Re: image is not redrawed sometimes when I bring my window to fore

From:

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

Newsgroups:

microsoft.public.vc.mfc

Date:

Sat, 2 May 2009 10:16:01 -0700

Message-ID:

<EF07567A-F4F3-4B26-8305-DD9B6954E534@microsoft.com>

Sorry, It is typo. It is my OnPaint derived from CDialog::OnPaint. In it,
    if (IsIconic())
    {
                 ...
                 }

was generated by VS2008 when CDialog-based application was created. When
you download Microsoft SDK, then look at DirectShow samples, you would see
the snippet.

"Joseph M. Newcomer" wrote:

More and more we find that Doug Harrison's post is dead-on accurate. See

http://www.flounder.com/msdn_documentation_errors_and_omissions.htm#Harrison

If I could have read the example you cited I might be able to say more about why it is
completely inappropriate, but as you have already been advised, using BeginPaint() is
deeply suspect, and if you are calling your RePaint() method from anyplace other than an
OnPaint/OnDraw handler (in which case the secondary CPaintDC is *absolutely* incorrect!)
then your code is dead wrong. You cannot show us some random out-of-context piece of code
and expect us to say much about it, except the obvious facts that it makes no sense
whatsoever in either branch of the if-statement. But we can't tell you how to fix it. You
need to give us more information to allow that.
joe

On Sat, 2 May 2009 04:51:01 -0700, Kai <Kai@discussions.microsoft.com> wrote:

Hi All,

Thank you for your help. I posted my snippet from MyWnd::RePaint(). But

        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);

is copied from windowless.cpp from a DirectShow sample code as follows

C:\Program Files\Microsoft
SDKs\Windows\v6.1\Samples\Multimedia\DirectShow\VMR9\Windowless

"Kai" wrote:

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?

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm