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Re: method for providing programmatically associated long description

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Wed, 25 Aug 2010 18:16:23 +0200
To: Steven Faulkner <faulkner.steve@gmail.com>
Cc: HTMLWG WG <public-html@w3.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-ID: <20100825181623511557.fd0c2b6d@xn--mlform-iua.no>
Steven Faulkner, Wed, 25 Aug 2010 16:07:52 +0100:
> Hi leif,
>  
>> The @coords in your example, in effect, makes the <img> a
>> link, for all users. The intention? Also, it is tedious to have 
>> create those @coords.
>  
> Noparticular intention it was a quickly mosked up example. Besides I 
> do not believe it is a requirement for a programmatically associated 
> long description only to be available for some users is it? I 
> certainly don't read that requirement in WCAG 2.0.

It can be 'in your face' to all users. But what I hinted at was a 
question: is there, in that case, any advantage to using an image map 
compared with wrapping the <img> in a link? To answer myself, I think 
there could be some. See below.
  
> But I am sure if an author wanted to achieve it they could. perhaps a 
> 1px region would do it.

I tried to explain that if you remove @coords, then it is only 
available to screenreader users. And perhaps that is one advantage to 
this method: it makes it possible to have some control over whether it 
is visible to all or just some. 

Some other advantages:

* association, but still separation of the img@alt="alternative text" 
area@alt="longdesc link info text"
* rel="longdesc" although a programmatically associated link, it is not 
programmatically clear that it is a _long description_ link. However, 
if we introduce rel="longdesc", then we would also be able to do <area 
rel="londesc" href="*" alt="a longer explanation">. And thus it would 
be programmatically clear that is a longdesc link.
* probably better supported than @longdesc

Issue: In order to be maximum compatible, some would perhaps like to 
combine this method with longdesc="details.html#table". How well would 
that work? Would the screenreader user hear the same link twice?

> As far as it being tedious creating the co-ordinates, most html code 
> editors provide a GUI for creating image map regions, it took me a 
> few moments to create the one in the example. And what percentage of 
> images require a long description?

I think it is useful to document that one does not need to use @coords 
in order to make it a link only to screenreaders. After all, one of the 
advantages of @longdesc is that is not "in your face" to all users.

>> Why not simply wrap the <img> in an anchor element, then?
>  
> the advantage this has is that it leaves the image alt attribute free 
> for the text alternative for the image, while the area alt labels the 
> link to the longdesc and the link to the longdesc is programmatically 
> associated.

So it seems like we concluded the same way on that particular point. :) 

Just so its 100% clear: I think you have document a useful method that 
is well worth studying and documenting. It probably should go into your 
alternative text spec together with @longdesc. Hence my comments.
-- 
leif halvard silli
Received on Wednesday, 25 August 2010 16:17:06 GMT

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