From f083df12eb27599898dabc2b53e830f24d0586c0 Mon Sep 17 00:00:00 2001
From: wp_xxyyzz <wp_xxyyzz@8e941d3f-bd1b-0410-a28a-d453659cc2b4>
Date: Sun, 12 Feb 2023 13:28:53 +0000
Subject: [PATCH] LazMapViewer: Extend download engines to be able to handle
 local files (https://www.lazarusforum.de/viewtopic.php?f=18&t=14790).

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@8701 8e941d3f-bd1b-0410-a28a-d453659cc2b4
---
 .../synapse_downloadengine/mvdlesynapse.pas   |  6 +--
 components/lazmapviewer/source/mvdlefpc.pas   |  5 ++-
 .../lazmapviewer/source/mvdownloadengine.pas  | 38 ++++++++++++++++++-
 3 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/components/lazmapviewer/source/addons/synapse_downloadengine/mvdlesynapse.pas b/components/lazmapviewer/source/addons/synapse_downloadengine/mvdlesynapse.pas
index 61755946d..cb6c38d59 100644
--- a/components/lazmapviewer/source/addons/synapse_downloadengine/mvdlesynapse.pas
+++ b/components/lazmapviewer/source/addons/synapse_downloadengine/mvdlesynapse.pas
@@ -29,8 +29,8 @@ type
     FProxyPort: Integer;
     FProxyUsername: string;
     FUseProxy: Boolean;
-  public
-    procedure DownloadFile(const Url: string; str: TStream); override;
+  protected
+    procedure InternalDownloadFile(const Url: string; str: TStream); override;
 
   published
     property UseProxy: Boolean read FUseProxy write FUseProxy default false;
@@ -55,7 +55,7 @@ end;
 
 { TMvDESynapse }
 
-procedure TMvDESynapse.DownloadFile(const Url: string; str: TStream);
+procedure TMvDESynapse.InternalDownloadFile(const Url: string; str: TStream);
 var
   FHttp: THTTPSend;
   realURL: String;
diff --git a/components/lazmapviewer/source/mvdlefpc.pas b/components/lazmapviewer/source/mvdlefpc.pas
index c09103970..7f692954d 100644
--- a/components/lazmapviewer/source/mvdlefpc.pas
+++ b/components/lazmapviewer/source/mvdlefpc.pas
@@ -37,8 +37,9 @@ type
     FProxyUserName: String;
     FProxyPassWord: String;
   {$IFEND}
+  protected
+    procedure InternalDownloadFile(const Url: string; AStream: TStream); override;
   public
-    procedure DownloadFile(const Url: string; AStream: TStream); override;
   {$IF FPC_FullVersion >= 30101}
   published
     property UseProxy: Boolean read FUseProxy write FUseProxy default false;
@@ -63,7 +64,7 @@ uses
 
 { TMVDEFPC }
 
-procedure TMVDEFPC.DownloadFile(const Url: string; AStream: TStream);
+procedure TMVDEFPC.InternalDownloadFile(const Url: string; AStream: TStream);
 var
   http: TFpHttpClient;
 begin
diff --git a/components/lazmapviewer/source/mvdownloadengine.pas b/components/lazmapviewer/source/mvdownloadengine.pas
index da2e4b970..33829a89e 100644
--- a/components/lazmapviewer/source/mvdownloadengine.pas
+++ b/components/lazmapviewer/source/mvdownloadengine.pas
@@ -23,18 +23,52 @@ type
   { TMvCustomDownloadEngine }
 
   TMvCustomDownloadEngine = class(TComponent)
+  protected
+    function GetLocalFileName(const Url: String): String;
+    procedure InternalDownloadFile(const Url: String; AStream: TStream); virtual; abstract;
+    procedure LoadFromLocalFile(const AFileName: String; AStream: TStream);
   public
-    procedure DownloadFile(const {%H-}Url: string; {%H-}AStream: TStream); virtual;
+    procedure DownloadFile(const Url: string; AStream: TStream); virtual;
   end;
 
 
 implementation
 
+uses
+  StrUtils;
+
+const
+  FILE_SCHEME = 'file://';
+
 { TMvCustomDownloadEngine }
 
 procedure TMvCustomDownloadEngine.DownloadFile(const Url: string; AStream: TStream);
 begin
-  // to be overridden...
+  if AnsiStartsText(FILE_SCHEME, Url) then
+    LoadFromLocalFile(GetLocalFileName(Url), AStream)
+  else
+    InternalDownloadFile(Url, AStream);
+end;
+
+// Chops the "file://" off of a local file name.
+// Note: Does not check whether the Url really begins with "file://".
+function TMvCustomDownloadEngine.GetLocalFileName(const Url: String): String;
+begin
+  Result := Copy(Url, Length(FILE_SCHEME) + 1, MaxInt);
+end;
+
+procedure TMvCustomDownloadEngine.LoadFromLocalFile(const AFileName: String;
+  AStream: TStream);
+var
+  fs: TFileStream;
+begin
+  fs := TFileStream.Create(AFileName, fmOpenRead or fmShareDenyWrite);
+  try
+    AStream.CopyFrom(fs, fs.Size);
+    AStream.Position := 0;
+  finally
+    fs.Free;
+  end;
 end;
 
 end.