From d5e5df7485a6b0b405b7a010e3e64e39f405762d Mon Sep 17 00:00:00 2001
From: wp_xxyyzz <wp_xxyyzz@8e941d3f-bd1b-0410-a28a-d453659cc2b4>
Date: Tue, 22 May 2018 22:21:15 +0000
Subject: [PATCH] fpspreadsheet: Rearrange units to better avoid circular unit
 references. General idea: no unit of the package must "use" fpspreadsheet.pas
 in the interface section.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@6444 8e941d3f-bd1b-0410-a28a-d453659cc2b4
---
 .../fpspreadsheet/source/common/fpscell.pas   |  89 +-
 .../source/common/fpsclasses.pas              |   7 +-
 .../fpspreadsheet/source/common/fpscsv.pas    |  56 +-
 .../source/common/fpsexprparser.pas           | 123 +--
 .../fpspreadsheet/source/common/fpsfunc.pas   |  24 +-
 .../fpspreadsheet/source/common/fpshtml.pas   | 153 ++--
 .../source/common/fpshtmlutils.pas            |  16 +-
 .../source/common/fpsopendocument.pas         | 645 +++++++-------
 .../source/common/fpspalette.pas              |  28 +-
 .../source/common/fpspreadsheet.pas           | 219 +----
 .../source/common/fpsreaderwriter.pas         | 131 +--
 .../fpspreadsheet/source/common/fpstypes.pas  | 248 +++++-
 .../fpspreadsheet/source/common/fpsutils.pas  |  58 +-
 .../source/common/fpsxmlcommon.pas            |   8 +-
 .../fpspreadsheet/source/common/wikitable.pas |  66 +-
 .../fpspreadsheet/source/common/xlsbiff2.pas  | 250 +++---
 .../fpspreadsheet/source/common/xlsbiff5.pas  | 151 ++--
 .../fpspreadsheet/source/common/xlsbiff8.pas  | 249 +++---
 .../fpspreadsheet/source/common/xlscommon.pas | 605 +++++++------
 .../fpspreadsheet/source/common/xlsxml.pas    | 164 ++--
 .../fpspreadsheet/source/common/xlsxooxml.pas | 817 ++++++++++--------
 21 files changed, 2276 insertions(+), 1831 deletions(-)

diff --git a/components/fpspreadsheet/source/common/fpscell.pas b/components/fpspreadsheet/source/common/fpscell.pas
index 9f35da083..c8cf04470 100644
--- a/components/fpspreadsheet/source/common/fpscell.pas
+++ b/components/fpspreadsheet/source/common/fpscell.pas
@@ -6,7 +6,7 @@ unit fpsCell;
 interface
 
 uses
-  Classes, SysUtils, fpstypes, fpspreadsheet;
+  Classes, SysUtils, fpstypes;
 
 type
   TCellHelper = record helper for TCell
@@ -46,8 +46,7 @@ type
     procedure SetWordwrap(const AValue: Boolean);
 
   protected
-    function GetWorkbook: TsWorkbook; inline;
-    function GetWorksheet: TsWorksheet; inline;
+    function GetWorkbook: TsBasicWorkbook; inline;
 
   public
     property BackgroundColor: TsColor
@@ -83,74 +82,77 @@ type
       read GetVertAlignment write SetVertAlignment;
     property Wordwrap: Boolean
       read GetWordwrap write SetWordwrap;
-    property Workbook: TsWorkbook read GetWorkbook;
+    property Workbook: TsBasicWorkbook read GetWorkbook;
   end;
 
 implementation
 
+uses
+  fpspreadsheet;
+
 function TCellHelper.GetBackgroundColor: TsColor;
 begin
-  Result := GetWorksheet.ReadBackgroundColor(@self);
+  Result := (Worksheet as TsWorksheet).ReadBackgroundColor(@self);
 end;
 
 function TCellHelper.GetBiDiMode: TsBiDiMode;
 begin
-  Result := GetWorksheet.ReadBiDiMode(@self);
+  Result := (Worksheet as TsWorksheet).ReadBiDiMode(@self);
 end;
 
 function TCellHelper.GetBorder: TsCellBorders;
 begin
-  Result := GetWorksheet.ReadCellBorders(@self);
+  Result := (Worksheet as TsWorksheet).ReadCellBorders(@self);
 end;
 
 function TCellHelper.GetBorderStyle(const ABorder: TsCellBorder): TsCellBorderStyle;
 begin
-  Result := GetWorksheet.ReadCellBorderStyle(@self, ABorder);
+  Result := (Worksheet as TsWorksheet).ReadCellBorderStyle(@self, ABorder);
 end;
 
 function TCellHelper.GetBorderStyles: TsCellBorderStyles;
 begin
-  Result := GetWorksheet.ReadCellBorderStyles(@self);
+  Result := (Worksheet as TsWorksheet).ReadCellBorderStyles(@self);
 end;
 
 function TCellHelper.GetCellFormat: TsCellFormat;
 begin
-  Result := GetWorkbook.GetCellFormat(FormatIndex);
+  Result := (GetWorkbook as TsWorkbook).GetCellFormat(FormatIndex);
 end;
 
 function TCellHelper.GetComment: String;
 begin
-  Result := GetWorksheet.ReadComment(@self);
+  Result := (Worksheet as TsWorksheet).ReadComment(@self);
 end;
 
 function TCellHelper.GetFont: TsFont;
 begin
-  Result := GetWorksheet.ReadCellFont(@self);
+  Result := (Worksheet as TsWorksheet).ReadCellFont(@self);
 end;
 
 function TCellHelper.GetFontIndex: Integer;
 var
   fmt: PsCellFormat;
 begin
-  fmt := Workbook.GetPointerToCellFormat(FormatIndex);
+  fmt := (Workbook as TsWorkbook).GetPointerToCellFormat(FormatIndex);
   Result := fmt^.FontIndex;
 end;
 
 function TCellHelper.GetHorAlignment: TsHorAlignment;
 begin
-  Result := GetWorksheet.ReadHorAlignment(@Self);
+  Result := (Worksheet as TsWorksheet).ReadHorAlignment(@Self);
 end;
 
 function TCellHelper.GetHyperlink: TsHyperlink;
 begin
-  Result := GetWorksheet.ReadHyperlink(@self);
+  Result := (Worksheet as TsWorksheet).ReadHyperlink(@self);
 end;
 
 function TCellHelper.GetNumberFormat: TsNumberFormat;
 var
   fmt: PsCellFormat;
 begin
-  fmt := Workbook.GetPointerToCellFormat(FormatIndex);
+  fmt := (Workbook as TsWorkbook).GetPointerToCellFormat(FormatIndex);
   Result := fmt^.NumberFormat;
 end;
 
@@ -158,127 +160,122 @@ function TCellHelper.GetNumberFormatStr: String;
 var
   fmt: PsCellFormat;
 begin
-  fmt := Workbook.GetPointerToCellFormat(FormatIndex);
+  fmt := (Workbook as TsWorkbook).GetPointerToCellFormat(FormatIndex);
   Result := fmt^.NumberFormatStr;
 end;
 
 function TCellHelper.GetTextRotation: TsTextRotation;
 begin
-  Result := GetWorksheet.ReadTextRotation(@Self);
+  Result := (Worksheet as TsWorksheet).ReadTextRotation(@Self);
 end;
 
 function TCellHelper.GetUsedFormattingFields: TsUsedFormattingFields;
 begin
-  Result := GetWorksheet.ReadUsedFormatting(@Self);
+  Result := (Worksheet as TsWorksheet).ReadUsedFormatting(@Self);
 end;
 
 function TCellHelper.GetVertAlignment: TsVertAlignment;
 begin
-  Result := GetWorksheet.ReadVertAlignment(@self);
+  Result := (Worksheet as TsWorksheet).ReadVertAlignment(@self);
 end;
 
 function TCellHelper.GetWordwrap: Boolean;
 begin
-  Result := GetWorksheet.ReadWordwrap(@self);
+  Result := (Worksheet as TsWorksheet).ReadWordwrap(@self);
 end;
 
-function TCellHelper.GetWorkbook: TsWorkbook;
+function TCellHelper.GetWorkbook: TsBasicWorkbook;
 begin
-  Result := GetWorksheet.Workbook;
-end;
-
-function TCellHelper.GetWorksheet: TsWorksheet;
-begin
-  Result := TsWorksheet(Worksheet);
+  Result := (Worksheet as TsWorksheet).Workbook;
 end;
 
 procedure TCellHelper.SetBackgroundColor(const AValue: TsColor);
 begin
-  GetWorksheet.WriteBackgroundColor(@self, AValue);
+  (Worksheet as TsWorksheet).WriteBackgroundColor(@self, AValue);
 end;
 
 procedure TCellHelper.SetBiDiMode(const AValue: TsBiDiMode);
 begin
-  GetWorksheet.WriteBiDiMode(@self, AValue);
+  (Worksheet as TsWorksheet).WriteBiDiMode(@self, AValue);
 end;
 
 procedure TCellHelper.SetBorder(const AValue: TsCellBorders);
 begin
-  GetWorksheet.WriteBorders(@self, AValue);
+  (Worksheet as TsWorksheet).WriteBorders(@self, AValue);
 end;
 
 procedure TCellHelper.SetBorderStyle(const ABorder: TsCellBorder;
   const AValue: TsCellBorderStyle);
 begin
-  GetWorksheet.WriteBorderStyle(@self, ABorder, AValue);
+  (Worksheet as TsWorksheet).WriteBorderStyle(@self, ABorder, AValue);
 end;
 
 procedure TCellHelper.SetBorderStyles(const AValue: TsCellBorderStyles);
 begin
-  GetWorksheet.WriteBorderStyles(@self, AValue);
+  (Worksheet as TsWorksheet).WriteBorderStyles(@self, AValue);
 end;
 
 procedure TCellHelper.SetCellFormat(const AValue: TsCellFormat);
 begin
-  GetWorksheet.WriteCellFormat(@self, AValue);
+  (Worksheet as TsWorksheet).WriteCellFormat(@self, AValue);
 end;
 
 procedure TCellHelper.SetComment(const AValue: String);
 begin
-  GetWorksheet.WriteComment(@self, AValue);
+  (Worksheet as TsWorksheet).WriteComment(@self, AValue);
 end;
 
 procedure TCellHelper.SetFontIndex(const AValue: Integer);
 begin
-  GetWorksheet.WriteFont(@self, AValue);
+  (Worksheet as TsWorksheet).WriteFont(@self, AValue);
 end;
 
 procedure TCellHelper.SetHorAlignment(const AValue: TsHorAlignment);
 begin
-  GetWorksheet.WriteHorAlignment(@self, AValue);
+  (Worksheet as TsWorksheet).WriteHorAlignment(@self, AValue);
 end;
 
 procedure TCellHelper.SetHyperlink(const AValue: TsHyperlink);
 begin
-  GetWorksheet.WriteHyperlink(@self, AValue.Target, AValue.Tooltip);
+  (Worksheet as TsWorksheet).WriteHyperlink(@self, AValue.Target, AValue.Tooltip);
 end;
 
 procedure TCellHelper.SetNumberFormat(const AValue: TsNumberFormat);
 var
   fmt: TsCellFormat;
 begin
-  fmt := Workbook.GetCellFormat(FormatIndex);
+  fmt := (Workbook as TsWorkbook).GetCellFormat(FormatIndex);
   fmt.NumberFormat := AValue;
-  GetWorksheet.WriteCellFormat(@self, fmt);
+  (Worksheet as TsWorksheet).WriteCellFormat(@self, fmt);
 end;
 
 procedure TCellHelper.SetNumberFormatStr(const AValue: String);
 var
   fmt: TsCellFormat;
 begin
-  fmt := Workbook.GetCellFormat(FormatIndex);
+  fmt := (Workbook as TsWorkbook).GetCellFormat(FormatIndex);
   fmt.NumberFormatStr := AValue;
-  GetWorksheet.WriteCellFormat(@self, fmt);
+  (Worksheet as TsWorksheet).WriteCellFormat(@self, fmt);
 end;
 
 procedure TCellHelper.SetTextRotation(const AValue: TsTextRotation);
 begin
-  GetWorksheet.WriteTextRotation(@self, AValue);
+  (Worksheet as TsWorksheet).WriteTextRotation(@self, AValue);
 end;
 
 procedure TCellHelper.SetUsedFormattingFields(const AValue: TsUsedFormattingFields);
 begin
-  GetWorksheet.WriteUsedFormatting(@self, AValue);
+  (Worksheet as TsWorksheet).WriteUsedFormatting(@self, AValue);
 end;
 
 procedure TCellHelper.SetVertAlignment(const AValue: TsVertAlignment);
 begin
-  GetWorksheet.WriteVertAlignment(@self, AValue);
+  (Worksheet as TsWorksheet).WriteVertAlignment(@self, AValue);
 end;
 
 procedure TCellHelper.SetWordwrap(const AValue: Boolean);
 begin
-  GetWorksheet.WriteWordwrap(@self, AValue);
+  (Worksheet as TsWorksheet).WriteWordwrap(@self, AValue);
 end;
 
 
diff --git a/components/fpspreadsheet/source/common/fpsclasses.pas b/components/fpspreadsheet/source/common/fpsclasses.pas
index 290e67520..c0987d60e 100644
--- a/components/fpspreadsheet/source/common/fpsclasses.pas
+++ b/components/fpspreadsheet/source/common/fpsclasses.pas
@@ -76,12 +76,12 @@ type
 
   TsCells = class(TsRowColAVLTree)
   private
-    FWorksheet: Pointer;  // Must be cast to TsWorksheet
+    FWorksheet: TsBasicWorksheet;  // Must be cast to TsWorksheet
   protected
     procedure DisposeData(var AData: Pointer); override;
     function NewData: Pointer; override;
   public
-    constructor Create(AWorksheet: Pointer; AOwnsData: Boolean = true);
+    constructor Create(AWorksheet: TsBasicWorksheet; AOwnsData: Boolean = true);
     function AddCell(ARow, ACol: Cardinal): PCell;
     procedure DeleteCell(ARow, ACol: Cardinal);
     function FindCell(ARow, ACol: Cardinal): PCell;
@@ -689,7 +689,8 @@ end;
 { TsCells: an AVLTree to store spreadsheet cells                               }
 {==============================================================================}
 
-constructor TsCells.Create(AWorksheet: Pointer; AOwnsData: Boolean = true);
+constructor TsCells.Create(AWorksheet: TsBasicWorksheet;
+  AOwnsData: Boolean = true);
 begin
   inherited Create(AOwnsData);
   FWorksheet := AWorksheet;
diff --git a/components/fpspreadsheet/source/common/fpscsv.pas b/components/fpspreadsheet/source/common/fpscsv.pas
index 14ad03ea3..59cc786bc 100644
--- a/components/fpspreadsheet/source/common/fpscsv.pas
+++ b/components/fpspreadsheet/source/common/fpscsv.pas
@@ -6,7 +6,7 @@ interface
 
 uses
   Classes, SysUtils,
-  fpstypes, fpspreadsheet, fpsReaderWriter, fpsCsvDocument;
+  fpstypes, fpsReaderWriter, fpsCsvDocument;
 
 type
   TsCSVReader = class(TsCustomSpreadReader)
@@ -21,7 +21,7 @@ type
     procedure ReadLabel(AStream: TStream); override;
     procedure ReadNumber(AStream: TStream); override;
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     procedure ReadFromFile(AFileName: String; APassword: String = '';
       AParams: TsStreamParams = []); override;
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
@@ -48,10 +48,10 @@ type
       const AValue: string; ACell: PCell); override;
     procedure WriteNumber(AStream: TStream; const ARow, ACol: Cardinal;
       const AValue: double; ACell: PCell); override;
-    procedure WriteSheet(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteSheet(AStream: TStream; AWorksheet: TsBasicWorksheet);
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     procedure WriteToStream(AStream: TStream; AParams: TsStreamParams = []); override;
     procedure WriteToStrings(AStrings: TStrings; AParams: TsStreamParams = []); override;
   end;
@@ -95,7 +95,7 @@ implementation
 
 uses
   DateUtils, LConvEncoding, Math,
-  fpsUtils, fpsNumFormat;
+  fpsUtils, fpspreadsheet, fpsNumFormat;
 
 const
   DEFAULT_ENCODING = 'utf8'; //'utf8bom';
@@ -115,7 +115,7 @@ end;
 {                              TsCSVReader                                     }
 {------------------------------------------------------------------------------}
 
-constructor TsCSVReader.Create(AWorkbook: TsWorkbook);
+constructor TsCSVReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   FWorksheetName := 'Sheet1';  // will be replaced by filename
@@ -148,29 +148,32 @@ procedure TsCSVReader.ReadCellValue(ARow, ACol: Cardinal; AText: String);
 var
   cell: PCell;
   boolValue: Boolean;
+  sheet: TsWorksheet;
 begin
   // Empty strings are blank cells -- nothing to do
   if AText = '' then
     exit;
 
-  cell := FWorksheet.AddCell(ARow, ACol);
+  sheet := FWorksheet as TsWorksheet;
+
+  cell := sheet.AddCell(ARow, ACol);
 
   // Do not try to interpret the strings. --> everything is a LABEL cell.
   if not CSVParams.DetectContentType then
   begin
-    FWorksheet.WriteText(cell, AText);
+    sheet.WriteText(cell, AText);
     exit;
   end;
 
   // Check for a BOOLEAN cell
   if IsBoolValue(AText, CSVParams.TrueText, CSVParams.FalseText, boolValue) then
   begin
-    FWorksheet.WriteBoolValue(cell, boolValue);
+    sheet.WriteBoolValue(cell, boolValue);
     exit;
   end;
 
   // All other cases are handled by WriteCellValusAsString
-  FWorksheet.WriteCellValueAsString(cell, AText, FFormatSettings);
+  sheet.WriteCellValueAsString(cell, AText, FFormatSettings);
 end;
 
 procedure TsCSVReader.ReadFormula(AStream: TStream);
@@ -205,7 +208,7 @@ begin
     encoding := DEFAULT_ENCODING;
 
   // Create worksheet
-  FWorksheet := FWorkbook.AddWorksheet(FWorksheetName, true);
+  FWorksheet := (FWorkbook as TsWorkbook).AddWorksheet(FWorksheetName, true);
 
   // Create csv parser, read file and store in worksheet
   Parser := TCSVParser.Create;
@@ -255,7 +258,7 @@ end;
 {                              TsCSVWriter                                     }
 {------------------------------------------------------------------------------}
 
-constructor TsCSVWriter.Create(AWorkbook: TsWorkbook);
+constructor TsCSVWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   FFormatSettings := CSVParams.FormatSettings;
@@ -298,7 +301,7 @@ var
 begin
   Unused(AStream);
   Unused(ARow, ACol, AValue);
-  s := FWorksheet.ReadAsText(ACell);
+  s := (FWorksheet as TsWorksheet).ReadAsText(ACell);
   s := ConvertEncoding(s, EncodingUTF8, FEncoding);
   FCSVBuilder.AppendCell(s);
 end;
@@ -349,20 +352,22 @@ begin
   if CSVParams.NumberFormat <> '' then
     s := Format(CSVParams.NumberFormat, [AValue], FFormatSettings)
   else
-    s := FWorksheet.ReadAsText(ACell, FFormatSettings);
+    s := (FWorksheet as TsWorksheet).ReadAsText(ACell, FFormatSettings);
   s := ConvertEncoding(s, EncodingUTF8, FEncoding);
   FCSVBuilder.AppendCell(s);
 end;
 
-procedure TsCSVWriter.WriteSheet(AStream: TStream; AWorksheet: TsWorksheet);
+procedure TsCSVWriter.WriteSheet(AStream: TStream; AWorksheet: TsBasicWorksheet);
 var
   r, c: Cardinal;
   firstRow, lastRow: Cardinal;
   firstCol, lastCol: Cardinal;
   cell: PCell;
   n: Integer;
+  sheet: TsWorksheet;
 begin
   FWorksheet := AWorksheet;
+  sheet := FWorksheet as TsWorksheet;
 
   FCSVBuilder := TCSVBuilder.Create;
   try
@@ -371,29 +376,29 @@ begin
     FCSVBuilder.QuoteChar := CSVParams.QuoteChar;
     FCSVBuilder.SetOutput(AStream);
 
-    n := FWorksheet.GetCellCount;
+    n := sheet.GetCellCount;
     if FClipboardMode and (n = 1) then
     begin
-      cell := FWorksheet.Cells.GetFirstCell;
+      cell := sheet.Cells.GetFirstCell;
       WriteCellToStream(AStream, cell);
     end else
     begin
       if FClipboardMode then
       begin
-        firstRow := FWorksheet.GetFirstRowIndex;
-        firstCol := FWorksheet.GetFirstColIndex;
+        firstRow := sheet.GetFirstRowIndex;
+        firstCol := sheet.GetFirstColIndex;
       end else
       begin
         firstRow := 0;
         firstCol := 0;
       end;
-      lastRow := FWorksheet.GetLastOccupiedRowIndex;
-      lastCol := FWorksheet.GetLastOccupiedColIndex;
+      lastRow := sheet.GetLastOccupiedRowIndex;
+      lastCol := sheet.GetLastOccupiedColIndex;
       for r := firstRow to lastRow do
       begin
         for c := firstCol to lastCol do
         begin
-          cell := FWorksheet.FindCell(r, c);
+          cell := sheet.FindCell(r, c);
           if cell = nil then
             FCSVBuilder.AppendCell('')
           else
@@ -411,12 +416,15 @@ procedure TsCSVWriter.WriteToStream(AStream: TStream;
   AParams: TsStreamParams = []);
 var
   n: Integer;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   FClipboardMode := (spClipboard in AParams);
-  if (CSVParams.SheetIndex >= 0) and (CSVParams.SheetIndex < FWorkbook.GetWorksheetCount)
+  if (CSVParams.SheetIndex >= 0) and (CSVParams.SheetIndex < book.GetWorksheetCount)
     then n := CSVParams.SheetIndex
     else n := 0;
-  WriteSheet(AStream, FWorkbook.GetWorksheetByIndex(n));
+  WriteSheet(AStream, book.GetWorksheetByIndex(n));
 end;
 
 procedure TsCSVWriter.WriteToStrings(AStrings: TStrings;
diff --git a/components/fpspreadsheet/source/common/fpsexprparser.pas b/components/fpspreadsheet/source/common/fpsexprparser.pas
index 48d374967..498afbc91 100644
--- a/components/fpspreadsheet/source/common/fpsexprparser.pas
+++ b/components/fpspreadsheet/source/common/fpsexprparser.pas
@@ -51,7 +51,7 @@ unit fpsExprParser;
 interface
 
 uses
-  Classes, SysUtils, contnrs, fpstypes, fpspreadsheet, fpsrpn;
+  Classes, SysUtils, contnrs, fpstypes, fpsrpn;
 
 type
   { Tokens }
@@ -86,7 +86,7 @@ type
   TsResultTypes = set of TsResultType;
 
   TsExpressionResult = record
-    Worksheet       : TsWorksheet;   // Worksheet containing the calculated cell
+    Worksheet       : TsBasicWorksheet;  // Worksheet containing the calculated cell
     ResString       : String;
     case ResultType : TsResultType of
       rtEmpty       : ();
@@ -586,7 +586,7 @@ type
   { TsCellExprNode }
   TsCellExprNode = class(TsExprNode)
   private
-    FWorksheet: TsWorksheet;
+    FWorksheet: TsBasicWorksheet;
     FRow, FCol: Cardinal;
     FFlags: TsRelFlags;
     FCell: PCell;
@@ -595,20 +595,20 @@ type
   protected
     function GetCol: Cardinal;
     function GetRow: Cardinal;
-    function GetSheet: TsWorksheet;
+    function GetSheet: TsBasicWorksheet;
     function GetSheetIndex: Integer;
     function GetSheetName: String;
-    function GetWorkbook: TsWorkbook;
+    function GetWorkbook: TsBasicWorkbook;
     procedure GetNodeValue(out AResult: TsExpressionResult); override;
   public
-    constructor Create(AParser: TsExpressionParser; AWorksheet: TsWorksheet;
+    constructor Create(AParser: TsExpressionParser; AWorksheet: TsBasicWorksheet;
       ASheetName: String; ARow, ACol: Cardinal; AFlags: TsRelFlags);
     function AsRPNItem(ANext: PRPNItem): PRPNItem; override;
     function AsString: string; override;
     procedure Check; override;
     function Has3DLink: Boolean; override;
     function NodeType: TsResultType; override;
-    property Worksheet: TsWorksheet read FWorksheet;
+    property Worksheet: TsBasicWorksheet read FWorksheet;
   end;
 
   { TsCellRangeExprNode }
@@ -616,7 +616,7 @@ type
 
   TsCellRangeExprNode = class(TsExprNode)
   private
-    FWorksheet: TsWorksheet;
+    FWorksheet: TsBasicWorksheet;
     FRow: array[TsCellRangeIndex] of Cardinal;
     FCol: array[TsCellRangeIndex] of Cardinal;
     FSheetIndex: array[TsCellRangeIndex] of Integer;
@@ -626,17 +626,17 @@ type
     function GetCol(AIndex: TsCellRangeIndex): Cardinal;
     function GetRow(AIndex: TsCellRangeIndex): Cardinal;
     procedure GetNodeValue(out Result: TsExpressionResult); override;
-    function GetWorkbook: TsWorkbook;
+    function GetWorkbook: TsBasicWorkbook;
   public
-    constructor Create(AParser: TsExpressionParser; AWorksheet: TsWorksheet;
+    constructor Create(AParser: TsExpressionParser; AWorksheet: TsBasicWorksheet;
       ASheet1, ASheet2: String; ARange: TsCellRange; AFlags: TsRelFlags);
     function AsRPNItem(ANext: PRPNItem): PRPNItem; override;
     function AsString: String; override;
     procedure Check; override;
     function Has3DLink: Boolean; override;
     function NodeType: TsResultType; override;
-    property Workbook: TsWorkbook read GetWorkbook;
-    property Worksheet: TsWorksheet read FWorksheet;
+    property Workbook: TsBasicWorkbook read GetWorkbook;
+    property Worksheet: TsBasicWorksheet read FWorksheet;
   end;
 
   { TsExpressionScanner }
@@ -700,7 +700,7 @@ type
     FIdentifiers: TsExprIdentifierDefs;
     FHashList: TFPHashObjectlist;
     FDirty: Boolean;
-    FWorksheet: TsWorksheet;
+    FWorksheet: TsBasicWorksheet;
     FDialect: TsFormulaDialect;
     FSourceCell: PCell;
     FDestCell: PCell;
@@ -748,7 +748,7 @@ type
     property Dirty: Boolean read FDirty;
 
   public
-    constructor Create(AWorksheet: TsWorksheet); virtual;
+    constructor Create(AWorksheet: TsBasicWorksheet); virtual;
     destructor Destroy; override;
     function IdentifierByName(AName: ShortString): TsExprIdentifierDef; virtual;
     procedure Clear;
@@ -771,7 +771,7 @@ type
     property RPNFormula: TsRPNFormula read GetRPNFormula write SetRPNFormula;
     property Identifiers: TsExprIdentifierDefs read FIdentifiers write SetIdentifiers;
     property BuiltIns: TsBuiltInExprCategories read FBuiltIns write SetBuiltIns;
-    property Worksheet: TsWorksheet read FWorksheet;
+    property Worksheet: TsBasicWorksheet read FWorksheet;
     property Dialect: TsFormulaDialect read FDialect write SetDialect;
     property Contains3DRef: boolean read FContains3DRef;
 
@@ -779,7 +779,7 @@ type
 
   TsSpreadsheetParser = class(TsExpressionParser)
   public
-    constructor Create(AWorksheet: TsWorksheet); override;
+    constructor Create(AWorksheet: TsBasicWorksheet); override;
   end;
 
 
@@ -865,7 +865,8 @@ const
 implementation
 
 uses
-  typinfo, math, lazutf8, dateutils, fpsutils, fpsfunc, fpsStrings;
+  typinfo, math, lazutf8, dateutils,
+  fpsutils, fpsfunc, fpsStrings, fpspreadsheet;
 
 const
   cNull = #0;
@@ -1372,7 +1373,7 @@ end;
 {  TsExpressionParser                                                         }
 {------------------------------------------------------------------------------}
 
-constructor TsExpressionParser.Create(AWorksheet: TsWorksheet);
+constructor TsExpressionParser.Create(AWorksheet: TsBasicWorksheet);
 begin
   inherited Create;
   FDialect := fdExcelA1;
@@ -2038,7 +2039,7 @@ procedure TsExpressionParser.SetRPNFormula(const AFormula: TsRPNFormula);
           else
           begin
             flags := AFormula[AIndex].RelFlags;
-            sn := FWorksheet.Workbook.GetWorksheetByIndex(idx).Name;
+            sn := (FWorksheet as TsWorksheet).Workbook.GetWorksheetByIndex(idx).Name;
             ANode := TsCellExprNode.Create(Self, FWorksheet, sn, r, c, flags);
           end;
           dec(AIndex);
@@ -2053,9 +2054,9 @@ procedure TsExpressionParser.SetRPNFormula(const AFormula: TsRPNFormula);
           if fek = fekCellRange then
             ANode := TsCellRangeExprNode.Create(self, FWorksheet, '', '', rng, flags)
           else begin
-            sn := FWorksheet.Workbook.GetWorksheetByIndex(AFormula[AIndex].Sheet).Name;
+            sn := (FWorksheet as TsWorksheet).Workbook.GetWorksheetByIndex(AFormula[AIndex].Sheet).Name;
             if AFormula[AIndex].Sheet2 <> -1 then
-              sn2 := FWorksheet.Workbook.GetWorksheetByIndex(AFormula[AIndex].Sheet2).Name
+              sn2 := (FWorksheet as TsWorksheet).Workbook.GetWorksheetByIndex(AFormula[AIndex].Sheet2).Name
             else
               sn2 := '';
             ANode := TsCellRangeExprNode.Create(self, FWorksheet, sn,sn2, rng, flags);
@@ -2185,7 +2186,7 @@ end;
 {  TsSpreadsheetParser                                                         }
 {------------------------------------------------------------------------------}
 
-constructor TsSpreadsheetParser.Create(AWorksheet: TsWorksheet);
+constructor TsSpreadsheetParser.Create(AWorksheet: TsBasicWorksheet);
 begin
   inherited Create(AWorksheet);
   BuiltIns := AllBuiltIns;
@@ -3763,7 +3764,7 @@ end;
 { TsCellExprNode }
 
 constructor TsCellExprNode.Create(AParser: TsExpressionParser;
-  AWorksheet: TsWorksheet; ASheetName: String; ARow, ACol: Cardinal;
+  AWorksheet: TsBasicWorksheet; ASheetName: String; ARow, ACol: Cardinal;
   AFlags: TsRelFlags);
 begin
   FParser := AParser;
@@ -3772,7 +3773,7 @@ begin
   FRow := ARow;
   FCol := ACol;
   FFlags := AFlags;
-  FCell := GetSheet.FindCell(FRow, FCol);
+  FCell := (GetSheet as TsWorksheet).FindCell(FRow, FCol);
   if Has3DLink then FParser.FContains3DRef := true;
 end;
 
@@ -3847,14 +3848,14 @@ var
   cell: PCell;
 begin
   if Parser.CopyMode then
-    cell := FWorksheet.FindCell(GetRow, GetCol)
+    cell := (FWorksheet as TsWorksheet).FindCell(GetRow, GetCol)
   else
     cell := FCell;
 
   if (cell <> nil) and HasFormula(cell) then
-    case FWorksheet.GetCalcState(cell) of
+    case (FWorksheet as TsWorksheet).GetCalcState(cell) of
       csNotCalculated:
-        FWorksheet.CalcFormula(cell);
+        (FWorksheet as TsWorksheet).CalcFormula(cell);
       csCalculating:
         raise ECalcEngine.CreateFmt(rsCircularReference, [GetCellString(cell^.Row, cell^.Col)]);
     end;
@@ -3873,20 +3874,23 @@ begin
     Result := FRow - FParser.FSourceCell^.Row + FParser.FDestCell^.Row;
 end;
 
-function TsCellExprNode.GetSheet: TsWorksheet;
+function TsCellExprNode.GetSheet: TsBasicWorksheet;
 begin
   if FSheetName = '' then
     Result := FWorksheet
   else
-    Result := GetWorkbook.GetWorksheetByName(FSheetName);
+    Result := (GetWorkbook as TsWorkbook).GetWorksheetByName(FSheetName);
 end;
 
 function TsCellExprNode.GetSheetIndex: Integer;
+var
+  book: TsWorkbook;
 begin
+  book := GetWorkbook as TsWorkbook;
   if FSheetName = '' then
-    Result := GetWorkbook.GetWorksheetIndex(FWorksheet)
+    Result := book.GetWorksheetIndex(FWorksheet)
   else
-    Result := GetWorkbook.GetWorksheetIndex(FSheetName);
+    Result := book.GetWorksheetIndex(FSheetName);
 end;
 
 function TsCellExprNode.GetSheetName: String;
@@ -3897,9 +3901,9 @@ begin
     Result := FSheetName;
 end;
 
-function TsCellExprNode.GetWorkbook: TsWorkbook;
+function TsCellExprNode.GetWorkbook: TsBasicWorkbook;
 begin
-  Result := FWorksheet.Workbook;
+  Result := (FWorksheet as TsWorksheet).Workbook;
 end;
 
 function TsCellExprNode.Has3DLink: Boolean;
@@ -3917,8 +3921,10 @@ end;
 { TsCellRangeExprNode }
 
 constructor TsCellRangeExprNode.Create(AParser: TsExpressionParser;
-  AWorksheet: TsWorksheet; ASheet1, ASheet2: String; ARange: TsCellRange;
+  AWorksheet: TsBasicWorksheet; ASheet1, ASheet2: String; ARange: TsCellRange;
   AFlags: TsRelFlags);
+var
+  book: TsWorkbook;
 begin
   if (ASheet1 = '') and (ASheet2 <> '') then
     raise Exception.Create('Invalid parameters in cell range');
@@ -3926,13 +3932,14 @@ begin
   FParser := AParser;
   FWorksheet := AWorksheet;
   FFlags := [];
+  book := TsWorkbook(GetWorkbook);
 
   F3dRange := ((ASheet1 <> '') and (ASheet2 <> '') { and (ASheet1 <> ASheet2)}) or
     ((ASheet1 <> '') and (ASheet2 = ''));
 
-  FSheetIndex[1] := GetWorkbook.GetWorksheetIndex(ASheet1);
+  FSheetIndex[1] := book.GetWorksheetIndex(ASheet1);
   if ASheet2 <> '' then
-    FSheetIndex[2] := GetWorkbook.GetWorksheetIndex(ASheet2)
+    FSheetIndex[2] := book.GetWorksheetIndex(ASheet2)
   else
     FSheetIndex[2] := FSheetIndex[1];
   EnsureOrder(FSheetIndex[1], FSheetIndex[2]);
@@ -3997,11 +4004,11 @@ begin
   if FSheetIndex[1] = -1 then
     s1 := FWorksheet.Name
   else
-    s1 := Workbook.GetWorksheetByIndex(FSheetIndex[1]).Name;
+    s1 := (Workbook as TsWorkbook).GetWorksheetByIndex(FSheetIndex[1]).Name;
   if FSheetIndex[2] = -1 then
     s2 := FWorksheet.Name
   else
-    s2 := Workbook.GetWorksheetByIndex(FSheetIndex[2]).Name;
+    s2 := (Workbook as TsWorkbook).GetWorksheetByIndex(FSheetIndex[2]).Name;
   r1 := GetRow(1);
   c1 := GetCol(1);
   r2 := GetRow(2);
@@ -4068,12 +4075,12 @@ begin
   end;
 
   if not F3dRange then begin
-    s[1] := Workbook.GetWorksheetIndex(FWorksheet);
+    s[1] := (Workbook as TsWorkbook).GetWorksheetIndex(FWorksheet);
     s[2] := s[1];
   end;
 
   for ss := s[1] to s[2] do begin
-    sheet := Workbook.GetWorksheetByIndex(ss);
+    sheet := (Workbook as TsWorkbook).GetWorksheetByIndex(ss);
     for rr := r[1] to r[2] do
       for cc := c[1] to c[2] do
       begin
@@ -4106,9 +4113,9 @@ begin
     Result := FRow[AIndex] - FParser.FSourceCell^.Row + FParser.FDestCell^.Row;
 end;
 
-function TsCellRangeExprNode.GetWorkbook: TsWorkbook;
+function TsCellRangeExprNode.GetWorkbook: TsBasicWorkbook;
 begin
-  Result := FWorksheet.Workbook;
+  Result := (FWorksheet as TsWorksheet).Workbook;
 end;
 
 function TsCellRangeExprNode.Has3DLink: Boolean;
@@ -4144,7 +4151,7 @@ end;
 function ArgToCell(Arg: TsExpressionResult): PCell;
 begin
   if Arg.ResultType = rtCell then
-    Result := Arg.Worksheet.FindCell(Arg.ResRow, Arg.ResCol)
+    Result := (Arg.Worksheet as TsWorksheet).FindCell(Arg.ResRow, Arg.ResCol)
   else
     Result := nil;
 end;
@@ -4196,14 +4203,18 @@ begin
                     cell := ArgToCell(Arg);
                     if Assigned(cell) then
                       case cell^.ContentType of
-                        cctNumber    : Result := cell^.NumberValue;
-                        cctDateTime  : Result := cell^.DateTimeValue;
-                        cctBool      : if cell^.BoolValue then result := 1.0;
-                        cctUTF8String: begin
-                                         fs := Arg.Worksheet.Workbook.FormatSettings;
-                                         s := cell^.UTF8StringValue;
-                                         TryStrToFloat(s, result, fs);
-                                       end;
+                        cctNumber:
+                          Result := cell^.NumberValue;
+                        cctDateTime:
+                          Result := cell^.DateTimeValue;
+                        cctBool:
+                          if cell^.BoolValue then result := 1.0;
+                        cctUTF8String:
+                          begin
+                            fs := (Arg.Worksheet as TsWorksheet).Workbook.FormatSettings;
+                            s := cell^.UTF8StringValue;
+                            TryStrToFloat(s, result, fs);
+                          end;
                        end;
                    end;
   end;
@@ -4222,7 +4233,7 @@ begin
     rtBoolean   : if Arg.ResBoolean then Result := 1.0;
     rtString,
     rtHyperlink : begin
-                    fs := Arg.Worksheet.Workbook.FormatSettings;
+                    fs := (Arg.Worksheet as TsWorksheet).Workbook.FormatSettings;
                     TryStrToDateTime(ArgToString(Arg), Result, fs);
                   end;
     rtCell      : begin
@@ -4265,7 +4276,7 @@ begin
                         cctNumber     : Result := Format('%g', [cell^.NumberValue]);
                         cctBool       : if cell^.BoolValue then Result := '1' else Result := '0';
                         cctDateTime   : begin
-                                          fs := Arg.Worksheet.Workbook.FormatSettings;
+                                          fs := (Arg.Worksheet as TsWorksheet).Workbook.FormatSettings;
                                           dt := cell^.DateTimeValue;
                                           if frac(dt) = 0.0 then
                                             Result := FormatDateTime(fs.LongTimeFormat, dt, fs)
@@ -4301,7 +4312,7 @@ begin
       idx2 := arg.ResCellRange.Sheet2;
       for idx := idx1 to idx2 do
       begin
-        sheet := arg.Worksheet.Workbook.GetWorksheetByIndex(idx);
+        sheet := (arg.Worksheet as TsWorksheet).Workbook.GetWorksheetByIndex(idx);
         for r := arg.ResCellRange.Row1 to arg.ResCellRange.Row2 do
           for c := arg.ResCellRange.Col1 to arg.ResCellRange.Col2 do
           begin
@@ -4393,7 +4404,7 @@ begin
     rtFloat  : Result := (frac(AValue.ResFloat) = 0);
     rtEmpty  : Result := true;
     rtCell   : begin
-                 cell := AValue.Worksheet.FindCell(AValue.ResRow, AValue.ResCol);
+                 cell := (AValue.Worksheet as TsWorksheet).FindCell(AValue.ResRow, AValue.ResCol);
                  if Assigned(cell) then
                    case cell^.ContentType of
                      cctNumber:
@@ -4415,7 +4426,7 @@ begin
   case AValue.ResultType of
     rtString: Result := true;
     rtCell  : begin
-                cell := AValue.Worksheet.FindCell(AValue.ResRow, AValue.ResCol);
+                cell := (AValue.Worksheet as TsWorksheet).FindCell(AValue.ResRow, AValue.ResCol);
                 Result := (cell <> nil) and (cell^.ContentType = cctUTF8String);
               end;
   end;
diff --git a/components/fpspreadsheet/source/common/fpsfunc.pas b/components/fpspreadsheet/source/common/fpsfunc.pas
index 09c99b1a3..8ee39f986 100644
--- a/components/fpspreadsheet/source/common/fpsfunc.pas
+++ b/components/fpspreadsheet/source/common/fpsfunc.pas
@@ -9,7 +9,7 @@ unit fpsfunc;
 interface
 
 uses
-  Classes, SysUtils, fpstypes, fpspreadsheet;
+  Classes, SysUtils, fpstypes;
 
 procedure RegisterStdBuiltins(AManager: TComponent);
 
@@ -18,7 +18,7 @@ implementation
 
 uses
   Math, lazutf8, StrUtils, DateUtils,
-  xlsconst, {%H-}fpsPatches, fpsUtils, fpsnumformat, fpsexprparser;
+  xlsconst, {%H-}fpsPatches, fpsUtils, fpsnumformat, fpsexprparser, fpspreadsheet;
 
 
 {------------------------------------------------------------------------------}
@@ -1035,7 +1035,7 @@ begin
         for r := arg.ResCellRange.Row1 to arg.ResCellRange.Row2 do
           for c := arg.ResCellRange.Col1 to arg.ResCellRange.Col2 do
           begin
-            cell := arg.Worksheet.FindCell(r, c);
+            cell := (arg.Worksheet as TsWorksheet).FindCell(r, c);
             if (cell <> nil) then
               case cell^.ContentType of
                 cctNumber, cctDateTime, cctBool : inc(n);
@@ -1076,7 +1076,7 @@ begin
     rtCellRange:
       for r := Args[0].ResCellRange.Row1 to Args[0].ResCellRange.Row2 do
         for c := Args[0].ResCellRange.Col1 to Args[0].ResCellRange.Col2 do begin
-          cell := Args[0].Worksheet.FindCell(r, c);
+          cell := (Args[0].Worksheet as TsWorksheet).FindCell(r, c);
           if cell = nil then
             inc(n)
           else
@@ -1185,7 +1185,7 @@ begin
 
   // Get format settings for string-to-float or -to-datetime conversion
   if (Args[0].ResultType in [rtCell, rtCellRange]) then
-    fs := Args[0].Worksheet.FormatSettings
+    fs := (Args[0].Worksheet as TsWorksheet).FormatSettings
   else
   begin
     Result := ErrorResult(errArgError);
@@ -1325,8 +1325,8 @@ begin
         if AFlag > 0 then
         begin
           if Length(Args) = 2 then
-            addcell := Args[0].Worksheet.FindCell(r + dr, c + dc) else
-            addCell := Args[2].Worksheet.FindCell(r + dr, c + dc);
+            addcell := (Args[0].Worksheet as TsWorksheet).FindCell(r + dr, c + dc) else
+            addCell := (Args[2].Worksheet as TsWorksheet).FindCell(r + dr, c + dc);
           if addcell <> nil then
             case addcell^.Contenttype of
               cctNumber  : addnumber := addcell^.NumberValue;
@@ -1335,7 +1335,7 @@ begin
             end;
         end;
 
-        cell := Args[0].Worksheet.FindCell(r, c);
+        cell := (Args[0].Worksheet as TsWorksheet).FindCell(r, c);
         case compareType of
           ctNumber:
             if cell <> nil then
@@ -1610,7 +1610,7 @@ begin
       begin
         r1 := Args[1].ResCellRange.Row1;
         c1 := Args[1].ResCellRange.Col1;
-        cell := Args[1].Worksheet.FindCell(r1, c1);
+        cell := (Args[1].Worksheet as TsWorksheet).FindCell(r1, c1);
       end;
     else
       Result := ErrorResult(errWrongType);
@@ -1652,8 +1652,8 @@ begin
   end else
   if stype = 'filename' then
     Result := Stringresult(
-      ExtractFilePath(Args[1].Worksheet.Workbook.FileName) + '[' +
-      ExtractFileName(Args[1].Worksheet.Workbook.FileName) + ']' +
+      ExtractFilePath((Args[1].Worksheet as TsWorksheet).Workbook.FileName) + '[' +
+      ExtractFileName((Args[1].Worksheet as TsWorksheet).Workbook.FileName) + ']' +
       Args[1].Worksheet.Name
     )
   else
@@ -1710,7 +1710,7 @@ begin
       Result := StringResult('v');
   end else
   if stype = 'width' then
-    Result := FloatResult(Args[1].Worksheet.GetColWidth(c1, suChars))
+    Result := FloatResult((Args[1].Worksheet as TsWorksheet).GetColWidth(c1, suChars))
   else
     Result := ErrorResult(errWrongType);
 end;
diff --git a/components/fpspreadsheet/source/common/fpshtml.pas b/components/fpspreadsheet/source/common/fpshtml.pas
index e56e628ed..8122aead1 100644
--- a/components/fpspreadsheet/source/common/fpshtml.pas
+++ b/components/fpspreadsheet/source/common/fpshtml.pas
@@ -6,7 +6,7 @@ interface
 
 uses
   Classes, SysUtils, fasthtmlparser,
-  fpstypes, fpspreadsheet, fpsClasses, fpsReaderWriter, fpsHTMLUtils;
+  fpstypes, fpsClasses, fpsReaderWriter, fpsHTMLUtils;
 
 type
   TsHTMLReader = class(TsCustomSpreadReader)
@@ -55,7 +55,7 @@ type
     procedure AddRichTextParam(AFont: TsFont; AHyperlinkIndex: Integer = -1);
     procedure FixRichTextParams(var AParams: TsRichTextParams);
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
       AParams: TsStreamParams = []); override;
@@ -86,7 +86,7 @@ type
     function IsHyperlinkTarget(ACell: PCell; out ABookmark: String): Boolean;
     procedure WriteBody(AStream: TStream);
     procedure WriteStyles(AStream: TStream);
-    procedure WriteWorksheet(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteWorksheet(AStream: TStream; ASheet: TsBasicWorksheet);
 
   protected
     procedure InternalWriteToStream(AStream: TStream);
@@ -106,7 +106,7 @@ type
       const AValue: double; ACell: PCell); override;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
     procedure WriteToStream(AStream: TStream; AParams: TsStreamParams = []); override;
     procedure WriteToStrings(AStrings: TStrings; AParams: TsStreamParams = []); override;
@@ -143,7 +143,7 @@ implementation
 
 uses
   LConvEncoding, LazUTF8, URIParser, StrUtils, Math,
-  fpsUtils, fpsXMLCommon, fpsNumFormat;
+  fpsUtils, fpspreadsheet, fpsXMLCommon, fpsNumFormat;
 
 const
   MIN_FONTSIZE = 6;
@@ -162,7 +162,7 @@ const
 {                             TsHTMLReader                                     }
 {==============================================================================}
 
-constructor TsHTMLReader.Create(AWorkbook: TsWorkbook);
+constructor TsHTMLReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   FEncoding := EncodingUTF8;
@@ -203,13 +203,16 @@ var
   currSym: String;
   warning: String;
   fntIndex: Integer;
+  sheet: TsWorksheet;
 begin
   // Empty strings are blank cells -- nothing to do
   if (AText = '') then
     exit;
 
+  sheet := FWorksheet as TsWorksheet;
+
   // Create cell
-  cell := FWorksheet.AddCell(ARow, ACol);
+  cell := sheet.AddCell(ARow, ACol);
 
   // Format, rich-text formatting parameters
   // Reject non-used runs; adapt font index to the workbook.
@@ -223,10 +226,10 @@ begin
   end else
   begin
     // Get cell font and use it in the cell format
-    fntIndex := FWorkbook.FindFont(FCellFont.FontName, FCellFont.Size,
+    fntIndex := (FWorkbook as TsWorkbook).FindFont(FCellFont.FontName, FCellFont.Size,
       FCellFont.Style, FCellFont.Color, FCellFont.Position);
     if fntIndex = -1 then
-      fntIndex := FWorkbook.AddFont(FCellFont.FontName, FCellFont.Size,
+      fntIndex := (FWorkbook as TsWorkbook).AddFont(FCellFont.FontName, FCellFont.Size,
         FCellFont.Style, FCellFont.Color, FCellFont.Position);
     FCurrCellFormat.FontIndex := fntIndex;
   end;
@@ -234,25 +237,25 @@ begin
     Include(FCurrCellFormat.UsedFormattingFields, uffFont) else
     Exclude(FCurrCellFormat.UsedFormattingFields, uffFont);
   // Store the cell format in the workbook
-  cell^.FormatIndex := FWorkbook.AddCellFormat(FCurrCellFormat);
+  cell^.FormatIndex := (FWorkbook as TsWorkbook).AddCellFormat(FCurrCellFormat);
 
   // Merged cells
   if (FColSpan > 0) or (FRowSpan > 0) then begin
-    FWorksheet.MergeCells(ARow, ACol, ARow + FRowSpan, ACol + FColSpan);
+    sheet.MergeCells(ARow, ACol, ARow + FRowSpan, ACol + FColSpan);
     FRowSpan := 0;
     FColSpan := 0;
   end;
 
   // Hyperlink
   if FHRef <> '' then begin
-    FWorksheet.WriteHyperlink(cell, FHRef);
+    sheet.WriteHyperlink(cell, FHRef);
     FHRef := '';
   end;
 
   // Case: Do not try to interpret the strings. --> everything is a LABEL cell.
   if not HTMLParams.DetectContentType then
   begin
-    FWorksheet.WriteText(cell, AText, FCurrRichTextParams);
+    sheet.WriteText(cell, AText, FCurrRichTextParams);
     exit;
   end;
 
@@ -261,9 +264,9 @@ begin
     dblValue, nf, decs, currSym, warning) then
   begin
     if currSym <> '' then
-      FWorksheet.WriteCurrency(cell, dblValue, nfCurrency, decs, currSym)
+      sheet.WriteCurrency(cell, dblValue, nfCurrency, decs, currSym)
     else
-      FWorksheet.WriteNumber(cell, dblValue, nf, decs);
+      sheet.WriteNumber(cell, dblValue, nf, decs);
     if warning <> '' then
       FWorkbook.AddErrorMsg('Cell %s: %s', [GetCellString(ARow, ACol), warning]);
     exit;
@@ -273,19 +276,19 @@ begin
   // No idea how to apply the date/time formatsettings here...
   if IsDateTimevalue(AText, FFormatSettings, dtValue, nf) then
   begin
-    FWorksheet.WriteDateTime(cell, dtValue, nf);
+    sheet.WriteDateTime(cell, dtValue, nf);
     exit;
   end;
 
   // Check for a BOOLEAN cell
   if IsBoolValue(AText, HTMLParams.TrueText, HTMLParams.FalseText, boolValue) then
   begin
-    FWorksheet.WriteBoolValue(cell, boolValue);
+    sheet.WriteBoolValue(cell, boolValue);
     exit;
   end;
 
   // What is left is handled as a TEXT cell
-  FWorksheet.WriteText(cell, AText, FCurrRichTextParams);
+  sheet.WriteText(cell, AText, FCurrRichTextParams);
 end;
 
 { Stores a font in the internal font list. Does not allow duplicates. }
@@ -378,9 +381,9 @@ begin
   for i:=0 to High(FCurrRichTextParams) do
   begin
     fnt := TsFont(FFontList[FCurrRichTextParams[i].FontIndex]);
-    fntIndex := FWorkbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+    fntIndex := (FWorkbook as TsWorkbook).FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
     if fntIndex = -1 then
-      fntIndex := FWorkbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+      fntIndex := (FWorkbook as TsWorkbook).AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
     FCurrRichTextParams[i].FontIndex := fntIndex;
   end;
 end;
@@ -485,6 +488,7 @@ end;
 procedure TsHTMLReader.ProcessEndTags(NoCaseTag, ActualTag: String);
 var
   fntIndex: Integer;
+  sheet: TsWorksheet;
 begin
   Unused(ActualTag);
   if not FInTable then exit;
@@ -501,9 +505,11 @@ begin
 
   if not FInCell then exit;
 
+  sheet := FWorksheet as TsWorksheet;
+
   if (NoCaseTag = '</TD>') or (NoCaseTag = '</TH>') then
   begin
-    while FWorksheet.IsMerged(FWorksheet.FindCell(FCurrRow, FCurrCol)) do
+    while sheet.IsMerged(sheet.FindCell(FCurrRow, FCurrCol)) do
       inc(FCurrCol);
     AddCell(FCurrRow, FCurrCol, FCellText);
     FInCell := false;
@@ -807,7 +813,7 @@ begin
   if idx = -1 then
     idx := FAttrList.IndexOfName('size');
   if idx > -1 then begin
-    defFntSize := FWorkbook.GetDefaultFont.Size;
+    defFntSize := (FWorkbook as TsWorkbook).GetDefaultFont.Size;
     s := FAttrList[idx].Value;
     case s of
       'medium',   '3' : AFont.Size := defFntSize;
@@ -1022,7 +1028,7 @@ procedure TsHTMLReader.InitFont(AFont: TsFont);
 var
   fnt: TsFont;
 begin
-  fnt := FWorkbook.GetDefaultFont;
+  fnt := (FWorkbook as TsWorkbook).GetDefaultFont;
   AFont.FontName := fnt.FontName;
   AFont.Size := fnt.Size;
   AFont.Style := fnt.Style;
@@ -1056,10 +1062,10 @@ begin
   try
     list.LoadFromStream(AStream);
     ReadFromStrings(list, AParams);
-    if FWorkbook.GetWorksheetCount = 0 then
+    if (FWorkbook as TsWorkbook).GetWorksheetCount = 0 then
     begin
       FWorkbook.AddErrorMsg('Requested table not found, or no tables in html file');
-      FWorkbook.AddWorksheet('Dummy');
+      TsWorkbook(FWorkbook).AddWorksheet('Dummy');
     end;
   finally
     list.Free;
@@ -1106,14 +1112,14 @@ begin
     inc(FTableCounter);
     if (HTMLParams.TableIndex >= 0) and (FTableCounter <> HTMLParams.TableIndex) then
       exit;
-    FWorksheet := FWorkbook.AddWorksheet(Format('Table #%d', [FTableCounter+1]));
+    FWorksheet := TsWorkbook(FWorkbook).AddWorksheet(Format('Table #%d', [FTableCounter+1]));
     FInTable := true;
     FCurrRow := -1;
     FCurrCol := -1;
     FFontStack.Push(AddFont(FCurrFont));
     FAttrList.Parse(ActualTag);
     ReadFont(FCurrFont);
-    FWorkbook.ReplaceFont(DEFAULT_FONTINDEX, FCurrFont.FontName, FCurrFont.Size,
+    TsWorkbook(FWorkbook).ReplaceFont(DEFAULT_FONTINDEX, FCurrFont.FontName, FCurrFont.Size,
       FCurrFont.Style, FCurrFont.Color, FCurrFont.Position);
     FCellFont.CopyOf(FCurrFont);
     exit;
@@ -1179,7 +1185,7 @@ end;
 {==============================================================================}
 {                             TsHTMLWriter                                     }
 {==============================================================================}
-constructor TsHTMLWriter.Create(AWorkbook: TsWorkbook);
+constructor TsHTMLWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   FPointSeparatorSettings := DefaultFormatSettings;
@@ -1311,17 +1317,20 @@ var
   col: PCol;
   w: Single;
   rLast: Cardinal;
+  sheet: TsWorksheet;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   if AColIndex < 0 then  // Row header column
   begin
-    rLast := FWorksheet.GetLastRowIndex;
-    w := FWorkbook.ConvertUnits(Length(IntToStr(rLast)) + 2, suChars, suPoints);
+    rLast := sheet.GetLastRowIndex;
+    w := (FWorkbook as TsWorkbook).ConvertUnits(Length(IntToStr(rLast)) + 2, suChars, suPoints);
   end else
   begin
-    w := FWorksheet.ReadDefaultColWidth(suPoints);
-    col := FWorksheet.FindCol(AColIndex);
+    w := sheet.ReadDefaultColWidth(suPoints);
+    col := sheet.FindCol(AColIndex);
     if (col <> nil) and (col^.Width > 0) then
-      w := FWorkbook.ConvertUnits(col^.Width, FWorkbook.Units, suPoints);
+      w := (FWorkbook as TsWorkbook).ConvertUnits(col^.Width, FWorkbook.Units, suPoints);
   end;
   Result:= Format(' width="%.1fpt"', [w], FPointSeparatorSettings);
 end;
@@ -1342,7 +1351,7 @@ function TsHTMLWriter.GetFontAsStyle(AFontIndex: Integer): String;
 var
   font: TsFont;
 begin
-  font := FWorkbook.GetFont(AFontIndex);
+  font := (FWorkbook as TsWorkbook).GetFont(AFontIndex);
   Result := Format('font-family:''%s'';font-size:%.1fpt;color:%s;', [
     font.FontName, font.Size, ColorToHTMLColorStr(font.Color)], FPointSeparatorSettings);
   if fssBold in font.Style then
@@ -1381,7 +1390,7 @@ var
   r1, r2, c1, c2: Cardinal;
 begin
   Result := '';
-  FWorksheet.FindMergedRange(AMergeBase, r1, c1, r2, c2);
+  (FWorksheet as TsWorksheet).FindMergedRange(AMergeBase, r1, c1, r2, c2);
   if c1 <> c2 then
     Result := Result + ' colspan="' + IntToStr(c2-c1+1) + '"';
   if r1 <> r2 then
@@ -1393,11 +1402,11 @@ var
   h: Single;
   row: PRow;
 begin
-  h := FWorksheet.ReadDefaultRowHeight(suPoints);
-  row := FWorksheet.FindRow(ARowIndex);
+  h := (FWorksheet as TsWorksheet).ReadDefaultRowHeight(suPoints);
+  row := (FWorksheet as TsWorksheet).FindRow(ARowIndex);
   if row <> nil then begin
     if row^.RowHeightType = rhtCustom then
-      h := abs(FWorkbook.ConvertUnits(row^.Height, FWorkbook.Units, suPoints));
+      h := abs((FWorkbook as TsWorkbook).ConvertUnits(row^.Height, FWorkbook.Units, suPoints));
   end;
   Result := Format(' height="%.1fpt"', [h], FPointSeparatorSettings);
 end;
@@ -1441,7 +1450,7 @@ end;
 
 procedure TsHTMLWriter.InternalWriteToStream(AStream: TStream);
 begin
-  FWorkbook.UpdateCaches;
+  (FWorkbook as TsWorkbook).UpdateCaches;
   AppendToStream(AStream,
     '<!DOCTYPE html>');
 
@@ -1472,9 +1481,9 @@ begin
   if ACell = nil then
     exit;
 
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do
+  for i:=0 to (FWorkbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(i);
     for hyperlink in sheet.Hyperlinks do
     begin
       SplitHyperlink(hyperlink^.Target, target, ABookmark);
@@ -1503,20 +1512,23 @@ end;
 procedure TsHTMLWriter.WriteBody(AStream: TStream);
 var
   i: Integer;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   AppendToStream(AStream,
     '<body>');
   if FWindowsClipboardMode or (HTMLParams.SheetIndex < 0) then      // active sheet
   begin
-    if FWorkbook.ActiveWorksheet = nil then
-      FWorkbook.SelectWorksheet(FWorkbook.GetWorksheetByIndex(0));
-    WriteWorksheet(AStream, FWorkbook.ActiveWorksheet)
+    if book.ActiveWorksheet = nil then
+      book.SelectWorksheet(book.GetWorksheetByIndex(0));
+    WriteWorksheet(AStream, book.ActiveWorksheet)
   end else
   if HTMLParams.SheetIndex = MaxInt then  // all sheets
-    for i:=0 to FWorkbook.GetWorksheetCount-1 do
-      WriteWorksheet(AStream, FWorkbook.GetWorksheetByIndex(i))
+    for i:=0 to book.GetWorksheetCount-1 do
+      WriteWorksheet(AStream, book.GetWorksheetByIndex(i))
   else                                    // specific sheet
-    WriteWorksheet(AStream, FWorkbook.GetWorksheetbyIndex(HTMLParams.SheetIndex));
+    WriteWorksheet(AStream, book.GetWorksheetbyIndex(HTMLParams.SheetIndex));
   AppendToStream(AStream,
     '</body>');
 end;
@@ -1538,7 +1550,7 @@ var
   s: String;
 begin
   Unused(AValue, ACol, ARow);
-  s := FWorksheet.ReadAsText(ACell);
+  s := (FWorksheet as TsWorksheet).ReadAsText(ACell);
   AppendToStream(AStream,
     '<div>' + s + '</div>');
 end;
@@ -1549,7 +1561,7 @@ var
   s: String;
 begin
   Unused(AValue, ACol, ARow);
-  s := FWOrksheet.ReadAsText(ACell);
+  s := (FWorksheet as TsWorksheet).ReadAsText(ACell);
   AppendToStream(AStream,
     '<div>' + s + '</div>');
 end;
@@ -1593,13 +1605,13 @@ begin
     exit;
 
   style := '';
-  cellfnt := FWorksheet.ReadCellFont(ACell);
+  cellfnt := (FWorksheet as TsWorksheet).ReadCellFont(ACell);
 
   // Hyperlink
   target := '';
   if FWorksheet.HasHyperlink(ACell) then
   begin
-    hyperlink := FWorksheet.FindHyperlink(ACell);
+    hyperlink := (FWorksheet as TsWorksheet).FindHyperlink(ACell);
     SplitHyperlink(hyperlink^.Target, target, bookmark);
 
     n := Length(hyperlink^.Target);
@@ -1657,7 +1669,7 @@ begin
     begin
       // formatted section
       rtParam := ACell^.RichTextParams[i];
-      fnt := FWorkbook.GetFont(rtParam.FontIndex);
+      fnt := (FWorkbook as TsWorkbook).GetFont(rtParam.FontIndex);
       style := GetFontAsStyle(rtParam.FontIndex);
       if style <> '' then
         style := ' style="' + style +'"';
@@ -1684,7 +1696,7 @@ var
   s: String;
 begin
   Unused(ARow, ACol, AValue);
-  s := FWorksheet.ReadAsText(ACell, FWorkbook.FormatSettings);
+  s := (FWorksheet as TsWorksheet).ReadAsText(ACell, FWorkbook.FormatSettings);
   AppendToStream(AStream,
     '<div>' + s + '</div>');
 end;
@@ -1697,8 +1709,8 @@ var
 begin
   AppendToStream(AStream,
     '<style>' + LineEnding);
-  for i:=0 to FWorkbook.GetNumCellFormats-1 do begin
-    fmt := FWorkbook.GetPointerToCellFormat(i);
+  for i:=0 to (FWorkbook as TsWorkbook).GetNumCellFormats-1 do begin
+    fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(i);
     fmtStr := CellFormatAsString(fmt);
     if fmtStr <> '' then
       fmtStr := Format('  td.style%d {%s}' + LineEnding, [i+1, fmtStr]);
@@ -1741,7 +1753,7 @@ begin
   end;
 end;
 
