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Re: Canvas positioning issue - possible solution (feedback requested).

From: Charles Pritchard <chuck@jumis.com>
Date: Tue, 8 Mar 2011 15:49:26 -0800
Message-Id: <5DD6B095-7B5B-4D30-A7AF-DAC42EBD5500@jumis.com>
Cc: Richard Schwerdtfeger <schwer@us.ibm.com>, "david.bolter@gmail.com" <david.bolter@gmail.com>, "franko@microsoft.com" <franko@microsoft.com>, Maciej Stachowiak <mjs@apple.com>, "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>
To: Dominic Mazzoni <dmazzoni@google.com>
On the other end of things, I'm waiting for feedback from www-dom about adding a touchhover event, to enable focusable based on hit testing to Apple's Mobile Safari AT, VoiceOver.

For setClickable-- we use a second canvas, and assign a semi-random color each time a new path is registered as clickable. It's quite nice in debugging, as each area has a clearly distinct color.

When we get an event, we just look up the pixel data.

As for CSS-- bounding boxes lose a lot of fidelity, and that is an issue with non-rectangular paths. Also, I believe the fallback content should be manageable in a manner that allows it to be accessibly displayed, should the canvas be toggled or otherwise accessed outside its bitmap.

-Charles


On Mar 8, 2011, at 3:37 PM, Dominic Mazzoni <dmazzoni@google.com> wrote:

> On Tue, Mar 8, 2011 at 3:07 PM, Richard Schwerdtfeger <schwer@us.ibm.com> wrote:
>> - If you use CSS you have to do all the coordinate transformations yourself.
> 
> This seems like the best argument to me. It doesn't make sense to
> require developers to try to do this calculation, and plus it means
> that they'd almost certainly have to use code, not static markup
> anyway.
> 
>> we can work on some code. ... as I said nothing is executable yet of course
> 
> Of course...but maybe it could be simulated with a "fake"
> implementation in pure JavaScript that shows what the end result might
> look like visually?
> 
> Even code that doesn't execute would be useful, though.
> 
> - Dominic
> 
Received on Tuesday, 8 March 2011 23:51:04 GMT

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