From 274ebf2d716517dddb2297f252d2185acd88d65b Mon Sep 17 00:00:00 2001
From: skalogryz <skalogryz@8e941d3f-bd1b-0410-a28a-d453659cc2b4>
Date: Mon, 13 Jan 2020 15:09:10 +0000
Subject: [PATCH] richmemo: adding the check for a valid character offset, for
 most GetXXXX attributes methods. bug #32296

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@7282 8e941d3f-bd1b-0410-a28a-d453659cc2b4
---
 components/richmemo/richmemo.pas | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/components/richmemo/richmemo.pas b/components/richmemo/richmemo.pas
index 1f3df6423..3fff1ff05 100644
--- a/components/richmemo/richmemo.pas
+++ b/components/richmemo/richmemo.pas
@@ -206,6 +206,7 @@ type
       LinkStart, LinkEnd: Integer);
     function GetCanRedo: Boolean; virtual;
 
+    function isValidCharOfs(TextStart: integer): Boolean;
   public
     constructor Create(AOwner: TComponent); override;
     procedure CopyToClipboard; override;
@@ -677,7 +678,8 @@ function TCustomRichMemo.GetTextAttributes(TextStart: Integer; var TextParams: T
 begin
   if not HandleAllocated then HandleNeeded;
   if HandleAllocated then
-    Result := TWSCustomRichMemoClass(WidgetSetClass).GetTextAttributes(Self, TextStart, TextParams)
+    Result := isValidCharOfs(TextStart)
+              and TWSCustomRichMemoClass(WidgetSetClass).GetTextAttributes(Self, TextStart, TextParams)
   else
     Result := false;
 end;
@@ -686,7 +688,7 @@ function TCustomRichMemo.GetStyleRange(CharOfs: Integer; var RangeStart,
   RangeLen: Integer): Boolean;
 begin
   if HandleAllocated then begin
-    Result := TWSCustomRichMemoClass(WidgetSetClass).GetStyleRange(Self, CharOfs, RangeStart, RangeLen);
+    Result := isValidCharOfs(CharOfs) and TWSCustomRichMemoClass(WidgetSetClass).GetStyleRange(Self, CharOfs, RangeStart, RangeLen);
     if Result and (RangeLen = 0) then RangeLen := 1;
   end else begin
     RangeStart := -1;
@@ -698,8 +700,9 @@ end;
 function TCustomRichMemo.GetParaAlignment(TextStart: Integer;
   var AAlign: TParaAlignment): Boolean;
 begin
-  Result := HandleAllocated and
-    TWSCustomRichMemoClass(WidgetSetClass).GetParaAlignment(Self, TextStart, AAlign);
+  Result := HandleAllocated
+    and isValidCharOfs(TextStart)
+    and TWSCustomRichMemoClass(WidgetSetClass).GetParaAlignment(Self, TextStart, AAlign);
 end;
 
 function TCustomRichMemo.GetParaAlignment(TextStart: Integer): TParaAlignment;
@@ -718,7 +721,8 @@ function TCustomRichMemo.GetParaMetric(TextStart: Integer;
   var AMetric: TParaMetric): Boolean;
 begin
   if HandleAllocated then
-    Result := TWSCustomRichMemoClass(WidgetSetClass).GetParaMetric(Self, TextStart, AMetric)
+    Result := isValidCharOfs(TextStart)
+      and TWSCustomRichMemoClass(WidgetSetClass).GetParaMetric(Self, TextStart, AMetric)
   else
     Result := false;
 end;
@@ -752,7 +756,8 @@ begin
   Result:=false;
   if not HandleAllocated then HandleNeeded;
   if HandleAllocated then
-    Result:=TWSCustomRichMemoClass(WidgetSetClass).GetParaRange(Self, CharOfs, ParaRange);
+    Result:=isValidCharOfs(CharOfs)
+            and TWSCustomRichMemoClass(WidgetSetClass).GetParaRange(Self, CharOfs, ParaRange);
 end;
 
 function TCustomRichMemo.GetParaRange(CharOfs: Integer; var TextStart,
@@ -777,7 +782,8 @@ begin
   Result:=false;
   if not HandleAllocated then HandleNeeded;
   if HandleAllocated then
-    Result:=TWSCustomRichMemoClass(WidgetSetClass).GetParaTabs(Self, CharOfs, AStopList);
+    Result:= isValidCharOfs(CharOfs)
+      and TWSCustomRichMemoClass(WidgetSetClass).GetParaTabs(Self, CharOfs, AStopList);
 end;
 
 function TCustomRichMemo.GetContStyleLength(TextStart: Integer): Integer;
@@ -1119,6 +1125,14 @@ begin
     Result:=false;
 end;
 
+function TCustomRichMemo.isValidCharOfs(TextStart: integer): Boolean;
+begin
+  // TextStart, where TextStart = GetTextLen, is a location at the end of the text
+  // it's technically a valid character offset (position)
+  // Because it's where the entry should occur
+  Result := (TextStart >= 0) and (TextStart <= GetTextLen);
+end;
+
 function TCustomRichMemo.PrintMeasure(const params: TPrintParams; var est: TPrintMeasure): Boolean;
 begin
   if not Assigned(Printer) then begin