-procedure TsHTMLWriter.WriteWorksheet(AStream: TStream; ASheet: TsWorksheet);
+procedure TsHTMLWriter.WriteWorksheet(AStream: TStream; ASheet: TsBasicWorksheet);
 var
   r, rFirst, rLast: LongInt;
   c, cFirst, cLast: LongInt;
@@ -1751,18 +1763,19 @@ var
   style, s: String;
   fixedLayout: Boolean;
   fmt: PsCellFormat;
+  sheet: TsWorksheet absolute ASheet;
 begin
   FWorksheet := ASheet;
 
-  rFirst := FWorksheet.GetFirstRowIndex;
-  cFirst := FWorksheet.GetFirstColIndex;
-  rLast := FWorksheet.GetLastOccupiedRowIndex;
-  cLast := FWorksheet.GetLastOccupiedColIndex;
+  rFirst := sheet.GetFirstRowIndex;
+  cFirst := sheet.GetFirstColIndex;
+  rLast := sheet.GetLastOccupiedRowIndex;
+  cLast := sheet.GetLastOccupiedColIndex;
 
   fixedLayout := false;
   for c:=cFirst to cLast do
   begin
-    col := FWorksheet.GetCol(c);
+    col := sheet.GetCol(c);
     if col <> nil then
     begin
       fixedLayout := true;
@@ -1812,7 +1825,7 @@ begin
         style := ' style="' + style + '"';
       if fixedLayout then
         style := style + GetColWidthAsAttr(c);
-      col := FWorksheet.FindCol(c);
+      col := sheet.FindCol(c);
       if (col <> nil) and (col^.FormatIndex > 0) then
         style := style + Format(' class="style%d"', [col^.FormatIndex+1]);
 
@@ -1822,7 +1835,7 @@ begin
   end;
 
   for r := rFirst to rLast do begin
-    row := FWorksheet.FindRow(r);
+    row := sheet.FindRow(r);
     AppendToStream(AStream,
         '<tr>' + LineEnding);
 
@@ -1840,8 +1853,8 @@ begin
 
     for c := cFirst to cLast do begin
       // Pointer to current cell in loop
-      cell := FWorksheet.FindCell(r, c);
-      col := FWorksheet.FindCol(c);
+      cell := sheet.FindCell(r, c);
+      col := sheet.FindCol(c);
 
       // Cell formatting via predefined styles ("class")
       style := '';
@@ -1849,17 +1862,17 @@ begin
       if cell <> nil then
       begin
         style := Format(' class="style%d"', [cell^.FormatIndex+1]);
-        fmt := FWorkbook.GetPointerToCellFormat(cell^.FormatIndex);
+        fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(cell^.FormatIndex);
       end else
       if (row <> nil) and (row^.FormatIndex > 0) then
       begin
         style := Format(' class="style%d"', [row^.FormatIndex+1]);
-        fmt := FWorkbook.GetPointerToCellFormat(row^.FormatIndex);
+        fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(row^.FormatIndex);
       end else
       if (col <> nil) and (col^.FormatIndex > 0) then
       begin
         style := Format(' class="style%d"', [col^.FormatIndex+1]);
-        fmt := FWorkbook.GetPointerToCellFormat(col^.FormatIndex);
+        fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(col^.FormatIndex);
       end;
 
       // Overriding differences between html and fps formatting
@@ -1888,9 +1901,9 @@ begin
       end;
 
       // Merged cells
-      if FWorksheet.IsMerged(cell) then
+      if sheet.IsMerged(cell) then
       begin
-        if FWorksheet.IsMergeBase(cell) then
+        if sheet.IsMergeBase(cell) then
           style := style + GetMergedRangeAsStyle(cell)
         else
           Continue;
diff --git a/components/fpspreadsheet/source/common/fpshtmlutils.pas b/components/fpspreadsheet/source/common/fpshtmlutils.pas
index a37da2427..9af668313 100644
--- a/components/fpspreadsheet/source/common/fpshtmlutils.pas
+++ b/components/fpspreadsheet/source/common/fpshtmlutils.pas
@@ -5,7 +5,7 @@ unit fpsHTMLUtils;
 interface
 
 uses
-  Classes, SysUtils, contnrs, fpstypes, fpspreadsheet;
+  Classes, SysUtils, contnrs, fpstypes;
 
 type
   TsHTMLEntity = record
@@ -39,11 +39,11 @@ type
 
   TsTagCase = (tcLowercase, tcUppercase, tcProperCase);
 
-procedure HTMLToRichText(AWorkbook: TsWorkbook; AFont: TsFont;
+procedure HTMLToRichText(AWorkbook: TsBasicWorkbook; AFont: TsFont;
   const AHTMLText: String; out APlainText: String;
   out ARichTextParams: TsRichTextParams);
 
-procedure RichTextToHTML(AWorkbook: TsWorkbook; AFont: TsFont;
+procedure RichTextToHTML(AWorkbook: TsBasicWorkbook; AFont: TsFont;
   const APlainText: String; const ARichTextParams: TsRichTextParams;
   out AHTMLText: String; APrefix:String = ''; ATagCase: TsTagCase = tcLowercase);
 
@@ -52,7 +52,7 @@ implementation
 
 uses
   math, lazUtf8, fasthtmlparser,
-  fpsUtils, fpsClasses;
+  fpsUtils, fpsClasses, fpspreadsheet;
 
 const
   // http://unicode.e-workers.de/entities.php
@@ -940,7 +940,7 @@ end;
   @@param ARichtTextParams   Rich-text parameters corresponding to the embedded
                              html tags
 -------------------------------------------------------------------------------}
-procedure HTMLToRichText(AWorkbook: TsWorkbook; AFont: TsFont;
+procedure HTMLToRichText(AWorkbook: TsBasicWorkbook; AFont: TsFont;
   const AHTMLText: String; out APlainText: String;
   out ARichTextParams: TsRichTextParams);
 var
@@ -949,7 +949,7 @@ var
   len: Integer;
   nrtp: Integer;
 begin
-  analyzer := TsHTMLAnalyzer.Create(AWorkbook, AFont, AHTMLText + '<end>');
+  analyzer := TsHTMLAnalyzer.Create(AWorkbook as TsWorkbook, AFont, AHTMLText + '<end>');
   try
     analyzer.PreserveSpaces := true;
     analyzer.Exec;
@@ -1187,7 +1187,7 @@ end;
   Constructs a html-coded string from a plain text string and
   rich-text parameters
 -------------------------------------------------------------------------------}
-procedure RichTextToHTML(AWorkbook: TsWorkbook; AFont: TsFont;
+procedure RichTextToHTML(AWorkbook: TsBasicWorkbook; AFont: TsFont;
   const APlainText: String; const ARichTextParams: TsRichTextParams;
   out AHTMLText: String; APrefix: String = ''; ATagCase: TsTagCase = tcLowercase);
 var
@@ -1197,7 +1197,7 @@ begin
     AHTMLText := APlainText
   else
   begin
-    composer := TsHTMLComposer.Create(AWorkbook, AFont, APrefix, ATagCase);
+    composer := TsHTMLComposer.Create(AWorkbook as TsWorkbook, AFont, APrefix, ATagCase);
     try
       AHTMLText := composer.Exec(APlainText, ARichTextParams);
     finally
diff --git a/components/fpspreadsheet/source/common/fpsopendocument.pas b/components/fpspreadsheet/source/common/fpsopendocument.pas
index a1eed437e..3452a41de 100644
--- a/components/fpspreadsheet/source/common/fpsopendocument.pas
+++ b/components/fpspreadsheet/source/common/fpsopendocument.pas
@@ -42,7 +42,7 @@ uses
  {$ELSE}
   fpszipper,
  {$ENDIF}
-  fpstypes, fpspreadsheet, fpsReaderWriter, fpsutils, fpsHeaderFooterParser,
+  fpstypes, fpsReaderWriter, fpsutils, fpsHeaderFooterParser,
   fpsNumFormat, fpsxmlcommon, fpsPagelayout;
   
 type
@@ -100,7 +100,8 @@ type
     procedure ApplyColWidths;
     procedure ApplyStyleToCell(ACell: PCell; AStyleIndex: Integer);
     function ApplyStyleToCell(ACell: PCell; AStyleName: String): Boolean;
-    function ApplyTableStyle(ASheet: TsWorksheet; AStyleName: String): Boolean;
+    function ApplyTableStyle(ASheet: TsBasicWorksheet;
+      AStyleName: String): Boolean;
     function ExtractBoolFromNode(ANode: TDOMNode): Boolean;
     function ExtractDateTimeFromNode(ANode: TDOMNode;
       ANumFormat: TsNumberFormat; const AFormatStr: String): TDateTime;
@@ -128,11 +129,11 @@ type
       var AFontColor: TsColor);
     function ReadHeaderFooterText(ANode: TDOMNode): String;
     procedure ReadPictures(AStream: TStream);
-    procedure ReadPrintRanges(ATableNode: TDOMNode; ASheet: TsWorksheet);
+    procedure ReadPrintRanges(ATableNode: TDOMNode; ASheet: TsBasicWorksheet);
     procedure ReadRowsAndCells(ATableNode: TDOMNode);
     procedure ReadRowStyle(AStyleNode: TDOMNode);
     procedure ReadShapes(ATableNode: TDOMNode);
-    procedure ReadSheetProtection(ANode: TDOMNode; ASheet: TsWorksheet);
+    procedure ReadSheetProtection(ANode: TDOMNode; ASheet: TsBasicWorksheet);
     procedure ReadTableStyle(AStyleNode: TDOMNode);
 
   protected
@@ -163,7 +164,7 @@ type
       ACellNode: TDOMNode); reintroduce;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
 
     { General reading methods }
@@ -184,25 +185,25 @@ type
 
     // Routines to write parts of files
     procedure WriteAutomaticStyles(AStream: TStream);
-    procedure WriteCellRow(AStream: TStream; ASheet: TsWorksheet;
+    procedure WriteCellRow(AStream: TStream; ASheet: TsBasicWorksheet;
       ARowIndex, ALastColIndex: Integer);
     procedure WriteCellStyles(AStream: TStream);
     procedure WriteColStyles(AStream: TStream);
-    procedure WriteColumns(AStream: TStream; ASheet: TsWorksheet);
-    procedure WriteEmptyRow(AStream: TStream; ASheet: TsWorksheet;
+    procedure WriteColumns(AStream: TStream; ASheet: TsBasicWorksheet);
+    procedure WriteEmptyRow(AStream: TStream; ASheet: TsBasicWorksheet;
       ARowIndex, AFirstColIndex, ALastColIndex, ALastRowIndex: Integer;
       out ARowsRepeated: Integer);
     procedure WriteFontNames(AStream: TStream);
     procedure WriteMasterStyles(AStream: TStream);
-    procedure WriteNamedExpressions(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteNamedExpressions(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure WriteNumFormats(AStream: TStream);
     procedure WriteRowStyles(AStream: TStream);
-    procedure WriteRowsAndCells(AStream: TStream; ASheet: TsWorksheet);
-    procedure WriteShapes(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteRowsAndCells(AStream: TStream; ASheet: TsBasicWorksheet);
+    procedure WriteShapes(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure WriteTableSettings(AStream: TStream);
     procedure WriteTableStyles(AStream: TStream);
     procedure WriteTextStyles(AStream: TStream);
-    procedure WriteVirtualCells(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteVirtualCells(AStream: TStream; ASheet: TsBasicWorksheet);
 
     function WriteBackgroundColorStyleXMLAsString(const AFormat: TsCellFormat): String;
     function WriteBiDiModeStyleXMLAsString(const AFormat: TsCellFormat): String;
@@ -217,9 +218,9 @@ type
     function WriteHeaderFooterFontXMLAsString(AFont: TsHeaderFooterFont): String;
     function WriteHorAlignmentStyleXMLAsString(const AFormat: TsCellFormat): String;
     function WritePageLayoutXMLAsString(AStyleName: String; const APageLayout: TsPageLayout): String;
-    function WritePrintRangesXMLAsString(ASheet: TsWorksheet): String;
-    function WriteSheetProtectionXMLAsString(ASheet: TsWorksheet): String;
-    function WriteSheetProtectionDetailsXMLAsString(ASheet: TsWorksheet): String;
+    function WritePrintRangesXMLAsString(ASheet: TsBasicWorksheet): String;
+    function WriteSheetProtectionXMLAsString(ASheet: TsBasicWorksheet): String;
+    function WriteSheetProtectionDetailsXMLAsString(ASheet: TsBasicWorksheet): String;
     function WriteTextRotationStyleXMLAsString(const AFormat: TsCellFormat): String;
     function WriteVertAlignmentStyleXMLAsString(const AFormat: TsCellFormat): String;
     function WriteWordwrapStyleXMLAsString(const AFormat: TsCellFormat): String;
@@ -238,7 +239,7 @@ type
       out AHeader, AFooter: String);
     procedure GetHeaderFooterImagePosStr(APagelayout: TsPageLayout;
       out AHeader, AFooter: String);
-    procedure GetRowStyleAndHeight(ASheet: TsWorksheet; ARowIndex: Integer;
+    procedure GetRowStyleAndHeight(ASheet: TsBasicWorksheet; ARowIndex: Integer;
       out AStyleName: String; out AHeight: Single);
     procedure InternalWriteToStream(AStream: TStream);
     procedure ListAllColumnStyles;
@@ -274,7 +275,7 @@ type
       const AValue: double; ACell: PCell); override;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
 
     { General writing methods }
@@ -297,7 +298,8 @@ uses
  {$IFDEF FPS_VARISBOOL}
   fpsPatches,
  {$ENDIF}
-  fpsStrings, fpsStreams, fpsCrypto, fpsClasses, fpsExprParser, fpsImages;
+  fpsStrings, fpsStreams, fpsCrypto, fpsClasses, fpspreadsheet,
+  fpsExprParser, fpsImages;
 
 const
   { OpenDocument general XML constants }
@@ -1020,7 +1022,7 @@ end;
 {                         TsSpreadOpenDocReader                                }
 {******************************************************************************}
 
-constructor TsSpreadOpenDocReader.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadOpenDocReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -1106,9 +1108,11 @@ var
   colWidth: Single;
   colWidthType: TsColWidthType;
   lastOccCol: Integer;
+  sheet: TsWorksheet;
 begin
-  defColWidth := FWorksheet.ReadDefaultColWidth(FWorkbook.Units);
-  lastOccCol := FWorksheet.GetLastOccupiedColIndex;
+  sheet := FWorksheet as TsWorksheet;
+  defColWidth := sheet.ReadDefaultColWidth(FWorkbook.Units);
+  lastOccCol := sheet.GetLastOccupiedColIndex;
   for i:=0 to FColumnList.Count-1 do
   begin
     colData := TColumnData(FColumnList[i]);
@@ -1139,7 +1143,7 @@ begin
 
     // Write non-default column width to the worksheet
     if (colWidthType = cwtCustom)  then
-      FWorksheet.WriteColWidth(colIndex, colWidth, FWorkbook.Units);
+      sheet.WriteColWidth(colIndex, colWidth, FWorkbook.Units);
 
     // Note: we don't store the column format index here; this is done in the
     // row/cell reading method (ReadRowsAndCells).
@@ -1167,17 +1171,20 @@ end;
 procedure TsSpreadOpenDocReader.ApplyStyleToCell(ACell: PCell; AStyleIndex: Integer);
 var
   fmt: TsCellFormat;
+  sheet: TsWorksheet;
 begin
-  if FWorksheet.HasHyperlink(ACell) then
-    FWorksheet.WriteFont(ACell, HYPERLINK_FONTINDEX);
+  sheet := FWorksheet as TsWorksheet;
+
+  if sheet.HasHyperlink(ACell) then
+    sheet.WriteFont(ACell, HYPERLINK_FONTINDEX);
 
   fmt := FCellFormatList.Items[AStyleIndex]^;
-  if (AStyleIndex = 0) and FWorksheet.HasHyperlink(ACell) then begin
+  if (AStyleIndex = 0) and sheet.HasHyperlink(ACell) then begin
     // Make sure to use hyperlink font for hyperlink cells in case of default cell style
     fmt.FontIndex := HYPERLINK_FONTINDEX;
     Include(fmt.UsedFormattingFields, uffFont);
   end;
-  ACell^.FormatIndex := FWorkbook.AddCellFormat(fmt);
+  ACell^.FormatIndex := (FWorkbook as TsWorkbook).AddCellFormat(fmt);
 end;
 
 { Applies the style data referred to by the style name to the specified cell
@@ -1191,7 +1198,7 @@ begin
   Result := false;
 
   if FWorksheet.HasHyperlink(ACell) then
-    FWorksheet.WriteFont(ACell, HYPERLINK_FONTINDEX);
+    (FWorksheet as TsWorksheet).WriteFont(ACell, HYPERLINK_FONTINDEX);
 
   styleIndex := ExtractFormatIndexFromStyle(AStyleName, ACell^.Col);
   (*
@@ -1217,16 +1224,17 @@ begin
     fmt.FontIndex := HYPERLINK_FONTINDEX;
     Include(fmt.UsedFormattingFields, uffFont);
   end;
-  ACell^.FormatIndex := FWorkbook.AddCellFormat(fmt);
+  ACell^.FormatIndex := (FWorkbook as TsWorkbook).AddCellFormat(fmt);
 
   Result := true;
 end;
 
-function TsSpreadOpenDocReader.ApplyTableStyle(ASheet: TsWorksheet;
+function TsSpreadOpenDocReader.ApplyTableStyle(ASheet: TsBasicWorksheet;
   AStyleName: String): Boolean;
 var
   styleIndex: Integer;
   tableStyle: TTableStyleData;
+  sheet: TsWorksheet absolute ASheet;
 begin
   Result := false;
   if (AStyleName = '') or (ASheet = nil) then
@@ -1236,9 +1244,9 @@ begin
     exit;
   tableStyle := TTableStyleData(FTableStyleList[styleIndex]);
   if (tableStyle.BiDiMode = bdRTL) or (tableStyle.BiDiMode = bdLTR) then
-    ASheet.BiDiMode := tableStyle.BiDiMode;
+    sheet.BiDiMode := tableStyle.BiDiMode;
   if tableStyle.Hidden then
-    ASheet.Options := ASheet.Options + [soHidden];
+    sheet.Options := sheet.Options + [soHidden];
   Result := true;
 end;
 
@@ -1467,8 +1475,8 @@ var
 begin
   if (boIgnoreFormulas in FWorkbook.Options) then
     exit;
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+  for i:=0 to (FWorkbook as TsWorkbook).GetWorksheetCount-1 do begin
+    sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(i);
     for cell in sheet.Cells do
       if HasFormula(cell) then FixCell(cell);
   end;
@@ -1496,7 +1504,7 @@ var
 begin
   if not Assigned(AStylesNode) then
     exit;
-  defFnt := Workbook.GetDefaultFont;
+  defFnt := (Workbook as TsWorkbook).GetDefaultFont;
   layoutNode := AStylesNode.FirstChild;
   while layoutNode <> nil do
   begin
@@ -1664,7 +1672,7 @@ begin
                 imgpos := GetAttrValue(childchild, 'style:position');
                 if (href <> '') and (imgpos <> '') then
                 begin
-                  n := FWorkbook.FindEmbeddedObj(ExtractFileName(href));
+                  n := (FWorkbook as TsWorkbook).FindEmbeddedObj(ExtractFileName(href));
                   if n > -1 then
                   begin
                     if pos('left', imgpos) > 0 then hfs := hfsLeft else
@@ -1693,7 +1701,7 @@ var
   parser: TsSpreadOpenDocHeaderFooterParser;
   defFnt: TsHeaderFooterFont;
 begin
-  defFnt := TsHeaderFooterFont.Create(Workbook.GetDefaultFont);
+  defFnt := TsHeaderFooterFont.Create((Workbook as TsWorkbook).GetDefaultFont);
   parser := TsSpreadOpenDocHeaderFooterParser.Create(ANode.FirstChild,
     FHeaderFooterFontList, defFnt);
   try
@@ -1862,12 +1870,12 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
-  FWorkSheet.WriteBlank(cell);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
+  (FWorkSheet as TsWorksheet).WriteBlank(cell);
   ApplyStyleToCell(cell, AStyleIndex);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadOpenDocReader.ReadBoolean(ARow, ACol: Cardinal;
@@ -1882,10 +1890,10 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
 
   boolValue := ExtractBoolFromNode(ACellNode);
-  FWorkSheet.WriteBoolValue(cell, boolValue);
+  (FWorkSheet as TsWorksheet).WriteBoolValue(cell, boolValue);
 
   ApplyStyleToCell(cell, AStyleIndex);
   {
@@ -1893,7 +1901,7 @@ begin
   ApplyStyleToCell(cell, stylename);
    }
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 { Collection columns used in the given table. The columns contain links to
@@ -2000,7 +2008,7 @@ begin
       s := GetAttrValue(styleChildNode, 'style:column-width');
       if s <> '' then
       begin
-        colWidth := FWorkbook.ConvertUnits(HTMLLengthStrToPts(s), suPoints, FWorkbook.Units);
+        colWidth := (FWorkbook as TsWorkbook).ConvertUnits(HTMLLengthStrToPts(s), suPoints, FWorkbook.Units);
         // convert to workbook units
         break;
       end;
@@ -2065,7 +2073,7 @@ begin
     cellChildNode := cellChildNode.NextSibling;
   end;
   if found then
-    FWorksheet.WriteComment(ARow, ACol, comment);
+    (FWorksheet as TsWorksheet).WriteComment(ARow, ACol, comment);
 end;
 
 procedure TsSpreadOpenDocReader.ReadDateTime(ARow, ACol: Cardinal;
@@ -2081,18 +2089,20 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
 
   ApplyStyleToCell(cell, AStyleIndex);
   //styleName := GetAttrValue(ACellNode, 'table:style-name');
   //ApplyStyleToCell(cell, stylename);
-  fmt := FWorkbook.GetPointerToCellFormat(cell^.FormatIndex);;
+  fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(cell^.FormatIndex);;
 
   dt := ExtractDateTimeFromNode(ACellNode, fmt^.NumberFormat, fmt^.NumberFormatStr);
-  FWorkSheet.WriteDateTime(cell, dt, fmt^.NumberFormat, fmt^.NumberFormatStr);
+  (FWorkSheet as TsWorksheet).WriteDateTime(cell,
+    dt, fmt^.NumberFormat, fmt^.NumberFormatStr
+  );
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(Workbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadOpenDocReader.ReadError(ARow, ACol: Cardinal;
@@ -2107,11 +2117,12 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := TsWorksheet(FWorksheet).AddCell(ARow, ACol);
 
   if ExtractErrorFromNode(ACellNode, errValue) then
-    FWorkSheet.WriteErrorValue(cell, errValue) else
-    FWorksheet.WriteText(cell, 'ERROR');
+    TsWorksheet(FWorkSheet).WriteErrorValue(cell, errValue)
+  else
+    TsWorksheet(FWorksheet).WriteText(cell, 'ERROR');
 
   ApplyStyleToCell(cell, AStyleIndex);
   {
@@ -2120,7 +2131,7 @@ begin
   }
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(Workbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadOpenDocReader.ReadDateMode(SpreadSheetNode: TDOMNode);
@@ -2162,7 +2173,7 @@ begin
   InitCryptoInfo(cinfo);
   cinfo.PasswordHash := GetAttrValue(ANode, 'table:protection-key');
   cinfo.Algorithm := StrToAlgorithm(GetAttrValue(ANode, 'table:protection-key-digest-algorithm'));
-  Workbook.CryptoInfo := cinfo;
+  (Workbook as TsWorkbook).CryptoInfo := cinfo;
 end;
 
 { Reads font data from an xml node and returns the font elements. }
@@ -2398,14 +2409,14 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.GetCell(ARow, ACol);   // Don't use AddCell here
+    cell := TsWorksheet(FWorksheet).GetCell(ARow, ACol);   // Don't use AddCell here
 
   ApplyStyleToCell(cell, AStyleIndex);
   {
   styleName := GetAttrValue(ACellNode, 'table:style-name');
   ApplyStyleToCell(cell, stylename);
   }
-  fmt := Workbook.GetPointerToCellFormat(cell^.FormatIndex);
+  fmt := TsWorkbook(Workbook).GetPointerToCellFormat(cell^.FormatIndex);
 
   formula := '';
   if (boReadFormulas in FWorkbook.Options) then
@@ -2428,9 +2439,9 @@ begin
     // ... and store in cell's FormulaValue field.
     cell^.FormulaValue := formula;
     // Note: This formula is still in OpenDocument dialect. Conversion to
-    // Because fpsspreadsheet supports references to other sheets which might
-    // not have been loaded at this moment, conversion to ExcelA1 dialect
-    // (used by fps) is postponed until all sheets are read.
+    // ExcelA1 dialect (used by fps) is postponed until all sheets have beeon
+    // read (--> FixFormulas) because of possible references to other sheets
+    // which might not have been loaded yet at this moment.
 
     {$IFDEF FPSpreadDebug}
     DebugLn('  Formula found: ' + formula);
@@ -2448,11 +2459,11 @@ begin
   if (valueType = 'float') then
   begin
     if UpperCase(valueStr) = '1.#INF' then
-      FWorksheet.WriteNumber(cell, 1.0/0.0)
+      TsWorksheet(FWorksheet).WriteNumber(cell, 1.0/0.0)
     else
     begin
       floatValue := StrToFloat(valueStr, FPointSeparatorSettings);
-      FWorksheet.WriteNumber(cell, floatValue);
+      TsWorksheet(FWorksheet).WriteNumber(cell, floatValue);
     end;
     if IsDateTimeFormat(fmt^.NumberFormat) then
     begin
@@ -2472,7 +2483,7 @@ begin
   if (valueType = 'date') or (valueType = 'time') then
   begin
     floatValue := ExtractDateTimeFromNode(ACellNode, fmt^.NumberFormat, fmt^.NumberFormatStr);
-    FWorkSheet.WriteDateTime(cell, floatValue);
+    TsWorksheet(FWorkSheet).WriteDateTime(cell, floatValue);
   end else
   // (c) text
   if (valueType = 'string') and (calcextValueType <> 'error') then
@@ -2481,27 +2492,27 @@ begin
     if (node <> nil) and (node.FirstChild <> nil) then
     begin
       valueStr := node.FirstChild.Nodevalue;
-      FWorksheet.WriteText(cell, valueStr);
+      TsWorksheet(FWorksheet).WriteText(cell, valueStr);
     end;
   end else
   // (d) boolean
   if (valuetype = 'boolean') then
   begin
     boolValue := ExtractBoolFromNode(ACellNode);
-    FWorksheet.WriteBoolValue(cell, boolValue);
+    TsWorksheet(FWorksheet).WriteBoolValue(cell, boolValue);
   end else
   if (calcextValuetype = 'error') then
   begin
     if ExtractErrorFromNode(ACellNode, errorValue) then
-      FWorksheet.WriteErrorValue(cell, errorValue) else
-      FWorksheet.WriteText(cell, 'ERROR');
+      TsWorksheet(FWorksheet).WriteErrorValue(cell, errorValue) else
+      TsWorksheet(FWorksheet).WriteText(cell, 'ERROR');
   end else
   // (e) Text
   if (valueStr <> '') then
-    FWorksheet.WriteText(cell, valueStr);
+    TsWorksheet(FWorksheet).WriteText(cell, valueStr);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(Workbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadOpenDocReader.ReadFromStream(AStream: TStream;
@@ -2514,6 +2525,7 @@ var
   nodename: String;
   XMLStream: TStream;
   sheet: TsWorksheet;
+  sheetName: String;
   tablestyleName: String;
 
   function CreateXMLStream: TStream;
@@ -2600,7 +2612,8 @@ begin
         Continue;
       end;
 
-      FWorkSheet := FWorkbook.AddWorksheet(GetAttrValue(TableNode, 'table:name'), true);
+      sheetName := GetAttrValue(TableNode, 'table:name');
+      FWorkSheet := TsWorkbook(FWorkbook).AddWorksheet(sheetName, true);
       tablestyleName := GetAttrValue(TableNode, 'table:style-name');
       // Read protection
       ReadSheetProtection(TableNode, FWorksheet);
@@ -2611,10 +2624,13 @@ begin
       // Process each row inside the sheet and process each cell of the row
       ReadRowsAndCells(TableNode);
       // Read page layout
-      ReadPageLayout(StylesNode, GetAttrValue(TableNode, 'table:style-name'), FWorksheet.PageLayout);
+      ReadPageLayout(StylesNode, GetAttrValue(TableNode, 'table:style-name'),
+        (FWorksheet as TsWorksheet).PageLayout);
       // Repeated cols/rows already have been determined.
-      FWorksheet.PageLayout.SetRepeatedRows(FRepeatedRows.FirstIndex, FRepeatedRows.LastIndex);
-      FWorksheet.PageLayout.SetRepeatedCols(FRepeatedCols.FirstIndex, FRepeatedCols.LastIndex);
+      (FWorksheet as TsWorksheet).PageLayout.SetRepeatedRows(
+        FRepeatedRows.FirstIndex, FRepeatedRows.LastIndex);
+      (FWorksheet as TsWorksheet).PageLayout.SetRepeatedCols(
+        FRepeatedCols.FirstIndex, FRepeatedCols.LastIndex);
       // Read print ranges
       ReadPrintRanges(TableNode, FWorksheet);
       // Apply table style
@@ -2648,9 +2664,9 @@ begin
 
     // Active sheet
     if FActiveSheet <> '' then
-      sheet := FWorkbook.GetWorksheetByName(FActiveSheet) else
-      sheet := FWorkbook.GetWorksheetByIndex(0);
-    FWorkbook.SelectWorksheet(sheet);
+      sheet := (FWorkbook as TsWorkbook).GetWorksheetByName(FActiveSheet) else
+      sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(0);
+    (FWorkbook as TsWorkbook).SelectWorksheet(sheet);
 
   finally
     FreeAndNil(Doc);
@@ -2741,7 +2757,7 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
 
   // Apply style to cell
   // We do this already here because we need the cell font for rich-text
@@ -2750,9 +2766,9 @@ begin
   styleName := GetAttrValue(ACellNode, 'table:style-name');
   ApplyStyleToCell(cell, stylename);
   }
-  fmt := FWorkbook.GetPointerToCellFormat(cell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(cell^.FormatIndex);
   fntIndex := fmt^.FontIndex;
-  fnt := FWorkbook.GetFont(fntIndex);
+  fnt := (FWorkbook as TsWorkbook).GetFont(fntIndex);
 
   // Prepare reading of node data
   cellText := '';
@@ -2804,10 +2820,14 @@ begin
                   if rtFnt.Color = scNone then rtFnt.Color := fnt.Color;
                   if rtFnt.Position = fpNormal then rtFnt.Position := fnt.Position;
                   // Find this font in the workbook's font list
-                  rtfntIndex := FWorkbook.FindFont(rtFnt.FontName, rtFnt.Size, rtFnt.Style, rtFnt.Color, rtFnt.Position);
+                  rtfntIndex := (FWorkbook as TsWorkbook).FindFont(
+                    rtFnt.FontName, rtFnt.Size, rtFnt.Style, rtFnt.Color, rtFnt.Position
+                  );
                   // If not found add to font list
                   if rtfntIndex = -1 then
-                    rtfntIndex := FWorkbook.AddFont(rtFnt.FontName, rtFnt.Size, rtFnt.Style, rtFnt.Color, rtFnt.Position);
+                    rtfntIndex := (FWorkbook as TsWorkbook).AddFont(
+                      rtFnt.FontName, rtFnt.Size, rtFnt.Style, rtFnt.Color, rtFnt.Position
+                    );
                   // Use this font index in the rich-text parameter
                   SetLength(rtParams, Length(rtParams)+1);
                   rtParams[High(rtParams)].FirstIndex := UTF8Length(cellText) + 1;  // 1-based character index
@@ -2826,7 +2846,7 @@ begin
     childnode := childnode.NextSibling;
   end;
 
-  FWorkSheet.WriteText(cell, cellText, rtParams);
+  (FWorkSheet as TsWorksheet).WriteText(cell, cellText, rtParams);
   if hyperlink <> '' then
   begin
     // ODS sees relative paths relative to the internal own file structure
@@ -2834,12 +2854,12 @@ begin
     // the file.
     if pos('../', hyperlink) = 1 then
       Delete(hyperlink, 1, Length('../'));
-    FWorksheet.WriteHyperlink(cell, hyperlink);
-    FWorksheet.WriteFont(cell, HYPERLINK_FONTINDEX);
+    (FWorksheet as TsWorksheet).WriteHyperlink(cell, hyperlink);
+    (FWorksheet as TsWorksheet).WriteFont(cell, HYPERLINK_FONTINDEX);
   end;
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadOpenDocReader.ReadNumber(ARow, ACol: Cardinal;
@@ -2858,17 +2878,17 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
 
   Value := GetAttrValue(ACellNode,'office:value');
   if UpperCase(Value)='1.#INF' then
-    FWorkSheet.WriteNumber(cell, 1.0/0.0)
+    (FWorkSheet as TsWorksheet).WriteNumber(cell, 1.0/0.0)
   else
   begin
     // Don't merge, or else we can't debug
     Str := GetAttrValue(ACellNode, 'office:value');
     lNumber := StrToFloat(Str, FPointSeparatorSettings);
-    FWorkSheet.WriteNumber(cell, lNumber);
+    (FWorkSheet as TsWorksheet).WriteNumber(cell, lNumber);
   end;
 
   ApplyStyleToCell(cell, AStyleIndex);
@@ -2876,8 +2896,8 @@ begin
   styleName := GetAttrValue(ACellNode, 'table:style-name');
   ApplyStyleToCell(cell, stylename);
   }
-  fmt := Workbook.GetPointerToCellFormat(cell^.FormatIndex);
-  numFmt := Workbook.GetNumberFormat(fmt^.NumberFormatIndex);
+  fmt := (Workbook as TsWorkbook).GetPointerToCellFormat(cell^.FormatIndex);
+  numFmt := (Workbook as TsWorkbook).GetNumberFormat(fmt^.NumberFormatIndex);
 
   // Sometimes date/time cells are stored as "float".
   // We convert them to date/time and also correct the date origin offset if
@@ -2899,11 +2919,11 @@ begin
     // Cell has TEXT format @ --> store number as text
     txtNode := ACellNode.FirstChild;
     if txtNode.NodeName = 'text:p' then
-      FWorksheet.WriteText(cell, GetNodeValue(txtNode));
+      (FWorksheet as TsWorksheet).WriteText(cell, GetNodeValue(txtNode));
   end;
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadOpenDocReader.ReadNumFormats(AStylesNode: TDOMNode);
@@ -3408,7 +3428,7 @@ begin
         memStream := TMemoryStream.Create;
         unzip.UnzipFile(fn, memStream);
         memstream.Position := 0;
-        FWorkbook.AddEmbeddedObj(memstream, ExtractFileName(fn));
+        (FWorkbook as TsWorkbook).AddEmbeddedObj(memstream, ExtractFileName(fn));
         memStream.Free;
       end;
     end;
@@ -3418,7 +3438,7 @@ begin
 end;
 
 procedure TsSpreadOpenDocReader.ReadPrintRanges(ATableNode: TDOMNode;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   L: TStringList;
   s, sheetname: String;
@@ -3487,7 +3507,7 @@ begin
         end;
       end;
       // Add found range to worksheet
-      ASheet.PageLayout.AddPrintRange(r1, c1, r2, c2);
+      (ASheet as TsWorksheet).PageLayout.AddPrintRange(r1, c1, r2, c2);
     end;
   finally
     L.Free;
@@ -3573,7 +3593,7 @@ begin
     rowsSpanned := 0;
 
   if (colsSpanned <> 0) or (rowsSpanned <> 0) then
-    FWorksheet.MergeCells(ARow, ACol, ARow + rowsSpanned, ACol + colsSpanned);
+    (FWorksheet as TsWorksheet).MergeCells(ARow, ACol, ARow + rowsSpanned, ACol + colsSpanned);
 
   s := GetAttrValue(ANode, 'table:number-columns-repeated');
   if s <> '' then
@@ -3623,7 +3643,7 @@ var
       rowHeight := rowStyle.RowHeight;    // in Workbook units (see ReadRowStyles)
       rowHeightType := rowStyle.RowHeightType;
     end else begin
-      rowHeight := FWorksheet.ReadDefaultRowHeight(FWorkbook.Units);
+      rowHeight := (FWorksheet as TsWorksheet).ReadDefaultRowHeight(FWorkbook.Units);
       rowHeightTYpe := rhtDefault;
     end;
 
@@ -3656,9 +3676,9 @@ var
            (col + colsRepeated >= LongInt(FLimitations.MaxColCount) - 10) and
            (row < FLimitations.MaxRowCount - 10) then
         begin
-          lRow := FWorksheet.GetRow(row);
+          lRow := (FWorksheet as TsWorksheet).GetRow(row);
           // Find first cell in row, all cells have the same format here.
-          cell := FWorksheet.FindNextCellInRow(row, 0);
+          cell := (FWorksheet as TsWorksheet).FindNextCellInRow(row, 0);
           if cell <> nil then
             // Cell found --> copy its format index to cell record
             lRow^.FormatIndex := cell^.FormatIndex
@@ -3678,10 +3698,10 @@ var
           // specification limit.
           // React some columns earlier because the added column range is
           // sometimes split into two parts.
-          cell := FWorksheet.FindCell(row, col);
+          cell := (FWorksheet as TsWorksheet).FindCell(row, col);
           if cell <> nil then
             for i:=1 to colsRepeated-1 do begin
-              cell := FWorksheet.CopyCell(row, col, row, col+i);
+              cell := TsWorksheet(FWorksheet).CopyCell(row, col, row, col+i);
               styleIndex := ExtractFormatIndexFromStyle(cellStyleName, col+i);
               ApplyStyleToCell(cell, styleIndex);
             end;
@@ -3712,7 +3732,7 @@ var
     // into two parts.
     if row + rowsRepeated < LongInt(FLimitations.MaxRowCount) - 10 then
       for i:=1 to rowsRepeated do
-        FWorksheet.WriteRowHeight(row + i - 1, rowHeight, FWorkbook.Units, rowHeightType);
+        TsWorksheet(FWorksheet).WriteRowHeight(row + i - 1, rowHeight, FWorkbook.Units, rowHeightType);
 
     // Prepare checking of column format
     if GetRowFormat then begin
@@ -3720,7 +3740,7 @@ var
       if isFirstRow then begin
         SetLength(colFmt, col);
         for col:=0 to High(colFmt) do begin
-          cell := FWorksheet.FindCell(row, col);
+          cell := TsWorksheet(FWorksheet).FindCell(row, col);
           if cell <> nil then
             colFmt[col] := cell^.FormatIndex
           else begin
@@ -3735,7 +3755,7 @@ var
         // have a column format.
         for col:=0 to High(colFmt) do begin
           if colFmt[col] > -1 then begin
-            cell := FWorksheet.FindCell(row, col);
+            cell := TsWorksheet(FWorksheet).FindCell(row, col);
             if ((cell <> nil) and (cell^.FormatIndex <> colFmt[col])) then
               colFmt[col] := -1;
           end;
@@ -3791,7 +3811,7 @@ begin
   if not PrintRowMode and (row > FLimitations.MaxRowCount-10) then begin
     for c := 0 to High(colFmt) do
       if colFmt[c] > 0 then
-        FWorksheet.WriteColFormatIndex(c, colFmt[c]);
+        (FWorksheet as TsWorksheet).WriteColFormatIndex(c, colFmt[c]);
   end;
 end;
 
@@ -3816,7 +3836,7 @@ begin
     begin
       s := GetAttrValue(styleChildNode, 'style:row-height');
       if s <> '' then
-        rowHeight := FWorkbook.ConvertUnits(HTMLLengthStrToPts(s), suPoints, FWorkbook.Units);
+        rowHeight := TsWorkbook(FWorkbook).ConvertUnits(HTMLLengthStrToPts(s), suPoints, FWorkbook.Units);
         // convert to workbook units
       s := GetAttrValue(styleChildNode, 'style:use-optimal-row-height');
       if s = 'true' then
@@ -3899,7 +3919,7 @@ begin
                     if tblName <> '' then
                     begin
                       hsm := 0; vsm := 0;
-                      sheet := Workbook.GetWorksheetByName(tblName);
+                      sheet := TsWorkbook(Workbook).GetWorksheetByName(tblName);
                       if sheet <> nil then
                       begin
                         node := cfgTableItemNode.FirstChild;
@@ -3952,9 +3972,9 @@ begin
 
   { Now let's apply the showGrid and showHeader values to all sheets - they
     are document-wide settings (although there is a ShowGrid in the Tables node) }
-  for i:=0 to Workbook.GetWorksheetCount-1 do
+  for i:=0 to (Workbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
+    sheet := TsWorkbook(Workbook).GetWorksheetByIndex(i);
     if not showGrid then sheet.Options := sheet.Options - [soShowGridLines];
     if not showHeaders then sheet.Options := sheet.Options - [soShowHeaders];
   end;
@@ -4001,9 +4021,11 @@ begin
             href := GetAttrValue(childShapeNode, 'xlink:href');
             if href <> '' then
             begin
-              idx := FWorkbook.FindEmbeddedObj(ExtractFileName(href));
-              FWorksheet.CalcImageCell(idx, x, y, w, h, r, c, dr, dc, sx, sy);
-              FWorksheet.WriteImage(r, c, idx, dc, dr, sx, sy);    // order of dc and dr is correct!
+              idx := TsWorkbook(FWorkbook).FindEmbeddedObj(ExtractFileName(href));
+              with FWorksheet as TsWorksheet do begin
+                CalcImageCell(idx, x, y, w, h, r, c, dr, dc, sx, sy);
+                WriteImage(r, c, idx, dc, dr, sx, sy);    // order of dc and dr is correct!
+              end;
             end;
             childShapeNode := childShapeNode.NextSibling;
           end;
@@ -4016,7 +4038,7 @@ begin
 end;
 
 procedure TsSpreadOpenDocReader.ReadSheetProtection(ANode: TDOMNode;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   s: String;
   sp: TsWorksheetProtections;
@@ -4050,15 +4072,17 @@ begin
       end;
       childNode := childNode.NextSibling;
     end;
-    ASheet.Protection := sp;
-    ASheet.Protect(true);
+    with ASheet as TsWorksheet do begin
+      Protection := sp;
+      Protect(true);
+    end;
 
     InitCryptoInfo(cinfo);
     cinfo.PasswordHash := GetAttrValue(ANode, 'table:protection-key');
     cinfo.Algorithm := StrToAlgorithm(GetAttrValue(ANode, 'table:protection-key-digest-algorithm'));
-    ASheet.CryptoInfo := cinfo;
+    (ASheet as TsWorksheet).CryptoInfo := cinfo;
   end else
-    ASheet.Protect(false);
+    (ASheet as TsWorksheet).Protect(false);
 end;
 
 procedure TsSpreadOpenDocReader.ReadStyles(AStylesNode: TDOMNode);
@@ -4187,7 +4211,7 @@ begin
       if family = 'table-cell' then begin
         InitFormatRecord(fmt);
         fmt.Name := 'DefaultStyle';
-        fnt := FWorkbook.GetFont(fmt.FontIndex);
+        fnt := (FWorkbook as TsWorkbook).GetFont(fmt.FontIndex);
         fntName := fnt.FontName;
         fntSize := fnt.Size;
         fntStyle := fnt.Style;
@@ -4207,9 +4231,9 @@ begin
             // not used;
           styleChildNode := styleChildNode.nextSibling;
         end;
-        fmt.FontIndex := FWorkbook.FindFont(fntName, fntSize, fntStyle, fntColor, fntPos);
+        fmt.FontIndex := TsWorkbook(FWorkbook).FindFont(fntName, fntSize, fntStyle, fntColor, fntPos);
         if fmt.FontIndex = -1 then
-          fmt.FontIndex := FWorkbook.AddFont(fntname, fntsize, fntstyle, fntColor, fntPos);
+          fmt.FontIndex := TsWorkbook(FWorkbook).AddFont(fntname, fntsize, fntstyle, fntColor, fntPos);
         if fmt.FontIndex > 0 then
           Include(fmt.UsedFormattingFields, uffFont);
         FCellFormatList.Add(fmt);
@@ -4253,7 +4277,7 @@ begin
         end;
         fmt.Name := styleName;
 
-        fnt := FWorkbook.GetFont(fmt.FontIndex);
+        fnt := (Workbook as TsWorkbook).GetFont(fmt.FontIndex);
         fntName := fnt.FontName;
         fntSize := fnt.Size;
         fntStyle := fnt.Style;
@@ -4266,8 +4290,8 @@ begin
         if numFmtIndex = -1 then numFmtIndex := numFmtIndexDefault;
         numFmtStr := NumFormatList[numFmtIndex];
         numFmtStr := Copy(numFmtStr, pos(':', numFmtStr)+1, Length(numFmtStr));
-        fmt.NumberFormatIndex := Workbook.AddNumberFormat(numFmtStr);
-        numFmtParams := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+        fmt.NumberFormatIndex := (Workbook as TsWorkbook).AddNumberFormat(numFmtStr);
+        numFmtParams := (Workbook as TsWorkbook).GetNumberFormat(fmt.NumberFormatIndex);
         if numFmtParams <> nil then begin
           fmt.NumberFormat := numFmtParams.NumFormat;
           fmt.NumberFormatStr := numFmtStr;
@@ -4283,20 +4307,20 @@ begin
             ReadFont(styleChildNode, fntName, fntSize, fntStyle, fntColor, fntPos);
             if SameText(stylename, 'Default') then
             begin
-              FWorkbook.ReplaceFont(DEFAULT_FONTINDEX, fntName, fntSize, fntStyle, fntColor, fntPos);
+              TsWorkbook(FWorkbook).ReplaceFont(DEFAULT_FONTINDEX, fntName, fntSize, fntStyle, fntColor, fntPos);
               fmt.FontIndex := DEFAULT_FONTINDEX;
               //fntIndex := ReadFont(styleChildNode, DEFAULT_FONTINDEX)
             end else
             if SameText(stylename, 'Excel_20_Built-in_20_Hyperlink') then
             begin
-              FWorkbook.ReplaceFont(HYPERLINK_FONTINDEX, fntName, fntSize, fntStyle, fntColor, fntPos);
+              TsWorkbook(FWorkbook).ReplaceFont(HYPERLINK_FONTINDEX, fntName, fntSize, fntStyle, fntColor, fntPos);
               fmt.FontIndex := HYPERLINK_FONTINDEX;
               //fntIndex := ReadFont(styleChildNode, HYPERLINK_FONTINDEX)
             end else
             begin
-              fmt.FontIndex := FWorkbook.FindFont(fntName, fntSize, fntStyle, fntColor, fntPos);
+              fmt.FontIndex := TsWorkbook(FWorkbook).FindFont(fntName, fntSize, fntStyle, fntColor, fntPos);
               if fmt.FontIndex = -1 then
-                fmt.FontIndex := FWorkbook.AddFont(fntName, fntSize, fntStyle, fntColor, fntPos);
+                fmt.FontIndex := TsWorkbook(FWorkbook).AddFont(fntName, fntSize, fntStyle, fntColor, fntPos);
             end;
             if fmt.FontIndex > 0 then
               Include(fmt.UsedFormattingFields, uffFont);
@@ -4599,7 +4623,7 @@ begin
       if APageLayout.HeaderImages[sct].Index > -1 then
       begin
         img := APageLayout.HeaderImages[sct];
-        ext := GetImageTypeExt(FWorkbook.GetEmbeddedObj(img.Index).ImageType);
+        ext := GetImageTypeExt(TsWorkbook(FWorkbook).GetEmbeddedObj(img.Index).ImageType);
         AHeader := Format('%d.%s', [img.Index+1, ext]);
         break;
       end;
@@ -4607,7 +4631,7 @@ begin
       if APageLayout.FooterImages[sct].Index > -1 then
       begin
         img := APageLayout.FooterImages[sct];
-        ext := GetImageTypeExt(FWorkbook.GetEmbeddedObj(img.Index).Imagetype);
+        ext := GetImageTypeExt(TsWorkbook(FWorkbook).GetEmbeddedObj(img.Index).Imagetype);
         AFooter := Format('%d.%s', [img.Index+1, ext]);
         break;
       end;
@@ -4692,14 +4716,14 @@ begin
   { At first, add the default column width }
   colStyle := TColumnStyleData.Create;
   colStyle.Name := 'co1';
-  colStyle.ColWidth := FWorkbook.ConvertUnits(12, suChars, FWorkbook.Units);
+  colStyle.ColWidth := TsWorkbook(Workbook).ConvertUnits(12, suChars, FWorkbook.Units);
   FColumnStyleList.Add(colStyle);
 
   { Then iterate through all sheets and all columns and store the unique
     column widths in the FColumnStyleList. }
-  for i:=0 to Workbook.GetWorksheetCount-1 do
+  for i:=0 to (Workbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
+    sheet := TsWorkbook(Workbook).GetWorksheetByIndex(i);
     for c := 0 to sheet.Cols.Count-1 do
     begin
       col := PCol(sheet.Cols[c]);
@@ -4775,12 +4799,14 @@ var
   defFnt: TsHeaderFooterFont;
   i: Integer;
   sheet: TsWorksheet;
+  book: TsWorkbook;
 begin
-  defFnt := TsHeaderFooterFont.Create(Workbook.GetDefaultFont);
+  book := FWorkbook as TsWorkbook;
+  defFnt := TsHeaderFooterFont.Create(book.GetDefaultFont);
   try
-    for i:=0 to Workbook.GetWorksheetCount-1 do
+    for i:=0 to book.GetWorksheetCount-1 do
     begin
-      sheet := Workbook.GetWorksheetByIndex(i);
+      sheet := book.GetWorksheetByIndex(i);
       AddFontsOfHeaderFooter(sheet.pageLayout.Headers[1], defFnt);
       AddFontsOfHeaderFooter(sheet.PageLayout.Headers[2], defFnt);
       AddFontsOfHeaderFooter(sheet.PageLayout.Footers[1], defFnt);
@@ -4802,9 +4828,9 @@ var
   nfparams: TsNumFormatParams;
 begin
   // The default format has already been added.
-  for i:=0 to Workbook.GetNumberFormatCount - 1 do
+  for i:=0 to (Workbook as TsWorkbook).GetNumberFormatCount - 1 do
   begin
-    nfParams := Workbook.GetNumberFormat(i);
+    nfParams := TsWorkbook(Workbook).GetNumberFormat(i);
     if nfParams <> nil then
       FNumFormatList.Add(Format('N%d:%s', [FMT_BASE+i, nfParams.NumFormatStr]));
   end;
@@ -4818,18 +4844,20 @@ var
   found: Boolean;
   rowstyle: TRowStyleData;
   h: Double;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
   { At first, add the default row height }
   { Initially, row height units will be the same as in the workbook }
   rowStyle := TRowStyleData.Create;
   rowStyle.Name := 'ro1';
-  rowStyle.RowHeight := FWorkbook.ConvertUnits(15, suPoints, FWorkbook.Units);
+  rowStyle.RowHeight := book.ConvertUnits(15, suPoints, FWorkbook.Units);
   rowStyle.RowHeightType := rhtAuto;
   FRowStyleList.Add(rowStyle);
 
-  for i:=0 to Workbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i);
     for r:=0 to sheet.GetLastRowIndex do
     begin
       row := sheet.FindRow(r);
@@ -4878,6 +4906,7 @@ var
   i: Integer;
   sheet: TsWorksheet;
   fnt: TXMLHeaderFooterFont;
+  book: TsWorkbook;
 
 begin
   AppendToStream(AStream,
@@ -4912,8 +4941,10 @@ begin
 
       '</style:page-layout>');
 
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+  book := TsWorkbook(FWorkbook);
+
+  for i:=0 to book.GetWorksheetCount-1 do begin
+    sheet := book.GetWorksheetByIndex(i);
     AppendToStream(AStream,
       WritePageLayoutXMLAsString('Mpm' + IntToStr(3+i), sheet.PageLayout));
   end;
@@ -4954,9 +4985,9 @@ begin
       '<manifest:file-entry manifest:media-type="text/xml" manifest:full-path="meta.xml" />');
   AppendToStream(FSMetaInfManifest,
       '<manifest:file-entry manifest:media-type="text/xml" manifest:full-path="settings.xml" />');
-  for i:=0 to FWorkbook.GetEmbeddedObjCount-1 do
+  for i:=0 to (FWorkbook as TsWorkbook).GetEmbeddedObjCount-1 do
   begin
-    embObj := FWorkbook.GetEmbeddedObj(i);
+    embObj := TsWorkbook(FWorkbook).GetEmbeddedObj(i);
     imgtype := embObj.ImageType;
     if imgtype = itUnknown then
       continue;
@@ -5004,9 +5035,9 @@ var
   embName: String;
   ext: String;
 begin
-  for i:=0 to FWorkbook.GetEmbeddedObjCount-1 do
+  for i:=0 to (FWorkbook as TsWorkbook).GetEmbeddedObjCount-1 do
   begin
-    embObj := FWorkbook.GetEmbeddedObj(i);
+    embObj := (FWorkbook as TsWorkbook).GetEmbeddedObj(i);
     // The original ods files have a very long, ranomd, unique (?) filename.
     // Tests show that a simple, unique, increasing number works as well.
     ext := GetImageTypeExt(embObj.ImageType);
@@ -5023,7 +5054,10 @@ var
   sheet: TsWorksheet;
   actSheet: String;
   zoomvalue: String;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   // Open/LibreOffice allow to change showGrid and showHeaders only globally.
   // As a compromise, we check whether there is at least one page with these
   // settings off. Then we assume it to be valid also for the other sheets.
@@ -5031,10 +5065,10 @@ begin
   showHeaders := true;
   actSheet := 'Table1';
   zoomValue := '100';
-  for i:=0 to Workbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
-    if sheet = Workbook.ActiveWorksheet then
+    sheet := book.GetWorksheetByIndex(i);
+    if sheet = book.ActiveWorksheet then
       actSheet := UTF8TextToXMLText(sheet.Name);
     if not (soShowGridLines in sheet.Options) then showGrid := false;
     if not (soShowHeaders in sheet.Options) then showHeaders := false;
@@ -5098,7 +5132,7 @@ begin
         '<style:style style:name="Default" style:family="table-cell">',
            WriteDefaultFontXMLAsString,
         '</style:style>');
-  if FWorkbook.HasEmbeddedSheetImages then
+  if (FWorkbook as TsWorkbook).HasEmbeddedSheetImages then
     AppendToStream(FSStyles,
         '<style:default-style style:family="graphic">',
           WriteDefaultGraphicStyleXMLAsString,
@@ -5212,7 +5246,7 @@ begin
         '<office:spreadsheet' + WriteDocumentProtectionXMLAsString + '>');
 
   // Write all worksheets
-  for i := 0 to Workbook.GetWorksheetCount - 1 do
+  for i := 0 to (Workbook as TsWorkbook).GetWorksheetCount - 1 do
     WriteWorksheet(FSContent, i);
 
   AppendToStream(FSContent,
@@ -5225,12 +5259,12 @@ end;
 procedure TsSpreadOpenDocWriter.WriteWorksheet(AStream: TStream;
   ASheetIndex: Integer);
 begin
-  FWorksheet := FWorkbook.GetWorksheetByIndex(ASheetIndex);
+  FWorksheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(ASheetIndex);
 
   // Buffer the information whether the worksheet contains column or row formats
   // Needed for writing rows and cells
-  FHasColFormats := FWorksheet.HasColFormats;
-  FHasRowFormats := FWorksheet.HasRowFormats;
+  FHasColFormats := (FWorksheet as TsWorksheet).HasColFormats;
+  FHasRowFormats := (FWorksheet as TsWorksheet).HasRowFormats;
 
   // Header
   AppendToStream(AStream, Format(
@@ -5274,14 +5308,14 @@ var
   fmt: TsCellFormat;
   nfParams: TsNumFormatParams;
 begin
-  for i := 0 to FWorkbook.GetNumCellFormats - 1 do
+  for i := 0 to (FWorkbook as TsWorkbook).GetNumCellFormats - 1 do
   begin
-    fmt := FWorkbook.GetCellFormat(i);
+    fmt := TsWorkbook(FWorkbook).GetCellFormat(i);
     nfs := '';
     nfidx := fmt.NumberFormatIndex;
     if nfidx <> -1 then
     begin
-      nfParams := FWorkbook.GetNumberFormat(nfidx);
+      nfParams := TsWorkbook(FWorkbook).GetNumberFormat(nfidx);
       if nfParams <> nil then
       begin
         nfs := nfParams.NumFormatStr;
@@ -5363,7 +5397,7 @@ begin
     // Column width
     AppendToStream(AStream, Format(
         '<style:table-column-properties style:column-width="%.3fmm" fo:break-before="auto"/>',
-          [FWorkbook.ConvertUnits(colStyle.ColWidth, FWorkbook.Units, suMillimeters)],
+          [TsWorkbook(FWorkbook).ConvertUnits(colStyle.ColWidth, FWorkbook.Units, suMillimeters)],
           FPointSeparatorSettings));
 
     // End
@@ -5373,7 +5407,7 @@ begin
 end;
 
 procedure TsSpreadOpenDocWriter.WriteColumns(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   lastCol: Integer;
   c, k: Integer;
@@ -5383,11 +5417,12 @@ var
   colsRepeatedStr: String;
   firstRepeatedPrintCol, lastRepeatedPrintCol: Longint;
   headerCols: Boolean;
+  sheet: TsWorksheet absolute ASheet;
 begin
 //  widthMultiplier := Workbook.GetFont(0).Size / 2;
-  lastCol := ASheet.GetLastColIndex;
-  firstRepeatedPrintCol := longInt(ASheet.PageLayout.RepeatedCols.FirstIndex);
-  lastRepeatedPrintCol := longint(ASheet.PageLayout.RepeatedCols.LastIndex);
+  lastCol := sheet.GetLastColIndex;
+  firstRepeatedPrintCol := longInt(sheet.PageLayout.RepeatedCols.FirstIndex);
+  lastRepeatedPrintCol := longint(sheet.PageLayout.RepeatedCols.LastIndex);
   if (firstRepeatedPrintCol <> Longint(UNASSIGNED_ROW_COL_INDEX)) and
      (lastRepeatedPrintCol = LongInt(UNASSIGNED_ROW_COL_INDEX))
   then
@@ -5397,7 +5432,7 @@ begin
   c := 0;
   while (c <= lastCol) do
   begin
-    w := ASheet.GetColWidth(c, FWorkbook.Units);
+    w := sheet.GetColWidth(c, FWorkbook.Units);
 
     if (c = firstRepeatedPrintCol) then
     begin
@@ -5425,7 +5460,7 @@ begin
     if headerCols then
       while (k <= lastCol) and (k <= lastRepeatedPrintCol) do
       begin
-        if ASheet.GetColWidth(k, FWorkbook.Units) = w then
+        if sheet.GetColWidth(k, FWorkbook.Units) = w then
           inc(colsRepeated)
         else
           break;
@@ -5434,7 +5469,7 @@ begin
     else
       while (k <= lastCol) and (k < firstRepeatedPrintCol) do
       begin
-        if ASheet.GetColWidth(k, FWorkbook.Units) = w then
+        if sheet.GetColWidth(k, FWorkbook.Units) = w then
           inc(colsRepeated)
         else
           break;
@@ -5523,9 +5558,9 @@ begin
   L := TStringList.Create;
   try
     // First collect the font names from the workbook's FontList
-    for i:=0 to Workbook.GetFontCount-1 do
+    for i:=0 to TsWorkbook(Workbook).GetFontCount-1 do
     begin
-      fnt := Workbook.GetFont(i);
+      fnt := TsWorkbook(Workbook).GetFont(i);
       if (fnt <> nil) and (L.IndexOf(fnt.FontName) = -1) then
         L.Add(fnt.FontName);
     end;
@@ -5628,7 +5663,7 @@ var
 var
   sheetname: String;
 begin
-  defFnt := TsHeaderFooterFont.Create(Workbook.GetDefaultFont);
+  defFnt := TsHeaderFooterFont.Create((Workbook as TsWorkbook).GetDefaultFont);
 
   AppendToStream(AStream,
     '<office:master-styles>');
@@ -5641,8 +5676,8 @@ begin
         '<style:footer-left style:display="false" />' +
       '</style:master-page>');
 
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+  for i:=0 to (FWorkbook as TsWorkbook).GetWorksheetCount-1 do begin
+    sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(i);
     sheetname := UTF8TextToXMLText(sheet.name);
     AppendToStream(AStream,
       MasterPageAsString('PageStyle_5f_' + sheetName, 'PageStyle_' + sheetname,
@@ -5661,20 +5696,21 @@ end;
  </table:named-expressions>}
 
 procedure TsSpreadOpenDocWriter.WriteNamedExpressions(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   stotal, srng, sheetname: String;
   j: Integer;
   prng: TsCellRange;
+  sheet: TsWorksheet absolute ASheet;
 begin
   sheetname := UTF8TextToXMLText(ASheet.Name);
   stotal := '';
 
