image is not redrawed sometimes when I bring my window to foregrou

From:

=?Utf-8?B?S2Fp?= <Kai@discussions.microsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 1 May 2009 08:32:30 -0700

Message-ID:

<4FD7716D-2975-45B6-8B20-DC7574DB9BF7@microsoft.com>

I use the following Repaint function to redraw my image

    if (IsIconic())
    {
        CPaintDC dc(this); // device context for painting

        SendMessage(WM_ICONERASEBKGND,
reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);

        // Center icon in client rectangle
        int cxIcon = GetSystemMetrics(SM_CXICON);
        int cyIcon = GetSystemMetrics(SM_CYICON);
        CRect rect;
        GetClientRect(&rect);
        int x = (rect.Width() - cxIcon + 1) / 2;
        int y = (rect.Height() - cyIcon + 1) / 2;

        // Draw the icon
        dc.DrawIcon(x, y, m_hIcon);
    }
    else
    {
        HWND hWnd;
        GetDlgItem(IDC_PREVIEW_WINDOW, &hWnd);
        PAINTSTRUCT ps;
        HDC hdc;
        RECT rcClient;

        ::GetClientRect(hWnd, &rcClient);
        hdc = ::BeginPaint(hWnd, &ps);

                                if(m_pWC)
              m_pWC->RepaintVideo(hWnd, hdc);

        ::EndPaint(hWnd, &ps);
        CDialog::OnPaint();
    }

m_pWC is non zero after initialization.

for safety, I added OnActivate function

    CDialog::OnActivate(nState, pWndOther, bMinimized);

    // TODO: Add your message handler code here
    if(nState != WA_INACTIVE)
        UpdateWindow();

It doesn't seem UpdateWindow repaints window immediately.
Any better solution?