- From: Tab Atkins Jr. <jackalmage@gmail.com>
- Date: Tue, 21 Aug 2012 13:02:17 -0700
- To: John Mellor <johnme@chromium.org>
- Cc: whatwg@whatwg.org, www-style@w3.org, Edward O'Connor <eoconnor@apple.com>, Mathew Marquis <mat@matmarquis.com>
On Tue, Aug 21, 2012 at 12:31 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote: > On Tue, Aug 21, 2012 at 12:20 PM, John Mellor <johnme@chromium.org> wrote: >> CSS image-set and HTML img srcset are getting their first implementations >> but both APIs have serious shortcomings. We should fix them before it's too >> late: >> >> 1. Neither is of any use for flexibly-sized images. >> 2. srcset isn't as smart/intuitive as image-set. >> 3. image-set is less flexible than srcset. >> >> I'll go through these in turn, in decreasing order of importance (sorry >> about the length, but this is a complex topic and I've tried to avoid >> ambiguity). >> >> (This email is cross-posted to whatwg and www-style, since this is of equal >> relevance to HTML and CSS). >> >> 1. Neither is of any use for flexibly-sized images. > > This is what Media Queries and the similar 'w' and 'h' tokens in > @srcset are for. You can create one pair of 1x/2x images for one size > of screen, and another pair for another size of screen. > > >> 2. srcset not as smart/intuitive as image-set. > > The algorithms are meant to be the same. If you read the HTML > algorithm carefully, you'll notice that, after you've eliminated the > images that violate the 'w' or 'h' constraints, the browser can choose > *any* of the remaining images, based on whatever criteria it wants. > This happens in two places: step 17 is very explicit in saying "UAs > can do what they want"; step 21 is more implicit, as the "nominal > pixel density" is a UA-defined value and can be literally anything. > (There was previously a note in the spec saying this directly, but it > appears to have been removed.) > > Ideally, I'd be able to just refer to the HTML algorithm, but it's far > too specialized for @srcset for me to actually use. Instead, I plan > to include a note pointing to @srcset and indicating that it should be > identical. > > There is currently a behavior difference between HTML and CSS - CSS > currently does fallback to less-good images if the first doesn't load, > while HTML doesn't. I'm going to harmonize the two, either by getting > HTML to do fallback or changing CSS to not do it. > > >> 3. image-set is less flexible than srcset. > > It's not. The extra things that @srcset can do are precisely > identical to just using Media Queries. > > ~TJ
Received on Tuesday, 21 August 2012 20:03:05 UTC