Re: aria-labelledby and recursion

Thanks for the longer explanation! Makes sense now.

On Thu, Apr 30, 2015 at 7:44 AM, Joseph Scheuhammer <clown@alum.mit.edu>
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
>
> --
> ;;;;joseph.
>
> 'Array(16).join("wat" - 1) + " Batman!"'
>            - G. Bernhardt -
>
>
>