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indeterminate progress bars

Posted on 2002-07-19
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Last Modified: 2013-11-20
Hi ,
 Does anyone know on how to create indeterminate progress bars in a dialog. I have this big dialog function which will load another DLL and execute functions within it. I need to show in my dialog that a processing is going on. I tried creating a thread and updating the progress control but no luck. It looks like the message pump is blocked until the dialog function is completed. Is there any other way I could implement this

Thanks
Saravana
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Question by:vsaravana
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Expert Comment

by:fl0yd
ID: 7166105
Using multi-threading is the way to go. I don't know what you did, but you must have made a mistake. Did you create the thread to do the actual work? I assume you created a thread to do the updating of the progress bar. In that case the dialog message-handler isn't called until the function doing the calculations has returned.
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Author Comment

by:vsaravana
ID: 7166835
You are correct, I did create the thread for the progress update. It's difficult as per the previous implementation to move tons of code into a thread.
Is there any other option..??

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Accepted Solution

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fl0yd earned 400 total points
ID: 7166939
You could use a CWinThread-function (PumpMessage) that is not really well documented:

void DoEvents() {

    MSG msg = { 0 };
    HWND hwnd = AfxGetMainWnd->m_hWnd;
    while( ::PeekMessage( &msg, hwnd, 0, 0, PM_NOREMOVE ) )
        AfxGetApp()->PumpMessage();
}

Call this function whenever you need to respond to messages. So your code would look like this:

void ThisFunctionTakesForEver() {

    // do some code here
    DoEvents();
    // do some more code...
    DoEvents();
    // and so on...
}

If you use this you won't have to use multithread, which is a very complex field of programming.
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LVL 8

Expert Comment

by:fl0yd
ID: 7166942
ooooops, there was a mistake. The right way to go:

    HWND hwnd = AfxGetMainWnd()->m_hWnd;
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Expert Comment

by:jemax
ID: 7167769
Hi,

you could use CWnd::UpdateWindow it bypasses message queue, so your progress bar will be updated.

HTH,
jemax
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Expert Comment

by:fl0yd
ID: 7167803
UpdateWindow sends a WM_PAINT message if the update region isn't empty -- what good is it if those aren't handled?
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Expert Comment

by:jemax
ID: 7168847
Hi,

forgive me, my stupid comment. I forgot that is not possible to SendMessage into wnd thread from another thread, it would cause to deadlock.

Sorry.
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