[xorg-bugzilla-noise] [Bug 809] New: (Expose-)Events not received by MT Xt-application until further events generated

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http://freedesktop.org/bugzilla/show_bug.cgi?id=809   
   
           Summary: (Expose-)Events not received by MT Xt-application until
                    further events generated
           Product: xorg
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: P2
         Component: Lib/Xlib
        AssignedTo: xorg-bugzilla-noise at freedesktop.org
        ReportedBy: luik at orthogon.de


I see the following strange behaviour in a multi-threaded Xt-application,
using the OSF/Motif 2.x widget set (but I do not think the bug is related
to Motif):  in a callback procedure, I change the pixmaps of some
pushbuttons and their sensitivity state.  Sometimes, not all of these
modifications are shown on the screen.  I tracked this down to
the fact, that XtNextEvent/XtWaitForSomething block at a time, when
some more Expose events should be in the queue.  In fact they are, because
as soon as some further action is done, which generates another event, e.g
pressing a key or moving the pointer so that a LeaveNotify event is generated,
the Expose events are read from the event queue, processed, and everything
looks fine.

My guess is that the XEventsQueued() called in Xt/NextEvent.c:XtAppNextEvent()
do not properly work.

Note: XFlush() does not help, using "-sync" makes it worse.

Note: I tested this on Red Hat Linux 7.2 with XFree86 4.1.0 and on
Tru64 Unix 4.0F with X11R6(?) and on Sun Solaris 8.  All show this
problem.  I don't run R6.7 yet, but I'm afraid this has not been fixed
yet.   
   
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