The following is a test page for Mozilla's attempt to extend the use of ARIA describedby to meet the same types of use cases as longdesc. It requires Firefox 14 and a recent version of JAWS to test. It is not as good as longdesc for at least 3 reasons:
The tests are a copy of Steve Faulkner's test page with slight midifications.
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. sSource: http://asurkov.blogspot.co.uk/2012/05/firefox-14-whats-new-for-at-developers.html
Example 1: WAI ARIA describedby link is visible
Example 2: describedby link target hidden using html5 "hidden" attribute on the <a> element
Example 3: Using Longdesc
Example 1: Using Firefox 14 and JAWS13. When the image gets focus with JAWS the user can press JAWSKEY+ALT+R . When they do so they simply hear "Further information about the painting" which is the link text. The user wouldn't know it is a link because it is not announced as a link... it is announced as flat text even though you can open it as a link, so a user wouldn't know to hit enter to go to the long description page.
When I did hit the "ENTER" key, the long description page opens to a new tab it did not announce a new tab...(this is a Firefox/JAWS bug). So there are three problems (1) it does not announce that the long description is a link (2) It does not announce that a new tab has opened. I would say this is an unannounced change of context. (3) it requires an extra step, the user has to activate describedby, which reads the link text, then they have activate to the link.
It's a poor imitation of Longdesc. It is not well supported, does very similar thing but not as wel. It requires an extra step, and it is a little difficult for the user to return to the original image. They wouldn't know it's opening to a new tab...
Example 2: Placing an HTML5 hidden attribute on the <a> element of the link to the long description causes the link to disappear visually. It is removed from the tab order. But the blind user with JAWS 13 and FF14 gets the same behaviour when they encounter the image as with example one... they can press JAWSKEY+ALT+R to hear the link text announced, they are not informed it is a link which is confusing, but if they hit enter they are taken to the long description page...
Hi David, thanks nice work.One thing to note is that as I understand it JAWS does not make use of the built in Firefox longdesc action(). It looks for longdesc attribute in the DOM. The longdesc() action is exposed the same way for both traditional longdesc and the new describedby feature in Firefox, but when the longdesc attribute is present JAWS intercepts the enter key press and opens the link in the new page. When longdesc is not present, the key press is passed through to Firefox which initiates the page opening. I believe JAWS exhibits this behaviour as its own implementation of longdesc is required since Firefox is the only browser that provides a native action to access the longdesc URL (i.e. lack of implementation in other browsers).