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Fw: Canvas Accessibility Next steps

From: Richard Schwerdtfeger <schwer@us.ibm.com>
Date: Tue, 19 Jan 2010 12:40:13 -0700
To: Ian Hickson <ian@hixie.ch>, public-canvas-api@w3.org, HTML WG <public-html@w3.org>, public-html-request@w3.org
Message-ID: <OF7C4FB4EF.E8FD9135-ON862576B0.0069790C-862576B0.006C0DA0@us.ibm.com>


Ian, group,

The canvas subteam for the accessibility task force met this week.

We agree that a shadow DOM used to make the actual canvas drawing directly
accessible (when the user operates directly on the canvas) can support
standard HTML 5 input controls. For some users, direct access to the canvas
is important as we have discussed.

What we also agreed on is that given the broad array of interactive
drawings you can create with canvas that it is not always possible to use a
shadow DOM approach.

This means we MUST provide for alternative content in the area, between the
canvas tags that is reserved as fallback content. We also need a vehicle
for the user to choose the alternative content. The only way to view the
alternative content in HTML is by the browser not supporting the <canvas>
which also means the browser does not support HTML 5.

The current vehicle being employed to choose alternative content in HTML 5,
for accessibility is through CSS Media Queries and yes the provision for
alternative content has benefit to people without disabilities as well.

So, we would like the spec to allow for shadow DOM binding to canvas where
that is possible and for the ability to use CSS Media Queries to choose
alternative content. This means the DOM elements between the <canvas>
</canvas> tags must not be used for fallback content but rather it be used
for content for the accessible binding of a shadow DOM to the canvas
drawing region and for alternative content:

such as:

<canvas>
      <default> /!-- we can chose a different tag name --/
            </devault>
            <visual  css media query properties used to select a particular
alternative modality rendering based on IMS Global Learning Consortium
Access For All content>
            </visual>
            <visual>>
            </visual>
            <audio> /!-- this is a possibility for some users --/
            <audio>
</canvas>

Yes, this requires the addition of a <visual> modality tag. At this point
is agreed upon we are at a stalemate on producing spec. ready content to
address canvas accessibility.

Rich

Rich Schwerdtfeger
Distinguished Engineer, SWG Accessibility Architect/Strategist
----- Forwarded by Richard Schwerdtfeger/Austin/IBM on 01/19/2010 01:12 PM
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             Richard                                                       
             Schwerdtfeger/Aus                                             
             tin/IBM@IBMUS                                              To 
             Sent by:                  Richard                             
             public-canvas-api         Schwerdtfeger/Austin/IBM@IBMUS      
             -request@w3.org                                            cc 
                                       janina@rednote.net, Michael         
                                       Cooper/Austin/IBM@IBMUS,            
             01/18/2010 03:47          mike@w3.org,                        
             PM                        public-canvas-api@w3.org, HTML WG   
                                       <public-html@w3.org>,               
                                       public-html-request@w3.org          
                                                                   Subject 
                                       Re: Minutes: HTML 5 Canvas          
                                       Accessibility Call January 18, 2010 
                                       (text  version)                     
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Text version.

(See attached file: Minutes- Jan18,2010 HTML 5 Canvas Accessibility
Call.txt)


Rich Schwerdtfeger
Distinguished Engineer, SWG Accessibility Architect/Strategist

Inactive hide details for Richard Schwerdtfeger---01/18/2010 03:14:06
PM---http://www.w3.org/2010/01/18-html-a11y-minutes.html Richard
Schwerdtfeger---01/18/2010 03:14:06
PM---http://www.w3.org/2010/01/18-html-a11y-minutes.html - DRAFT -
                                                                           
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                         l-req                                             
                         uest@                                     Subject 
                         w3.or                                             
                         g             Minutes: HTML 5 Canvas              
                                       Accessibility Call                  
                                                                           
                         01/18                                             
                         /2010                                             
                         03:11                                             
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http://www.w3.org/2010/01/18-html-a11y-minutes.html

- DRAFT -
HTML Accessibility Task Force Teleconference
18 Jan 2010


See also: IRC log


Attendees
Present
Regrets
Chair
                        Rich


Scribe
                        davidb
Contents
                        Topics
                                    1. Use of Input controls in a shadow
                                    DOM
                        Summary of Action Items
<trackbot> Date: 18 January 2010


