Re: aria-labelledby and recursion

Would anyone be opposed to adding the credit card example to the spec. 
It certainly clarifies a misunderstanding I had.
Or should I simply add a section to the authoring practices about how 
the accessible name calculation works?

Regards,
James

On 4/30/2015 7:44 AM, Joseph Scheuhammer wrote:
> On 2015-04-29 5:55 PM, Dominic Mazzoni wrote:
>> It's clear that we don't have consensus on how to interpret the spec. 
>> Does anyone know what was actually intended?
>
> The interpretation that only the first aria-labelledby is followed is 
> correct.  There is an explanatory example at the end of step 2B, 
> repeated below[1]:
>
>> The following example shows the meaning of the clause "… and the 
>> current node is not already part of an aria-labelledby traversal …" .
>>
>> * element1's accessible name is "hello" because this is a first 
>> traversal of its aria-labelledby, leading to element3.
>> * element2 has no accessible name. The computation involves a first 
>> traversal of its aria-labelledby leading to element1, but element1's 
>> aria-labelledby is not subsequently followed.
>>
>> <element1 id="el1" aria-labelledby="el3" />
>> <element2 id="el2" aria-labelledby="el1" />
>> <element3 id="el3"> hello </element3>
>
> I think the restriction has to do with reverse relationships[2]. Like 
> aria-controls and aria-flowto, aria-labelledby creates a 
> 'label-for/labelled-by' relationship structure in some accessibility 
> APIs (in addition to a name string).  That's simple to do if there are 
> only two accessible nodes in the relationship. But, if aria-labelledby 
> references are followed indefinitely, it's not clear how to create the 
> label-for/labelledby relationship(s). Is there only one such 
> relationship?  Or a flat chain of relationships?  Or is it a 
> many-to-one relationship with one label-for with many labelled-bys?  
> Or, one-to-many and hierarchical?  My head hurts just thinking about 
> how the relationship could be represented.
>
> Also, FWIW, I think it it's simpler for authors if only the first 
> aria-labelledby is followed.  They know what they have to work with, 
> and don't have to worry about indefinitely long chains of 
> aria-labelledbys.
>
> Regarding the credit card 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>
>
> The desired result could be accomplished using @aria-label or @alt on 
> the <img> elements.  Since that doesn't involve following a second 
> aria-labelledby reference, the alternative text of the images is 
> captured by the recursion at step 2B:
>
> <input aria-labelledby="label1">
> <div id="label1">
>   Enter your
>     <img src="visa.png" aria-label="Visa">
>   or
>     <img src="mastercard.png" aria-label="Mastercard">
>   credit card number now.
> </div>
>
> or:
>
> <input aria-labelledby="label1">
> <div id="label1">
>   Enter your
>     <img src="visa.png" alt="Visa">
>   or
>     <img src="mastercard.png" alt="Mastercard">
>   credit card number now.
> </div>
>
> Those work in FireFox.
>
> [1] http://www.w3.org/TR/accname-aam-1.1/#step2B
> [2] 
> http://www.w3.org/TR/core-aam-1.1/#mapping_additional_relations_reverse_relations
>

-- 
Regards, James

Oracle <http://www.oracle.com>
James Nurthen | Principal Engineer, Accessibility
Phone: +1 650 506 6781 <tel:+1%20650%20506%206781> | Mobile: +1 415 987 
1918 <tel:+1%20415%20987%201918> | Video: james.nurthen@oracle.com 
<sip:james.nurthen@oracle.com>
Oracle Corporate Architecture
500 Oracle Parkway | Redwood Cty, CA 94065
Green Oracle <http://www.oracle.com/commitment> Oracle is committed to 
developing practices and products that help protect the environment