Re: Proposal: enable accessibility by default for GNOME

[David Bolter <david bolter utoronto ca>]

Thanks for the quick metrics Mark, they are helpful.

Nice to see no extra CPU load... and RAM is cheap and users are 
priceless, and we aren't talking about a lot of extra RAM it seems.

cheers,
David
Mark Doffman wrote:
> Hi everyone,
>
> Rob Taylor wrote:
> > Hmm, my take here is that the current AT-SPI is possibly a little too 
> > heavy to enable by default. I'd suggest we look at enabling a11y by 
> > default when the new AT-SPI DBus is ready (2.26 at current estimations)
>
> I'll take my best guess about what happens when a11y is turned on:
>
> 1. The atspi registry daemon needs to be running.
>
> 'top' has the data memory usage at 550kb and the code size at 40kb. The
> cpu utilization is exactly zero.
>
> 2. All gtk applications are going to load accessibility modules.
>
> I'm not sure which modules are going to be loaded. I would say libgail
> and libatk-bridge (including libspi). Perhaps not gail, isn't it now 
> included in gtk? Are liborbit and libbonobo loaded for other reasons 
> on gtk_init?
>
> So the test program:
>
> int main(int argc, char* argv[])
> {
>     gtk_init(&argc, &argv);
>     gtk_main();
> }
>
> It uses 15464kb virtual memory and 596kb of data when accessibility is 
> turned on.
>
> When accessibility is turned off it uses 13660kb of total virtual 
> memory and 456kb of data.
>
> So there is 150kb odd of data initializing the atk-bridge and libspi.
>
> 3. Accessible objects are created for gtk widgets / other UI elements.
>
> Finding how an ATK object is created feels very much like jumping down 
> a rabbit hole. In the end though Gail objects and Bonobo servants are 
> only created on-demand. This means that there will be very little 
> additional memory usage if accessibility is turned on but not accessed.
>
> This is the important part really. Bonobo servants might be very 
> large, and this, I think, is where ORBit/Bonobo gets its reputation 
> for being heavy. However, if a11y goes unused there shouldn't be any 
> created.
>
> > I've cc'd Mark Doffman for his imput as he's probably got the most 
> > experience profiling current AT-SPI behaviour.
> >
> > Rob
> >
> > Willie Walker wrote:
> > > The way accessibility support works is that GTK+ loads accessibility 
> > > modules (gail and atk-bridge) if it detects that accessibility 
> > > support is enabled.
> > >
> > > If accessibility support is not enabled when an application starts, 
> > > I don't believe there is a way to indicate to a running GTK+ 
> > > application to go ahead and load the accessibility modules 
> > > retroactively.  As such, one needs to quit running applications and 
> > > restart them in order for changes to the accessibility setting to 
> > > take effect.
> > >
> > > The current user experience is very bad and kind of a Catch 22 
> > > situation: in order to enable accessibility, they often need to use 
> > > assisitve technologies.  In order to use assisitve technologies, 
> > > they often need accessibility enabled.  So, what we do now is tell 
> > > users to find some way to enable accessibility for their session, 
> > > then log out and log back in.  It's really embarrassing as far as 
> > > I'm concerned.
> > >
> > > I'll see if we can dig up some metrics on the costs of enabling 
> > > a11y. If anyone has good suggestions for how to do this and how to 
> > > get numbers that people will trust, I'd like to hear them.  :-)  
> > > Even if the numbers  are not favorable, however, I think I'd still 
> > > argue to turn a11y on by default: it's far easier for someone 
> > > without a disability to turn it off than it is for a person with a 
> > > disability to turn it on.
> > >
> > > Will
> > >
> > > Mathias Hasselmann wrote:
> > > > Am Mittwoch, den 30.07.2008, 13:11 -0400 schrieb Willie Walker:
> > > > > Alexander Jones wrote:
> > > > >  > Isn't this a distro decision?
> > > > >
> > > > > Ultimately, I guess the value for any gconf setting in 
> > > > > schemas/desktop_gnome_interface.schemas can be whatever a distro 
> > > > > wants it to be.  What I'm proposing, however, is that the default 
> > > > > value that we choose for GNOME is that accessibility will be 
> > > > > enabled by default. If distros want to revert this back to 
> > > > > disabling accessibility, I guess it would be their choice.
> > > >
> > > > What is the motivation for enabling accessibility by default?
>
> Anecdotally....
> I have had 'assistive technologies' turned on now for a year. I am not 
> a  user. My fairly modest computer (IBM T43 512mb of ram) hasn't had 
> any difficulties. I haven't seen any detrimental effect.
>
> Having assistive technologies turned off by default is a real hassle 
> for those who need to use it. Having it turned on by default doesn't 
> have much of an effect. For those who want to optimize their desktop 
> turning it off takes exactly 10 seconds.
>
> > > > For the regular user (not handicapped, not a testing engineer) the
> > > > accessibility bridge just consumes resources without providing any
> > > > benefit - AFAIKS.
> > > >
> > > > Why can't accessibility be activated on demand? With D-Bus activation
> > > > we have the platform for enabling such features on demand.
> > > >
> > > > Ciao,
> > > > Mathias
> > > >
> > > >
> > > > ------------------------------------------------------------------------ 
> > > >
> > > >
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>
> Thanks
>
> Mark
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