Re: Help needed with an a11y related Cheese bug

[Li Yuan <Li Yuan Sun COM>]

Hi Filippo,

I reproduced the bug. I think cheese is hanging. From the trace, I found 
10 threads in cheese, but I don't find any accessibility code involved. 
I am not familiar with cheese's code so I don't know why there is a 
hang. But note that, when accessibility is enabled, a thread could lost 
the gdk lock when it emit a GUI signal, like show a window.

There is such code in atk-bridge:

bridge_threads_leave ();
Accessibility_Registry_notifyEvent(...);
bridge_threads_enter ();

bridge_threads_leave is equal to GDK_THREADS_LEAVE and 
bridge_threads_enter is equal to GDK_THREADS_ENTER.

Maybe this has something to do with the hang.

Li


Filippo Argiolas wrote:
> Hi all,
> I'm sending this mail because of a pretty strange cheese bug that only
> happens if accessibility is enabled.
> I already added the "accessibility" keyword in bugzilla but maybe I
> have more chance to find someone who has a clue about it asking for
> help here :)
>
> The bug in question is
> http://bugzilla.gnome.org/show_bug.cgi?id=566098 (see my last
> comments)
>
> If cheese is started with:
>
> /usr/lib/at-spi/at-spi-registryd&
> GTK_MODULES=gail:atk-bridge cheese
>
> when a photo is taken the screen becomes indefinetely white while it
> should just show the "flash" and hide it right after.
> We do the flash with a fullscreen white window that is shown when a
> photo is taken and fades out gradually reducing its opacity if screen
> is composited or just hides if not.
> The relevant lines from cheese-flash.c are:
>
>   gtk_widget_show_all (GTK_WIDGET (flash_window));
>   flash_priv->flash_timeout_tag = g_timeout_add (FLASH_DURATION,
> cheese_flash_start_fade, (gpointer) flash);
>
> cheese_flash_start_fade is the function that hides or fades out
> flash_window but I don't think it really matters here.
> I believe the GSource attached by that g_timeout_add never gets called
> if a11y modules are loaded.
> I tried increasing the timeout priority but doesn't seem to make any difference.
> There is also some relationship with the event that called
> cheese_flash_fire, I could be wrong but it seems that if the Take
> photo button is activated with the spacebar the problem doesn't occur
> while it does almost every time if the even is a mouse click.
>
> I tried to figure out what could cause this behaviour but I have no
> knowledge about the way accessibility works so I couldn't get any far.
> Did any of you ever heard about g_timeout_add not working with a11y enabled?
> Any idea of what could cause this issue?
>
> Thanks,
>
> Filippo Argiolas
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