深入解析钩子和动态链接库（下）

/****************************************************************

*                             clearMyHook

* Inputs:

*       HWND hWnd: Window whose hook is to be cleared

* Result: BOOL

*       TRUE if the hook is properly unhooked

*       FALSE if you gave the wrong parameter

* Effect:

*       Removes the hook that has been set.

****************************************************************/

__declspec(dllexport) BOOL clearMyHook(HWND hWnd)

   {

    if(hWnd != hWndServer)

       return FALSE;

    BOOL unhooked = UnhookWindowsHookEx(hook);

    if(unhooked)

       hWndServer = NULL;

    return unhooked;

   }

/****************************************************************

*                              msghook

* Inputs:

*       int nCode: Code value

*       WPARAM wParam: parameter

*       LPARAM lParam: parameter

* Result: LRESULT

*

* Effect:

*       If the message is a mouse-move message, posts it back to

*       the server window with the mouse coordinates

* Notes:

*       This must be a CALLBACK function or it will not work!

****************************************************************/

static LRESULT CALLBACK msghook(int nCode, WPARAM wParam, LPARAM lParam)

   {

    // If the value of nCode is < 0, just pass it on and return 0

    // this is required by the specification of hook handlers

    if(nCode < 0)

      { /* pass it on */

       CallNextHookEx(hook, nCode,

                   wParam, lParam);

       return 0;

      } /* pass it on */

    // Read the documentation to discover what WPARAM and LPARAM

    // mean. For a WH_MESSAGE hook, LPARAM is specified as being

    // a pointer to a MSG structure, so the code below makes that

    // structure available

    LPMSG msg = (LPMSG)lParam;

    // If it is a mouse-move message, either in the client area or

    // the non-client area, we want to notify the parent that it has

    // occurred. Note the use of PostMessage instead of SendMessage

    if(msg->message == WM_MOUSEMOVE ||

       msg->message == WM_NCMOUSEMOVE)

      PostMessage(hWndServer,

                  UWM_MOUSEMOVE,   

                  0, 0); 

    // Pass the message on to the next hook

    return CallNextHookEx(hook, nCode, 

                       wParam, lParam);

   } // msghook

afx_msg LRESULT OnMyMouseMove(WPARAM,LPARAM);

UINT UWM_MOUSEMOVE = ::RegisterWindowMessage(UWM_MOUSEMOVE_MSG);

ON_REGISTERED_MESSAGE(UWM_MOUSEMOVE, OnMyMouseMove)

LRESULT CMyClass::OnMyMouseMove(WPARAM, LPARAM)

   {

    // ...do stuff here

    return 0;

   }

    上面是我写的一个小程序。既然我为了钩子花了n+1st 时间，我干脆给它一个好的用户界面。

猫在窗口之内盯着老鼠。小心! 当老鼠足够接近猫时并且它将捉住老鼠你可以下载这个项目并建立它。

真正的关键是DLL 子工程项目; 其他的都不过是陪衬。有几个其它的技术被用在这个例子里，包括各种各样的图画技术，

ClipCursor和SetCapture的用法，区域选择、屏幕更新等等。因此除了展示钩子函数的使用以外，

对初级程序员掌握窗口样式设计编程也有一些价值。