W3C home > Mailing lists > Public > public-html@w3.org > July 2011

Re: hit testing and retained graphics

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Thu, 7 Jul 2011 10:46:52 -0700
Message-ID: <CAAWBYDDXOjOxZ+YQzXN26FxHK51yjGfjnPUbS-H0h3jicJiveQ@mail.gmail.com>
To: Charles Pritchard <chuck@jumis.com>
Cc: Doug Schepers <schepers@w3.org>, Steve Faulkner <faulkner.steve@gmail.com>, Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>, Henri Sivonen <hsivonen@iki.fi>, Sean Hayes <Sean.Hayes@microsoft.com>, "E.J. Zufelt" <everett@zufelt.ca>, Paul Bakaus <pbakaus@zynga.com>, John Foliot <jfoliot@stanford.edu>, Charles McCathieNevile <chaals@opera.com>, Richard Schwerdtfeger <schwer@us.ibm.com>, Cameron McCormack <cam@mcc.id.au>, Cynthia Shelly <cyns@microsoft.com>, "david.bolter@gmail.com" <david.bolter@gmail.com>, Frank Olivier <Frank.Olivier@microsoft.com>, "Mike@w3.org" <Mike@w3.org>, "public-canvas-api@w3.org" <public-canvas-api@w3.org>, "public-html@w3.org" <public-html@w3.org>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
On Thu, Jul 7, 2011 at 10:38 AM, Charles Pritchard <chuck@jumis.com> wrote:
> On 7/7/2011 10:07 AM, Doug Schepers wrote:
>> 1) Make AT that is is "smart" enough to identify an important shape, zoom
>> in on it, and track it if it is moving (this seems like a hard problem, but
>> wouldn't need any changes to specs);
> As rendering engines push more into the graphics card, ATs have less
> opportunity to apply direct heuristics to the screen.
> Also, these are computing devices; forcing vision recognition for virtual
> components is a last resort. It's slow, too.

Agreed that image recognition is not a solution we should care about
right now, given that it's an AI-hard problem.  Given sufficient
hardware and software increases, though, it will arrive as a useful
solution eventually (and will, eventually, solve *all* accessibility
problems).  ^_^

>> 2) Make the shape, size, and position information available through a
>> special accessibility API, updated and maintained in parallel to changes to
>> the rendered shape;
> This API already exists (with shape as an exception); it's the accessibility
> tree and its implemented by most vendors as a separate
> tree which is updated when changes are made to the DOM tree.

This is incorrect.  Size and position are *not* drawn from the
accessibility subtree.  All three pieces of information that Doug
listed have to be explicitly indicated by the author in your proposal.

(I could see a solution where this isn't the case, and the DOM
actually *does* act as a form of scene graph, but that probably
requires a new context to be written.  It's also remarkably similar to
Doug's proposal to put Canvas in SVG.)

Received on Thursday, 7 July 2011 17:47:40 UTC

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