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 02:40:27 +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.4.62.0902210230410.6186@hixie.dreamhostps.com>
On Fri, 20 Feb 2009, John Foliot - WATS.ca wrote:
> 
> You were right in your example in illustrating the kind of good, useful 
> textual alternative to an image that should exist, especially in a 
> complex image; your error was in the method of delivery to the end 
> users... not every screen reader user might want to hear that much 
> detail at first pass... Imagine '...a glance at the image' vs. '...a 
> close study of the image' and you kind of get the idea.  We need to 
> actually provide both options!

If the image is actually a _replacement_ for text that otherwise existed, 
why would the user care that the author had made the stylistic choice to 
use an image instead? I don't understand.

Specifically, the example in the spec is talking about an author who has 
something like this:

  <p>In the common case, the data handled by the tokenization stage
  comes from the network, but it can also come from script.</p>
  <p>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.</p>

...and decides to replace the text with an image. Why should there be 
_any_ difference for the non-visual user? What the spec proposes:

  <p>In the common case, the data handled by the tokenization stage
  comes from the network, but it can also come from script.</p>
  <p><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."></p>

...seems like exactly what the user would want. Why should the user who 
doesn't have access to images be affected here?

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Saturday, 21 February 2009 02:41:09 GMT

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