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Re: You Got Your SVG in my Canvas! Mmm, Delicious! (was: hit testing and retained graphics)

From: Richard Schwerdtfeger <schwer@us.ibm.com>
Date: Wed, 6 Jul 2011 16:54:55 -0500
To: Doug Schepers <schepers@w3.org>
Cc: public-canvas-api@w3.org, public-html-request@w3.org
Message-ID: <OF70A247E0.E11EFDE6-ON862578C5.00781A6B-862578C5.0078625C@us.ibm.com>


I have been giving this some more thought. If we were to overlay SVG
objects over canvas wouldn't we ultimately need to make everything SVG
objects and address things like focus rings on those objects. It I am
concerned that we end up just creating an and SVG applications bound to a
canvas subtree DOM to make it accessible. If we do that we are really just
working on SVG accessibility. Perhaps I am wrong about this but I would
like to hear more.


Rich Schwerdtfeger
CTO Accessibility Software Group

From:	Doug Schepers <schepers@w3.org>
To:	public-canvas-api@w3.org
Date:	06/30/2011 12:01 AM
Subject:	You Got Your SVG in my Canvas! Mmm, Delicious!  (was: hit
            testing  and retained graphics)
Sent by:	public-html-request@w3.org

Hi, Rich-

(Please reply to public-canvas-api... I've BCCed other related lists.)

I agree with others on this list that a retained-mode Canvas API is a
bit of a contradiction, and that SVG is better suited (designed, in
fact) for retained-mode graphics.

I agree with you and others that there should be a way for applications
using Canvas to be made more accessible.

I suggest that rather than adding more retained-mode shape features to
the Canvas API or shadow tree, that we simply allow the SVG and Canvas
to be used more seamlessly together.  The SVG WG has discussed this in
the past, and I think most of them would be open to this idea.

I wrote up some more detailed notes on my blog [1], and I'm interested
in hearing feedback from you and others.

[1] http://schepers.cc/retain-a11y-immediately

Bonus Link: http://www.youtube.com/watch?v=DJLDF6qZUX0 (Do not watch if
you are allergic to peanuts or cheese.)

-Doug Schepers
W3C Staff Contact, SVG, WebApps, Web Events, and Audio WGs

Richard Schwerdtfeger wrote (on 6/17/11 2:41 PM):
> Charles, Frank, Mike,
> I am back from vacation. How far do we need to go with hit testing?
> Right now I am looking at associating a closed draw path with a DOM
> object in the canvas subtree. We would then need to address the routing
> of pointing device input events to the DOM object. The drawing path can
> be used to provide bound information to platform accessibility API.
> Do we need to bind any other drawing properties to the canvas object -
> similar to the way device context's are handled on graphic subsystems
> like Windows?
> Mike, I am including you as before I went on vacation you indicated that
> a number of developers desired this feature and wanted to be involved.
> Rich
> Rich Schwerdtfeger
> CTO Accessibility Software Group

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Received on Wednesday, 6 July 2011 21:55:25 UTC

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