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[Bug 13461] Commentary on Issue #30 (longdesc) from the Association of American Publishers

From: <bugzilla@jessica.w3.org>
Date: Mon, 01 Aug 2011 18:49:55 +0000
To: public-html-a11y@w3.org
Message-Id: <E1QnxYp-0003KT-Rz@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=13461

Charles Pritchard <chuck@jumis.com> changed:

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--- Comment #9 from Charles Pritchard <chuck@jumis.com> 2011-08-01 18:49:54 UTC ---
(In reply to comment #8)

> Using a normal link has the benefit that it works for everyone now, does not
> require software upgrades or user retraining, and W3C-WAI are not planning to
> obsolete it. See also RNIB and WebAIM advice:
...
> Are there any scenarios where using a normal link on the image, with
> rel="longdesc" if required, does not provide an immediate, significant
> improvement in accessibility and usability, while still meeting all the
> requirements you listed?

The AAP posting seems to reject the use of anchors:

  * Hiding the link visually would require custom CSS or scripting. The
    mechanism for hiding the link would therefore differ
    product-to-product, making browser extensions or features to show
    the links more complex to code and less reliable for users.  

  * The link would have to be present on the page for screen reader
    users, creating redundancy for those users. 

The AAP seems to be looking for a long-term solution, other than using anchor
tags:

"We urge the W3C HTML Working Group to write out the expected implementation
and user experience details of any proposed replacements for the longdesc
attribute to be sure that they will be at least as effective as the longdesc
attribute in practice."

ARIA markup looks like a viable solution:
"Semantic tagging ... once the W3C's WAI-ARIA specification is further
implemented". (AAP)

>From the ARIA spec:
http://www.w3.org/TR/wai-aria/states_and_properties#aria-flowto
"In the case of one or more IDREFS, user agents or assistive technologies
SHOULD give the user the option of navigating to any of the targeted elements"

Using CSS display none and ARIA flowto may address the issues posted, without
causing visual artifacts, allowing the viewer to chose between the extended
description or typical document flow, without additional anchors.

With the canvas tag, we use non-visible content to represent a description of
the visual media. The img tag does not have a similar option for child nodes
(though the svg image tag does). It's preferable to include alternate content
within the same document. SVG image and HTML canvas avoid longdesc by using the
element subtree.

(long term) Example:

<img aria-flowto="nextParagraph imgDescription" aria-owns="imgDescription"
alt="Pie chart illustrating the reasons people like pie." />
<div aria-label="Analyzing the pie chart" style="display: none"
id="imgDescription">This pie chart is broken up into 9 sections...</div>
<p id="nextParagraph" aria-label="Discussing the pie chart">
Pie is excellent, everyone can see that...</p>

Note: The long description here is not visible to users, as it has the css
display none style applied. This removes it from the rendering tree as well as
diminishing the ability of elements inside of the tree from receiving events.
Image content and long description content is typically static.

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Received on Monday, 1 August 2011 18:49:57 GMT

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