   // Cell block of print range
   srng := '';
-  for j := 0 to ASheet.PageLayout.NumPrintRanges - 1 do
+  for j := 0 to sheet.PageLayout.NumPrintRanges - 1 do
   begin
-    prng := ASheet.PageLayout.PrintRange[j];
+    prng := sheet.PageLayout.PrintRange[j];
     srng := srng + ';' + Format('[$%s.%s]', [
       sheetname, GetCellRangeString(prng.Row1, prng.Col1, prng.Row2, prng.Col2, [])
     ]);
@@ -5693,38 +5729,38 @@ begin
   {
   // repeated columns ...
   srng := '';
-  if ASheet.PageLayout.RepeatedCols.FirstIndex <> UNASSIGNED_ROW_COL_INDEX then
+  if sheet.PageLayout.RepeatedCols.FirstIndex <> UNASSIGNED_ROW_COL_INDEX then
   begin
-    if ASheet.PageLayout.RepeatedCols.LastIndex = UNASSIGNED_ROW_COL_INDEX then
+    if sheet.PageLayout.RepeatedCols.LastIndex = UNASSIGNED_ROW_COL_INDEX then
       srng := srng + ';' + Format('[$%s.$%s]',
-        [ASheet.Name, GetColString(ASheet.pageLayout.RepeatedCols.FirstIndex)]
+        [sheet.Name, GetColString(sheet.pageLayout.RepeatedCols.FirstIndex)]
       )
     else
       srng := srng + ';' + Format('[$%s.$%s1:.$%s1048576]', [      // [$Sheet1.$A$1:.$D$1048576]
-        ASheet.Name,
-        GetColString(ASheet.Pagelayout.RepeatedCols.FirstIndex),
-        GetColString(ASheet.PageLayout.RepeatedCols.LastIndex)
+        sheet.Name,
+        GetColString(sheet.Pagelayout.RepeatedCols.FirstIndex),
+        GetColString(sheet.PageLayout.RepeatedCols.LastIndex)
       ]);
   end;
   // ... and repeated rows
-  if ASheet.PageLayout.RepeatedRows.FirstIndex <> UNASSIGNED_ROW_COL_INDEX then
+  if sheet.PageLayout.RepeatedRows.FirstIndex <> UNASSIGNED_ROW_COL_INDEX then
   begin
-    if ASheet.PageLayout.RepeatedRows.LastIndex = UNASSIGNED_ROW_COL_INDEX then
+    if sheet.PageLayout.RepeatedRows.LastIndex = UNASSIGNED_ROW_COL_INDEX then
       srng := srng + ';' + Format('[$%s.$%d]',
-        [ASheet.Name, ASheet.pageLayout.RepeatedRows.FirstIndex]
+        [sheet.Name, sheet.pageLayout.RepeatedRows.FirstIndex]
       )
     else
       srng := srng + ';' + Format('[$%s.$A$%d:.$AMJ$%d]', [              // [$Sheet1.$A$1:.$AMJ$2]"
-        ASheet.Name,
-        ASheet.Pagelayout.RepeatedRows.FirstIndex+1,
-        ASheet.PageLayout.RepeatedRows.LastIndex+1
+        sheet.Name,
+        sheet.Pagelayout.RepeatedRows.FirstIndex+1,
+        sheet.PageLayout.RepeatedRows.LastIndex+1
       ]);
   end;
   if srng <> '' then begin
     Delete(srng, 1,1);
     stotal := stotal + Format(
       '<table:named-expression table:name="_xlnm.Print_Titles" table:bases-cell-address="$%s.$A$1" table:expression="%s" />',
-      [ASheet.Name, srng]
+      [sheet.Name, srng]
     );
   end;
    }
@@ -5759,20 +5795,24 @@ begin
   end;
 end;
 
-procedure TsSpreadOpenDocWriter.WriteRowsAndCells(AStream: TStream; ASheet: TsWorksheet);
+procedure TsSpreadOpenDocWriter.WriteRowsAndCells(AStream: TStream;
+  ASheet: TsBasicWorksheet);
 var
   r: Integer;
   rowsRepeated: Integer;
   firstCol, firstRow, lastCol, lastRow: Cardinal;
   firstRepeatedPrintRow, lastRepeatedPrintRow: Integer;
   headerRows: Boolean;
+  sheet: TsWorksheet;
 begin
+  sheet := (ASheet as TsWorksheet);
+
   // some abbreviations...
   GetSheetDimensions(ASheet, firstRow, lastRow, firstCol, lastCol);
 
   headerRows := false;
-  firstRepeatedPrintRow := Integer(ASheet.PageLayout.RepeatedRows.FirstIndex);
-  lastRepeatedPrintRow := Integer(ASheet.PageLayout.RepeatedRows.LastIndex);
+  firstRepeatedPrintRow := Integer(sheet.PageLayout.RepeatedRows.FirstIndex);
+  lastRepeatedPrintRow := Integer(sheet.PageLayout.RepeatedRows.LastIndex);
   if (firstRepeatedPrintRow <> Integer(UNASSIGNED_ROW_COL_INDEX)) and
      (lastRepeatedPrintRow = Integer(UNASSIGNED_ROW_COL_INDEX))
   then
@@ -5787,7 +5827,7 @@ begin
     end;
 
     // Write rows
-    if ASheet.IsEmptyRow(r) then
+    if sheet.IsEmptyRow(r) then
       WriteEmptyRow(AStream, ASheet, r, firstCol, lastCol, lastRow, rowsRepeated)
     else begin
       WriteCellRow(AStream, ASheet, r, lastCol);
@@ -6041,7 +6081,7 @@ end;
 *)
 
 procedure TsSpreadOpenDocWriter.WriteCellRow(AStream: TStream;
-  ASheet: TsWorksheet; ARowIndex, ALastColIndex: Integer);
+  ASheet: TsBasicWorksheet; ARowIndex, ALastColIndex: Integer);
 var
   row: PRow;
   col: PCol;
@@ -6053,9 +6093,10 @@ var
   c, cc: integer;
   colsRepeated: Integer;
   fmtIndex: integer;
+  sheet: TsWorksheet absolute ASheet;
 begin
   // Get row
-  row := ASheet.FindRow(ARowIndex);
+  row := sheet.FindRow(ARowIndex);
 
   // Get style and height of row
   GetRowStyleAndHeight(ASheet, ARowIndex, stylename, h);
@@ -6065,18 +6106,18 @@ begin
     '<table:table-row table:style-name="%s">', [stylename]));
 
   // Find first cell or column in this row
-  cell := ASheet.Cells.GetFirstCellOfRow(ARowIndex);  // first cell
-  col := ASheet.FindFirstCol;   // left-most column
+  cell := sheet.Cells.GetFirstCellOfRow(ARowIndex);  // first cell
+  col := sheet.FindFirstCol;   // left-most column
   if col <> nil then
     firstcol := Min(col^.Col, cell^.Col) else
     firstcol := cell^.Col;
 
   // Find last cell or column in this row
-  cell := ASheet.Cells.GetlastCellOfRow(ARowIndex);
-  if ASheet.Cols.Count = 0 then
+  cell := sheet.Cells.GetlastCellOfRow(ARowIndex);
+  if sheet.Cols.Count = 0 then
     lastCol := cell^.Col
   else begin
-    col := ASheet.Cols[ASheet.Cols.Count-1];
+    col := sheet.Cols[sheet.Cols.Count-1];
     if col <> nil then
       lastcol := Max(col^.Col, cell^.Col) else
       lastCol := cell^.Col;
@@ -6091,11 +6132,11 @@ begin
   c := firstcol;
   while (c <= lastcol) do
   begin
-    cell := ASheet.FindCell(ARowIndex, c);
+    cell := sheet.FindCell(ARowIndex, c);
     if cell <> nil then
     begin
       // Belongs to merged block?
-      if not FWorksheet.IsMergeBase(cell) and FWorksheet.IsMerged(cell) then
+      if not sheet.IsMergeBase(cell) and sheet.IsMerged(cell) then
       // this means: all cells of a merged block except for the merge base
       begin
         AppendToStream(AStream,
@@ -6110,7 +6151,7 @@ begin
     end;
 
     // Column format
-    col := ASheet.FindCol(c);
+    col := sheet.FindCol(c);
     if (col <> nil) and (col^.FormatIndex > 0) then
     begin
       // row format has priority...
@@ -6126,10 +6167,10 @@ begin
     // Empty cell
     cc := c + 1;
     while (cc <= lastcol) do begin
-      cell := ASheet.FindCell(ARowIndex, cc);
+      cell := sheet.FindCell(ARowIndex, cc);
       if cell <> nil then
         break;
-      col := ASheet.FindCol(cc);
+      col := sheet.FindCol(cc);
       if (col <> nil) and (col^.FormatIndex > 0) then
         break;
       inc(cc);
@@ -6175,7 +6216,8 @@ end;
   handles row and column formats.
   If ALastRowIndex = -1 then the filler rows below the used sheet are written }
 procedure TsSpreadOpenDocWriter.WriteEmptyRow(AStream: TStream;
-  ASheet: TsWorksheet; ARowIndex, AFirstColIndex, ALastColIndex, ALastRowIndex: Integer;
+  ASheet: TsBasicWorksheet;
+  ARowIndex, AFirstColIndex, ALastColIndex, ALastRowIndex: Integer;
   out ARowsRepeated: Integer);
 var
   row: PRow;
@@ -6185,12 +6227,13 @@ var
   stylename: String;
   h, h1: Single;
   fmtIndex: Integer;
+  sheet: TsWorksheet absolute ASheet;
 begin
   // Get style and height of row
   GetRowStyleAndHeight(ASheet, ARowIndex, stylename, h);
 
   // Determine how often this row is repeated
-  row := ASheet.FindRow(ARowIndex);
+  row := sheet.FindRow(ARowIndex);
   // Rows with format are not repeated - too complicated...
   if (row <> nil) and (row^.FormatIndex > 0) then
     ARowsRepeated := 1
@@ -6200,12 +6243,12 @@ begin
     r := ARowIndex + 1;
     while r <= ALastRowIndex do
     begin
-      if not ASheet.IsEmptyRow(r) then
+      if not sheet.IsEmptyRow(r) then
         break;
-      row := ASheet.FindRow(r);
+      row := sheet.FindRow(r);
       if (row <> nil) and (row^.FormatIndex > 0) then
         break;
-      h1 := ASheet.GetRowHeight(r, FWorkbook.Units);
+      h1 := sheet.GetRowHeight(r, FWorkbook.Units);
       if not SameValue(h, h1, ROWHEIGHT_EPS) then
         break;
       inc(r);
@@ -6234,11 +6277,11 @@ begin
   r := ARowIndex;
   c := AFirstColIndex;
 
-  row := ASheet.FindRow(r);
+  row := sheet.FindRow(r);
   while (c <= ALastColIndex) do
   begin
     // Empty cell in a column with a column format
-    col := ASheet.FindCol(c);
+    col := sheet.FindCol(c);
     if (col <> nil) and (col^.FormatIndex > 0) then
     begin
       if (row <> nil) and (row^.FormatIndex > 0) then
@@ -6255,7 +6298,7 @@ begin
     cc := c + 1;
     while (cc <= ALastColIndex) do
     begin
-      col := ASheet.FindCol(cc);
+      col := sheet.FindCol(cc);
       if (col <> nil) and (col^.FormatIndex > 0) then
         break;
       inc(cc);
@@ -6293,7 +6336,7 @@ begin
     '</table:table-row>');
 end;
 
-procedure TsSpreadOpenDocWriter.GetRowStyleAndHeight(ASheet: TsWorksheet;
+procedure TsSpreadOpenDocWriter.GetRowStyleAndHeight(ASheet: TsBasicWorksheet;
   ARowIndex: Integer; out AStyleName: String; out AHeight: Single);
 var
   row: PRow;
@@ -6301,7 +6344,7 @@ var
   k: Integer;
 begin
   AStyleName := '';
-  row := ASheet.FindRow(ARowIndex);
+  row := (ASheet as TsWorksheet).FindRow(ARowIndex);
   if row <> nil then
   begin
     AHeight := row^.Height;    // row height in workbook units
@@ -6319,7 +6362,7 @@ begin
   end;
   if AStyleName = '' then begin
     AStyleName := 'ro1';   // "ro1" is default row record - see ListAllRowStyles
-    AHeight := ASheet.ReadDefaultRowHeight(FWorkbook.Units);
+    AHeight := (ASheet as TsWorksheet).ReadDefaultRowHeight(FWorkbook.Units);
   end;
 end;
 
@@ -6337,7 +6380,7 @@ begin
         '<style:table-row-properties style:row-height="%.3fmm" ' +
           'fo:break-before="auto" style:use-optimal-row-height="true"/>' +
       '</style:style>',
-      [FWorksheet.ReadDefaultRowHeight(suMillimeters)]
+      [(FWorksheet as TsWorksheet).ReadDefaultRowHeight(suMillimeters)]
     ));
     exit;
   end;
@@ -6353,7 +6396,7 @@ begin
     // Row height
     AppendToStream(AStream, Format(
       '<style:table-row-properties style:row-height="%.3fmm" ',
-        [FWorkbook.ConvertUnits(rowStyle.RowHeight, FWorkbook.Units, suMillimeters)],
+        [TsWorkbook(FWorkbook).ConvertUnits(rowStyle.RowHeight, FWorkbook.Units, suMillimeters)],
         FPointSeparatorSettings));
     AppendToStream(AStream, Format(
         'style:use-optimal-row-height="%s" ', [FALSE_TRUE[rowstyle.RowHeightType <> rhtCustom]]));
@@ -6367,7 +6410,7 @@ begin
 end;
 
 
-constructor TsSpreadOpenDocWriter.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadOpenDocWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -6455,27 +6498,29 @@ var
   comment: String;
   r1,c1,r2,c2: Cardinal;
   fmt: TsCellFormat;
+  sheet: TsWorksheet;
 begin
   Unused(ARow, ACol);
+  sheet := FWorksheet as TsWorksheet;
 
   // Hyperlink
-  if FWorksheet.HasHyperlink(ACell) then
+  if sheet.HasHyperlink(ACell) then
     FWorkbook.AddErrorMsg(rsODSHyperlinksOfTextCellsOnly, [GetCellString(ARow, ACol)]);
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString(sheet.ReadComment(ACell));
 
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if sheet.IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    sheet.FindMergedRange(ACell, r1, c1, r2, c2);
     rowsSpannedStr := Format(' table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     colsSpannedStr := Format(' table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     spannedStr := colsSpannedStr + rowsSpannedStr;
   end else
     spannedStr := '';
 
-  fmt := FWorkbook.GetCellFormat(ACell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetCellFormat(ACell^.FormatIndex);
   if (fmt.UsedFormattingFields <> []) then
     AppendToStream(AStream, Format(
       '<table:table-cell table:style-name="ce%d"%s>', [ACell^.FormatIndex, spannedStr]),
@@ -6508,19 +6553,19 @@ begin
 
   valType := 'boolean';
 
-  fmt := FWorkbook.GetCellFormat(ACell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetCellFormat(ACell^.FormatIndex);
   if fmt.UsedFormattingFields <> [] then
     lStyle := ' table:style-name="ce' + IntToStr(ACell^.FormatIndex) + '" '
   else
     lStyle := '';
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString((FWorksheet as TsWorksheet).ReadComment(ACell));
 
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if (FWorksheet as TsWorksheet).IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    (FWorksheet as TsWorksheet).FindMergedRange(ACell, r1, c1, r2, c2);
     rowsSpannedStr := Format('table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     colsSpannedStr := Format('table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     spannedStr := colsSpannedStr + ' ' + rowsSpannedStr;
@@ -6698,7 +6743,7 @@ function TsSpreadOpenDocWriter.WriteDefaultFontXMLAsString: String;
 var
   fnt: TsFont;
 begin
-  fnt := Workbook.GetDefaultFont;
+  fnt := (Workbook as TsWorkbook).GetDefaultFont;
   Result := Format(
     '<style:text-properties style:font-name="%s" fo:font-size="%.1fpt" />',
     [fnt.FontName, fnt.Size], FPointSeparatorSettings
@@ -6734,7 +6779,7 @@ var
 begin
   if bpLockStructure in Workbook.Protection then
   begin
-    cinfo := Workbook.CryptoInfo;
+    cinfo := (Workbook as TsWorkbook).CryptoInfo;
     if cinfo.PasswordHash <> '' then
       pwd := Format(' table:protection-key="%s"', [cinfo.PasswordHash])
     else
@@ -6760,22 +6805,25 @@ var
   spannedStr: String;
   valueStr: String;
   r1,c1,r2,c2: Cardinal;
+  sheet: TsWorksheet;
 begin
   Unused(ARow, ACol, AValue);
 
-  fmt := FWorkbook.GetPointerToCellFormat(ACell^.FormatIndex);
+  sheet := FWorksheet as TsWorksheet;
+
+  fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(ACell^.FormatIndex);
   if fmt^.UsedFormattingFields <> [] then
     lStyle := ' table:style-name="ce' + IntToStr(ACell^.FormatIndex) + '" '
   else
     lStyle := '';
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString(sheet.ReadComment(ACell));
 
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if sheet.IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    sheet.FindMergedRange(ACell, r1, c1, r2, c2);
     rowsSpannedStr := Format(' table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     colsSpannedStr := Format(' table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     spannedStr := colsSpannedStr + rowsSpannedStr;
@@ -6786,8 +6834,8 @@ begin
   valueStr := GetErrorValueStr(ACell^.ErrorValue);
 
   // Hyperlink
-  if FWorksheet.HasHyperlink(ACell) then
-    FWorkbook.AddErrorMsg(rsODSHyperlinksOfTextCellsOnly, [GetCellString(ARow, ACol)]);
+  if sheet.HasHyperlink(ACell) then
+    (FWorkbook as TsWorkbook).AddErrorMsg(rsODSHyperlinksOfTextCellsOnly, [GetCellString(ARow, ACol)]);
 
   // Write to stream
   AppendToStream(AStream, Format(
@@ -6822,7 +6870,7 @@ var
 begin
   Result := '';
 
-  defFnt := Workbook.GetDefaultFont;
+  defFnt := (Workbook as TsWorkbook).GetDefaultFont;
   if AFont = nil then AFont := defFnt;
 
   Result := Result + Format('style:font-name="%s" ', [AFont.FontName]);
@@ -6857,7 +6905,7 @@ function TsSpreadOpenDocWriter.WriteFontStyleXMLAsString(
 begin
   Result := '';
   if (uffFont in AFormat.UsedFormattingFields) then
-    Result := WriteFontStyleXMLAsString(Workbook.GetFont(AFormat.FontIndex));
+    Result := WriteFontStyleXMLAsString((Workbook as TsWorkbook).GetFont(AFormat.FontIndex));
 end;
 
 function TsSpreadOpenDocWriter.WriteHeaderFooterFontXMLAsString(
@@ -7038,21 +7086,23 @@ begin
     '</style:page-layout>';
 end;
 
-function TsSpreadOpenDocWriter.WritePrintRangesXMLAsString(ASheet: TsWorksheet): String;
+function TsSpreadOpenDocWriter.WritePrintRangesXMLAsString(
+  ASheet: TsBasicWorksheet): String;
 var
   i: Integer;
   rng: TsCellRange;
   sheetName: String;
+  sheet: TsWorksheet absolute ASheet;
 begin
   Result := '';
-  if ASheet.PageLayout.NumPrintRanges > 0 then
+  if sheet.PageLayout.NumPrintRanges > 0 then
   begin
-    for i := 0 to ASheet.PageLayout.NumPrintRanges - 1 do
+    for i := 0 to sheet.PageLayout.NumPrintRanges - 1 do
     begin
-      rng := ASheet.PageLayout.PrintRange[i];
+      rng := sheet.PageLayout.PrintRange[i];
       if pos(' ', ASheet.Name) > 0 then
-        sheetName := '&apos;' + UTF8TextToXMLText(ASheet.Name) + '&apos;' else
-        sheetname := UTF8TextToXMLText(ASheet.Name);
+        sheetName := '&apos;' + UTF8TextToXMLText(sheet.Name) + '&apos;' else
+        sheetname := UTF8TextToXMLText(sheet.Name);
       Result := Result + ' ' + Format('%s.%s:%s.%s', [
         sheetName, GetCellString(rng.Row1,rng.Col1),
         sheetName, GetCellString(rng.Row2,rng.Col2)
@@ -7067,19 +7117,20 @@ begin
 end;
 
 function TsSpreadOpenDocWriter.WriteSheetProtectionXMLAsString(
-  ASheet: TsWorksheet): String;
+  ASheet: TsBasicWorksheet): String;
 {table:protected="true" table:protection-key="h/jtkVcSX/xNqeBqe4ARrYClP+E=" table:protection-key-digest-algorithm="http://www.w3.org/2000/09/xmldsig#sha1"}
 var
   pwd: String;
   algo: String;
+  sheet: TsWorksheet absolute ASheet;
 begin
   Result := '';
   if ASheet.IsProtected then
   begin
-    if ASheet.CryptoInfo.PasswordHash <> '' then
-      pwd := ' table:protection-key="' + ASheet.CryptoInfo.PasswordHash + '"' else
+    if sheet.CryptoInfo.PasswordHash <> '' then
+      pwd := ' table:protection-key="' + sheet.CryptoInfo.PasswordHash + '"' else
       pwd := '';
-    algo := AlgorithmToStr(ASheet.CryptoInfo.Algorithm, auOpenDocument);
+    algo := AlgorithmToStr(sheet.CryptoInfo.Algorithm, auOpenDocument);
     if algo <> '' then
       algo := ' table:protection-key-digest-algorithm="%s"';
     Result := ' table:protected="true"' + pwd + algo;
@@ -7087,7 +7138,7 @@ begin
 end;
 
 function TsSpreadOpenDocWriter.WriteSheetProtectionDetailsXMLAsString(
-  ASheet: TsWorksheet): String;
+  ASheet: TsBasicWorksheet): String;
 // <loext:table-protection loext:select-unprotected-cells="true" />
 begin
   Result := '';
@@ -7102,7 +7153,7 @@ begin
 end;
 
 procedure TsSpreadOpenDocWriter.WriteShapes(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 {
 <table:shapes>
   <draw:frame draw:z-index="0" draw:name="Bild 1" draw:style-name="gr1" draw:text-style-name="P1"
@@ -7121,20 +7172,20 @@ var
   roffs1,coffs1, roffs2, coffs2: Double;
   x, y, w, h: Double;
 begin
-  if ASheet.GetImageCount = 0 then
+  if (ASheet as TsWorksheet).GetImageCount = 0 then
     exit;
 
   AppendToStream(AStream,
     '<table:shapes>');
 
-  for i:=0 to ASheet.GetImageCount-1 do
+  for i:=0 to (ASheet as TsWorksheet).GetImageCount-1 do
   begin
-    img := ASheet.GetImage(i);
-    imgType := FWorkbook.GetEmbeddedObj(img.Index).ImageType;
+    img := (ASheet as TsWorksheet).GetImage(i);
+    imgType := (FWorkbook as TsWorkbook).GetEmbeddedObj(img.Index).ImageType;
     if imgType = itUnknown then
       Continue;
 
-    ASheet.CalcImageExtent(i, false,   // not clear if UsePixels=false is correct. Not harmful at least
+    (ASheet as TsWorksheet).CalcImageExtent(i, false,  // not clear if UsePixels=false is correct. Not harmful at least
       r1, c1, r2, c2,
       roffs1, coffs1, roffs2, coffs2,  // mm
       x, y, w, h);                     // mm
@@ -7171,9 +7222,9 @@ var
   zoom: String;
 begin
   zoom := '100';
-  for i:=0 to Workbook.GetWorksheetCount-1 do
+  for i:=0 to (Workbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
+    sheet := (Workbook as TsWorkbook).GetWorksheetByIndex(i);
     sheetname := UTF8TextToXMLText(sheet.Name);
 
     AppendToStream(AStream,
@@ -7249,9 +7300,9 @@ var
   sheet: TsWorksheet;
   sheetname, bidi: String;
 begin
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do
+  for i:=0 to (FWorkbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(i);
     sheetname := UTF8TextToXMLText(sheet.Name);
     case sheet.BiDiMode of
       bdDefault: bidi := '';
@@ -7301,9 +7352,9 @@ var
   i: Integer;
 begin
   styleCounter := 0;
-  for i := 0 to FWorkbook.GetWorksheetCount-1 do
+  for i := 0 to (FWorkbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(i);
     for cell in sheet.Cells do
     begin
       if Length(cell^.RichTextParams) = 0 then
@@ -7312,7 +7363,7 @@ begin
       begin
         inc(styleCounter);
         stylename := Format('T%d', [stylecounter]);
-        fnt := FWorkbook.GetFont(rtp.FontIndex);
+        fnt := (FWorkbook as TsWorkbook).GetFont(rtp.FontIndex);
         FRichTextFontList.AddObject(stylename, fnt);
         fntStr := WriteFontStyleXMLAsString(fnt);
         AppendToStream(AStream,
@@ -7363,7 +7414,7 @@ begin
 end;
 
 procedure TsSpreadOpenDocWriter.WriteVirtualCells(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   r, c, cc: Cardinal;
   lCell: TCell;
@@ -7378,24 +7429,25 @@ var
   colsRepeated: Cardinal;
   colsRepeatedStr: String;
   lastCol, lastRow: Cardinal;
+  sheet: TsWorksheet absolute ASheet;
 begin
-  if ASheet.VirtualColCount = 0 then
+  if sheet.VirtualColCount = 0 then
     exit;
-  if ASheet.VirtualRowCount = 0 then
+  if sheet.VirtualRowCount = 0 then
     exit;
-  if not Assigned(ASheet.OnWriteCellData) then
+  if not Assigned(sheet.OnWriteCellData) then
     exit;
 
   // some abbreviations...
-  lastCol := LongInt(ASheet.VirtualColCount) - 1;
-  lastRow := LongInt(ASheet.VirtualRowCount) - 1;
+  lastCol := LongInt(sheet.VirtualColCount) - 1;
+  lastRow := LongInt(sheet.VirtualRowCount) - 1;
 
   rowsRepeated := 1;
   r := 0;
   while (r <= lastRow) do
   begin
     // Look for the row style of the current row (r)
-    row := ASheet.FindRow(r);
+    row := sheet.FindRow(r);
     if row = nil then
       styleName := 'ro1'
     else
@@ -7435,7 +7487,7 @@ begin
       value := varNull;
       styleCell := nil;
 
-      ASheet.OnWriteCellData(ASheet, r, c, value, styleCell);
+      sheet.OnWriteCellData(sheet, r, c, value, styleCell);
 
       if VarIsNull(value) then
       begin
@@ -7446,7 +7498,7 @@ begin
           InitCell(ASheet, r, cc, lCell);
           value := varNull;
           styleCell := nil;
-          ASheet.OnWriteCellData(ASheet, r, cc, value, styleCell);
+          sheet.OnWriteCellData(sheet, r, cc, value, styleCell);
           if not VarIsNull(value) then
             break;
           inc(cc);
@@ -7524,24 +7576,27 @@ var
   r1,c1,r2,c2: Cardinal;
   fmt: TsCellFormat;
   ignoreFormulas: Boolean;
+  sheet: TsWorksheet;
 begin
   Unused(ARow, ACol);
   ignoreFormulas := (boIgnoreFormulas in FWorkbook.Options);
 
+  sheet := FWorksheet as TsWorksheet;
+
   // Style
-  fmt := FWorkbook.GetCellFormat(ACell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetCellFormat(ACell^.FormatIndex);
   if fmt.UsedFormattingFields <> [] then
     lStyle := ' table:style-name="ce' + IntToStr(ACell^.FormatIndex) + '" '
   else
     lStyle := '';
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString(sheet.ReadComment(ACell));
 
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if sheet.IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    sheet.FindMergedRange(ACell, r1, c1, r2, c2);
     rowsSpannedStr := Format(' table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     colsSpannedStr := Format(' table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     spannedStr := colsSpannedStr + rowsSpannedStr;
@@ -7549,7 +7604,7 @@ begin
     spannedStr := '';
 
   // Hyperlink
-  if FWorksheet.HasHyperlink(ACell) then
+  if sheet.HasHyperlink(ACell) then
     FWorkbook.AddErrorMsg(rsODSHyperlinksOfTextCellsOnly, [GetCellString(ARow, ACol)]);
 
   // Formula string
@@ -7624,7 +7679,7 @@ begin
 
   { We are writing a very rudimentary formula here without result and result
     data type. Seems to work... }
-  if not ignoreFormulas or (FWorksheet.GetCalcState(ACell) = csCalculated) then
+  if not ignoreFormulas or (sheet.GetCalcState(ACell) = csCalculated) then
     AppendToStream(AStream, Format(
       '<table:table-cell table:formula="%s" office:value-type="%s"%s%s%s>' +
         comment +
@@ -7669,6 +7724,7 @@ var
   rtParam: TsRichTextParam;
   wideStr, txt: WideString;
   ch: WideChar;
+  sheet: TsWorksheet;
 
   function IsNewLine(var idx: Integer): Boolean;
   begin
@@ -7710,20 +7766,22 @@ var
 begin
   Unused(ARow, ACol);
 
+  sheet := FWorksheet as TsWorksheet;
+
   // Style
-  fmt := FWorkbook.GetCellFormat(ACell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetCellFormat(ACell^.FormatIndex);
   if fmt.UsedFormattingFields <> [] then
     lStyle := ' table:style-name="ce' + IntToStr(ACell^.FormatIndex) + '"'
   else
     lStyle := '';
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString(sheet.ReadComment(ACell));
 
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if sheet.IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    sheet.FindMergedRange(ACell, r1, c1, r2, c2);
     rowsSpannedStr := Format(' table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     colsSpannedStr := Format(' table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     spannedStr := colsSpannedStr + rowsSpannedStr;
@@ -7739,9 +7797,9 @@ begin
     ]);
 
   // Hyperlink?
-  if FWorksheet.HasHyperlink(ACell) then
+  if sheet.HasHyperlink(ACell) then
   begin
-    hyperlink := FWorksheet.FindHyperlink(ACell);
+    hyperlink := sheet.FindHyperlink(ACell);
     SplitHyperlink(hyperlink^.Target, target, bookmark);
 
     if (target <> '') and (pos('file:', target) = 0) then
@@ -7816,7 +7874,7 @@ begin
       begin
         // Formatted parts of the string according the RichTextParams
         rtParam := ACell^.RichTextParams[i];
-        fnt := FWorkbook.GetFont(rtParam.FontIndex);
+        fnt := (FWorkbook as TsWorkbook).GetFont(rtParam.FontIndex);
         fntidx := FRichTextFontList.IndexOfObject(fnt);
         fntName := FRichTextFontList[fntIdx];
         if i < High(ACell^.RichTextParams) then
@@ -7867,10 +7925,10 @@ begin
   Unused(ARow, ACol);
 
   valType := 'float';
-  fmt := FWorkbook.GetCellFormat(ACell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetCellFormat(ACell^.FormatIndex);
   if fmt.UsedFormattingFields <> [] then
   begin
-    numFmt := FWorkbook.GetNumberFormat(fmt.NumberFormatIndex);
+    numFmt := (FWorkbook as TsWorkbook).GetNumberFormat(fmt.NumberFormatIndex);
     if (numFmt <> nil) then begin
       if (Length(numFmt.Sections) > 1) and (AValue < 0) then
         nfSection := numFmt.Sections[1]
@@ -7890,12 +7948,12 @@ begin
     lStyle := '';
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString((FWorksheet as TsWorksheet).ReadComment(ACell));
 
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if (FWorksheet as TsWorksheet).IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    (FWorksheet as TsWorksheet).FindMergedRange(ACell, r1, c1, r2, c2);
     rowsSpannedStr := Format(' table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     colsSpannedStr := Format(' table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     spannedStr := colsSpannedStr + rowsSpannedStr;
@@ -7909,7 +7967,7 @@ begin
     DisplayStr := '1.#INF';
   end else begin
     StrValue := FloatToStr(AValue, FPointSeparatorSettings); // Uses '.' as decimal separator
-    DisplayStr := FWorksheet.ReadAsText(ACell); //FloatToStr(AValue); // Uses locale decimal separator
+    DisplayStr := (FWorksheet as TsWorksheet).ReadAsText(ACell); //FloatToStr(AValue); // Uses locale decimal separator
   end;
 
   // Hyperlink
@@ -7948,28 +8006,31 @@ var
   fmt: TsCellFormat;
   numFmtParams: TsNumFormatParams;
   h,m,s,ms: Word;
+  sheet: TsWorksheet;
 begin
   Unused(ARow, ACol);
 
+  sheet := FWorksheet as TsWorksheet;
+
   // Merged?
-  if FWorksheet.IsMergeBase(ACell) then
+  if sheet.IsMergeBase(ACell) then
   begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+    sheet.FindMergedRange(ACell, r1, c1, r2, c2);
     colsSpannedStr := Format(' table:number-columns-spanned="%d"', [c2 - c1 + 1]);
     rowsSpannedStr := Format(' table:number-rows-spanned="%d"', [r2 - r1 + 1]);
     spannedStr := colsSpannedStr + rowsSpannedStr;
   end else
     spannedStr := '';
 
-  fmt := FWorkbook.GetCellFormat(ACell^.FormatIndex);
-  numFmtParams := FWorkbook.GetNumberFormat(fmt.NumberFormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetCellFormat(ACell^.FormatIndex);
+  numFmtParams := (FWorkbook as TsWorkbook).GetNumberFormat(fmt.NumberFormatIndex);
   if fmt.UsedFormattingFields <> [] then
     lStyle := Format(' table:style-name="ce%d"', [ACell^.FormatIndex])
   else
     lStyle := '';
 
   // Comment
-  comment := WriteCommentXMLAsString(FWorksheet.ReadComment(ACell));
+  comment := WriteCommentXMLAsString(sheet.ReadComment(ACell));
 
   // Hyperlink
   if FWorksheet.HasHyperlink(ACell) then
@@ -7982,7 +8043,7 @@ begin
     DecodeTime(AValue, h,m,s,ms);
     strValue := Format('PT%.2dH%.2dM%.2d.%.3dS', [trunc(AValue)*24+h, m, s, ms], FPointSeparatorSettings);
 //    strValue := FormatDateTime(ISO8601FormatHoursOverflow, AValue, [fdoInterval]);
-    displayStr := FWorksheet.ReadAsText(ACell);
+    displayStr := sheet.ReadAsText(ACell);
 //    displayStr := FormatDateTime(fmt.NumberFormatStr, AValue, [fdoInterval]);
     AppendToStream(AStream, Format(
       '<table:table-cell office:value-type="time" office:time-value="%s"%s%s>' +
@@ -8015,7 +8076,7 @@ begin
       end;
       strValue := strValue + 'S';
     end;
-    displayStr := FWorksheet.ReadAsText(ACell);
+    displayStr := sheet.ReadAsText(ACell);
     AppendToStream(AStream, Format(
       '<table:table-cell office:value-type="%s" office:%s-value="%s" %s %s>' +
         comment +
diff --git a/components/fpspreadsheet/source/common/fpspalette.pas b/components/fpspreadsheet/source/common/fpspalette.pas
index 58fd7bb48..9c348d89d 100644
--- a/components/fpspreadsheet/source/common/fpspalette.pas
+++ b/components/fpspreadsheet/source/common/fpspalette.pas
@@ -16,7 +16,7 @@ unit fpsPalette;
 interface
 
 uses
-  Classes, SysUtils, fpstypes, fpspreadsheet;
+  Classes, SysUtils, fpstypes;
 
 type
 
@@ -34,8 +34,8 @@ type
     procedure AddExcelColors;
     function AddUniqueColor(AColor: TsColor; ABigEndian: Boolean = false): Integer;
     procedure Clear;
-    procedure CollectFromWorkbook(AWorkbook: TsWorkbook);
-    function ColorUsedInWorkbook(APaletteIndex: Integer; AWorkbook: TsWorkbook): Boolean;
+    procedure CollectFromWorkbook(AWorkbook: TsBasicWorkbook);
+    function ColorUsedInWorkbook(APaletteIndex: Integer; AWorkbook: TsBasicWorkbook): Boolean;
     function FindClosestColorIndex(AColor: TsColor; AMaxPaletteCount: Integer = -1): Integer;
     function FindColor(AColor: TsColor; AMaxPaletteCount: Integer = -1;
       AStartIndex: Integer = 0): Integer;
@@ -51,7 +51,7 @@ type
 implementation
 
 uses
-  fpsutils;
+  fpsutils, fpspreadsheet;
 
 {@@ ----------------------------------------------------------------------------
   If a palette is coded as big-endian (e.g. by copying the rgb values from
@@ -223,18 +223,19 @@ end;
 {@@ ----------------------------------------------------------------------------
   Collects the colors used in the specified workbook
 -------------------------------------------------------------------------------}
-procedure TsPalette.CollectFromWorkbook(AWorkbook: TsWorkbook);
+procedure TsPalette.CollectFromWorkbook(AWorkbook: TsBasicWorkbook);
 var
   i: Integer;
+  book: TsWorkbook absolute AWorkbook;
   sheet: TsWorksheet;
   cell: PCell;
   fmt: TsCellFormat;
   fnt: TsFont;
   cb: TsCellBorder;
 begin
-  for i:=0 to AWorkbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := AWorkbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i);
     for cell in sheet.Cells do begin
       fmt := sheet.ReadCellFormat(cell);
       if (uffBackground in fmt.UsedFormattingFields) then
@@ -244,7 +245,7 @@ begin
       end;
       if (uffFont in fmt.UsedFormattingFields) then
       begin
-        fnt := AWorkbook.GetFont(fmt.FontIndex);
+        fnt := book.GetFont(fmt.FontIndex);
         AddUniqueColor(fnt.Color);
       end;
       if (uffBorder in fmt.UsedFormattingFields) then
@@ -264,8 +265,9 @@ end;
   @result True if the color is used by at least one cell, false if not.
 -------------------------------------------------------------------------------}
 function TsPalette.ColorUsedInWorkbook(APaletteIndex: Integer;
-  AWorkbook: TsWorkbook): Boolean;
+  AWorkbook: TsBasicWorkbook): Boolean;
 var
+  book: TsWorkbook absolute AWorkbook;
   sheet: TsWorksheet;
   cell: PCell;
   i: Integer;
@@ -279,12 +281,12 @@ begin
     exit(false);
 
   Result := true;
-  for i:=0 to AWorkbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := AWorkbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i);
     for cell in sheet.Cells do
     begin
-      fmt := AWorkbook.GetPointerToCellFormat(cell^.FormatIndex);
+      fmt := book.GetPointerToCellFormat(cell^.FormatIndex);
       if (uffBackground in fmt^.UsedFormattingFields) then
       begin
         if fmt^.Background.BgColor = color then exit;
@@ -296,7 +298,7 @@ begin
             exit;
       if (uffFont in fmt^.UsedFormattingFields) then
       begin
-        fnt := AWorkbook.GetFont(fmt^.FontIndex);
+        fnt := book.GetFont(fmt^.FontIndex);
         if fnt.Color = color then
           exit;
       end;
diff --git a/components/fpspreadsheet/source/common/fpspreadsheet.pas b/components/fpspreadsheet/source/common/fpspreadsheet.pas
index 1e7444371..2073be866 100644
--- a/components/fpspreadsheet/source/common/fpspreadsheet.pas
+++ b/components/fpspreadsheet/source/common/fpspreadsheet.pas
@@ -30,23 +30,6 @@ type
   TsWorksheet = class;
   TsWorkbook = class;
 
-  {@@ Worksheet user interface options:
-    @param soShowGridLines    Show or hide the grid lines in the spreadsheet
-    @param soShowHeaders      Show or hide the column or row headers of the
-                              spreadsheet
-    @param soHasFrozenPanes   If set a number of rows and columns of the
-                              spreadsheet is fixed and does not scroll. The number
-                              is defined by LeftPaneWidth and TopPaneHeight.
-    @param soHidden           Worksheet is hidden.
-    @param soProtected        Worksheet is protected
-    @param soPanesProtection  Panes are locked due to workbook protection }
-  TsSheetOption = (soShowGridLines, soShowHeaders, soHasFrozenPanes, soHidden,
-    soProtected, soPanesProtection);
-
-  {@@ Set of user interface options
-    @ see TsSheetOption }
-  TsSheetOptions = set of TsSheetOption;
-
 
   { TsWorksheet }
 
@@ -77,10 +60,9 @@ type
 
   {@@ The worksheet contains a list of cells and provides a variety of methods
     to read or write data to the cells, or to change their formatting. }
-  TsWorksheet = class
+  TsWorksheet = class(TsBasicWorksheet)
   private
     FWorkbook: TsWorkbook;
-    FName: String;  // Name of the worksheet (displayed at the tab)
     FCells: TsCells;
     FComments: TsComments;
     FMergedCells: TsMergedCells;
@@ -94,7 +76,6 @@ type
     FSelection: TsCellRangeArray;
     FLeftPaneWidth: Integer;
     FTopPaneHeight: Integer;
-    FOptions: TsSheetOptions;
     FFirstRowIndex: Cardinal;
     FFirstColIndex: Cardinal;
     FLastRowIndex: Cardinal;
@@ -105,7 +86,6 @@ type
     FBiDiMode: TsBiDiMode;
     FCryptoInfo: TsCryptoInfo;
     FPageLayout: TsPageLayout;
-    FProtection: TsWorksheetProtections;
     FVirtualColCount: Cardinal;
     FVirtualRowCount: Cardinal;
     FZoomFactor: Double;
@@ -125,7 +105,6 @@ type
     procedure SetBiDiMode(AValue: TsBiDiMode);
     procedure SetDefaultColWidth(AValue: Single);
     procedure SetDefaultRowHeight(AValue: Single);
-    procedure SetName(const AName: String);
     procedure SetVirtualColCount(AValue: Cardinal);
     procedure SetVirtualRowCount(AValue: Cardinal);
     procedure SetZoomFactor(AValue: Double);
@@ -152,6 +131,9 @@ type
       AFromIndex, AToIndex: Cardinal);
     procedure ExchangeCells(ARow1, ACol1, ARow2, ACol2: Cardinal);
 
+    // inherited setters/getters
+    procedure SetName(const AName: String); override;
+
   public
     { Base methods }
     constructor Create;
@@ -523,7 +505,6 @@ type
 
     // Hyperlinks
     function FindHyperlink(ACell: PCell): PsHyperlink;
-    function HasHyperlink(ACell: PCell): Boolean;
     function ReadHyperlink(ACell: PCell): TsHyperlink;
     procedure RemoveHyperlink(ACell: PCell);
     function ValidHyperlink(AValue: String; out AErrMsg: String): Boolean;
@@ -567,7 +548,6 @@ type
 
     { Protection }
     procedure Protect(AEnable: Boolean);
-    function IsProtected: Boolean;
 
     { Notification of changed cells, rows or columns }
     procedure ChangedCell(ARow, ACol: Cardinal);
@@ -592,13 +572,8 @@ type
     property  Hyperlinks: TsHyperlinks read FHyperlinks;
     {@@ FormatSettings for localization of some formatting strings }
     property  FormatSettings: TFormatSettings read GetFormatSettings;
-    {@@ Name of the sheet. In the popular spreadsheet applications this is
-      displayed at the tab of the sheet. }
-    property Name: string read FName write SetName;
     {@@ Parameters to be used for printing by the Office applications }
     property PageLayout: TsPageLayout read FPageLayout write FPageLayout;
-    {@@ Worksheet protection options }
-    property Protection: TsWorksheetProtections read FProtection write FProtection;
     {@@ List of all row records of the worksheet having a non-standard row height }
     property  Rows: TIndexedAVLTree read FRows;
     {@@ Workbook to which the worksheet belongs }
@@ -619,9 +594,6 @@ type
 
     // These are properties to interface to TsWorksheetGrid
     property BiDiMode: TsBiDiMode read FBiDiMode write SetBiDiMode;
-    {@@ Parameters controlling visibility of grid lines and row/column headers,
-        usage of frozen panes etc. }
-    property  Options: TsSheetOptions read FOptions write FOptions;
     {@@ Column index of the selected cell of this worksheet }
     property  ActiveCellCol: Cardinal read FActiveCellCol;
     {@@ Row index of the selected cell of this worksheet }
@@ -656,43 +628,6 @@ type
     property OnZoom: TsNotifyEvent read FOnZoom write FOnZoom;
   end;
 
-  {@@
-    Option flags for the workbook
-
-    @param  boVirtualMode      If in virtual mode date are not taken from cells
-                               when a spreadsheet is written to file, but are
-                               provided by means of the event OnWriteCellData.
-                               Similarly, when data are read they are not added
-                               as cells but passed the the event OnReadCellData;
-    @param  boBufStream        When this option is set a buffered stream is used
-                               for writing (a memory stream swapping to disk) or
-                               reading (a file stream pre-reading chunks of data
-                               to memory)
-    @param  boFileStream       Uses file streams and temporary files during
-                               reading and writing. Lowest memory consumptions,
-                               but slow.
-    @param  boAutoCalc         Automatically recalculate formulas whenever a
-                               cell value changes.
-    @param  boCalcBeforeSaving Calculates formulas before saving the file.
-                               Otherwise there are no results when the file is
-                               loaded back by fpspreadsheet.
-    @param  boReadFormulas     Allows to turn off reading of rpn formulas; this
-                               is a precaution since formulas not correctly
-                               implemented by fpspreadsheet could crash the
-                               reading operation.
-    @param boWriteZoomfactor   Instructs the writer to write the current zoom
-                               factors of the worksheets to file.
-    @param boAbortReadOnFormulaError Aborts reading if a formula error is
-                               encountered
-    @param boIgnoreFormulas    Formulas are not checked and not calculated.
-                               Cannot be used for biff formats. }
-  TsWorkbookOption = (boVirtualMode, boBufStream, boFileStream,
-    boAutoCalc, boCalcBeforeSaving, boReadFormulas, boWriteZoomFactor,
-    boAbortReadOnFormulaError, boIgnoreFormulas);
-
-  {@@ Set of option flags for the workbook }
-  TsWorkbookOptions = set of TsWorkbookOption;
-
   {@@ Event fired when reading a file in virtual mode. Read data are provided in
     the "ADataCell" (which is not added to the worksheet in virtual mode). }
   TsWorkbookReadCellDataEvent = procedure(Sender: TObject; ARow, ACol: Cardinal;
@@ -707,40 +642,32 @@ type
   {@@ FSome action has an effect on existing formulas which must be corrected. }
   TsFormulaCorrection = (fcWorksheetRenamed);
 
-  { TsWorkbook }
+
+    { TsWorkbook }
 
   {@@ The workbook contains the worksheets and provides methods for reading from
     and writing to file. }
-  TsWorkbook = class
+  TsWorkbook = class(TsBasicWorkbook)
   private
     { Internal data }
     FWorksheets: TFPList;
-    FFormatID: TsSpreadFormatID;
     FBuiltinFontCount: Integer;
     FReadWriteFlag: TsReadWriteFlag;
     FCalculationLock: Integer;
-    FOptions: TsWorkbookOptions;
     FActiveWorksheet: TsWorksheet;
     FOnOpenWorkbook: TNotifyEvent;
-    FOnReadCellData: TsWorkbookReadCellDataEvent;
     FOnChangeWorksheet: TsWorksheetEvent;
     FOnRenameWorksheet: TsWorksheetEvent;
     FOnAddWorksheet: TsWorksheetEvent;
     FOnRemoveWorksheet: TsRemoveWorksheetEvent;
     FOnRemovingWorksheet: TsWorksheetEvent;
     FOnSelectWorksheet: TsWorksheetEvent;
-    FFileName: String;
+    FOnReadCellData: TsWorkbookReadCellDataEvent;
     FLockCount: Integer;
-    FLog: TStringList;
     FSearchEngine: TObject;
-    FUnits: TsSizeUnits;
-    FProtection: TsWorkbookProtections;
     FCryptoInfo: TsCryptoInfo;
     {FrevisionsCrypto: TsCryptoInfo;} // Commented out because it needs revision handling
 
-    { Setter/Getter }
-    function GetErrorMsg: String;
-
     { Callback procedures }
     procedure RemoveWorksheetsCallback(data, arg: pointer);
 
@@ -764,11 +691,6 @@ type
 //    procedure ReCalc;
 
   public
-    {@@ A copy of SysUtil's DefaultFormatSettings (converted to UTF8) to provide
-      some kind of localization to some formatting strings.
-      Can be modified before loading/writing files }
-    FormatSettings: TFormatSettings;
-
     { Base methods }
     constructor Create;
     destructor Destroy; override;
@@ -809,7 +731,7 @@ type
     function  GetWorksheetByIndex(AIndex: Integer): TsWorksheet;
     function  GetWorksheetByName(AName: String): TsWorksheet;
     function  GetWorksheetCount: Integer;
-    function  GetWorksheetIndex(AWorksheet: TsWorksheet): Integer; overload;
+    function  GetWorksheetIndex(AWorksheet: TsBasicWorksheet): Integer; overload;
     function  GetWorksheetIndex(const AWorksheetName: String): Integer; overload;
     procedure RemoveAllWorksheets;
     procedure RemoveAllEmptyWorksheets;
@@ -886,33 +808,16 @@ type
     procedure UpdateCaches;
     procedure GetLastRowColIndex(out ALastRow, ALastCol: Cardinal);
 
-    { Protection }
-    function IsProtected: Boolean;
-
     { Notification }
     procedure ChangedWorksheet(AWorksheet: TsWorksheet);
     procedure DisableNotifications;
     procedure EnableNotifications;
     function NotificationsEnabled: Boolean;
 
-    { Error messages }
-    procedure AddErrorMsg(const AMsg: String); overload;
-    procedure AddErrorMsg(const AMsg: String; const Args: array of const); overload;
-    procedure ClearErrorList;
-
     {@@ Identifies the "active" worksheet (only for visual controls)}
     property ActiveWorksheet: TsWorksheet read FActiveWorksheet write SelectWorksheet;
     property CryptoInfo: TsCryptoInfo read FCryptoInfo write FCryptoInfo;
-    {@@ Retrieves error messages collected during reading/writing }
-    property ErrorMsg: String read GetErrorMsg;
-    {@@ Filename of the saved workbook }
-    property FileName: String read FFileName;
-    {@@ Identifies the file format which was detected when reading the file }
-    property FileFormatID: TsSpreadFormatID read FFormatID;
-    property Options: TsWorkbookOptions read FOptions write FOptions;
     {property RevisionsCrypto: TsCryptoInfo read FRevisionsCrypto write FRevisionsCrypto;}
-    property Protection: TsWorkbookProtections read FProtection write FProtection;
-    property Units: TsSizeUnits read FUnits;
 
     {@@ This event fires whenever a new worksheet is added }
     property OnAddWorksheet: TsWorksheetEvent read FOnAddWorksheet write FOnAddWorksheet;
@@ -1217,7 +1122,6 @@ begin
   FActiveCellRow := UNASSIGNED_ROW_COL_INDEX;
   FActiveCellCol := UNASSIGNED_ROW_COL_INDEX;
 
-  FProtection := DEFAULT_SHEET_PROTECTION;
   InitCryptoInfo(FCryptoInfo);
 
   FOptions := [soShowGridLines, soShowHeaders];
@@ -1336,8 +1240,7 @@ begin
                     end;
       rtBoolean   : WriteBoolValue(ACell, res.ResBoolean);
       rtCell      : begin
-//                      cell := GetCell(res.ResRow, res.ResCol);
-                      cell := res.Worksheet.FindCell(res.ResRow, res.ResCol);
+                      cell := (res.Worksheet as TsWorksheet).FindCell(res.ResRow, res.ResCol);
                       if cell <> nil then
                         case cell^.ContentType of
                           cctNumber    : WriteNumber(ACell, cell^.NumberValue);
@@ -1603,14 +1506,6 @@ begin
     Result := nil;
 end;
 
-{@@ ----------------------------------------------------------------------------
-  Checks whether the specified cell contains a hyperlink
--------------------------------------------------------------------------------}
-function TsWorksheet.HasHyperlink(ACell: PCell): Boolean;
-begin
-  Result := (ACell <> nil) and (cfHyperlink in ACell^.Flags);
-end;
-
 {@@ ----------------------------------------------------------------------------
   Reads the hyperlink information of a specified cell.
 
@@ -4201,14 +4096,6 @@ begin
   FWorkbook.ChangedWorksheet(self);
 end;
 
-{@@ ----------------------------------------------------------------------------
-  Returns whether the worksheet is protected
--------------------------------------------------------------------------------}
-function TsWorksheet.IsProtected: Boolean;
-begin
-  Result := soProtected in FOptions;
-end;
-
 
 {@@ ----------------------------------------------------------------------------
   Setter for the worksheet name property. Checks if the name is valid, and
@@ -4221,9 +4108,11 @@ begin
   if (FWorkbook <> nil) then //and FWorkbook.ValidWorksheetName(AName) then
   begin
     FName := AName;
-    FWorkbook.FixFormulas(fcWorksheetRenamed, self, 0);
-    if (FWorkbook.FLockCount = 0) and Assigned(FWorkbook.FOnRenameWorksheet) then
-      FWorkbook.FOnRenameWorksheet(FWorkbook, self);
+    if FWorkbook.FReadWriteFlag = rwfNormal then begin
+      FWorkbook.FixFormulas(fcWorksheetRenamed, self, 0);
+      if (FWorkbook.FLockCount = 0) and Assigned(FWorkbook.FOnRenameWorksheet) then
+        FWorkbook.FOnRenameWorksheet(FWorkbook, self);
+    end;
   end;
 end;
 
@@ -8111,10 +8000,10 @@ begin
   InitFonts;
 
   // Clear error log
-  FLog.Clear;
+  ClearErrorList;
 
   // Abort if virtual mode is active without an event handler
-  if (boVirtualMode in FOptions) and not Assigned(FOnReadCellData) then
+  if (boVirtualMode in FOptions) and not Assigned(OnReadCellData) then
     raise EFPSpreadsheet.Create('[TsWorkbook.PrepareBeforeReading] Event handler "OnReadCellData" required for virtual mode.');
 end;
 
@@ -8129,7 +8018,7 @@ var
   virtModeOK: Boolean;
 begin
   // Clear error log
-  FLog.Clear;
+  ClearErrorList;
 
   // Updates fist/last column/row index
   UpdateCaches;
@@ -8280,13 +8169,6 @@ var
 begin
   inherited Create;
   FWorksheets := TFPList.Create;
-  FLog := TStringList.Create;
-  FFormatID := sfidUnknown;
-  FUnits := suMillimeters;              // Units for column width and row height
-
-  FormatSettings := UTF8FormatSettings;
-// FormatSettings.ShortDateFormat := MakeShortDateFormat(FormatSettings.ShortDateFormat);
-//  FormatSettings.LongDateFormat := MakeLongDateFormat(FormatSettings.ShortDateFormat);
 
   FFontList := TFPList.Create;
   SetDefaultFont(DEFAULT_FONTNAME, DEFAULT_FONTSIZE);
@@ -8302,7 +8184,6 @@ begin
 
   // Protection
   InitCryptoInfo(FCryptoInfo);
-  FProtection := [];
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -8324,7 +8205,6 @@ begin
   RemoveAllEmbeddedObj;
   FEmbeddedObjList.Free;
 
-  FLog.Free;
   FreeAndNil(FSearchEngine);
 
   inherited Destroy;
@@ -8454,14 +8334,6 @@ begin
   end;
 end;
 
-{@@ ----------------------------------------------------------------------------
-  Returns whether the workbook is protected
--------------------------------------------------------------------------------}
-function TsWorkbook.IsProtected: Boolean;
-begin
-  Result := (FProtection <> []);
-end;
-
 {@@ ----------------------------------------------------------------------------
   Reads the document from a file. It is assumed to have the given file format.
 
