procedure TForm1.WriteTextOnScreen;
var
Dc:HDC;
ScreenCanvas:TCanvas;
begin
Dc:=GetDC(0);
ScreenCanvas:=TCanvas.Create;
ScreenCanvas.Handle:=Dc;
ScreenCanvas.TextOut(30,30,'吃饭了！');
ScreenCanvas.Free;
ReleaseDC(Handle,Dc);
end;