Windows 消息【二】窗口函数

前一篇文章讲到非队列消息会直接把消息Dispatch到窗口函数上，窗口函数长什么样？

 

//就是一个大case分支

//要想拦截消息，override窗口函数是一个办法！

procedure TCustomForm.WndProc(var Message: TMessage);

var

  FocusHandle: HWND;

  SaveIndex: Integer;

  MenuItem: TMenuItem;

  Canvas: TCanvas;

  DC: HDC;

begin

  with Message do

    case Msg of

      WM_ACTIVATE, WM_SETFOCUS, WM_KILLFOCUS:

        begin

        end;

      CM_EXIT:

        if HostDockSite <> nil then DeActivate;

    end;

end;

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假如我们要用这种方法拦截Edit的Copy,Cut消息怎么办？

难道我们还要继承CustomEdit,再override窗口函数，生成新的MyEdit?有人想，直接用一个函数先把CustomEdit的WndProc替换掉不就行了，使用完毕后，再还原！

//替换窗口函数 

 TForm1 = class(TForm)

    edt1: TEdit;

    btn1: TButton;

    procedure FormCreate(Sender: TObject);

    procedure FormDestroy(Sender: TObject);

  private

    FOldWndProc:  TWndMethod;



    { Private declarations }

  public

    { Public declarations }

      procedure  NewWndProc(var  Message:  TMessage);  



  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure  TForm1.NewWndProc(var  Message:  TMessage);

begin

    if  (Message.Msg  <>  WM_CUT)  and  (Message.Msg  <>  WM_COPY)  and

        (Message.Msg  <>  WM_PASTE)  then

        FOldWndProc(Message);

end;



procedure TForm1.FormCreate(Sender: TObject);

begin

   FOldWndProc  :=  edt1.WindowProc;

   edt1.WindowProc  :=  NewWndProc;



end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  edt1.WindowProc  :=  FOldWndProc;

end;

end.

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