createellipticrgnindirectu.pas

DelphiWin32核心API参考光盘内容.是学习书籍中的源码,便于学习.

unit CreateEllipticRgnIndirectU;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;

type
  TForm1 = class(TForm)
    procedure FormPaint(Sender: TObject);
    procedure FormResize(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  TheRegion: HRGN;        // holds the elliptic region

implementation

{$R *.DFM}

procedure TForm1.FormPaint(Sender: TObject);
begin
  {erase the current image on the form}
  Canvas.Brush.Color := clBtnFace;
  Canvas.FillRect(BoundsRect);

  {outline the elliptic region in red}
  Canvas.Brush.Color := clRed;
  FrameRgn(Canvas.Handle, TheRegion, Canvas.Brush.Handle, 2, 2);
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  {delete the current region, if it exists}
  if TheRegion<>0 then
    DeleteObject(TheRegion);

  {create a new elliptical region based on the boundaries of the client area}
  TheRegion := CreateEllipticRgnIndirect(ClientRect);

  {repaint the form}
  Repaint;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  {delete the elliptic region}
  DeleteObject(TheRegion);
end;

end.