@@ -9044,7 +8916,7 @@ end;
 {@@ ----------------------------------------------------------------------------
   Returns the index of a worksheet in the worksheet list
 -------------------------------------------------------------------------------}
-function TsWorkbook.GetWorksheetIndex(AWorksheet: TsWorksheet): Integer;
+function TsWorkbook.GetWorksheetIndex(AWorksheet: TsBasicWorksheet): Integer;
 begin
   Result := FWorksheets.IndexOf(AWorksheet);
 end;
@@ -9609,7 +9481,7 @@ begin
     AddFont(AFontName, ASize, [], scBlack)
   else
   for i:=0 to FBuiltinFontCount-1 do
-    if (i <> 4) and (i < FFontList.Count) then
+    if (i <> 4) and (i < FFontList.Count) then           // wp: why if font #4 relevant here ????
       with TsFont(FFontList[i]) do
       begin
         FontName := AFontName;
@@ -9663,21 +9535,8 @@ end;
   @return String with font name, font size etc.
 -------------------------------------------------------------------------------}
 function TsWorkbook.GetFontAsString(AIndex: Integer): String;
-var
-  fnt: TsFont;
 begin
-  fnt := GetFont(AIndex);
-  if fnt <> nil then begin
-    Result := Format('%s; size %.1g; %s', [
-      fnt.FontName, fnt.Size, GetColorName(fnt.Color)]);
-    if (fssBold in fnt.Style) then Result := Result + '; bold';
-    if (fssItalic in fnt.Style) then Result := Result + '; italic';
-    if (fssUnderline in fnt.Style) then Result := Result + '; underline';
-    if (fssStrikeout in fnt.Style) then result := Result + '; strikeout';
-    if fnt.Position = fpSubscript then Result := Result + '; subscript';
-    if fnt.Position = fpSuperscript then Result := Result + '; superscript';
-  end else
-    Result := '';
+  Result := fpsUtils.GetFontAsString(GetFont(AIndex));
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -10200,42 +10059,6 @@ begin
   FEmbeddedObjList.Clear;
 end;
 
-{@@ ----------------------------------------------------------------------------
-  Adds a (simple) error message to an internal list
-
-  @param   AMsg   Error text to be stored in the list
--------------------------------------------------------------------------------}
-procedure TsWorkbook.AddErrorMsg(const AMsg: String);
-begin
-  FLog.Add(AMsg);
-end;
-
-{@@ ----------------------------------------------------------------------------
-  Adds an error message composed by means of format codes to an internal list
-
-  @param   AMsg   Error text to be stored in the list
-  @param   Args   Array of arguments to be used by the Format() function
--------------------------------------------------------------------------------}
-procedure TsWorkbook.AddErrorMsg(const AMsg: String; const Args: Array of const);
-begin
-  FLog.Add(Format(AMsg, Args));
-end;
-
-{@@ ----------------------------------------------------------------------------
-  Clears the internal error message list
--------------------------------------------------------------------------------}
-procedure TsWorkbook.ClearErrorList;
-begin
-  FLog.Clear;
-end;
-
-{@@ ----------------------------------------------------------------------------
-  Getter to retrieve the error messages collected during reading/writing
--------------------------------------------------------------------------------}
-function TsWorkbook.GetErrorMsg: String;
-begin
-  Result := FLog.Text;
-end;
                            (*
 {@@ ----------------------------------------------------------------------------
   Converts a fpspreadsheet color into into a string RRGGBB.
diff --git a/components/fpspreadsheet/source/common/fpsreaderwriter.pas b/components/fpspreadsheet/source/common/fpsreaderwriter.pas
index 1e904a4e1..7a3abbbad 100644
--- a/components/fpspreadsheet/source/common/fpsreaderwriter.pas
+++ b/components/fpspreadsheet/source/common/fpsreaderwriter.pas
@@ -23,7 +23,7 @@ interface
 
 uses
   Classes, Sysutils,
-  fpsTypes, fpsClasses, fpSpreadsheet;
+  fpsTypes, fpsClasses;
 
 type
 
@@ -31,16 +31,16 @@ type
   TsBasicSpreadReaderWriter = class
   protected
     {@@ Instance of the workbook which is currently being read or written. }
-    FWorkbook: TsWorkbook;
+    FWorkbook: TsBasicWorkbook;
     {@@ Instance of the worksheet which is currently being read or written. }
-    FWorksheet: TsWorksheet;
+    FWorksheet: TsBasicWorksheet;
     {@@ Limitations for the specific data file format }
     FLimitations: TsSpreadsheetFormatLimitations;
   public
-    constructor Create(AWorkbook: TsWorkbook); virtual;  // to allow descendents to override it
+    constructor Create(AWorkbook: TsBasicWorkbook); virtual;  // to allow descendents to override it
     function Limitations: TsSpreadsheetFormatLimitations;
     {@@ Instance of the workbook which is currently being read/written. }
-    property Workbook: TsWorkbook read FWorkbook;
+    property Workbook: TsBasicWorkbook read FWorkbook;
   end;
 
   { TsBasicSpreadReader }
@@ -93,9 +93,9 @@ type
     { Helper methods }
     procedure AddBuiltinNumFormats; virtual;
     {@@ Removes column records if all of them have the same column width }
-    procedure FixCols(AWorksheet: TsWorksheet);
+    procedure FixCols(AWorksheet: TsBasicWorksheet);
     {@@ Removes row records if all of them have the same row height }
-    procedure FixRows(AWorksheet: TsWorksheet);
+    procedure FixRows(AWorksheet: TsBasicWorksheet);
 
     { Record reading methods }
     {@@ Abstract method for reading a blank cell. Must be overridden by descendent classes. }
@@ -110,7 +110,7 @@ type
     procedure ReadNumber(AStream: TStream); virtual; abstract;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
 
     { General writing methods }
@@ -148,7 +148,7 @@ type
     function  FindNumFormatInList(ANumFormatStr: String): Integer;
 //    function  FixColor(AColor: TsColor): TsColor; virtual;
     procedure FixFormat(ACell: PCell); virtual;
-    procedure GetSheetDimensions(AWorksheet: TsWorksheet;
+    procedure GetSheetDimensions(AWorksheet: TsBasicWorksheet;
       out AFirstRow, ALastRow, AFirstCol, ALastCol: Cardinal); virtual;
     procedure ListAllNumFormats; virtual;
 
@@ -174,7 +174,7 @@ type
       const AValue: double; ACell: PCell); virtual; abstract;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
 
     { General writing methods }
@@ -219,7 +219,7 @@ implementation
 
 uses
   Math, LazUTF8,
-  fpsStrings, fpsUtils, fpsNumFormat, fpsStreams;
+  fpsStrings, fpsUtils, fpsNumFormat, fpsStreams, fpspreadsheet;
 
 
 {------------------------------------------------------------------------------}
@@ -234,7 +234,7 @@ uses
                     file is written. This parameter is passed from the workbook
                     which creates the reader/writer.
 -------------------------------------------------------------------------------}
-constructor TsBasicSpreadReaderWriter.Create(AWorkbook: TsWorkbook);
+constructor TsBasicSpreadReaderWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create;
   FWorkbook := AWorkbook;
@@ -264,24 +264,27 @@ end;
 -------------------------------------------------------------------------------}
 procedure TsBasicSpreadWriter.CheckLimitations;
 var
+  workbook: TsWorkbook;
   lastCol, lastRow: Cardinal;
   i: Integer;
   sheet: TsWorksheet;
 begin
-  Workbook.GetLastRowColIndex(lastRow, lastCol);
+  workbook := FWorkbook as TsWorkbook;
+
+  workbook.GetLastRowColIndex(lastRow, lastCol);
 
   // Check row count
   if lastRow >= FLimitations.MaxRowCount then
-    Workbook.AddErrorMsg(rsMaxRowsExceeded, [lastRow+1, FLimitations.MaxRowCount]);
+    workbook.AddErrorMsg(rsMaxRowsExceeded, [lastRow+1, FLimitations.MaxRowCount]);
 
   // Check column count
   if lastCol >= FLimitations.MaxColCount then
-    Workbook.AddErrorMsg(rsMaxColsExceeded, [lastCol+1, FLimitations.MaxColCount]);
+    workbook.AddErrorMsg(rsMaxColsExceeded, [lastCol+1, FLimitations.MaxColCount]);
 
   // Check worksheet names
-  for i:=0 to Workbook.GetWorksheetCount-1 do
+  for i:=0 to workbook.GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
+    sheet := workbook.GetWorksheetByIndex(i);
     if UTF8Length(sheet.Name) > FLimitations.MaxSheetNameLength then
       // Worksheet name is too long.
       // We abort saving here because it is not safe to chop the sheet name
@@ -306,7 +309,7 @@ end;
                     This parameter is passed from the workbook which creates
                     the reader.
 -------------------------------------------------------------------------------}
-constructor TsCustomSpreadReader.Create(AWorkbook: TsWorkbook);
+constructor TsCustomSpreadReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   // Font list
@@ -316,7 +319,7 @@ begin
   AddBuiltinNumFormats;
   // Virtual mode
   FIsVirtualMode := (boVirtualMode in FWorkbook.Options) and
-    Assigned(FWorkbook.OnReadCellData);
+    Assigned((FWorkbook as TsWorkbook).OnReadCellData);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -353,10 +356,11 @@ end;
 
   @param   AWorksheet   The columns in this worksheet are processed.
 -------------------------------------------------------------------------------}
-procedure TsCustomSpreadReader.FixCols(AWorkSheet: TsWorksheet);
+procedure TsCustomSpreadReader.FixCols(AWorkSheet: TsBasicWorksheet);
 const
   EPS = 1E-3;
 var
+  sheet: TsWorksheet absolute AWorksheet;
   c: LongInt;
   w: Single;
   lCol: PCol;
@@ -365,30 +369,30 @@ begin
   // If the count of columns is equal to the max colcount of the file format
   // then it is likely that dummy columns have been added -> delete all empty
   // columns (starting at the right) until the first non-empty column is found
-  if AWorksheet.Cols.Count =  SizeInt(FLimitations.MaxColCount) then
+  if sheet.Cols.Count =  SizeInt(FLimitations.MaxColCount) then
   begin
-    c := AWorksheet.Cols.Count - 1;
-    lCol := PCol(AWorksheet.Cols[c]);
+    c := sheet.Cols.Count - 1;
+    lCol := PCol(sheet.Cols[c]);
     w := lCol.Width;
     while c >= 0 do begin
-      lCol := PCol(AWorksheet.Cols[c]);
+      lCol := PCol(sheet.Cols[c]);
       if not SameValue(lCol^.Width, w, EPS) then
         break;
-      if AWorksheet.FindNextCellInCol(0, c) <> nil then
+      if sheet.FindNextCellInCol(0, c) <> nil then
         break;
-      AWorksheet.RemoveCol(c);
+      sheet.RemoveCol(c);
       dec(c);
     end;
   end;
 
-  if AWorksheet.Cols.Count < 2 then
+  if sheet.Cols.Count < 2 then
     exit;
 
   // Check whether all columns have the same column width
   sameWidth := true;
-  w := PCol(AWorksheet.Cols[0])^.Width;
-  for c := 1 to AWorksheet.Cols.Count-1 do begin
-    lCol := PCol(AWorksheet.Cols[c]);
+  w := PCol(sheet.Cols[0])^.Width;
+  for c := 1 to sheet.Cols.Count-1 do begin
+    lCol := PCol(sheet.Cols[c]);
     if not SameValue(lCol^.Width, w, EPS) then
     begin
       sameWidth := false;
@@ -399,12 +403,12 @@ begin
   if sameWidth then begin
     // At this point we know that all columns have the same width. We pass this
     // to the DefaultColWidth ...
-    AWorksheet.WriteDefaultColWidth(w, FWorkbook.Units);
+    sheet.WriteDefaultColWidth(w, FWorkbook.Units);
 
     // ...and delete all column records with non-default format
-    for c := AWorksheet.Cols.Count-1 downto 0 do begin
-      lCol := PCol(AWorksheet.Cols[c]);
-      if lCol^.FormatIndex = 0 then AWorksheet.RemoveCol(c);
+    for c := sheet.Cols.Count-1 downto 0 do begin
+      lCol := PCol(sheet.Cols[c]);
+      if lCol^.FormatIndex = 0 then sheet.RemoveCol(c);
     end;
   end;
 end;
@@ -414,21 +418,22 @@ end;
   row records if they do. Such unnecessary row records are often written
   when an Office application converts a file to another format.
 -------------------------------------------------------------------------------}
-procedure TsCustomSpreadReader.FixRows(AWorkSheet: TsWorksheet);
+procedure TsCustomSpreadReader.FixRows(AWorkSheet: TsBasicWorksheet);
 const
   EPS = 1E-3;
 var
+  sheet: TsWorksheet absolute AWorksheet;
   r, rLast: Cardinal;
   h: Single;
   lRow: PRow;
 begin
-  if AWorksheet.Rows.Count <= 1 then
+  if sheet.Rows.Count <= 1 then
     exit;
 
   // Check whether all rows have the same height
-  h := PRow(AWorksheet.Rows[0])^.Height;
-  for r := 1 to AWorksheet.Rows.Count-1 do begin
-    lRow := PRow(AWorksheet.Rows[r]);
+  h := PRow(sheet.Rows[0])^.Height;
+  for r := 1 to sheet.Rows.Count-1 do begin
+    lRow := PRow(sheet.Rows[r]);
     if not SameValue(lRow^.Height, h, EPS) then
       exit;
   end;
@@ -436,21 +441,21 @@ begin
   // If there are more rows than row records and the common row height is not
   // the default row height (i.e. the row height of the non-record rows) then
   // the row heights are different
-  rLast := AWorksheet.GetLastRowIndex;
-  if (AWorksheet.Rows.Count > 0) and
-     (rLast <> PRow(AWorksheet.Rows[AWorksheet.Rows.Count-1]).Row) and
-     not SameValue(h, AWorksheet.ReadDefaultRowHeight(FWorkbook.Units), EPS)
+  rLast := sheet.GetLastRowIndex;
+  if (sheet.Rows.Count > 0) and
+     (rLast <> PRow(sheet.Rows[sheet.Rows.Count-1]).Row) and
+     not SameValue(h, sheet.ReadDefaultRowHeight(FWorkbook.Units), EPS)
   then
     exit;
 
   // At this point we know that all rows have the same height. We pass this
   // to the DefaultRowHeight ...
-  AWorksheet.WriteDefaultRowHeight(h, FWorkbook.Units);
+  sheet.WriteDefaultRowHeight(h, FWorkbook.Units);
 
   // ... and delete all row records with default format.
-  for r := AWorksheet.Rows.Count-1 downto 0 do begin
-    lRow := PRow(AWorksheet.Rows[r]);
-    if lRow^.FormatIndex = 0 then AWorksheet.RemoveRow(r);
+  for r := sheet.Rows.Count-1 downto 0 do begin
+    lRow := PRow(sheet.Rows[r]);
+    if lRow^.FormatIndex = 0 then sheet.RemoveRow(r);
   end;
 end;
 
@@ -549,7 +554,7 @@ end;
   @param AWorkbook  Workbook from with the file is written. This parameter is
                     passed from the workbook which creates the writer.
 -------------------------------------------------------------------------------}
-constructor TsCustomSpreadWriter.Create(AWorkbook: TsWorkbook);
+constructor TsCustomSpreadWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   // Number formats
@@ -616,26 +621,32 @@ end;
   @param   AFirstCol   Index of first column to be written
   @param   ALastCol    Index of last column to be written
 -------------------------------------------------------------------------------}
-procedure TsCustomSpreadWriter.GetSheetDimensions(AWorksheet: TsWorksheet;
+procedure TsCustomSpreadWriter.GetSheetDimensions(AWorksheet: TsBasicWorksheet;
   out AFirstRow, ALastRow, AFirstCol, ALastCol: Cardinal);
+var
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
-  if (boVirtualMode in AWorksheet.Workbook.Options) then
+  book := FWorkbook as TsWorkbook;
+  sheet := AWorksheet as TsWorksheet;
+
+  if (boVirtualMode in sheet.Workbook.Options) then
   begin
     AFirstRow := 0;
     AFirstCol := 0;
-    ALastRow := LongInt(AWorksheet.VirtualRowCount)-1;
-    ALastCol := LongInt(AWorksheet.VirtualColCount)-1;
+    ALastRow := LongInt(sheet.VirtualRowCount)-1;
+    ALastCol := LongInt(sheet.VirtualColCount)-1;
   end else
   begin
-    Workbook.UpdateCaches;
-    AFirstRow := AWorksheet.GetFirstRowIndex;
+    book.UpdateCaches;
+    AFirstRow := sheet.GetFirstRowIndex;
     if AFirstRow = Cardinal(-1) then
       AFirstRow := 0;  // this happens if the sheet is empty and does not contain row records
-    AFirstCol := AWorksheet.GetFirstColIndex;
+    AFirstCol := sheet.GetFirstColIndex;
     if AFirstCol = Cardinal(-1) then
       AFirstCol := 0;  // this happens if the sheet is empty and does not contain col records
-    ALastRow := AWorksheet.GetLastRowIndex;
-    ALastCol := AWorksheet.GetLastColIndex;
+    ALastRow := sheet.GetLastRowIndex;
+    ALastCol := sheet.GetLastColIndex;
   end;
   if AFirstCol >= Limitations.MaxColCount then
     AFirstCol := Limitations.MaxColCount-1;
@@ -657,9 +668,9 @@ var
   numFmt: TsNumFormatParams;
   numFmtStr: String;
 begin
-  for i:=0 to Workbook.GetNumberFormatCount - 1 do
+  for i:=0 to TsWorkbook(Workbook).GetNumberFormatCount - 1 do
   begin
-    numFmt := Workbook.GetNumberFormat(i);
+    numFmt := TsWorkbook(Workbook).GetNumberFormat(i);
     if numFmt <> nil then
     begin
       numFmtStr := numFmt.NumFormatStr;
@@ -699,7 +710,7 @@ begin
         WriteLabel(AStream, ACell^.Row, ACell^.Col, ACell^.UTF8StringValue, ACell);
     end;
 
-  if FWorksheet.ReadComment(ACell) <> '' then
+  if TsWorksheet(FWorksheet).ReadComment(ACell) <> '' then
     WriteComment(AStream, ACell);
 end;
 
diff --git a/components/fpspreadsheet/source/common/fpstypes.pas b/components/fpspreadsheet/source/common/fpstypes.pas
index 4abcabded..f607f4272 100644
--- a/components/fpspreadsheet/source/common/fpstypes.pas
+++ b/components/fpspreadsheet/source/common/fpstypes.pas
@@ -23,6 +23,10 @@ type
 {$ENDIF}
 
 type
+  { Forward declarations }
+  TsBasicWorksheet = class;
+  TsBasicWorkbook = class;
+
   {@@ Built-in file formats of fpspreadsheet }
   TsSpreadsheetFormat = (sfExcel2, sfExcel5, sfExcel8, sfExcelXML, sfOOXML,
     sfOpenDocument, sfCSV, sfHTML, sfWikiTable_Pipes, sfWikiTable_WikiMedia,
@@ -732,7 +736,7 @@ type
     { Location of the cell }
     Row: Cardinal; // zero-based
     Col: Cardinal; // zero-based
-    Worksheet: Pointer;   // Must be cast to TsWorksheet when used  (avoids circular unit reference)
+    Worksheet: TsBasicWorksheet;   // Must be cast to TsWorksheet when used  (avoids circular unit reference)
     { Status flags }
     Flags: TsCellFlags;
     { Index of format record in the workbook's CellFormatList }
@@ -874,6 +878,124 @@ type
   TsStreamParam = (spClipboard, spWindowsClipboardHTML);
   TsStreamParams = set of TsStreamParam;
 
+  {@@ Worksheet user interface options:
+    @param soShowGridLines    Show or hide the grid lines in the spreadsheet
+    @param soShowHeaders      Show or hide the column or row headers of the
+                              spreadsheet
+    @param soHasFrozenPanes   If set a number of rows and columns of the
+                              spreadsheet is fixed and does not scroll. The number
+                              is defined by LeftPaneWidth and TopPaneHeight.
+    @param soHidden           Worksheet is hidden.
+    @param soProtected        Worksheet is protected
+    @param soPanesProtection  Panes are locked due to workbook protection }
+  TsSheetOption = (soShowGridLines, soShowHeaders, soHasFrozenPanes, soHidden,
+    soProtected, soPanesProtection);
+
+  {@@ Set of user interface options
+    @ see TsSheetOption }
+  TsSheetOptions = set of TsSheetOption;
+
+  {@@ Option flags for the workbook
+    @param  boVirtualMode      If in virtual mode date are not taken from cells
+                               when a spreadsheet is written to file, but are
+                               provided by means of the event OnWriteCellData.
+                               Similarly, when data are read they are not added
+                               as cells but passed the the event OnReadCellData;
+    @param  boBufStream        When this option is set a buffered stream is used
+                               for writing (a memory stream swapping to disk) or
+                               reading (a file stream pre-reading chunks of data
+                               to memory)
+    @param  boFileStream       Uses file streams and temporary files during
+                               reading and writing. Lowest memory consumptions,
+                               but slow.
+    @param  boAutoCalc         Automatically recalculate formulas whenever a
+                               cell value changes.
+    @param  boCalcBeforeSaving Calculates formulas before saving the file.
+                               Otherwise there are no results when the file is
+                               loaded back by fpspreadsheet.
+    @param  boReadFormulas     Allows to turn off reading of rpn formulas; this
+                               is a precaution since formulas not correctly
+                               implemented by fpspreadsheet could crash the
+                               reading operation.
+    @param boWriteZoomfactor   Instructs the writer to write the current zoom
+                               factors of the worksheets to file.
+    @param boAbortReadOnFormulaError Aborts reading if a formula error is
+                               encountered
+    @param boIgnoreFormulas    Formulas are not checked and not calculated.
+                               Cannot be used for biff formats. }
+  TsWorkbookOption = (boVirtualMode, boBufStream, boFileStream,
+    boAutoCalc, boCalcBeforeSaving, boReadFormulas, boWriteZoomFactor,
+    boAbortReadOnFormulaError, boIgnoreFormulas);
+
+  {@@ Set of option flags for the workbook }
+  TsWorkbookOptions = set of TsWorkbookOption;
+
+  {@@ Basic worksheet class to avoid circular unit references. It has only those
+    properties and methods which do not require any other unit than fpstypes. }
+  TsBasicWorksheet = class
+  protected
+    FName: String;  // Name of the worksheet (displayed at the tab)
+    FOptions: TsSheetOptions;
+    FProtection: TsWorksheetProtections;
+    procedure SetName(const AName: String); virtual; abstract;
+  public
+    constructor Create;
+    function HasHyperlink(ACell: PCell): Boolean;
+    function IsProtected: Boolean;
+    {@@ Name of the sheet. In the popular spreadsheet applications this is
+      displayed in the tab of the sheet. }
+    property Name: string read FName write SetName;
+    {@@ Parameters controlling visibility of grid lines and row/column headers,
+      usage of frozen panes etc. }
+    property  Options: TsSheetOptions read FOptions write FOptions;
+    {@@ Worksheet protection options }
+    property Protection: TsWorksheetProtections read FProtection write FProtection;
+  end;
+
+  {@@ Basic worksheet class to avoid circular unit references. It contains only
+    those properties and methods which do not require any other unit than
+    fpstypes. }
+  TsBasicWorkbook = class
+  private
+    FLog: TStringList;
+    function GetErrorMsg: String;
+  protected
+    FFileName: String;
+    FFormatID: TsSpreadFormatID;
+    FOptions: TsWorkbookOptions;
+    FProtection: TsWorkbookProtections;
+    FUnits: TsSizeUnits;
+  public
+    {@@ A copy of SysUtil's DefaultFormatSettings (converted to UTF8) to provide
+      some kind of localization to some formatting strings.
+      Can be modified before loading/writing files }
+    FormatSettings: TFormatSettings;
+
+    constructor Create;
+    destructor Destroy; override;
+
+    { Error messages }
+    procedure AddErrorMsg(const AMsg: String); overload;
+    procedure AddErrorMsg(const AMsg: String; const Args: array of const); overload;
+    procedure ClearErrorList; inline;
+
+    { Protection }
+    function IsProtected: Boolean;
+
+    {@@ Retrieves error messages collected during reading/writing }
+    property ErrorMsg: String read GetErrorMsg;
+    {@@ Identifies the file format which was detected when reading the file }
+    property FileFormatID: TsSpreadFormatID read FFormatID;
+    {@@ Filename of the saved workbook }
+    property FileName: String read FFileName;
+    {@@ Option flags for the workbook - see boXXXX declarations }
+    property Options: TsWorkbookOptions read FOptions write FOptions;
+    {@@ Workbook protection flags }
+    property Protection: TsWorkbookProtections read FProtection write FProtection;
+    {@@ Units of row heights and column widths }
+    property Units: TsSizeUnits read FUnits;
+  end;
+
   {@@ Exception types for fpspreadsheet }
   EFpSpreadsheet = class(Exception);
   EFpSpreadsheetReader = class(EFpSpreadsheet);
@@ -892,6 +1014,10 @@ const
   HEADER_FOOTER_INDEX_EVEN    = 2;
   HEADER_FOOTER_INDEX_ALL     = 1;
 
+var
+  {@@ FPC format settings for which all strings have been converted to UTF8 }
+  UTF8FormatSettings: TFormatSettings;
+
 
 implementation
 
@@ -914,5 +1040,125 @@ begin
   Position := AFont.Position;
 end;
 
+
+{-------------------------------------------------------------------------------
+                              sBasicWorksheet
+-------------------------------------------------------------------------------}
+
+constructor TsBasicWorksheet.Create;
+begin
+  inherited;
+  FProtection := DEFAULT_SHEET_PROTECTION;
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Checks whether the specified cell contains a hyperlink
+-------------------------------------------------------------------------------}
+function TsBasicWorksheet.HasHyperlink(ACell: PCell): Boolean;
+begin
+  Result := (ACell <> nil) and (cfHyperlink in ACell^.Flags);
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Returns whether the worksheet is protected
+-------------------------------------------------------------------------------}
+function TsBasicWorksheet.IsProtected: Boolean;
+begin
+  Result := soProtected in FOptions;
+end;
+
+
+{-------------------------------------------------------------------------------
+                             TsBasicWorkbook
+-------------------------------------------------------------------------------}
+constructor TsBasicWorkbook.Create;
+begin
+  inherited;
+  FormatSettings := UTF8FormatSettings;
+  FUnits := suMillimeters;              // Units for column width and row height
+  FFormatID := sfidUnknown;
+  FLog := TStringList.Create;
+  FProtection := [];
+end;
+
+destructor TsBasicWorkbook.Destroy;
+begin
+  FLog.Free;
+  inherited;
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Adds a (simple) error message to an internal list
+
+  @param   AMsg   Error text to be stored in the list
+-------------------------------------------------------------------------------}
+procedure TsBasicWorkbook.AddErrorMsg(const AMsg: String);
+begin
+  FLog.Add(AMsg);
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Adds an error message composed by means of format codes to an internal list
+
+  @param   AMsg   Error text to be stored in the list
+  @param   Args   Array of arguments to be used by the Format() function
+-------------------------------------------------------------------------------}
+procedure TsBasicWorkbook.AddErrorMsg(const AMsg: String;
+  const Args: Array of const);
+begin
+  FLog.Add(Format(AMsg, Args));
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Clears the internal error message list
+-------------------------------------------------------------------------------}
+procedure TsBasicWorkbook.ClearErrorList;
+begin
+  FLog.Clear;
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Getter to retrieve the error messages collected during reading/writing
+-------------------------------------------------------------------------------}
+function TsBasicWorkbook.GetErrorMsg: String;
+begin
+  Result := FLog.Text;
+end;
+
+{@@ ----------------------------------------------------------------------------
+  Returns whether the workbook is protected
+-------------------------------------------------------------------------------}
+function TsBasicWorkbook.IsProtected: Boolean;
+begin
+  Result := (FProtection <> []);
+end;
+
+
+
+{@@ ----------------------------------------------------------------------------
+  Creates a FPC format settings record in which all strings are encoded as
+  UTF8.
+-------------------------------------------------------------------------------}
+procedure InitUTF8FormatSettings;
+// remove when available in LazUtils
+var
+  i: Integer;
+begin
+  UTF8FormatSettings := DefaultFormatSettings;
+  UTF8FormatSettings.CurrencyString := AnsiToUTF8(DefaultFormatSettings.CurrencyString);
+  for i:=1 to 12 do begin
+    UTF8FormatSettings.LongMonthNames[i] := AnsiToUTF8(DefaultFormatSettings.LongMonthNames[i]);
+    UTF8FormatSettings.ShortMonthNames[i] := AnsiToUTF8(DefaultFormatSettings.ShortMonthNames[i]);
+  end;
+  for i:=1 to 7 do begin
+    UTF8FormatSettings.LongDayNames[i] := AnsiToUTF8(DefaultFormatSettings.LongDayNames[i]);
+    UTF8FormatSettings.ShortDayNames[i] := AnsiToUTF8(DefaultFormatSettings.ShortDayNames[i]);
+  end;
+end;
+
+
+initialization
+  InitUTF8FormatSettings;
+
 end.
 
diff --git a/components/fpspreadsheet/source/common/fpsutils.pas b/components/fpspreadsheet/source/common/fpsutils.pas
index 4672f5629..b7f235d38 100644
--- a/components/fpspreadsheet/source/common/fpsutils.pas
+++ b/components/fpspreadsheet/source/common/fpsutils.pas
@@ -18,7 +18,7 @@ unit fpsutils;
 interface
 
 uses
-  Classes, SysUtils, TypInfo, //StrUtils,
+  Classes, SysUtils, TypInfo,
   fpstypes;
 
 // Exported types
@@ -194,7 +194,8 @@ procedure SplitHyperlink(AValue: String; out ATarget, ABookmark: String);
 procedure FixHyperlinkPathDelims(var ATarget: String);
 
 procedure InitCell(out ACell: TCell); overload;
-procedure InitCell(AWorksheet: Pointer; ARow, ACol: Cardinal; out ACell: TCell); overload;
+procedure InitCell(AWorksheet: TsBasicWorksheet; ARow, ACol: Cardinal;
+  out ACell: TCell); overload;
 procedure InitCryptoInfo(out AValue: TsCryptoInfo);
 procedure InitFormatRecord(out AValue: TsCellFormat);
 procedure InitImageRecord(out AValue: TsImage; ARow, ACol: Cardinal;
@@ -210,6 +211,8 @@ function SameFont(AFont: TsFont; AFontName: String; AFontSize: Single;
 
 function Range(ARow1, ACol1, ARow2, ACol2: Cardinal): TsCellRange;
 
+function GetFontAsString(AFont: TsFont): String;
+
 //function GetUniqueTempDir(Global: Boolean): String;
 
 procedure AppendToStream(AStream: TStream; const AString: String); inline; overload;
@@ -226,9 +229,6 @@ var
   for conversion of distances to pixels}
   ScreenPixelsPerInch: Integer = 96;
 
-  {@@ FPC format settings for which all strings have been converted to UTF8 }
-  UTF8FormatSettings: TFormatSettings;
-
 
 implementation
 
@@ -2348,7 +2348,8 @@ end;
   @param  ACol        Column index of the new cell
   @return New cell record with row and column fields preset to passed values.
 -------------------------------------------------------------------------------}
-procedure InitCell(AWorksheet: Pointer; ARow, ACol: Cardinal; out ACell: TCell);
+procedure InitCell(AWorksheet: TsbasicWorksheet;
+  ARow, ACol: Cardinal; out ACell: TCell);
 begin
   InitCell(ACell);
   ACell.Worksheet := AWorksheet;
@@ -2552,6 +2553,26 @@ begin
   end;
 end;
 
+{@@ ----------------------------------------------------------------------------
+  Combines the relevant font properties into a string
+-------------------------------------------------------------------------------}
+function GetFontAsString(AFont: TsFont): String;
+begin
+  if AFont = nil then
+    Result := ''
+  else begin
+    Result := Format('%s; size %.1g; %s', [
+      AFont.FontName, AFont.Size, GetColorName(AFont.Color)]);
+    if (fssBold in AFont.Style) then Result := Result + '; bold';
+    if (fssItalic in AFont.Style) then Result := Result + '; italic';
+    if (fssUnderline in AFont.Style) then Result := Result + '; underline';
+    if (fssStrikeout in AFont.Style) then result := Result + '; strikeout';
+    if AFont.Position = fpSubscript then Result := Result + '; subscript';
+    if AFont.Position = fpSuperscript then Result := Result + '; superscript';
+  end;
+end;
+
+
                                                  (*
 {@@ ----------------------------------------------------------------------------
   Constructs a string of length "Len" containing random uppercase characters
@@ -2838,30 +2859,5 @@ end;
 {$POP}
 
 
-{@@ ----------------------------------------------------------------------------
-  Creates a FPC format settings record in which all strings are encoded as
-  UTF8.
--------------------------------------------------------------------------------}
-procedure InitUTF8FormatSettings;
-// remove when available in LazUtils
-var
-  i: Integer;
-begin
-  UTF8FormatSettings := DefaultFormatSettings;
-  UTF8FormatSettings.CurrencyString := AnsiToUTF8(DefaultFormatSettings.CurrencyString);
-  for i:=1 to 12 do begin
-    UTF8FormatSettings.LongMonthNames[i] := AnsiToUTF8(DefaultFormatSettings.LongMonthNames[i]);
-    UTF8FormatSettings.ShortMonthNames[i] := AnsiToUTF8(DefaultFormatSettings.ShortMonthNames[i]);
-  end;
-  for i:=1 to 7 do begin
-    UTF8FormatSettings.LongDayNames[i] := AnsiToUTF8(DefaultFormatSettings.LongDayNames[i]);
-    UTF8FormatSettings.ShortDayNames[i] := AnsiToUTF8(DefaultFormatSettings.ShortDayNames[i]);
-  end;
-end;
-
-
-initialization
-  InitUTF8FormatSettings;
-
 end.
 
diff --git a/components/fpspreadsheet/source/common/fpsxmlcommon.pas b/components/fpspreadsheet/source/common/fpsxmlcommon.pas
index 9ebd77c7e..eac2d01a6 100644
--- a/components/fpspreadsheet/source/common/fpsxmlcommon.pas
+++ b/components/fpspreadsheet/source/common/fpsxmlcommon.pas
@@ -15,7 +15,7 @@ uses
  {$ELSE}
   fpszipper,
  {$ENDIF}
-  fpSpreadsheet, fpsreaderwriter;
+  fpstypes, fpsreaderwriter;
 
 type
   TsSpreadXMLReader = class(TsCustomSpreadReader)
@@ -53,7 +53,8 @@ procedure UnzipFile(AZipFileName, AZippedFile, ADestFolder: String);
 function UnzipToStream(AZipStream: TStream; const AZippedFile: String;
   ADestStream: TStream): Boolean;
 
-function CreateTempStream(AWorkbook: TsWorkbook; AFileNameBase: String): TStream;
+function CreateTempStream(AWorkbook: TsBasicWorkbook;
+  AFileNameBase: String): TStream;
 procedure DestroyTempStream(AStream: TStream);
 
 
@@ -379,7 +380,8 @@ end;
   In the latter two cases a filename mask is provided to create a temporary
   filename around this mask.
 -------------------------------------------------------------------------------}
-function CreateTempStream(AWorkbook: TsWorkbook; AFilenameBase: String): TStream;
+function CreateTempStream(AWorkbook: TsBasicWorkbook;
+  AFilenameBase: String): TStream;
 begin
   if boFileStream in AWorkbook.Options then
     Result := TFileStream.Create(GetTempFileName('', AFilenameBase), fmCreate)
diff --git a/components/fpspreadsheet/source/common/wikitable.pas b/components/fpspreadsheet/source/common/wikitable.pas
index cc617dc6c..10ed4ab08 100644
--- a/components/fpspreadsheet/source/common/wikitable.pas
+++ b/components/fpspreadsheet/source/common/wikitable.pas
@@ -31,7 +31,7 @@ interface
 uses
   Classes, SysUtils,
   fpimage, fgl, lconvencoding,
-  fpsTypes, fpSpreadsheet, fpsUtils, fpsReaderWriter;
+  fpsTypes, fpsUtils, fpsReaderWriter;
 
 type
 
@@ -52,10 +52,10 @@ type
 
   TWikiTableTokenizer = class
   private
-    FWorkbook: TsWorkbook;
+    FWorkbook: TsBasicWorkbook;
   public
     Tokens: TWikiTableTokenList;
-    constructor Create(AWorkbook: TsWorkbook); virtual;
+    constructor Create(AWorkbook: TsBasicWorkbook); virtual;
     destructor Destroy; override;
     procedure Clear;
     function AddToken(AValue: string): TWikiTableToken;
@@ -79,7 +79,7 @@ type
 
   TsWikiTable_PipesReader = class(TsWikiTableReader)
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
   end;
 
 
@@ -98,7 +98,7 @@ type
 
   TsWikiTable_WikiMediaWriter = class(TsWikiTableWriter)
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
   end;
 
 
@@ -110,12 +110,12 @@ var
 implementation
 
 uses
-  fpsStrings, fpsXMLCommon;
+  fpsStrings, fpsXMLCommon, fpSpreadsheet;
 
 
 { TWikiTableTokenizer }
 
-constructor TWikiTableTokenizer.Create(AWorkbook: TsWorkbook);
+constructor TWikiTableTokenizer.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create;
   FWorkbook := AWorkbook;
@@ -321,7 +321,7 @@ var
   lLineSplitter: TWikiTableTokenizer;
   lCurToken: TWikiTableToken;
 begin
-  FWorksheet := FWorkbook.AddWorksheet('Table', true);
+  FWorksheet := (FWorkbook as TsWorkbook).AddWorksheet('Table', true);
   lLineSplitter := TWikiTableTokenizer.Create(FWorkbook);
   try
     for i := 0 to AStrings.Count-1 do
@@ -331,11 +331,11 @@ begin
       for j := 0 to lLineSplitter.Tokens.Count-1 do
       begin
         lCurToken := lLineSplitter.Tokens[j];
-        FWorksheet.WriteText(i, j, lCurToken.Value);
+        (FWorksheet as TsWorksheet).WriteText(i, j, lCurToken.Value);
         if lCurToken.Bold then
-          FWorksheet.WriteFontStyle(i, j, [fssBold]);
+          (FWorksheet as TsWorksheet).WriteFontStyle(i, j, [fssBold]);
         if lCurToken.UseBackgroundColor then
-          FWorksheet.WriteBackgroundColor(i, j, lCurToken.BackgroundColor);
+          (FWorksheet as TsWorksheet).WriteBackgroundColor(i, j, lCurToken.BackgroundColor);
       end;
     end;
   finally
@@ -346,7 +346,7 @@ end;
 
 { TsWikiTable_PipesReader }
 
-constructor TsWikiTable_PipesReader.Create(AWorkbook: TsWorkbook);
+constructor TsWikiTable_PipesReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   SubFormat := sfWikiTable_Pipes;
@@ -420,25 +420,27 @@ var
   borders: TsCellBorders;
   fs: TFormatSettings;
   fmt: PsCellFormat;
+  sheet: TsWorksheet;
 begin
-  FWorksheet := Workbook.GetFirstWorksheet();
-  FWorksheet.UpdateCaches;
+  FWorksheet := (Workbook as TsWorkbook).GetFirstWorksheet();
+  sheet := FWorksheet as TsWorksheet;
+  sheet.UpdateCaches;
 
-  fs := FWorksheet.FormatSettings;
+  fs := sheet.FormatSettings;
   fs.DecimalSeparator := '.';
   fs.ThousandSeparator := ',';
 
   AStrings.Add('<!-- generated by fpspreadsheet -->');
 
   // Show/hide grid lines
-  if soShowGridLines in FWorksheet.Options then
+  if soShowGridLines in sheet.Options then
     lCurStr := '{| class="wikitable"' // sortable"'
   else
     lCurStr := '{| border="0" cellpadding="2"';
 
   // Default font
   lStyleStr := '';
-  lFont := FWorkbook.GetDefaultFont;
+  lFont := (FWorkbook as TsWorkbook).GetDefaultFont;
   if lFont.FontName <> DEFAULT_FONTNAME then
     lStyleStr := lStyleStr + Format('font-family:%s;', [lFont.FontName]);
   if fssBold in lFont.Style then
@@ -454,16 +456,16 @@ begin
 
   AStrings.Add(lCurStr);
 
-  for i := 0 to FWorksheet.GetLastRowIndex() do
+  for i := 0 to sheet.GetLastRowIndex() do
   begin
     AStrings.Add('|-');
-    //lRow := FWorksheet.FindRow(i);
+    //lRow := sheet.FindRow(i);
 
-    for j := 0 to FWorksheet.GetLastColIndex do
+    for j := 0 to sheet.GetLastColIndex do
     begin
-      lCell := FWorksheet.FindCell(i, j);
-      //lCol := FWorksheet.FindCol(j);
-      lCurStr := FWorksheet.ReadAsText(lCell, fs);
+      lCell := sheet.FindCell(i, j);
+      //lCol := sheet.FindCol(j);
+      lCurStr := sheet.ReadAsText(lCell, fs);
 
       // Check for invalid characters
       if not ValidXMLText(lCurStr, false) then
@@ -480,32 +482,32 @@ begin
       lRowHeightStr := '';
 
       // Format
-      fmt := FWorksheet.GetPointerToEffectiveCellFormat(i, j);
+      fmt := sheet.GetPointerToEffectiveCellFormat(i, j);
       if fmt <> nil then
         lCurUsedFormatting := fmt^.UsedFormattingFields else
         lCurUsedFormatting := [];
 
       // Row header
       isHeader := (soHasFrozenPanes in FWorksheet.Options) and
-         ((i < cardinal(FWorksheet.TopPaneHeight)) or (j < cardinal(FWorksheet.LeftPaneWidth)));
+         ((i < cardinal(sheet.TopPaneHeight)) or (j < cardinal(sheet.LeftPaneWidth)));
 
       // Column width (to be considered in first row)
       if i = 0 then
         lColWidthStr := Format(' width="%.0fpt"', [
-          FWorkbook.ConvertUnits(FWorksheet.GetColWidth(i, suChars), FWorkbook.Units, suPoints)
+          (FWorkbook as TsWorkbook).ConvertUnits(sheet.GetColWidth(i, suChars), FWorkbook.Units, suPoints)
         ]);
 
       // Row height (to be considered in first column)
       if j = 0 then
         lRowHeightStr := Format(' height="%.0fpt"', [
-          FWorkbook.ConvertUnits(FWorksheet.GetRowHeight(j, suLines), FWorkbook.Units, suPoints)
+          (FWorkbook as TsWorkbook).ConvertUnits(sheet.GetRowHeight(j, suLines), FWorkbook.Units, suPoints)
         ]);
 
       // Font
-      lFont := FWorkbook.GetDefaultFont;
+      lFont := (FWorkbook as TsWorkbook).GetDefaultFont;
       if (uffFont in lCurUsedFormatting) and (fmt <> nil) then
       begin
-        lFont := FWorkbook.GetFont(fmt^.FontIndex);
+        lFont := (FWorkbook as TsWorkbook).GetFont(fmt^.FontIndex);
         if fssBold in lFont.Style then lCurStr := '<b>' + lCurStr + '</b>';
         if fssItalic in lFont.Style then lCurStr := '<i>' + lCurStr + '</i>';
         if fssUnderline in lFont.Style then lCurStr := '<u>' + lCurStr + '</u>';
@@ -570,9 +572,9 @@ begin
       end;
 
       // Merged cells
-      if FWorksheet.IsMerged(lCell) then
+      if sheet.IsMerged(lCell) then
       begin
-        FWorksheet.FindMergedRange(lCell, r1, c1, r2, c2);
+        sheet.FindMergedRange(lCell, r1, c1, r2, c2);
         if (i = r1) and (j = c1) then
         begin
           if r1 < r2 then
@@ -619,7 +621,7 @@ end;
 
 { TsWikiTable_WikiMediaWriter }
 
-constructor TsWikiTable_WikiMediaWriter.Create(AWorkbook: TsWorkbook);
+constructor TsWikiTable_WikiMediaWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   SubFormat := sfWikiTable_WikiMedia;
diff --git a/components/fpspreadsheet/source/common/xlsbiff2.pas b/components/fpspreadsheet/source/common/xlsbiff2.pas
index 6e146eecb..0ddbe4f6a 100644
--- a/components/fpspreadsheet/source/common/xlsbiff2.pas
+++ b/components/fpspreadsheet/source/common/xlsbiff2.pas
@@ -34,7 +34,7 @@ interface
 
 uses
   Classes, SysUtils, lconvencoding,
-  fpsTypes, fpspreadsheet, fpsUtils, xlscommon;
+  fpsTypes, fpsUtils, xlscommon;
 
 const
   BIFF2_MAX_PALETTE_SIZE = 8;
@@ -75,7 +75,7 @@ type
     procedure ReadWindow2(AStream: TStream); override;
     procedure ReadXF(AStream: TStream);
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     { General reading methods }
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
       AParams: TsStreamParams = []); override;
@@ -100,8 +100,8 @@ type
     procedure WriteColumnDefault(AStream: TStream;
         AFirstColIndex, ALastColIndex: Word; AFormatIndex: Integer);
     procedure WriteColumnDefaults(AStream: TStream);
-    procedure WriteDefaultRowHeight(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteDimensions(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteDefaultRowHeight(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteDimensions(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteEOF(AStream: TStream);
     procedure WriteFont(AStream: TStream; AFontIndex: Integer);
     procedure WriteFonts(AStream: TStream);
@@ -111,7 +111,7 @@ type
     procedure AddBuiltinNumFormats; override;
     function FunctionSupported(AExcelCode: Integer;
       const AFuncName: String): Boolean; override;
-    procedure PopulatePalette(AWorkbook: TsWorkbook); override;
+    procedure PopulatePalette(AWorkbook: TsbasicWorkbook); override;
     procedure WriteBlank(AStream: TStream; const ARow, ACol: Cardinal;
       ACell: PCell); override;
     procedure WriteBool(AStream: TStream; const ARow, ACol: Cardinal;
@@ -126,7 +126,7 @@ type
     procedure WriteNumber(AStream: TStream; const ARow, ACol: Cardinal;
       const AValue: double; ACell: PCell); override;
     procedure WritePASSWORD(AStream: TStream);
-    procedure WriteRow(AStream: TStream; ASheet: TsWorksheet;
+    procedure WriteRow(AStream: TStream; ASheet: TsBasicWorksheet;
       ARowIndex, AFirstColIndex, ALastColIndex: Cardinal; ARow: PRow); override;
     procedure WriteRPNFormula(AStream: TStream; const ARow, ACol: Cardinal;
       AFormula: TsRPNFormula; ACell: PCell); override;
@@ -134,11 +134,11 @@ type
     procedure WriteRPNTokenArraySize(AStream: TStream; ASize: Word); override;
     procedure WriteStringRecord(AStream: TStream; AString: String); override;
     procedure WriteWindow1(AStream: TStream); override;
-    procedure WriteWindow2(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteWindow2(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure WriteXF(AStream: TStream; AFormatRecord: PsCellFormat;
       XFType_Prot: Byte = 0); override;
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsbasicWorkbook); override;
     procedure WriteToStream(AStream: TStream; AParams: TsStreamParams = []); override;
   end;
 
@@ -180,7 +180,7 @@ uses
   LazLogger,
  {$ENDIF}
   Math,
-  fpsStrings, fpsReaderWriter, fpsPalette, fpsNumFormat;
+  fpsStrings, fpspreadsheet, fpsReaderWriter, fpsPalette, fpsNumFormat;
 
 const
   { Excel record IDs }
@@ -320,7 +320,7 @@ end;
 {                             TsSpreadBIFF2Reader                              }
 {------------------------------------------------------------------------------}
 
-constructor TsSpreadBIFF2Reader.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFF2Reader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   InitBiff2Limitations(FLimitations);
@@ -342,10 +342,10 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := TsWorksheet(FWorksheet).AddCell(ARow, ACol);
   ApplyCellFormatting(cell, XF);
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(FWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -358,7 +358,10 @@ var
   r, c: Cardinal;
   xf: Word;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   { Read entire record, starting at Row }
   rec.Row := 0;  // to silence the compiler...
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF2_BoolErrRecord) - 2*SizeOf(Word));
@@ -372,19 +375,19 @@ begin
     InitCell(FWorksheet, r, c, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(r, c);
+    cell := sheet.AddCell(r, c);
 
   { Retrieve boolean or error value depending on the "ValueType" }
   case rec.ValueType of
-    0: FWorksheet.WriteBoolValue(cell, boolean(rec.BoolErrValue));
-    1: FWorksheet.WriteErrorValue(cell, ConvertFromExcelError(rec.BoolErrValue));
+    0: sheet.WriteBoolValue(cell, boolean(rec.BoolErrValue));
+    1: sheet.WriteErrorValue(cell, ConvertFromExcelError(rec.BoolErrValue));
   end;
 
   { Apply formatting }
   ApplyCellFormatting(cell, xf);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, r, c, cell);
+    TsWorkbook(FWorkbook).OnReadCellData(Workbook, r, c, cell);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadColumnDefault(AStream: TStream);
@@ -398,7 +401,10 @@ var
   nf: TsNumFormatParams;
   nfs: String;
   b: Byte;
+  book: TsWorkbook;
 begin
+  book := TsWorkbook(FWorkbook);
+
   { Index of first column }
   col1 := WordLEToN(AStream.ReadWord);
 
@@ -417,9 +423,9 @@ begin
   fontIndex := (attr2 and $C0) shr 6;
   if fontIndex > 4 then dec(fontIndex);  // Watch out for the nasty missing font #4...
   fnt := TsFont(FFontList[fontIndex]);
-  fmt.FontIndex := Workbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
+  fmt.FontIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
   if fmt.FontIndex = -1 then
-    fmt.FontIndex := Workbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
+    fmt.FontIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
   if fmt.FontIndex > 0 then
     Include(fmt.UsedFormattingFields, uffFont);
 
@@ -427,8 +433,8 @@ begin
   b := attr2 and $3F;
   nfs := NumFormatList[b];
   if nfs <> '' then begin
-    fmt.NumberFormatIndex := Workbook.AddNumberFormat(nfs);
-    nf := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+    fmt.NumberFormatIndex := book.AddNumberFormat(nfs);
+    nf := book.GetNumberFormat(fmt.NumberFormatIndex);
     fmt.NumberFormat := nf.NumFormat;
     fmt.NumberFormatStr := nf.NumFormatStr;
     if fmt.NumberFormat <> nfGeneral then
@@ -477,10 +483,10 @@ begin
 
   // Add the decoded data to the format list
   FCellFormatList.Add(fmt);
-  fmtIndex := FWorkbook.AddCellFormat(fmt);
+  fmtIndex := book.AddCellFormat(fmt);
 
   for c := col1 to col2 do
-    FWorksheet.WriteColFormatIndex(c, fmtIndex);
+    TsWorksheet(FWorksheet).WriteColFormatIndex(c, fmtIndex);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadColWidth(AStream: TStream);
@@ -490,18 +496,21 @@ var
   c, c1, c2: Cardinal;
   w: Word;
   colwidth: Single;
+  sheet: TsWorksheet;
 begin
+  sheet := TsWorksheet(FWorksheet);
+
   // read column start and end index of column range
   c1 := AStream.ReadByte;
   c2 := AStream.ReadByte;
   // read col width in 1/256 of the width of "0" character
   w := WordLEToN(AStream.ReadWord);
   // calculate width in units of "characters"
-  colwidth := FWorkbook.ConvertUnits(w / 256, suChars, FWorkbook.Units);
+  colwidth := (FWorkbook as TsWorkbook).ConvertUnits(w / 256, suChars, FWorkbook.Units);
   // assign width to columns, but only if different from default column width.
-  if not SameValue(colwidth, FWorksheet.ReadDefaultColWidth(FWorkbook.Units), EPS) then
+  if not SameValue(colwidth, sheet.ReadDefaultColWidth(FWorkbook.Units), EPS) then
     for c := c1 to c2 do
-      FWorksheet.WriteColWidth(c, colwidth, FWorkbook.Units);
+      sheet.WriteColWidth(c, colwidth, FWorkbook.Units);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadDefRowHeight(AStream: TStream);
@@ -511,12 +520,7 @@ var
 begin
   hw := WordLEToN(AStream.ReadWord);
   h := TwipsToPts(hw and $7FFF);
-  FWorksheet.WriteDefaultRowHeight(h, suPoints);
-  {
-  h := TwipsToPts(hw and $8000) / FWorkbook.GetDefaultFontSize;
-  if h > ROW_HEIGHT_CORRECTION then
-    FWorksheet.DefaultRowHeight := h - ROW_HEIGHT_CORRECTION;
-    }
+  (FWorksheet as TsWorksheet).WriteDefaultRowHeight(h, suPoints);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadFONT(AStream: TStream);
@@ -553,7 +557,7 @@ begin
   FFontList.Add(FFont);
 
   if isDefaultFont then
-    Workbook.SetDefaultFont(FFont.FontName, FFont.Size);
+    TsWorkbook(FWorkbook).SetDefaultFont(FFont.FontName, FFont.Size);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadFONTCOLOR(AStream: TStream);
@@ -606,7 +610,7 @@ begin
   BIFF2EOF := False;
 
   { In BIFF2 files there is only one worksheet, let's create it }
-  FWorksheet := FWorkbook.AddWorksheet('Sheet', true);
+  FWorksheet := TsWorkbook(FWorkbook).AddWorksheet('Sheet', true);
 
   { Read all records in a loop }
   BOFFound := false;
@@ -685,7 +689,10 @@ var
   nfs: String;
   err: TsErrorValue;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
+  sheet := TsWorksheet(FWorksheet);
+
   { BIFF Record row/column/style }
   ReadRowColXF(AStream, ARow, ACol, XF);
 
@@ -701,7 +708,7 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := sheet.AddCell(ARow, ACol);
 
   // Now determine the type of the formula result
   if (Data[6] = $FF) and (Data[7] = $FF) then
@@ -709,7 +716,7 @@ begin
       0: // String -> Value is found in next record (STRING)
          FIncompleteCell := cell;
       1: // Boolean value
-         FWorksheet.WriteBoolValue(cell, Data[2] = 1);
+         sheet.WriteBoolValue(cell, Data[2] = 1);
       2: begin  // Error value
            case Data[2] of
              ERR_INTERSECTION_EMPTY   : err := errEmptyIntersection;
@@ -720,10 +727,10 @@ begin
              ERR_OVERFLOW             : err := errOverflow;
              ERR_ARG_ERROR            : err := errArgError;
            end;
-           FWorksheet.WriteErrorValue(cell, err);
+           sheet.WriteErrorValue(cell, err);
          end;
       3: // Empty cell
-         FWorksheet.WriteBlank(cell);
+         sheet.WriteBlank(cell);
     end
   else
   begin
@@ -733,23 +740,23 @@ begin
     {Find out what cell type, set content type and value}
     ExtractNumberFormat(XF, nf, nfs);
     if IsDateTime(formulaResult, nf, nfs, dt) then
-      FWorksheet.WriteDateTime(cell, dt, nf, nfs)
+      sheet.WriteDateTime(cell, dt, nf, nfs)
     else
-      FWorksheet.WriteNumber(cell, formulaResult, nf, nfs);
+      sheet.WriteNumber(cell, formulaResult, nf, nfs);
   end;
 
   { Formula token array }
   if (boReadFormulas in FWorkbook.Options) then
   begin
     ok := ReadRPNTokenArray(AStream, cell);
-    if not ok then FWorksheet.WriteErrorValue(cell, errFormulaNotSupported);
+    if not ok then sheet.WriteErrorValue(cell, errFormulaNotSupported);
   end;
 
   { Apply formatting to cell }
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode and (cell <> FIncompleteCell) then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(FWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadLabel(AStream: TStream);
@@ -761,7 +768,10 @@ var
   ansiStr: ansistring;
   valueStr: UTF8String;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   { Read entire record, starting at Row, except for string data }
   rec.Row := 0;  // to silence the compiler...
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF2_LabelRecord) - 2*SizeOf(Word));
@@ -777,33 +787,20 @@ begin
 
   { Save the data }
   valueStr := ConvertEncoding(ansiStr, FCodePage, encodingUTF8);
-  {
-  case WorkBookEncoding of
-    seLatin2:   AStrValue := CP1250ToUTF8(AValue);
-    seCyrillic: AStrValue := CP1251ToUTF8(AValue);
-    seGreek:    AStrValue := CP1253ToUTF8(AValue);
-    seTurkish:  AStrValue := CP1254ToUTF8(AValue);
-    seHebrew:   AStrValue := CP1255ToUTF8(AValue);
-    seArabic:   AStrValue := CP1256ToUTF8(AValue);
-  else
-    // Latin 1 is the default
-    AStrValue := CP1252ToUTF8(AValue);
-  end;
-  }
 
   { Create cell }
   if FIsVirtualMode then begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
-  FWorksheet.WriteText(cell, valueStr);
+    cell := sheet.AddCell(ARow, ACol);
+  sheet.WriteText(cell, valueStr);
 
   { Apply formatting to cell }
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode and (cell <> FIncompleteCell) then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(FWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadNumber(AStream: TStream);
@@ -816,7 +813,10 @@ var
   nf: TsNumberFormat;
   nfs: String;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   { Read entire record, starting at Row }
   rec.Row := 0;  // to silence the compiler...
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF2_NumberRecord) - 2*SizeOf(Word));
@@ -831,30 +831,33 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := sheet.AddCell(ARow, ACol);
 
   {Find out what cell type, set content type and value}
   ExtractNumberFormat(XF, nf, nfs);
   if IsDateTime(value, nf, nfs, dt) then
-    FWorksheet.WriteDateTime(cell, dt, nf, nfs)
+    sheet.WriteDateTime(cell, dt, nf, nfs)
   else
-    FWorksheet.WriteNumber(cell, value, nf, nfs);
+    sheet.WriteNumber(cell, value, nf, nfs);
 
   { Apply formatting to cell }
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode and (cell <> FIncompleteCell) then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(FWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadBIFF2Reader.ReadInteger(AStream: TStream);
 var
+  sheet: TsWorksheet;
   ARow, ACol: Cardinal;
   XF: Word;
   AWord  : Word = 0;
   cell: PCell;
   rec: TBIFF2_IntegerRecord;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   { Read record into buffer }
   rec.Row := 0;   // to silence the comiler...
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF2_NumberRecord) - 2*SizeOf(Word));
@@ -870,16 +873,16 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := sheet.AddCell(ARow, ACol);
 
   { Save the data }
-  FWorksheet.WriteNumber(cell, AWord);
+  sheet.WriteNumber(cell, AWord);
 
   { Apply formatting to cell }
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode and (cell <> FIncompleteCell) then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    TsWorkbook(FWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -911,14 +914,14 @@ begin
 
   // Use the same password for workbook and worksheet protection because
   // BIFF2 can have only a single sheet.
-  FWorkbook.CryptoInfo := cinfo;
-  FWorksheet.CryptoInfo := cinfo;
+  (FWorkbook as TsWorkbook).CryptoInfo := cinfo;
+  (FWorksheet as TsWorksheet).CryptoInfo := cinfo;
 end;
 
 procedure TsSpreadBIFF2Reader.ReadPROTECT(AStream: TStream);
 begin
   inherited ReadPROTECT(AStream);
-  FWorksheet.Protect(Workbook.IsProtected);
+  (FWorksheet as TsWorksheet).Protect(Workbook.IsProtected);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -966,13 +969,18 @@ var
   defRowHeight: Single;
   containsXF: Boolean;
   xf: Word;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
+  book := FWorkbook as TsWorkbook;
+  sheet := FWorksheet as TsWorksheet;
+
   rowRec.RowIndex := 0;  // to silence the compiler...
   AStream.ReadBuffer(rowrec, SizeOf(TRowRecord));
   h := WordLEToN(rowrec.Height);
   auto := h and $8000 <> 0;
-  rowheight := FWorkbook.ConvertUnits(TwipsToPts(h and $7FFF), suPoints, FWorkbook.Units);
-  defRowHeight := FWorksheet.ReadDefaultRowHeight(FWorkbook.Units);
+  rowheight := book.ConvertUnits(TwipsToPts(h and $7FFF), suPoints, FWorkbook.Units);
+  defRowHeight := sheet.ReadDefaultRowHeight(FWorkbook.Units);
   containsXF := rowRec.ContainsXF = 1;
   xf := WordLEToN(rowRec.XFIndex);
 
@@ -982,7 +990,7 @@ begin
     exit;
 
   // Otherwise: create a row record
-  lRow := FWorksheet.GetRow(WordLEToN(rowrec.RowIndex));
+  lRow := sheet.GetRow(WordLEToN(rowrec.RowIndex));
   lRow^.Height := rowHeight;
   if auto then
     lRow^.RowHeightType := rhtAuto else
@@ -1062,7 +1070,9 @@ begin
       FIncompleteCell^.UTF8StringValue := ConvertEncoding(s, FCodePage, encodingUTF8);
       FIncompleteCell^.ContentType := cctUTF8String;
       if FIsVirtualMode then
-        Workbook.OnReadCellData(Workbook, FIncompleteCell^.Row, FIncompleteCell^.Col, FIncompleteCell);
+        TsWorkbook(FWorkbook).OnReadCellData(FWorkbook,
+          FIncompleteCell^.Row, FIncompleteCell^.Col, FIncompleteCell
+        );
     end;
   end;
   FIncompleteCell := nil;
@@ -1120,7 +1130,10 @@ var
   nfs: String;
   i: Integer;
   fnt: TsFont;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   // Read entire xf record into buffer
   InitFormatRecord(fmt);
   fmt.ID := FCellFormatList.Count;
@@ -1132,9 +1145,9 @@ begin
   i := rec.FontIndex;
   if i > 4 then dec(i);  // Watch out for the nasty missing font #4...
   fnt := TsFont(FFontList[i]);
-  fmt.FontIndex := Workbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
+  fmt.FontIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
   if fmt.FontIndex = -1 then
-    fmt.FontIndex := Workbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
+    fmt.FontIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color);
   if fmt.FontIndex > 0 then
     Include(fmt.UsedFormattingFields, uffFont);
 
@@ -1143,8 +1156,8 @@ begin
   nfs := NumFormatList[b];
   if nfs <> '' then
   begin
-    fmt.NumberFormatIndex := Workbook.AddNumberFormat(nfs);
-    nf := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+    fmt.NumberFormatIndex := book.AddNumberFormat(nfs);
+    nf := book.GetNumberFormat(fmt.NumberFormatIndex);
     fmt.NumberFormat := nf.NumFormat;
     fmt.NumberFormatStr := nf.NumFormatStr;
     if fmt.NumberFormat <> nfGeneral then
@@ -1211,7 +1224,7 @@ end;
 {                           TsSpreadBIFF2Writer                                }
 {------------------------------------------------------------------------------}
 
-constructor TsSpreadBIFF2Writer.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFF2Writer.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -1252,7 +1265,7 @@ var
   fmt: PsCellFormat;
   fontIdx, formatIdx: Integer;
 begin
-  fmt := Workbook.GetPointerToCellFormat(AFormatIndex);
+  fmt := (Workbook as TsWorkbook).GetPointerToCellFormat(AFormatIndex);
 
   if fmt^.UsedFormattingFields = [] then begin
     Attrib1 := 15 + MASK_XF_TYPE_PROT_LOCKED_BIFF2;  // $40
@@ -1308,7 +1321,7 @@ begin
   AFormatIndex := 0;
   if (AFormatRecord <> nil) and (uffNumberFormat in AFormatRecord^.UsedFormattingFields) then
   begin
-    nfParams := Workbook.GetNumberFormat(AFormatRecord^.NumberFormatIndex);
+    nfParams := TsWorkbook(FWorkbook).GetNumberFormat(AFormatRecord^.NumberFormatIndex);
     nfs := nfParams.NumFormatStr;
     AFormatIndex := NumFormatList.IndexOf(nfs);
     if AFormatIndex = -1 then AFormatIndex := 0;
@@ -1323,7 +1336,7 @@ begin
   end;
 end;
 
-procedure TsSpreadBIFF2Writer.PopulatePalette(AWorkbook: TsWorkbook);
+procedure TsSpreadBIFF2Writer.PopulatePalette(AWorkbook: TsBasicWorkbook);
 begin
   FPalette.Clear;
   FPalette.AddBuiltinColors(false);
@@ -1353,7 +1366,7 @@ var
   fmt: PsCellFormat;
   w: Word;
 begin
-  fmt := Workbook.GetPointerToCellFormat(AFormatIndex);
+  fmt := TsWorkbook(FWorkbook).GetPointerToCellFormat(AFormatIndex);
   rec.XFIndex_Locked_Hidden := 0;  // to silence the compiler...
   FillChar(rec, SizeOf(rec), 0);
 
@@ -1466,7 +1479,7 @@ var
   lCol, lCol1: PCol;
   lastcol: Integer;
 begin
-  sheet := Workbook.GetFirstWorksheet;
+  sheet := TsWorkbook(FWorkbook).GetFirstWorksheet;
   j := 0;
   while (j < sheet.Cols.Count) do begin
     lCol := PCol(sheet.Cols[j]);
@@ -1518,9 +1531,9 @@ begin
   { Column width }
   { calculate width to be in units of 1/256 of pixel width of character "0" }
   if ACol^.ColWidthType = cwtDefault then
-    w := FWorksheet.ReadDefaultColWidth(suChars)
+    w := TsWorksheet(FWorksheet).ReadDefaultColWidth(suChars)
   else
-    w := FWorkbook.ConvertUnits(ACol^.Width, FWorkbook.Units, suChars);
+    w := tsWorkbook(FWorkbook).ConvertUnits(ACol^.Width, FWorkbook.Units, suChars);
   rec.ColWidth := WordToLE(round(w*256));
 
   { Write out }
@@ -1536,7 +1549,7 @@ var
   sheet: TsWorksheet;
   col: PCol;
 begin
-  sheet := Workbook.GetFirstWorksheet;
+  sheet := TsWorkbook(FWorkbook).GetFirstWorksheet;
   for j := 0 to sheet.Cols.Count-1 do begin
     col := PCol(sheet.Cols[j]);
     WriteColWidth(AStream, col);
@@ -1547,7 +1560,7 @@ end;
   Writes an Excel 2 DIMENSIONS record
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF2Writer.WriteDimensions(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   firstRow, lastRow, firstCol, lastCol: Cardinal;
   rec: TBIFF2_DimensionsRecord;
@@ -1595,7 +1608,7 @@ var
 begin
   Unused(AParams);
 
-  FWorksheet := Workbook.GetWorksheetByIndex(FSheetIndex);
+  FWorksheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(FSheetIndex);
   if FWorksheet = nil then
     raise EFPSpreadsheetWriter.Create(rsWorksheetNotFound1);
 
@@ -1633,7 +1646,7 @@ begin
     if (boVirtualMode in Workbook.Options) then
       WriteVirtualCells(AStream, FWorksheet)
     else
-      WriteCellsToStream(AStream, FWorksheet.Cells);
+      WriteCellsToStream(AStream, TsWorksheet(FWorksheet).Cells);
 
     WriteWindow1(AStream);
     //  { -- currently not working
@@ -1673,9 +1686,10 @@ end;
   Writes an Excel 2 WINDOW2 record
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF2Writer.WriteWindow2(AStream: TStream;
- ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   b: Byte;
+  sheet: TsWorksheet absolute ASheet;
 begin
   { BIFF Record header }
   AStream.WriteWord(WordToLE(INT_EXCEL_ID_WINDOW2));
@@ -1685,17 +1699,17 @@ begin
   AStream.WriteByte(0);
 
   { Show grid lines }
-  b := IfThen(soShowGridLines in ASheet.Options, 1, 0);
+  b := IfThen(soShowGridLines in sheet.Options, 1, 0);
   AStream.WriteByte(b);
 
   { Show sheet headers }
-  b := IfThen(soShowHeaders in ASheet.Options, 1, 0);
+  b := IfThen(soShowHeaders in sheet.Options, 1, 0);
   AStream.WriteByte(b);
 
   { Panes are frozen? }
   b := 0;
-  if (soHasFrozenPanes in ASheet.Options) and
-     ((ASheet.LeftPaneWidth > 0) or (ASheet.TopPaneHeight > 0))
+  if (soHasFrozenPanes in sheet.Options) and
+     ((sheet.LeftPaneWidth > 0) or (sheet.TopPaneHeight > 0))
   then
     b := 1;
   AStream.WriteByte(b);
@@ -1820,7 +1834,7 @@ var
   optn: Word;
   font: TsFont;
 begin
-  font := Workbook.GetFont(AFontIndex);
+  font := TsWorkbook(FWorkbook).GetFont(AFontIndex);
   if font = nil then  // this happens for FONT4 in case of BIFF
     exit;
 
@@ -1868,7 +1882,7 @@ procedure TsSpreadBiff2Writer.WriteFonts(AStream: TStream);
 var
   i: Integer;
 begin
-  for i:=0 to Workbook.GetFontCount-1 do
+  for i:=0 to TsWorkbook(FWorkbook).GetFontCount-1 do
     WriteFont(AStream, i);
 end;
 
@@ -2075,7 +2089,7 @@ end;
   corresponding ROW record
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF2Writer.WriteDefaultRowHeight(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   h: Single;
 begin
@@ -2085,7 +2099,7 @@ begin
   { Default height for unused rows, in twips = 1/20 of a point
     Bits 0-14: Default height for unused rows, in twips
     Bit 15 = 1: Row height not changed manually }
-  h := AWorksheet.ReadDefaultRowHeight(suPoints);  // h is in points
+  h := TsWorksheet(AWorksheet).ReadDefaultRowHeight(suPoints);  // h is in points
   AStream.WriteWord(WordToLE(PtsToTwips(h)));      // write as twips
 end;
 
