• <ins id="pjuwb"></ins>
    <blockquote id="pjuwb"><pre id="pjuwb"></pre></blockquote>
    <noscript id="pjuwb"></noscript>
          <sup id="pjuwb"><pre id="pjuwb"></pre></sup>
            <dd id="pjuwb"></dd>
            <abbr id="pjuwb"></abbr>
            隨筆 - 25  文章 - 29  trackbacks - 0
            <2015年11月>
            25262728293031
            1234567
            891011121314
            15161718192021
            22232425262728
            293012345

            常用鏈接

            留言簿(4)

            隨筆分類(22)

            隨筆檔案(25)

            文章分類(2)

            文章檔案(2)

            相冊

            最新隨筆

            搜索

            •  

            積分與排名

            • 積分 - 56695
            • 排名 - 405

            最新評論

            閱讀排行榜

            評論排行榜

            The Problem

            Windows objects are normally represented by HANDLEs. The MFC classes wrap Windows object handles with C++ objects. The handle wrapping functions of the MFC class library provide a way to find the C++ object that is wrapping the Windows object with a particular handle. There are times when a Windows object does not have a C++ wrapper object, however, and at these times a temporary object is created to act as the C++ wrapper.

            mfc 映射的 windows object ---->c++ wrapper
            以下使用 mfc 的函數 如:fromhandle, getdlgitem,都會返回temporary 和 pemanent? c++ wrapper object
            ?注意:
            ???? 零時的 對象 會被在空閑時(OnIdle()函數)被刪除,不能存下在下次消息處理中 使用
            The default OnIdle processing in CWinThread automatically calls DeleteTempMap for each class that supports temporary handle maps
            ////////////////////////////////////////////////////////////
            The Windows objects that use handle maps are:

            • HWND (CWnd and CWnd-derived classes)
            • HDC (CDC and CDC-derived classes)
            • HMENU (CMenu)
            • HPEN (CGdiObject)
            • HBRUSH (CGdiObject)
            • HFONT (CGdiObject)
            • HBITMAP (CGdiObject)
            • HPALETTE (CGdiObject)
            • HRGN (CGdiObject)
            • HIMAGELIST (CImageList)
            • SOCKET (CSocket)

            ///////////////////////////////////////////////

            Given a handle to any of these objects, you can find the MFC object that wraps the handle by calling the static member function FromHandle. For example, given an HWND called hWnd:

            CWnd::FromHandle(hWnd)

            will return a pointer to the CWnd that wraps the hWnd. If that hWnd does not have a specific wrapper object, then a temporary CWnd is created to wrap the hWnd. This makes it possible to get a valid C++ object from any handle.

            Once you have a wrapper object, you can get to its handle through a public member variable. In the case of a CWnd, m_hWnd contains the HWND for that object.

            Attaching Handles to MFC Objects

            Given a newly created handle-wrapper object and a handle to a Windows object, you can associate the two by calling Attach. For example:

            CWnd myWnd;
            myWnd.Attach(hWnd);
            ////mywnd 析構時會調用 destroywindow ,連同 hwnd 一起銷毀




            This makes an entry in the permanent map associating myWnd and hWnd.
            Calling CWnd::FromHandle(hWnd) will now return a pointer to myWnd.
            When myWnd is deleted, the destructor will automatically destroy the hWnd by calling the Windows DestroyWindow function. If this is not desired, the hWnd must be detached from myWnd before the myWnd object is destroyed (normally when leaving the scope at which myWnd was defined). The Detach member function does this.

            myWnd.Detach();

            More About Temporary Objects

            Temporary objects are created whenever FromHandle is given a handle that does not already have a wrapper object. These temporary objects are detached from their handle and deleted by the DeleteTempMap functions. The default OnIdle processing in CWinThread automatically calls DeleteTempMap for each class that supports temporary handle maps. This means that you cannot assume a pointer to a temporary object will be valid past the point of exit from the function where the pointer was obtained, as the temporary object will be deleted during the Windows message-loop idle time.

            很重要:
            在多線程中傳遞 c++ wrapper object 是無效的(無論是 temporary 還是 permanent)
            只能傳遞 windows handle, 換句話就是說, 線程 只能 訪問 自己創建的c++ wrapper object

            Wrapper Objects and Multiple Threads

            Both temporary and permanent objects are maintained on a per-thread basis. That is, one thread cannot access another threads C++ wrapper objects, regardless of whether it is temporary or permanent. As stated above, temporary objects are deleted when the thread which that temporary object belongs enters OnIdle.

            To pass these objects from one thread to another, always send them as their native HANDLE type. Passing a C++ wrapper object from one thread to another will often result in unexpected results.

            ????

            posted on 2006-06-30 11:33 黃大仙 閱讀(1708) 評論(1)  編輯 收藏 引用 所屬分類: c++

            FeedBack:
            # re: MFC中 windows object 和 C++ object 2006-07-08 00:49 flyingxu
            色综合合久久天天综合绕视看| A级毛片无码久久精品免费| 无码国产69精品久久久久网站 | 亚洲av伊人久久综合密臀性色| 思思久久99热只有频精品66| 久久久久久精品免费看SSS| 狠狠综合久久综合88亚洲| 日韩精品久久久久久免费| 久久精品成人免费网站| 久久精品国产亚洲AV影院| 久久精品国内一区二区三区| 中文字幕精品久久| 精品久久久久久久久中文字幕| 欧洲国产伦久久久久久久 | 亚洲国产精品久久电影欧美| 亚洲国产精品一区二区久久| 精品多毛少妇人妻AV免费久久| 久久美女网站免费| 久久丫精品国产亚洲av不卡 | 中文国产成人精品久久不卡| 久久精品中文字幕一区| 国产亚洲色婷婷久久99精品| 久久久SS麻豆欧美国产日韩| 久久精品国产亚洲7777| 丁香狠狠色婷婷久久综合| 国产69精品久久久久9999APGF| 国内精品久久久久久麻豆| 精品久久久久久亚洲| 久久精品亚洲一区二区三区浴池| 久久人人爽人人爽人人片AV麻烦| 久久99国产精品成人欧美| 99久久免费国产精品| 久久免费精品一区二区| 久久精品嫩草影院| 7777久久亚洲中文字幕| 丁香五月网久久综合| 91精品国产综合久久久久久| 久久久久女人精品毛片| 99久久综合狠狠综合久久止| 久久成人国产精品二三区| 91久久国产视频|