W3C home > Mailing lists > Public > public-html-a11y@w3.org > February 2010

Re: Please vote on the canvas accessibility proposal

From: Ian Hickson <ian@hixie.ch>
Date: Wed, 24 Feb 2010 22:34:14 +0000 (UTC)
To: Richard Schwerdtfeger <schwer@us.ibm.com>
Cc: public-canvas-api@w3.org, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
Message-ID: <Pine.LNX.4.64.1002242229530.20980@ps20323.dreamhostps.com>
On Wed, 24 Feb 2010, Richard Schwerdtfeger wrote:
> >
> > > It also does not mean it is accessible if you are saying the canvas 
> > > can only act as a bitmap.
> >
> > I don't see how something that "conveys essentially the same function 
> > or purpose", when presented to the user, can be anything _but_ 
> > accessible.
> You are saying that it has the same function as the "bitmap" canvas. I read
> this as having the function of a bitmap.

The bitmap canvas is the image rendered by the <canvas> element in visual 

> Also, fallback content could provide similar function (essentially the 
> same) but that does not mean the same function of the canvas as it is 
> rendered.

Indeed. But we still have to expose it to the user.

> So, if what you are saying is true most or a vast majority of canvas 
> implementations are in non-compliance.

Assuming you mean pages that use <canvas>, and not <canvas> 
implementations, then yes -- most aren't accessible. It's a terrible state 
of affairs, that won't be helped by making it even harder to get 
accessibility right by adding an unintuitive attribute that has to be 
added in order for the fallback content to be accessible.

> img alt is the most simplistic example and only conveys the text 
> equivalent aspect of accessibility. If you know <canvas> behaves like an 
> image or bitmap then that would be a good start. If you go to something 
> like bespin, which is not a bitmap then we have a problem.

Bespin is a great demo, but it's a horrible misuse of <canvas>. 

> Perhaps we are arguing semantics but clearly the current wording has not 
> helped to promote accessible canvas development.

I doubt many authors have read the current wording. Adding attributes that 
make getting this right even more complicated certainly isn't going to 
help matters, IMHO.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Wednesday, 24 February 2010 22:34:46 UTC

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