Re: CfC: to publish "The picture element" specification as a First Public Working Draft (FPWD)

On Feb 3, at 3:39 PM, Silvia Pfeiffer wrote:

> [- <public-respimg@w3.org>, <public-pua@w3.org> ; posting to multiple lists fragments email threads and is frowned upon]
> 
> On Mon, Feb 4, 2013 at 12:45 AM, Fred Andrews <fredandw@live.com> wrote:
> 
> Section 8 'Adaptive images' of the srcset proposal appears inconsistent with the intent of the proposal.  There are examples using the srcset as a viewport media query to select between images.  Perhaps just remove this section.
>  
> I agree that this section should be modified to accommodate the use of `srcset` with `<picture>`.
> 
> 
> What I am hearing from the discussions is that the 'srcset' and the <picture> proposal are not alternatives but work best in combination. Is this correct?

Absolutely. We attempted to clarify the relationship between the two in the `picture` extension specification: http://picture.responsiveimages.org/#relationship-to-srcset

The two syntaxes do share some overlap where `srcset` was later retrofitted with `w` and `h` options, as outlined in Section 8 of the `srcset` document. This syntax is strictly pixel-based, and limited in use as the equivalent of `max-width/height` media queries. For example: this extension to the syntax would require authors seeking image breakpoint parity with a layout specced using em-based `min-width` media queries�a common development practice�to do a great deal of calculation and manual conversion. Perhaps as a result, the `picture` syntax is overwhelmingly preferred by authors for this purpose: http://www.w3.org/community/respimg/2012/05/11/respimg-proposal/

Also, were this overlapping syntax removed from the `srcset` extension specification the markup pattern would very closely match CSS� `image-set` function ( http://lists.w3.org/Archives/Public/www-style/2012Feb/1103.html ), and I think there�s real value to maintaining that sort of cross-concern parity: media queries for �size� heuristics, and `srcset`/`image-set` for resolution heuristics.

> If so, I would suggest the authors of both specifications to get together and write a single extension specification that includes the motivation for responsive image design, explains both approaches, their specifications, and examples on when to use what. As a Web author and browser developer I'd much prefer dealing with a single document for responsive images than two or now even three.
> 
> If this is not possible, I'd like to know the reasons. Thanks.

While they do serve to address a number of use cases in combination, the markup patterns can be used independent of one another�`srcset` for simple resolution switching on an `img` tag, or a `picture` element with `source` elements using `src` strictly to determine the appropriate image source for the �art direction� use case. I don�t feel it�s entirely inappropriate for the documents to remain separate where they can function independent of one another, but I�m certainly not opposed to the idea.

Merging the two specifications has been one of the the RICG�s goals for some time now. I�d be very happy to work towards those ends, though I would propose that the scope of the `srcset` attribute be reduced to a set of resolution heuristics as a part of that effort. I want to stress that this does represent the consensus of the Community Group, rather than simply my own opinions on the matter.

I do know that maintaining parity with the `srcset` as specced by the WHATWG is likely a concern, but I�d be more than happy to discuss merging the extension specifications further if the editor of the `srcset` doc is amenable to the idea. A native solution to the laundry-list of �responsive images� concerns is long overdue, but I�m confident that the end is in sight.

Thanks,
Mat Marquis