var
Canvas: TCanvas;
begin
Canvas := TCanvas.Create;
Canvas.Handle := GetDC(0);
Canvas.Pen.Style := psSolid;
Canvas.Pen.Color := clRed;
Canvas.Pen.Width := 4;
Canvas.MoveTo(0, 0);
Canvas.LineTo(Screen.Width, Screen.Height);
Canvas.MoveTo(Screen.Width, 0);
Canvas.LineTo(0, Screen.Height);
Canvas.Free;
end;