Re: Actions for custom widgets in PyGTK

[Piñeiro <apinheiro igalia com>]

On 08/01/2012 12:03 AM, Sascha Silbe wrote:
> Sascha Silbe <silbe activitycentral com> writes:
>
>> Is there a way of using AtkObject subclasses with GTK subclasses other
>> than duplicating the entire set of custom widgets (and probably quite a
>> few stock ones as well) and registering an AtkObject factory for each of
>> them?
> The minor detail I missed was that I need to override
> do_get_accessible() rather than get_accessible(). Thanks to Mike Gorse
> (on #a11y) for digging out a couple of references for me.
>
> It also seems do_get_accessible() needs to have been overridden at class
> definition time, rather than being able to override it on an individual,
> already initialised instance.

Yes all those methods are virtual class methods, so they are required to
be defined at class definition time (as any other Gobject virtual class
methods). This is something that I slightly mentioned here:
https://bugzilla.gnome.org/show_bug.cgi?id=649804#c6

>  That means adding code to each widget
> class (including creating subclasses for stock GTK widgets that we're
> using). Not sure yet if that's feasible; at the very least it's a major
> PITA.

Hmm, initially I thought that you had custom GTK widgets (so custom
widgets needs custom accessibility), but taking into account this
paragraph it seems that you are just using GTK widgets instead of
subclassing them. Is that true?


>
> Python backtrace for do_get_n_actions() invoked on the wrong class:
>
> [...]
>   File "/home/sascha.silbe/sugar-jhbuild/install/lib/python2.7/site-packages/jarabe/desktop/favoritesview.py", line 636, in __init__
>     BuddyIcon.__init__(self, buddy=get_owner_instance(), pixel_size=size)
>   File "/home/sascha.silbe/sugar-jhbuild/install/lib/python2.7/site-packages/jarabe/view/buddyicon.py", line 38, in __init__
>     self._update_color()
>   File "/home/sascha.silbe/sugar-jhbuild/install/lib/python2.7/site-packages/jarabe/view/buddyicon.py", line 53, in _update_color
>     self.props.xo_color = self._buddy.get_color()
>   File "<string>", line 2, in do_get_n_actions
>   File "/home/sascha.silbe/sugar-jhbuild/install/lib/python2.7/site-packages/sugar/logger.py", line 208, in _trace
>     res = f(*args, **kwargs)
>   File "/home/sascha.silbe/sugar-jhbuild/install/lib/python2.7/site-packages/jarabe/view/eventicon.py", line 293, in do_get_n_actions
>     traceback.print_stack()
>
>
> gdb backtrace for the segfault (sorry about the missing debug symbols,
> will have to rebuild the glib Debian package first):
>
> #1  0x00007ffff4db4724 in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #2  0x00007ffff4dc57b0 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #3  0x00007ffff4dcd72c in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #4  0x00007ffff4dcd8c2 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #5  0x00007ffff4db90e5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #6  0x00007ffff4db8b2e in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #7  0x00007ffff4dbc759 in g_object_set_property () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #8  0x00007ffff3e38e03 in set_property_from_pspec (obj=0xd572f0, attr_name=0x10df054 "xo_color", pspec=<optimized out>, pvalue=<optimized out>)
>     at /home/martin/debian/pkg-gnome/build-area/pygobject-2-2.28.6/gobject/pygobject.c:357
> Python Exception <class 'gdb.error'> There is no member named in_class.: 
> #9  0x00007ffff3e39690 in PyGProps_setattro (self=0x1a76550, attr='xo_color', pvalue=) at /home/martin/debian/pkg-gnome/build-area/pygobject-2-2.28.6/gobject/pygobject.c:406
> [...]
>
> Just to make sure, there's only a single thread:
>
>   Id   Target Id         Frame 
> * 1    Thread 0x7ffff7fda700 (LWP 18084) "python" 0x00007fffedeb820c in ?? () from /usr/lib/x86_64-linux-gnu/gtk-2.0/modules/libgail.so

Taking into account this line, it seems that you are using gtk2. Sorry,
initially I thought that you were using gtk3 and gobject introspection.
So, I remembered that conduit developers were trying to do something
similar some years ago, and they wrote some posts about that. Take I
look to posts like this:

http://blogs.gnome.org/johncarr/2008/08/04/conduit-and-accessibility/

I hope this could help you.

Finally, what are your plans in relation to GTK3? A lot of stuff have
changed between GTK2 and GTK3. This includes a lot of fields, but
specifically, it includes the python bindings (gtk2 used static
bindings, gtk3 uses gobject introspection) and accessibility (GTK3 has a
better accessibility support). So if you plan is use GTK3, probably some
of the conclusions of this first investigation will not be valid for GTK3.

BR

-- 
Alejandro Piñeiro Iglesias