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Re: A presentational img?

From: James Craig <jcraig@apple.com>
Date: Tue, 10 May 2011 10:54:27 -0700
Cc: W3C WAI-XTECH <wai-xtech@w3.org>
Message-id: <F37BD778-EFF5-4524-918E-0ECDB6547908@apple.com>
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
On May 10, 2011, at 7:16 AM, Leif Halvard Silli wrote:

> as VoiceOver developer and as WAI-ARIA editor,

Well, since you asked it like that: The following opinions are my own and do not necessary represent the views of my employer, nor do they represent group consensus within the ARIA subteam of the PFWG.

> is it in your view 
> correct to treat the following image as non-presentational?
> <img alt="" title="Advicory text" src="i" />
> VoiceOver currently does treat it as non-presentational and reads the 
> @title to the user. Ahis seems correct to do, from my POV. The 
> background for my question is found int Bug 12587 against HTML5. [1] 
> [1] http://www.w3.org/Bugs/Public/show_bug.cgi?id=12587

In my opinion, the presentation state would only apply if one of the following were true:

 the author explicitly provided a role of presentation on the img tag, <img role="presentation">
 the host language labeling mechanism (in this case @alt) equaled an empty string, *AND* the ARIA text alternative computation [1] equaled an empty string.

The ARIA spec does *NOT* limit the ability of assistive technologies to use heuristic to determine the text alternative of an image with missing alternative text. Sometimes these heuristics fall back to image file name substrings on standalone images, or link path substring on linked images. For example, some assistive technologies will determine the following alternative text from the following markup (that is invalid in HTML4 b/c of the missing @alt)

"contact": <img src="contact.png">
"about us": <a href="/path/about_us.html"><img src="contact.png"></a>

Perhaps if the HTML editors were to standardize the heuristic mechanism above, the accessibility advocates in the HTML group would be appeased. As is, it's unacceptable to state that these images are presentational, because it is in the best interest of the spec editors, browser vendors, AT users, and AT vendors to make sure rendering engines provide the most accessible output, even with the worst possible markup:

<img src="asdfhjklafds_gibberish_12347612394786.png">

W3C process requires that, in order for HTML 5 to reach Candidate Recommendation phase, the Working Group will have to prove on each part of the spec, that two rendering engines have implemented the requirement. Despite what is currently in the HTML 5 spec, I don't believe any of the major browser vendors will decrease the accessibility of their rendering engines in order to make <img src="contact.png"> presentational, because it would be a user interface regression.

And again, these opinions are my own and do not necessary represent the views of my employer, nor do they represent group consensus within the ARIA subteam of the PFWG.


1. ARIA text alternative computation: http://www.w3.org/TR/wai-aria/complete#textalternativecomputation
Received on Tuesday, 10 May 2011 17:54:55 UTC

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