WTL 消息流

在_tWinMain里做了一些初始化函数之后，就进入了Run函数，显然Run函数就是消息循环。下面是Run函数的代码：
int Run(LPTSTR /*lpstrCmdLine*/ = NULL, int nCmdShow = SW_SHOWDEFAULT)

{

         CMessageLoop theLoop;

         _Module.AddMessageLoop(&theLoop);

         CMainFrame wndMain;

         if(wndMain.CreateEx() == NULL)

         {

                   ATLTRACE(_T("Main window creation failed!\n"));

                   return 0;

         }

         wndMain.ShowWindow(nCmdShow);

         int nRet = theLoop.Run();

         _Module.RemoveMessageLoop();

         return nRet;

}
 

不出所料，CmessageLoop就是用作消息循环的类，_Module.AddMessageLoop不过是保存一个全局引用，其它地方可以方便的取得CmessageLoop的实例theLoop。

CmessageLoop::Run函数无疑就是消息循环函数了:
int Run()

         {

                   BOOL bDoIdle = TRUE;

                   int nIdleCount = 0;

                   BOOL bRet;

                   for(;;)

                   {

                            while(bDoIdle && !::PeekMessage(&m_msg, NULL, 0, 0, PM_NOREMOVE))

                            {

                                     if(!OnIdle(nIdleCount++))

                                               bDoIdle = FALSE;

                            }

                            bRet = ::GetMessage(&m_msg, NULL, 0, 0);

                            if(bRet == -1)

                            {

                                     ATLTRACE2(atlTraceUI, 0, _T("::GetMessage returned -1 (error)\n"));

                                     continue;   // error, don't process

                            }

                            else if(!bRet)

                            {

                                     ATLTRACE2(atlTraceUI, 0, _T("CMessageLoop::Run - exiting\n"));

                                     break;   // WM_QUIT, exit message loop

                            }

                            if(!PreTranslateMessage(&m_msg))

                            {

                                     ::TranslateMessage(&m_msg);

                                     ::DispatchMessage(&m_msg);

                            }

                            if(IsIdleMessage(&m_msg))

                            {

                                     bDoIdle = TRUE;

                                     nIdleCount = 0;

                            }

                   }

                   return (int)m_msg.wParam;

         }

CmessageLoop::Run函数，不断的从消息队列里取消息，然后分发给对应的窗口。当消息分发到窗口时，自然就是调用窗口的WINPROC函数了。那么WINPROC是在哪里注册，在哪里实现的呢？

         HWND CwindowImpl::Create(HWND hWndParent, RECT& rcPos, LPCTSTR szWindowName = NULL,

                            DWORD dwStyle = 0, DWORD dwExStyle = 0,

                            UINT nID = 0, LPVOID lpCreateParam = NULL)

         {

                   if (T::GetWndClassInfo().m_lpszOrigName == NULL)

                            T::GetWndClassInfo().m_lpszOrigName = GetWndClassName();

                   ATOM atom = T::GetWndClassInfo().Register(&m_pfnSuperWindowProc);

                   dwStyle = T::GetWndStyle(dwStyle);

                   dwExStyle = T::GetWndExStyle(dwExStyle);

                   return CWindowImplBaseT< TBase, TWinTraits >::Create(hWndParent, rcPos, szWindowName,

                            dwStyle, dwExStyle, nID, atom, lpCreateParam);

         } 

原来在窗口创建函数里注册WinClass，因为这是在基类里实现的，它需要从子类窗口中获得WinClass信息。很明显，这里调用GetWndClassInfo获得WinClass信息。但是我们并没有看到子类里实现该函数，应该是宏展开的吧，DECLARE_XXXX_WND_CLASS之类最为可疑：
#define DECLARE_FRAME_WND_CLASS(WndClassName, uCommonResourceID) \

static CFrameWndClassInfo& GetWndClassInfo() \

{ \

         static CFrameWndClassInfo wc = \

         { \

                   { 0, StartWindowProc, \

                     0, 0, NULL, NULL, NULL, (HBRUSH)(COLOR_WINDOW + 1), NULL, WndClassName }, \

                   NULL, NULL, IDC_ARROW, TRUE, 0, _T(""), uCommonResourceID \

         }; \

         return wc; \

}

没错，就是它，原来WINPROC函数名为StartWindowProc。问题又来了：StartWindowProc在哪里实现了，子类没有，自然是基类里了：
template <class TBase, class TWinTraits>

LRESULT CALLBACK CWindowImplBaseT< TBase, TWinTraits >::StartWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

{

         CWindowImplBaseT< TBase, TWinTraits >* pThis = (CWindowImplBaseT< TBase, TWinTraits >*)_Module.ExtractCreateWndData();