@@ -2267,20 +2281,25 @@ procedure TsSpreadBIFF2Writer.WritePassword(AStream: TStream);
 var
   hash: Word;
   hb, hs: LongInt;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
+  book := FWorkbook as TsWorkbook;
+  sheet := FWorksheet as TsWorksheet;
+
   hb := 0;
-  if (Workbook.CryptoInfo.PasswordHash <> '') and
-     not TryStrToInt('$' + Workbook.CryptoInfo.PasswordHash, hb) then
+  if (book.CryptoInfo.PasswordHash <> '') and
+     not TryStrToInt('$' + book.CryptoInfo.PasswordHash, hb) then
   begin
-    Workbook.AddErrorMsg(rsPasswordRemoved_NotValid);
+    book.AddErrorMsg(rsPasswordRemoved_NotValid);
     exit;
   end;
 
   hs := 0;
-  if (FWorksheet.CryptoInfo.PasswordHash <> '') and
-     not TryStrToInt('$' + FWorksheet.CryptoInfo.PasswordHash, hs) then
+  if (sheet.CryptoInfo.PasswordHash <> '') and
+     not TryStrToInt('$' + sheet.CryptoInfo.PasswordHash, hs) then
   begin
-    Workbook.AddErrorMsg(rsPasswordRemoved_NotValid);
+    book.AddErrorMsg(rsPasswordRemoved_NotValid);
     exit;
   end;
 
@@ -2290,28 +2309,28 @@ begin
 
   // Only workbook password set. Check for Excel algorithm.
   if (hb <> 0) and (hs = 0) then begin
-    if Workbook.CryptoInfo.Algorithm <> caExcel then begin
-      Workbook.AddErrorMsg(rsPasswordRemoved_Excel);
+    if book.CryptoInfo.Algorithm <> caExcel then begin
+      book.AddErrorMsg(rsPasswordRemoved_Excel);
       exit;
     end;
     hash := hb;
   end else
   // Only worksheet password set, check for Excel algorithm
   if (hs <> 0) and (hb = 0) then begin
-    if FWorksheet.CryptoInfo.Algorithm <> caExcel then begin
-      Workbook.AddErrorMsg(rsPasswordRemoved_Excel);
+    if sheet.CryptoInfo.Algorithm <> caExcel then begin
+      book.AddErrorMsg(rsPasswordRemoved_Excel);
       exit;
     end;
     hash := hs;
   end else
   if (hs <> hb) then begin
-    Workbook.AddErrorMsg(rsPasswordRemoved_BIFF2);
+    book.AddErrorMsg(rsPasswordRemoved_BIFF2);
     exit;
   end else
-  if (Workbook.CryptoInfo.Algorithm <> caExcel) or
-     (FWorksheet.CryptoInfo.Algorithm <> caExcel) then
+  if (book.CryptoInfo.Algorithm <> caExcel) or
+     (sheet.CryptoInfo.Algorithm <> caExcel) then
   begin
-    Workbook.AddErrorMsg(rsPasswordRemoved_Excel);
+    book.AddErrorMsg(rsPasswordRemoved_Excel);
     exit;
   end else
     hash := hs;  // or hb -- they are equal here.
@@ -2321,7 +2340,7 @@ begin
   AStream.WriteWord(WordToLE(hash));
 end;
 
-procedure TsSpreadBIFF2Writer.WriteRow(AStream: TStream; ASheet: TsWorksheet;
+procedure TsSpreadBIFF2Writer.WriteRow(AStream: TStream; ASheet: TsBasicWorksheet;
   ARowIndex, AFirstColIndex, ALastColIndex: Cardinal; ARow: PRow);
 var
   containsXF: Boolean;
@@ -2329,6 +2348,8 @@ var
   auto: Boolean;
   w: Word;
   xf: Word;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
   if (ARowIndex >= FLimitations.MaxRowCount) or
      (AFirstColIndex >= FLimitations.MaxColCount) or
@@ -2336,6 +2357,9 @@ begin
   then
     exit;
 
+  book := FWorkbook as TsWorkbook;
+  sheet := ASheet as TsWorksheet;
+
   containsXF := (ARow <> nil) and (ARow^.FormatIndex > 0);
 
   { BIFF record header }
@@ -2353,12 +2377,12 @@ begin
   auto := true;
   { Row height (in twips, 1/20 point) and info on custom row height }
   if (ARow = nil) or (ARow^.RowHeightType = rhtDefault) then
-    rowheight := PtsToTwips(ASheet.ReadDefaultRowHeight(suPoints))
+    rowheight := PtsToTwips(sheet.ReadDefaultRowHeight(suPoints))
   else
   if (ARow^.Height = 0) then
     rowheight := 0
   else begin
-    rowheight := PtsToTwips(FWorkbook.ConvertUnits(ARow^.Height, FWorkbook.Units, suPoints));
+    rowheight := PtsToTwips(book.ConvertUnits(ARow^.Height, book.Units, suPoints));
     auto := ARow^.RowHeightType <> rhtCustom;
   end;
   w := rowheight and $7FFF;
diff --git a/components/fpspreadsheet/source/common/xlsbiff5.pas b/components/fpspreadsheet/source/common/xlsbiff5.pas
index caf53610e..45a6989a1 100644
--- a/components/fpspreadsheet/source/common/xlsbiff5.pas
+++ b/components/fpspreadsheet/source/common/xlsbiff5.pas
@@ -58,7 +58,7 @@ interface
 
 uses
   Classes, SysUtils, fpcanvas, lconvencoding,
-  fpsTypes, fpspreadsheet,
+  fpsTypes,
   xlscommon,
   {$ifdef USE_NEW_OLE}
   fpolebasic,
@@ -83,7 +83,7 @@ type
     procedure ReadRPNSheetIndex(AStream: TStream; out ADocumentURL: String;
       out ASheet1, ASheet2: Integer); override;
     procedure ReadRSTRING(AStream: TStream);
-    procedure ReadStandardWidth(AStream: TStream; ASheet: TsWorksheet);
+    procedure ReadStandardWidth(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure ReadStringRecord(AStream: TStream); override;
     procedure ReadWorkbookGlobals(AStream: TStream); override;
     procedure ReadWorksheet(AStream: TStream); override;
@@ -100,14 +100,14 @@ type
   protected
     function FunctionSupported(AExcelCode: Integer; const AFuncName: String): Boolean; override;
     procedure InternalWriteToStream(AStream: TStream);
-    procedure PopulatePalette(AWorkbook: TsWorkbook); override;
+    procedure PopulatePalette(AWorkbook: TsBasicWorkbook); override;
     { Record writing methods }
     procedure WriteBOF(AStream: TStream; ADataType: Word);
-    function  WriteBoundsheet(AStream: TStream; AWorkSheet: TsWorksheet): Int64;
-    procedure WriteDefinedName(AStream: TStream; AWorksheet: TsWorksheet;
+    function  WriteBoundsheet(AStream: TStream; AWorkSheet: TsBasicWorksheet): Int64;
+    procedure WriteDefinedName(AStream: TStream; AWorksheet: TsBasicWorksheet;
        const AName: String; AIndexToREF, ASheetIndex: Word;
        AKind: TsBIFFExternKind); override;
-    procedure WriteDimensions(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteDimensions(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteEOF(AStream: TStream);
     procedure WriteFont(AStream: TStream;  AFont: TsFont);
     procedure WriteFonts(AStream: TStream);
@@ -117,16 +117,17 @@ type
     procedure WriteIndex(AStream: TStream);
     procedure WriteLABEL(AStream: TStream; const ARow, ACol: Cardinal;
       const AValue: string; ACell: PCell); override;
-    procedure WriteLocalLinkTable(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteLocalLinkTable(AStream: TStream;
+      AWorksheet: TsBasicWorksheet);
     function WriteRPNSheetIndex(AStream: TStream; ADocumentURL: String;
       ASheet1, ASheet2: Integer): Word; override;
     procedure WriteStringRecord(AStream: TStream; AString: String); override;
     procedure WriteStyle(AStream: TStream);
-    procedure WriteWindow2(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteWindow2(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure WriteXF(AStream: TStream; AFormatRecord: PsCellFormat;
       XFType_Prot: Byte = 0); override;
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     { General writing methods }
     procedure WriteToFile(const AFileName: string;
       const AOverwriteExisting: Boolean = False; AParams: TsStreamParams = []); override;
@@ -228,7 +229,8 @@ uses
   LazLogger,
  {$ENDIF}
   Math,
-  fpsStrings, fpsReaderWriter, fpsStreams, fpsPalette, fpsNumFormat, xlsconst;
+  fpsStrings, fpspreadsheet, fpsReaderWriter, fpsStreams,
+  fpsPalette, fpsNumFormat, xlsconst;
 
 const
    { Excel record IDs }
@@ -397,7 +399,9 @@ begin
   SetLength(s, len);
   AStream.ReadBuffer(s[1], len*SizeOf(AnsiChar));
 
-  sheet := FWorkbook.AddWorksheet(ConvertEncoding(s, FCodePage, EncodingUTF8), true);
+  sheet := (FWorkbook as TsWorkbook).AddWorksheet(
+    ConvertEncoding(s, FCodePage, EncodingUTF8), true
+  );
   if sheetState <> 0 then
     sheet.Options := sheet.Options + [soHidden];
 end;
@@ -513,7 +517,7 @@ var
   RecordType: Word;
   CurStreamPos: Int64;
 begin
-  FWorksheet := FWorkbook.GetWorksheetByIndex(FCurSheetIndex);
+  FWorksheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(FCurSheetIndex);
   while (not SectionEOF) do
   begin
     { Read the record header }
@@ -703,15 +707,20 @@ var
   rtfRuns: TBiff5_RichTextFormattingRuns;
   fntIndex: Integer;
   fnt: TsFont;
+  sheet: TsWorksheet;
+  book: TsWorkbook;
 begin
+  sheet := TsWorksheet(FWorksheet);
+  book := TsWorkbook(FWorkbook);
+
   ReadRowColXF(AStream, ARow, ACol, XF);
 
   { Create cell }
   if FIsVirtualMode then begin
-    InitCell(FWorksheet, ARow, ACol, FVirtualCell);
+    InitCell(sheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := sheet.AddCell(ARow, ACol);
 
   { Read data string (Byte string with 16-bit length) }
   L := WordLEtoN(AStream.ReadWord);
@@ -720,7 +729,7 @@ begin
 
   { Save the data string to cell }
   valueStr := ConvertEncoding(ansistr, FCodePage, encodingUTF8);
-  FWorksheet.WriteText(cell, valuestr);
+  sheet.WriteText(cell, valuestr);
 
   { Read rich-text formatting runs }
   B := AStream.ReadByte;
@@ -734,9 +743,9 @@ begin
     // in the file is different from the font index stored by the workbook.
     fntIndex := rtfRuns[i].FontIndex;
     fnt := TsFont(FFontList[fntIndex]);
-    fntIndex := FWorkbook.FindFont(fnt.FontName, fnt.Size, fnt.Style,fnt.Color, fnt.Position);
+    fntIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style,fnt.Color, fnt.Position);
     if fntIndex = -1 then
-      fntIndex := FWorkbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+      fntIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
     cell^.RichTextParams[i].FontIndex := fntIndex;
     // Hyperlink index (not used here)
     cell^.RichTextParams[i].HyperlinkIndex := -1;
@@ -746,20 +755,21 @@ begin
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    book.OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 { Reads the default column width that is used when a bit in the GCW bit structure
   is set for the corresponding column. The GCW is ignored here. The column
   width read from the STANDARDWIDTH record overrides the one from the
   DEFCOLWIDTH record. }
-procedure TsSpreadBIFF5Reader.ReadStandardWidth(AStream: TStream; ASheet: TsWorksheet);
+procedure TsSpreadBIFF5Reader.ReadStandardWidth(AStream: TStream;
+  ASheet: TsBasicWorksheet);
 var
   w: Word;
 begin
   // read width in 1/256 of the width of "0" character
   w := WordLEToN(AStream.ReadWord);
-  ASheet.WriteDefaultRowHeight(w / 256, suChars);
+  (ASheet as TsWorksheet).WriteDefaultRowHeight(w / 256, suChars);
 end;
 
 { Reads a STRING record which contains the result of string formula. }
@@ -777,7 +787,9 @@ begin
       FIncompletecell^.UTF8StringValue := ConvertEncoding(s, FCodePage, encodingUTF8);
       FIncompleteCell^.ContentType := cctUTF8String;
       if FIsVirtualMode then
-        Workbook.OnReadCellData(Workbook, FIncompleteCell^.Row, FIncompleteCell^.Col, FIncompleteCell);
+        (Workbook as TsWorkbook).OnReadCellData(
+          Workbook, FIncompleteCell^.Row, FIncompleteCell^.Col, FIncompleteCell
+        );
     end;
   end;
   FIncompleteCell := nil;
@@ -823,8 +835,10 @@ var
   dw: DWord;
   fill: Word;
   fs: TsFillStyle;
-//  fnt: TsFont;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   InitFormatRecord(fmt);
   fmt.ID := FCellFormatList.Count;
 
@@ -843,8 +857,8 @@ begin
     // "General" (NumFormatIndex = 0) not stored in workbook's NumFormatList
     if (rec.NumFormatIndex > 0) and not SameText(nfs, 'General') then
     begin
-      fmt.NumberFormatIndex := Workbook.AddNumberFormat(nfs);
-      nfParams := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+      fmt.NumberFormatIndex := book.AddNumberFormat(nfs);
+      nfParams := book.GetNumberFormat(fmt.NumberFormatIndex);
       fmt.NumberFormat := nfParams.NumFormat;
       fmt.NumberFormatStr := nfs;
       Include(fmt.UsedFormattingFields, uffNumberFormat);
@@ -1090,7 +1104,7 @@ begin
   if FFontList.Count = 4 then FFontList.Add(nil);
 
   if isDefaultFont then
-    FWorkbook.SetDefaultFont(font.FontName, font.Size);
+    (FWorkbook as TsWorkbook).SetDefaultFont(font.FontName, font.Size);
 end;
 
 // Read the FORMAT record for formatting numerical data
@@ -1149,17 +1163,17 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
 
   { Save the data }
   valueStr := ConvertEncoding(ansistr, FCodePage, encodingUTF8);
-  FWorksheet.WriteText(cell, valueStr); //ISO_8859_1ToUTF8(ansistr));
+  (FWorksheet as TsWorksheet).WriteText(cell, valueStr); //ISO_8859_1ToUTF8(ansistr));
 
   { Add attributes }
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 
@@ -1167,7 +1181,7 @@ end;
 {                           TsSpreadBIFF5Writer                                }
 {------------------------------------------------------------------------------}
 
-constructor TsSpreadBIFF5Writer.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFF5Writer.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   FDateMode := Excel5Settings.DateMode;
@@ -1192,14 +1206,17 @@ var
   sheetPos: array of Int64;
   i: Integer;
   pane: Byte;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   { Write workbook globals }
   WriteBOF(AStream, INT_BOF_WORKBOOK_GLOBALS);
 
   WriteCODEPAGE(AStream, FCodePage);
   WriteWindowProtect(AStream, bpLockWindows in Workbook.Protection);
   WritePROTECT(AStream, bpLockStructure in Workbook.Protection);
-  WritePASSWORD(AStream, Workbook.CryptoInfo);
+  WritePASSWORD(AStream, book.CryptoInfo);
   WriteGlobalLinkTable(AStream);
   WriteDefinedNames(AStream);
   WriteWINDOW1(AStream);
@@ -1210,17 +1227,17 @@ begin
   WriteStyle(AStream);
 
   // A BOUNDSHEET for each worksheet
-  SetLength(sheetPos, Workbook.GetWorksheetCount);
-  for i := 0 to Workbook.GetWorksheetCount - 1 do
-    sheetPos[i] := WriteBoundsheet(AStream, Workbook.GetWorksheetByIndex(i));
+  SetLength(sheetPos, book.GetWorksheetCount);
+  for i := 0 to book.GetWorksheetCount - 1 do
+    sheetPos[i] := WriteBoundsheet(AStream, book.GetWorksheetByIndex(i));
 
   WriteEOF(AStream);
 
   { Write each worksheet }
 
-  for i := 0 to Workbook.GetWorksheetCount - 1 do
+  for i := 0 to book.GetWorksheetCount - 1 do
   begin
-    FWorksheet := Workbook.GetWorksheetByIndex(i);
+    FWorksheet := book.GetWorksheetByIndex(i);
 
     { First goes back and writes the position of the BOF of the
       sheet on the respective BOUNDSHEET record }
@@ -1255,7 +1272,7 @@ begin
         WritePROTECT(AStream, true);
 //          WriteScenarioProtect(AStream);
         WriteObjectProtect(AStream, FWorksheet);
-        WritePASSWORD(AStream, FWorksheet.CryptoInfo);
+        WritePASSWORD(AStream, TsWorksheet(FWorksheet).CryptoInfo);
       end;
 
       WriteDefaultColWidth(AStream, FWorksheet);
@@ -1271,7 +1288,7 @@ begin
         WriteVirtualCells(AStream, FWorksheet)
       else begin
         WriteRows(AStream, FWorksheet);
-        WriteCellsToStream(AStream, FWorksheet.Cells);
+        WriteCellsToStream(AStream, TsWorksheet(FWorksheet).Cells);
       end;
 
     WriteEOF(AStream);
@@ -1287,7 +1304,7 @@ end;
   BIFF8 begins with the 8 default colors which are duplicated. Then the user
   colors follow up to a max of total 64 entries.
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFF5Writer.PopulatePalette(AWorkbook: TsWorkbook);
+procedure TsSpreadBIFF5Writer.PopulatePalette(AWorkbook: TsBasicWorkbook);
 var
   i: Integer;
 begin
@@ -1405,7 +1422,7 @@ end;
             of the BOF of this sheet should be written (4 bytes size).
 -------------------------------------------------------------------------------}
 function TsSpreadBIFF5Writer.WriteBoundsheet(AStream: TStream;
-  AWorkSheet: TsWorksheet): Int64;
+  AWorkSheet: TsBasicWorksheet): Int64;
 var
   len: Byte;
   xlsSheetName: ansistring;
@@ -1442,8 +1459,8 @@ end;
   Writes out a DEFINEDNAMES record
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF5Writer.WriteDefinedName(AStream: TStream;
-  AWorksheet: TsWorksheet; const AName: String; AIndexToREF, ASheetIndex: Word;
-  AKind: TsBIFFExternKind);
+  AWorksheet: TsBasicWorksheet; const AName: String;
+  AIndexToREF, ASheetIndex: Word; AKind: TsBIFFExternKind);
 
   procedure WriteRangeFormula(MemStream: TMemoryStream; ARange: TsCellRange;
     AIndexToREF, ASheetIndex, ACounter: Word);
@@ -1503,42 +1520,46 @@ var
   memstream: TMemoryStream;
   rng: TsCellRange;
   j: Integer;
+  sheet: TsWorksheet;
 begin
+  sheet := AWorksheet as TsWorksheet;
+
   // Since this is a variable length record we begin by writing the formula
   // to a memory stream
   memstream := TMemoryStream.Create;
   try
     case AName of
       #06: begin  // Print range
-             for j := 0 to AWorksheet.PageLayout.NumPrintRanges-1 do
+             for j := 0 to sheet.PageLayout.NumPrintRanges-1 do
              begin
-               rng := AWorksheet.PageLayout.PrintRange[j];
+               rng := sheet.PageLayout.PrintRange[j];
                WriteRangeFormula(memstream, rng, AIndexToRef, ASheetIndex, j+1);
              end;
            end;
       #07: begin
              j := 1;
-             if AWorksheet.PageLayout.HasRepeatedCols then
+             if sheet.PageLayout.HasRepeatedCols then
              begin
-               rng.Col1 := AWorksheet.PageLayout.RepeatedCols.FirstIndex;
-               rng.Col2 := AWorksheet.PageLayout.RepeatedCols.LastIndex;
+               rng.Col1 := sheet.PageLayout.RepeatedCols.FirstIndex;
+               rng.Col2 := sheet.PageLayout.RepeatedCols.LastIndex;
                if rng.Col2 = UNASSIGNED_ROW_COL_INDEX then rng.Col2 := rng.Col1;
                rng.Row1 := 0;
                rng.Row2 := 65535;
                WriteRangeFormula(memstream, rng, AIndexToRef, ASheetIndex, j);
                inc(j);
              end;
-             if AWorksheet.PageLayout.HasRepeatedRows then
+             if sheet.PageLayout.HasRepeatedRows then
              begin
-               rng.Row1 := AWorksheet.PageLayout.RepeatedRows.FirstIndex;
-               rng.Row2 := AWorksheet.PageLayout.RepeatedRows.LastIndex;
+               rng.Row1 := sheet.PageLayout.RepeatedRows.FirstIndex;
+               rng.Row2 := sheet.PageLayout.RepeatedRows.LastIndex;
                if rng.Row2 = UNASSIGNED_ROW_COL_INDEX then rng.Row2 := rng.Row1;
                rng.Col1 := 0;
                rng.Col2 := 255;
                WriteRangeFormula(memstream, rng, AIndexToRef, ASheetIndex, j);
              end;
            end;
-      else raise EFPSpreadsheetWriter.Create('Name not supported');
+      else
+           raise EFPSpreadsheetWriter.Create('Name not supported');
     end;  // case
 
     { BIFF record header }
@@ -1598,7 +1619,8 @@ end;
 
   See bug 18886: excel5 files are truncated when imported
 --------------------------------------------------------------------------------}
-procedure TsSpreadBIFF5Writer.WriteDimensions(AStream: TStream; AWorksheet: TsWorksheet);
+procedure TsSpreadBIFF5Writer.WriteDimensions(AStream: TStream;
+  AWorksheet: TsBasicWorksheet);
 var
   rec: TBIFF5_DimensionsRecord;
   firstCol, lastCol, firstRow, lastRow: Cardinal;
@@ -1704,8 +1726,8 @@ procedure TsSpreadBiff5Writer.WriteFonts(AStream: TStream);
 var
   i: Integer;
 begin
-  for i:=0 to Workbook.GetFontCount-1 do
-    WriteFont(AStream, Workbook.GetFont(i));
+  for i:=0 to TsWorkbook(Workbook).GetFontCount-1 do
+    WriteFont(AStream, TsWorkbook(Workbook).GetFont(i));
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -1907,7 +1929,7 @@ end;
   internal 3D references to other sheets
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF5Writer.WriteLocalLinkTable(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   i, n: Integer;
   externSheetList: TsBIFFExternSheetList;
@@ -1993,7 +2015,7 @@ begin
 
   externSheetList := FLinkLists.GetLocalLinks(FWorksheet);
 
-  s := FWorkbook.GetWorksheetByIndex(ASheet1).Name;
+  s := (FWorkbook as TsWorkbook).GetWorksheetByIndex(ASheet1).Name;
   externSheetIdx := externSheetList.IndexOfSheet(s);
 
   if ASheet2 = -1 then
@@ -2065,11 +2087,14 @@ end;
   Writes an Excel 5 WINDOW2 record
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF5Writer.WriteWindow2(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   Options: Word;
+  book: TsWorkbook;
   actSheet: TsWorksheet;
 begin
+  book := FWorkbook as TsWorkbook;
+
   { BIFF Record header }
   WriteBiffHeader(AStream, INT_EXCEL_ID_WINDOW2, 10);
 
@@ -2087,13 +2112,15 @@ begin
     Options := Options or MASK_WINDOW2_OPTION_SHOW_GRID_LINES;
   if (soShowHeaders in ASheet.Options) then
     Options := Options or MASK_WINDOW2_OPTION_SHOW_SHEET_HEADERS;
-  if (soHasFrozenPanes in ASheet.Options) and ((ASheet.LeftPaneWidth > 0) or (ASheet.TopPaneHeight > 0)) then
+  if (soHasFrozenPanes in ASheet.Options) and
+    ((TsWorksheet(ASheet).LeftPaneWidth > 0) or (TsWorksheet(ASheet).TopPaneHeight > 0))
+  then
     Options := Options or MASK_WINDOW2_OPTION_PANES_ARE_FROZEN;
-  if (ASheet.BiDiMode = bdRTL) then
+  if (TsWorksheet(ASheet).BiDiMode = bdRTL) then
     Options := Options or MASK_WINDOW2_OPTION_COLUMNS_RIGHT_TO_LEFT;
-  if FWorkbook.ActiveWorksheet <> nil then
-    actSheet := FWorkbook.ActiveWorksheet else
-    actSheet := Fworkbook.GetWorksheetByIndex(0);
+  if book.ActiveWorksheet <> nil then
+    actSheet := book.ActiveWorksheet else
+    actSheet := book.GetWorksheetByIndex(0);
   if (ASheet = actSheet) then
     Options := Options or MASK_WINDOW2_OPTION_SHEET_ACTIVE or MASK_WINDOW2_OPTION_SHEET_SELECTED;
 
@@ -2160,7 +2187,7 @@ begin
   j := 0;
   if (AFormatRecord <> nil) and (uffNumberFormat in AFormatRecord^.UsedFormattingFields)
   then begin
-    nfParams := Workbook.GetNumberFormat(AFormatRecord^.NumberFormatIndex);
+    nfParams := TsWorkbook(Workbook).GetNumberFormat(AFormatRecord^.NumberFormatIndex);
     nfs := nfParams.NumFormatStr;
     j := NumFormatList.IndexOf(nfs);
     if j = -1 then j := 0;
diff --git a/components/fpspreadsheet/source/common/xlsbiff8.pas b/components/fpspreadsheet/source/common/xlsbiff8.pas
index 031dc4d15..f687ab337 100644
--- a/components/fpspreadsheet/source/common/xlsbiff8.pas
+++ b/components/fpspreadsheet/source/common/xlsbiff8.pas
@@ -55,7 +55,7 @@ interface
 
 uses
   Classes, SysUtils, fpcanvas, DateUtils, contnrs, lazutf8,
-  fpstypes, fpspreadsheet, xlscommon,
+  fpstypes, xlscommon,
   {$ifdef USE_NEW_OLE}
   fpolebasic,
   {$else}
@@ -175,7 +175,7 @@ type
     procedure ReadWorksheet(AStream: TStream); override;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
     procedure ReadFromStream(AStream: TStream;
       APassword: String = ''; AParams: TsStreamParams = []); override;
@@ -203,19 +203,20 @@ type
     function IndexOfSharedString(const AText: String;
       const ARichTextParams: TsRichTextParams): Integer;
     procedure InternalWriteToStream(AStream: TStream);
-    procedure PopulatePalette(AWorkbook: TsWorkbook); override;
-    procedure PopulateSharedStringTable(AWorkbook: TsWorkbook);
+    procedure PopulatePalette(AWorkbook: TsBasicWorkbook); override;
+    procedure PopulateSharedStringTable(AWorkbook: TsBasicWorkbook);
 
     { Record writing methods }
     procedure WriteBOF(AStream: TStream; ADataType: Word);
-    function  WriteBoundsheet(AStream: TStream; AWorksheet: TsWorksheet): Int64;
+    function  WriteBoundsheet(AStream: TStream;
+      AWorksheet: TsBasicWorksheet): Int64;
     procedure WriteComment(AStream: TStream; ACell: PCell); override;
-    procedure WriteComments(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteDefinedName(AStream: TStream; AWorksheet: TsWorksheet;
+    procedure WriteComments(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteDefinedName(AStream: TStream; AWorksheet: TsBasicWorksheet;
        const AName: String; AIndexToREF, ASheetIndex: Word;
        AKind: TsBIFFExternKind);
     procedure WriteDefinedNames(AStream: TStream);
-    procedure WriteDimensions(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteDimensions(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteEOF(AStream: TStream);
     procedure WriteEXTERNBOOK(AStream: TStream; AUrl: String);
     procedure WriteEXTERNSHEET(AStream: TStream);
@@ -225,14 +226,14 @@ type
       ANumFormatIndex: Integer); override;
     procedure WriteHeaderFooter(AStream: TStream; AIsHeader: Boolean); override;
     procedure WriteHyperlink(AStream: TStream; AHyperlink: PsHyperlink;
-      AWorksheet: TsWorksheet);
-    procedure WriteHyperlinks(AStream: TStream; AWorksheet: TsWorksheet);
+      AWorksheet: TsBasicWorksheet);
+    procedure WriteHyperlinks(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteHyperlinkToolTip(AStream: TStream; const ARow, ACol: Cardinal;
       const ATooltip: String);
     procedure WriteINDEX(AStream: TStream);
     procedure WriteLABEL(AStream: TStream; const ARow, ACol: Cardinal;
       const AValue: string; ACell: PCell); override;
-    procedure WriteMergedCells(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteMergedCells(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteMSODrawing1(AStream: TStream; ANumShapes: Word; AComment: PsComment);
     procedure WriteMSODrawing2(AStream: TStream; AComment: PsComment; AObjID: Word);
     procedure WriteMSODrawing2_Data(AStream: TStream; AComment: PsComment; AShapeID: Word);
@@ -255,11 +256,11 @@ type
     procedure WriteSTRINGRecord(AStream: TStream; AString: string); override;
     procedure WriteSTYLE(AStream: TStream);
     procedure WriteTXO(AStream: TStream; AComment: PsComment);
-    procedure WriteWINDOW2(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteWINDOW2(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure WriteXF(AStream: TStream; AFormatRecord: PsCellFormat;
       XFType_Prot: Byte = 0); override;
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
     { General writing methods }
     procedure WriteToFile(const AFileName: string;
@@ -363,7 +364,7 @@ uses
  {$ENDIF}
   Math, lconvencoding, LazFileUtils, URIParser,
   fpsStrings, {%H-}fpsPatches, fpsStreams, fpsReaderWriter, fpsPalette,
-  fpsNumFormat, fpsExprParser, xlsEscher;
+  fpspreadsheet, fpsNumFormat, fpsExprParser, xlsEscher;
 
 const
    { Excel record IDs }
@@ -769,7 +770,7 @@ end;
 {------------------------------------------------------------------------------}
 {                              TsSpreadBIFF8Reader                             }
 {------------------------------------------------------------------------------}
-constructor TsSpreadBIFF8Reader.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFF8Reader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited;
   InitBIFF8Limitations(FLimitations);
@@ -858,7 +859,7 @@ begin
     if TBIFF8Comment(FCommentList[i]).ID = commentID then
     begin
       commentText := TBIFF8Comment(FCommentList[i]).Text;
-      FWorksheet.WriteComment(r, c, commentText);
+      TsWorksheet(FWorksheet).WriteComment(r, c, commentText);
       exit;
     end;
 end;
@@ -1158,7 +1159,7 @@ var
   RecordType: Word;
   CurStreamPos: Int64;
 begin
-  FWorksheet := FWorkbook.GetWorksheetByIndex(FCurSheetIndex);
+  FWorksheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(FCurSheetIndex);
   while (not SectionEOF) do
   begin
     { Read the record header }
@@ -1269,7 +1270,7 @@ begin
   { Read string with flags }
   wideName := ReadWideString(AStream, len, rtParams);
 
-  sheet := FWorkbook.AddWorksheet(UTF8Encode(widename), true);
+  sheet := (FWorkbook as TsWorkbook).AddWorksheet(UTF8Encode(widename), true);
   if sheetState <> 0 then
     sheet.Options := sheet.Options + [soHidden];
 end;
@@ -1357,7 +1358,10 @@ var
   rtParams: TsRichTextParams;
   fntIndex: Integer;
   fnt: TsFont;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   { BIFF Record data: Row, Column, XF Index }
   ReadRowColXF(AStream, ARow, ACol, XF);
 
@@ -1372,9 +1376,9 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);        // "virtual" cell
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);    // "real" cell
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);    // "real" cell
 
-  FWorksheet.WriteText(cell, UTF16ToUTF8(wideStrValue));
+  (FWorksheet as TsWorksheet).WriteText(cell, UTF16ToUTF8(wideStrValue));
 
   { Add attributes }
   ApplyCellFormatting(cell, XF);
@@ -1389,9 +1393,9 @@ begin
       // Font index of new format - need to adjust index!
       fntIndex := rtParams[i].FontIndex;
       fnt := TsFont(FFontList[fntIndex]);
-      fntIndex := FWorkbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+      fntIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
       if fntIndex = -1 then
-        fntIndex := FWorkbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+        fntIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
       cell^.RichTextParams[i].FontIndex := fntIndex;
       // Hyperlink index, not used here
       cell^.RichTextParams[i].HyperlinkIndex := -1;
@@ -1399,7 +1403,7 @@ begin
   end;
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    book.OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 procedure TsSpreadBIFF8Reader.ReadMergedCells(const AStream: TStream);
@@ -1416,7 +1420,7 @@ begin
     // Read range
     AStream.ReadBuffer(rng, SizeOf(rng));
     // Transfer cell range to worksheet
-    FWorksheet.MergeCells(
+    (FWorksheet as TsWorksheet).MergeCells(
       WordLEToN(rng.Row1), WordLEToN(rng.Col1),
       WordLEToN(rng.Row2), WordLEToN(rng.Col2)
     );
@@ -1629,7 +1633,10 @@ var
   rtfRuns: TBiff8_RichTextFormattingRuns;
   fntIndex: Integer;
   fnt: TsFont;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   { BIFF Record data: Row, Column, XF Index }
   ReadRowColXF(AStream, ARow, ACol, XF);
 
@@ -1644,10 +1651,10 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);        // "virtual" cell
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);    // "real" cell
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);    // "real" cell
 
   { Save the data string}
-  FWorksheet.WriteText(cell, UTF16ToUTF8(wideStrValue));
+  (FWorksheet as TsWorksheet).WriteText(cell, UTF16ToUTF8(wideStrValue));
 
   { Read rich-text formatting runs }
   L := WordLEToN(AStream.ReadWord);
@@ -1660,9 +1667,9 @@ begin
     // necessarily the same as the index used by the workbook!
     fntIndex := WordLEToN(rtfRuns[j].FontIndex);
     fnt := TsFont(FFontList[fntIndex]);
-    fntIndex := FWorkbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+    fntIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
     if fntIndex = -1 then
-      fntIndex := FWorkbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+      fntIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
     cell^.RichTextParams[j].FontIndex := fntIndex;
     // Index of the first character using this font: 0-based in file, 1-based in fps
     cell^.RichTextParams[j].FirstIndex := WordLEToN(rtfRuns[j].FirstIndex) + 1;
@@ -1674,7 +1681,7 @@ begin
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    book.OnReadCellData(book, ARow, ACol, cell);
 end;
 
 procedure TsSpreadBIFF8Reader.ReadSST(const AStream: TStream);
@@ -1773,7 +1780,10 @@ var
   rtParams: TsRichTextParams;
   fnt: TsFont;
   fntIndex: Integer;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   rec.Row := 0;  // to silence the compiler...
 
   { Read entire record, starting at Row }
@@ -1794,9 +1804,9 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := (FWorksheet as TsWorksheet).AddCell(ARow, ACol);
 
-  FWorksheet.WriteText(cell, FSharedStringTable.Strings[SSTIndex]);
+  (FWorksheet as TsWorksheet).WriteText(cell, FSharedStringTable.Strings[SSTIndex]);
 
   { Add attributes }
   ApplyCellFormatting(cell, XF);
@@ -1814,16 +1824,16 @@ begin
       cell^.RichTextParams[i].FirstIndex := rtParams[i].FirstIndex;
       fntIndex := rtParams[i].FontIndex;
       fnt := TsFont(FFontList[fntIndex]);
-      fntIndex := FWorkbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+      fntIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
       if fntIndex = -1 then
-        fntIndex := FWorkbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+        fntIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
       cell^.RichTextParams[i].FontIndex := fntIndex;
       cell^.RichTextParams[i].HyperlinkIndex := -1;
     end;
   end;
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    book.OnReadCellData(book, ARow, ACol, cell);
 end;
 
 { Helper function for reading a string with 8-bit length. }
@@ -1841,13 +1851,16 @@ end;
 procedure TsSpreadBIFF8Reader.ReadStringRecord(AStream: TStream);
 var
   wideStr: WideString;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   wideStr := ReadWideString(AStream, false);
   if (FIncompleteCell <> nil) and (wideStr <> '') then begin
     FIncompleteCell^.UTF8StringValue := UTF8Encode(wideStr);
     FIncompleteCell^.ContentType := cctUTF8String;
     if FIsVirtualMode then
-      Workbook.OnReadCellData(Workbook, FIncompleteCell^.Row, FIncompleteCell^.Col, FIncompleteCell);
+      book.OnReadCellData(book, FIncompleteCell^.Row, FIncompleteCell^.Col, FIncompleteCell);
   end;
   FIncompleteCell := nil;
 end;
@@ -1875,7 +1888,10 @@ var
   nfs: String;
   nfParams: TsNumFormatParams;
   iclr: Integer;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   InitFormatRecord(fmt);
   fmt.ID := FCellFormatList.Count;
 
@@ -1894,8 +1910,8 @@ begin
     // "General" (NumFormatIndex = 0) not stored in workbook's NumFormatList
     if (rec.NumFormatIndex > 0) and not SameText(nfs, 'General') then
     begin
-      fmt.NumberFormatIndex := Workbook.AddNumberFormat(nfs);
-      nfParams := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+      fmt.NumberFormatIndex := book.AddNumberFormat(nfs);
+      nfParams := book.GetNumberFormat(fmt.NumberFormatIndex);
       if nfParams <> nil then
       begin
         fmt.NumberFormat := nfParams.NumFormat;
@@ -2265,7 +2281,7 @@ begin
   if FFontList.Count = 4 then FFontList.Add(nil);
 
   if isDefaultFont then
-    Workbook.SetDefaultFont(font.FontName, font.Size);
+    (Workbook as TsWorkbook).SetDefaultFont(font.FontName, font.Size);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2312,10 +2328,11 @@ begin
 
   len := WordLEToN(AStream.ReadWord);
   s := ReadWideString(AStream, len, rtParams);
-  if AIsHeader then
-    FWorksheet.PageLayout.Headers[1] := UTF8Encode(s)
-  else
-    FWOrksheet.PageLayout.Footers[1] := UTF8Encode(s);
+  with (FWorksheet as TsWorksheet).Pagelayout do
+    if AIsHeader then
+      Headers[1] := UTF8Encode(s)
+    else
+      Footers[1] := UTF8Encode(s);
 
   { Options poDifferentFirst and poDifferentOddEvent are not used, BIFF supports
     only common headers/footers }
@@ -2461,7 +2478,7 @@ begin
   // Add hyperlink(s) to worksheet
   for row := row1 to row2 do
     for col := col1 to col2 do
-      FWorksheet.WriteHyperlink(row, col, link);
+      TsWorksheet(FWorksheet).WriteHyperlink(row, col, link);
 end;
 
 
@@ -2476,6 +2493,7 @@ var
   row1, col1, row2, col2: Word;
   hyperlink: PsHyperlink;
   numbytes: Integer;
+  sheet: TsWorksheet;
 begin
   { Record type; this matches the BIFF record type }
   AStream.ReadWord;
@@ -2494,7 +2512,8 @@ begin
   txt := UTF8Encode(wideStr);
 
   { Add tooltip to hyperlinks }
-  for hyperlink in FWorksheet.Hyperlinks.GetRangeEnumerator(row1, col1, row2, col2) do
+  sheet := FWorksheet as TsWorksheet;
+  for hyperlink in sheet.Hyperlinks.GetRangeEnumerator(row1, col1, row2, col2) do
     hyperlink^.ToolTip := txt;
 end;
 
@@ -2506,7 +2525,7 @@ end;
 {@@ ----------------------------------------------------------------------------
   Constructor of the Excel 8 writer
 -------------------------------------------------------------------------------}
-constructor TsSpreadBIFF8Writer.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFF8Writer.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   InitBiff8Limitations(FLimitations);
@@ -2576,6 +2595,7 @@ procedure TsSpreadBIFF8Writer.CollectExternData;
   end;
 
 var
+  book: TsWorkbook;
   sheet: TsWorksheet;
   i: Integer;
   writeIt: Boolean;
@@ -2586,9 +2606,11 @@ begin
   FBiff8ExternBooks := TsBIFF8ExternBookList.Create;
   FBiff8ExternSheets := TsBIFF8ExternSheetList.Create(FBiff8ExternBooks);
 
+  book := FWorkbook as TsWorkbook;
+
   { Add sheets used in print ranges, repeated cols or repeated rows }
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+  for i:=0 to book.GetWorksheetCount-1 do begin
+    sheet := book.GetWorksheetByIndex(i);
     with sheet.PageLayout do
       writeIt := (NumPrintRanges > 0) or HasRepeatedCols or HasRepeatedRows;
     if writeIt then
@@ -2596,9 +2618,9 @@ begin
   end;
 
   { Add sheets related to 3d references of all sheets }
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i);
     DoCollectForSheet(sheet);
   end;
 
@@ -2632,7 +2654,7 @@ Begin
   Bit 9: 0 = Print notes as displayed; 1 = Print notes at end of sheet
   Bit 11-10:  00 = Print errors as displayed; 1 = Do not print errors
               2 = Print errors as “--”; 3 = Print errors as “#N/A” }
-  if poCommentsAtEnd in FWorksheet.PageLayout.Options then
+  if poCommentsAtEnd in (FWorksheet as TsWorksheet).PageLayout.Options then
     Result := Result or $0200;
 end;
 
@@ -2671,7 +2693,9 @@ var
   sheetPos: array of Int64;
   i: Integer;
   pane: Byte;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
   CollectExternData;
 
   { Write workbook globals }
@@ -2679,7 +2703,7 @@ begin
   WriteCodePage(AStream, 'ucs2le'); // = utf-16
   WriteWindowProtect(AStream, bpLockWindows in Workbook.Protection);
   WritePROTECT(AStream, bpLockStructure in Workbook.Protection);
-  WritePASSWORD(AStream, Workbook.CryptoInfo);
+  WritePASSWORD(AStream, book.CryptoInfo);
   WriteWINDOW1(AStream);
   WriteFonts(AStream);
   WriteNumFormats(AStream);
@@ -2688,9 +2712,9 @@ begin
   WriteStyle(AStream);
 
   // A BOUNDSHEET for each worksheet
-  SetLength(sheetPos, Workbook.GetWorksheetCount);
-  for i := 0 to Workbook.GetWorksheetCount - 1 do
-    sheetPos[i] := WriteBoundsheet(AStream, Workbook.GetWorksheetByIndex(i));
+  SetLength(sheetPos, book.GetWorksheetCount);
+  for i := 0 to book.GetWorksheetCount - 1 do
+    sheetPos[i] := WriteBoundsheet(AStream, book.GetWorksheetByIndex(i));
 
   WriteEXTERNBOOK(AStream, '');
   WriteEXTERNSHEET(AStream);
@@ -2700,9 +2724,9 @@ begin
   WriteEOF(AStream);
 
   { Write each worksheet }
-  for i := 0 to Workbook.GetWorksheetCount - 1 do
+  for i := 0 to book.GetWorksheetCount - 1 do
   begin
-    FWorksheet := Workbook.GetWorksheetByIndex(i);
+    FWorksheet := book.GetWorksheetByIndex(i);
 
     { First goes back and writes the position of the BOF of the
       sheet on the respective BOUNDSHEET record }
@@ -2734,7 +2758,7 @@ begin
         WritePROTECT(AStream, true);
 //        WriteScenarioProtect(AStream);
         WriteObjectProtect(AStream, FWorksheet);
-        WritePASSWORD(AStream, FWorksheet.CryptoInfo);
+        WritePASSWORD(AStream, (FWorksheet as TsWorksheet).CryptoInfo);
       end;
 
       WriteDefaultColWidth(AStream, FWorksheet);
@@ -2745,7 +2769,7 @@ begin
         WriteVirtualCells(AStream, FWorksheet)
       else begin
         WriteRows(AStream, FWorksheet);
-        WriteCellsToStream(AStream, FWorksheet.Cells);
+        WriteCellsToStream(AStream, (FWorksheet as TsWorksheet).Cells);
         WriteComments(AStream, FWorksheet);
       end;
 
@@ -2770,7 +2794,7 @@ end;
   BIFF8 begins with the 8 default colors which are duplicated. Then the user
   colors follow up to a max of total 64 entries.
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFF8Writer.PopulatePalette(AWorkbook: TsWorkbook);
+procedure TsSpreadBIFF8Writer.PopulatePalette(AWorkbook: TsBasicWorkbook);
 var
   i: Integer;
 begin
@@ -2791,18 +2815,19 @@ end;
 {@@ ----------------------------------------------------------------------------
   Collects all strings of the workbook in the SharedStringTable
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFF8Writer.PopulateSharedStringTable(AWorkbook: TsWorkbook);
+procedure TsSpreadBIFF8Writer.PopulateSharedStringTable(AWorkbook: TsBasicWorkbook);
 var
   i, idx: Integer;
   cell: PCell;
   sheet: TsWorksheet;
+  book: TsWorkbook absolute AWorkbook;
 begin
   FNumStrings := 0;
   FSharedStringTable := TStringList.Create;
 
-  for i:=0 to AWorkbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := AWorkbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i);
     for cell in sheet.Cells do begin
       if (cell^.ContentType <> cctUTF8String) then
         Continue;
@@ -2925,7 +2950,7 @@ end;
             of the BOF of this sheet should be written (4 bytes size).
 -------------------------------------------------------------------------------}
 function TsSpreadBIFF8Writer.WriteBoundsheet(AStream: TStream;
-  AWorksheet: TsWorksheet): Int64;
+  AWorksheet: TsBasicWorksheet): Int64;
 var
   len: Byte;
   wideSheetName: WideString;
@@ -2972,21 +2997,24 @@ end;
   Writes all comments to the worksheet stream
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF8Writer.WriteComments(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   index: Integer;
   comment: PsComment;
+  sheet: TsWorksheet;
 begin
   exit;      // Remove after comments can be written correctly
   {$warning TODO: Fix writing of cell comments in BIFF8 (file is readable by OpenOffice, but not by Excel)}
 
+  sheet := AWorksheet as TsWorksheet;
+
   { At first we have to write all Escher-related records for all comments;
       MSODRAWING - OBJ - MSODRAWING - TXO }
   index := 1;
-  for comment in AWorksheet.Comments do
+  for comment in sheet.Comments do
   begin
     if index = 1 then
-      WriteMSODrawing1(AStream, FWorksheet.Comments.Count, comment)
+      WriteMSODrawing1(AStream, sheet.Comments.Count, comment)
     else
       WriteMSODrawing2(AStream, comment, index);
     WriteOBJ(AStream, index);
@@ -2997,7 +3025,7 @@ begin
 
   { The NOTE records for all comments follow subsequently. }
   index := 1;
-  for comment in AWorksheet.Comments do
+  for comment in sheet.Comments do
   begin
     WriteNOTE(AStream, comment, index);
     inc(index);
@@ -3009,8 +3037,8 @@ end;
   Implements only the builtin defined names for print ranges and titles!
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF8Writer.WriteDefinedName(AStream: TStream;
-  AWorksheet: TsWorksheet; const AName: String; AIndexToREF, ASheetIndex: Word;
-  AKind: TsBIFFExternKind);
+  AWorksheet: TsBasicWorksheet; const AName: String;
+  AIndexToREF, ASheetIndex: Word; AKind: TsBIFFExternKind);
 
   procedure WriteRangeFormula(MemStream: TMemoryStream; ARange: TsCellRange;
     AIndexToRef, ACounter: Word);
@@ -3042,6 +3070,8 @@ var
   memstream: TMemoryStream;
   rng: TsCellRange;
   j: Integer;
+  idx: Integer;
+  sheet: TsWorksheet absolute AWorksheet;
 
 begin
   // Since this is a variable length record we begin by writing the formula
@@ -3050,28 +3080,28 @@ begin
   try
     case AName of
       #06: begin  // Print range
-             for j := 0 to AWorksheet.PageLayout.NumPrintRanges-1 do
+             for j := 0 to sheet.PageLayout.NumPrintRanges-1 do
              begin
-               rng := AWorksheet.PageLayout.PrintRange[j];
+               rng := sheet.PageLayout.PrintRange[j];
                WriteRangeFormula(memstream, rng, AIndexToRef, j+1);
              end;
            end;
       #07: begin  // Print titles
              j := 1;
-             if AWorksheet.PageLayout.HasRepeatedCols then
+             if sheet.PageLayout.HasRepeatedCols then
              begin
-               rng.Col1 := AWorksheet.PageLayout.RepeatedCols.FirstIndex;
-               rng.Col2 := AWorksheet.PageLayout.RepeatedCols.LastIndex;
+               rng.Col1 := sheet.PageLayout.RepeatedCols.FirstIndex;
+               rng.Col2 := sheet.PageLayout.RepeatedCols.LastIndex;
                if rng.Col2 = UNASSIGNED_ROW_COL_INDEX then rng.Col2 := rng.Col1;
                rng.Row1 := 0;
                rng.Row2 := 65535;
                WriteRangeFormula(memstream, rng, AIndexToRef, j);
                inc(j);
              end;
-             if AWorksheet.PageLayout.HasRepeatedRows then
+             if sheet.PageLayout.HasRepeatedRows then
              begin
-               rng.Row1 := AWorksheet.PageLayout.RepeatedRows.FirstIndex;
-               rng.Row2 := AWorksheet.PageLayout.RepeatedRows.LastIndex;
+               rng.Row1 := sheet.PageLayout.RepeatedRows.FirstIndex;
+               rng.Row2 := sheet.PageLayout.RepeatedRows.LastIndex;
                if rng.Row2 = UNASSIGNED_ROW_COL_INDEX then rng.Row2 := rng.Row1;
                rng.Col1 := 0;
                rng.Col2 := 255;
@@ -3102,7 +3132,8 @@ begin
     AStream.WriteWord(0);
 
     { Index to sheet (1-based) }
-    AStream.WriteWord(WordToLE(FWorkbook.GetWorksheetIndex(AWorksheet)+1));
+    idx := (FWorkbook as TsWorkbook).GetWorksheetIndex(AWorksheet);
+    AStream.WriteWord(WordToLE(idx+1));
 
     { Length of menu text }
     AStream.WriteByte(0);
@@ -3134,18 +3165,21 @@ end;
 procedure TsSpreadBIFF8Writer.WriteDefinedNames(AStream: TStream);
 var
   bookIdx: Integer;
+  book: TsWorkbook;
   sheet: TsWorksheet;
   i: Integer;
 begin
   if (FBiff8ExternBooks = nil) or (FBiff8ExternSheets = nil) then
     exit;
 
+  book := FWorkbook as TsWorkbook;
+
   // Defined names in "internal" book only
   bookIdx := FBiff8ExternBooks.IndexOfInternalbook;
 
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i);
     if (sheet.PageLayout.NumPrintRanges > 0) or
        sheet.PageLayout.HasRepeatedCols or sheet.PageLayout.HasRepeatedRows then
     begin
@@ -3170,7 +3204,7 @@ end;
   See bug 18886: excel5 files are truncated when imported
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF8Writer.WriteDimensions(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   firstRow, lastRow, firstCol, lastCol: Cardinal;
   rec: TBIFF8_DimensionsRecord;
@@ -3219,7 +3253,7 @@ begin
   { Current workbook -- assuming that it has index 0 in list FExternBook8 }
   if AUrl = '' then begin
     { Number of sheets in this workbook }
-    AStream.WriteWord(WordToLE(FWorkbook.GetWorksheetCount));
+    AStream.WriteWord(WordToLE((FWorkbook as TsWorkbook).GetWorksheetCount));
 
     { Relict from BIFF5 }
     AStream.WriteWord(WordToLE($0401));
@@ -3344,9 +3378,11 @@ end;
 procedure TsSpreadBiff8Writer.WriteFonts(AStream: TStream);
 var
   i: Integer;
+  book: TsWorkbook;
 begin
-  for i:=0 to Workbook.GetFontCount-1 do
-    WriteFONT(AStream, Workbook.GetFont(i));
+  book := FWorkbook as TsWorkbook;
+  for i:=0 to book.GetFontCount-1 do
+    WriteFONT(AStream, book.GetFont(i));
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -3407,7 +3443,7 @@ var
   len: Integer;
   id: Word;
 begin
-  with FWorksheet.PageLayout do
+  with (FWorksheet as TsWorksheet).PageLayout do
     if AIsHeader then
     begin
       if (Headers[HEADER_FOOTER_INDEX_ALL] = '') then
@@ -3440,7 +3476,7 @@ end;
   Writes an Excel 8 HYPERLINK record
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF8Writer.WriteHyperlink(AStream: TStream;
-  AHyperlink: PsHyperlink; AWorksheet: TsWorksheet);
+  AHyperlink: PsHyperlink; AWorksheet: TsBasicWorksheet);
 var
   temp: TStream;
   guid: TGUID;
@@ -3456,11 +3492,11 @@ var
   isInternal: Boolean;
   dirUpCounter: Integer;
 begin
-  cell := AWorksheet.FindCell(AHyperlink^.Row, AHyperlink^.Col);
+  cell := (AWorksheet as TsWorksheet).FindCell(AHyperlink^.Row, AHyperlink^.Col);
   if (cell = nil) or (AHyperlink^.Target='') then
     exit;
 
-  descr := AWorksheet.ReadAsText(cell);      // Hyperlink description
+  descr := (AWorksheet as TsWorksheet).ReadAsText(cell);   // Hyperlink description
   SplitHyperlink(AHyperlink^.Target, target, bookmark);
   u := ParseURI(AHyperlink^.Target);
   isInternal := (target = '') and (bookmark <> '');
@@ -3597,11 +3633,11 @@ end;
   Writes all hyperlinks
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF8Writer.WriteHyperlinks(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   hyperlink: PsHyperlink;
 begin
-  for hyperlink in AWorksheet.Hyperlinks do begin
+  for hyperlink in (AWorksheet as TsWorksheet).Hyperlinks do begin
     { Write HYPERLINK record }
     WriteHyperlink(AStream, hyperlink, AWorksheet);
     { Write HYPERLINK TOOLTIP record }
@@ -3787,18 +3823,19 @@ begin
 end;
 
 procedure TsSpreadBIFF8Writer.WriteMergedCells(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 const
   MAX_PER_RECORD = 1026;
 var
   n0, n: Integer;
   rng: PsCellRange;
   newRecord: Boolean;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  n0 := AWorksheet.MergedCells.Count;
+  n0 := sheet.MergedCells.Count;
   n := Min(n0, MAX_PER_RECORD);
   newRecord := true;
-  for rng in AWorksheet.MergedCells do
+  for rng in sheet.MergedCells do
   begin
     if newRecord then
     begin
@@ -4781,11 +4818,15 @@ end;
   sheets.
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFF8Writer.WriteWINDOW2(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   Options: Word;
-  actSheet: TsWorksheet;
+  book: TsWorkbook;
+  sheet, actSheet: TsWorksheet;
 begin
+  book := FWorkbook as TsWorkbook;
+  sheet := ASheet as TsWorksheet;
+
   { BIFF Record header }
   WriteBiffHeader(AStream, INT_EXCEL_ID_WINDOW2, 18);
 
@@ -4800,18 +4841,18 @@ begin
    { Bug 0026386 -> every sheet must be selected/active, otherwise Excel cannot print
      ---> wp: after changes for issue 0028452: this is not necessary any more. }
 
-  if (soShowGridLines in ASheet.Options) then
+  if (soShowGridLines in sheet.Options) then
     Options := Options or MASK_WINDOW2_OPTION_SHOW_GRID_LINES;
-  if (soShowHeaders in ASheet.Options) then
+  if (soShowHeaders in sheet.Options) then
     Options := Options or MASK_WINDOW2_OPTION_SHOW_SHEET_HEADERS;
-  if (soHasFrozenPanes in ASheet.Options) and ((ASheet.LeftPaneWidth > 0) or (ASheet.TopPaneHeight > 0)) then
+  if (soHasFrozenPanes in sheet.Options) and ((sheet.LeftPaneWidth > 0) or (sheet.TopPaneHeight > 0)) then
     Options := Options or MASK_WINDOW2_OPTION_PANES_ARE_FROZEN;
-  if FWorkbook.ActiveWorksheet <> nil then
-    actSheet := FWorkbook.ActiveWorksheet else
-    actSheet := Fworkbook.GetWorksheetByIndex(0);
-  if (ASheet = actSheet) then
+  if book.ActiveWorksheet <> nil then
+    actSheet := book.ActiveWorksheet else
+    actSheet := book.GetWorksheetByIndex(0);
+  if (sheet = actSheet) then
     Options := Options or MASK_WINDOW2_OPTION_SHEET_ACTIVE or MASK_WINDOW2_OPTION_SHEET_SELECTED;
-  if (ASheet.BiDiMode = bdRTL) then
+  if (sheet.BiDiMode = bdRTL) then
     Options := Options or MASK_WINDOW2_OPTION_COLUMNS_RIGHT_TO_LEFT;
   AStream.WriteWord(WordToLE(Options));
 
@@ -4870,7 +4911,7 @@ begin
   j := 0;
   if (AFormatRecord <> nil) and (uffNumberFormat in AFormatRecord^.UsedFormattingFields)
   then begin
-    nfParams := Workbook.GetNumberFormat(AFormatRecord^.NumberFormatIndex);
+    nfParams := (Workbook as TsWorkbook).GetNumberFormat(AFormatRecord^.NumberFormatIndex);
     if nfParams <> nil then
     begin
       nfs := nfParams.NumFormatStr;
diff --git a/components/fpspreadsheet/source/common/xlscommon.pas b/components/fpspreadsheet/source/common/xlscommon.pas
index cae912ce2..44ddbe569 100644
--- a/components/fpspreadsheet/source/common/xlscommon.pas
+++ b/components/fpspreadsheet/source/common/xlscommon.pas
@@ -11,7 +11,7 @@ interface
 
 uses
   Classes, SysUtils, DateUtils, lconvencoding, contnrs,
-  fpsTypes, fpSpreadsheet, fpsUtils, fpsNumFormat, fpsPalette,
+  fpsTypes, fpsUtils, fpsNumFormat, fpsPalette,
   fpsReaderWriter, fpsrpn;
 
 const
@@ -404,16 +404,16 @@ type
   end;
 
   TsBIFFLinkListItem = class
-    Worksheet: TsWorksheet;
+    Worksheet: TsBasicWorksheet;
     Sheetlist: TsBIFFExternSheetList;
     destructor Destroy; override;
   end;
 
   TsBIFFLinkLists = class(TFPObjectList)
   public
-    function GetSheetList(AWorksheet: TsWorksheet): TsBiffExternSheetList;
+    function GetSheetList(AWorksheet: TsBasicWorksheet): TsBiffExternSheetList;
     function GetGlobalLinks: TsBiffExternSheetList;
-    function GetLocalLinks(AWorksheet: TsWorksheet): TsBiffExternSheetList;
+    function GetLocalLinks(AWorksheet: TsBasicWorksheet): TsBiffExternSheetList;
   end;
 
 
@@ -447,11 +447,12 @@ type
     // Returns the numberformat for a given XF record
     procedure ExtractNumberFormat(AXFIndex: WORD;
       out ANumberFormat: TsNumberFormat; out ANumberFormatStr: String); virtual;
-    procedure ExtractPrintRanges(AWorksheet: TsWorksheet);
-    procedure ExtractPrintTitles(AWorksheet: TsWorksheet);
-    function FindDefinedName(AWorksheet: TsWorksheet; const AName: String): TsBiffDefinedName;
+    procedure ExtractPrintRanges(AWorksheet: TsBasicWorksheet);
+    procedure ExtractPrintTitles(AWorksheet: TsBasicWorksheet);
+    function FindDefinedName(AWorksheet: TsBasicWorksheet;
+      const AName: String): TsBiffDefinedName;
     procedure FixColors;
-    procedure FixDefinedNames(AWorksheet: TsWorksheet);
+    procedure FixDefinedNames(AWorksheet: TsBasicWorksheet);
     function FixFontIndex(AFontIndex: Integer): Integer;
     // Tries to find if a number cell is actually a date/datetime/time cell and retrieves the value
     function IsDateTime(Number: Double; ANumberFormat: TsNumberFormat;
@@ -474,9 +475,9 @@ type
     // Read the default row height
     procedure ReadDefRowHeight(AStream: TStream);
     // Read an EXTERNCOUNT record
-    procedure ReadEXTERNCOUNT(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure ReadEXTERNCOUNT(AStream: TStream; AWorksheet: TsBasicWorksheet);
     // Read an EXTERNSHEET record (defined names)
-    procedure ReadEXTERNSHEET(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure ReadEXTERNSHEET(AStream: TStream; AWorksheet: TsBasicWorksheet);
     // Read FORMAT record (cell formatting)
     procedure ReadFormat(AStream: TStream); virtual;
     // Read FORMULA record
@@ -491,7 +492,8 @@ type
     // Read floating point number
     procedure ReadNumber(AStream: TStream); override;
     // Read OBJECTPROTECT record
-    procedure ReadObjectProtect(AStream: TStream; AWorksheet: TsWorksheet = nil);
+    procedure ReadObjectProtect(AStream: TStream;
+      AWorksheet: TsBasicWorksheet = nil);
     // Read palette
     procedure ReadPalette(AStream: TStream);
     // Read page setup
@@ -499,11 +501,11 @@ type
     // Read PANE record
     procedure ReadPane(AStream: TStream);
     // Read PASSWORD record
-    procedure ReadPASSWORD(AStream: TStream; AWorksheet: TsWorksheet = nil);
+    procedure ReadPASSWORD(AStream: TStream; AWorksheet: TsBasicWorksheet = nil);
     procedure ReadPrintGridLines(AStream: TStream);
     procedure ReadPrintHeaders(AStream: TStream);
     // Reads whether the workbook or worksheet is protected
-    procedure ReadPROTECT(AStream: TStream; AWorksheet: TsWorksheet = nil);
+    procedure ReadPROTECT(AStream: TStream; AWorksheet: TsBasicWorksheet = nil);
     // Read an RK value cell
     procedure ReadRKValue(AStream: TStream);
     // Read the row, column, and XF index at the current stream position
@@ -553,7 +555,7 @@ type
     procedure ReadWorksheet(AStream: TStream); virtual;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
   end;
 
@@ -569,16 +571,16 @@ type
     FLinkLists: TsBiffLinkLists;
 
     procedure AddBuiltinNumFormats; override;
-    function CollectExternData(AWorksheet: TsWorksheet = nil): Integer;
+    function CollectExternData(AWorksheet: TsBasicWorksheet = nil): Integer;
     function FindXFIndex(AFormatIndex: Integer): Integer; virtual;
     function FixLineEnding(const AText: String): String;
     function FormulaSupported(ARPNFormula: TsRPNFormula; out AUnsupported: String): Boolean;
     function FunctionSupported(AExcelCode: Integer; const AFuncName: String): Boolean; virtual;
-    function GetLastRowIndex(AWorksheet: TsWorksheet): Integer;
-    function GetLastColIndex(AWorksheet: TsWorksheet): Word;
+    function GetLastRowIndex(AWorksheet: TsBasicWorksheet): Integer;
+    function GetLastColIndex(AWorksheet: TsBasicWorksheet): Word;
     function GetPrintOptions: Word; virtual;
     function PaletteIndex(AColor: TsColor): Word;
-    procedure PopulatePalette(AWorkbook: TsWorkbook); virtual;
+    procedure PopulatePalette(AWorkbook: TsBasicWorkbook); virtual;
 
