深入解析钩子和动态链接库（下）

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

*                             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

The server application

在头文件中，将下面的增加到类的protected段：

afx_msg LRESULT OnMyMouseMove(WPARAM,LPARAM);

在application 文件中, 增加以下代码到文件前部。

UINT UWM_MOUSEMOVE = ::RegisterWindowMessage(UWM_MOUSEMOVE_MSG);

在 MESSAGE_MAP, 增加以下代码

//{AFX_MSG comments:

ON_REGISTERED_MESSAGE(UWM_MOUSEMOVE, OnMyMouseMove)

In your application file, add the following function:

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+1^st 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。