Re: Request for advice on <canvas> accessibility

Thank you for this request, Ian.

There is noticeable divide in the accessibility community. On on side,  
you have those screaming, "Feature X isn't accessible. Abolish it." On  
the other side, some would rather have discussions such as, "Feature X  
isn't accessible yet, but it provides obvious benefit to those using  
it. Instead of stifling innovation with futile attempts to abolish a  
useful new feature, let's figure out how to make it work for everyone."

One of the options on the table for WAI-ARIA 2.0 is to discuss new DOM  
methods and other programatic interfaces in addition to the roles,  
states, and properties that exist now. The discussion was tabled for  
WAI-ARIA 1.0 in the interest of completing a 1.0 last call. Content  
attributes are the lowest common denominators for any DOM-compliant  
language (including HTML and SVG) so the PF Working Group decided to  
revisit other programmatic methods in a later version.

I, admittedly, haven't thought about this problem in depth, but it  
seems that canvas (or any DOM element for that matter) could be  
special-cased to allow a programmatic representation of the data  
displayed, along with an any relevant accessibility information and  
interaction methods. I have no ideas for how to make this "automatic"  
like you request, but I'm sure we can come to a reasonable solution  
that would allow accessibility-conscious authors to make their canvas- 
based applications accessible.

Cheers,
James Craig


On Jun 26, 2009, at 3:53 PM, Ian Hickson wrote:

> It has been suggested that the <canvas> feature in HTML5 should have  
> an
> accessibililty solution more thorough that its current solution,  
> which is
> based on the <object> fallback model.
>
> To this end, I would like to look to the W3C WAI groups for guidance  
> on
> this issue.
>
> To help me understand how <canvas> could be made more accessible, I  
> would
> like to work from a concrete example:
>
>   http://www.whatwg.org/issues/data.html
>
> This page uses <canvas> to generate a graph. Could I ask for advice on
> what the best possible way to make this page universally accessible  
> would
> be? I would like to maintain the same visual presentation, but would  
> like
> to make this page accessible to users of ATs.
>
> Could the WAI groups provide sample pages showing how, in an ideal  
> world,
> with whatever APIs or accessibility hooks need to be made available,  
> the
> page could be made accessible, while still maintaining its current  
> dynamic
> generation and visual presentation?
>
> My goal here is to determine what the best APIs and other technical
> solutions would be to provide good accessibility as automatically as
> possible for people using <canvas>. I hope the combined accessibility
> expertise of the WAI groups will be able to design a solution for this
> that we can use in HTML5.
>
> I am at a loss personally as to how to do this. Any help would be  
> greatly
> appreciated on this issue.
>
> Cheers,
> -- 
> Ian Hickson
>