WTL里双缓冲避免闪烁

 

 1/**////////////////////////////////////////////////////////////////////////////////
 2// CDoubleBufferImpl - Provides double-buffer painting support to any window
 3
 4template <class T>
 5class CDoubleBufferImpl
 6{
 7public:
 8// Overrideables
 9    void DoPaint(CDCHandle /**//*dc*/)
    {
        // must be implemented in a derived class
        ATLASSERT(FALSE);
    }

// Message map and handlers
    BEGIN_MSG_MAP(CDoubleBufferImpl)
        MESSAGE_HANDLER(WM_ERASEBKGND, OnEraseBackground)
        MESSAGE_HANDLER(WM_PAINT, OnPaint)
#ifndef _WIN32_WCE
        MESSAGE_HANDLER(WM_PRINTCLIENT, OnPaint)
#endif // !_WIN32_WCE
    END_MSG_MAP()

    LRESULT OnEraseBackground(UINT /**//*uMsg*/, WPARAM /**//*wParam*/, LPARAM /**//*lParam*/, BOOL& /**//*bHandled*/)
    {
        return 1;   // no background painting needed
    }

    LRESULT OnPaint(UINT /**//*uMsg*/, WPARAM wParam, LPARAM /**//*lParam*/, BOOL& /**//*bHandled*/)
    {
        T* pT = static_cast<T*>(this);
        ATLASSERT(::IsWindow(pT->m_hWnd));

        if(wParam != NULL)
        {
            RECT rect = { 0 };
            pT->GetClientRect(&rect);
            CMemoryDC dcMem((HDC)wParam, rect);
            pT->DoPaint(dcMem.m_hDC);
        }
        else
        {
            CPaintDC dc(pT->m_hWnd);
            CMemoryDC dcMem(dc.m_hDC, dc.m_ps.rcPaint);
            pT->DoPaint(dcMem.m_hDC);
        }

        return 0;
    }
};