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

Re: Example canvas element use - accessibility concerns

From: Alexander Surkov <surkov.alexander@gmail.com>
Date: Wed, 18 Feb 2009 22:21:04 +0800
Message-ID: <faf3cb2b0902180621t719957a4oc9cba3fe1cc95fe4@mail.gmail.com>
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>
I would guess canvas accessibility problem can be target for expert
handlers group (http://www.linuxfoundation.org/en/Accessibility/Handlers).
They develop plug-able mechanism to allow AT work with specialized
markups. In the case of Bespin we don't have specialized markup
actually, we have JavaScript code. Any way idea of plug-able mechanism
might work here. But it sounds Bespin guys don't care about
accessibility so I'm not sure they will be happy to create specialized
JS classes for AT assuming we have working plug-able mechanism :)

Alex Surkov.


On Wed, Feb 18, 2009 at 8:12 PM, Steven Faulkner
<faulkner.steve@gmail.com> 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.
>
> The current advice on its use and provision of fallback content seems
> somewhat weak given the example of its use in Bespin:
>
> "Authors should not use the canvas element in a document when a more
> suitable element is available. For example, it is inappropriate to use a
> canvas element to render a page heading: if the desired presentation of the
> heading is graphically intense, it should be marked up using appropriate
> elements (typically h1) and then styled using CSS and supporting
> technologies such as XBL.
>
> When authors use the canvas element, they should also provide content that,
> when presented to the user, conveys essentially the same function or purpose
> as the bitmap canvas. This content may be placed as content of the canvas
> element. The contents of the canvas element, if any, are the element's
> fallback content." [1]
>
> 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.
>
> [1] http://www.w3.org/TR/html5/the-canvas-element.html#the-canvas-element
>
> --
> with regards
>
> Steve Faulkner
> Technical Director - TPG Europe
> Director - Web Accessibility Tools Consortium
>
> www.paciellogroup.com | www.wat-c.org
> Web Accessibility Toolbar -
> http://www.paciellogroup.com/resources/wat-ie-about.html
>
Received on Wednesday, 18 February 2009 14:21:47 UTC

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