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Re: img@relaxed CP [was: CfC: Close ISSUE-206: meta-generator by Amicable Resolution]

From: Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>
Date: Sat, 4 Aug 2012 15:29:31 +0100
Message-ID: <CAEhSh3eJLqCDZ5Zq4J2ygU1bi509kgksoGnRAEa1-+pDHDjtZA@mail.gmail.com>
To: Steve Faulkner <faulkner.steve@gmail.com>
Cc: "Michael[tm] Smith" <mike@w3.org>, public-html@w3.org, HTML Accessibility Task Force <public-html-a11y@w3.org>, John Foliot <john@foliot.ca>
On Sat, Aug 4, 2012 at 1:01 PM, Steve Faulkner <faulkner.steve@gmail.com> wrote:
>>The absence of @alt is an unambiguous indication that the image should
>>have a text alternative. Doesn't necessarily mean it's key to
>>understanding the content though.
> While you may disagree, that is what the HTML5 and HTML LS currently
> define it as.

I was talking about what developers can effectively communicate with,
and what UAs can (and do) reasonably assume from, its absence, rather
than merely what the spec says about it, but in any case it agrees
with what I was saying AFAICT:

"If the src attribute is set and the alt attribute is not … The image
might be a key part of the content, and there is no textual equivalent
of the image available."


It says "might be" not "is". This is the correct inference, I feel.

> When an image is the content of a figure element it is not unabiguous
> <figure>
> <img>
> <figcaption>text</figcaption>
> </figure>

Yeah, I take it as read that we are using presence of @alt as a
shorthand for presence of @alt or other (non-repair) source of text

>> User agents (as opposed to linters) have to treat images without @alt
>> with or without the linter flag the same,
> why? currently firefox for example does not display any visible
> indication of an image when it has not alt attribute, why is that
> useful for users who have images disabled?

I'm not saying it is or isn't, though I do think user agents should be
free to render as they see fit.

I doubt a user agent would factor the presence of an attribute such as
@relaxed into its decision to indicate or not indicate the presence of
a particular image without a provided text alternative. In particular,
I doubt user agents which provide configuration for indicating or not
indicating such images (such as VoiceOver which allows users to ask it
to announce all images or only images "with descriptions") would
distinguish <img> and <img relaxed> as distinct categories in their
configuration UI.

Maybe an <img relaxed> would be less likely to be a spacer image. But
I think there are more reliable heuristics for detecting spacer images
than looking for the absence of @relaxed, for example looking at
filename, intrinsic image size, color variance, repetition of the
image, and legacy traits of surrounding code.

In practice, spacer images are rare in new content where you could
treat the absence of @relaxed as a signal. For recent content a bigger
challenge to alerting users to key content is the abuse of CSS
background images to speed loading of content images like news photos
and galleries.

@relaxed is such a weak signal for user agents that I doubt the value
of pushing it into the accessibility APIs, that's all.

Benjamin Hawkes-Lewis
Received on Saturday, 4 August 2012 14:30:20 GMT

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