怎样增加一个OnColorChange的属性？

[sc_arhat]

想写一个TMyPanel，继承自TPanel,增加一个属性OnColorChange便于用户在mypanel颜色改变的时候自定义事件，该怎么定义这个属性呢？VCl的源码没有看明白，哪位大师指点以下，或是推荐本书学习一下，谢谢。

[阿发伯]

没测试，也许有错误

TMyPanel = class(TPanel)
private
FOnColorChange: TNotifyEvent;
procedure CMColorChanged(var Message: TMessage); message CM_COLORCHANGED;
published
property OnColorChange: TNotifyEvent read FOnColorChange write FOnColorChange;
end;


procedure TMyPanle.CMColorChanged(var Message: TMessage);
begin
if Assigned(FOnColorChange) then
FOnColorChange(Self);
inherited;
end;

[阿发伯]

上面的过程实现中TMyPanle写错了，应改为TMyPanel。下面是完整的的测试：

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls, StdCtrls;

type
TMyPanel = class(TPanel)
private
FOnColorChange: TNotifyEvent;
procedure CMColorChanged(var Message: TMessage); message CM_COLORCHANGED;
published
property OnColorChange: TNotifyEvent read FOnColorChange write FOnColorChange;
end;

TForm1 = class(TForm)
Button1: TButton;
procedure FormCreate(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
FPanel: TMyPanel;
procedure ColorChange(Sender: TObject);
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TMyPanel.CMColorChanged(var Message: TMessage);
begin
if Assigned(FOnColorChange) then
FOnColorChange(Self);
inherited;
end;

procedure TForm1.ColorChange(Sender: TObject);
begin
ShowMessage('Ok');
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
FPanel := TMyPanel.Create(Self);
FPanel.Parent := Self;
FPanel.OnColorChange := ColorChange;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
if FPanel.Color <> clRed then
FPanel.Color := clRed
else
FPanel.Color := clWhite;
end;

end.