[Bug 21565] New: Should it be an error to use @longdesc on presentational images? And/Or should it _affect_ the role of the image?

https://www.w3.org/Bugs/Public/show_bug.cgi?id=21565

            Bug ID: 21565
           Summary: Should it be an error to use @longdesc on
                    presentational images? And/Or should it _affect_ the
                    role of the image?
    Classification: Unclassified
           Product: HTML WG
           Version: unspecified
          Hardware: PC
               URL: http://www.w3.org/TR/2013/WD-html-longdesc-20130312/#l
                    ongdesc
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: HTML Image Description Extension
          Assignee: chaals@yandex-team.ru
          Reporter: xn--mlform-iua@xn--mlform-iua.no
        QA Contact: public-html-bugzilla@w3.org
                CC: public-html-admin@w3.org,
                    xn--mlform-iua@xn--mlform-iua.no

A longdesc is obviously supposed to be used on images that are *not*
presentational. As specced by HTML5, it is the empty @alt="" that affects an
image to be considered presentational. HTML5 does not include @longdesc in its
calculation of whether the image is content or presentation.

QUESTION: So what if an image has empty @alt PLUS @longdesc?
          <img src=src alt="" longdesc="longdesc" />

The answer has two sides: One side is the validity issue. The other issue is
make the image 'non-presentational'.

The simplest thing (in the sense that it doesn't challenge the HTML5 spec, too
much) would be to say that longdesc in that case does not make the image
*non*-presentational *and* to make it an error to include longdesc if the image
is presentational.

On the other side: If an <img> has @usemap, then, in praxis, the presentational
nature of that image is actually ignored. (HTML5 may be wrong/incomplete.) And
it could make sense to say that @usemap - and (for our spec) @longdesc - in
this case overrulse the empty @alt. 

It seems to me that regardless, it should be an validaton error to use longdesc
on images which uses empty alt. If you agree, then the one thing remaining, is
to clarify whether @longdesc should cause the image to be treated as
non-presentational, by UAs and ATs.

Presedence for ignoring longdesc when image is presentational: The @summary
attribute is frequently ignored by AT when the table is deemed to be
presentational.

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Received on Wednesday, 3 April 2013 11:34:11 UTC