Drawing on FMX canvas with WinApi functions - delphi

Question

This question looks very simple, with VCL this is works fine (Image is TImage on VCL):
procedure TFormMain.btnDrawBackgroundClick(Sender: TObject);
var
theme: HTHEME;
begin
theme := OpenThemeData(0, 'TASKDIALOG');
if theme <> 0 then
try
DrawThemeBackground(theme,
Image.Canvas.Handle,
TDLG_SECONDARYPANEL,
0,
Image.ClientRect,
nil);
finally
CloseThemeData(theme);
end;
end;
Question: what I should change to get the same effect with FMX (on Windows)

Answer 1

Based on this answer you simply can't do that.
The problem is that with Firemonkey, you only have a single device
context for the form and not one for each component. When a component
needs to be redrawn, it gets passed the forms canvas but with clipping
and co-ordinates mapped to the components location.
But there is always some workaround and you can try something like this.
procedure TFormMain.btnDrawBackgroundClick(Sender: TObject);
var
lTheme : HTHEME;
lStream : TMemoryStream;
lBitmap : Vcl.Graphics.TBitmap;
begin
lTheme := OpenThemeData(0, 'TASKDIALOG');
if lTheme <> 0 then
try
lBitmap := Vcl.Graphics.TBitmap.Create;
try
lBitmap.Width := Round(Image.Width);
lBitmap.Height := Round(Image.Height);
DrawThemeBackground(lTheme, lBitmap.Canvas.Handle, TDLG_SECONDARYPANEL, 0,
Rect(0, 0, lBitmap.Width, lBitmap.Height), nil);
lStream := TMemoryStream.Create;
try
lBitmap.SaveToStream(lStream);
Image.Bitmap.LoadFromStream(lStream);
finally
lStream.Free;
end;
finally
lBitmap.Free;
end;
finally
CloseThemeData(lTheme);
end;
end;