http://www.cnblogs.com/del/archive/2008/10/25/1319318.html

TApplicationEvents.OnMessage 的第二个参数 Handled 如果是 True, 表示消息已经处理过了, 到此为止.

---

unit Unit1;

interface

uses

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

  Dialogs, AppEvnts, StdCtrls;

type

  TForm1 = class(TForm)

    Memo1: TMemo;

    ApplicationEvents1: TApplicationEvents;

    procedure ApplicationEvents1Message(var Msg: tagMSG; var Handled: Boolean);

    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

  end;

var

  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.ApplicationEvents1Message(var Msg: tagMSG;

  var Handled: Boolean);
begin

  if Msg.message = WM_LBUTTONDOWN then

  begin

    Memo1.Lines.Add('OnMessage');

    Handled := False; {Handled 默认是 False, 这句可以省略}

//    Handled := True;  {如果这样, 下面 OnMouseDown 事件将不会得到执行}

  end;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);
begin

  Memo1.Lines.Add('OnMouseDown');
end;

end.

---

我们可以利用这个特性来屏蔽一些消息, 譬如给 TWebBrowser 屏蔽右键菜单:

---

unit Unit1;

interface

uses

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

  Dialogs, OleCtrls, SHDocVw, AppEvnts;

type

  TForm1 = class(TForm)

    WebBrowser1: TWebBrowser;

    ApplicationEvents1: TApplicationEvents;

    procedure FormCreate(Sender: TObject);

    procedure ApplicationEvents1Message(var Msg: tagMSG; var Handled: Boolean);

  end;

var

  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.ApplicationEvents1Message(var Msg: tagMSG;

  var Handled: Boolean);
begin

  if IsChild(WebBrowser1.Handle, Msg.hwnd) and (Msg.message = WM_RBUTTONDOWN) then

  begin

    Handled := True;

  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin

  WindowState := wsMaximized;

  WebBrowser1.Align := alTop;

  WebBrowser1.Navigate('http://www.cnblogs.com/del/');
end;

end.