Re: aria-describedby and visibility, what is the expected spec behavior?

Bryan wrote:

> Hi Birkir, you can control the association by not setting 
> aria-describedby until the error is made visible, then when focus is 
> set to the field after this, it will be announced.
>

What Bryan said.

Furthermore, aria-describedby is intended to provide a good description 
of the associated form field.  Setting that description permanently to 
"invalid field" is not a good description.  In fact, it's a false 
description when the field is valid.  That's an author error.  It's 
analogous to setting aria-invalid="true" on the field and never changing 
it, regardless of the contents of the field. (Aside:  authors should be 
using aria-invalid as well in the scenario described).

Steve wrote:
> yes, refer to section 5.6.1.3. Text Alternative Computation of the 
> ARIA implementation guide: 
> http://www.w3.org/WAI/PF/aria-implementation/#mapping_additional_nd
>
>
>     Skip hidden elements unless the author specifies to use them via
>     an |aria-labelledby| or |aria-describedby| being used in the
>     current computation. By default, users of assistive technologies
>     won't receive the hidden information, but an author will be able
>     to explicitly override that and include the hidden text
>     alternative as part of the label string sent to the accessibility API.
>

A use case is where aria-describedby references a tooltip.  The 
visibility of the tooltip varies over time -- it pops up and vanishes 
depending on what the user does. Nonetheless, the tooltip text remains 
the same, and is available to the user/AT via the accessibility API.  In 
general, the visibility of a description is orthogonal to that 
description's text.

Aside:  Recently, FireFox added support for a "description-changed" 
event when description text changes [1].  That event is part of the 
accessibility API (e.g, IA2, ATK).  Going forward, these events are 
useful in situations where a description changes, including those that 
depend on the validity of a form field, and the description is 
referenced using aria-describedby.

Hope that helps.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=991969

-- 
;;;;joseph.


'A: After all, it isn't rocket science.'
'K: Right. It's merely computer science.'
              - J. D. Klaun -

Received on Monday, 21 April 2014 14:59:04 UTC