         ATLASSERT(pThis != NULL);

         pThis->m_hWnd = hWnd;

         pThis->m_thunk.Init(pThis->GetWindowProc(), pThis);

         WNDPROC pProc = (WNDPROC)&(pThis->m_thunk.thunk);

         WNDPROC pOldProc = (WNDPROC)::SetWindowLong(hWnd, GWL_WNDPROC, (LONG)pProc);

#ifdef _DEBUG

         // check if somebody has subclassed us already since we discard it

         if(pOldProc != StartWindowProc)

                   ATLTRACE2(atlTraceWindowing, 0, _T("Subclassing through a hook discarded.\n"));

#else

         pOldProc; // avoid unused warning

#endif

         return pProc(hWnd, uMsg, wParam, lParam);

}
 

这个函数的实现有点晦涩，主要是不太明白thunk指的是什么。基本功能倒是很明显，只是重新设置了一下WINPROC，也就是说WINPROC被换成新的了，下次再也不会调用StartWindowProc了。很快找到了真正的WINPROC：
template <class TBase, class TWinTraits>

LRESULT CALLBACK CWindowImplBaseT< TBase, TWinTraits >::WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

{

         CWindowImplBaseT< TBase, TWinTraits >* pThis = (CWindowImplBaseT< TBase, TWinTraits >*)hWnd;

         // set a ptr to this message and save the old value

         MSG msg = { pThis->m_hWnd, uMsg, wParam, lParam, 0, { 0, 0 } };

         const MSG* pOldMsg = pThis->m_pCurrentMsg;

         pThis->m_pCurrentMsg = &msg;

         // pass to the message map to process

         LRESULT lRes;

         BOOL bRet = pThis->ProcessWindowMessage(pThis->m_hWnd, uMsg, wParam, lParam, lRes, 0);

         // restore saved value for the current message

         ATLASSERT(pThis->m_pCurrentMsg == &msg);

         pThis->m_pCurrentMsg = pOldMsg;

         // do the default processing if message was not handled

         if(!bRet)

         {

                  if(uMsg != WM_NCDESTROY)

                            lRes = pThis->DefWindowProc(uMsg, wParam, lParam);

                   else

                   {

                            // unsubclass, if needed

                            LONG pfnWndProc = ::GetWindowLong(pThis->m_hWnd, GWL_WNDPROC);

                            lRes = pThis->DefWindowProc(uMsg, wParam, lParam);

                            if(pThis->m_pfnSuperWindowProc != ::DefWindowProc && ::GetWindowLong(pThis->m_hWnd, GWL_WNDPROC) == pfnWndProc)

                                     ::SetWindowLong(pThis->m_hWnd, GWL_WNDPROC, (LONG)pThis->m_pfnSuperWindowProc);

                            // clear out window handle

                            HWND hWnd = pThis->m_hWnd;

                            pThis->m_hWnd = NULL;

                            // clean up after window is destroyed

                            pThis->OnFinalMessage(hWnd);

                   }

         }

         return lRes;

}

在这个函数里，调用ProcessWindowMessage去分发消息，ProcessWindowMessage是在哪里实现的呢？没有找到自然是宏展开的：
#define BEGIN_MSG_MAP(theClass) \

public: \

         BOOL ProcessWindowMessage(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID = 0) \

         { \

                   BOOL bHandled = TRUE; \

                   hWnd; \

                   uMsg; \

                   wParam; \

                   lParam; \

                   lResult; \

                   bHandled; \

                   switch(dwMsgMapID) \

                   { \

#define MESSAGE_HANDLER(msg, func) \

         if(uMsg == msg) \

         { \

                   bHandled = TRUE; \

                   lResult = func(uMsg, wParam, lParam, bHandled); \

                   if(bHandled) \

                            return TRUE; \

         }

#define END_MSG_MAP() \

                            break; \

                   default: \

                            ATLTRACE2(atlTraceWindowing, 0, _T("Invalid message map ID (%i)\n"), dwMsgMapID); \

                            ATLASSERT(FALSE); \

                            break; \

                   } \

                   return FALSE; \

         }
原来BEGIN_MSG_MAP等函数就是用展开ProcessWindowMessage函数的，而ProcessWindowMessage又是为用来实现WinProc函数的，这下消息的流动过程就很清楚了。

另外与消息处理函数的两个类是CmessageFilter和CidleHandler，两者都是接口类，各定义了一个纯虚函数。在子类里实现它们，然后注册到CMessageLoop中去，CMessageLoop会在适当的时候调用它们。前者一般来转换快捷键，后者一般用来更新界面。

Trackback: http://tb.blog.csdn.net/TrackBack.aspx?PostId=1803034