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Content positioning in Canvas fallback content feedback requested

From: Richard Schwerdtfeger <schwer@us.ibm.com>
Date: Fri, 25 Feb 2011 16:23:58 -0600
To: public-html@w3.org
Cc: public-html-a11y@w3.org, franko@microsoft.com, chuck@jumis.com, david.bolter@gmail.com
Message-ID: <OF34770393.BC7AF5AF-ON86257842.0079D00D-86257842.007B0AF5@us.ibm.com>

One of the features that platform accessibility API have is bounding
rectangles associated with accessible objects. Screen magnifiers use this
information to allow the user to zoom to an arbitrary, visual object in
view. AI Squared has asked that we provide this feature for the fallback
content such that fallback content objects can be positioned, with
dimensions relative to where they are drawn on the physical <canvas>.

There are a couple of ways we see this can be done:

- apply shape and coords similar to image maps in fallback content
- Parially, using CSS positioning.

We have wrestling with how best to do this as it is expensive for
developers. We would like to hear what members think would be the preferred
way to address this issue. What would people prefer? Is there an
alternative that would be better?

To produce an accessible canvas there is a one for one correspondence
between elements in fallback content and what is drawn on the canvas, i.e.
if there is a checkbox drawn on canvas there would be an associated
checkbox in fallback content. Now we just need a way to have the fallback
content reflect the position and dimensions as best possible.


Rich Schwerdtfeger
CTO Accessibility Software Group
Received on Friday, 25 February 2011 22:25:57 UTC

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