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Win32编程点滴:消息循环(Message loop)

 2010-01-10 09:37:13 来源:WEB开发网   
核心提示:第五个版本?我想我暂时是想不出第五个版本了,即便是一个简简单单的消息循环,Win32编程点滴:消息循环(Message loop)(3),也 还有很多深层次的东西可以挖掘,我们平时用惯了MFC/ATL/WTL之类的框架,但是还是需要对此有 一定了解的,最后,它们已经将消息循环封装的 很好了,很多东西都已经自动处理了

第五个版本?

我想我暂时是想不出第五个版本了,即便是一个简简单单的消息循环,也 还有很多深层次的东西可以挖掘。我们平时用惯了MFC/ATL/WTL之类的框架,它们已经将消息循环封装的 很好了,很多东西都已经自动处理了。我想,虽然有些东西我们不需要亲自处理,但是还是需要对此有 一定了解的。

最后,就已WTL的消息循环的源代码,结束这篇文章吧:

////////////////////////////////////////////////////////////////////////////// /
// CMessageLoop - message loop implementation

class CMessageLoop
{
public:
    ATL::CSimpleArray<CMessageFilter*> m_aMsgFilter;
    ATL::CSimpleArray<CIdleHandler*> m_aIdleHandler;
    MSG m_msg;

// Message filter operations
    BOOL AddMessageFilter(CMessageFilter*  pMessageFilter)
    {
        return m_aMsgFilter.Add (pMessageFilter);
    }

    BOOL RemoveMessageFilter (CMessageFilter* pMessageFilter)
    {
        return  m_aMsgFilter.Remove(pMessageFilter);
    }

// Idle handler  operations
    BOOL AddIdleHandler(CIdleHandler* pIdleHandler)
    {
        return m_aIdleHandler.Add(pIdleHandler);
    }

     BOOL RemoveIdleHandler(CIdleHandler* pIdleHandler)
    {
         return m_aIdleHandler.Remove(pIdleHandler);
    }

#ifndef  _ATL_NO_OLD_NAMES
    // for compatilibility with old names only
     BOOL AddUpdateUI(CIdleHandler* pIdleHandler)
    {
         ATLTRACE2(atlTraceUI, 0, _T("CUpdateUIObject and AddUpdateUI are deprecated.  Please change your code to use CIdleHandler and OnIdle\n"));
         return AddIdleHandler(pIdleHandler);
    }

    BOOL  RemoveUpdateUI(CIdleHandler* pIdleHandler)
    {
        ATLTRACE2 (atlTraceUI, 0, _T("CUpdateUIObject and RemoveUpdateUI are deprecated. Please  change your code to use CIdleHandler and OnIdle\n"));
         return RemoveIdleHandler(pIdleHandler);
    }
#endif // ! _ATL_NO_OLD_NAMES

// message loop
    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;
    }

    static BOOL IsIdleMessage(MSG* pMsg)
    {
        // These messages should NOT cause idle  processing
        switch(pMsg->message)
        {
         case WM_MOUSEMOVE:
#ifndef _WIN32_WCE
        case  WM_NCMOUSEMOVE:
#endif // !_WIN32_WCE
        case WM_PAINT:
         case 0x0118:    // WM_SYSTIMER (caret blink)
             return FALSE;
        }

        return TRUE;
     }

// Overrideables
    // Override to change message  filtering
    virtual BOOL PreTranslateMessage(MSG* pMsg)
    {
        // loop backwards
        for(int i =  m_aMsgFilter.GetSize() - 1; i >= 0; i--)
        {
             CMessageFilter* pMessageFilter = m_aMsgFilter[i];
             if(pMessageFilter != NULL && pMessageFilter->PreTranslateMessage(pMsg))
                return TRUE;
        }
         return FALSE;   // not translated
    }

    //  override to change idle processing
    virtual BOOL OnIdle(int  /*nIdleCount*/)
    {
        for(int i = 0; i <  m_aIdleHandler.GetSize(); i++)
        {
             CIdleHandler* pIdleHandler = m_aIdleHandler[i];
            if (pIdleHandler != NULL)
                pIdleHandler->OnIdle();
        }
        return FALSE;   // don't continue
    }
};

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