Re: Accessibility hang when GTK's main loop is in a second thread (PyGTK)

[Li Yuan <Li Yuan Sun COM>]

Hi Timothy,

For Python threads issues, have you followed the suggestions in 
http://faq.pygtk.org/index.py?req=show&file=faq20.006.htp ? I think your 
way is approach #2 in that page. It is important to wrap main loop and 
other gtk functions with gtk.threads_enter()/gtk.threads_leave().

Timothy Renner wrote:
> We have a Python application using PyGTK, which fires up a second
> thread for the GUI and gtk.main() while main processing happens in the
> Main thread.  Main is responsible for much of the actual drawing of
> the GUI, while the secondary thread is responsible for picking up
> actions on the GUI and prodding the main thread into the appropriate
> responses.  This has been working beautifully with accessibility
> disabled, and under older versions of GTK.
>   
If I understand correctly, there is only one mail loop in the second 
thread, right?
> However, we're running into the problem of the application freezing
> when accessibility is enabled on newer systems (Ubuntu 8.10+ as far as
> I can tell.)  I've narrowed it down to which thread gtk.main() is
> executed in.  If it's the main thread, there are no problems.  If it's
> in the secondary thread, then as soon as the window loses focus, it
> hangs.  Not only does it hang, but the idle functions that I've
> registered with gobject.idle_add(...) will get through one more
> iteration and then never execute again.  It looks like something is
> deadlocking in glib's or gtk's internals when this happens.
>
> Is running in a secondary thread simply not allowed at the moment?
> I'd prefer to find a solution that allows us to keep our current
> structure rather than juggling our threads, but if it must be changed,
> that's acceptable.  At the very least, I'd like to understand better
> the technical details of how GNOME accessibility is interacting with
> our program.
>   
The threads of GNOME accessibility is a long story, please refer to 
http://bugzilla.gnome.org/show_bug.cgi?id=329454 if you are interested in.

Thanks,
Li