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Bug 12587 - AT shouldn't see img@alt="" and img@role=presentation as 100% synonyms
Summary: AT shouldn't see img@alt="" and img@role=presentation as 100% synonyms
Status: RESOLVED INVALID
Alias: None
Product: HTML WG
Classification: Unclassified
Component: HTML a11y APIs (editor: Steve Faulkner, Cynthia Shelly) (show other bugs)
Version: unspecified
Hardware: PC All
: P3 normal
Target Milestone: ---
Assignee: steve faulkner
QA Contact: HTML a11y API spec bugbot
URL: http://www.w3.org/TR/html-aapi/#api-role
Whiteboard:
Keywords: a11y, a11ytf
Depends on:
Blocks:
 
Reported: 2011-05-03 02:36 UTC by Leif Halvard Silli
Modified: 2016-04-07 15:37 UTC (History)
9 users (show)

See Also:


Attachments

Description Leif Halvard Silli 2011-05-03 02:36:15 UTC
The HTML to Platform Accessibility APIs implementation guide requires AT to treat

    <img alt="" src=i> 

as 100% the same as

    <img role=presentation src=i >

But such a change is likely to make many pages less accessible to AT users. Examples:

Example 1:  In this example, VoiceOver will contstruct a link text from the href URL.
<a href="./">
     <img src=i role=presentation title="Lorem Ipsum">
</a>

Example 2: In this example, VoiceOVer will use @title as link text.
<a href="./">
     <img src=i title="Lorem Ipsum">
</a>

Thus, as you can see, by making the empty img@alt="" a synonym for img@role=presentation, the treatment of existing web pages will be affected. 

Another problem of seeing them as 100% synonyms is: who wins if both are present and @alt e.g. is non-empty? If they are not  100% synonyms, then it is easier to see why role=presentation wins.

Also, I believe there is a usecase for images with non-empty @alt text which nevertheless are presentational. (E.g. the @alt text could be purely decorational - to reflect that the image itself  is purely some decorational symbols. )
Comment 1 Leif Halvard Silli 2011-05-03 11:18:26 UTC
Example from the wild: 

Mac OS X told to me to upgrade my printer today. This caused me to find that,
on Apple support pages, the link to call the Apple Support Express Lane is an 
IMG link with a @title attribute in combination with an empty @alt:

<a href="[link]">
   <img src="http://images.apple.com/support/iknow/images/i_call_adv.png" 
               alt="" 
             title="Apple Support Express Lane">
</a>

See the page: http://support.apple.com/kb/HT3669
Comment 2 Leif Halvard Silli 2011-05-03 13:01:31 UTC
Here is the approach which the 'HTML to Platform Accessibility APIs implementation guide' should take:

1. The AT should first run an algoritm to *calculate* whether the IMG
     is presentational or non-presentational
2. If it is non-presentational, AT should select the best text substitute

When it comes to the algorithm to calculate whether IMG is presentational or not, then I have suggested how it should look in my 'Validity map for <img>':

http://lists.w3.org/Archives/Public/public-html/2011Mar/0750

Two examples from that algorithm:

* If IMG has non-empty @title, then AT should consider 
   the IMG as non-presentational,  regardless of @alt's value.
* Ditto if IMG has @aria-labelledby  - regardless of @alt's value.
Comment 3 Martin Kliehm 2011-05-10 15:35:41 UTC
Bug-triage sub-team adding the a11yTF keyword because this issue is already discussed in the TF and related to ongoing work regarding @alt validation.
Comment 4 Charles McCathieNevile 2016-04-07 14:26:51 UTC
With disagreement on how role=presentation should be handled in various cases, on HTML bug triage we agreed that it makes sense to treat these two examples in the same way.
Comment 5 Charles McCathieNevile 2016-04-07 15:37:06 UTC
With disagreement on how role=presentation should be handled in various cases, on HTML bug triage we agreed that it makes sense to treat alt="" and role=presentation in the same way.