Re: suggestions for new roles and properties in ARIA next

James Craig, Wed, 20 Apr 2011 17:13:50 -0700:
> On Apr 20, 2011, at 4:43 PM, Leif Halvard Silli wrote:

> No. @title applies to every role in HTML. See text alt computation rule 2D.
> http://www.w3.org/TR/wai-aria/roles#textalternativecomputation
> 
>> If @alt is *fallback* (in addition to alternative text), then the @alt 
>> does not disappear just because the element gets another role. And 
>> HTML5's current definition of @alt is that it *is* fallback. (This was 
>> just changed in a Desision, which states that the @alt text is 
>> alternative text. However it is clear that it is technically fallback 
>> and semantically alternative text.)
> 
> I think that's probably acceptable then.

So seems we agree about this, then. :-) 

Should ARIA say that @alt is also global in nature, even if it is 
invalid on most elements? Remember that it also exists on <area>. When 
I did some tests last year, it seemed as if one could add @alt on any 
element, and them most ARIA supporting AT would pick that up. (Clearly, 
per HTML5's definition, @alt is only fallback in the elements where it 
is permitted.)

> Here's the relevant part 
> from the text alt computation (rule 2A bullet 3).
> 
>> From the spec:
>>> If aria-labelledby and aria-label are both empty or undefined, and 
>>> if the element is not marked as presentational 
>>> (role="presentation"), check for the presence of an equivalent host 
>>> language attribute or element for associating a label, and use 
>>> those mechanisms to determine a text alternative. For example, in 
>>> HTML, the img element's alt attribute defines a label string and 
>>> the label element references the form element it labels. See How to 
>>> Specify Alternate Text ([HTML], section 13.8) and HTML 5 
>>> Requirements for providing text to act as an alternative for 
>>> images([HTML5], section 4.8.1.1).

I don't quite grok whether that rule supports what we agree about ... 

It was always a problem for me to understand the place of @alt in ARIA. 
Because, ARIA describes @alt more or less as @aria-label. But it is 
also clear (but not clear from ARIA) that @alt has features that 
@aria-label don't have (the most important being that it is fallback).

> There are a few places this does not apply though. For example:
> 
> An HTML 5 image:
> <img alt="This is valid fallback content, which is used as the label.">
> 
> An ARIA presentational element:
> <img role="presentation" alt="This is invalid fallback content">
> 
> The second would be considered an author error. 

Basically, yes.

>> VoiceOver IMO support this interpretation. Just run the following Test 
>> 1 and Test 2 in VoiceOver:
>> 
>> 	<p>Test 1: <img src="x.jpg" aria-labelledby="y" >
>> 	<img src="y.jpg" id="y" alt="Y, y, y?" >
>> 	<p>Test 2: <img src="x.jpg" aria-labelledby="yy" >
>> 	<img src="y.jpg" id="y" aria-label="Therfore!" >
>> 
>> You will see that for Test 1, then the first image takes is label from 
>> the second image's @alt text. But in Test 2, this does not happen.
> 
> I think you have some errors in that example.
> 
> 1. The role has not been overridden, so I don't see the relevance.

Relevance: The tests were only meant to demonstrate that @alt is 
technically fallback content. So, in Test 1, if you replace the second 
img element with a <object> element with the same @id value, then the 
fallback of <object> will be used.

> 2. The reason example #2 doesn't work is because you are using a 
> IDREF 'yy' that does not exist in the DOM.

Sorry. Just correct the @id value (or the idref in @aria-labelledby), 
and you will see that it works as I said.
-- 
leif halvard silli

Received on Thursday, 21 April 2011 01:23:30 UTC