Canvas у TShape

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;
 
type
  TShape = class (ExtCtrls.TShape)
  public
    property Canvas;
    procedure Paint; override;
    constructor Create(aowner:TComponent); override;
    destructor Destroy; override;
    procedure ResetCanvas;
    Procedure SaveCanvas;
  protected
    savePaint: boolean;
    CanvasBufer: Tbitmap;
  end;
 
  TForm1 = class(TForm)
    Shape1: TShape;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  // чтото рисуем
  Shape1.Canvas.Pen.Color:=clRed;
  Shape1.Canvas.Brush.Color:=clBlue;
  Shape1.Canvas.MoveTo(20,20);
  Shape1.Canvas.LineTo(100,100);
  Shape1.Canvas.MoveTo(40,20);
  Shape1.Canvas.LineTo(120,100);
  // сохраняем изменения
  Shape1.SaveCanvas;
end;
 
{ TShape }
 
constructor TShape.Create(aowner: TComponent);
begin
  inherited;
  CanvasBufer:=Tbitmap.Create;
  savePaint:=false;
end;
 
destructor TShape.Destroy;
begin
  CanvasBufer.Free;
  inherited;
end;
 
procedure TShape.Paint;
var r:TRect;
begin
  if savePaint then begin
     r:=Bounds(0,0,self.Width,self.Height);
     Canvas.CopyRect(r,CanvasBufer.Canvas,r);
  end else
    inherited;
end;
 
procedure TShape.ResetCanvas;
begin
  savePaint:=false;
  Repaint;
end;
 
procedure TShape.SaveCanvas;
var r:TRect;
begin
  r:=Bounds(0,0,self.Width,self.Height);
  CanvasBufer.Width:=Width;
  CanvasBufer.Height:=Height;
  CanvasBufer.Canvas.CopyRect(r,Canvas,r);
  savePaint:=true;
end;
 
procedure TForm1.Button2Click(Sender: TObject);
begin
  // сброс канваса
  Shape1.ResetCanvas;
end;
 
end.