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Re: Improving alt (was handling fallback content for still images)

From: Sander Tekelenburg <st@isoc.nl>
Date: Thu, 5 Jul 2007 20:11:06 +0200
Message-Id: <p06240602c2b2d92b93ad@[192.168.0.102]>
To: <public-html@w3.org>

At 12:32 +0200 UTC, on 2007-07-05, Anne van Kesteren wrote:

[...]

>   1) Changing fundamental parts of HTML in drastic ways is not something
>      I think we should be doing.

Aside: this is hard to argue with when you don't define "drastic" nor argue
*why* you don't think it should be done ;)

>   2) While I agree that it would have been nice if <img alt> was designed
>      better when invented I'm not convinced it's so bad now. All user
>      agents now support it so graceful fallback is no longer relevant and
>      you typically don't need markup fallback.

I think whether all UAs support alt is debatable. Test case:
<http://santek.no-ip.org/~st/tests/altlength/>. (I don't have any special
'accessibility' software available. If those who do provide me with test
results, I'll add them.)

Most UAs treat alt quite differently, and most impementations don't appear to
be exactly useful. No doubt this in part stems from the spec being too vague
about allt text having to be "short". I would imagine that defining a hard
limit would be helpful. Both for UA implementors to know how to comply with
having to make alt available, and for web publishers to know how to  provide
useful alt text.

So I propose to add the following to
<http://www.whatwg.org/specs/web-apps/current-work/multipage/section-embedded.html#alt>

- UAs must make the entire contents of the alt attribute easily discoverable
and available to users when the image is, for whatever reason, not presented.
(For example, UAs may present the alt text in place of the image; or through
a tooltip or in a status bar on hovering the indicator of the missing image;
etc.)
- The maximum length of the alt attribute is n characters. UAs must ignore
the part of alt's conent that exceeds this limit. For longer alternatives
authors must use longdesc.

Obviously n needs to be defined. For backwards compatibility we need to take
into account that tooltips disappear after n seconds (at least in Mac OS X
and Windows). For that reason alone the alt text must be kept short. I'd
think 100 characters, or even less. (Would that number, or that unit, be a
problem with non-latin scripts?)


As to the "rich fallback for images" debate in general, I think that <object>
is the most promising approach still. But that means that until Microsoft
tells us whether it is willing to fix IE's <object> implementation, we're
stuck. Luckily one of our chairs happens to be the top IE guy, so no doubt
he'll not leave us in the dark for long.


-- 
Sander Tekelenburg
The Web Repair Initiative: <http://webrepair.org/>
Received on Thursday, 5 July 2007 18:15:29 UTC

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