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Re: Agenda: March 7, 2011 Canvas Accessibility Working Group

From: Charles Pritchard <chuck@jumis.com>
Date: Wed, 02 Mar 2011 12:42:10 -0800
Message-ID: <4D6EABA2.7010700@jumis.com>
To: public-canvas-api@w3.org
CC: Richard Schwerdtfeger <schwer@us.ibm.com>, franko@microsoft.com, david.bolter@gmail.com, public-html-a11y@w3.org
On 3/1/2011 1:04 PM, Richard Schwerdtfeger wrote:
>
> Agenda: March 7, 2011 Canvas Accessibility Working Group
> Time of meeting is 3:00PM EST, 20:00 UTC, duration is 1 hour
> Zakim Bridge +1.617.761.6200, conference 2119 ("A11Y")
>
> IRC: server: irc.w3.org, port: 6665, channel: #html-a11y.
>
> 1. Strategy for positioning fallback content relative to corresponding
> canvas UI drawing counterparts. Discussion starts here:
> _
> __http://lists.w3.org/Archives/Public/public-html/2011Feb/0443.html_
>

This issue is particularly important for tablet devices/touch devices, 
such as mobile smart phones.
I'm currently exploring iOS accessibility techniques inside Mobile Safari.

It appears that mobile safari a11y treats the canvas as it would an 
image. It's possible (not confirmed)
that it expects an image map.

 From a canvas API perspective, something along the lines of

context. setClickableElement(element)
context. clearClickableElements()

feels like the most natural way to "enable" areas in a canvas context to 
be touchable
on a full screen touch device.


FWIW: It seems that in the existing standard, a device such as an iPhone 
should allow
the user to first focus on the canvas element (which it does), and then 
"flip" that area
over to the fallback content (which nobody does).

I do think there's good reason to consider the fallback content as a 
visual alternative
in future contexts; likely as a display: block; overflow: auto;

<canvas>Usable fallback <button></canvas>

In that situation, it would not be wise to apply CSS to the Canvas 
children unrelated
to their display.

...

I don't have any solid answers for the situation, but I'm glad that I 
have a device
at hand which I can use to test the feasibility of implementation.


-Charles
Received on Wednesday, 2 March 2011 20:42:42 GMT

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