[Bug 10497] New: What happens to role of <img alt="non-empty"> inside a <figure role="img">?

http://www.w3.org/Bugs/Public/show_bug.cgi?id=10497

           Summary: What happens to role of <img alt="non-empty"> inside a
                    <figure role="img">?
           Product: HTML WG
           Version: unspecified
          Platform: PC
               URL: http://dev.w3.org/html5/spec/content-models#annotation
                    s-for-assistive-technology-products-aria
        OS/Version: All
            Status: NEW
          Keywords: a11y
          Severity: normal
          Priority: P2
         Component: HTML5 spec (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: xn--mlform-iua@xn--mlform-iua.no
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html@w3.org, jonas@sicking.cc
        Depends on: 10066,10483,10485


REQUEST: An <img alt="non-empty" > inside a <figure role="img"> looses its
role="img" and becomes either presentational or simply a "normal" text
container.  

CONSEQUENTLY, for <figure role="img">, then it should be a requirement that
<img> elements that it may contain have role="presentational"/alt="" _or_ that
@aria-labelledby or @aria-describedby is used to point to the <img>, so that
the AT can include the @alt text in its accessible name calculation.

DISCUSSION:

ARIA 1.0 says that the children of an element with role="img" are
presentational. 
http://www.w3.org/TR/wai-aria/roles#img

And presentational elements should be hidden from AT - otherwise it could lead
to duplication of content.
http://www.w3.org/TR/wai-aria/complete#childrenArePresentational

A _possible_ conclusion thus is, that in the following example, then the @alt
text of the <img> should not be presented, as the <img> shoudl be considered
presentational:
<figure role="img">
   <img alt="description">
   <figcaption>caption</figcaption>
</figure>
(Yeah, if we take ARIA 1.0 _very_ literally, then even the <figcaption> should
be treated as presentational.)

At the same time, ARIA gives this code example, where a <div role="img"> has
caption element. Here, the captioning element is not ignored, simply because it
is pointed to via aria-labelledby:
<div role="img" aria-labelledby="caption">
  <img src="example.png" role="presentation" alt="">
  <p id="caption">A visible text caption labeling the image.</p>
</div>
http://www.w3.org/TR/wai-aria/complete#presentation
But what if it had _not_ been pointed to by aria-labelledby? 

Conseptually, @alt must be considered an equivalent to @aria-label, despite
that ARIA 1.0's definition of aria-label draws a link to @title.
http://www.w3.org/TR/wai-aria/complete#aria-label
That said, ARIA _also_ draws a link between @alt and @aria-label:
]] 
If aria-label and aria-labelledby are empty or undefined, check for the
presence of an equivalent host language attribute or element for associating a
label, and use those mechanisms to determine a text alternative. For example,
in HTML, the img element's alt attribute defines a label string and the label
element references the form element it labels.
[[ http://www.w3.org/TR/wai-aria/complete#textalternativecomputation

Thus, the logical conclusion is that <img alt="non-empty"> changes from having
role="img" to simply being a text container element, whenever it is the (only)
child(ren) of a <figure role="img">. In order to make sure that AT presents the
content of the @alt attribute to the user, there should be an @aria-labelledby
or @aria-describedby attribute on the <figure role="img"> element, with a
reference to the <img> element:
]]
    <figure role="img" aria-describedby="photo-1">
            <img 
                       id="photo-1"
                     src="image" 
                      alt="Mom is holding her grandson in here arms.
                              He is smiling at her.
                             Mom sits in her usual chair." >
            <figcaption>Mom with her grandson.</figcaption>
    </figure>
[[
(This example takes for granted that the <figcaption> automatically will be
considerd a caption for the entire <figure role="img"> - bug 10483 )

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Received on Sunday, 29 August 2010 15:04:28 UTC