     // Helper function for writing the BIFF header
     procedure WriteBIFFHeader(AStream: TStream; ARecID, ARecSize: Word);
@@ -595,7 +597,7 @@ type
     procedure WriteCodePage(AStream: TStream; ACodePage: String); virtual;
     // Writes out column info(s)
     procedure WriteColInfo(AStream: TStream; ACol: PCol);
-    procedure WriteColInfos(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteColInfos(AStream: TStream; ASheet: TsBasicWorksheet);
     // Writes out NOTE record(s)
     procedure WriteComment(AStream: TStream; ACell: PCell); override;
     // Writes out DATEMODE record depending on FDateMode
@@ -604,11 +606,11 @@ type
     procedure WriteDateTime(AStream: TStream; const ARow, ACol: Cardinal;
        const AValue: TDateTime; ACell: PCell); override;
     // Writes out a DEFCOLWIDTH record
-    procedure WriteDefaultColWidth(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteDefaultColWidth(AStream: TStream; AWorksheet: TsBasicWorksheet);
     // Writes out a DEFAULTROWHEIGHT record
-    procedure WriteDefaultRowHeight(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteDefaultRowHeight(AStream: TStream; AWorksheet: TsBasicWorksheet);
     // Writes out DEFINEDNAMES records
-    procedure WriteDefinedName(AStream: TStream; AWorksheet: TsWorksheet;
+    procedure WriteDefinedName(AStream: TStream; AWorksheet: TsBasicWorksheet;
        const AName: String; AIndexToREF, ASheetIndex: Word;
        AKind: TsBIFFExternKind); virtual;
     procedure WriteDefinedNames(AStream: TStream);
@@ -636,23 +638,23 @@ type
     procedure WriteNumber(AStream: TStream; const ARow, ACol: Cardinal;
       const AValue: Double; ACell: PCell); override;
     // Writes an OBJECTPROTECT record
-    procedure WriteObjectProtect(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteObjectProtect(AStream: TStream; ASheet: TsBasicWorksheet);
     procedure WritePageSetup(AStream: TStream);
     // Writes out a PALETTE record containing all colors defined in the workbook
     procedure WritePalette(AStream: TStream);
     // Writes out a PANE record
-    procedure WritePane(AStream: TStream; ASheet: TsWorksheet; IsBiff58: Boolean;
-      out ActivePane: Byte);
+    procedure WritePane(AStream: TStream; ASheet: TsBasicWorksheet;
+      IsBiff58: Boolean; out ActivePane: Byte);
     procedure WritePASSWORD(AStream: TStream; const ACryptoInfo: TsCryptoInfo);
     // Writes out whether grid lines are printed
     procedure WritePrintGridLines(AStream: TStream);
     procedure WritePrintHeaders(AStream: TStream);
     procedure WritePROTECT(AStream: TStream; AEnable: Boolean);
     // Writes out a ROW record
-    procedure WriteRow(AStream: TStream; ASheet: TsWorksheet;
+    procedure WriteRow(AStream: TStream; ASheet: TsBasicWorksheet;
       ARowIndex, AFirstColIndex, ALastColIndex: Cardinal; ARow: PRow); virtual;
     // Write all ROW records for a sheet
-    procedure WriteRows(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteRows(AStream: TStream; ASheet: TsBasicWorksheet);
 
     function WriteRPNCellAddress(AStream: TStream; ARow, ACol: Cardinal;
       AFlags: TsRelFlags): Word; virtual;
@@ -674,11 +676,12 @@ type
       AFormula: TsRPNFormula; UseRelAddr, IsSupported: Boolean; var RPNLength: Word);
     procedure WriteRPNTokenArraySize(AStream: TStream; ASize: Word); virtual;
 
-    procedure WriteSCLRecord(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteSCLRecord(AStream: TStream; ASheet: TsBasicWorksheet);
 
     // Writes out a SELECTION record
-    procedure WriteSELECTION(AStream: TStream; ASheet: TsWorksheet; APane: Byte);
-    procedure WriteSelections(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteSELECTION(AStream: TStream; ASheet: TsBasicWorksheet;
+      APane: Byte);
+    procedure WriteSelections(AStream: TStream; ASheet: TsBasicWorksheet);
     (*
     // Writes out a shared formula
     procedure WriteSharedFormula(AStream: TStream; ACell: PCell); virtual;
@@ -689,7 +692,7 @@ type
     procedure WriteSTRINGRecord(AStream: TStream; AString: String); virtual;
     procedure WriteVCenter(AStream: TStream);
     // Writes cell content received by workbook in OnNeedCellData event
-    procedure WriteVirtualCells(AStream: TStream; ASheet: TsWorksheet);
+    procedure WriteVirtualCells(AStream: TStream; ASheet: TsBasicWorksheet);
     // Writes out a WINDOW1 record
     procedure WriteWindow1(AStream: TStream); virtual;
     procedure WriteWindowProtect(AStream: TStream; AEnable: Boolean);
@@ -700,7 +703,7 @@ type
     procedure WriteXFRecords(AStream: TStream);
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
     procedure CheckLimitations; override;
   end;
@@ -715,7 +718,7 @@ implementation
 
 uses
   Math, Variants,
-  {%H-}fpspatches, fpsStrings, fpsClasses, xlsConst,
+  {%H-}fpspatches, fpsStrings, fpsClasses, fpSpreadsheet, xlsConst,
   fpsExprParser, fpsPageLayout;
 
 const
@@ -1025,7 +1028,7 @@ end;
 {                             TsBIFFLinkLists                                  }
 {------------------------------------------------------------------------------}
 function TsBIFFLinkLists.GetSheetList(
-  AWorksheet: TsWorksheet): TsBiffExternSheetList;
+  AWorksheet: TsBasicWorksheet): TsBiffExternSheetList;
 var
   i: Integer;
   item: TsBIFFLinkListItem;
@@ -1046,7 +1049,7 @@ begin
 end;
 
 function TsBIFFLinkLists.GetLocalLinks(
-  AWorksheet: TsWorksheet): TsBIFFExternSheetList;
+  AWorksheet: TsBasicWorksheet): TsBIFFExternSheetList;
 begin
   Result := GetSheetList(AWorksheet);
 end;
@@ -1125,7 +1128,7 @@ end;
 {                           TsSpreadBIFFReader                                 }
 {------------------------------------------------------------------------------}
 
-constructor TsSpreadBIFFReader.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFFReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -1189,7 +1192,7 @@ begin
   idx := FCellFormatList.FindIndexOfID(XFIndex);
   if idx > -1 then begin
     fmt := FCellFormatList.Items[idx];
-    result := FWorkbook.AddCellFormat(fmt^);   // Adds a copy of fmt to workbook
+    result := TsWorkbook(FWorkbook).AddCellFormat(fmt^);   // Adds a copy of fmt to workbook
   end else
     Result := 0;
 end;
@@ -1291,7 +1294,7 @@ begin
   end;
 end;
 
-procedure TsSpreadBiffReader.ExtractPrintRanges(AWorksheet: TsWorksheet);
+procedure TsSpreadBiffReader.ExtractPrintRanges(AWorksheet: TsBasicWorksheet);
 var
   defName: TsBiffDefinedName;
   rng: TsCellRange3DArray;
@@ -1303,12 +1306,15 @@ begin
   begin
     rng := defName.Ranges;
     for i := 0 to High(rng) do
-      AWorksheet.PageLayout.AddPrintRange(rng[i].Row1, rng[i].Col1, rng[i].Row2, rng[i].Col2);
+      TsWorksheet(AWorksheet).PageLayout.AddPrintRange(
+        rng[i].Row1, rng[i].Col1, rng[i].Row2, rng[i].Col2
+      );
   end;
 end;
 
-procedure TsSpreadBiffReader.ExtractPrintTitles(AWorksheet: TsWorksheet);
+procedure TsSpreadBiffReader.ExtractPrintTitles(AWorksheet: TsBasicWorksheet);
 var
+  sheet: TsWorksheet absolute AWorksheet;
   defName: TsBiffDefinedName;
   rng: TsCellRange3dArray;
   i: Integer;
@@ -1321,22 +1327,22 @@ begin
     for i := 0 to High(rng) do
     begin
       if (rng[i].Col2 <> Cardinal(-1)) then
-        AWorksheet.PageLayout.SetRepeatedCols(rng[i].Col1, rng[i].Col2)
+        sheet.PageLayout.SetRepeatedCols(rng[i].Col1, rng[i].Col2)
       else
       if (rng[i].Row2 <> Cardinal(-1)) then
-        AWorksheet.PageLayout.SetRepeatedRows(rng[i].Row1, rng[i].Row2);
+        sheet.PageLayout.SetRepeatedRows(rng[i].Row1, rng[i].Row2);
     end;
   end;
 end;
 
-function TsSpreadBIffReader.FindDefinedName(AWorksheet: TsWorksheet;
+function TsSpreadBIffReader.FindDefinedName(AWorksheet: TsBasicWorksheet;
   const AName: String): TsBiffDefinedName;
 var
   i: integer;
   wi: Integer;
   defName: TsBiffDefinedName;
 begin
-  wi := FWorkbook.GetWorksheetIndex(AWorksheet);
+  wi := TsWorkbook(FWorkbook).GetWorksheetIndex(AWorksheet);
   for i := 0 to FDefinedNames.Count-1 do
   begin
     defName := TsBiffDefinedName(FDefinedNames[i]);
@@ -1376,9 +1382,9 @@ begin
     if fnt <> nil then FixColor(fnt.Color);
   end;
 
-  for i:=0 to FWorkbook.GetFontCount - 1 do
+  for i:=0 to TsWorkbook(FWorkbook).GetFontCount - 1 do
   begin
-    fnt := FWorkbook.GetFont(i);
+    fnt := TsWorkbook(FWorkbook).GetFont(i);
     FixColor(fnt.Color);
   end;
 
@@ -1396,13 +1402,13 @@ begin
   end;
 end;
 
-procedure TsSpreadBIFFReader.FixDefinedNames(AWorksheet: TsWorksheet);
+procedure TsSpreadBIFFReader.FixDefinedNames(AWorksheet: TsBasicWorksheet);
 var
   i: Integer;
   defname: TsBiffDefinedName;
   sheetIndex: Integer;
 begin
-  sheetIndex := FWorkbook.GetWorksheetIndex(AWorksheet);
+  sheetIndex := TsWorkbook(FWorkbook).GetWorksheetIndex(AWorksheet);
   for i:=0 to FDefinedNames.Count-1 do begin
     defname := TsBiffDefinedName(FDefinedNames.Items[i]);
     defname.UpdateSheetIndex(AWorksheet.Name, sheetIndex);
@@ -1418,6 +1424,7 @@ end;
 function TsSpreadBIFFReader.FixFontIndex(AFontIndex: Integer): Integer;
 var
   fnt: TsFont;
+  book: TsWorkbook;
 begin
   // There are some files which do not contain any font records.
   // Here we use the predefined DefaultFont of the workbook.
@@ -1432,9 +1439,10 @@ begin
     Result := -1
   else
   begin
-    Result := FWorkbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+    book := FWorkbook as TsWorkbook;
+    Result := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
     if Result = -1 then
-      Result := FWorkbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+      Result := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
   end;
 end;
 
@@ -1491,15 +1499,15 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := TsWorksheet(FWorksheet).AddCell(ARow, ACol);
 
-  FWorksheet.WriteBlank(cell);
+  TsWorksheet(FWorksheet).WriteBlank(cell);
 
   { Add attributes to cell}
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (FWorkbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -1512,12 +1520,14 @@ var
   r, c: Cardinal;
   XF: Word;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
   rec.Row := 0;  // to silence the compiler
 
   { Read entire record into a buffer }
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF38BoolErrRecord) - 2*SizeOf(Word));
 
+  sheet := FWorksheet as TsWorksheet;
   r := WordLEToN(rec.Row);
   c := WordLEToN(rec.Col);
   XF := WordLEToN(rec.XFIndex);
@@ -1526,19 +1536,19 @@ begin
     InitCell(FWorksheet, r, c, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(r, c);
+    cell := sheet.AddCell(r, c);
 
   { Retrieve boolean or error value depending on the "ValueType" }
   case rec.ValueType of
-    0: FWorksheet.WriteBoolValue(cell, boolean(rec.BoolErrValue));
-    1: FWorksheet.WriteErrorValue(cell, ConvertFromExcelError(rec.BoolErrValue));
+    0: sheet.WriteBoolValue(cell, boolean(rec.BoolErrValue));
+    1: sheet.WriteErrorValue(cell, ConvertFromExcelError(rec.BoolErrValue));
   end;
 
   { Add attributes to cell}
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, r, c, cell);
+    TsWorkbook(Workbook).OnReadCellData(Workbook, r, c, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -1606,7 +1616,12 @@ var
   lCol: TCol;
   idx: Integer;
   fmt: PsCellFormat;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
+  book := FWorkbook as TsWorkbook;
+  sheet := FWorksheet as TsWorksheet;
+
   { Read column start and end index of column range }
   c1 := WordLEToN(AStream.ReadWord);
   c2 := WordLEToN(AStream.ReadWord);
@@ -1616,8 +1631,8 @@ begin
   w := WordLEToN(AStream.ReadWord);
 
   { Calculate width in workbook units }
-  lCol.Width := FWorkbook.ConvertUnits(w / 256, suChars, FWorkbook.Units);
-  if SameValue(lCol.Width, FWorksheet.ReadDefaultColWidth(FWorkbook.Units), EPS) then
+  lCol.Width := book.ConvertUnits(w / 256, suChars, FWorkbook.Units);
+  if SameValue(lCol.Width, sheet.ReadDefaultColWidth(FWorkbook.Units), EPS) then
     lCol.ColWidthType := cwtDefault else
     lCol.ColWidthType := cwtCustom;
 
@@ -1626,14 +1641,14 @@ begin
   idx := FCellFormatList.FindIndexOfID(xf);
   if idx > -1 then begin
     fmt := FCellFormatList.Items[idx];
-    lCol.FormatIndex := FWorkbook.AddCellFormat(fmt^);
+    lCol.FormatIndex := book.AddCellFormat(fmt^);
   end else
     lCol.FormatIndex := 0;
 
   { Assign width and format to columns, but only if different from defaults }
   if (lCol.FormatIndex > 0) or (lCol.ColWidthType = cwtCustom) then
     for c := c1 to c2 do
-      FWorksheet.WriteColInfo(c, lCol);
+      sheet.WriteColInfo(c, lCol);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -1647,7 +1662,10 @@ var
   n: Word;
   s: ansiString;
   List: TStringList;
+  sheet: TsWorksheet;
 begin
+  sheet := TsWorksheet(FWorksheet);
+
   rec.Row := 0; // to silence the compiler...
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF25NoteRecord) - 2*SizeOf(Word));
   r := WordLEToN(rec.Row);
@@ -1668,7 +1686,7 @@ begin
         List.Text := s;  // Fix line endings which are #10 in file
         s := Copy(List.Text, 1, Length(List.Text) - Length(LineEnding));
         s := ConvertEncoding(s, FCodePage, encodingUTF8);
-        FWorksheet.WriteComment(r, c, s);
+        sheet.WriteComment(r, c, s);
       finally
         List.Free;
       end;
@@ -1680,7 +1698,7 @@ begin
       SetLength(s, n);
       AStream.ReadBuffer(s[1], n);
       FIncompleteNote := s;
-      FIncompleteCell := FWorksheet.GetCell(r, c);  // no AddCell here!
+      FIncompleteCell := sheet.GetCell(r, c);  // no AddCell here!
     end;
   end else
   // One of the continuation records
@@ -1695,7 +1713,7 @@ begin
       try
         List.Text := FIncompleteNote;    // Fix line endings which are #10 in file
         s := Copy(List.Text, 1, Length(List.Text) - Length(LineEnding));
-        FWorksheet.WriteComment(FIncompleteCell, s);
+        sheet.WriteComment(FIncompleteCell, s);
       finally
         List.Free;
       end;
@@ -1739,7 +1757,7 @@ var
 begin
   // The file contains the column width in characters
   w := WordLEToN(AStream.ReadWord);
-  FWorksheet.WriteDefaultColWidth(w, suChars);
+  TsWorksheet(FWorksheet).WriteDefaultColWidth(w, suChars);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -1755,11 +1773,11 @@ begin
 
   // Height, in Twips (1/20 pt).
   hw := WordLEToN(AStream.ReadWord);
-  FWorksheet.WriteDefaultRowHeight(TwipsToPts(hw), suPoints);
+  TsWorksheet(FWorksheet).WriteDefaultRowHeight(TwipsToPts(hw), suPoints);
 end;
 
 procedure TsSpreadBIFFReader.ReadEXTERNCOUNT(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   item: TsBIFFLinkListItem;
 begin
@@ -1784,7 +1802,7 @@ end;
   a reference to one of the own sheets (first character is #03).
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFReader.ReadEXTERNSHEET(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   len, b: Byte;
   ansistr: AnsiString;
@@ -1839,8 +1857,11 @@ var
   err: TsErrorValue;
   ok: Boolean;
   cell: PCell;
+  sheet: TsWorksheet;
   msg: String;
 begin
+  sheet := TsWorksheet(FWorksheet);
+
   { Index to XF Record }
   ReadRowColXF(AStream, ARow, ACol, XF);
 
@@ -1860,7 +1881,7 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.GetCell(ARow, ACol);    // "Real" cell
+    cell := sheet.GetCell(ARow, ACol);    // "Real" cell
     // Don't call "AddCell" because, if the cell belongs to a shared formula, it
     // already has been created before, and then would exist in the tree twice.
 
@@ -1871,14 +1892,14 @@ begin
          FIncompleteCell := cell;
 
       1: // Boolean value
-         FWorksheet.WriteBoolValue(cell, Data[2] = 1);
+         sheet.WriteBoolValue(cell, Data[2] = 1);
 
       2: begin  // Error value
            err := ConvertFromExcelError(Data[2]);
-           FWorksheet.WriteErrorValue(cell, err);
+           sheet.WriteErrorValue(cell, err);
          end;
 
-      3: FWorksheet.WriteBlank(cell);
+      3: sheet.WriteBlank(cell);
     end
   else
   begin
@@ -1888,9 +1909,9 @@ begin
     {Find out what cell type, set content type and value}
     ExtractNumberFormat(XF, nf, nfs);
     if IsDateTime(ResultFormula, nf, nfs, dt) then
-      FWorksheet.WriteDateTime(cell, dt) //, nf, nfs)
+      sheet.WriteDateTime(cell, dt) //, nf, nfs)
     else
-      FWorksheet.WriteNumber(cell, ResultFormula); //, nf, nfs);
+      sheet.WriteNumber(cell, ResultFormula); //, nf, nfs);
   end;
 
   { Formula token array }
@@ -1905,7 +1926,7 @@ begin
       if (boAbortReadOnFormulaError in Workbook.Options) then
         raise Exception.Create(msg)
       else begin
-        FWorksheet.WriteErrorValue(cell, errFormulaNotSupported);
+        sheet.WriteErrorValue(cell, errFormulaNotSupported);
         FWorkbook.AddErrorMsg(msg);
       end;
     end;
@@ -1915,7 +1936,7 @@ begin
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode and (cell <> FIncompleteCell) then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (FWorkbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -1927,7 +1948,7 @@ var
 begin
   w := WordLEToN(AStream.ReadWord);
   if w = 1 then
-    with FWorksheet.PageLayout do
+    with TsWorksheet(FWorksheet).PageLayout do
       Options := Options + [poHorCentered];
 end;
 
@@ -1947,7 +1968,7 @@ begin
   Len := AStream.ReadByte;
   SetLength(s, len*SizeOf(ansichar));
   AStream.ReadBuffer(s[1], len*SizeOf(ansichar));
-  with FWorksheet.PageLayout do
+  with TsWorksheet(FWorksheet).PageLayout do
   begin
     if AIsHeader then
     begin
@@ -1972,12 +1993,13 @@ var
   dbl: Double = 0.0;
 begin
   AStream.ReadBuffer(dbl, SizeOf(dbl));
-  case AMargin of
-    0: FWorksheet.PageLayout.LeftMargin := InToMM(dbl);
-    1: FWorksheet.PageLayout.RightMargin := InToMM(dbl);
-    2: FWorksheet.PageLayout.TopMargin := InToMM(dbl);
-    3: FWorksheet.PageLayout.BottomMargin := InToMM(dbl);
-  end;
+  with TsWorksheet(FWorksheet).PageLayout do
+    case AMargin of
+      0: LeftMargin := InToMM(dbl);
+      1: RightMargin := InToMM(dbl);
+      2: TopMargin := InToMM(dbl);
+      3: BottomMargin := InToMM(dbl);
+    end;
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2002,11 +2024,11 @@ begin
     if FIsVirtualMode then
       cell^.Col := fc
     else
-      cell := FWorksheet.AddCell(ARow, fc);
-    FWorksheet.WriteBlank(cell);
+      cell := TsWorksheet(FWorksheet).AddCell(ARow, fc);
+    TsWorksheet(FWorksheet).WriteBlank(cell);
     ApplyCellFormatting(cell, XF);
     if FIsVirtualMode then
-      Workbook.OnReadCellData(Workbook, ARow, fc, cell);
+      (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, fc, cell);
     inc(fc);
     dec(pending, SizeOf(XF));
   end;
@@ -2033,7 +2055,10 @@ var
   nf: TsNumberFormat;
   nfs: String;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
+  sheet := TsWorksheet(FWorksheet);
+
   ARow := WordLEtoN(AStream.ReadWord);
   fc := WordLEtoN(AStream.ReadWord);
   pending := RecordSize - SizeOf(fc) - SizeOf(ARow);
@@ -2046,20 +2071,20 @@ begin
     if FIsVirtualMode then
       cell^.Col := fc
     else
-      cell := FWorksheet.AddCell(ARow, fc);
+      cell := sheet.AddCell(ARow, fc);
     RK := DWordLEtoN(AStream.ReadDWord);
     lNumber := DecodeRKValue(RK);
     {Find out what cell type, set contenttype and value}
     ExtractNumberFormat(XF, nf, nfs);
     if IsDateTime(lNumber, nf, nfs, lDateTime) then
-      FWorksheet.WriteDateTime(cell, lDateTime, nf, nfs)
+      sheet.WriteDateTime(cell, lDateTime, nf, nfs)
     else if nf=nfText then
-      FWorksheet.WriteText(cell, GeneralFormatFloat(lNumber, FWorkbook.FormatSettings))
+      sheet.WriteText(cell, GeneralFormatFloat(lNumber, Workbook.FormatSettings))
     else
-      FWorksheet.WriteNumber(cell, lNumber, nf, nfs);
+      sheet.WriteNumber(cell, lNumber, nf, nfs);
     ApplyCellFormatting(cell, XF);
     if FIsVirtualMode then
-      Workbook.OnReadCellData(Workbook, ARow, fc, cell);
+      (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, fc, cell);
     inc(fc);
     dec(pending, SizeOf(XF) + SizeOf(RK));
   end;
@@ -2086,7 +2111,10 @@ var
   nf: TsNumberFormat;
   nfs: String;
   cell: PCell;
+  sheet: TsWorksheet;
 begin
+  sheet := TsWorksheet(FWorksheet);
+
   { Read entire record, starting at Row }
   rec.Row := 0;   // to silence the compiler...
   AStream.ReadBuffer(rec.Row, SizeOf(TBIFF58NumberRecord) - 2*SizeOf(Word));
@@ -2103,20 +2131,20 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);  // "real" cell
+    cell := sheet.AddCell(ARow, ACol);  // "real" cell
 
   if IsDateTime(value, nf, nfs, dt) then
-    FWorksheet.WriteDateTime(cell, dt, nf, nfs)
+    sheet.WriteDateTime(cell, dt, nf, nfs)
   else if nf = nfText then
-    FWorksheet.WriteText(cell, GeneralFormatFloat(value, FWorkbook.FormatSettings))
+    sheet.WriteText(cell, GeneralFormatFloat(value, FWorkbook.FormatSettings))
   else
-    FWorksheet.WriteNumber(cell, value, nf, nfs);
+    sheet.WriteNumber(cell, value, nf, nfs);
 
   { Add attributes to cell }
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2124,17 +2152,20 @@ end;
   etc) of the current sheet are protected.
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFReader.ReadObjectProtect(AStream: TStream;
-  AWorksheet: TsWorksheet = nil);
+  AWorksheet: TsBasicWorksheet = nil);
 var
   w: Word;
   sp: TsWorksheetProtections;
+  sheet: TsWorksheet;
 begin
   if AWorksheet = nil then
-    AWorksheet := FWorksheet;
+    sheet := TsWorksheet(FWorksheet)
+  else
+    sheet := TsWorksheet(AWorkSheet);
   w := WordLEToN(AStream.ReadWord);
-  sp := AWorksheet.Protection;
+  sp := sheet.Protection;
   if w = 0 then Exclude(sp, spObjects) else Include(sp, spObjects);
-  AWorksheet.Protection := sp;
+  sheet.Protection := sp;
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2166,37 +2197,40 @@ var
   w: Word;
   dbl: Double = 0.0;
   optns: TsPrintOptions;
+  sheet: TsWorksheet;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   // Store current pagelayout options, they already can contain the poFitPages
   // which gets altered when reading FitWidthToPages and FitHeightToPages
-  optns := FWorksheet.PageLayout.Options;
+  optns := sheet.PageLayout.Options;
 
   // Paper size
   w := WordLEToN(AStream.ReadWord);
   if (w <= High(PAPER_SIZES)) then
   begin
-    FWorksheet.PageLayout.PageWidth := PAPER_SIZES[w, 0];
-    FWorksheet.PageLayout.PageHeight := PAPER_SIZES[w, 1];
+    sheet.PageLayout.PageWidth := PAPER_SIZES[w, 0];
+    sheet.PageLayout.PageHeight := PAPER_SIZES[w, 1];
   end;
 
   // Scaling factor in percent
-  FWorksheet.PageLayout.ScalingFactor := WordLEToN(AStream.ReadWord);
+  sheet.PageLayout.ScalingFactor := WordLEToN(AStream.ReadWord);
 
   // Start page number
-  FWorksheet.PageLayout.StartPageNumber := WordLEToN(AStream.ReadWord);
+  sheet.PageLayout.StartPageNumber := WordLEToN(AStream.ReadWord);
 
   // Fit worksheet width to this number of pages (0 = use as many as neede)
-  FWorksheet.PageLayout.FitWidthToPages := WordLEToN(AStream.ReadWord);
+  sheet.PageLayout.FitWidthToPages := WordLEToN(AStream.ReadWord);
 
   // Fit worksheet height to this number of pages (0 = use as many as needed)
-  FWorksheet.PageLayout.FitHeightToPages := WordLEToN(AStream.ReadWord);
+  sheet.PageLayout.FitHeightToPages := WordLEToN(AStream.ReadWord);
 
   // Information whether scaling factor or fittopages are used is stored in the
   // SHEETPR record.
 
   // Option flags
   w := WordLEToN(AStream.ReadWord);
-  with FWorksheet.PageLayout do
+  with sheet.PageLayout do
   begin
     Options := optns;
     if w and $0001 <> 0 then
@@ -2226,14 +2260,14 @@ begin
 
   // Header margin
   AStream.ReadBuffer(dbl, SizeOf(dbl));
-  FWorksheet.PageLayout.HeaderMargin := InToMM(dbl);
+  sheet.PageLayout.HeaderMargin := InToMM(dbl);
 
   // Footer margin
   AStream.ReadBuffer(dbl, SizeOf(dbl));
-  FWorksheet.PageLayout.FooterMargin := InToMM(dbl);
+  sheet.PageLayout.FooterMargin := InToMM(dbl);
 
   // Number of copies
-  FWorksheet.PageLayout.Copies := WordLEToN(AStream.ReadWord);
+  sheet.PageLayout.Copies := WordLEToN(AStream.ReadWord);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2241,19 +2275,23 @@ end;
   Valid for all BIFF versions
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFReader.ReadPane(AStream: TStream);
+var
+  sheet: TsWorksheet;
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   { Position of horizontal split:
     - Unfrozen pane: Width of the left pane(s) (in twips = 1/20 of a point)
     - Frozen pane: Number of visible columns in left pane(s) }
-  FWorksheet.LeftPaneWidth := WordLEToN(AStream.ReadWord);
+  sheet.LeftPaneWidth := WordLEToN(AStream.ReadWord);
 
   { Position of vertical split:
     - Unfrozen pane: Height of the top pane(s) (in twips = 1/20 of a point)
     - Frozen pane: Number of visible rows in top pane(s) }
-  FWorksheet.TopPaneHeight := WordLEToN(AStream.ReadWord);
+  sheet.TopPaneHeight := WordLEToN(AStream.ReadWord);
 
-  if (FWorksheet.LeftPaneWidth = 0) and (FWorksheet.TopPaneHeight = 0) then
-    FWorksheet.Options := FWorksheet.Options - [soHasFrozenPanes];
+  if (sheet.LeftPaneWidth = 0) and (sheet.TopPaneHeight = 0) then
+    sheet.Options := sheet.Options - [soHasFrozenPanes];
 
   // Index to first visible row in bottom pane(s) -- not used
   AStream.ReadWord;
@@ -2271,7 +2309,7 @@ end;
   Reads the PASSWORD record containing the encrypted password
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFReader.ReadPASSWORD(AStream: TStream;
-  AWorksheet: TsWorksheet = nil);
+  AWorksheet: TsBasicWorksheet = nil);
 var
   hash: Word;
   cinfo: TsCryptoInfo;
@@ -2285,14 +2323,14 @@ begin
     InitCryptoInfo(cinfo);
     cinfo.PasswordHash := Format('%.4x', [hash]);
     cinfo.Algorithm := caExcel;
-    FWorkbook.CryptoInfo := cinfo;
+    TsWorkbook(FWorkbook).CryptoInfo := cinfo;
   end else
   begin
     // Password for worksheet protection
     InitCryptoInfo(cinfo);
     cinfo.PasswordHash := Format('%.4x', [hash]);
     cinfo.Algorithm := caExcel;
-    AWorksheet.CryptoInfo := cinfo;
+    TsWorksheet(AWorksheet).CryptoInfo := cinfo;
   end;
 end;
 
@@ -2305,7 +2343,7 @@ var
 begin
   w := WordLEToN(AStream.ReadWord);
   if w = 1 then
-    with FWorksheet.PageLayout do
+    with TsWorksheet(FWorksheet).PageLayout do
       Options := Options + [poPrintGridLines];
 end;
 
@@ -2318,7 +2356,7 @@ var
 begin
   w := WordLEToN(AStream.ReadWord);
   if w = 1 then
-    with FWorksheet.PageLayout do
+    with TsWorksheet(FWorksheet).PageLayout do
       Options := Options + [poPrintHeaders];
 end;
 
@@ -2326,27 +2364,31 @@ end;
   Determines whether the workbook or worksheet is protected
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFReader.ReadPROTECT(AStream: TStream;
-  AWorksheet: TsWorksheet = nil);
+  AWorksheet: TsBasicWorksheet = nil);
 var
   p: Word;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
   p := WordLEToN(AStream.ReadWord);
 
   if AWorksheet = nil then
   begin
     // Workbook protection
+    book := FWorkbook as TsWorkbook;
     if p = 1 then
-      FWorkbook.Protection := FWorkbook.Protection + [bpLockStructure]
+      book.Protection := book.Protection + [bpLockStructure]
     else
-      FWorkbook.Protection := FWorkbook.Protection - [bpLockStructure];
+      book.Protection := book.Protection - [bpLockStructure];
   end else
   begin
     // Worksheet protection
+    sheet := AWorksheet as TsWorksheet;
     if p = 1 then begin
-      AWorksheet.Protection := AWorksheet.Protection + [spCells];
-      AWorksheet.Protect(true);
+      sheet.Protection := sheet.Protection + [spCells];
+      sheet.Protect(true);
     end else
-      AWorksheet.Protect(false);
+      sheet.Protect(false);
   end;
 end;
 
@@ -2377,9 +2419,12 @@ var
   lDateTime: TDateTime;
   Number: Double;
   cell: PCell;
+  sheet: TsWorksheet;
   nf: TsNumberFormat;    // Number format
   nfs: String;           // Number format string
 begin
+  sheet := FWorksheet as TsWorksheet;
+
   {Retrieve XF record, row and column}
   ReadRowColXF(AStream, ARow, ACol, XF);
 
@@ -2394,22 +2439,22 @@ begin
     InitCell(FWorksheet, ARow, ACol, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.AddCell(ARow, ACol);
+    cell := sheet.AddCell(ARow, ACol);
 
   {Find out what cell type, set contenttype and value}
   ExtractNumberFormat(XF, nf, nfs);
   if IsDateTime(Number, nf, nfs, lDateTime) then
-    FWorksheet.WriteDateTime(cell, lDateTime, nf, nfs)
+    sheet.WriteDateTime(cell, lDateTime, nf, nfs)
   else if nf=nfText then
-    FWorksheet.WriteText(cell, GeneralFormatFloat(Number, FWorkbook.FormatSettings))
+    sheet.WriteText(cell, GeneralFormatFloat(Number, FWorkbook.FormatSettings))
   else
-    FWorksheet.WriteNumber(cell, Number, nf, nfs);
+    sheet.WriteNumber(cell, Number, nf, nfs);
 
   {Add attributes}
   ApplyCellFormatting(cell, XF);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, ARow, ACol, cell);
+    (Workbook as TsWorkbook).OnReadCellData(Workbook, ARow, ACol, cell);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2445,8 +2490,8 @@ begin
 
   { Row height }
   h := WordLEToN(rowrec.Height) and $7FFF;  // mask off "custom" bit
-  hpts := FWorkbook.ConvertUnits(TwipsToPts(h), suPoints, FWorkbook.Units);
-  hdef := FWorksheet.ReadDefaultRowHeight(FWorkbook.Units);
+  hpts := TsWorkbook(FWorkbook).ConvertUnits(TwipsToPts(h), suPoints, FWorkbook.Units);
+  hdef := TsWorksheet(FWorksheet).ReadDefaultRowHeight(FWorkbook.Units);
   isNonDefaultHeight := not SameValue(hpts, hdef, ROWHEIGHT_EPS);
   isAutoSizeHeight := flags and $00000040 = 0;
   // If this bit is set then font size and row height do NOT match, i.e. NO autosize
@@ -2470,7 +2515,7 @@ begin
   // We only create a row record for fpspreadsheet if the row has a
   // non-standard height (i.e. different from default row height) or format.
   if isNonDefaultHeight or hasFormat then
-    FWorksheet.WriteRowInfo(rowrec.RowIndex, lRow);
+    TsWorksheet(FWorksheet).WriteRowInfo(rowrec.RowIndex, lRow);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -2831,7 +2876,7 @@ begin
   n := ReadRPNTokenArraySize(AStream);
   Result := ReadRPNTokenArray(AStream, n, rpnFormula, ACell, ASharedFormulaBase);
   if Result then begin
-    strFormula := FWorksheet.ConvertRPNFormulaToStringFormula(rpnFormula);
+    strFormula := tsWorksheet(FWorksheet).ConvertRPNFormulaToStringFormula(rpnFormula);
     if strFormula <> '' then
       ACell^.FormulaValue := strFormula;
   end;
@@ -3066,7 +3111,7 @@ var
 begin
   num := WordLEToN(AStream.ReadWord);
   denom := WOrdLEToN(AStream.ReadWord);
-  FWorksheet.ZoomFactor := num/denom;
+  TsWorksheet(FWorksheet).ZoomFactor := num/denom;
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -3109,8 +3154,8 @@ begin
   // Apply selections to worksheet, but only in the pane with the cursor
   if paneIdx = FActivePane then
   begin
-    if Length(sel) > 0 then FWorksheet.SetSelection(sel);
-    FWorksheet.SelectCell(actRow, actCol);
+    if Length(sel) > 0 then TsWorksheet(FWorksheet).SetSelection(sel);
+    TsWorksheet(FWorksheet).SelectCell(actRow, actCol);
   end;
 end;
 
@@ -3135,7 +3180,7 @@ begin
     InitCell(FWorksheet, r1, c1, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := FWorksheet.GetCell(r1, c1);        // "Real" cell
+    cell := TsWorksheet(FWorksheet).GetCell(r1, c1);        // "Real" cell
     // Don't use "AddCell" here because this cell already exists in files written
     // by Excel, and this would destroy its formatting.
 
@@ -3151,7 +3196,7 @@ begin
   // Copy shared formula to individual cells in the specified range
   for r := r1 to r2 do
     for c := c1 to c2 do
-      FWorksheet.CopyFormula(cell, r, c);
+      TsWorksheet(FWorksheet).CopyFormula(cell, r, c);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -3162,7 +3207,7 @@ var
   flags: Word;
 begin
   flags := WordLEToN(AStream.ReadWord);
-  with FWorksheet.PageLayout do
+  with TsWorksheet(FWorksheet).PageLayout do
     if flags and $0100 <> 0 then
       Options := Options + [poFitPages]
     else
@@ -3205,7 +3250,7 @@ var
 begin
   w := WordLEToN(AStream.ReadWord);
   if w = 1 then
-    with FWorksheet.PageLayout do
+    with TsWorksheet(FWorksheet).PageLayout do
       Options := Options + [poVertCentered];
 end;
 
@@ -3238,10 +3283,10 @@ begin
     FWorksheet.Options := FWorksheet.Options - [soHasFrozenPanes];
 
   if (flags and MASK_WINDOW2_OPTION_SHEET_ACTIVE <> 0) then
-    FWorkbook.SelectWorksheet(FWorksheet);
+    TsWorkbook(FWorkbook).SelectWorksheet(FWorksheet as TsWorksheet);
 
   if (flags AND MASK_WINDOW2_OPTION_COLUMNS_RIGHT_TO_LEFT <> 0) then
-    FWorksheet.BiDiMode := bdRTL;
+    TsWorksheet(FWorksheet).BiDiMode := bdRTL;
 end;
 
 { Reads the workbook globals. }
@@ -3254,12 +3299,15 @@ end;
 procedure TsSpreadBIFFReader.ReadWindowProtect(AStream: TStream);
 var
   p: Word;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   p := WordLEToN(AStream.ReadWord);
   if p = 0 then   // Workbook not protected
-    FWorkbook.Protection := FWorkbook.Protection - [bpLockWindows]
+    book.Protection := book.Protection - [bpLockWindows]
   else   // Workbook protection
-    FWorkbook.Protection := FWorkbook.Protection + [bpLockWindows];
+    book.Protection := book.Protection + [bpLockWindows];
 end;
 
 procedure TsSpreadBIFFReader.ReadWorksheet(AStream: TStream);
@@ -3297,7 +3345,7 @@ begin
 
   { Read workbook globals }
   ReadWorkbookGlobals(AStream);
-  numSheets := FWorkbook.GetWorksheetCount;
+  numSheets := TsWorkbook(FWorkbook).GetWorksheetCount;
 
   { Check for the end of the file }
   if AStream.Position >= AStream.Size then
@@ -3322,7 +3370,7 @@ begin
 
   { Extract print ranges, repeated rows/cols }
   for i := 0 to numSheets - 1 do begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := TsWorkbook(FWorkbook).GetWorksheetByIndex(i);
     FixDefinedNames(sheet);
     ExtractPrintRanges(sheet);
     ExtractPrintTitles(sheet);
@@ -3340,7 +3388,7 @@ end;
 
   https://support.microsoft.com/de-de/help/507098
 -------------------------------------------------------------------------------}
-constructor TsSpreadBIFFWriter.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadBIFFWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -3399,7 +3447,7 @@ end;
   The found data are written to the a TBIFFLinkListItem which is added to
   FLinkLists. The function returns the index of the new TBIFFLinkListItem.
 -------------------------------------------------------------------------------}
-function TsSpreadBIFFWriter.CollectExternData(AWorksheet: TsWorksheet = nil): Integer;
+function TsSpreadBIFFWriter.CollectExternData(AWorksheet: TsBasicWorksheet = nil): Integer;
 
   procedure DoCollectForSheet(ASheet: TsWorksheet; ASheetList: TsBIFFExternSheetList);
   var
@@ -3462,15 +3510,15 @@ begin
   begin
     { This part is active when called from WriteLocalLinkList }
     linklist.Worksheet := AWorksheet;
-    DoCollectForSheet(AWorksheet, linklist.SheetList)
+    DoCollectForSheet(AWorksheet as TsWorksheet, linklist.SheetList)
   end else
   begin
     { This part is active when called from WriteGlobalLinkList }
     { Find sheets used in print ranges, repeated cols or repeated rows }
     linkList.Worksheet := nil;  // signals global linklist
-    for i:=0 to FWorkbook.GetWorksheetCount-1 do
+    for i:=0 to TsWorkbook(FWorkbook).GetWorksheetCount-1 do
     begin
-      sheet := FWorkbook.GetWorksheetbyIndex(i);
+      sheet := TsWorkbook(FWorkbook).GetWorksheetbyIndex(i);
       with sheet.PageLayout do
         writeIt := (NumPrintRanges > 0) or HasRepeatedCols or HasRepeatedRows;
       if writeIt then
@@ -3550,14 +3598,14 @@ begin
   Result := AExcelCode <> INT_EXCEL_SHEET_FUNC_NOT_BIFF;
 end;
 
-function TsSpreadBIFFWriter.GetLastRowIndex(AWorksheet: TsWorksheet): Integer;
+function TsSpreadBIFFWriter.GetLastRowIndex(AWorksheet: TsBasicWorksheet): Integer;
 begin
-  Result := AWorksheet.GetLastRowIndex;
+  Result := (AWorksheet as TsWorksheet).GetLastRowIndex;
 end;
 
-function TsSpreadBIFFWriter.GetLastColIndex(AWorksheet: TsWorksheet): Word;
+function TsSpreadBIFFWriter.GetLastColIndex(AWorksheet: TsBasicWorksheet): Word;
 begin
-  Result := AWorksheet.GetLastColIndex;
+  Result := (AWorksheet as TsWorksheet).GetLastColIndex;
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -3566,6 +3614,8 @@ end;
   Is overridden by BIFF8 which uses more bits. Not used by BIFF2.
 -------------------------------------------------------------------------------}
 function TsSpreadBIFFWriter.GetPrintOptions: Word;
+var
+  sheet: TsWorksheet;
 begin
   { Options:
      Bit 0: 0 = Print pages in columns; 1 = Print pages in rows
@@ -3584,19 +3634,20 @@ begin
      Bit 11-10:  00 = Print errors as displayed; 1 = Do not print errors
                  2 = Print errors as “--”; 3 = Print errors as “#N/A” }
   Result := 0;
-  if poPrintPagesByRows in FWorksheet.PageLayout.Options then
+  sheet := FWorksheet as TsWorksheet;
+  if poPrintPagesByRows in sheet.PageLayout.Options then
     Result := Result or $0001;
-  if FWorksheet.PageLayout.Orientation = spoPortrait then
+  if sheet.PageLayout.Orientation = spoPortrait then
     Result := Result or $0002;
-  if poMonochrome in FWorksheet.PageLayout.Options then
+  if poMonochrome in sheet.PageLayout.Options then
     Result := Result or $0008;
-  if poDraftQuality in FWorksheet.PageLayout.Options then
+  if poDraftQuality in sheet.PageLayout.Options then
     Result := Result or $0010;
-  if poPrintCellComments in FWorksheet.PageLayout.Options then
+  if poPrintCellComments in sheet.PageLayout.Options then
     Result := Result or $0020;
-  if poDefaultOrientation in FWorksheet.PageLayout.Options then
+  if poDefaultOrientation in sheet.PageLayout.Options then
     Result := Result or $0040;
-  if poUseStartPageNumber in FWorksheet.PageLayout.Options then
+  if poUseStartPageNumber in sheet.PageLayout.Options then
     Result := Result or $0080;
 end;
 
@@ -3619,7 +3670,7 @@ end;
   Populates the color palette of the BIFF writer. Must be overridden by
   descendants.
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFFWriter.PopulatePalette(AWorkbook: TsWorkbook);
+procedure TsSpreadBIFFWriter.PopulatePalette(AWorkbook: TsBasicWorkbook);
 begin
   Unused(AWorkbook);
   FPalette.Clear;
@@ -3779,9 +3830,9 @@ begin
     { calculate width to be in units of 1/256 of pixel width of character "0" }
     case ACol^.ColWidthType of
       cwtDefault:
-        width := FWorksheet.ReadDefaultColWidth(suChars);
+        width := (FWorksheet as TsWorksheet).ReadDefaultColWidth(suChars);
       cwtCustom:
-        width := FWorkbook.ConvertUnits(ACol^.Width, FWorkbook.Units, suChars);
+        width := (FWorkbook as TsWorkbook).ConvertUnits(ACol^.Width, FWorkbook.Units, suChars);
     end;
     w := round(width * 256);
 
@@ -3799,13 +3850,14 @@ end;
   Writes the column info records for all used columns.
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFWriter.WriteColInfos(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   j: Integer;
   col: PCol;
+  sheet: TsWorksheet absolute ASheet;
 begin
-  for j := 0 to ASheet.Cols.Count-1 do begin
-    col := PCol(ASheet.Cols[j]);
+  for j := 0 to sheet.Cols.Count-1 do begin
+    col := PCol(sheet.Cols[j]);
     WriteColInfo(AStream, col);
   end;
 end;
@@ -3828,7 +3880,7 @@ var
 begin
   Unused(ACell);
 
-  comment := FWorksheet.FindComment(ACell);
+  comment := (FWorksheet as TsWorksheet).FindComment(ACell);
   if (comment = nil) or (comment^.Text = '') then
     exit;
 
@@ -3909,7 +3961,7 @@ end;
   Valud for BIFF2-BIFF8.
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFWriter.WriteDefaultColWidth(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   w: Single;
 begin
@@ -3918,7 +3970,7 @@ begin
 
   { Column width in characters, using the width of the zero character
   from default font (first FONT record in the file). }
-  w := AWorksheet.ReadDefaultColWidth(suChars);
+  w := (AWorksheet as TsWorksheet).ReadDefaultColWidth(suChars);
   AStream.WriteWord(round(w));
 end;
 
@@ -3929,7 +3981,7 @@ end;
   Valid for BIFF3-BIFF8.
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFWriter.WriteDefaultRowHeight(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   h: Double;
 begin
@@ -3944,13 +3996,13 @@ begin
   AStream.WriteWord(WordToLE($0001));
 
   { Default height for unused rows, in twips = 1/20 of a point }
-  h := AWorksheet.ReadDefaultRowHeight(suPoints);  // h is in points
+  h := (AWorksheet as TsWorksheet).ReadDefaultRowHeight(suPoints);  // h is in points
   AStream.WriteWord(WordToLE(PtsToTwips(h)));      // write as twips
 end;
 
 procedure TsSpreadBIFFWriter.WriteDefinedName(AStream: TStream;
-  AWorksheet: TsWorksheet; const AName: String; AIndexToREF, ASheetIndex: Word;
-  AKind: TsBIFFExternKind);
+  AWorksheet: TsBasicWorksheet; const AName: String;
+  AIndexToREF, ASheetIndex: Word; AKind: TsBIFFExternKind);
 begin
   Unused(AStream, AWorksheet);
   Unused(Aname, AIndexToREF);
@@ -3960,19 +4012,22 @@ end;
 
 procedure TsSpreadBIFFWriter.WriteDefinedNames(AStream: TStream);
 var
+  book: TsWorkbook;
   sheet: TsWorksheet;
   i: Integer;
   extSheetIdx: Integer;
   sheetList: TsBIFFExternSheetList;
 begin
+  book := FWorkbook as TsWorkbook;
+
   { Find sheetlist of global link table }
   sheetList := FLinkLists.GetGlobalLinks;
   if sheetList = nil then
     exit;
 
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do
+  for i:=0 to book.GetWorksheetCount-1 do
   begin
-    sheet := FWorkbook.GetWorksheetByIndex(i);
+    sheet := book.GetWorksheetByIndex(i) as TsWorksheet;
     extSheetIdx := sheetList.IndexOfSheet(sheet.Name);
     if (sheet.PageLayout.NumPrintRanges > 0) or
        sheet.PageLayout.HasRepeatedCols or sheet.PageLayout.HasRepeatedRows then
@@ -4141,12 +4196,13 @@ begin
   // the MARGIN IDs are consecutive beginning with the one for left margin
 
   { Page margin value, written in inches }
-  case AMargin of
-    0: dbl := FWorksheet.PageLayout.LeftMargin;
-    1: dbl := FWorksheet.PageLayout.RightMargin;
-    2: dbl := FWorksheet.PageLayout.TopMargin;
-    3: dbl := FWorksheet.PageLayout.Bottommargin;
-  end;
+  with (FWorksheet as TsWorksheet).PageLayout do
+    case AMargin of
+      0: dbl := LeftMargin;
+      1: dbl := RightMargin;
+      2: dbl := TopMargin;
+      3: dbl := Bottommargin;
+    end;
   dbl := mmToIn(dbl);
   AStream.WriteBuffer(dbl, SizeOf(dbl));
 end;
@@ -4199,7 +4255,7 @@ procedure TsSpreadBIFFWriter.WriteFormula(AStream: TStream;
 var
   formula: TsRPNFormula;
 begin
-  formula := FWorksheet.BuildRPNFormula(ACell);
+  formula := (FWorksheet as TsWorksheet).BuildRPNFormula(ACell);
   WriteRPNFormula(AStream, ARow, ACol, formula, ACell);
   SetLength(formula, 0);
 end;
@@ -4216,7 +4272,7 @@ begin
   WriteBIFFHeader(AStream, INT_EXCEL_ID_HCENTER, SizeOf(w));
 
   { Data }
-  if poHorCentered in FWorksheet.PageLayout.Options then w := 1 else w := 0;
+  w := IfThen(poHorCentered in TsWorksheet(FWorksheet).PageLayout.Options, 1, 0);
   AStream.WriteWord(WordToLE(w));
 end;
 
@@ -4231,7 +4287,7 @@ var
   len: Integer;
   id: Word;
 begin
-  with FWorksheet.PageLayout do
+  with (FWorksheet as TsWorksheet).PageLayout do
     if AIsHeader then
     begin
       if (Headers[HEADER_FOOTER_INDEX_ALL] = '') then
@@ -4323,15 +4379,15 @@ end;
   protection is not active.
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFWriter.WriteObjectProtect(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   w: Word;
 begin
-  if not ASheet.IsProtected then
+  if not (ASheet as TsWorksheet).IsProtected then
     exit;
 
   WriteBIFFHeader(AStream, INT_EXCEL_ID_OBJECTPROTECT, 2);
-  w := IfThen(spObjects in ASheet.Protection, 1, 0);
+  w := IfThen(spObjects in (ASheet as TsWorksheet).Protection, 1, 0);
   AStream.WriteWord(WordToLE(w));
 end;
 
@@ -4344,17 +4400,20 @@ var
   dbl: Double;
   i: Integer;
   w: Word;
+  pglayout: TsPageLayout;
 begin
+  pglayout := (FWorksheet as TsWorksheet).PageLayout;
+
   { BIFF record header }
   WriteBIFFHeader(AStream, INT_EXCEL_ID_PAGESETUP, 9*2 + 2*8);
 
   { Paper size }
   w := 0;
   for i:=0 to High(PAPER_SIZES) do
-    if (SameValue(PAPER_SIZES[i,0], FWorksheet.PageLayout.PageHeight) and
-        SameValue(PAPER_SIZES[i,1], FWorksheet.PageLayout.PageWidth))
-    or (SameValue(PAPER_SIZES[i,1], FWorksheet.PageLayout.PageHeight) and
-        SameValue(PAPER_SIZES[i,0], FWorksheet.PageLayout.PageWidth))
+    if (SameValue(PAPER_SIZES[i,0], pgLayout.PageHeight) and
+        SameValue(PAPER_SIZES[i,1], pgLayout.PageWidth))
+    or (SameValue(PAPER_SIZES[i,1], pgLayout.PageHeight) and
+        SameValue(PAPER_SIZES[i,0], pgLayout.PageWidth))
     then begin
       w := i;
       break;
@@ -4362,19 +4421,19 @@ begin
   AStream.WriteWord(WordToLE(w));
 
   { Scaling factor in percent }
-  w := FWorksheet.PageLayout.ScalingFactor;
+  w := pgLayout.ScalingFactor;
   AStream.WriteWord(WordToLE(w));
 
   { Start page number }
-  w := FWorksheet.PageLayout.StartPageNumber;
+  w := pgLayout.StartPageNumber;
   AStream.WriteWord(WordToLE(w));
 
   { Fit worksheet width to this number of pages, 0 = use as many as needed }
-  w := FWorksheet.PageLayout.FitWidthToPages;
+  w := pgLayout.FitWidthToPages;
   AStream.WriteWord(WordToLE(w));
 
   { Fit worksheet height to this number of pages, 0 = use as many as needed }
-  w := FWorksheet.PageLayout.FitHeightToPages;
+  w := pgLayout.FitHeightToPages;
   AStream.WriteWord(WordToLE(w));
 
   { Options:
@@ -4403,15 +4462,15 @@ begin
   AStream.WriteWord(WordToLE(600));
 
   { Header margin }
-  dbl := mmToIn(FWorksheet.PageLayout.HeaderMargin);
+  dbl := mmToIn(pgLayout.HeaderMargin);
   AStream.WriteBuffer(dbl, SizeOf(dbl));
 
   { Footer margin }
-  dbl := mmToIn(FWorksheet.PageLayout.FooterMargin);
+  dbl := mmToIn(pgLayout.FooterMargin);
   AStream.WriteBuffer(dbl, SizeOf(dbl));
 
   { Number of copies to print }
-  w := FWorksheet.PageLayout.Copies;
+  w := pgLayout.Copies;
   AStream.WriteWord(WordToLE(w));
 end;
 
@@ -4427,19 +4486,20 @@ end;
   |         |   |     2     |  |     |     |   |  2  |  0  |
    ---------     ----------     -----------     -----------  </pre>
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFFWriter.WritePane(AStream: TStream; ASheet: TsWorksheet;
-  IsBiff58: Boolean; out ActivePane: Byte);
+procedure TsSpreadBIFFWriter.WritePane(AStream: TStream;
+  ASheet: TsBasicWorksheet; IsBiff58: Boolean; out ActivePane: Byte);
 var
   n: Word;
+  sheet: TsWorksheet absolute ASheet;
 begin
   ActivePane := 3;
 
-  if not (soHasFrozenPanes in ASheet.Options) then
+  if not (soHasFrozenPanes in sheet.Options) then
     exit;
-  if (ASheet.LeftPaneWidth = 0) and (ASheet.TopPaneHeight = 0) then
+  if (sheet.LeftPaneWidth = 0) and (sheet.TopPaneHeight = 0) then
     exit;
 
-  if not (soHasFrozenPanes in ASheet.Options) then
+  if not (soHasFrozenPanes in sheet.Options) then
     exit;
   { Non-frozen panes should work in principle, but they are not read without
     error. They possibly require an additional SELECTION record. }
@@ -4451,34 +4511,34 @@ begin
   { Position of the vertical split (px, 0 = No vertical split):
     - Unfrozen pane: Width of the left pane(s) (in twips = 1/20 of a point)
     - Frozen pane: Number of visible columns in left pane(s) }
-  AStream.WriteWord(WordToLE(ASheet.LeftPaneWidth));
+  AStream.WriteWord(WordToLE(sheet.LeftPaneWidth));
 
   { Position of the horizontal split (py, 0 = No horizontal split):
     - Unfrozen pane: Height of the top pane(s) (in twips = 1/20 of a point)
     - Frozen pane: Number of visible rows in top pane(s) }
-  AStream.WriteWord(WordToLE(ASheet.TopPaneHeight));
+  AStream.WriteWord(WordToLE(sheet.TopPaneHeight));
 
   { Index to first visible row in bottom pane(s) }
   if (soHasFrozenPanes in ASheet.Options) then
-    AStream.WriteWord(WordToLE(ASheet.TopPaneHeight))
+    AStream.WriteWord(WordToLE(sheet.TopPaneHeight))
   else
-    AStream.WriteWord(WordToLE(0));
+    AStream.WriteWord(0);
 
   { Index to first visible column in right pane(s) }
-  if (soHasFrozenPanes in ASheet.Options) then
-    AStream.WriteWord(WordToLE(ASheet.LeftPaneWidth))
+  if (soHasFrozenPanes in sheet.Options) then
+    AStream.WriteWord(WordToLE(sheet.LeftPaneWidth))
   else
-    AStream.WriteWord(WordToLE(0));
+    AStream.WriteWord(0);
 
   { Identifier of pane with active cell cursor, see header for numbering scheme }
-  if (soHasFrozenPanes in ASheet.Options) then begin
-    if (ASheet.LeftPaneWidth = 0) and (ASheet.TopPaneHeight = 0) then
+  if (soHasFrozenPanes in sheet.Options) then begin
+    if (sheet.LeftPaneWidth = 0) and (sheet.TopPaneHeight = 0) then
       ActivePane := 3
     else
-    if (ASheet.LeftPaneWidth = 0) then
+    if (sheet.LeftPaneWidth = 0) then
       ActivePane := 2
     else
-    if (ASheet.TopPaneHeight =0) then
+    if (sheet.TopPaneHeight =0) then
       ActivePane := 1
     else
       ActivePane := 0;
@@ -4529,7 +4589,7 @@ begin
   WriteBIFFHeader(AStream, INT_EXCEL_ID_PRINTGRID, SizeOf(w));
 
   { Data }
-  if poPrintGridLines in FWorksheet.PageLayout.Options then w := 1 else w := 0;
+  w := IfThen(poPrintGridLines in TsWorksheet(FWorksheet).PageLayout.Options, 1, 0);
   AStream.WriteWord(WordToLE(w));
 end;
 
@@ -4544,7 +4604,7 @@ begin
   WriteBIFFHeader(AStream, INT_EXCEL_ID_PRINTHEADERS, SizeOf(w));
 
   { Data }
-  if poPrintHeaders in FWorksheet.PageLayout.Options then w := 1 else w := 0;
+  w := IfThen(poPrintHeaders in TsWorksheet(FWorksheet).PageLayout.Options, 1, 0);
   AStream.WriteWord(WordToLE(w));
 end;
 
@@ -4567,7 +4627,7 @@ end;
   Writes an Excel 3-8 ROW record
   Valid for BIFF3-BIFF8
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFFWriter.WriteRow(AStream: TStream; ASheet: TsWorksheet;
+procedure TsSpreadBIFFWriter.WriteRow(AStream: TStream; ASheet: TsBasicWorksheet;
   ARowIndex, AFirstColIndex, ALastColIndex: Cardinal; ARow: PRow);
 var
   w: Word;
@@ -4577,6 +4637,8 @@ var
   colindex: Cardinal;
   rowheight: Word;
   fmt: PsCellFormat;
+  sheet: TsWorksheet;
+  book: TsWorkbook;
 begin
   if (ARowIndex >= FLimitations.MaxRowCount) or
      (AFirstColIndex >= FLimitations.MaxColCount) or
@@ -4584,16 +4646,19 @@ begin
   then
     exit;
 
+  sheet := TsWorksheet(ASheet);
+  book := TsWorkbook(FWorkbook);
+
   // Check for additional space above/below row
   spaceabove := false;
   spacebelow := false;
   colindex := AFirstColIndex;
   while colindex <= ALastColIndex do
   begin
-    cell := ASheet.FindCell(ARowindex, colindex);
+    cell := sheet.FindCell(ARowindex, colindex);
     if (cell <> nil) then
     begin
-      fmt := Workbook.GetPointerToCellFormat(cell^.FormatIndex);
+      fmt := book.GetPointerToCellFormat(cell^.FormatIndex);
       if (uffBorder in fmt^.UsedFormattingFields) then
       begin
         if (cbNorth in fmt^.Border) and (fmt^.BorderStyles[cbNorth].LineStyle = lsThick)
@@ -4620,9 +4685,9 @@ begin
 
   { Row height (in twips, 1/20 point) and info on custom row height }
   if (ARow = nil) or (ARow^.RowHeightType = rhtDefault) then
-    rowheight := PtsToTwips(ASheet.ReadDefaultRowHeight(suPoints))
+    rowheight := PtsToTwips(sheet.ReadDefaultRowHeight(suPoints))
   else
-    rowheight := PtsToTwips(FWorkbook.ConvertUnits(ARow^.Height, FWorkbook.Units, suPoints));
+    rowheight := PtsToTwips(book.ConvertUnits(ARow^.Height, book.Units, suPoints));
   w := rowheight and $7FFF;
   AStream.WriteWord(WordToLE(w));
 
@@ -4650,20 +4715,22 @@ end;
   groups of 32, followed by the cells on these rows, etc. THIS IS NOT NECESSARY!
   Valid for BIFF2-BIFF8.
 -------------------------------------------------------------------------------}
-procedure TsSpreadBIFFWriter.WriteRows(AStream: TStream; ASheet: TsWorksheet);
+procedure TsSpreadBIFFWriter.WriteRows(AStream: TStream;
+  ASheet: TsBasicWorksheet);
 var
   row: PRow;
   i: Integer;
   cell1, cell2: PCell;
+  sheet: TsWorksheet absolute ASheet;
 begin
-  for i := 0 to ASheet.Rows.Count-1 do begin
-    row := ASheet.Rows[i];
-    cell1 := ASheet.Cells.GetFirstCellOfRow(row^.Row);
+  for i := 0 to sheet.Rows.Count-1 do begin
+    row := sheet.Rows[i];
+    cell1 := sheet.Cells.GetFirstCellOfRow(row^.Row);
     if cell1 <> nil then begin
-      cell2 := ASheet.Cells.GetLastCellOfRow(row^.Row);
-      WriteRow(AStream, ASheet, row^.Row, cell1^.Col, cell2^.Col, row);
+      cell2 := sheet.Cells.GetLastCellOfRow(row^.Row);
+      WriteRow(AStream, sheet, row^.Row, cell1^.Col, cell2^.Col, row);
     end else
-      WriteRow(AStream, ASheet, row^.Row, 0, 0, row);
+      WriteRow(AStream, sheet, row^.Row, 0, 0, row);
   end;
 end;
 
