Un ejemplito, aunque no con lo de Zarco,
Código Delphi
[-]
var
Desktop: TControlCanvas;
begin
Desktop := TControlCanvas.Create;
try
Desktop.Handle := GetDC(0);
Desktop.Pen.Width := 2;
Desktop.Pen.Color := clRed;
Desktop.MoveTo(0, 0);
Desktop.LineTo(Screen.Width, Screen.Height);
Desktop.MoveTo(0, Screen.Height);
Desktop.LineTo(Screen.Width, 0);
finally
Desktop.Free
end;
end;
// Saludos