W3C home > Mailing lists > Public > public-html@w3.org > February 2009

Re: Example canvas element use - accessibility concerns

From: Philip Taylor <pjt47@cam.ac.uk>
Date: Wed, 18 Feb 2009 14:52:24 +0000
Message-ID: <499C20A8.2020604@cam.ac.uk>
To: Steven Faulkner <faulkner.steve@gmail.com>
CC: HTML WG <public-html@w3.org>, W3C WAI-XTECH <wai-xtech@w3.org>, Janina Sajka <janina@rednote.net>
Steven Faulkner wrote:
> The recently released code editor Bespin (
> https://bespin.mozilla.com/index.html) is a great example of the utility of
> the canvas element, its also a worrying example of the barriers to
> accessibility its use will produce. It includes editable text, folder lists
> and interactive elements that are all essentially a graphic. there does not
> appear to be a way to extract any usable information to support Assistive
> technology to interpret or provide interaction.
> [...]
> Are there plans to provide mechanisms to add accessibility hooks for content
> produced using canvas? As providing a secondary accessible version of an
> application such as bespin seems like a non starter, and is a prime example
> of the sort of "bolt on" accessibility that HTML5 was trying to move away
> from.

As far as I can tell, the non-bolted-on accessible way to implement 
Bespin would be using HTML (with textarea, contenteditable, etc) and 
CSS, not canvas. Its current use of canvas hurts fully-capable graphical 
browsers too, e.g. I can't copy-and-paste text between Bespin and any 
other application, and I can't edit its text with my OS's usual key 

http://benzilla.galbraiths.org/2009/02/17/bespin-and-canvas/ indicates 
that canvas was chosen because of concerns over the performance and 
controllability of other solutions. It'd be good to see if those 
concerns could be addressed in the long term by changes to the specs or 
by fixing browser bugs, to remove the reasons for inappropriately using 

The main problem I see with adding built-in (as opposed to bolt-on) 
accessibility to canvas is that I can't even begin to imagine any way 
that could ever possibly work at all :-). That may be largely because my 
imagination is limited - I'd be interested in concrete suggestions of 
how it could be done. Otherwise I can't think of anything the spec could 
say to help accessibility here.

Philip Taylor
Received on Wednesday, 18 February 2009 14:53:03 UTC

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