@@ -5131,7 +5198,7 @@ end;
   Writes the SCL record - this is the current magnification factor of the sheet
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFWriter.WriteSCLRecord(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   num, denom: Word;
 begin
@@ -5142,7 +5209,7 @@ begin
   WriteBIFFHeader(AStream, INT_EXCEL_ID_SCL, 4);
 
   denom := 100;
-  num := round(ASheet.ZoomFactor * denom);
+  num := round((ASheet as TsWorksheet).ZoomFactor * denom);
 
   { Numerator }
   AStream.WriteWord(WordToLE(num));
@@ -5157,28 +5224,33 @@ end;
   Valid for BIFF2-BIFF8
 -------------------------------------------------------------------------------}
 procedure TsSpreadBIFFWriter.WriteSELECTION(AStream: TStream;
-  ASheet: TsWorksheet; APane: Byte);
+  ASheet: TsBasicWorksheet; APane: Byte);
 var
   activeCellRow, activeCellCol: Word;
   i, n: Integer;
   sel: TsCellRange;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
-  if FWorkbook.ActiveWorksheet <> nil then
+  book := FWorkbook as TsWorkbook;
+  sheet := ASheet as TsWorksheet;
+
+  if book.ActiveWorksheet <> nil then
   begin
-    activeCellRow := FWorksheet.ActiveCellRow;
-    activeCellCol := FWorksheet.ActiveCellCol;
+    activeCellRow := sheet.ActiveCellRow;
+    activeCellCol := sheet.ActiveCellCol;
   end else
     case APane of
       0: begin   // right-bottom
-           activeCellRow := ASheet.TopPaneHeight;
-           activeCellCol := ASheet.LeftPaneWidth;
+           activeCellRow := sheet.TopPaneHeight;
+           activeCellCol := sheet.LeftPaneWidth;
          end;
       1: begin   // right-top
            activeCellRow := 0;
-           activeCellCol := ASheet.LeftPaneWidth;
+           activeCellCol := sheet.LeftPaneWidth;
          end;
       2: begin   // left-bottom
-           activeCellRow := ASheet.TopPaneHeight;
+           activeCellRow := sheet.TopPaneHeight;
            activeCellCol := 0;
          end;
       3: begin   // left-top
@@ -5200,12 +5272,12 @@ begin
   AStream.WriteWord(WordToLE(activeCellCol));
 
   { Index into the following cell range list to the entry that contains the active cell }
-  i := Max(0, ASheet.GetSelectionRangeIndexOfActiveCell);
+  i := Max(0, sheet.GetSelectionRangeIndexOfActiveCell);
   AStream.WriteWord(WordToLE(i));
 
   { Cell range array }
 
-  n := ASheet.GetSelectionCount;
+  n := sheet.GetSelectionCount;
   // Case 1: no selection
   if n = 0 then
   begin
@@ -5226,7 +5298,7 @@ begin
     // Write each selected cell range
     for i := 0 to n-1 do
     begin
-      sel := ASheet.GetSelection[i];
+      sel := sheet.GetSelection[i];
       // Index to first and last row of this selected range
       AStream.WriteWord(WordToLE(sel.Row1));
       AStream.WriteWord(WordToLE(sel.Row2));
@@ -5239,14 +5311,17 @@ begin
 end;
 
 procedure TsSpreadBIFFWriter.WriteSelections(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
+var
+  sheet: TsWorksheet absolute ASheet;
 begin
   WriteSelection(AStream, ASheet, 3);
-  if (ASheet.LeftPaneWidth = 0) then begin
-    if ASheet.TopPaneHeight > 0 then WriteSelection(AStream, ASheet, 2);
+  if (sheet.LeftPaneWidth = 0) then begin
+    if sheet.TopPaneHeight > 0 then
+      WriteSelection(AStream, ASheet, 2);
   end else begin
     WriteSelection(AStream, ASheet, 1);
-    if ASheet.TopPaneHeight > 0 then begin
+    if sheet.TopPaneHeight > 0 then begin
       WriteSelection(AStream, ASheet, 2);
       WriteSelection(AStream, ASheet, 0);
     end;
@@ -5339,7 +5414,7 @@ begin
         or $0080  // Outline buttons right of outline groups
         or $0400; // Show outline symbols
 
-  if (poFitPages in FWorksheet.PageLayout.Options) then
+  if (poFitPages in TsWorksheet(FWorksheet).PageLayout.Options) then
     flags := flags or $0100;  // Fit printout to number of pages
 
   AStream.WriteWord(WordToLE(flags));
@@ -5387,34 +5462,35 @@ begin
   WriteBIFFHeader(AStream, INT_EXCEL_ID_VCENTER, SizeOf(w));
 
   { Data }
-  if poVertCentered in FWorksheet.PageLayout.Options then w := 1 else w := 0;
+  w := IfThen(poVertCentered in TsWorksheet(FWorksheet).PageLayout.Options, 1, 0);
   AStream.WriteWord(WordToLE(w));
 end;
 
 procedure TsSpreadBIFFWriter.WriteVirtualCells(AStream: TStream;
-  ASheet: TsWorksheet);
+  ASheet: TsBasicWorksheet);
 var
   r,c: Cardinal;
   lCell: TCell;
   value: variant;
   styleCell: PCell;
+  sheet: TsWorksheet absolute ASheet;
 begin
-  if ASheet.VirtualRowCount = 0 then
+  if sheet.VirtualRowCount = 0 then
     exit;
-  if ASheet.VirtualColCount = 0 then
+  if sheet.VirtualColCount = 0 then
     exit;
-  if not Assigned(ASheet.OnWriteCellData) then
+  if not Assigned(sheet.OnWriteCellData) then
     exit;
 
-  for r := 0 to LongInt(ASheet.VirtualRowCount) - 1 do
-    for c := 0 to LongInt(ASheet.VirtualColCount) - 1 do
+  for r := 0 to LongInt(sheet.VirtualRowCount) - 1 do
+    for c := 0 to LongInt(sheet.VirtualColCount) - 1 do
     begin
       lCell.Row := r; // to silence a compiler hint...
       InitCell(lCell);
       lCell.Worksheet := ASheet;
       value := varNull;
       styleCell := nil;
-      ASheet.OnWriteCellData(ASheet, r, c, value, styleCell);
+      sheet.OnWriteCellData(sheet, r, c, value, styleCell);
       if styleCell <> nil then lCell := styleCell^;
       lCell.Row := r;
       lCell.Col := c;
@@ -5462,7 +5538,10 @@ end;
 procedure TsSpreadBIFFWriter.WriteWindow1(AStream: TStream);
 var
   actSheet: Integer;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   { BIFF Record header }
   WriteBIFFHeader(AStream, INT_EXCEL_ID_WINDOW1, 18);
 
@@ -5485,9 +5564,9 @@ begin
    MASK_WINDOW1_OPTION_WORKSHEET_TAB_VISIBLE));
 
   { Index to active (displayed) worksheet }
-  if FWorkbook.ActiveWorksheet = nil then
+  if book.ActiveWorksheet = nil then
     actSheet := 0 else
-    actSheet := FWorkbook.GetWorksheetIndex(FWorkbook.ActiveWorksheet);
+    actSheet := book.GetWorksheetIndex(book.ActiveWorksheet);
   AStream.WriteWord(WordToLE(actSheet));
 
   { Index of first visible tab in the worksheet tab bar }
@@ -5568,8 +5647,8 @@ begin
 
   // Add all further non-standard format records
   // The first style was already added --> begin loop with 1
-  for i:=1 to Workbook.GetNumCellFormats - 1 do
-    WriteXF(AStream, Workbook.GetPointerToCellFormat(i), 0);
+  for i:=1 to TsWorkbook(FWorkbook).GetNumCellFormats - 1 do
+    WriteXF(AStream, TsWorkbook(Workbook).GetPointerToCellFormat(i), 0);
 end;
 
 
diff --git a/components/fpspreadsheet/source/common/xlsxml.pas b/components/fpspreadsheet/source/common/xlsxml.pas
index 2c1aa8f89..a22a0964e 100644
--- a/components/fpspreadsheet/source/common/xlsxml.pas
+++ b/components/fpspreadsheet/source/common/xlsxml.pas
@@ -23,7 +23,7 @@ interface
 uses
   Classes, SysUtils,
   laz2_xmlread, laz2_DOM,
-  fpsTypes, fpspreadsheet, fpsReaderWriter, xlsCommon;
+  fpsTypes, fpsReaderWriter, xlsCommon;
 
 type
 
@@ -35,21 +35,21 @@ type
     FPointSeparatorSettings: TFormatSettings;
     function GetCommentStr(ACell: PCell): String;
     function GetFormulaStr(ACell: PCell): String;
-    function GetFrozenPanesStr(AWorksheet: TsWorksheet; AIndent: String): String;
+    function GetFrozenPanesStr(AWorksheet: TsBasicWorksheet; AIndent: String): String;
     function GetHyperlinkStr(ACell: PCell): String;
     function GetIndexStr(AIndex: Integer): String;
-    function GetLayoutStr(AWorksheet: TsWorksheet): String;
+    function GetLayoutStr(AWorksheet: TsBasicWorksheet): String;
     function GetMergeStr(ACell: PCell): String;
-    function GetPageFooterStr(AWorksheet: TsWorksheet): String;
-    function GetPageHeaderStr(AWorksheet: TsWorksheet): String;
-    function GetPageMarginStr(AWorksheet: TsWorksheet): String;
+    function GetPageFooterStr(AWorksheet: TsBasicWorksheet): String;
+    function GetPageHeaderStr(AWorksheet: TsBasicWorksheet): String;
+    function GetPageMarginStr(AWorksheet: TsBasicWorksheet): String;
     function GetStyleStr(AFormatIndex: Integer): String;
     procedure WriteExcelWorkbook(AStream: TStream);
     procedure WriteStyle(AStream: TStream; AIndex: Integer);
     procedure WriteStyles(AStream: TStream);
-    procedure WriteTable(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteWorksheet(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteWorksheetOptions(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteTable(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteWorksheet(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteWorksheetOptions(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteWorksheets(AStream: TStream);
 
   protected
@@ -68,7 +68,7 @@ type
       const AValue: double; ACell: PCell); override;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     procedure WriteToStream(AStream: TStream; AParams: TsStreamParams = []); override;
 
   end;
@@ -90,7 +90,7 @@ implementation
 
 uses
   StrUtils, Math,
-  fpsStrings, fpsUtils, fpsNumFormat, fpsXmlCommon, fpsHTMLUtils;
+  fpsStrings, fpspreadsheet, fpsUtils, fpsNumFormat, fpsXmlCommon, fpsHTMLUtils;
 
 const
   FMT_OFFSET   = 61;
@@ -164,7 +164,7 @@ end;
   Defines the date mode and the limitations of the file format.
   Initializes the format settings to be used when writing to xml.
 -------------------------------------------------------------------------------}
-constructor TsSpreadExcelXMLWriter.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadExcelXMLWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -186,7 +186,7 @@ var
   comment: PsComment;
 begin
   Result := '';
-  comment := FWorksheet.FindComment(ACell);
+  comment := (FWorksheet as TsWorksheet).FindComment(ACell);
   if Assigned(comment) then
     Result := INDENT1 + '<Comment><Data>' + comment^.Text + '</Data></Comment>' + LF + CELL_INDENT;
   // If there will be some rich-text-like formatting in the future, use
@@ -197,40 +197,41 @@ function TsSpreadExcelXMLWriter.GetFormulaStr(ACell: PCell): String;
 begin
   if HasFormula(ACell) then
   begin
-    Result := UTF8TextToXMLText(FWorksheet.ConvertFormulaDialect(ACell, fdExcelR1C1));
+    Result := UTF8TextToXMLText((FWorksheet as TsWorksheet).ConvertFormulaDialect(ACell, fdExcelR1C1));
     Result := ' ss:Formula="=' + Result + '"';
   end else
     Result := '';
 end;
 
-function TsSpreadExcelXMLWriter.GetFrozenPanesStr(AWorksheet: TsWorksheet;
+function TsSpreadExcelXMLWriter.GetFrozenPanesStr(AWorksheet: TsBasicWorksheet;
   AIndent: String): String;
 var
   activePane: Integer;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  if (soHasFrozenPanes in AWorksheet.Options) then
+  if (soHasFrozenPanes in sheet.Options) then
   begin
     Result := AIndent +
         '<FreezePanes/>' + LF + AIndent +
         '<FrozenNoSplit/>' + LF;
 
-    if FWorksheet.LeftPaneWidth > 0 then
+    if sheet.LeftPaneWidth > 0 then
       Result := Result + AIndent +
         '<SplitVertical>1</SplitVertical>' + LF + AIndent +
-        '<LeftColumnRightPane>' + IntToStr(FWorksheet.LeftPaneWidth) + '</LeftColumnRightPane>' + LF;
+        '<LeftColumnRightPane>' + IntToStr(sheet.LeftPaneWidth) + '</LeftColumnRightPane>' + LF;
 
-    if FWorksheet.TopPaneHeight > 0 then
+    if sheet.TopPaneHeight > 0 then
       Result := Result + AIndent +
         '<SplitHorizontal>1</SplitHorizontal>' + LF + AIndent +
-        '<TopRowBottomPane>' + IntToStr(FWorksheet.TopPaneHeight) + '</TopRowBottomPane>' + LF;
+        '<TopRowBottomPane>' + IntToStr(sheet.TopPaneHeight) + '</TopRowBottomPane>' + LF;
 
-    if (FWorksheet.LeftPaneWidth = 0) and (FWorkSheet.TopPaneHeight = 0) then
+    if (sheet.LeftPaneWidth = 0) and (sheet.TopPaneHeight = 0) then
       activePane := 3
     else
-    if (FWorksheet.LeftPaneWidth = 0) then
+    if (sheet.LeftPaneWidth = 0) then
       activePane := 2
     else
-    if (FWorksheet.TopPaneHeight = 0) then
+    if (sheet.TopPaneHeight = 0) then
       activePane := 1
     else
       activePane := 0;
@@ -245,7 +246,7 @@ var
   hyperlink: PsHyperlink;
 begin
   Result := '';
-  hyperlink := FWorksheet.FindHyperlink(ACell);
+  hyperlink := (FWorksheet as TsWorksheet).FindHyperlink(ACell);
   if Assigned(hyperlink) then
     Result := ' ss:HRef="' + hyperlink^.Target + '"';
 end;
@@ -255,17 +256,19 @@ begin
   Result := Format(' ss:Index="%d"', [AIndex]);
 end;
 
-function TsSpreadExcelXMLWriter.GetLayoutStr(AWorksheet: TsWorksheet): String;
+function TsSpreadExcelXMLWriter.GetLayoutStr(AWorksheet: TsBasicWorksheet): String;
+var
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   Result := '';
-  if AWorksheet.PageLayout.Orientation = spoLandscape then
+  if sheet.PageLayout.Orientation = spoLandscape then
     Result := Result + ' x:Orientation="Landscape"';
-  if (poHorCentered in AWorksheet.PageLayout.Options) then
+  if (poHorCentered in sheet.PageLayout.Options) then
     Result := Result + ' x:CenterHorizontal="1"';
-  if (poVertCentered in AWorksheet.PageLayout.Options) then
+  if (poVertCentered in sheet.PageLayout.Options) then
     Result := Result + ' x:CenterVertical="1"';
-  if (poUseStartPageNumber in AWorksheet.PageLayout.Options) then
-    Result := Result + ' x:StartPageNumber="' + IntToStr(AWorksheet.PageLayout.StartPageNumber) + '"';
+  if (poUseStartPageNumber in sheet.PageLayout.Options) then
+    Result := Result + ' x:StartPageNumber="' + IntToStr(sheet.PageLayout.StartPageNumber) + '"';
   Result := '<Layout' + Result + '/>';
 end;
 
@@ -274,8 +277,8 @@ var
   r1, c1, r2, c2: Cardinal;
 begin
   Result := '';
-  if FWorksheet.IsMerged(ACell) then begin
-    FWorksheet.FindMergedRange(ACell, r1, c1, r2, c2);
+  if (FWorksheet as TsWorksheet).IsMerged(ACell) then begin
+    (FWorksheet as TsWorksheet).FindMergedRange(ACell, r1, c1, r2, c2);
     if c2 > c1 then
       Result := Result + Format(' ss:MergeAcross="%d"', [c2-c1]);
     if r2 > r1 then
@@ -283,29 +286,38 @@ begin
   end;
 end;
 
-function TsSpreadExcelXMLWriter.GetPageFooterStr(AWorksheet: TsWorksheet): String;
+function TsSpreadExcelXMLWriter.GetPageFooterStr(
+  AWorksheet: TsBasicWorksheet): String;
+var
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  Result := Format('x:Margin="%g"', [mmToIn(AWorksheet.PageLayout.FooterMargin)], FPointSeparatorSettings);
-  if (AWorksheet.PageLayout.Footers[HEADER_FOOTER_INDEX_ALL] <> '') then
-    Result := Result + ' x:Data="' + UTF8TextToXMLText(AWorksheet.PageLayout.Footers[HEADER_FOOTER_INDEX_ALL], true) + '"';
+  Result := Format('x:Margin="%g"', [mmToIn(sheet.PageLayout.FooterMargin)], FPointSeparatorSettings);
+  if (sheet.PageLayout.Footers[HEADER_FOOTER_INDEX_ALL] <> '') then
+    Result := Result + ' x:Data="' + UTF8TextToXMLText(sheet.PageLayout.Footers[HEADER_FOOTER_INDEX_ALL], true) + '"';
   Result := '<Footer ' + result + '/>';
 end;
 
-function TsSpreadExcelXMLWriter.GetPageHeaderStr(AWorksheet: TsWorksheet): String;
+function TsSpreadExcelXMLWriter.GetPageHeaderStr(
+  AWorksheet: TsBasicWorksheet): String;
+var
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  Result := Format('x:Margin="%g"', [mmToIn(AWorksheet.PageLayout.HeaderMargin)], FPointSeparatorSettings);
-  if (AWorksheet.PageLayout.Headers[HEADER_FOOTER_INDEX_ALL] <> '') then
-    Result := Result + ' x:Data="' + UTF8TextToXMLText(AWorksheet.PageLayout.Headers[HEADER_FOOTER_INDEX_ALL], true) + '"';
+  Result := Format('x:Margin="%g"', [mmToIn(sheet.PageLayout.HeaderMargin)], FPointSeparatorSettings);
+  if (sheet.PageLayout.Headers[HEADER_FOOTER_INDEX_ALL] <> '') then
+    Result := Result + ' x:Data="' + UTF8TextToXMLText(sheet.PageLayout.Headers[HEADER_FOOTER_INDEX_ALL], true) + '"';
   Result := '<Header ' + Result + '/>';
 end;
 
-function TsSpreadExcelXMLWriter.GetPageMarginStr(AWorksheet: TsWorksheet): String;
+function TsSpreadExcelXMLWriter.GetPageMarginStr(
+  AWorksheet: TsBasicWorksheet): String;
+var
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   Result := Format('x:Bottom="%g" x:Left="%g" x:Right="%g" x:Top="%g"', [
-    mmToIn(AWorksheet.PageLayout.BottomMargin),
-    mmToIn(AWorksheet.PageLayout.LeftMargin),
-    mmToIn(AWorksheet.PageLayout.RightMargin),
-    mmToIn(AWorksheet.PageLayout.TopMargin)
+    mmToIn(sheet.PageLayout.BottomMargin),
+    mmToIn(sheet.PageLayout.LeftMargin),
+    mmToIn(sheet.PageLayout.RightMargin),
+    mmToIn(sheet.PageLayout.TopMargin)
     ], FPointSeparatorSettings);
   Result := '<PageMargins ' + Result + '/>';
 end;
@@ -366,7 +378,7 @@ begin
       WriteLabel(AStream, ACell^.Row, ACell^.Col, ACell^.UTF8StringValue, ACell);
   end;
 
-  if FWorksheet.ReadComment(ACell) <> '' then
+  if (FWorksheet as TsWorksheet).ReadComment(ACell) <> '' then
     WriteComment(AStream, ACell);
 end;
 
@@ -380,11 +392,11 @@ var
 begin
   Unused(ARow, ACol);
   ExcelDate := AValue;
-  fmt := FWorkbook.GetPointerToCellFormat(ACell^.FormatIndex);
+  fmt := (FWorkbook as TsWorkbook).GetPointerToCellFormat(ACell^.FormatIndex);
   // Times have an offset of 1 day!
   if (fmt <> nil) and (uffNumberFormat in fmt^.UsedFormattingFields) then
   begin
-    nfp := FWorkbook.GetNumberFormat(fmt^.NumberFormatIndex);
+    nfp := (FWorkbook as TsWorkbook).GetNumberFormat(fmt^.NumberFormatIndex);
     if IsTimeIntervalFormat(nfp) or IsTimeFormat(nfp) then
       case FDateMode of
         dm1900: ExcelDate := AValue + DATEMODE_1900_BASE;
@@ -461,8 +473,8 @@ begin
   if Length(ACell^.RichTextParams) > 0 then
   begin
     RichTextToHTML(
-      FWorkbook,
-      FWorksheet.ReadCellFont(ACell),
+      FWorkbook as TsWorkbook,
+      (FWorksheet as TsWorksheet).ReadCellFont(ACell),
       AValue,
       ACell^.RichTextParams,
       valueStr,             // html-formatted rich text
@@ -531,8 +543,10 @@ var
   fill: TsFillPattern;
   cb: TsCellBorder;
   cbs: TsCellBorderStyle;
+  book: TsWorkbook;
 begin
-  deffnt := FWorkbook.GetDefaultFont;
+  book := FWorkbook as TsWorkbook;
+  deffnt := book.GetDefaultFont;
   if AIndex = 0 then
   begin
     AppendToStream(AStream, Format(INDENT2 +
@@ -551,7 +565,7 @@ begin
     AppendToStream(AStream, Format(INDENT2 +
       '<Style ss:ID="s%d">' + LF, [AIndex + FMT_OFFSET]));
 
-    fmt := FWorkbook.GetPointerToCellFormat(AIndex);
+    fmt := book.GetPointerToCellFormat(AIndex);
 
     // Horizontal alignment
     fmtHor := '';
@@ -600,7 +614,7 @@ begin
     // Font
     if (uffFont in fmt^.UsedFormattingFields) then
     begin
-      fnt := FWorkbook.GetFont(fmt^.FontIndex);
+      fnt := book.GetFont(fmt^.FontIndex);
       s := '';
       if fnt.FontName <> deffnt.FontName then
         s := s + Format('ss:FontName="%s" ', [fnt.FontName]);
@@ -624,7 +638,7 @@ begin
     // Number Format
     if (uffNumberFormat in fmt^.UsedFormattingFields) then
     begin
-      nfp := FWorkbook.GetNumberFormat(fmt^.NumberFormatIndex);
+      nfp := book.GetNumberFormat(fmt^.NumberFormatIndex);
       AppendToStream(AStream, Format(INDENT3 +
         '<NumberFormat ss:Format="%s"/>' + LF, [UTF8TextToXMLText(nfp.NumFormatStr)]));
     end;
@@ -685,12 +699,14 @@ var
 begin
   AppendToStream(AStream, INDENT1 +
     '<Styles>' + LF);
-  for i:=0 to FWorkbook.GetNumCellFormats-1 do WriteStyle(AStream, i);
+  for i:=0 to (FWorkbook as TsWorkbook).GetNumCellFormats-1 do
+    WriteStyle(AStream, i);
   AppendToStream(AStream, INDENT1 +
     '</Styles>' + LF);
 end;
 
-procedure TsSpreadExcelXMLWriter.WriteTable(AStream: TStream; AWorksheet: TsWorksheet);
+procedure TsSpreadExcelXMLWriter.WriteTable(AStream: TStream;
+  AWorksheet: TsBasicWorksheet);
 var
   c, c1, c2: Cardinal;
   r, r1, r2: Cardinal;
@@ -700,27 +716,28 @@ var
   styleStr: String;
   col: PCol;
   row: PRow;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   r1 := 0;
   c1 := 0;
-  r2 := AWorksheet.GetLastRowIndex;
-  c2 := AWorksheet.GetLastColIndex;
+  r2 := sheet.GetLastRowIndex;
+  c2 := sheet.GetLastColIndex;
   AppendToStream(AStream, TABLE_INDENT + Format(
     '<Table ss:ExpandedColumnCount="%d" ss:ExpandedRowCount="%d" ' +
       'x:FullColumns="1" x:FullRows="1" ' +
       'ss:DefaultColumnWidth="%.2f" ' +
       'ss:DefaultRowHeight="%.2f">' + LF,
       [
-      AWorksheet.GetLastColIndex + 1, AWorksheet.GetLastRowIndex + 1,
-      AWorksheet.ReadDefaultColWidth(suPoints),
-      AWorksheet.ReadDefaultRowHeight(suPoints)
+      sheet.GetLastColIndex + 1, sheet.GetLastRowIndex + 1,
+      sheet.ReadDefaultColWidth(suPoints),
+      sheet.ReadDefaultRowHeight(suPoints)
       ],
       FPointSeparatorSettings
     ));
 
   for c := c1 to c2 do
   begin
-    col := FWorksheet.FindCol(c);
+    col := sheet.FindCol(c);
     styleStr := '';
     colWidthStr := '';
     if Assigned(col) then
@@ -728,7 +745,7 @@ begin
       // column width is needed in pts.
       if col^.ColWidthType = cwtCustom then
         colwidthStr := Format(' ss:Width="%0.2f" ss:AutoFitWidth="0"',
-          [FWorkbook.ConvertUnits(col^.Width, FWorkbook.Units, suPoints)],
+          [(FWorkbook as TsWorkbook).ConvertUnits(col^.Width, FWorkbook.Units, suPoints)],
           FPointSeparatorSettings);
       // column style
       if col^.FormatIndex > 0 then
@@ -740,13 +757,13 @@ begin
 
   for r := r1 to r2 do
   begin
-    row := FWorksheet.FindRow(r);
+    row := sheet.FindRow(r);
     styleStr := '';
     // Row height is needed in pts.
     if Assigned(row) then
     begin
       rowheightStr := Format(' ss:Height="%.2f"',
-        [FWorkbook.ConvertUnits(row^.Height, FWorkbook.Units, suPoints)],
+        [(FWorkbook as TsWorkbook).ConvertUnits(row^.Height, FWorkbook.Units, suPoints)],
         FPointSeparatorSettings
       );
       if row^.RowHeightType = rhtCustom then
@@ -760,10 +777,10 @@ begin
       '<Row %s%s>' + LF, [rowheightStr, styleStr]));
     for c := c1 to c2 do
     begin
-      cell := AWorksheet.FindCell(r, c);
+      cell := sheet.FindCell(r, c);
       if cell <> nil then
       begin
-        if FWorksheet.IsMerged(cell) and not FWorksheet.IsMergeBase(cell) then
+        if sheet.IsMerged(cell) and not sheet.IsMergeBase(cell) then
           Continue;
         WriteCellToStream(AStream, cell);
       end;
@@ -804,7 +821,7 @@ begin
 end;
 
 procedure TsSpreadExcelXMLWriter.WriteWorksheet(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   protectedStr: String;
 begin
@@ -827,7 +844,7 @@ begin
 end;
 
 procedure TsSpreadExcelXMLWriter.WriteWorksheetOptions(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   footerStr, headerStr: String;
   hideGridStr: String;
@@ -837,6 +854,7 @@ var
   marginStr: String;
   selectedStr: String;
   protectStr: String;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   // Orientation, some PageLayout.Options
   layoutStr := GetLayoutStr(AWorksheet);
@@ -864,7 +882,7 @@ begin
     hideHeadersStr := INDENT3 + '<DoNotDisplayHeadings/>' + LF else
     hideHeadersStr := '';
 
-  if FWorkbook.ActiveWorksheet = AWorksheet then
+  if (FWorkbook as TsWorkbook).ActiveWorksheet = AWorksheet then
     selectedStr := INDENT3 + '<Selected/>' + LF else
     selectedStr := '';
 
@@ -899,9 +917,11 @@ end;
 procedure TsSpreadExcelXMLWriter.WriteWorksheets(AStream: TStream);
 var
   i: Integer;
+  book: TsWorkbook;
 begin
-  for i:=0 to FWorkbook.GetWorksheetCount-1 do
-    WriteWorksheet(AStream, FWorkbook.GetWorksheetByIndex(i));
+  book := FWorkbook as TsWorkbook;
+  for i:=0 to book.GetWorksheetCount-1 do
+    WriteWorksheet(AStream, book.GetWorksheetByIndex(i));
 end;
 
 
diff --git a/components/fpspreadsheet/source/common/xlsxooxml.pas b/components/fpspreadsheet/source/common/xlsxooxml.pas
index 9912bdb2c..982af9b2a 100644
--- a/components/fpspreadsheet/source/common/xlsxooxml.pas
+++ b/components/fpspreadsheet/source/common/xlsxooxml.pas
@@ -41,7 +41,7 @@ uses
  {$ELSE}
   fpszipper,
  {$ENDIF}
-  fpsTypes, fpSpreadsheet, fpsUtils, fpsReaderWriter, fpsNumFormat, fpsPalette,
+  fpsTypes, fpsUtils, fpsReaderWriter, fpsNumFormat, fpsPalette,
   fpsxmlcommon, xlsCommon;
   
 type
@@ -63,45 +63,45 @@ type
     FLastRow, FLastCol: Cardinal;
     FWrittenByFPS: Boolean;
     procedure ApplyCellFormatting(ACell: PCell; XfIndex: Integer);
-    procedure ApplyHyperlinks(AWorksheet: TsWorksheet);
+    procedure ApplyHyperlinks(AWorksheet: TsBasicWorksheet);
     function FindCommentsFileName(ANode: TDOMNode): String;
     procedure ReadActiveSheet(ANode: TDOMNode; out ActiveSheetIndex: Integer);
     procedure ReadBorders(ANode: TDOMNode);
-    procedure ReadCell(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadCell(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadCellXfs(ANode: TDOMNode);
     function  ReadColor(ANode: TDOMNode): TsColor;
-    procedure ReadCols(ANode: TDOMNode; AWorksheet: TsWorksheet);
-    procedure ReadComments(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadCols(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
+    procedure ReadComments(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadDateMode(ANode: TDOMNode);
     procedure ReadDefinedNames(ANode: TDOMNode);
-    procedure ReadDimension(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadDimension(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadFileVersion(ANode: TDOMNode);
     procedure ReadFills(ANode: TDOMNode);
     function ReadFont(ANode: TDOMNode): Integer;
     procedure ReadFonts(ANode: TDOMNode);
-    procedure ReadHeaderFooter(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadHeaderFooter(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadHyperlinks(ANode: TDOMNode);
-    procedure ReadMergedCells(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadMergedCells(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadNumFormats(ANode: TDOMNode);
-    procedure ReadPageMargins(ANode: TDOMNode; AWorksheet: TsWorksheet);
-    procedure ReadPageSetup(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadPageMargins(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
+    procedure ReadPageSetup(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadPalette(ANode: TDOMNode);
-    procedure ReadPrintOptions(ANode: TDOMNode; AWorksheet: TsWorksheet);
-    procedure ReadRow(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadPrintOptions(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
+    procedure ReadRow(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadSharedStrings(ANode: TDOMNode);
-    procedure ReadSheetFormatPr(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadSheetFormatPr(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadSheetList(ANode: TDOMNode);
-    procedure ReadSheetProtection(ANode: TDOMNode; AWorksheet: TsWorksheet);
-    procedure ReadSheetViews(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadSheetProtection(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
+    procedure ReadSheetViews(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
     procedure ReadThemeElements(ANode: TDOMNode);
     procedure ReadThemeColors(ANode: TDOMNode);
     procedure ReadWorkbookProtection(ANode: TDOMNode);
-    procedure ReadWorksheet(ANode: TDOMNode; AWorksheet: TsWorksheet);
+    procedure ReadWorksheet(ANode: TDOMNode; AWorksheet: TsBasicWorksheet);
   protected
     FFirstNumFormatIndexInFile: Integer;
     procedure AddBuiltinNumFormats; override;
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
       AParams: TsStreamParams = []); override;
@@ -120,7 +120,7 @@ type
     FFillList: array of PsCellFormat;
     FBorderList: array of PsCellFormat;
     function GetActiveTab: String;
-    procedure Get_rId(AWorksheet: TsWorksheet;
+    procedure Get_rId(AWorksheet: TsBasicWorksheet;
       out AComment_rId, AFirstHyperlink_rId, ADrawing_rId, ADrawingHF_rId: Integer);
   protected
     procedure AddBuiltinNumFormats; override;
@@ -134,40 +134,40 @@ type
     function  PrepareFormula(const AFormula: String): String;
     procedure ResetStreams;
     procedure WriteBorderList(AStream: TStream);
-    procedure WriteCols(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteComments(AWorksheet: TsWorksheet);
+    procedure WriteCols(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteComments(AWorksheet: TsBasicWorksheet);
     procedure WriteDefinedNames(AStream: TStream);
-    procedure WriteDimension(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteDrawings(AWorksheet: TsWorksheet);
-    procedure WriteDrawingRels(AWorksheet: TsWorksheet);
+    procedure WriteDimension(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteDrawings(AWorksheet: TsBasicWorksheet);
+    procedure WriteDrawingRels(AWorksheet: TsBasicWorksheet);
 //    procedure WriteDrawingsOfSheet(AStream: TStream; AWorksheet: TsWorksheet);
     procedure WriteFillList(AStream: TStream);
     procedure WriteFont(AStream: TStream; AFont: TsFont; UseInStyleNode: Boolean);
     procedure WriteFontList(AStream: TStream);
-    procedure WriteHeaderFooter(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteHyperlinks(AStream: TStream; AWorksheet: TsWorksheet; rId: Integer);
-    procedure WriteMergedCells(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteHeaderFooter(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteHyperlinks(AStream: TStream; AWorksheet: TsBasicWorksheet; rId: Integer);
+    procedure WriteMergedCells(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteNumFormatList(AStream: TStream);
     procedure WritePalette(AStream: TStream);
-    procedure WritePageMargins(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WritePageSetup(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WritePrintOptions(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteSheetData(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteSheetFormatPr(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteSheetPr(AStream: TStream; AWorksheet: TsWorksheet);
-    procedure WriteSheetProtection(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WritePageMargins(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WritePageSetup(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WritePrintOptions(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteSheetData(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteSheetFormatPr(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteSheetPr(AStream: TStream; AWorksheet: TsBasicWorksheet);
+    procedure WriteSheetProtection(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteSheets(AStream: TStream);
-    procedure WriteSheetViews(AStream: TStream; AWorksheet: TsWorksheet);
+    procedure WriteSheetViews(AStream: TStream; AWorksheet: TsBasicWorksheet);
     procedure WriteStyleList(AStream: TStream; ANodeName: String);
-    procedure WriteVmlDrawings(AWorksheet: TsWorksheet);
-    procedure WriteVMLDrawings_Comments(AWorksheet: TsWorksheet);
-    procedure WriteVMLDrawings_HeaderFooterImages(AWorksheet: TsWorksheet);
-    procedure WriteVMLDrawingRels(AWorksheet: TsWorksheet);
+    procedure WriteVmlDrawings(AWorksheet: TsBasicWorksheet);
+    procedure WriteVMLDrawings_Comments(AWorksheet: TsBasicWorksheet);
+    procedure WriteVMLDrawings_HeaderFooterImages(AWorksheet: TsBasicWorksheet);
+    procedure WriteVMLDrawingRels(AWorksheet: TsBasicWorksheet);
     procedure WriteWorkbook(AStream: TStream);
     procedure WriteWorkbookProtection(AStream: TStream);
     procedure WriteWorkbookRels(AStream: TStream);
-    procedure WriteWorksheet(AWorksheet: TsWorksheet);
-    procedure WriteWorksheetRels(AWorksheet: TsWorksheet);
+    procedure WriteWorksheet(AWorksheet: TsBasicWorksheet);
+    procedure WriteWorksheetRels(AWorksheet: TsBasicWorksheet);
   protected
     { Streams with the contents of files }
     FSContentTypes: TStream;
@@ -211,7 +211,7 @@ type
       const AValue: double; ACell: PCell); override;
 
   public
-    constructor Create(AWorkbook: TsWorkbook); override;
+    constructor Create(AWorkbook: TsBasicWorkbook); override;
     { General writing methods }
     procedure WriteStringToFile(AFileName, AString: string);
     procedure WriteToStream(AStream: TStream; AParams: TsStreamParams = []); override;
@@ -236,7 +236,7 @@ implementation
 
 uses
   variants, strutils, math, lazutf8, LazFileUtils, uriparser,
-  {%H-}fpsPatches, fpsCrypto, fpsExprParser,
+  {%H-}fpsPatches, fpSpreadsheet, fpsCrypto, fpsExprParser,
   fpsStrings, fpsStreams, fpsClasses, fpsImages;
 
 const
@@ -370,7 +370,7 @@ end;
 {                           TsSpreadOOXMLReader                                }
 {------------------------------------------------------------------------------}
 
-constructor TsSpreadOOXMLReader.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadOOXMLReader.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
   FDateMode := XlsxSettings.DateMode;
@@ -445,16 +445,19 @@ begin
   if Assigned(ACell) then begin
     i := FCellFormatList.FindIndexOfID(XFIndex);
     fmt := FCellFormatList.Items[i];
-    ACell^.FormatIndex := FWorkbook.AddCellFormat(fmt^);
+    ACell^.FormatIndex := (FWorkbook as TsWorkbook).AddCellFormat(fmt^);
   end;
 end;
 
-procedure TsSpreadOOXMLReader.ApplyHyperlinks(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLReader.ApplyHyperlinks(AWorksheet: TsbasicWorksheet);
 var
   i: Integer;
   hyperlinkData: THyperlinkListData;
   r1, c1, r2, c2, r, c: Cardinal;
+  sheet: TsWorksheet;
 begin
+  sheet := AWorksheet as TsWorksheet;
+
   for i:=0 to FHyperlinkList.Count-1 do
   begin
     hyperlinkData := THyperlinkListData(FHyperlinkList.Items[i]);
@@ -470,12 +473,12 @@ begin
       for c := c1 to c2 do
         with hyperlinkData do
           if Target = '' then
-            AWorksheet.WriteHyperlink(r, c, '#'+TextMark, ToolTip)
+            sheet.WriteHyperlink(r, c, '#'+TextMark, ToolTip)
           else
           if TextMark = '' then
-            AWorksheet.WriteHyperlink(r, c, Target, ToolTip)
+            sheet.WriteHyperlink(r, c, Target, ToolTip)
           else
-            AWorksheet.WriteHyperlink(r, c, Target+'#'+TextMark, ToolTip);
+            sheet.WriteHyperlink(r, c, Target+'#'+TextMark, ToolTip);
   end;
 end;
 
@@ -625,8 +628,11 @@ begin
   end;
 end;
 
-procedure TsSpreadOOXMLReader.ReadCell(ANode: TDOMNode; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLReader.ReadCell(ANode: TDOMNode;
+  AWorksheet: TsBasicWorksheet);
 var
+  book: TsWorkbook;
+  sheet: TsWorksheet;
   addr, s: String;
   rowIndex, colIndex: Cardinal;
   cell: PCell;
@@ -646,6 +652,9 @@ begin
   if ANode = nil then
     exit;
 
+  book := FWorkbook as TsWorkbook;
+  sheet := AWorksheet as TsWorksheet;
+
   // get row and column address
   addr := GetAttrValue(ANode, 'r');       // cell address, like 'A1'
   ParseCellString(addr, rowIndex, colIndex);
@@ -656,13 +665,13 @@ begin
     InitCell(FWorksheet, rowIndex, colIndex, FVirtualCell);
     cell := @FVirtualCell;
   end else
-    cell := AWorksheet.AddCell(rowIndex, colIndex);
+    cell := sheet.AddCell(rowIndex, colIndex);
 
   // get style index
   s := GetAttrValue(ANode, 's');
   if s <> '' then begin
     ApplyCellFormatting(cell, StrToInt(s));
-    fmt := Workbook.GetCellFormat(cell^.FormatIndex);
+    fmt := book.GetCellFormat(cell^.FormatIndex);
   end else
   begin
     InitFormatRecord(fmt);
@@ -670,7 +679,7 @@ begin
   end;
 
   // get number format parameters
-  numFmt := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+  numFmt := book.GetNumberFormat(fmt.NumberFormatIndex);
 
   // get data
   datanode := ANode.FirstChild;
@@ -692,7 +701,7 @@ begin
         tnode := tnode.NextSibling;
       end;
     end else
-    if (boReadFormulas in FWorkbook.Options) and (nodeName = 'f') then
+    if (boReadFormulas in book.Options) and (nodeName = 'f') then
     begin
       // Formula to cell
       formulaStr := GetNodeValue(datanode);
@@ -704,11 +713,11 @@ begin
           s := GetAttrValue(datanode, 'ref');
           if (s <> '') then      // This defines the shared formula range
           begin
-            AWorksheet.WriteFormula(cell, formulaStr);
+            sheet.WriteFormula(cell, formulaStr);
             // We store the shared formula base in the SharedFormulaBaseList.
             // The list index is identical with the 'si' attribute of the node.
             sharedformulabase := TSharedFormulaData.Create;
-            sharedformulabase.Worksheet := FWorksheet;
+            sharedformulabase.Worksheet := sheet;
             sharedformulabase.Row := rowindex;
             sharedformulabase.Col := colindex;
             sharedformulabase.Formula := formulaStr;
@@ -724,7 +733,7 @@ begin
               InitCell(FWorksheet, sharedformulabase.Row, sharedformulabase.Col, lCell);
               lCell.Formulavalue := sharedformulabase.Formula;
               lCell.Worksheet := sharedformulabase.Worksheet;
-              FWorksheet.CopyFormula(@lCell, cell);
+              sheet.CopyFormula(@lCell, cell);
               cell^.ContentType := cctFormula;
             end;
           end;
@@ -752,7 +761,7 @@ begin
   if (s = '') and (dataStr = '') then
   begin
     formulaStr := cell^.FormulaValue;
-    AWorksheet.WriteBlank(cell);     // this erases the formula!!!
+    sheet.WriteBlank(cell);     // this erases the formula!!!
     cell^.FormulaValue := formulaStr;
   end else
   if (s = '') or (s = 'n') then begin
@@ -762,18 +771,18 @@ begin
     begin
       if not IsTimeIntervalFormat(numFmt) then   // no correction of time origin for "time interval" format
         number := ConvertExcelDateTimeToDateTime(number, FDateMode);
-      AWorksheet.WriteDateTime(cell, number);
+      sheet.WriteDateTime(cell, number);
     end
     else if IsTextFormat(numFmt) then
-      AWorksheet.WriteText(cell, dataStr)
+      sheet.WriteText(cell, dataStr)
     else
-      AWorksheet.WriteNumber(cell, number);
+      sheet.WriteNumber(cell, number);
   end
   else
   if s = 's' then begin
     // String from shared strings table
     sstIndex := StrToInt(dataStr);
-    AWorksheet.WriteText(cell, FSharedStrings[sstIndex]);
+    sheet.WriteText(cell, FSharedStrings[sstIndex]);
     // Read rich-text parameters from the stream stored in the Objects of the stringlist
     if FSharedStrings.Objects[sstIndex] <> nil then
     begin
@@ -787,40 +796,40 @@ begin
   if (s = 'str') or (s = 'inlineStr') then begin
     // literal string
     formulaStr := cell^.FormulaValue;
-    AWorksheet.WriteText(cell, datastr);
+    sheet.WriteText(cell, datastr);
     cell^.FormulaValue := formulaStr;
   end else
   if s = 'b' then
     // boolean
-    AWorksheet.WriteBoolValue(cell, dataStr='1')
+    sheet.WriteBoolValue(cell, dataStr='1')
   else
   if s = 'e' then begin
     // error value
     if dataStr = '#NULL!' then
-      AWorksheet.WriteErrorValue(cell, errEmptyIntersection)
+      sheet.WriteErrorValue(cell, errEmptyIntersection)
     else if dataStr = '#DIV/0!' then
-      AWorksheet.WriteErrorValue(cell, errDivideByZero)
+      sheet.WriteErrorValue(cell, errDivideByZero)
     else if dataStr = '#VALUE!' then
-      AWorksheet.WriteErrorValue(cell, errWrongType)
+      sheet.WriteErrorValue(cell, errWrongType)
     else if dataStr = '#REF!' then
-      AWorksheet.WriteErrorValue(cell, errIllegalRef)
+      sheet.WriteErrorValue(cell, errIllegalRef)
     else if dataStr = '#NAME?' then
-      AWorksheet.WriteErrorValue(cell, errWrongName)
+      sheet.WriteErrorValue(cell, errWrongName)
     else if dataStr = '#NUM!' then
-      AWorksheet.WriteErrorValue(cell, errOverflow)
+      sheet.WriteErrorValue(cell, errOverflow)
     else if dataStr = '#N/A' then
-      AWorksheet.WriteErrorValue(cell, errArgError)
+      sheet.WriteErrorValue(cell, errArgError)
     else if dataStr = '' then
       // rare case...
       // see http://forum.lazarus.freepascal.org/index.php/topic,38726.0.html
-      AWorksheet.WriteBlank(cell)
+      sheet.WriteBlank(cell)
     else
       raise EFPSpreadsheetReader.Create(rsUnknownErrorType);
   end else
     raise EFPSpreadsheetReader.Create(rsUnknownDataType);
 
   if FIsVirtualMode then
-    Workbook.OnReadCellData(Workbook, rowIndex, colIndex, cell);
+    book.OnReadCellData(book, rowIndex, colIndex, cell);
 end;
 
 procedure TsSpreadOOXMLReader.ReadCellXfs(ANode: TDOMNode);
@@ -838,7 +847,10 @@ var
   borderData: TBorderListData;
   fnt: TsFont;
   cp: TsCellProtections;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   node := ANode.FirstChild;
   while Assigned(node) do
   begin
@@ -861,8 +873,8 @@ begin
           numFmtParams := nil
         else
         begin
-          fmt.NumberFormatIndex := Workbook.AddNumberFormat(numFmtStr);
-          numFmtParams := Workbook.GetNumberFormat(fmt.NumberFormatIndex);
+          fmt.NumberFormatIndex := book.AddNumberFormat(numFmtStr);
+          numFmtParams := book.GetNumberFormat(fmt.NumberFormatIndex);
         end;
         if numFmtParams <> nil then
         begin
@@ -882,9 +894,9 @@ begin
       if (s1 <> '') and (s2 <> '0') then
       begin
         fnt := TsFont(FFontList.Items[StrToInt(s1)]);
-        fmt.FontIndex := Workbook.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+        fmt.FontIndex := book.FindFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
         if fmt.FontIndex = -1 then
-          fmt.FontIndex := Workbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+          fmt.FontIndex := book.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
         if fmt.FontIndex > 0 then
           Include(fmt.UsedFormattingFields, uffFont);
       end;
@@ -1089,7 +1101,8 @@ begin
   Result := scBlack;
 end;
 
-procedure TsSpreadOOXMLReader.ReadCols(ANode: TDOMNode; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLReader.ReadCols(ANode: TDOMNode;
+  AWorksheet: TsBasicWorksheet);
 const
   EPS = 1e-3;
 var
@@ -1101,10 +1114,15 @@ var
   nodeName: String;
   idx: Integer;
   fmt: PsCellFormat;
+  book: TsWorkbook;
+  sheet: TsWorksheet;
 begin
   if ANode = nil then
     exit;
 
+  book := FWorkbook as TsWorkbook;
+  sheet := AWorksheet as TsWorksheet;
+
   colNode := ANode.FirstChild;
   while Assigned(colNode) do begin
     nodeName := colNode.NodeName;
@@ -1121,35 +1139,35 @@ begin
         s := GetAttrValue(colNode, 'width');
         if (s <> '') and TryStrToFloat(s, w, FPointSeparatorSettings) then
         begin
-          if SameValue(w, AWorksheet.ReadDefaultColWidth(suChars), EPS) then  // is this needed?
+          if SameValue(w, sheet.ReadDefaultColWidth(suChars), EPS) then  // is this needed?
             lCol.ColWidthType := cwtDefault
           else
             lCol.ColWidthType := cwtCustom;
-          lCol.Width := FWorkbook.ConvertUnits(w, suChars, FWorkbook.Units);
+          lCol.Width := book.ConvertUnits(w, suChars, book.Units);
         end;
       end else begin
         lCol.ColWidthType := cwtDefault;
-        lCol.Width := AWorksheet.ReadDefaultColWidth(FWorkbook.Units);
+        lCol.Width := sheet.ReadDefaultColWidth(FWorkbook.Units);
       end;
 
       s := GetAttrValue(colNode, 'style');
       if s <> '' then begin
         idx := FCellFormatList.FindIndexOfID(StrToInt(s));
         fmt := FCellFormatList.Items[idx];
-        lCol.FormatIndex := FWorkbook.AddCellFormat(fmt^);
+        lCol.FormatIndex := book.AddCellFormat(fmt^);
       end else
         lCol.FormatIndex := 0;
 
       if (lCol.ColWidthType = cwtCustom) or (lCol.FormatIndex > 0) then
         for col := col1 to Min(col2, FLastCol) do
-          AWorksheet.WriteColInfo(col, lCol);
+          sheet.WriteColInfo(col, lCol);
     end;
     colNode := colNode.NextSibling;
   end;
 end;
 
 procedure TsSpreadOOXMLReader.ReadComments(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   node, txtNode, rNode, rchild: TDOMNode;
   nodeName: String;
@@ -1188,7 +1206,7 @@ begin
         if (comment <> '') and ParseCellString(cellAddr, r, c) then begin
           // Fix line endings  // #10 --> "LineEnding"
           comment := UTF8StringReplace(comment, #10, LineEnding, [rfReplaceAll]);
-          AWorksheet.WriteComment(r, c, comment);
+          (AWorksheet as TsWorksheet).WriteComment(r, c, comment);
         end;
         txtNode := txtNode.NextSibling;
       end;
@@ -1234,7 +1252,7 @@ begin
         Continue;
       end;
       namestr := GetAttrValue(node, 'name');
-      sheet := FWorkbook.GetWorksheetByIndex(id);
+      sheet := (FWorkbook as TsWorkbook).GetWorksheetByIndex(id);
       if namestr = '_xlnm.Print_Area' then
       begin
         L := TStringList.Create;
@@ -1297,7 +1315,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadDimension(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   ref: String;
   r1, c1: Cardinal;
@@ -1432,7 +1450,7 @@ var
 begin
   isDefaultFont := FFontList.Count = 0;
 
-  fnt := Workbook.GetDefaultFont;
+  fnt := (Workbook as TsWorkbook).GetDefaultFont;
   if fnt <> nil then
   begin
     fntName := fnt.FontName;
@@ -1538,7 +1556,7 @@ begin
   Result := FFontList.Add(fnt);
 
   if isDefaultFont then
-    Workbook.SetDefaultFont(fnt.FontName, fnt.Size);
+    (Workbook as TsWorkbook).SetDefaultFont(fnt.FontName, fnt.Size);
 end;
 
 procedure TsSpreadOOXMLReader.ReadFonts(ANode: TDOMNode);
@@ -1553,11 +1571,12 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadHeaderFooter(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   node: TDOMNode;
   nodeName: String;
   s: String;
+  sheet: TsWorksheet absolute AWorksheet;
 
   function FixLineEnding(AString: String): String;
   begin
@@ -1570,23 +1589,23 @@ begin
 
   s := GetAttrValue(ANode, 'differentOddEven');
   if s = '1' then
-    with AWorksheet.PageLayout do Options := Options + [poDifferentOddEven];
+    with sheet.PageLayout do Options := Options + [poDifferentOddEven];
 
   s := GetAttrValue(ANode, 'differentFirst');
   if s = '1' then
-    with AWorksheet.PageLayout do Options := Options + [poDifferentFirst];
+    with sheet.PageLayout do Options := Options + [poDifferentFirst];
 
   node := ANode.FirstChild;
   while node <> nil do
   begin
     nodeName := node.NodeName;
     case nodeName of
-      'firstHeader': AWorksheet.PageLayout.Headers[0] := FixLineEnding(GetNodeValue(node));
-      'oddHeader'  : AWorksheet.PageLayout.Headers[1] := FixLineEnding(GetNodeValue(node));
-      'evenHeader' : AWorksheet.PageLayout.Headers[2] := FixLineEnding(GetNodeValue(node));
-      'firstFooter': AWorksheet.PageLayout.Footers[0] := FixLineEnding(GetNodeValue(node));
-      'oddFooter'  : AWorksheet.PageLayout.Footers[1] := FixLineEnding(GetNodeValue(node));
-      'evenFooter' : AWorksheet.PageLayout.Footers[2] := FixLineEnding(GetNodeValue(node));
+      'firstHeader': sheet.PageLayout.Headers[0] := FixLineEnding(GetNodeValue(node));
+      'oddHeader'  : sheet.PageLayout.Headers[1] := FixLineEnding(GetNodeValue(node));
+      'evenHeader' : sheet.PageLayout.Headers[2] := FixLineEnding(GetNodeValue(node));
+      'firstFooter': sheet.PageLayout.Footers[0] := FixLineEnding(GetNodeValue(node));
+      'oddFooter'  : sheet.PageLayout.Footers[1] := FixLineEnding(GetNodeValue(node));
+      'evenFooter' : sheet.PageLayout.Footers[2] := FixLineEnding(GetNodeValue(node));
     end;
     node := node.NextSibling;
   end;
@@ -1668,7 +1687,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadMergedCells(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   node: TDOMNode;
   nodename: String;
@@ -1682,7 +1701,7 @@ begin
       if nodename = 'mergeCell' then begin
         s := GetAttrValue(node, 'ref');
         if s <> '' then
-          AWorksheet.MergeCells(s);
+          (AWorksheet as TsWorksheet).MergeCells(s);
       end;
       node := node.NextSibling;
     end;
@@ -1718,43 +1737,45 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadPageMargins(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   if (ANode = nil) or (AWorksheet = nil) then     // just to make sure...
     exit;
 
   s := GetAttrValue(ANode, 'left');
   if s <> '' then
-    AWorksheet.PageLayout.LeftMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
+    sheet.PageLayout.LeftMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
 
   s := GetAttrValue(ANode, 'right');
   if s <> '' then
-    AWorksheet.PageLayout.RightMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
+    sheet.PageLayout.RightMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
 
   s := GetAttrValue(ANode, 'top');
   if s <> '' then
-    AWorksheet.PageLayout.TopMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
+    sheet.PageLayout.TopMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
 
   s := GetAttrValue(ANode, 'bottom');
   if s <> '' then
-    AWorksheet.PageLayout.BottomMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
+    sheet.PageLayout.BottomMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
 
   s := GetAttrValue(ANode, 'header');
   if s <> '' then
-    AWorksheet.PageLayout.HeaderMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
+    sheet.PageLayout.HeaderMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
 
   s := GetAttrValue(ANode, 'footer');
   if s <> '' then
-    AWorksheet.PageLayout.FooterMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
+    sheet.PageLayout.FooterMargin := PtsToMM(HtmlLengthStrToPts(s, 'in'));
 end;
 
 procedure TsSpreadOOXMLReader.ReadPageSetup(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
   n: Integer;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   if ANode = nil then
     exit;
@@ -1766,42 +1787,42 @@ begin
     n := StrToInt(s);
     if (n >= 0) and (n <= High(PAPER_SIZES)) then
     begin
-      AWorksheet.PageLayout.PageWidth := PAPER_SIZES[n, 0];
-      AWorksheet.PageLayout.PageHeight := PAPER_SIZES[n, 1];
+      sheet.PageLayout.PageWidth := PAPER_SIZES[n, 0];
+      sheet.PageLayout.PageHeight := PAPER_SIZES[n, 1];
     end;
   end;
 
   // Orientation
   s := GetAttrValue(ANode, 'orientation');
   if s = 'portrait' then
-    AWorksheet.PageLayout.Orientation := spoPortrait
+    sheet.PageLayout.Orientation := spoPortrait
   else if s = 'landscape' then
-    AWorksheet.PageLayout.Orientation := spoLandscape;
+    sheet.PageLayout.Orientation := spoLandscape;
 
   // Scaling factor
   s := GetAttrValue(ANode, 'scale');
   if s <> '' then
-    AWorksheet.PageLayout.ScalingFactor := StrToInt(s);
+    sheet.PageLayout.ScalingFactor := StrToInt(s);
     // poFitPages is automatically excluded
 
   // Fit print job to pages
   s := GetAttrValue(ANode, 'fitToHeight');
   if s <> '' then
-    AWorksheet.PageLayout.FitHeightToPages := StrToInt(s);
+    sheet.PageLayout.FitHeightToPages := StrToInt(s);
     // poFitPages is automatically included.
 
   s := GetAttrValue(ANode, 'fitToWidth');
   if s <> '' then
-    AWorksheet.PageLayout.FitWidthToPages := StrToInt(s);
+    sheet.PageLayout.FitWidthToPages := StrToInt(s);
     // poFitPages is automatially included.
 
