mORMot Open Source

I'm trying to copy the VCLCanvas to my own bitmap to mimic transparency, but it doesn't copy anything.
What am I doing wrong?

var
  Fpdf:TPdfDocumentGDI;
  Abmp:TBitmap;
  W, H: Integer;
begin
  Fpdf:=TPdfDocumentGDI.Create;
  Abmp:=TBitmap.Create;
  try
    W:=250;
    H:=150;
    Abmp.Width:=W;
    Abmp.Height:=H;
    Fpdf.DefaultPaperSize:=psA4;
    Fpdf.ScreenLogPixels:=Screen.PixelsPerInch;
    Fpdf.AddPage;
    // Output some text on the canvas
    FPdf.VCLCanvas.TextOut(10,10,'Demo text');
    // Copy the VCLCanvas into the BMP canvas
    Abmp.Canvas.CopyRect(Rect(0,0,W,H),Fpdf.VCLCanvas,Rect(0,0,W,H));
    // add some other text tot the bitmap canvas
    Abmp.Canvas.TextOut(15,15,'Another text');
    // copy the bitmap canvas back onto the vclcanvas
    Fpdf.VCLCanvas.StretchDraw(Rect(200,200,200+W,200+H),Abmp);
    Fpdf.SaveToFile('d:\test.pdf');
  finally
    Abmp.Free;
    Fpdf.Free;
  end;
end;