Re: Problem with AccName regarding recursively processed nodes

I have always read the computation of Accessible Name and Accessible Description as separate invocations of the algorithm.
I can compute either a description or a name and the same node can be referenced in either calculation.

Aaron? How do the actual implementations actually do this?
________________________________
From: Bryan Garaventa <bryan.garaventa@levelaccess.com>
Sent: Wednesday, February 2, 2022 10:54 AM
To: ARIA <public-aria@w3.org>
Subject: Problem with AccName regarding recursively processed nodes


Hi,

Yesterday I received an issue report about the live algorithm code for AccName that I maintain, and I thought it was a simple bug to fix. In looking at this further though, I’m not so sure, and need some feedback from those here to figure out which it is.



The problem, the following code results in no accessible name, but only a description.



<div id="bob">

<a id="test" href="foo" aria-describedby="bob">Some Text</a>

</div>



If you remove aria-describedby, then it results in an accessible name as expected.



This seems like a simple fix, but it’s not.



The reason why this is complicated is because of the following text in the AccName spec.



Important: Each node<https://www.w3.org/TR/wai-aria-1.2/#dfn-node> in the subtree is consulted only once. If text has been collected from a descendant, but is referenced by another IDREF in some descendant node, then that second, or subsequent, reference is not followed. This is done to avoid infinite loops.



Since the AccName algorithm is linear, the result of it not producing an accessible name is actually correct.



The reason being, the algorithm has to be followed in the steps they are documented.

If either aria-labelledby or aria-describedby is present, the nodes that they reference have to be followed before the other steps that occur afterwards in the algorithm.

As a result, all the nodes that are supposed to be processed if aria-describedby were not present have already been processed because aria-describedby references the same nodes beforehand.

And, as the spec clearly states, you can only process a node once and not during any other iterations within the same process.



So, this is why this code does not result in an accessible name.



My question is, should this be changed, and if so, you should realize that this will impact everything everywhere if it is.



Thanks,

Bryan





Bryan Garaventa

Principal Accessibility Architect

Level Access, Inc.

Bryan.Garaventa@LevelAccess.com<mailto:Bryan.Garaventa@LevelAccess.com>

415.624.2709 (o)

www.LevelAccess.com<http://www.levelaccess.com/>