[whatwg] Implementation complexity with elements vs an attribute (responsive images)

[Maciej Stachowiak]

On May 12, 2012, at 12:35 PM, Adam Barth <w3c at adambarth.com> wrote:

> On Sat, May 12, 2012 at 11:17 AM, Maciej Stachowiak <mjs at apple.com> wrote:
>> 
>> On May 12, 2012, at 6:28 AM, Mathew Marquis <mat at matmarquis.com> wrote:
>> 
>>> While that information may be available at the time the img tag is parsed, I don’t believe it will be available at the time of prefetching — I’m happy to research this further and report back with citations. I’m sure I don’t have to tell you that “disable prefetching on img tags just in case there are matching sources” is going to be a hard sell to vendors that do prefetch. If we’re left with a solution that fetches the original src before applying any custom source logic, well, we’re no better off than we would be with one of the scores of script-based solutions that have come about in the past year.
>>> 
>>> To your original point, though: as much as you can absolutely make a case that a simpler implementation will benefit developers if inherently more stable, you can’t convince me that `img set` suits the needs of developers as well as `picture`. In fact, even if you were to convince me, it wouldn’t matter. Picture is, for better or worse, what developers want and expect in a “responsive images” element. There’s certainly no shortage of proof of that, on this page alone: http://www.w3.org/community/respimg/2012/05/11/respimg-proposal/ At the moment, the Community Group server seems to be down due to excessive traffic.
>> 
>> The key to making the case for the <picture> element or something like it is to cite use cases. Most of the comments on that blog post just give opinions, without use cases backing them up. A lot more weight will be placed on explanations of *why* developers love something (e.g. it lets them do X where they otherwise couldn't, it lets them do Y more easily, etc) than just testimonials that they love it.
>> 
>> Regards,
>> Maciej
>> 
>> 
>> P.S. Your examples in that blog post are not equivalent. Here are two examples  that I believe would be equivalent for resolution adaptation only, presuming a 600x200 image and a 1200x400 scaled version:
>> 
>> <img src="catface.jpg" alt="A cat's face" srcset="catface at 2x.jpg 2x">
>> 
>> <picture style="width: 600px; width: 200px" id="catface_picture" alt="A cat's face">
>> <source src="catface.jpg">
>> <source src="catface at 2x.jpg" media="min-device-pixel-ratio: 2">
>> <img src="catface.jpg" alt="A cat's face">
>> </picture>
>> 
>> Other than more general verbosity, there are a few other other differences that show up:
>> 
>> 1) The <picture> version has to repeat the alt text.
>> 2) The <picture> version has to repeat the URL to the 1x asset.
>> 3) The <picture> version has to explicitly set a width and height, because it does not have the built-in scaling semantics of srcset and so cannot rely on intrinsic size, since it will end up different between the two images.
>> 4) The <picture> version has to use a specific order, while in the srcset version, order doesn't matter.
> 
> Does the id="catface_picture" attribute play an essential role in this
> example, or is it just extra clutter in the <picture> example?

Extra clutter. I forgot to delete it after I switched that example from using externally declared <style> to a style attribute. Corrected versions:



<img src="catface.jpg" alt="A cat's face" srcset="catface at 2x.jpg 2x">

<picture style="width: 600px; width: 200px" alt="A cat's face">
<source src="catface.jpg">
<source src="catface at 2x.jpg" media="min-device-pixel-ratio: 2">
<img src="catface.jpg" alt="A cat's face">
</picture>