Firefox 14: image long description via link using aria-describedby

In his latest article Mozilla accessibility engineer Alexander Surkov describes an interesting implementation development in FireFox 14, which is a possible solution using ARIA to provide a link to a long description on an image:

Using aria-describedby to provide a long description link on an image

ARIA aria-describedby attribute used on HTML image element and pointing to HTML a element makes the image accessible to expose showlongdesc action. This action opens an URL provided by @href attribute on HTML a element in a new window.

When the image has focus the screen reader user can press enter to activate the link, because a link action showlongdesc is exposed on the image, it uses the URL from the link referenced via aria-describedby.

code:

Note: example from the test page.

<figure>
<img src="shalott.jpg" aria-describedby="a" alt="Painting of a  young woman with long hair, sitting in a wooden boat.">
<figcaption>
A painting inspired by Alfred Tennyson's poem The Lady of Shalott.
</figcaption>
<p><a id="a" href="http://www.tate.org.uk/art/artworks/waterhouse-the-lady-of-shalott-n01543/text-summary">Further information about the painting.</a></p>
</figure>

Notes:

• This is an experimental implementaion only I DO NOT suggest anyone uses this method for anything other than testing.
• Only works in FireFox 14+
• Although the accessible action is exposed and can be activated from the image when using a screen reader (when virtual focus is on the image, pressing enter will open the link), there is no indication to user that the link can be activated from the image.
• From initial discussions with implementers and stakeholders, they are not keen this implementation
• Still works when the link is hidden using the HTML5 hidden attribute or CSS display:none
• Has the same UI issue as current longdesc attribute implementations: The link always opens in a new window/tab.
• test page