Re: [g-a-devel] children-changed signals in at-spi2

[Li Yuan <Li Yuan Sun COM>]

Hi Mark,

On Thu, 2009-12-10 at 00:46 -0800, Mark Doffman wrote:
> Hi Li,
> 
> > Ginn found a bug today that when Firefox created a new window, the
> > window can not be seen in Accerciser. We think the problem might be that
> > the "index" field of "children-changed:add" signal is missing. Actually
> > it is not missing, it is 0.
> 
> If the index is 0 and that isn't actually the child that has been added
> then it will cause problems. The index is used to add new children to
> the cache even if it isn't sent in the UpdateAccessible signal.

Yes, the index is always 0 even if Firefox sends out the signal with
other numbers.
> 
> > 
> > So I checked the code and find atk-bridge does not emit
> > "children-changed" signals anymore. Instead it emits "UpdateAccessible".
> > And on pyatspi2 side, the old cache and the new cache are compared to
> > determine if this is an add or a remove and send "children-change:add"
> > or "children-change:remove" to ATs. (Please correct me if I am wrong.)
> > 
> > This comes up with two questions:
> > 
> > 1. In at-spi2-core/xml/org.freedesktop.atspi.Accessible.xml,
> > "object:children-changed" is one of the signals of accessible. Now
> > atk-bridge doesn't emit it anymore. This can be a problem if we develop
> > another language bindings used by ATs.
> 
> There are a number of inconsistencies in the XML description of the
> protocol. At the moment it doesn't properly match what is going on in
> the code. At some point we will need to do a thorough analysis of it.
> 
Great.
> > 
> > 2. The index information is not passed to ATs. So there may be bugs if
> > ATs rely on the index number (or the AtkObject which is the second
> > arguments of children-changed signal). 
> 
> I'm not sure what you mean by the index information not being passed to
> the AT's.

I mean Firefox sets the index to 2 or other numbers, and sends out the
children-changed:add signal. But on Accerciser side, index is always 0.
So the value of index is not correct.

>  An array of objects is passed to the AT's the index
> information is implicit in the array structure. Its an ordered list.

How the list is passed to AT's? I don't see the children-changed signals
have such a field. Or do you mean ATs should get the list manually when
there is a children-changed signal?

> > 
> > So is it possible to emit "children-changed" signal in atk-bridge and
> > use a separate listener in pyatspi2 to listen it? 
> 
> I've been thinking about doing this. It would make the code in Pyatspi
> simpler, and so might help out if anyone wants to write new bindings. 

Yes.

Thanks,
Li