<richardschwerdtfe> Meeting: HTML Canvas Accessibility Caucus


passcode?:


<richardschwerdtfe> 92473


ah finally worked


<richardschwerdtfe>
http://lists.w3.org/Archives/Public/public-canvas-api/2010JanMar/0044.html


<richardschwerdtfe> scribe: davidb


rs: use of input controls in shadow dom


Use of Input controls in a shadow DOM


<richardschwerdtfe> http://www.w3.org/WAI/PF/HTML/track/actions/4


db: not sure about shadow dom


<richardschwerdtfe> david: The concern I have is the amount of resource
that will go into this solution


<richardschwerdtfe> david: Is anyone going to do this


<dbb> sf: devs want to add interaction to canvas


sf: if we combine a solution that happens to make it accessible, then win
win


all: discussion of canvas use cases


rs: pushing on alternative content for tricky cases
... if you can do it via shadow dom great, if not, provide alt content, and
way to select it via media query
... in bespin you have a toolbar, no reason that same toolbar can't be
implemented as html5 toolbar
... in shadow dom as we navigate toolbar we render it on screen via canvas,
but actually have a11y tree populated using html markup (shadow dom)


sf: dave do you see alternatives?


db: i don't have a great answer


all: more discussion of canvas examples


rs: consider subway map
... you need a vehicle to select what version you want
... some people want fallback content rendered
... how does user choose
... any technical reason you couldn't insert interactive controls in
'shadow dom'


db: unsure about how this works if not rendered.


<richardschwerdtfe> db: could move the shadow dom to -5000, -5000


<richardschwerdtfe> sf: yes but then magnifiers will not work


<richardschwerdtfe> db: yes that is the problem


<richardschwerdtfe> db: so focus for users would be on the shadow DOM?


<richardschwerdtfe> rs: yes but rendering would be on the visual canvas


<richardschwerdtfe> db: this is going to require evangelization


<richardschwerdtfe> sf: why?


<richardschwerdtfe> db: what answer I got. I like the canvas API but I
don't like the DOM API


<richardschwerdtfe> db: I thin for people used to working in a toolkit
where they have something like a canvas and they do all themselves then
they are in that mind set.


<richardschwerdtfe> SF: we need to be able to draw a focus rectangle


<richardschwerdtfe> db: for the user interaction is focus and all the event
handlers are on the shadow dom


<richardschwerdtfe> rich: you could have the keyboard and mouse handlers on
the canvas element


<richardschwerdtfe> db: so it is up to the web developer


<richardschwerdtfe> rs: we are not requiring people to do the shadow DOM


sf: some people are concerned about slowing down canvas rendering
... don't see this happening


rs: no


db: what do other browser devs thing?


<richardschwerdtfe> db: this shadow DOM idea does not strike me as
something that has to be spoken in the same breath as canvas


<richardschwerdtfe> http://www.w3.org/WAI/PF/HTML/track/actions/4


db: not 100% sure


<richardschwerdtfe> http://www.w3.org/WAI/PF/HTML/track/actions/5


db: i don't see another way


<Stevef> Canvas Focus management
http://dev.w3.org/html5/2dcontext/Overview.html#focus-management


<Stevef> "When a canvas is interactive, authors should include focusable
elements in the element's fallback content corresponding to each focusable
part of the canvas."


<richardschwerdtfe>
http://lists.w3.org/Archives/Public/public-canvas-api/2010JanMar/0044.html


<Stevef> i don't thinkit is correct now


<richardschwerdtfe> Resolution: Close Action items 4 and 5. Mozilla
supports the use of input controls in the shadow DOM at thi stime


rs: we are going to have situations where we need to choose alt content
... there is no vehicle to choose fallback content


sf: if it is included in the tab order and can be interacted with by any
user, it is no longer 'fallback' is it?
... you might want the canvas or something else to be displayed


rs: i've been looking at use of media queries
... we would essentially be adding additional modality tags
... consider audio and visual tags
... visual with properties xyz
... AT interoperable
... currently html5 spec says you can put content inside canvas tags, and
if browser cannot support canvas, then content would be rendered in its
place
... you need a selection mechanism for rendering. having as fallback
doesn't necessary work.
... if you support the html5 spec, must you support canvas?


