Last modified: 2012-04-16 09:15:40 UTC

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Bug 26066 - longdesc support for assistive technology
longdesc support for assistive technology
Status: RESOLVED WONTFIX
Product: MediaWiki
Classification: Unclassified
File management (Other open bugs)
unspecified
All All
: Lowest enhancement (vote)
: ---
Assigned To: Nobody - You can work on this!
: accessibility
Depends on:
Blocks:
  Show dependency treegraph
 
Reported: 2010-11-23 04:31 UTC by Rob Burns
Modified: 2012-04-16 09:15 UTC (History)
5 users (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---


Attachments

Description Rob Burns 2010-11-23 04:31:29 UTC
HTML 4.01 provides for a longdesc attribute which accepts a URI linking to a resource or resource fragment for a description of any image embedded in a page. MediaWIki currently requests an image description from editors and provides a link to the overall page about an uploaded image/media resource. However, by providing a longdesc URI to the description itself, this would aid assistive technology in finding the description in a standardized manner.

Simplest fix:
add an id attribute to the meidai file’s description table cell and then add a longdesc attribute to the img element which references just the description fragment.

Better fix:
check for non-empty content of the description cell of the table and include a longdesc attribute on the image only when that description is populated.

The longdesc attribute is not suitable for ornamental images, however for most of the images and media uploaded by editors, the longdesc is suitable and quite appropriate. Especially where the accompanying article might discuss salient features of the image immediately apparent to sighted readers, the longdesc can fill in the missing gaps for visually impaired users or users otherwise unable to load and view the accompanying image (because of their client application’s capabilities, bandwidth limitations ,etc.).

As an example in a Wikipedia article which embeds an image from the WIkiMedia commons (adding the longdesc attribute and the id attribute for fragment reference and indicating added text by wrapping in three asterisks *** ):


<a href="/wiki/File:filename.file-extension" class="image" title="<Title>">
     <img 
              alt="" 
        *** longdesc="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/filename.file-extension/225px-filename.file-extension#description" ***
              src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/filename.file-extension/225px-filename.file-extension" 
              width="225" 
              height="270" />
</a>

Then on the uploaded media page (the id attribute added to the table cell containing the actual description):

<th style="background: #ccf; text-align: right; vertical-align: top; padding-right: 0.4em; width: 15%" id="fileinfotpl_desc">Description
</th>
<td *** id="description" ***>
      <span class="summary" style="display:none"><filename>.<file-extension>
      </span>
      <p>[A user/editor entered description of the subject, and salient visual properties of the image]
       </p>
</td>
Comment 1 Rob Burns 2010-11-23 05:03:11 UTC
sorry, the example longdesc URI should have read:

/wiki/File:filename.file-extension#description

That is it should link to the metadata page corresponding to the image and not the image itself.
Comment 2 Chad H. 2010-11-23 13:22:23 UTC
Hmmm, HTML5 isn't including a longdesc, and I know that's the direction we're heading in. Not really sure if it's worth it since it won't be around much longer anyway. I'd say WONTFIX.

CC'ing Aryeh, he follows this sort of thing usually.
Comment 3 Aryeh Gregor (not reading bugmail, please e-mail directly) 2010-11-23 16:44:55 UTC
HTML5 has made longdesc obsolete and non-conforming:

http://www.whatwg.org/specs/web-apps/current-work/multipage/obsolete.html#attr-iframe-longdesc

The HTML Working Group at the W3C considered the argument according to its Decision Process.  After reviewing the evidence presented, the chairs concluded that longdesc has few good uses and is poorly implemented in practice, so it should not be made conforming again:

http://lists.w3.org/Archives/Public/public-html/2010Aug/att-0112/issue-30-decision.html

We intend to output valid HTML5 moving forward, so we should not support this unless there's a good reason.  In reality, given the state of UA support for longdesc, there is no good reason, so I'm marking WONTFIX.


If you have specific examples of assistive technology that would benefit significantly from longdesc use in some cases, please present that evidence and reopen the bug.  Note that I'm *not* asking for hypotheticals here, I'm asking for a situation in which a significant number of disabled users will *demonstrably* (not just conceivably) benefit from longdesc use.  In the absence of such evidence, I don't think there's any reason to allow it.

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