WinAPI: SetRectRgn - 将区域转换成矩形区域

本例效果图:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs;



type

  TForm1 = class(TForm)

    procedure FormClick(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



var f: Boolean;



procedure TForm1.FormClick(Sender: TObject);

const

  n = 50;

var

  Rgn: HRGN;

  x1,y1,x2,y2: Integer;

begin

  Repaint;



  x1 := n;

  y1 := n div 2;

  x2 := ClientWidth - n;

  y2 := ClientHeight - n;



  {建立椭圆区域}

  Rgn := CreateEllipticRgn(x1, y1, x2, y2);



  {转换为矩形区域 - 谈不上是转换, 是重新定制了一个矩形区域, 只是用了原来的区域句柄而已}

  if f then SetRectRgn(Rgn, 11, 11, 111, 111);

  f := not f;



  {绘制区域}

  Canvas.Brush.Color := clSilver;

  Canvas.Brush.Style := bsCross;

  FillRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle);



  Canvas.Brush.Color := clRed;

  Canvas.Brush.Style := bsSolid;

  FrameRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle, 2, 2);



  DeleteObject(Rgn);

end;



end.