W3C home > Mailing lists > Public > public-html@w3.org > July 2007

Re: handling fallback content for still images

From: Smylers <Smylers@stripey.com>
Date: Thu, 5 Jul 2007 17:11:36 +0100
To: public-html@w3.org
Message-ID: <20070705161136.GI9858@stripey.com>

Ben Boyle writes:

> There is confusion about "fallback". Scenarios (in my mind are):
> 1. fallback for UAs that don't understand HTML 5

That isn't fallback (in the sense in which has been discussed in this
thread); it's backwards compatibility.

> 2. fallback for UAs that don't support a particular plugin/media type
> used within a document
> 3. fallback for accessibility (a need to access alternatives instead
> of the embedded content)

Those are pretty much the same thing.  In a browser I can disable image
support, and so should get the 'alternative' content instead, just the
same as a user-agent that can't display images at all; that may be
because of technological limitations (a text-only browser) or to cope
with human disability (a speaking browser), but the reason for images
not being displayed doesn't make any difference.

What's important is that alternative content is a true alternative to
the missing images.

> I assume all can be served by the same fallback mechanism(s) and this
> may be incorrect?

Given they want different things, that isn't a valid assumption to make:
for the backwards compatibility case what we need is not for an HTML5
image to be replaced by its alternative content, but by an <img> element
as understood by current browsers.

> Another case is not a fallback, but dealing with related content in
> the page (and a way to express the semantics of that relationship
> through markup), figure/legend is an example of this,

That is definitely not alternative content.  It's a good problem to
solve, but it's a different one.

> It is at the author's discretion which method is best, for example,
> whether I should use alt="Portrait of George Washington" or alt=""
> because there is a heading/caption (i.e. context) that already
> clarifies this.

That example you gave is not really at the author's discretion.  You
state two different scenarios, each of which require different
alternative text.  The difference in the alternatives is because of the
differing scenarios, not on the author's whim; it would be incorrect for
an author to use them the other way round.

Received on Thursday, 5 July 2007 16:11:48 UTC

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