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

RE: Example canvas element use - accessibility concerns

From: Ian Hickson <ian@hixie.ch>
Date: Sat, 21 Feb 2009 00:13:17 +0000 (UTC)
To: "John Foliot - WATS.ca" <foliot@wats.ca>
Cc: 'HTML WG' <public-html@w3.org>, 'W3C WAI-XTECH' <wai-xtech@w3.org>
Message-ID: <Pine.LNX.4.62.0902202350480.6186@hixie.dreamhostps.com>
On Fri, 20 Feb 2009, John Foliot - WATS.ca wrote:
> Let's look at Ian's short novel shall we?  He makes all kinds of 
> recommendations on how to use @alt, but I wonder, how much actual 
> user-feedback was solicited before he presumed to tell all and sundry 
> how best to use @alt.  Ian suggests:
> "...<img src="images/parsing-model-overview.png" alt="The network passes 
> data to the Tokeniser stage, which passes data to the Tree Construction 
> stage. From there, data goes to both the DOM and to Script Execution. 
> Script Execution is linked to the DOM, and, using document.write(), 
> passes data to the Tokeniser.">..."
> For real?  Hands up on this list - how many blind users really want that 
> much data as part of their alt text?
> *Real* user research suggests exactly the opposite:
> 	"In general, those with disabilities, those that use a screen 
> reader more, and those with higher screen reader proficiency all tended 
> to prefer the more brief alternative texts more than those with no 
> disabilities, less frequent use, and lower proficiency." 

The bit you're quoting here is about images that show logos, not about 
images showing detailed diagrams. The spec does in fact supports what you 
say for logos:

# If the logo is being used to represent the entity, e.g. as a page 
# header, the alt attribute must contain the name of the entity being 
# represented by the logo. The alt attribute must not contain text like 
# the word "logo", as it is not the fact that it is a logo that is being 
# conveyed, it's the entity itself.

There doesn't seem to be anything in the survey regarding how to handle 
images that convey complicated concepts in the form of diagrams not 
otherwise represented in the text.

> http://webaim.org/projects/screenreadersurvey/#images

This is awesome data, thanks for the link. I'll make sure to study this 
carefully and see if anything in the spec should be updated based on it.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Saturday, 21 February 2009 00:13:56 UTC

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