Re: aria-labelledby and recursion

My understanding is that it recursively follows aria-labelledby until the 
"current node" either does not have labelledby or the reference became 
circular.
It is not the easiest thing to follow though.

It does say it is recursive in the descriptive text:
"Text alternatives are built up, when appropriate, from all the relevant 
content contained within an element. This is accomplished via steps 2B and 
2F, which are recursive, using the full set of rules to retrieve text from 
its own children or nodes it references."

Matt King
IBM Senior Technical Staff Member
I/T Chief Accessibility Strategist
IBM BT/CIO - Global Workforce and Web Process Enablement 
Phone: (503) 578-2329, Tie line: 731-7398
mattking@us.ibm.com



From:   James Nurthen <james.nurthen@oracle.com>
To:     public-pfwg@w3.org, 
Date:   04/29/2015 11:52 AM
Subject:        Re: aria-labelledby and recursion



My reading has always been that you only don't follow the aria-labelledby 
traversal when the referenced node itself includes aria-labelledby, so for 
your first example the label for the input would be "Label 1" and for your 
2nd it would be "Enter your Visa or Mastercard credit card number now".

I guess if this is causing confusion the language needs to be tidied up - 
perhaps even with some more examples.

Regards,
James

On 4/29/2015 11:44 AM, Dominic Mazzoni wrote:
Is aria-labelledby supposed to be allowed to be used recursively? For 
example: 

<input aria-labelledby="label1">
<div id="label1" aria-labelledby="label2">Label 1</div>
<div id="label2">Label 2</div>

Is the computed name of the input element supposed to be Label 1 or Label 
2? I thought it was supposed to be Label 2, but the spec (
http://www.w3.org/TR/accname-aam-1.1/) says:

"Otherwise, if the current node has a non-empty aria-labelledby attribute, 
and the current node is not already part of an aria-labelledby traversal, 
process its IDREFs in the order they occur:"

That seems to imply that when you're part of an aria-labelledby traversal, 
you stop following the aria-labelledby attribute. Is that true, or is it 
misworded?

Here's an even more subtle example:

<input aria-labelledby="label1">
<div id="label1">
  Enter your
    <img src="visa.png" aria-labelledby="visa">
  or
    <img src="mastercard.png" aria-labelledby="mastercard">
  credit card number now.
</div>
<div hidden id="visa">Visa</div>
<div hidden id="mastercard">Mastercard</div>

I think as a web developer I'd be really surprised if the text for the 
label element itself was "Enter your visa or mastercard credit card number 
now" but the computed label for the input element was "Enter your or 
credit card number now" because aria-labelledby is not allowed to be 
followed recursively.


-- 
Regards, James 

James Nurthen | Principal Engineer, Accessibility
Phone: +1 650 506 6781 | Mobile: +1 415 987 1918 | Video: 
james.nurthen@oracle.com 
Oracle Corporate Architecture
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