Re: Please vote on the canvas accessibility proposal

hi ian,

>I don't think there's any evidence of correlation between authors who care
>about conformance and authors who care about AT users. Do you have
>anything to back this up?

note: this concerns not just AT users, it also affects anybody using a
keyboard to navigate the page. Its about providing accessible content.

I provided some examples in this thread of non conforming canvas use i found
canvasdemos.com,
of the 30 or so uses i looked at I found zero intances of conforming uses
and zero instances of accessible fallback. most canavas elements contained
no content (net negative effect of having the adom set would be zero) . The
3 i found with content were not useful, net effect of having adom set on all
as against your idea, would be no worse. If it was not set on only one of
the elements with inappropriate content it would still be a win for users.

do you have any evidence to the contrary?



>The point is that if the author doesn't care about conformance, there's
>the possibility that the author will specify adom="" even if the content
>is inappropriate for ATs, and equally a possibility that the author will
>_not_ specify adom="" even if the content _is_ appropriate for ATs.

how is the probability equal? does any data support that attribute use
follows this pattern of 50% inappropriate use? there is data available to
show that provision of accessible fallback for canvas is pretty much zero.


> So the content should not be available in this case.

The point is that if the author doesn't care about conformance, there's
the possibility that the author will specify adom="" even if the content
is inappropriate for ATs, and equally a possibility that the author will
_not_ specify adom="" even if the content _is_ appropriate for ATs.

>If authors conform to the spec and provide accessible content in the
>canvas subtree, then it follows that the adom="" attribute is redundant,
>since the content will either be empty or useful for ATs.

>So adom="" is either redundant, or possibly inaccurate. What's the point?

how so?

I can foresee instances where the developer provides an accessible
alternative outside of the canvas (currently conforming no?) and wants to
tell users of browsers that don't support canvas that they are missing
something:

<canvas> you cannot see the graph because your browser does not support
canvas </canvas>
<!-- table containing data represented in graph -->


I would consider this case conforming as an accessible alternative is
provided. and the "fallback" provides information to users of browsers that
don't support canvas.

regards
stevef

On 24 February 2010 06:11, Ian Hickson <ian@hixie.ch> wrote:

> On Wed, 24 Feb 2010, Steven Faulkner wrote:
> >
> > if authors ignore the spec it is most likely that any content in the
> > canvas will not be useful in the case where canvas is supported in the
> > browser.
>
> I don't think there's any evidence of correlation between authors who care
> about conformance and authors who care about AT users. Do you have
> anything to back this up?
>
>
> > So the content should not be available in this case.
>
> The point is that if the author doesn't care about conformance, there's
> the possibility that the author will specify adom="" even if the content
> is inappropriate for ATs, and equally a possibility that the author will
> _not_ specify adom="" even if the content _is_ appropriate for ATs.
>
>
> > If authors conform to the spec and provide accessible content in the
> > canvas subtree, then it follows that they will set the adom attribute
> > correctly, otherwise they would not be conforming.
>
> If authors conform to the spec and provide accessible content in the
> canvas subtree, then it follows that the adom="" attribute is redundant,
> since the content will either be empty or useful for ATs.
>
> So adom="" is either redundant, or possibly inaccurate. What's the point?
>
> --
>  Ian Hickson               U+1047E                )\._.,--....,'``.    fL
> http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
> Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
>



-- 
with regards

Steve Faulkner
Technical Director - TPG Europe
Director - Web Accessibility Tools Consortium

www.paciellogroup.com | www.wat-c.org
Web Accessibility Toolbar -
http://www.paciellogroup.com/resources/wat-ie-about.html