[whatwg] Fallback for <picture>

[Kornel Lesiński]

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