   // First page number
   s := GetAttrValue(ANode, 'firstPageNumber');
   if s <> '' then
-    AWorksheet.PageLayout.StartPageNumber := StrToInt(s);
+    sheet.PageLayout.StartPageNumber := StrToInt(s);
 
   s := GetAttrValue(ANode, 'useFirstPageNumber');
-  with AWorksheet.PageLayout do
+  with sheet.PageLayout do
     if s = '1' then
       Options := Options + [poUseStartPageNumber]
     else
@@ -1810,17 +1831,17 @@ begin
   // Print order
   s := GetAttrValue(ANode, 'pageOrder');
   if s = 'overThenDown' then
-    with AWorksheet.PageLayout do Options := Options + [poPrintPagesByRows];
+    with sheet.PageLayout do Options := Options + [poPrintPagesByRows];
 
   // Monochrome
   s := GetAttrValue(ANode, 'blackAndWhite');
   if s = '1' then
-    with AWorksheet.PageLayout do Options := Options + [poMonochrome];
+    with sheet.PageLayout do Options := Options + [poMonochrome];
 
   // Quality
   s := GetAttrValue(ANode, 'draft');
   if s = '1' then
-    with AWorksheet.PageLayout do Options := Options + [poDraftQuality];
+    with sheet.PageLayout do Options := Options + [poDraftQuality];
 end;
 
 procedure TsSpreadOOXMLReader.ReadPalette(ANode: TDOMNode);
@@ -1874,22 +1895,24 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadPrintOptions(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   if ANode = nil then
     exit;
   s := GetAttrValue(ANode, 'headings');
   if (s = '1') then
-    with AWorksheet.PageLayout do Options := Options + [poPrintHeaders];
+    with sheet.PageLayout do Options := Options + [poPrintHeaders];
 
   s := GetAttrValue(ANode, 'gridLines');
   if (s = '1') then
-    with AWorksheet.PageLayout do Options := Options + [poPrintGridLines];
+    with sheet.PageLayout do Options := Options + [poPrintGridLines];
 end;
 
-procedure TsSpreadOOXMLReader.ReadRow(ANode: TDOMNode; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLReader.ReadRow(ANode: TDOMNode;
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
   r: Cardinal;
@@ -1911,10 +1934,10 @@ begin
     it is the default row height }
   s := GetAttrValue(ANode, 'ht');
   if s = '' then begin
-    lRow.Height := AWorksheet.ReadDefaultRowHeight(FWorkbook.Units);
+    lRow.Height := (AWorksheet as TsWorksheet).ReadDefaultRowHeight(FWorkbook.Units);
     lRow.RowHeightType := rhtDefault;
   end else
-    lRow.Height := FWorkbook.ConvertUnits(
+    lRow.Height := (FWorkbook as TsWorkbook).ConvertUnits(
       StrToFloat(s, FPointSeparatorSettings),
       suPoints,
       FWorkbook.Units
@@ -1932,13 +1955,13 @@ begin
     if s <> '' then begin
       idx := FCellFormatList.FindIndexOfID(StrToInt(s));
       fmt := FCellFormatList.Items[idx];
-      lRow.FormatIndex := FWorkbook.AddCellFormat(fmt^);
+      lRow.FormatIndex := (FWorkbook as TsWorkbook).AddCellFormat(fmt^);
     end;
   end;
 
   { Write out }
   if (lRow.RowHeightType <> rhtDefault) or (lRow.FormatIndex <> 0) then
-    AWorksheet.WriteRowInfo(r, lRow);
+    (AWorksheet as TsWorksheet).WriteRowInfo(r, lRow);
 end;
 
 procedure TsSpreadOOXMLReader.ReadSharedStrings(ANode: TDOMNode);
@@ -1980,9 +2003,13 @@ begin
               // But this fontindex may be different from the one needed for the
               // workbook's font list. We fix this here.
               fnt := TsFont(FFontList[fntIndex]);
-              fntIndex := Workbook.FindFont(fnt.FontName, fnt.Size, fnt.style, fnt.Color, fnt.Position);
+              fntIndex := (Workbook as TsWorkbook).FindFont(
+                fnt.FontName, fnt.Size, fnt.style, fnt.Color, fnt.Position
+              );
               if fntIndex = -1 then
-                fntIndex := Workbook.AddFont(fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position);
+                fntIndex := (Workbook as TsWorkbook).AddFont(
+                  fnt.FontName, fnt.Size, fnt.Style, fnt.Color, fnt.Position
+                );
               SetLength(rtParams, Length(rtParams)+1);
               rtParams[High(rtParams)].FirstIndex := UTF8Length(totaltxt) + 1;
               rtParams[High(rtParams)].FontIndex := fntIndex;
@@ -2008,7 +2035,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadSheetFormatPr(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   w, h: Double;
   s: String;
@@ -2018,11 +2045,11 @@ begin
 
   s := GetAttrValue(ANode, 'defaultColWidth');   // is in characters
   if (s <> '') and TryStrToFloat(s, w, FPointSeparatorSettings) then
-    AWorksheet.WriteDefaultColWidth(w, suChars);
+    (AWorksheet as TsWorksheet).WriteDefaultColWidth(w, suChars);
 
   s := GetAttrValue(ANode, 'defaultRowHeight');  // is in points
   if (s <> '') and TryStrToFloat(s, h, FPointSeparatorSettings) then
-    AWorksheet.WriteDefaultRowHeight(h, suPoints);
+    (AWorksheet as TsWorksheet).WriteDefaultRowHeight(h, suPoints);
 end;
 
 procedure TsSpreadOOXMLReader.ReadSheetList(ANode: TDOMNode);
@@ -2047,7 +2074,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLReader.ReadSheetProtection(ANode: TDOMNode;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
   shc: TsCryptoInfo;
@@ -2079,7 +2106,7 @@ begin
       shc.SpinCount := StrToIntDef(s, 0);
     end;
   end;
-  AWorksheet.CryptoInfo := shc;
+  (AWorksheet as TsWorksheet).CryptoInfo := shc;
 
   shp := DEFAULT_SHEET_PROTECTION;
 
@@ -2157,17 +2184,21 @@ begin
     if (s = '') or (s = '1') then Include(shp, spPivotTables);
   }
 
-  AWorksheet.Protection := shp;
-  AWorksheet.Protect(true);
+  with AWorksheet as TsWorksheet do begin
+    Protection := shp;
+    Protect(true);
+  end;
 end;
 
-procedure TsSpreadOOXMLReader.ReadSheetViews(ANode: TDOMNode; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLReader.ReadSheetViews(ANode: TDOMNode;
+  AWorksheet: TsBasicWorksheet);
 var
   sheetViewNode: TDOMNode;
   childNode: TDOMNode;
   nodeName: String;
   s: String;
   actRow, actCol: Cardinal;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   if ANode = nil then
     exit;
@@ -2178,29 +2209,29 @@ begin
     if nodeName = 'sheetView' then begin
       s := GetAttrValue(sheetViewNode, 'showGridLines');
       if s = '0' then
-        AWorksheet.Options := AWorksheet.Options - [soShowGridLines];
+        sheet.Options := AWorksheet.Options - [soShowGridLines];
 
       s := GetAttrValue(sheetViewNode, 'showRowColHeaders');
       if s = '0' then
-         AWorksheet.Options := AWorksheet.Options - [soShowHeaders];
+         sheet.Options := AWorksheet.Options - [soShowHeaders];
 
       s := GetAttrValue(sheetViewNode, 'tabSelected');
       if s = '1' then
-        Workbook.ActiveWorksheet := AWorksheet;
+        (FWorkbook as TsWorkbook).ActiveWorksheet := sheet;
 
       s := GetAttrValue(sheetViewNode, 'windowProtection');
       if s = '1' then
-        AWorksheet.Options := AWorksheet.Options + [soPanesProtection];
+        sheet.Options := sheet.Options + [soPanesProtection];
 
       s := GetAttrValue(sheetViewNode, 'zoomScale');
       if s <> '' then
-        AWorksheet.ZoomFactor := StrToFloat(s, FPointSeparatorSettings) * 0.01;
+        sheet.ZoomFactor := StrToFloat(s, FPointSeparatorSettings) * 0.01;
 
       s := GetAttrValue(sheetViewNode, 'rightToLeft');
       if s = '0' then
-        AWorksheet.BiDiMode := bdLTR
+        sheet.BiDiMode := bdLTR
       else if s = '1' then
-        AWorksheet.BiDiMode := bdRTL;
+        sheet.BiDiMode := bdRTL;
 
       childNode := sheetViewNode.FirstChild;
       while Assigned(childNode) do begin
@@ -2208,11 +2239,13 @@ begin
         if nodeName = 'pane' then begin
           s := GetAttrValue(childNode, 'state');
           if s = 'frozen' then begin
-            AWorksheet.Options := AWorksheet.Options + [soHasFrozenPanes];
+            sheet.Options := sheet.Options + [soHasFrozenPanes];
             s := GetAttrValue(childNode, 'xSplit');
-            if s <> '' then AWorksheet.LeftPaneWidth := round(StrToFloat(s, FPointSeparatorSettings));
+            if s <> '' then
+              sheet.LeftPaneWidth := round(StrToFloat(s, FPointSeparatorSettings));
             s := GetAttrValue(childNode, 'ySplit');
-            if s <> '' then AWorksheet.TopPaneHeight := round(StrToFloat(s, FPointSeparatorSettings));
+            if s <> '' then
+              sheet.TopPaneHeight := round(StrToFloat(s, FPointSeparatorSettings));
           end;
         end else
         if nodeName = 'selection' then begin
@@ -2220,7 +2253,7 @@ begin
           if s <> '' then
           begin
             ParseCellString(s, actRow, actCol);
-            AWorksheet.SelectCell(actRow, actCol);
+            sheet.SelectCell(actRow, actCol);
           end;
         end;
         childNode := childNode.NextSibling;
@@ -2338,7 +2371,7 @@ begin
       wbc.SpinCount := StrToIntDef(GetAttrValue(ANode, 'workbookSpinCount'), 0);
     end;
   end;
-  Workbook.CryptoInfo := wbc;
+  (Workbook as TsWorkbook).CryptoInfo := wbc;
 
   {
   InitCryptoInfo(wbc);
@@ -2372,7 +2405,8 @@ begin
   Workbook.Protection := wbp;
 end;
 
-procedure TsSpreadOOXMLReader.ReadWorksheet(ANode: TDOMNode; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLReader.ReadWorksheet(ANode: TDOMNode;
+  AWorksheet: TsBasicWorksheet);
 var
   rownode: TDOMNode;
   cellnode: TDOMNode;
@@ -2487,7 +2521,7 @@ begin
     // read worksheets
     for i:=0 to FSheetList.Count-1 do begin
       // Create worksheet
-      FWorksheet := FWorkbook.AddWorksheet(TSheetData(FSheetList[i]).Name, true);
+      FWorksheet := (FWorkbook as TsWorkbook).AddWorksheet(TSheetData(FSheetList[i]).Name, true);
       if TSheetData(FSheetList[i]).Hidden then
         FWorksheet.Options := FWorksheet.Options + [soHidden];
 
@@ -2575,7 +2609,7 @@ begin
 
       // Active worksheet
       if i = actSheetIndex then
-        FWorkbook.SelectWorksheet(FWorksheet);
+        (FWorkbook as TsWorkbook).SelectWorksheet(FWorksheet as TsWorksheet);
     end;  // for
 
     // 2nd run for the workbook.xml file
@@ -2607,7 +2641,7 @@ end;
   Defines the date mode and the limitations of the file format.
   Initializes the format settings to be used when writing to xml.
 -------------------------------------------------------------------------------}
-constructor TsSpreadOOXMLWriter.Create(AWorkbook: TsWorkbook);
+constructor TsSpreadOOXMLWriter.Create(AWorkbook: TsBasicWorkbook);
 begin
   inherited Create(AWorkbook);
 
@@ -2686,11 +2720,14 @@ end;
 
 { Calculates the rIds for comments, hyperlinks, image, and
   header/footer images of the specified worksheet }
-procedure TsSpreadOOXMLWriter.Get_rId(AWorksheet: TsWorksheet;
+procedure TsSpreadOOXMLWriter.Get_rId(AWorksheet: TsBasicWorksheet;
   out AComment_rId, AFirstHyperlink_rId, ADrawing_rId, ADrawingHF_rId: Integer);
 var
   next_rId: Integer;
+  sheet: TsWorksheet;
 begin
+  sheet := AWorksheet as TsWorksheet;
+
   AComment_rId := -1;
   AFirstHyperlink_rId := -1;
   ADrawing_rId := -1;
@@ -2698,21 +2735,21 @@ begin
   next_rId := 1;
 
   // Comments first
-  if AWorksheet.Comments.Count > 0 then
+  if sheet.Comments.Count > 0 then
   begin
     AComment_rId := next_rId;
     inc(next_rId, 2);  // there are two .rels entries in case of comments
   end;
 
   // Embedded images next
-  if AWorksheet.GetImageCount > 0 then
+  if sheet.GetImageCount > 0 then
   begin
     ADrawing_rId := next_rId;
     inc(next_rId);
   end;
 
   // HeaderFooter images next
-  if AWorksheet.PageLayout.HasHeaderFooterImages then
+  if sheet.PageLayout.HasHeaderFooterImages then
   begin
     ADrawingHF_rId := next_rId;
     inc(next_rId);
@@ -2720,14 +2757,17 @@ begin
 
   // Hyperlinks at the end because it is not clear how many rIds will be
   // used without analyzing the hyperlink.
-  if AWorksheet.Hyperlinks.Count > 0 then
+  if sheet.Hyperlinks.Count > 0 then
     AFirstHyperlink_rId := next_rId;
 end;
 
 function TsSpreadOOXMLWriter.GetActiveTab: String;
+var
+  book: TsWorkbook;
 begin
-  Result := IfThen(FWorkbook.ActiveWorksheet = nil, '',
-    ' activeTab="' + IntToStr(FWorkbook.GetWorksheetIndex(FWorkbook.ActiveWorksheet)) + '"');
+  book := FWorkbook as TsWorkbook;
+  Result := IfThen(book.ActiveWorksheet = nil, '',
+    ' activeTab="' + IntToStr(book.GetWorksheetIndex(book.ActiveWorksheet)) + '"');
 end;
 
 { Determines the formatting index which a given cell has in list of
@@ -2747,15 +2787,18 @@ var
   //styleCell: PCell;
   i, n : Integer;
   fmt: PsCellFormat;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   // first list entry is a no-border cell
   n := 1;
   SetLength(FBorderList, n);
   FBorderList[0] := nil;
 
-  for i := 0 to FWorkbook.GetNumCellFormats - 1 do
+  for i := 0 to book.GetNumCellFormats - 1 do
   begin
-    fmt := FWorkbook.GetPointerToCellFormat(i);
+    fmt := book.GetPointerToCellFormat(i);
     if FindBorderInList(fmt) = -1 then
     begin
       SetLength(FBorderList, n+1);
@@ -2774,16 +2817,19 @@ procedure TsSpreadOOXMLWriter.ListAllFills;
 var
   i, n: Integer;
   fmt: PsCellFormat;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   // Add built-in fills first.
   n := 2;
   SetLength(FFillList, n);
   FFillList[0] := nil;  // built-in "no fill"
   FFillList[1] := nil;  // built-in "gray125"
 
-  for i := 0 to FWorkbook.GetNumCellFormats - 1 do
+  for i := 0 to book.GetNumCellFormats - 1 do
   begin
-    fmt := FWorkbook.GetPointerToCellFormat(i);
+    fmt := book.GetPointerToCellFormat(i);
     if FindFillInList(fmt) = -1 then
     begin
       SetLength(FFillList, n+1);
@@ -2863,30 +2909,33 @@ begin
     '</borders>');
 end;
 
-procedure TsSpreadOOXMLWriter.WriteCols(AStream: TStream; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteCols(AStream: TStream;
+  AWorksheet: TsBasicWorksheet);
 var
   lCol: PCol;
   c: Integer;
   w: Single;
   customWidth: String;
   customStyle: String;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   AppendToStream(AStream,
     '<cols>');
 
-  for c:=0 to AWorksheet.GetLastColIndex do begin
+  for c:=0 to sheet.GetLastColIndex do begin
     customWidth := '';
     customStyle := '';
-    lCol := AWorksheet.FindCol(c);
+    lCol := sheet.FindCol(c);
 
     // The column width is needed in suChars here.
-    w := AWorksheet.ReadDefaultColWidth(suChars);
+    w := sheet.ReadDefaultColWidth(suChars);
     if lCol <> nil then begin
       if lCol^.ColWidthType = cwtCustom then begin
-        w := FWorkbook.ConvertUnits(lCol^.Width, FWorkbook.Units, suChars);
+        w := (FWorkbook as TsWorkbook).ConvertUnits(lCol^.Width, FWorkbook.Units, suChars);
         customWidth := 'customWidth="1" ';
       end;
-      if lCol^.FormatIndex > 0 then customStyle := Format('style="%d" ', [lCol^.FormatIndex]);
+      if lCol^.FormatIndex > 0 then
+        customStyle := Format('style="%d" ', [lCol^.FormatIndex]);
     end;
     AppendToStream(AStream, Format(
       '<col min="%d" max="%d" width="%.2f" %s%s />',
@@ -2898,12 +2947,12 @@ begin
     '</cols>');
 end;
 
-procedure TsSpreadOOXMLWriter.WriteComments(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteComments(AWorksheet: TsBasicWorksheet);
 var
   comment: PsComment;
   txt: String;
 begin
-  if AWorksheet.Comments.Count = 0 then
+  if (AWorksheet as TsWorksheet).Comments.Count = 0 then
     exit;
 
   // Create the comments stream
@@ -2923,7 +2972,7 @@ begin
       '<commentList>');
 
   // Comments
-  for comment in AWorksheet.Comments do
+  for comment in (AWorksheet as TsWorksheet).Comments do
   begin
     txt := comment^.Text;
     ValidXMLText(txt);
@@ -2953,7 +3002,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteDimension(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   r1,c1,r2,c2: Cardinal;
   dim: String;
@@ -3051,11 +3100,13 @@ procedure TsSpreadOOXMLWriter.WriteFontList(AStream: TStream);
 var
   i: Integer;
   font: TsFont;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
   AppendToStream(AStream, Format(
-    '<fonts count="%d">', [Workbook.GetFontCount]));
-  for i:=0 to Workbook.GetFontCount-1 do begin
-    font := Workbook.GetFont(i);
+    '<fonts count="%d">', [book.GetFontCount]));
+  for i:=0 to book.GetFontCount-1 do begin
+    font := book.GetFont(i);
     WriteFont(AStream, font, true);
   end;
   AppendToStream(AStream,
@@ -3063,11 +3114,11 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteHeaderFooter(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
 begin
-  with AWorksheet.PageLayout do
+  with (AWorksheet as TsWorksheet).PageLayout do
   begin
     if not (HasHeader or HasFooter) then
       exit;
@@ -3088,7 +3139,7 @@ begin
       AppendToStream(AStream,
           '<oddFooter>' + UTF8TextToXMLText(Footers[HEADER_FOOTER_INDEX_ODD]) + '</oddFooter>');
 
-    if poDifferentFirst in AWorksheet.PageLayout.Options then
+    if poDifferentFirst in (AWorksheet as TsWorksheet).PageLayout.Options then
     begin
       if Headers[HEADER_FOOTER_INDEX_FIRST] <> '' then
         AppendToStream(AStream,
@@ -3112,21 +3163,22 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteHyperlinks(AStream: TStream;
-  AWorksheet: TsWorksheet; rId: Integer);
+  AWorksheet: TsBasicWorksheet; rId: Integer);
 var
   hyperlink: PsHyperlink;
   target, bookmark: String;
   s: String;
   txt: String;
   AVLNode: TAvgLvlTreeNode;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  if AWorksheet.Hyperlinks.Count = 0 then
+  if sheet.Hyperlinks.Count = 0 then
     exit;
 
   AppendToStream(AStream,
     '<hyperlinks>');
 
-  AVLNode := AWorksheet.Hyperlinks.FindLowest;
+  AVLNode := sheet.Hyperlinks.FindLowest;
   while AVLNode <> nil do begin
     hyperlink := PsHyperlink(AVLNode.Data);
     SplitHyperlink(hyperlink^.Target, target, bookmark);
@@ -3138,7 +3190,7 @@ begin
     end;
     if bookmark <> '' then //target = '' then
       s := Format('%s location="%s"', [s, bookmark]);
-    txt := UTF8TextToXMLText(AWorksheet.ReadAsText(hyperlink^.Row, hyperlink^.Col));
+    txt := UTF8TextToXMLText(sheet.ReadAsText(hyperlink^.Row, hyperlink^.Col));
     if (txt <> '') and (txt <> hyperlink^.Target) then
       s := Format('%s display="%s"', [s, txt]);
     if hyperlink^.ToolTip <> '' then begin
@@ -3148,7 +3200,7 @@ begin
     end;
     AppendToStream(AStream,
         '<hyperlink ' + s + ' />');
-    AVLNode := AWorksheet.Hyperlinks.FindSuccessor(AVLNode);
+    AVLNode := sheet.Hyperlinks.FindSuccessor(AVLNode);
   end;
 
   AppendToStream(AStream,
@@ -3156,17 +3208,17 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteMergedCells(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   rng: PsCellRange;
   n: Integer;
 begin
-  n := AWorksheet.MergedCells.Count;
+  n := (AWorksheet as TsWorksheet).MergedCells.Count;
   if n = 0 then
     exit;
   AppendToStream(AStream, Format(
     '<mergeCells count="%d">', [n]) );
-  for rng in AWorksheet.MergedCells do
+  for rng in (AWorksheet as TsWorksheet).MergedCells do
     AppendToStream(AStream, Format(
       '<mergeCell ref="%s" />', [GetCellRangeString(rng^.Row1, rng^.Col1, rng^.Row2, rng^.Col2)]));
   AppendToStream(AStream,
@@ -3215,9 +3267,9 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WritePageMargins(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 begin
-  with AWorksheet.PageLayout do
+  with (AWorksheet as TsWorksheet).PageLayout do
     AppendToStream(AStream, Format(
       '<pageMargins left="%g" right="%g" top="%g" bottom="%g" header="%g" footer="%g" />', [
       mmToIn(LeftMargin), mmToIn(RightMargin), mmToIn(TopMargin), mmToIn(BottomMargin),
@@ -3227,55 +3279,56 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WritePageSetup(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
   i: Integer;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   s := '';
 
   // Paper size
   for i:=0 to High(PAPER_SIZES) do
-    if (SameValue(PAPER_SIZES[i,0], AWorksheet.PageLayout.PageHeight) and
-        SameValue(PAPER_SIZES[i,1], AWorksheet.PageLayout.PageWidth))
-    or (SameValue(PAPER_SIZES[i,1], AWorksheet.PageLayout.PageHeight) and
-        SameValue(PAPER_SIZES[i,0], AWorksheet.PageLayout.PageWidth))
+    if (SameValue(PAPER_SIZES[i,0], sheet.PageLayout.PageHeight) and
+        SameValue(PAPER_SIZES[i,1], sheet.PageLayout.PageWidth))
+    or (SameValue(PAPER_SIZES[i,1], sheet.PageLayout.PageHeight) and
+        SameValue(PAPER_SIZES[i,0], sheet.PageLayout.PageWidth))
     then begin
       s := Format('%s paperSize="%d"', [s, i]);
       break;
     end;
 
-  if poFitPages in AWorksheet.PageLayout.Options then
+  if poFitPages in sheet.PageLayout.Options then
   begin
     // Fit width to pages
-    s := Format('%s fitToWidth="%d"', [s, AWorksheet.PageLayout.FitWidthToPages]);
+    s := Format('%s fitToWidth="%d"', [s, sheet.PageLayout.FitWidthToPages]);
     // Fit height to pages
-    s := Format('%s fitToHeight="%d"', [s, AWorksheet.PageLayout.FitHeightToPages]);
+    s := Format('%s fitToHeight="%d"', [s, sheet.PageLayout.FitHeightToPages]);
   end else
     // Scaling factor
-    s := Format('%s scale="%d"', [s, AWorksheet.PageLayout.ScalingFactor]);
+    s := Format('%s scale="%d"', [s, sheet.PageLayout.ScalingFactor]);
 
   // Orientation
   s := Format('%s orientation="%s"', [
-    s, IfThen(AWorksheet.PageLayout.Orientation = spoPortrait, 'portrait', 'landscape')
+    s, IfThen(sheet.PageLayout.Orientation = spoPortrait, 'portrait', 'landscape')
   ]);
 
   // First page number
-  if poUseStartPageNumber in FWorksheet.PageLayout.Options then
+  if poUseStartPageNumber in sheet.PageLayout.Options then
     s := Format('%s useFirstPageNumber="1"', [s]);
 
-  s := Format('%s firstPageNumber="%d"', [s, AWorksheet.PageLayout.StartPageNumber]);
+  s := Format('%s firstPageNumber="%d"', [s, sheet.PageLayout.StartPageNumber]);
 
   // Print order
-  if poPrintPagesByRows in AWorksheet.PageLayout.Options then
+  if poPrintPagesByRows in sheet.PageLayout.Options then
     s := s + ' pageOrder="overThenDown"';
 
   // Monochrome
-  if poMonochrome in AWorksheet.PageLayout.Options then
+  if poMonochrome in sheet.PageLayout.Options then
     s := s + ' blackAndWhite="1"';
 
   // Quality
-  if poDraftQuality in AWOrksheet.PageLayout.Options then
+  if poDraftQuality in sheet.PageLayout.Options then
     s := s + ' draft="1"';
 
   if s <> '' then
@@ -3284,14 +3337,14 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WritePrintOptions(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
 begin
   s := '';
-  if poPrintGridLines in AWorksheet.PageLayout.Options then
+  if poPrintGridLines in (AWorksheet as TsWorksheet).PageLayout.Options then
     s := s + ' gridLines="1"';
-  if poPrintHeaders in AWorksheet.PageLayout.Options then
+  if poPrintHeaders in (AWorksheet as TsWorksheet).PageLayout.Options then
     s := s + ' headings="1"';
 
   if s <> '' then
@@ -3300,7 +3353,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteSheetData(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   r, r1, r2: Cardinal;
   c, c1, c2: Cardinal;
@@ -3310,36 +3363,42 @@ var
   styleCell: PCell;
   cell: PCell;
   s: String;
+  sheet: TsWorksheet;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+  sheet := AWorksheet as TsWorksheet;
+
   AppendToStream(AStream,
       '<sheetData>');
 
   GetSheetDimensions(AWorksheet, r1, r2, c1, c2);
 
   if (boVirtualMode in Workbook.Options) then begin
-    if Assigned(AWorksheet.OnWriteCellData) and
-      (AWorksheet.VirtualColCount > 0) and (AWorksheet.VirtualRowCount > 0)
+    if Assigned(sheet.OnWriteCellData) and
+      (sheet.VirtualColCount > 0) and (sheet.VirtualRowCount > 0)
     then begin
       for r := 0 to r2 do begin
-        row := AWorksheet.FindRow(r);
+        row := sheet.FindRow(r);
         s := '';
         if row <> nil then begin
           s := s + Format(' ht="%.2f"',
-            [FWorkbook.ConvertUnits(row^.Height, FWorkbook.Units, suPoints)],
-            FPointSeparatorSettings);
+            [book.ConvertUnits(row^.Height, book.Units, suPoints)],
+            FPointSeparatorSettings
+          );
           if row^.RowHeightType = rhtCustom then
             s := s + ' customHeight="1"';
           if row^.FormatIndex > 0 then
             s := s + Format(' s="%d" customFormat="1"', [row^.FormatIndex]);
         end;
         AppendToStream(AStream, Format(
-          '<row r="%d" spans="1:%d"%s>', [r+1, AWorksheet.VirtualColCount, s]));
+          '<row r="%d" spans="1:%d"%s>', [r+1, sheet.VirtualColCount, s]));
         for c := 0 to c2 do begin
           lCell.Row := r; // to silence a compiler hint
           InitCell(lCell);
           value := varNull;
           styleCell := nil;
-          AWorksheet.OnWriteCellData(AWorksheet, r, c, value, styleCell);
+          sheet.OnWriteCellData(sheet, r, c, value, styleCell);
           if styleCell <> nil then
             lCell := styleCell^;
           lCell.Row := r;
@@ -3385,12 +3444,13 @@ begin
     for r := r1 to r2 do begin
       // If the row has a custom or auto height and/or custom format
       // then add them to the <row> specification
-      row := AWorksheet.FindRow(r);
+      row := sheet.FindRow(r);
       s := '';
       if row <> nil then begin
         s := s + Format(' ht="%.2f"',
-          [FWorkbook.ConvertUnits(row^.Height, FWorkbook.Units, suPoints)],
-          FPointSeparatorSettings);
+          [book.ConvertUnits(row^.Height, book.Units, suPoints)],
+          FPointSeparatorSettings
+        );
         if row^.RowHeightType = rhtCustom then
           s := s + ' customHeight="1"';
         if row^.FormatIndex > 0 then
@@ -3406,7 +3466,7 @@ begin
         WriteCellToStream(AStream, cell);
       }
       for c := c1 to c2 do begin
-        cell := AWorksheet.FindCell(r, c);
+        cell := sheet.FindCell(r, c);
         if Assigned(cell) then
           WriteCellToStream(AStream, cell);
       end;
@@ -3420,26 +3480,27 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteSheetFormatPr(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   w, h: Single;
 begin
   // Excel has column width in characters, and row heights in pts.
-  w := AWorksheet.ReadDefaultColWidth(suChars);
-  h := AWorksheet.ReadDefaultRowHeight(suPoints);
+  w := (AWorksheet as TsWorksheet).ReadDefaultColWidth(suChars);
+  h := (AWorksheet as TsWorksheet).ReadDefaultRowHeight(suPoints);
   AppendToStream(AStream, Format(
     '<sheetFormatPr baseColWidth="10" defaultColWidth="%.2f" defaultRowHeight="%.2f" customHeight="true" />',
     [w, h],
     FPointSeparatorSettings));
 end;
 
-procedure TsSpreadOOXMLWriter.WriteSheetPr(AStream: TStream; AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteSheetPr(AStream: TStream;
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
 begin
   s := '';
-  if (AWorksheet.PageLayout.FitWidthToPages > 0) or
-     (AWorksheet.PageLayout.FitHeightToPages > 0) then
+  if ((AWorksheet as TsWorksheet).PageLayout.FitWidthToPages > 0) or
+     ((AWorksheet as TsWorksheet).PageLayout.FitHeightToPages > 0) then
   s := s + ' fitToPage="1"';
   if s <> '' then s := '<pageSetUpPr' + s + ' />';
 
@@ -3449,84 +3510,85 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteSheetProtection(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 var
   s: String;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   s := '';
 
   // No attribute -> attr="0"
-  if AWorksheet.IsProtected then
+  if sheet.IsProtected then
     s := ' sheet="1" scenarios="1"'
   else
     Exit; //exit if sheet not protected
 
-  if AWorksheet.CryptoInfo.PasswordHash <> '' then begin
-    if AWorksheet.CryptoInfo.Algorithm = caExcel then
-      s := s + ' password="' + AWorksheet.CryptoInfo.PasswordHash + '"'
+  if sheet.CryptoInfo.PasswordHash <> '' then begin
+    if sheet.CryptoInfo.Algorithm = caExcel then
+      s := s + ' password="' + sheet.CryptoInfo.PasswordHash + '"'
     else
     begin
-      s := s + ' hashValue="' + AWorksheet.CryptoInfo.PasswordHash + '"';
+      s := s + ' hashValue="' + sheet.CryptoInfo.PasswordHash + '"';
 
-      if AWorksheet.CryptoInfo.Algorithm <> caUnknown then
-        s := s + ' algorithmName="' + AlgorithmToStr(AWorksheet.CryptoInfo.Algorithm, auExcel) + '"';
+      if sheet.CryptoInfo.Algorithm <> caUnknown then
+        s := s + ' algorithmName="' + AlgorithmToStr(sheet.CryptoInfo.Algorithm, auExcel) + '"';
 
-      if AWorksheet.CryptoInfo.SaltValue <> '' then
-        s := s + ' saltValue="' + AWorksheet.CryptoInfo.SaltValue + '"';
+      if sheet.CryptoInfo.SaltValue <> '' then
+        s := s + ' saltValue="' + sheet.CryptoInfo.SaltValue + '"';
 
-      if AWorksheet.CryptoInfo.SpinCount <> 0 then
-        s := s + ' spinCount="' + IntToStr(AWorksheet.CryptoInfo.SpinCount) + '"';
+      if sheet.CryptoInfo.SpinCount <> 0 then
+        s := s + ' spinCount="' + IntToStr(sheet.CryptoInfo.SpinCount) + '"';
     end;
   end;
 
-  if spObjects in AWorksheet.Protection then
+  if spObjects in sheet.Protection then
     s := s + ' objects="1"';
 
   {
-  if spScenarios in AWorksheet.Protection then     // to do: Remove from default above
+  if spScenarios in sheet.Protection then     // to do: Remove from default above
     s := s + ' scenarios="1"';
   }
 
-  if spSelectLockedCells in AWorksheet.Protection then
+  if spSelectLockedCells in sheet.Protection then
     s := s + ' selectLockedCells="1"';
 
-  if spSelectUnlockedCells in AWorksheet.Protection then
+  if spSelectUnlockedCells in sheet.Protection then
     s := s + ' selectUnlockedCells="1"';
 
   // No attribute -> attr="1"
   {
-  if not (spAutoFilter in AWorksheet.Protection) then
+  if not (spAutoFilter in sheet.Protection) then
     s := s + ' autoFilter="0"';
   }
-  if not (spDeleteColumns in AWorksheet.Protection) then
+  if not (spDeleteColumns in sheet.Protection) then
     s := s + ' deleteColumns="0"';
 
-  if not (spDeleteRows in AWorksheet.Protection) then
+  if not (spDeleteRows in sheet.Protection) then
     s := s + ' deleteRows="0"';
 
-  if not (spFormatCells in AWorksheet.Protection) then
+  if not (spFormatCells in sheet.Protection) then
     s := s + ' formatCells="0"';
 
-  if not (spFormatColumns in AWorksheet.Protection) then
+  if not (spFormatColumns in sheet.Protection) then
     s := s + ' formatColumns="0"';
 
-  if not (spFormatRows in AWorksheet.Protection) then
+  if not (spFormatRows in sheet.Protection) then
     s := s + ' formatRows="0"';
 
-  if not (spInsertColumns in AWorksheet.Protection) then
+  if not (spInsertColumns in sheet.Protection) then
     s := s + ' insertColumns="0"';
 
-  if not (spInsertHyperlinks in AWorksheet.Protection) then
+  if not (spInsertHyperlinks in sheet.Protection) then
     s := s + ' insertHyperlinks="0"';
 
-  if not (spInsertRows in AWorksheet.Protection) then
+  if not (spInsertRows in sheet.Protection) then
     s := s + ' insertRows="0"';
 
   {
-  if not (spPivotTables in AWorksheet.Protection) then
+  if not (spPivotTables in sheet.Protection) then
     s := s + ' pivotTables="0"';
   }
-  if not (spSort in AWorksheet.Protection) then
+  if not (spSort in sheet.Protection) then
     s := s + ' sort="0"';
 
   if s <> '' then
@@ -3543,9 +3605,9 @@ var
 begin
   AppendToStream(AStream,
     '<sheets>');
-  for counter := 1 to Workbook.GetWorksheetCount do
+  for counter := 1 to (Workbook as TsWorkbook).GetWorksheetCount do
   begin
-    sheet := Workbook.GetWorksheetByIndex(counter-1);
+    sheet := (Workbook as TsWorkbook).GetWorksheetByIndex(counter-1);
     sheetname := UTF8TextToXMLText(sheet.Name);
     sheetState := IfThen(soHidden in sheet.Options, ' state="hidden"', '');
     AppendToStream(AStream, Format(
@@ -3557,7 +3619,7 @@ begin
 end;
 
 procedure TsSpreadOOXMLWriter.WriteSheetViews(AStream: TStream;
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
 const
   ZOOM_EPS = 1E-3;
 var
@@ -3572,37 +3634,41 @@ var
   zoomscale: String;
   attr: String;
   windowProtection: String;
+  book: TsWorkbook;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
+  book := FWorkbook as TsWorkbook;
+
   // Show gridlines ?
-  showGridLines := StrUtils.IfThen(soShowGridLines in AWorksheet.Options, '', ' showGridLines="0"');
+  showGridLines := StrUtils.IfThen(soShowGridLines in sheet.Options, '', ' showGridLines="0"');
 
   // Show headers?
-  showHeaders := StrUtils.IfThen(soShowHeaders in AWorksheet.Options, '', ' showRowColHeaders="0"');
+  showHeaders := StrUtils.IfThen(soShowHeaders in sheet.Options, '', ' showRowColHeaders="0"');
 
   // Zoom factor
   if boWriteZoomFactor in FWorkbook.Options then
-    zoomscale := StrUtils.IfThen(SameValue(AWorksheet.ZoomFactor, 1.0, ZOOM_EPS), '',
-      Format(' zoomScale="%.0f"', [AWorksheet.ZoomFactor*100]))
+    zoomscale := StrUtils.IfThen(SameValue(sheet.ZoomFactor, 1.0, ZOOM_EPS), '',
+      Format(' zoomScale="%.0f"', [sheet.ZoomFactor*100]))
   else
     zoomscale := '';
 
   // BiDiMode
-  case AWorksheet.BiDiMode of
+  case sheet.BiDiMode of
     bdDefault: bidi := '';
     bdLTR    : bidi := ' rightToLeft="0"';
     bdRTL    : bidi := ' rightToLeft="1"';
   end;
 
   // Active cell
-  if (AWorksheet.ActiveCellRow <> cardinal(-1)) and (AWorksheet.ActiveCellCol <> cardinal(-1)) then
-    actCell := GetCellString(AWorksheet.ActiveCellRow, AWorksheet.ActiveCellCol) else
+  if (sheet.ActiveCellRow <> cardinal(-1)) and (sheet.ActiveCellCol <> cardinal(-1)) then
+    actCell := GetCellString(sheet.ActiveCellRow, sheet.ActiveCellCol) else
     actCell := '';
 
   // Selected tab?
-  tabSel := StrUtils.IfThen(AWorksheet = FWorkbook.ActiveWorksheet, ' tabSelected="1"', '');
+  tabSel := StrUtils.IfThen(sheet = book.ActiveWorksheet, ' tabSelected="1"', '');
 
   // Window protection
-  if (soPanesProtection in AWorksheet.Options) and FWorkbook.IsProtected then
+  if (soPanesProtection in sheet.Options) and book.IsProtected then
     windowProtection := ' windowProtection="1"'
   else
     windowProtection := '';
@@ -3611,8 +3677,8 @@ begin
   attr := windowProtection + showGridLines + showHeaders + tabSel + zoomScale + bidi;
 
   // No frozen panes
-  if not (soHasFrozenPanes in AWorksheet.Options) or
-     ((AWorksheet.LeftPaneWidth = 0) and (AWorksheet.TopPaneHeight = 0))
+  if not (soHasFrozenPanes in sheet.Options) or
+     ((sheet.LeftPaneWidth = 0) and (sheet.TopPaneHeight = 0))
   then
   begin
     if actCell = '' then actCell := 'A1';
@@ -3627,10 +3693,10 @@ begin
     ]))
   end else
   begin  // Frozen panes
-    topRightCell := GetCellString(0, AWorksheet.LeftPaneWidth, [rfRelRow, rfRelCol]);
-    bottomLeftCell := GetCellString(AWorksheet.TopPaneHeight, 0, [rfRelRow, rfRelCol]);
-    bottomRightCell := GetCellString(AWorksheet.TopPaneHeight, AWorksheet.LeftPaneWidth, [rfRelRow, rfRelCol]);
-    if (AWorksheet.LeftPaneWidth > 0) and (AWorksheet.TopPaneHeight > 0) then
+    topRightCell := GetCellString(0, sheet.LeftPaneWidth, [rfRelRow, rfRelCol]);
+    bottomLeftCell := GetCellString(sheet.TopPaneHeight, 0, [rfRelRow, rfRelCol]);
+    bottomRightCell := GetCellString(sheet.TopPaneHeight, sheet.LeftPaneWidth, [rfRelRow, rfRelCol]);
+    if (sheet.LeftPaneWidth > 0) and (sheet.TopPaneHeight > 0) then
     begin
       if actCell = '' then
         actCell := bottomRightcell;
@@ -3644,13 +3710,13 @@ begin
           '</sheetView>' +
         '</sheetViews>', [
         attr,
-        AWorksheet.LeftPaneWidth, AWorksheet.TopPaneHeight, bottomRightCell,
+        sheet.LeftPaneWidth, sheet.TopPaneHeight, bottomRightCell,
         topRightCell, topRightCell,
         bottomLeftCell, bottomLeftCell,
         actCell, actCell
       ]))
     end else
-    if (AWorksheet.LeftPaneWidth > 0) then
+    if (sheet.LeftPaneWidth > 0) then
     begin
       if actCell = '' then
         actCell := topRightCell;
@@ -3662,11 +3728,11 @@ begin
           '</sheetView>' +
         '</sheetViews>', [
         attr,
-        AWorksheet.LeftPaneWidth, topRightCell,
+        sheet.LeftPaneWidth, topRightCell,
         actCell, actCell
       ]))
     end else
-    if (AWorksheet.TopPaneHeight > 0) then
+    if (sheet.TopPaneHeight > 0) then
     begin
       if actCell = '' then
         actCell := bottomLeftCell;
@@ -3678,7 +3744,7 @@ begin
           '</sheetView>'+
         '</sheetViews>', [
         attr,
-        AWorksheet.TopPaneHeight, bottomLeftCell,
+        sheet.TopPaneHeight, bottomLeftCell,
         actCell, actCell
       ]));
     end;
@@ -3697,13 +3763,16 @@ var
   idx: Integer;
   fmt: PsCellFormat;
   i: Integer;
+  book: TsWorkbook;
 begin
-  AppendToStream(AStream, Format(
-    '<%s count="%d">', [ANodeName, FWorkbook.GetNumCellFormats]));
+  book := FWorkbook as TsWorkbook;
 
-  for i:=0 to FWorkbook.GetNumCellFormats-1 do
+  AppendToStream(AStream, Format(
+    '<%s count="%d">', [ANodeName, book.GetNumCellFormats]));
+
+  for i:=0 to book.GetNumCellFormats-1 do
   begin
-    fmt := FWorkbook.GetPointerToCellFormat(i);
+    fmt := book.GetPointerToCellFormat(i);
     s := '';
     sAlign := '';
     sProtected := '';
@@ -3711,7 +3780,7 @@ begin
     { Number format }
     if (uffNumberFormat in fmt^.UsedFormattingFields) then
     begin
-      numFmtParams := Workbook.GetNumberFormat(fmt^.NumberFormatIndex);
+      numFmtParams := book.GetNumberFormat(fmt^.NumberFormatIndex);
       if numFmtParams <> nil then
       begin
         numFmtStr := numFmtParams.NumFormatStr;
@@ -3819,7 +3888,7 @@ begin
     '</%s>', [ANodeName]));
 end;
 
-procedure TsSpreadOOXMLWriter.WriteDrawings(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteDrawings(AWorksheet: TsBasicWorksheet);
 var
   i: Integer;
   img: TsImage;
@@ -3827,10 +3896,14 @@ var
   roffs1, coffs1, roffs2, coffs2: Double;
   x, y, w, h: Double;
   descr: String;
+  book: TsWorkbook;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  if AWorksheet.GetImageCount= 0 then
+  if sheet.GetImageCount= 0 then
     exit;
 
+  book := FWorkbook as TsWorkbook;
+
   SetLength(FSDrawings, FCurSheetNum + 1);
   FSDrawings[FCurSheetNum] := CreateTempStream(FWorkbook, Format('fpsD%d', [FCurSheetNum]));
 
@@ -3841,17 +3914,17 @@ begin
               'xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main">');
 
   // Repeat for each image
-  for i:=0 to AWorksheet.GetImageCount - 1 do
+  for i:=0 to sheet.GetImageCount - 1 do
   begin
-    img := AWorksheet.GetImage(i);
-    if FWorkbook.GetEmbeddedObj(img.Index).ImageType = itUnknown then
+    img := sheet.GetImage(i);
+    if book.GetEmbeddedObj(img.Index).ImageType = itUnknown then
       Continue;
-    AWorksheet.CalcImageExtent(i, true,
+    sheet.CalcImageExtent(i, true,
       r1, c1, r2, c2,
       roffs1, coffs1, roffs2, coffs2,  // mm
       x, y, w, h);                     // mm;
 
-    descr := ExtractFileName(FWorkbook.GetEmbeddedObj(img.index).Filename);
+    descr := ExtractFileName(book.GetEmbeddedObj(img.index).Filename);
     if descr = '' then descr := 'image';
 
     AppendToStream(FSDrawings[FCurSheetNum],
@@ -3916,13 +3989,14 @@ end;
 // For each sheet, writes a "drawingX.xml.rels" file to
 // folder "../drawings/_rels". X matches the (1-base) sheet index.
 // See also: WriteVmlDrawingRels
-procedure TsSpreadOOXMLWriter.WriteDrawingRels(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteDrawingRels(AWorksheet: TsBasicWorksheet);
 var
   i: Integer;
   ext: String;
   img: TsImage;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  if (AWorksheet.GetImageCount = 0) then
+  if (sheet.GetImageCount = 0) then
     exit;
 
   SetLength(FSDrawingsRels, FCurSheetNum + 1);
@@ -3934,10 +4008,10 @@ begin
     '<Relationships xmlns="' + SCHEMAS_RELS + '">' + LineEnding);
 
   // Repeat for each image
-  for i:=0 to AWorksheet.GetImageCount - 1 do
+  for i:=0 to sheet.GetImageCount - 1 do
   begin
-    img := AWorksheet.GetImage(i);
-    ext := GetImageTypeExt(FWorkbook.GetEmbeddedObj(img.Index).Imagetype);
+    img := sheet.GetImage(i);
+    ext := GetImageTypeExt((FWorkbook as TsWorkbook).GetEmbeddedObj(img.Index).Imagetype);
     AppendToStream(FSDrawingsRels[FCurSheetNum], Format(
     '  <Relationship Id="rId%d" Type="%s" Target="../media/image%d.%s"/>' + LineEnding, [
        i+1, SCHEMAS_IMAGE, img.Index+1, ext
@@ -3992,7 +4066,7 @@ end;                           *)
     vmlDrawing3.vml  --> Sheet 2 header/footer images
     vmlDrawing4.vml  --> Sheet 3 comments
 -------------------------------------------------------------------------------}
-procedure TsSpreadOOXMLWriter.WriteVmlDrawings(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteVmlDrawings(AWorksheet: TsBasicWorksheet);
 begin
   // At first write the VmlDrawings related to comments
   WriteVmlDrawings_Comments(AWorksheet);
@@ -4001,14 +4075,15 @@ begin
   WriteVmlDrawings_HeaderFooterImages(AWorksheet);
 end;
 
-procedure TsSpreadOOXMLWriter.WriteVMLDrawings_Comments(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteVMLDrawings_Comments(
+  AWorksheet: TsBasicWorksheet);
 var
   comment: PsComment;
   fileindex: Integer;
   index: Integer;
   id: Integer;
 begin
-  if AWorksheet.Comments.Count = 0 then
+  if (AWorksheet as TsWorksheet).Comments.Count = 0 then
     exit;
 
   fileIndex := Length(FSVmlDrawings);
@@ -4035,7 +4110,7 @@ begin
 
   // Write vmlDrawings for each comment (formatting and position of comment box)
   index := 1;
-  for comment in AWorksheet.Comments do
+  for comment in (AWorksheet as TsWorksheet).Comments do
   begin
     id := 1024*(FCurSheetNum+1) + index;     // if more than 1024 comments then use data="1,2,etc" above! -- not implemented yet
     AppendToStream(FSVmlDrawings[fileIndex], LineEnding + Format(
@@ -4110,7 +4185,10 @@ end;
  *)
 
 procedure TsSpreadOOXMLWriter.WriteVMLDrawings_HeaderFooterImages(
-  AWorksheet: TsWorksheet);
+  AWorksheet: TsBasicWorksheet);
+var
+  book: TsWorkbook;
+  sheet: TsWorksheet absolute AWorksheet;
 
   { AName = 'header' or 'footer'
     ATag  = 'L', 'C', 'R', 'x', or ' '
@@ -4124,15 +4202,15 @@ procedure TsSpreadOOXMLWriter.WriteVMLDrawings_HeaderFooterImages(
       exit;
     if ATag = 'x' then
     begin
-      FWorkbook.AddErrorMsg(rsOnlyOneHeaderFooterImageAllowed, [AName]);
+      book.AddErrorMsg(rsOnlyOneHeaderFooterImageAllowed, [AName]);
       exit;
     end;
     if ATag = ' ' then
     begin
-      FWorkbook.AddErrorMsg(rsIncorrectPositionOfImageInHeaderFooter, [AName]);
+      book.AddErrorMsg(rsIncorrectPositionOfImageInHeaderFooter, [AName]);
       exit;
     end;
-    fn := ChangeFileExt(Workbook.GetEmbeddedObj(AImage.Index).FileName, '');
+    fn := ChangeFileExt(book.GetEmbeddedObj(AImage.Index).FileName, '');
     if fn = '' then fn := 'image';
     AppendToStream(AStream, Format(
       ' <v:shape id="%s" o:spid="_x0000_s%d" type="#_x0000_t75"' + LineEnding +
@@ -4157,7 +4235,8 @@ var
   sec: TsHeaderFooterSectionIndex;
   headerTags, footerTags: String;
 begin
-  if not AWorksheet.PageLayout.HasHeaderFooterImages then
+  book := FWorkbook as TsWorkbook;
+  if not sheet.PageLayout.HasHeaderFooterImages then
     exit;
 
   fileIndex := Length(FSVmlDrawings);
@@ -4197,19 +4276,19 @@ begin
   index := 1;
   id := 1024 * (FCurSheetNum+1) + index;
 
-  AWorksheet.PageLayout.GetImageSections(headerTags, footerTags);
+  sheet.PageLayout.GetImageSections(headerTags, footerTags);
 
   // Write the data for the image in each section of the header
   for sec in TsHeaderFooterSectionIndex do
   begin
     tagIndex := ord(sec) + 1;
-    img := AWorksheet.PageLayout.HeaderImages[sec];
+    img := sheet.PageLayout.HeaderImages[sec];
     Process(FSVmlDrawings[fileIndex], rsHeader, headerTags[tagIndex], 'H', img, id, index);
   end;
   // Repeat with footer
   for sec in TsHeaderFooterSectionIndex do
   begin
-    img := AWorksheet.PageLayout.FooterImages[sec];
+    img := sheet.PageLayout.FooterImages[sec];
     tagIndex := ord(sec) + 1;
     Process(FSVmlDrawings[fileIndex], rsFooter, footerTags[tagIndex], 'F', img, id, index);
   end;
@@ -4236,21 +4315,20 @@ end;
   Note: vmlDrawing files of comments do not have a correspondig rels file.
   The index of the rels file must match that of the vmlDrawingX.vml file.
 -------------------------------------------------------------------------------}
-procedure TsSpreadOOXMLWriter.WriteVmlDrawingRels(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteVmlDrawingRels(AWorksheet: TsBasicWorksheet);
 var
   fileindex: Integer;
   sec: TsHeaderFooterSectionIndex;
   rId: Integer;
   img: TsHeaderFooterImage;
-//  imgIdx: Integer;
-//  imgName: String;
   ext: String;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
-  if not AWorksheet.PageLayout.HasHeaderFooterImages then
+  if not sheet.PageLayout.HasHeaderFooterImages then
     exit;
 
   fileIndex := Length(FSVmlDrawingsRels);
-  if AWorksheet.Comments.Count > 0 then
+  if sheet.Comments.Count > 0 then
     inc(fileIndex);  // skip comments for numbering
 
   SetLength(FSVmlDrawingsRels, fileIndex+1);
@@ -4269,12 +4347,10 @@ begin
 
   // Write the data for the image in each section of the header
   for sec in TsHeaderFooterSectionIndex do begin
-    img := AWorksheet.PageLayout.HeaderImages[sec];
+    img := sheet.PageLayout.HeaderImages[sec];
     if img.Index = -1 then
       continue;
-//    imgName := FWorkbook.GetEmbeddedObj(img.Index).Name;
-//    imgIdx := img.Index;
-    ext := GetImageTypeExt(FWorkbook.GetEmbeddedObj(img.Index).ImageType);
+    ext := GetImageTypeExt((FWorkbook as TsWorkbook).GetEmbeddedObj(img.Index).ImageType);
 //    imgIdx := FWorkbook.FindEmbeddedObj(imgName);
     AppendToStream(FSVmlDrawingsRels[fileIndex], Format(
       '  <Relationship Id="rId%d" Target="../media/image%d.%s" '+
@@ -4287,13 +4363,10 @@ begin
 
   // Repeat with footer
   for sec in TsHeaderFooterSectionIndex do begin
-    img := AWorksheet.PageLayout.FooterImages[sec];
+    img := sheet.PageLayout.FooterImages[sec];
     if img.Index = -1 then
       continue;
-//    imgName := FWorkbook.GetEmbeddedObj(img.Index).Name;
-//    imgIdx := img.Index;
-//    imgIdx := FWorkbook.FindEmbeddedObj(imgName);
-    ext := GetImageTypeExt(FWorkbook.GetEmbeddedObj(img.Index).Imagetype);
+    ext := GetImageTypeExt((FWorkbook as TsWorkbook).GetEmbeddedObj(img.Index).Imagetype);
     AppendToStream(FSVmlDrawingsRels[fileIndex], Format(
       '  <Relationship Id="rId%d" Target="../media/image%d.%s" '+  //
          //  e.g.         "rId1"         "..(media/image1.png"
@@ -4309,13 +4382,14 @@ begin
     '</Relationships>');
 end;
 
-procedure TsSpreadOOXMLWriter.WriteWorksheetRels(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteWorksheetRels(AWorksheet: TsBasicWorksheet);
 var
   AVLNode: TAvgLvlTreeNode;
   hyperlink: PsHyperlink;
   s: String;
   target, bookmark: String;
   rId_Comments, rId_Hyperlink, rId_Drawing, rId_DrawingHF: Integer;
+  sheet: TsWorksheet absolute AWorksheet;
 begin
   // Extend stream array
   // NOTE: If no .rels file is written for this sheet at least an empty stream
@@ -4323,8 +4397,8 @@ begin
   SetLength(FSSheetRels, FCurSheetNum + 1);
 
   // Anything to write?
-  if (AWorksheet.Comments.Count = 0) and (AWorksheet.Hyperlinks.Count = 0) and
-     (AWorksheet.GetImageCount = 0) and not (AWorksheet.PageLayout.HasHeaderFooterImages)
+  if (sheet.Comments.Count = 0) and (sheet.Hyperlinks.Count = 0) and
+     (sheet.GetImageCount = 0) and not (sheet.PageLayout.HasHeaderFooterImages)
   then
     exit;
 
@@ -4340,7 +4414,7 @@ begin
     '<Relationships xmlns="%s">' + LineEnding, [SCHEMAS_RELS]));
 
   // Relationships for comments
-  if AWorksheet.Comments.Count > 0 then
+  if sheet.Comments.Count > 0 then
   begin
     AppendToStream(FSSheetRels[FCurSheetNum], Format(
       '  <Relationship Id="rId%d" Target="../comments%d.xml" Type="%s" />' + LineEnding,
@@ -4352,9 +4426,9 @@ begin
   end;
 
   // Relationships for hyperlinks
-  if AWorksheet.Hyperlinks.Count > 0 then
+  if sheet.Hyperlinks.Count > 0 then
   begin
-    AVLNode := AWorksheet.Hyperlinks.FindLowest;
+    AVLNode := sheet.Hyperlinks.FindLowest;
     while Assigned(AVLNode) do
     begin
       hyperlink := PsHyperlink(AVLNode.Data);
@@ -4369,21 +4443,21 @@ begin
           '  <Relationship ' + s + ' />' + LineEnding);
         inc(rId_Hyperlink);
       end;
-      AVLNode := AWorksheet.Hyperlinks.FindSuccessor(AVLNode);
+      AVLNode := sheet.Hyperlinks.FindSuccessor(AVLNode);
     end;
   end;
 
   // Relationships for embedded images
   // relationship with to the ../drawings/drawingX.xml file containing all
   // image infos. X is the 1-base sheet index
-  if AWorksheet.GetImageCount > 0 then
+  if sheet.GetImageCount > 0 then
     AppendToStream(FSSheetRels[FCurSheetNum], Format(
       '  <Relationship Id="rId%d" Target="../drawings/drawing%d.xml" Type="%s" />' + LineEnding,
       [rId_Drawing, FCurSheetNum + 1, SCHEMAS_DRAWING]
     ));
 
   // Relationships for embedded header/footer images
-  if AWorksheet.PageLayout.HasHeaderFooterImages then
+  if sheet.PageLayout.HasHeaderFooterImages then
   begin
     AppendToStream(FSSheetRels[FCurSheetnum], Format(
       '  <Relationship Id="rId%d" Target="../drawings/vmlDrawing%d.vml" Type="%s" />' + LineEnding,
@@ -4466,10 +4540,12 @@ var
   embObj: TsEmbeddedObj;
   embName: String;
   ext: String;
+  book: TsWorkbook;
 begin
-  for i:=0 to FWorkbook.GetEmbeddedObjCount-1 do
+  book := FWorkbook as TsWorkbook;
+  for i:=0 to book.GetEmbeddedObjCount-1 do
   begin
-    embObj := FWorkbook.GetEmbeddedObj(i);
+    embObj := book.GetEmbeddedObj(i);
     stream := embObj.Stream;
     stream.Position := 0;
     ext := GetImageTypeExt(embObj.ImageType);
@@ -4505,9 +4581,9 @@ begin
 
   { Write all worksheets which fills also the shared strings.
     Also: write comments, Drawings, vmlDrawings and relationship files }
-  for i := 0 to Workbook.GetWorksheetCount - 1 do
+  for i := 0 to (Workbook as TsWorkbook).GetWorksheetCount - 1 do
   begin
-    FWorksheet := Workbook.GetWorksheetByIndex(i);
+    FWorksheet := (Workbook as TsWorkbook).GetWorksheetByIndex(i);
     WriteWorksheet(FWorksheet);
     WriteComments(FWorksheet);
     WriteVmlDrawings(FWorksheet);
@@ -4541,7 +4617,10 @@ var
   imgext: TStringList;
   ext: String;
   sheet: TsWorksheet;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
+
   AppendToStream(FSContentTypes,
     XML_HEADER + LineEnding);
   AppendToStream(FSContentTypes,
@@ -4554,13 +4633,13 @@ begin
   AppendToStream(FSContentTypes, Format(
       '<Default Extension="vml" ContentType="%s" />' + LineEnding, [MIME_VMLDRAWING]));
 
-  if Workbook.GetEmbeddedObjCount > 0 then
+  if book.GetEmbeddedObjCount > 0 then
   begin
     imgExt := TStringList.Create;
     try
-      for i:=0 to Workbook.GetEmbeddedObjCount-1 do
+      for i:=0 to book.GetEmbeddedObjCount-1 do
       begin
-        ext := GetImageTypeExt(Workbook.GetEmbeddedObj(i).ImageType);
+        ext := GetImageTypeExt(book.GetEmbeddedObj(i).ImageType);
         j := imgExt.IndexOf(ext);
         if j = -1 then
           imgExt.Add(ext);
@@ -4576,12 +4655,12 @@ begin
   AppendToStream(FSContentTypes,
       '<Override PartName="/xl/workbook.xml" ContentType="' + MIME_SHEET + '" />' + LineEnding);
 
-  for i:=1 to Workbook.GetWorksheetCount do
+  for i:=1 to book.GetWorksheetCount do
   begin
     AppendToStream(FSContentTypes, Format(
       '<Override PartName="/xl/worksheets/sheet%d.xml" ContentType="%s" />' + LineEnding,
         [i, MIME_WORKSHEET]));
-    sheet := Workbook.GetWorksheetByIndex(i-1);
+    sheet := book.GetWorksheetByIndex(i-1);
     if sheet.GetImageCount > 0 then
       AppendToStream(FSContentTypes, Format(
         '<Override PartName="/xl/drawings/drawing%d.xml" ContentType="%s"/>' + LineEnding,
@@ -4616,9 +4695,9 @@ begin
   stotal := '';
 
   // Write print ranges and repeatedly printed rows and columns
-  for i := 0 to Workbook.GetWorksheetCount-1 do
+  for i := 0 to (Workbook as TsWorkbook).GetWorksheetCount-1 do
   begin
-    sheet := Workbook.GetWorksheetByIndex(i);
+    sheet := (Workbook as TsWorkbook).GetWorksheetByIndex(i);
     sheetname := '''' + UTF8TextToXMLText(sheet.Name) + '''';
 
     // Cell block of print range
@@ -4699,53 +4778,55 @@ end;
 procedure TsSpreadOOXMLWriter.WriteWorkbookProtection(AStream: TStream);
 var
   s: String;
+  book: TsWorkbook;
 begin
+  book := FWorkbook as TsWorkbook;
   s := '';
 
-  if Workbook.CryptoInfo.PasswordHash <> '' then
+  if book.CryptoInfo.PasswordHash <> '' then
   begin
-    if Workbook.CryptoInfo.Algorithm = caExcel then
-      s := s + ' workbookPassword="' + Workbook.CryptoInfo.PasswordHash + '"'
+    if book.CryptoInfo.Algorithm = caExcel then
+      s := s + ' workbookPassword="' + book.CryptoInfo.PasswordHash + '"'
     else
     begin
-      s:= s + ' workbookHashVal="' + Workbook.CryptoInfo.PasswordHash + '"';
-      if Workbook.CryptoInfo.Algorithm <> caUnknown then
-        s:= s + ' workbookAlgorithmName="' + AlgorithmToStr(Workbook.CryptoInfo.Algorithm, auExcel) + '"';
+      s:= s + ' workbookHashVal="' + book.CryptoInfo.PasswordHash + '"';
+      if book.CryptoInfo.Algorithm <> caUnknown then
+        s:= s + ' workbookAlgorithmName="' + AlgorithmToStr(book.CryptoInfo.Algorithm, auExcel) + '"';
 
-      if Workbook.CryptoInfo.SaltValue <> '' then
-        s:= s + ' workbookSaltValue="' + Workbook.CryptoInfo.SaltValue + '"';
+      if book.CryptoInfo.SaltValue <> '' then
+        s:= s + ' workbookSaltValue="' + book.CryptoInfo.SaltValue + '"';
 
-      if Workbook.CryptoInfo.SpinCount <> 0 then
-        s:= s + ' workbookSpinCount="' + IntToStr(Workbook.CryptoInfo.SpinCount) + '"';
+      if book.CryptoInfo.SpinCount <> 0 then
+        s:= s + ' workbookSpinCount="' + IntToStr(book.CryptoInfo.SpinCount) + '"';
     end;
   end;
 
   {
-  if Workbook.RevisionsCrypto.Password <> '' then
-    s:= s + ' revisionsPassword="' + Workbook.RevisionsCrypto.Password +'"'
+  if book.RevisionsCrypto.Password <> '' then
+    s:= s + ' revisionsPassword="' + book.RevisionsCrypto.Password +'"'
   else
-  if Workbook.RevisionsCrypto.HashValue <> '' then
+  if book.RevisionsCrypto.HashValue <> '' then
   begin
-    s:= s + ' revisionsHashValue="' + Workbook.RevisionsCrypto.HashValue +'"';
+    s:= s + ' revisionsHashValue="' + book.RevisionsCrypto.HashValue +'"';
 
-    if Workbook.RevisionsCrypto.AlgorithmName <> '' then
-      s:= s + ' revisionsAlgorithm="' + Workbook.RevisionsCrypto.AlgorithmName +'"';
+    if book.RevisionsCrypto.AlgorithmName <> '' then
+      s:= s + ' revisionsAlgorithm="' + book.RevisionsCrypto.AlgorithmName +'"';
 
-    if Workbook.RevisionsCrypto.SaltValue <> '' then
-      s:= s + ' revisionsSaltValue="' + Workbook.RevisionsCrypto.SaltValue +'"';
+    if book.RevisionsCrypto.SaltValue <> '' then
+      s:= s + ' revisionsSaltValue="' + book.RevisionsCrypto.SaltValue +'"';
 
-    if Workbook.RevisionsCrypto.SpinCount <> 0 then
-      s:= s + ' revisionsSpinCount="' + IntToStr( Workbook.RevisionsCrypto.SpinCount ) +'"';
+    if book.RevisionsCrypto.SpinCount <> 0 then
+      s:= s + ' revisionsSpinCount="' + IntToStr( book.RevisionsCrypto.SpinCount ) +'"';
   end;
   }
 
-  if bpLockStructure in Workbook.Protection then
+  if bpLockStructure in book.Protection then
     s := s + ' lockStructure="1"';
 
-  if bpLockWindows in Workbook.Protection then
+  if bpLockWindows in book.Protection then
     s := s + ' lockWindows="1"';
 
-  if bpLockRevision in Workbook.Protection then
+  if bpLockRevision in book.Protection then
     s := s + ' lockRevision="1"';
 
   if s <> '' then
@@ -4761,7 +4842,7 @@ begin
     '<Relationships xmlns="' + SCHEMAS_RELS + '">' + LineEnding);
 
   counter := 1;
-  while counter <= Workbook.GetWorksheetCount do begin
+  while counter <= (Workbook as TsWorkbook).GetWorksheetCount do begin
     AppendToStream(AStream, Format(
       '  <Relationship Id="rId%d" Target="worksheets/sheet%d.xml" Type="%s" />' + LineEnding,
         [counter, counter, SCHEMAS_WORKSHEET]));
@@ -4784,7 +4865,7 @@ begin
     '</Relationships>');
 end;
 
-procedure TsSpreadOOXMLWriter.WriteWorksheet(AWorksheet: TsWorksheet);
+procedure TsSpreadOOXMLWriter.WriteWorksheet(AWorksheet: TsBasicWorksheet);
 var
   rId_Comments: Integer;
   rId_FirstHyperlink: Integer;
@@ -4825,7 +4906,7 @@ begin
     which contains the image-related data of all images in this sheet.
     The file in turn requires an entry "drawingX.xml.rels" in the drawings rels
     folder }
-  if AWorksheet.GetImageCount > 0 then
+  if (AWorksheet as TsWorksheet).GetImageCount > 0 then
     AppendToStream(FSSheets[FCurSheetNum], Format(
       '<drawing r:id="rId%d" />', [rId_Drawing]));
 
@@ -4834,13 +4915,13 @@ begin
     "../comments.xml" file, and one for the "../drawings/vmlDrawingX.vml" file.
     The vmlDrawing file must have an entry "vmlDrawingX.vml.rels" in the drawings
     rels folder. }
-  if AWorksheet.Comments.Count > 0 then
+  if (AWorksheet as TsWorksheet).Comments.Count > 0 then
     AppendToStream(FSSheets[FCurSheetNum], Format(
       '<legacyDrawing r:id="rId%d" />', [rId_Comments]));
 
   { This item is required for all images embedded to a header/footer.
     There must be a corresponding "vmlDrawingX.vml" file in "../drawings". }
-  if AWorksheet.PageLayout.HasHeaderFooterImages then
+  if (AWorksheet as TsWorksheet).PageLayout.HasHeaderFooterImages then
     AppendToStream(FSSheets[FCurSheetNum], Format(
       '<legacyDrawingHF r:id="rId%d" />', [rId_DrawingHF]));
 
@@ -5256,7 +5337,7 @@ begin
     for i := 0 to High(ACell^.RichTextParams) do
     begin
       rtParam := ACell^.RichTextParams[i];
-      fnt := FWorkbook.GetFont(rtParam.FontIndex);
+      fnt := (FWorkbook as TsWorkbook).GetFont(rtParam.FontIndex);
       // Calculate count of characters in this format section
       if i = High(ACell^.RichTextParams) then
         n := L - rtParam.FirstIndex + 1 else