子类化窗口控件的窗口过程（系统级替换，与直接替换控件的WndProc方法不是一回事）

unit   Unit1;  
   
  interface  
   
  uses  
      Windows,   Messages,   SysUtils,   Classes,   Controls,   Forms,   Dialogs,   StdCtrls;  
   
  type  
      TForm1   =   class(TForm)  
          Edit1:   TEdit;  
          procedure   FormCreate(Sender:   TObject);  
      private  
          {   Private   declarations   }  
          FOldWndProc,   FNewWndProc:   TFarProc;  
          procedure   WindowProc(var   Message:   TMessage);  
      public  
          {   Public   declarations   }  
      end;  
   
  var  
      Form1:   TForm1;  
   
  implementation  
   
  {$R   *.dfm}  
   
  procedure   TForm1.WindowProc(var   Message:   TMessage);  
  begin  
      Message.Result   :=   CallWindowProc(FOldWndProc,   Edit1.Handle,   Message.Msg,  
            Message.WParam,   Message.LParam);  
  end;  
   
  procedure   TForm1.FormCreate(Sender:   TObject);  
  begin  
      FNewWndProc   :=   MakeObjectInstance(WindowProc);  
      FOldWndProc   :=   Pointer(GetWindowLong(Edit1.Handle,   GWL_WNDPROC));  
      SetWindowLong(Edit1.Handle,   GWL_WNDPROC,   LongInt(FNewWndProc));  
  end;  
   
  end.
 
// 其它消息做默认处理
  Result := DefWindowProc(hWnd, uMsg, wParam, lParam);