TGPGraphics.GetVisibleClipBounds

[Yeray Alonso]

We use the TGPGraphics.GetVisibleClipBounds function to get the current clipping zone, store it and restore later. But this function seems to give a wrong result in Linux and MacOS:

procedure TForm1.FormPaint(Sender: TObject);
var GPGraphics: TGPGraphics;
    tmpR: TGPRectF;
begin
  GPGraphics:=TGPGraphics.Create(Canvas.Handle);
  GPGraphics.GetVisibleClipBounds(tmpR);
  Caption:='Width: ' + FormatFloat('#,##0.00#', tmpR.Width) + ', Height: ' + FormatFloat('#,##0.00#', tmpR.Height);
end;

[Eugene Kryukov]

Actually this function uses native API to get clipping box. Why you think it is wrong ?

[Yeray Alonso]

Our TChart component fails to draw the Legend under some circumstances and I suspect there's something wrong with the clipping. However, at this moment I'm not sure the problem is at TGPGraphics.GetVisibleClipBounds function. Sorry for the confusion.
Here is the result in Linux:

And in MacOS:

However, in 3D the Legend is drawn both for Linux and MacOS.
In Linux:

And in MacOS:

Of course in Windows the Legend is drawn both in 2D and 3D.
At this moment I believe the problem is at how we call TGPGraphics.IntersectClip function.
For 2D Charts we use this ClipRectangle function:

procedure TGDIPlusCanvas.ClipRectangle(Const Rect:TRect);
var tmpR : TRect;
begin
  tmpR:=TeeRect(Rect.Left,Rect.Top-1,Rect.Right,Rect.Bottom+1);
  FGraphics.IntersectClip(MakeRect(tmpR));
end;

For 3D Charts we use this ClipPolygon function:

Procedure TGDIPlusCanvas.ClipPolygon(const Points:Array of TPoint; NumPoints:Integer;
                                     DiffRegion:Boolean=False);
var Region : HRgn;
    r : TGPRegion;
begin
  Region:=CreatePolygonRgn(Points,NumPoints,ALTERNATE);

  r:=TGPRegion.Create(Region);
  try
    PushClipRect;

    if DiffRegion then
       FGraphics.SetClip(r,CombineModeExclude)
    else
       FGraphics.IntersectClip(r);

  finally
    DeleteObject(Region);
    r.Free;
  end;

//DONT:  inherited;
end;

Now I'm testing this new ClipRectangle function, which seems to work fine everywhere:

procedure TGDIPlusCanvas.ClipRectangle(Const Rect:TRect);
var tmpR : TRect;
{$IFNDEF MSWINDOWS}
    tmpP   : TFourPoints;
    Region : HRgn;
    r      : TGPRegion;
{$ENDIF}
begin
  PushClipRect;

  tmpR:=TeeRect(Rect.Left,Rect.Top-1,Rect.Right,Rect.Bottom+1);

  {$IFDEF MSWINDOWS}
  FGraphics.IntersectClip(MakeRect(tmpR));
  {$ELSE}
  try
    RectToFourPoints(tmpR, 0, tmpP);
    Region:=CreatePolygonRgn(tmpP,4,ALTERNATE);
    r:=TGPRegion.Create(Region);

    FGraphics.IntersectClip(r);
  finally
    DeleteObject(Region);
    r.Free;
  end;
  {$ENDIF}
end;

[Yeray Alonso]

Hmmm, this function works in respect to the Legend drawing, but it doesn't do the clipping correctly in Linux&MacOS:

Linux:

MacOS:

Windows:

I've also tested with this function to do the same in all the platforms, with the same results above:

procedure TGDIPlusCanvas.ClipRectangle(Const Rect:TRect);
var tmpR : TRect;
    tmpP   : TFourPoints;
    Region : HRgn;
    r      : TGPRegion;
begin
  PushClipRect;

  tmpR:=TeeRect(Rect.Left,Rect.Top-1,Rect.Right,Rect.Bottom+1);

  try
    RectToFourPoints(tmpR, 0, tmpP);
    Region:=CreatePolygonRgn(tmpP,4,ALTERNATE);
    r:=TGPRegion.Create(Region);

    FGraphics.IntersectClip(r);
  finally
    DeleteObject(Region);
    r.Free;
  end;
end;

[Yeray Alonso]

I've simplified the issue removing any reference to TeeChart. Here you have the code to reproduce the clipping problem in Linux&MacOS:

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormPaint(Sender: TObject);
var G: TGPGraphics;
    chartRect: TRect;
    oldClipRect,
    seriesRect,
    legendRect: TGPRect;
    tmpP   : Array[0..3] of TPoint;
    Region : HRgn;
    r      : TGPRegion;
begin
  G:=TGPGraphics.Create(Canvas.Handle);

  legendRect.Width:=100;
  legendRect.Height:=200;
  legendRect.X:=ClientRect.Width-legendRect.Width-50;
  legendRect.Y:=50;

  chartRect:=Rect(50,50,legendRect.X-200+50,clientRect.Height-100);

  seriesRect.X:=chartRect.Left+chartRect.Width-50;
  seriesRect.Width:=100;
  seriesRect.Y:=chartRect.Top+50;
  seriesRect.Height:=chartRect.Height;

  //draw Chart rectangle
  G.FillRectangle(TGPSolidBrush.Create(MakeColor(255,255,255)), MakeRect(chartRect));
  G.DrawRectangle(TGPPen.Create(MakeColor(0,0,0)), MakeRect(chartRect));

  //save clipping rect
  G.GetVisibleClipBounds(oldClipRect);

  //clip rectangle
  try
    tmpP[0]:=Point(chartRect.Left,chartRect.Top);
    tmpP[1]:=Point(chartRect.Left,chartRect.Bottom);
    tmpP[2]:=Point(chartRect.Right,chartRect.Bottom);
    tmpP[3]:=Point(chartRect.Right,chartRect.Top);
    Region:=CreatePolygonRgn(tmpP,4,ALTERNATE);
    r:=TGPRegion.Create(Region);
    G.IntersectClip(r);
  finally
    DeleteObject(Region);
    r.Free;
  end;

  //drawSeries
  G.FillRectangle(TGPSolidBrush.Create(MakeColor(125,200,255)), seriesRect);
  G.DrawRectangle(TGPPen.Create(MakeColor(0,0,0)), seriesRect);

  //restore saved clipping
  G.SetClip(oldClipRect);

  //drawLegend
  G.FillRectangle(TGPSolidBrush.Create(MakeColor(255,125,125)), legendRect);
  G.DrawRectangle(TGPPen.Create(MakeColor(0,0,0)), legendRect);
end;

[Eugene Kryukov]

Thank you for detailed report. We start working on it.

One question, why don't you just use TGPGraphics.IntersectClip(const rect: TGPRectF) in ClipRectangle, but use such complicated code with Region ?

[Eugene Kryukov]

Fixed at 1.06

[Yeray Alonso]

One question, why don't you just use TGPGraphics.IntersectClip(const rect: TGPRectF) in ClipRectangle, but use such complicated code with Region ?

Precisely the TGPRectF version of TGPGraphics.IntersectClip wasn't working as expected in Linux&MacOS and I found the TGPRegion version was working well everywhere.

Now, with v1.06, it seems to work perfectly.
Thanks!