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[Bug 13176] The bounds of canvas fallback content, as rendered on the canvas, are not provided by the user agent to an assistive technology.

From: <bugzilla@jessica.w3.org>
Date: Thu, 11 Aug 2011 22:46:39 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1Qre1P-0000eq-9a@jessica.w3.org>

--- Comment #13 from Charles Pritchard <chuck@jumis.com> 2011-08-11 22:46:37 UTC ---
(In reply to comment #9)
> Wouldn't SVG be the right solution to this? Surely using <canvas> when you are
> expecting a user to interact with the app via a tactile interface rather than
> through sight is just misusing canvas.

One more comment on this, because it occurred to me, that perhaps the WWHATWG
editor does not understand accessibility testing. There is no expectation that
the user will  "interact" via any particular interface, tactile or otherwise.
The purpose is to expose information to the operating system / UA, that's all.
>From there, we certainly test usability, but that's a separate issue for app
developers, not browser vendors.

Further, eyes-free use does not necessarily mean that the user, or other
observers are not looking or able to look at the screen.

Circling back: drawFocusRing is not sufficient for driving screen magnification
nor Apple's VoiceOver. It only works for an element that is in focus, and some
magnification and touch-based interfaces do not send focus-events until after
the user has initiated one. drawFocusRing works for many use cases, and should
be used via onfocus events. It's not adequate for the remaining cases which
rely on IAccessible accLocation and do not trigger focus. By adding a new
method to the canvas api, as we have proposed a setClickableRegion(element),
similar to drawFocusRing, the information can be exposed to the OS / UA, and

I hope that helps. The checkbox example in the WHATWG spec would benefit from
setClickableRegion. Currently, it will-not work on VoiceOver in Mobile Safari.
It would require only one-line, to fix that, if setClickableRegion were

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Received on Thursday, 11 August 2011 22:46:41 UTC

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