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Re: /dev/windows and select() [was Re: Slow response to keypresses in xorg-server-1.8.0-1]
On Aug 29 16:41, Corinna Vinschen wrote:
> On Aug 29 16:17, Corinna Vinschen wrote:
> > On Aug 29 14:39, Jon TURNEY wrote:
> > > On 08/08/2010 12:04, Andy Koppe wrote:
> > > >On 7 August 2010 23:07, Jon TURNEY wrote:
> > > >>Hmmm, looking again at the implementation of select(), I don't immediately
> > > >>see that when waiting on /dev/windows, it checks that the message queue has
> > > >>old messages on it before waiting. The MSDN documentation for
> > > >>MsgWaitForMultipleObjects() seems to says that messages which had arrived
> > > >>before the last PeekMessage() etc. aren't considered new and so don't end
> > > >>the wait?
> > > >[...]
> > Thanks for the testcase. I examined this and I think I have a
> > workaround. MSDN states that there's a flag QS_ALLPOSTMESSAGE for
> > MsgWaitForMultipleObjects, which is not cleared by PeekMessage, if the
> > wMsgFilterMin and wMsgFilterMax arguments are not both 0. So, what I
> > did was to add the QS_ALLPOSTMESSAGE flag to the
> > MsgWaitForMultipleObjects call in select.cc, and to change the
> > PeekMessage call in select.cc:peek_windows() from
> > PeekMessage (&m, (HWND) h, 0, 0, PM_NOREMOVE)
> > to
> > PeekMessage (&m, (HWND) h, 1, UINT_MAX, PM_NOREMOVE)
> > Same in your above test application. This appears to do the trick.
> > However, I'm not exactly sure if that's a valid fix. Patch below.
> Hmm, this ignores the potential WM_NULL message, afaics. For some
> reason, using
> PeekMessage (&m, (HWND) h, 0, UINT_MAX, PM_NOREMOVE)
> results in MsgWaitForMultipleObjects hanging, too. OTOH, using
> PeekMessage (&m, (HWND) h, 0, 16, PM_NOREMOVE)
> && PeekMessage (&m, (HWND) h, 17, UINT_MAX, PM_NOREMOVE)
> does not. Go figure.
Yeah, I realize I'm talking to myself, but this works, too:
PeekMessage (&m, (HWND) h, 0, UINT_MAX - 1, PM_NOREMOVE)
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
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