Re: [orca-list] some programmers want to contribute to orca.

[orca yokoy de]

Hello Peter,
thanks for that fine explanation. I think it is much clearer now why we need another technologie side by side 
to AT-SPI. 

On the XO we have a special case. Nearly all application, say "Activities", and the desktop environment 
"Sugar" are python (pygtk, gygame) based. Would it be possible to modify ORCA in a comfortable way to 
communicate directly with these activities and sugar?

regards,

yokoy

On Wed, 15 Aug 2007 22:51:00 -0700
Peter Korn <Peter Korn Sun COM> wrote:

> Hi Halim, gang,
>
> > Hi,
> > On Mi, Aug 15, 2007 at 10:53:06 +0200, orca yokoy de wrote:
> >   
> > > no, it is not a joke.
> > > AT-SPI is not used by all access technologies. 
> > >     
> >
> > Which other access technologies you are talking about?
> >
> >
> > Halim
>
>
> AT-SPI, the Assistive Technology Service Provider Interface, specifies 
> the information that is provided by accessible applications to assistive 
> technologies (and the questions ATs can ask of apps).  Our 
> implementation of AT-SPI uses CORBA for interprocess communication (the 
> AT lives in one process, the app another, so we need some form of 
> interprocess communication).
>
> CORBA is an object based interprocess communication mechanism (the 
> Common Object Request Broker Architecture).  The user interface elements 
> in an applications are represented by 'Accessible' objects, these 
> objects have methods, and CORBA allows an AT to make remote, 
> inter-process method calls on these objects (e.g. to ask an accessible 
> for its name, its role, etc.). 
>
> In order to handle all of the potential issues that can arise with 
> inter-process communication around objects, CORBA is fairly large and 
> complex.  It has to handle the case when the remote object goes away, 
> when a method call fails, etc. etc. 
>
> Memory constrained environments - like the OLCP and the Nokia N800 - 
> don't include CORBA (whereas many desktop systems like Ubuntu and 
> Solaris do).  So, if we are to bring assistive technology support to 
> things like the OLCP and Nokia N800, we need to address this situation.
>
> One idea is to see whether we can slim down the CORBA implementation for 
> OLCP/N800, on the assumption that AT-SPI may not need everything that 
> CORBA provides.  Another idea is to move do a different inter-process 
> communication mechanism (and the candidate choice here is D-BUS, which 
> has roots in DCOP and the KDE desktop). 
>
> The big, not fully answered question, is whether a D-BUS implementation 
> of AT-SPI can do everything we need.  Recent news from Trolltech labs 
> (the folks behind Qt, the main GUI toolkit for KDE) sounds promising on 
> this front, but I believe a little more investigation and testing is 
> needed before we can be sure this will work for us. 
>
> On a related note, I have repeatedly heard the suggestion of "moving to 
> IAccessible2" for UNIX.  To quote the character Inigo Montoya from the 
> movie The Princess Bride, "I do not think that means what you think it 
> means."  IAccessible2 is a port of AT-SPI (or more specifically, the UNO 
> Accessibility API in OpenOffice.org) to Windows.  More precisely, it is 
> a port of those portions of the UNO Accessibility API which weren't 
> already in MSAA (Microsoft Active Accessibility, the fairly simplistic 
> and primitive accessibility API Microsoft introduced in 1997).  Thus, 
> IAccessible2 is not a complete API, but rather is an extension of MSAA.  
> Also, like MSAA, IAccessible2 uses the Microsoft interprocess 
> communication mechanism 'COM' (Component Object Model).  COM doesn't 
> exist on OLPC or N800.  While I believe there are ports of COM to UNIX, 
> nobody I know of is suggesting implementing COM on UNIX an alternative 
> to CORBA for accessibility purposes. 
>
> Because toolkits like GTK+ and Qt have been ported to Windows, and 
> because IAccessible2 is gaining some traction on the Windows platform 
> with JAWS and WindowEyes providing support for it in their screen 
> readers, exposing accessibility information for GTK+ and Qt applications 
> on Windows via IAccessible2 makes a lot of sense.  Since IAccessible2 is 
> derived from the UNO Accessibility API, which itself is expressed in 
> AT-SPI on UNIX, having cross platform apps be accessible on both UNIX 
> and Windows via what is essentially the same API (though different 
> inter-process communication implementation) makes a lot of sense.
>
>
> To the question Halim asked, about what AT supports a D-BUS 
> implementation of AT-SPI, I believe Trolltech labs a fork of Dasher that 
> uses it.  As the GNOME Dasher makes fairly simple and limited use of 
> AT-SPI, this is a natural first AT to test out.  But as it is nowhere as 
> heavy a user of AT-SPI as something like Orca, this port doesn't 
> definitely answer questions about whether we can do everything we need 
> to in a D-BUS based AT-SPI.  I know there are other, KDE AT tools, but I 
> don't think any of them make heavy use of the API either.  All of them 
> pre-date Trolltech's work in this area, and I haven't seen any mention 
> of them being updated.
>
>
> Another important facet to this whole discussion is the question of 
> whether we actually need to fork/port AT to use the D-BUS 
> implementation.  The Accerciser project introduced a Python abstraction 
> layer to CORBA AT-SPI.  Moving our Python-based AT (like Orca) to this 
> abstraction layer would allow us to substitute something else for CORBA 
> (e.g. D-BUS), without needing to fork/port/modify Orca at all.  Orca 
> could use CORBA-based AT-SPI on those platforms where that approach made 
> sense, and something else (e.g. D-BUS) on others, where that was a 
> better choice.  CORBA and AT-SPI have a lot going for them.  They are 
> tested and proven technologies.  It may make sense to stay on CORBA for 
> a while in the desktop world, even as we move to something else in 
> memory constrained environments like OLCP and N800.
>
>
> I hope this helps clear up a lot of the questions and confusion around 
> these topics
>
>
> Regards,
>
> Peter Korn
> Accessibility Architect,
> Sun Microsystems, Inc.
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