Re: Xlib: unexpected async reply (sequence #####)!

[David Nečas (Yeti) <yeti physics muni cz>]

On Sat, Aug 04, 2007 at 09:38:25PM +0800, Gregory Hosler wrote:
> I have a threaded gtk application. The threads create some gui (gtk
> widgets/windows). and most of the time (maybe 80%) everything works as expected.
> Occassionally I will get the message on stdout
>
>       Xlib: unexpected async reply (sequence #####)!
>
> the ### is an x event sequence number
>
> I am suspecting that this is because of the x calls from 2 different threads.
>
> Is this a known problem?
>
> Any way around this ? (I thought gtk was supposed to be thread ok :)

The answer depends on your defintions of `OK', `known' and
`problem':
- Gtk+ is thread-aware
- Gtk+ is not thread-safe

If you operate on the GUI from multiple threads:
- you are responsible for the locking on Unix/X
- it will just not work on MS Windows

See

  http://developer.gnome.org/doc/API/2.0/gdk/gdk-Threads.html

People typically operate on the GUI only from the main
thread (i.e. running gtk_main()) and pass work requests to
it via g_idle_add() or some other queue mechanism.

This topic is discussed here every other week, see the list
archives.

Yeti

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