sf: yes


db: sorry i gotta go


<Stevef> Canvas Focus management
http://dev.w3.org/html5/2dcontext/Overview.html#focus-management


<richardschwerdtfe> ACTION: SteveF ensure there is a dependency between the
HTML5 specification and the HTML 5 2D Context specification to ensure that
the author has the ability to set the visible focus, for <canvas>, to
ensure that a magnifier may follow the visual focus. This would be driven
by the shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action01]


<trackbot> Sorry, couldn't find user - SteveF


<richardschwerdtfe> ction: member:SteveFf ensure there is a dependency
between the HTML5 specification and the HTML 5 2D Context specification to
ensure that the author has the ability to set the visible focus, for
<canvas>, to ensure that a magnifier may follow the visual focus. This
would be driven by the shadow DOM.


<richardschwerdtfe> ACTION: member:SteveFf ensure there is a dependency
between the HTML5 specification and the HTML 5 2D Context specification to
ensure that the author has the ability to set the visible focus, for
<canvas>, to ensure that a magnifier may follow the visual focus. This
would be driven by the shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action02]


<trackbot> Sorry, bad ACTION syntax


<richardschwerdtfe> ACTION: Stevef ensure there is a dependency between the
HTML5 specification and the HTML 5 2D Context specification to ensure that
the author has the ability to set the visible focus, for <canvas>, to
ensure that a magnifier may follow the visual focus. This would be driven
by the shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action03]


<trackbot> Sorry, couldn't find user - Stevef


<richardschwerdtfe> ACTION: RichS ensure there is a dependency between the
HTML5 specification and the HTML 5 2D Context specification to ensure that
the author has the ability to set the visible focus, for <canvas>, to
ensure that a magnifier may follow the visual focus. This would be driven
by the shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action04]


<trackbot> Sorry, couldn't find user - RichS


<richardschwerdtfe> ACTION: Rich ensure there is a dependency between the
HTML5 specification and the HTML 5 2D Context specification to ensure that
the author has the ability to set the visible focus, for <canvas>, to
ensure that a magnifier may follow the visual focus. This would be driven
by the shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action05]


<trackbot> Created ACTION-12 - Ensure there is a dependency between the
HTML5 specification and the HTML 5 2D Context specification to ensure that
the author has the ability to set the visible focus, for <canvas>, to
ensure that a magnifier may follow the visual focus. This would be driven
by the shadow DOM. [on Richard Schwerdtfeger - due 2010-01-25].


<richardschwerdtfe> made Steve Faulkner the owner


Summary of Action Items
[NEW] ACTION: member:SteveFf ensure there is a dependency between the HTML5
specification and the HTML 5 2D Context specification to ensure that the
author has the ability to set the visible focus, for <canvas>, to ensure
that a magnifier may follow the visual focus. This would be driven by the
shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action02]
[NEW] ACTION: Rich ensure there is a dependency between the HTML5
specification and the HTML 5 2D Context specification to ensure that the
author has the ability to set the visible focus, for <canvas>, to ensure
that a magnifier may follow the visual focus. This would be driven by the
shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action05]
[NEW] ACTION: RichS ensure there is a dependency between the HTML5
specification and the HTML 5 2D Context specification to ensure that the
author has the ability to set the visible focus, for <canvas>, to ensure
that a magnifier may follow the visual focus. This would be driven by the
shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action04]
[NEW] ACTION: SteveF ensure there is a dependency between the HTML5
specification and the HTML 5 2D Context specification to ensure that the
author has the ability to set the visible focus, for <canvas>, to ensure
that a magnifier may follow the visual focus. This would be driven by the
shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action01]
[NEW] ACTION: Stevef ensure there is a dependency between the HTML5
specification and the HTML 5 2D Context specification to ensure that the
author has the ability to set the visible focus, for <canvas>, to ensure
that a magnifier may follow the visual focus. This would be driven by the
shadow DOM. [recorded in
http://www.w3.org/2010/01/18-html-a11y-minutes.html#action03]

[End of minutes] (See attached file: pic15977.gif)(See attached file:
Minutes- Jan18,2010 HTML 5 Canvas Accessibility Call.txt)






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Received on Tuesday, 19 January 2010 19:41:43 GMT

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