Delphi限制光标在矩形区域

procedure TForm1.Button3Click(Sender: TObject);
var
rtButton4:TRect;
begin
//获取Button4控件的坐标区域
rtButton4:=Button4.BoundsRect;
//将坐标转换为屏幕坐标
MapWindowPoints(handle,0,rtButton4,2);
//将坐标移动的范围限制在Button4控件上
ClipCursor(@rtButton4);
end;