W3C home > Mailing lists > Public > public-html-a11y@w3.org > March 2012

Re: Drop longdesc, get aria-describedat?

From: Charles McCathieNevile <chaals@opera.com>
Date: Tue, 13 Mar 2012 20:35:08 +0100
To: "Leif Halvard Silli" <xn--mlform-iua@xn--mlform-iua.no>
Cc: "Silvia Pfeiffer" <silviapfeiffer1@gmail.com>, "John Foliot" <john@foliot.ca>, RichardSchwerdtfeger <schwer@us.ibm.com>, "W3C WAI-XTECH" <wai-xtech@w3.org>, "HTMLAccessibility Task Force" <public-html-a11y@w3.org>
Message-ID: <op.wa4jcupowxe0ny@widsith-3.local>
On Tue, 13 Mar 2012 17:44:26 +0100, Leif Halvard Silli  
<xn--mlform-iua@målform.no> wrote:

> Charles McCathieNevile, Tue, 13 Mar 2012 08:08:46 +0100:
>> On Tue, 13 Mar 2012 06:40:48 +0100, Leif Halvard Silli:
>>> One thing that struck me, as I was writing this - at least the things
>>> relating to fallback, is that much of what I was describing probably
>>> only makes sense for the <img> element. Simply because only the <img>
>>> element has a such a specific behavior whenever it isn't displayed.
>> Longdesc isn't default fallback, it is extended support. (Or some
>> such terminology).
> In the bug, then it was Alexey from Webkit who asked if the longdesc
> URL - that is to say: the link, not the content at the end of the link
> - should be rendered visually as a link 'if image loading is disabled'.
> I thought that sounded like a great idea, and hence I said 'yes' to
> that. Why would that be a bad idea?

It isn't, a priori, it is a further form of "discoverable" and probably a  
good one. (That illustrates the value of not over-constraining the  
behaviour, and expecting progressively better ideas to come from  

  There's a bug for not showing all the alt that our devs are worried about  
fixing because it breaks compatibility by messing the layout around, and  
other browsers don't fix - maybe for the same or other reasons, I don't  

> Note that he had 'disabled image loading' - and not 'rotten image URL'
> - in mind, in case that is important. [There are less concerns when
> image are disabled, one should think.]
> PS: The CSS WG has shown interest for being able to style broken
> images: http://lists.w3.org/Archives/Public/www-style/2012Jan/0168

This would help deal with the above problem.

> PPS: In Opera, if @src points to something that Opera doesn't recognize
> as an image file, then the contextual menu fails to render, and so the
> long description becomes unavailable. Seems like a bug?

Yep, seems like one to me. Did you file it, or should I?

>>> E.g. for <video>, <audio> etc, then there is no guaranteed fallback.
>>> And even if there is fallback, it isn't guaranteed to be a textual
>>> substitute.
>> There's no guarantee that the long explanation of an image is
>> textual, either. (Somewhere there is an example I made with audio, to
>> illustrate a different idea, or think of multi-modal CAPTCHA).
> Right. But that's completely another issue, AFAICT.
> What I had in mind was, that when an image URL is broken, then we know
> what we get: We get the alt text, and in most browsers we also get an
> icon to signal 'lacking image'. For video, if the video URLs are broken
> or the forma is not supported, then -a- we do not get a 'lacking video'
> icon'; -b- we might get flash fallback; -c- we might get a link to
> download the file to the disk. In short: We don't know what we get. And
> so, we cannot, as easily, e.g. decide to render the longdesc URL as a
> link if the video doesn't render, because it might break the fallback.
>>> This, IMO, points towards 'the HTML feature' rather than
>>> 'an ARIA feature'.
>> Right.
> But note that the chairs have asked for *more* justification for why
> the CP ask for why @longdesc is needed specifically for <img>.

That's (subtly) the wrong question. There perhaps should have been more  
justification for why it is needed for images, which doesn't imply it  
isn't needed elsewhere.


Charles 'chaals' McCathieNevile  Opera Software, Standards Group
     je parle français -- hablo español -- jeg kan litt norsk
http://my.opera.com/chaals       Try Opera: http://www.opera.com
Received on Tuesday, 13 March 2012 19:35:57 UTC

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