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Re: implementing Canvas to assure accessibility

From: Olaf Drümmer <olaf@druemmer.com>
Date: Mon, 10 Mar 2014 11:25:22 +0100
Cc: Olaf Drümmer <olaf@druemmer.com>
Message-Id: <DFC80A90-5E4F-474E-AD56-E16F5923C3B4@druemmer.com>
To: Jennifer Sutton <jsuttondc@gmail.com>, w3c WAI List <w3c-wai-ig@w3.org>
My interpretation of the canvas feature is as follows:
- it has been invented for painting, not for representing content structure
- some of the use cases are speed optimised, low memory/CPU footprint painting for games or animations
- someone who is into content structure will feel more at home relying on SVG, which is also a full class citizen of HTML5
- probably SVG just wasn't fast enough or low enough on memory or CPU footprint for certain use cases, so canvas was invented
- re-injecting representation of content structure (whether for accessibility purposes or other reasons) into canvas probably will also reintroduce many of the problems canvas was invented to solve


Am 10 Mar 2014 um 04:34 schrieb Jennifer Sutton <jsuttondc@gmail.com>:

> Greetings, WAI-IG:
> I posted a message similar to this one to the WebAIM list on February 27, but I didn't receive any answers to the thread:
> http://webaim.org/discussion/mail_thread?thread=6335
> So, I'm slightly modifying my message and posting here, in hopes of gathering input.
> I'm wondering if involved parties could offer the list an update on Canvas accessibility. One of Steve's recent tweets, pasted below my name, suggests that there's progress .
> What I'd welcome is an update on the application of/implications for the use of Canvas, with respect to accessibility, in the real world, right now. I'm working with a client who's implementing it, and I need to provide guidance to assure both that the Canvas implementation can be made as accessible as possible (not just to screen reader users, of course). And I want to provide guidance about fallback techniques.
> Questions that are crossing my mind include:
> -- If Canvas is implemented to create an image, but the raw data is still available, will that raw data suffice, in terms of accessibility? I would think some kind of textual description would be valuable to all, including anyone using an older browser that might not support Canvas.
> -- Are there any Canvas-generating libraries that are particularly focusing on assuring accessibility?
> -- What is the best source of accessible examples?
> Thanks.
> Best,
> Jennifer
> @stevefaulkner tweeted:
> HTML5 <canvas> hit Region and focus ring details and example http://t.co/WxhkuSN4TD
> Wednesday, February 26, 2014 at 9:14:40 AM
> http://twitter.com/stevefaulkner/status/438723805067096066
Received on Monday, 10 March 2014 10:25:49 UTC

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