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Re: You Got Your SVG in my Canvas! Mmm, Delicious!

From: Charles Pritchard <chuck@jumis.com>
Date: Thu, 30 Jun 2011 13:38:07 -0700
Message-ID: <4E0CDEAF.9050400@jumis.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Richard Schwerdtfeger <schwer@us.ibm.com>, public-canvas-api@w3.org, public-canvas-api-request@w3.org, Doug Schepers <schepers@w3.org>, Paul Bakaus <pbakaus@zynga.com>
On 6/30/2011 10:53 AM, Tab Atkins Jr. wrote:
>> >  3. If you don't want to use hit testing on drawing objects don't add them
>> >  and canvas will in fact route the hit events off the canvas element like it
>> >  does now. If an author never introduces a drawing path that needs to be hit
>> >  tested then
> If you do hit-testing yourself by listening for clicks on the
> <canvas>, users can't use a magnifier to zoom into the active area
> (something you implied was a problem to be solved in the previous
> point).  Thus, this does not satisfy #3,

Magnifier zoom for hit-testing "onclick" is already solved by drawFocusRing,
as the onclick event can / should trigger a focus event on the 
appropriate element.

The issue is enabling magnifier zoom prior to an onclick or focus event.

This issue comes up with ZoomText and with Apple's VoiceOver.

The WHATWG has tried to push things forward with virtual focus; in 
essence, trying to
support active descendant. It's not sufficient, but it was a step 
forward in making a proposal.

There are no AT-side mechanics which would send a "virtual focus" event to
the browser. What they do have, is access to the accessibility tree.

They traverse that tree, find suitable objects (given whatever criteria 
is appropriate
for the context) and then look for bounding box information and/or other 
metadata.

That information needs to be there ahead of time; thus the issue of 
"retained-mode".
Thing is, this is information that's bound to elements, not to "Canvas" 
itself.

In Flash, I would most certainly use their retained mode children, and 
add them
as elements in the subtree (appendChild); but I would still have a normal,
typical, bitmap, powering the canvas.

-Charles
Received on Thursday, 30 June 2011 20:38:50 UTC

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