Re: Too many Post Messages causing app not to refresh

From:

"David Ching" <dc@remove-this.dcsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sun, 12 Aug 2007 12:45:19 -0700

Message-ID:

<irJvi.3352$i85.1909@nlpi061.nbdc.sbc.com>

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:tpkub3d1p2fs05is4ebnnggqnbkejhk058@4ax.com...

Yes, this is expected behavior. WM_TIMER and WM_PAINT messages are
dispatched only when
the message queue is empty.

Take a look at my example of using an I/O Completion Port and the OnIdle
handler to avoid
message pump saturation:

http://www.flounder.com/iocompletion.htm

I had exactly the same problem, and this is the code I wrote to fix it.

This is a nice article, but I would say it is overkill for notifying the
primary thread to repaint. I had the same problem when the worker thread
posted messages to update the progress gauge during a file download. I
optimized it by recognizing that I could throw away paint requests without
penalty (unlike in your case where perhaps the primary thread needs to know
about every IO completion), so my worker thread just called GetTickCount()
when it posted a message, and did not post another message until some delta
(say 500 milliseconds) had elapsed. This prevented too many messages from
being posted but did not cause any adverse side effect.

-- David