本例效果图:
![](https://www.cnblogs.com/images/cnblogs_com/del/129733/o_84305.gif)
![](https://www.cnblogs.com/images/cnblogs_com/del/129733/o_84305.gif)
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls; type TForm1 = class(TForm) Button1: TButton; RadioGroup1: TRadioGroup; procedure FormCreate(Sender: TObject); procedure RadioGroup1Click(Sender: TObject); procedure Button1Click(Sender: TObject); procedure FormDblClick(Sender: TObject); end; var Form1: TForm1; implementation {$R *.dfm} var pt: TPoint; RGN_Mode: Integer = RGN_AND; procedure TForm1.FormCreate(Sender: TObject); begin pt.X := Width; pt.Y := Height; RadioGroup1.Items.CommaText := 'RGN_AND,RGN_OR,RGN_XOR,RGN_DIFF,RGN_COPY'; RadioGroup1.ItemIndex := 0; end; procedure TForm1.RadioGroup1Click(Sender: TObject); begin RGN_Mode := RadioGroup1.ItemIndex + 1; end; procedure TForm1.Button1Click(Sender: TObject); var rgn1,rgn2: HRGN; begin rgn1 := CreateEllipticRgn(10,10,110,110); rgn2 := CreateEllipticRgn(80,10,180,110); CombineRgn(rgn1, rgn1, rgn2, RGN_Mode); SetWindowRgn(Handle, rgn1, True); end; procedure TForm1.FormDblClick(Sender: TObject); var rgn: HRGN; begin rgn := CreateRectRgn(0, 0, pt.X, pt.Y); SetWindowRgn(Handle, rgn, True); end; end.