Syntax used on the wiki:
http://wiki.whatwg.org/wiki/Adaptive_images
places alt on the new element:
<picture alt="alt">
<source …>
<img>
</picture>
I think it can be improved in two ways:
- Instead of having alt on <picture>, it could be on the fallback <img>.
This will give better backward-compatibility.
- Use of an attribute for alternative content is very limiting, e.g. image
of a comic cannot have dialog marked up well. Use of an non-empty element
opens up possibility of richer alternatives.
The processing rules for extracting fallback from <picture> would be:
1. Take all children of <picture>
2. Remove/ignore all <source> elements.
3. Interpret all <img alt=""> elements as their alt text.
<picture>
<source …>
<img alt="This is unstructured fallback">
</picture>
and
<picture>
<source …>
<img>
This is <em>structured</em> fallback
</picture>
The two examples above would have "This is unstructured fallback" and
"This is <em>structured</em> fallback" as their alt, respectively.
A use case for markup in alt:
<picture>
<source
src="world-map-showing-most-popular-browser-in-each-country.png">
<table><tr><th>Country</th><th>Most popular browser</th>...
</picture>
Trying to put all data in alt="" wouldn't work well, and
<img alt="world map showing most popular browser in each country">
doesn't contain the information that the map conveys, so that's at best a
caption, not an alternative.
--
regards, Kornel Lesiński
