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Re: Agenda: HTML 5 Canvas Accessibility Meeting February 22, 2010

From: Richard Schwerdtfeger <schwer@us.ibm.com>
Date: Sun, 21 Feb 2010 10:14:10 -0600
To: James Craig <jcraig@apple.com>
Cc: Charles McCathieNevile <chaals@opera.com>, cooper@w3.org, cyns@exchange.microsoft.com, David Bolter <david.bolter@gmail.com>, Steven Faulkner <faulkner.steve@gmail.com>, Frank Olivier <franko@microsoft.com>, janina@rednote.net, "public-canvas-api@w3.org" <public-canvas-api@w3.org>, public-canvas-api-request@w3.org, surkov.alexander@gmail.com
Message-ID: <OF3253C46E.C057568A-ON862576D1.0055DDED-862576D1.0059301F@us.ibm.com>

HTML <canvas> content should be accessible too. However, I can think of
none on the web that are today. Your statement of partially inaccessible is
makes no sense either technically or logically based on what has been
implemented for <canvas> to date.

The purpose of the adom attribute is not an accessibility compliance
statement "flag." It is a indication to the browser to map what is in the
subtree to the accessibility subtree to the accessibility infrastructure
and to include it in the keyboard navigation tree. The subtree, today, is
not designed to do that. It is basically ignored a browser unless it does
not support canvas. Setting the flag is not a guarantee that the author has
done a good job any more than anything else that is out there today. That
is what accessibility test tools are for.

The reality is that you should not map the subtree DOM to the accessibility
API and include it in the navigation order, by default, because neither the
AT, an accessibility test tool, nor the user have any way of knowing the
purpose of that content. As for Ian's content about the content being
non-conforming there is no restrictions on what the fallback content is
today. It can be anything. Cynthia made a very important point at one of
the previous meetings in that an accessibility test tool need to know the
content in the sub-tree is directly related to the visual rendering to test
it. That cannot be known unless the author indicates it is.

There are authors that do not care about meeting accessibility criteria and
our making a blind assumption that the author should care to do so would be
irresponsible on our part. Without the attribute you would have to REQUIRE
that the author make the structure and accessibility properties exactly
match what you are rendering on the canvas in all instances. That is an
unrealistic expectation of authors and creates an unmanageable situation
for accessibility test tools. We would also create a situation where two
people sitting down with a web page application (one sighted and one not)
will try to operate a web page application and the solution the blind user
has access to will have absolutely no correlation to the one being rendered
on canvas keyboard-wise, semantically, etc. It may be an entirely different
collection of components, which the neither user cannot see and behaves
nothing like the visual rendering.

I am sorry James, but the argument you present holds no water to me and I
see no way of us ever reaching consensus on it.


Rich Schwerdtfeger
Distinguished Engineer, SWG Accessibility Architect/Strategist

             James Craig                                                   
             >                                                          To 
             Sent by:                  Richard                             
             public-canvas-api         Schwerdtfeger/Austin/IBM@IBMUS      
             -request@w3.org                                            cc 
                                       David Bolter                        
             02/19/2010 08:17          cooper@w3.org, janina@rednote.net,  
             PM                        Charles McCathieNevile              
                                       cyns@exchange.microsoft.com, Steven 
                                       <faulkner.steve@gmail.com>, Frank   
                                       Olivier <franko@microsoft.com>,     
                                       Re: Agenda: HTML 5 Canvas           
                                       Accessibility Meeting February 22,  

I discussed agenda item #2 (@adom) today with Maciej and David, and I've
come to agree with Ian's original argument that canvas contents should just
be accessible by default. Though the idea of using an attribute was
slightly more palatable than an extra element, adding a flag of any kind
doesn't provide much benefit in the best case scenario. In the worst case
scenario, it would render partially accessible content completely


On Feb 19, 2010, at 5:23 PM, Richard Schwerdtfeger wrote:

      Monday, 2010-2-15
      Time: 3:00pm-4:00pm Boston local
      Name: WAI_PFWG(CANVAS)
      Code: 92473 ("WAIPF")
      One time

      irc channel= #html-a11y


      1. Identify Scribe
      2. Final Review for spec. ready adom text for Issue 74

      3. Progress on caret tracking:
      http://www.w3.org/WAI/PF/HTML/track/actions/19 - Steve Faukner

      Rich Schwerdtfeger
      Distinguished Engineer, SWG Accessibility Architect/Strategist

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Received on Sunday, 21 February 2010 16:14:57 UTC

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