Added: support for custom drawing procedures

Source/X2CLGraphicList.pas

@@ -24,6 +24,7 @@ uses
 {$IFDEF VER150}
 {$WARN UNSAFE_CODE OFF}
 {$WARN UNSAFE_CAST OFF}
+{$WARN UNSAFE_TYPE OFF}
 {$ENDIF}
 
 
@@ -32,6 +33,13 @@ type
   TX2GraphicList      = class;
   TX2GraphicContainer = class;
 
+
+  TX2GLCustomDrawImageProc = function(ACanvas: TCanvas;
+                                      AGraphicList: TX2GraphicList;
+                                      AIndex: Integer;
+                                      AX, AY: Integer;
+                                      AEnabled: Boolean): Boolean;
+
   {
     :$ Holds a single graphic.
   }
@@ -190,6 +198,11 @@ type
     property StretchMode:   TX2GLStretchMode      read FStretchMode write SetStretchMode  default smCrop;
   end;
 
+
+  procedure X2GLRegisterCustomDrawImageProc(ACustomDrawImageProc: TX2GLCustomDrawImageProc);
+  procedure X2GLUnregisterCustomDrawImageProc(ACustomDrawImageProc: TX2GLCustomDrawImageProc);
+
+
 implementation
 uses
   Forms,
@@ -197,6 +210,10 @@ uses
   SysUtils;
 
 
+var
+  CustomDrawImageProcs: TList;
+
+
 type
   PClass          = ^TClass;
 
@@ -223,6 +240,47 @@ type
 
 
 
+procedure X2GLRegisterCustomDrawImageProc(ACustomDrawImageProc: TX2GLCustomDrawImageProc);
+var
+  procPointer: Pointer absolute ACustomDrawImageProc;
+
+begin
+  if CustomDrawImageProcs.IndexOf(procPointer) = -1 then
+    CustomDrawImageProcs.Add(procPointer);
+end;
+
+
+procedure X2GLUnregisterCustomDrawImageProc(ACustomDrawImageProc: TX2GLCustomDrawImageProc);
+var
+  procPointer: Pointer absolute ACustomDrawImageProc;
+
+begin
+  CustomDrawImageProcs.Remove(procPointer);
+end;
+
+
+function CustomDrawImage(ACanvas: TCanvas; AGraphicList: TX2GraphicList;
+                         AIndex: Integer; AX, AY: Integer; AEnabled: Boolean): Boolean;
+var
+  customProcIndex:  Integer;
+  customProc:       TX2GLCustomDrawImageProc;
+
+begin
+  Result := False;
+
+  for customProcIndex := Pred(CustomDrawImageProcs.Count) downto 0 do
+  begin
+    customProc  := TX2GLCustomDrawImageProc(CustomDrawImageProcs[customProcIndex]);
+
+    if customProc(ACanvas, AGraphicList, AIndex, AX, AY, AEnabled) then
+    begin
+      Result := True;
+      Break;
+    end;
+  end;
+end;
+
+
 {================ TX2GraphicContainerItem
   Initialization
 ========================================}
@@ -900,20 +958,23 @@ begin
      (FContainer.Graphics[AIndex].Picture.Graphic.Empty) then
     exit;
 
+  { First see if any custom draw handlers want to draw the image }
+  if not CustomDrawImage(ACanvas, Self, AIndex, AX, AY, AEnabled) then
+  begin
     if AEnabled then
-    // Enabled, simply draw the graphic
+      { Enabled, simply draw the graphic }
       InternalDrawGraphic(ACanvas, AX, AY)
     else
     begin
-    // Disabled, need to draw the image using 50% transparency. There's only
-    // one problem; not all TGraphic's support that, and neither is there a
-    // generic way of determining a pixel's transparency. So instead, we
-    // blend the background with a copy of the background with the graphic
-    // painted on it...
+      { Disabled, need to draw the image using 50% transparency. There's only
+        one problem; not all TGraphic's support that, and neither is there a
+        generic way of determining a pixel's transparency. So instead, we
+        blend the background with a copy of the background with the graphic
+        painted on it... }
       bmpBackground := TBitmap.Create();
       bmpBlend      := TBitmap.Create();
       try
-      // Get background from canvas
+        { Get background from canvas }
         with bmpBackground do
         begin
           Width       := Self.Width;
@@ -926,7 +987,7 @@ begin
         bmpBlend.Assign(bmpBackground);
         InternalDrawGraphic(bmpBlend.Canvas, 0, 0);
 
-      // Blend graphic with background at 50%
+        { Blend graphic with background at 50% }
         for iY  := 0 to bmpBackground.Height - 1 do
         begin
           pBackground := bmpBackground.ScanLine[iY];
@@ -944,13 +1005,14 @@ begin
             end;
         end;
 
-      // Copy blended graphic back
+        { Copy blended graphic back }
         ACanvas.Draw(AX, AY, bmpBlend);
       finally
         FreeAndNil(bmpBlend);
         FreeAndNil(bmpBackground);
       end;
     end;
+  end;
 
   Result  := True;
 end;
@@ -1338,5 +1400,9 @@ end;
 
 initialization
   RegisterClass(TX2GraphicContainerItem);
+  CustomDrawImageProcs  := TList.Create;
+
+finalization
+  FreeAndNil(CustomDrawImageProcs);
 
 end.