[webkit-dev] The SrcN responsive images proposal

[Dirk Schulze]

On Nov 5, 2013, at 11:18 AM, John Mellor <johnme at chromium.org<mailto:johnme at chromium.org>> wrote:

On Mon, Nov 4, 2013 at 10:19 PM, Ryosuke Niwa <rniwa at webkit.org<mailto:rniwa at webkit.org>> wrote:
99 is a very high upper bound while it would still allow us to implement the optimization we're thinking of.

I'm of the opinion that we should use exactly one attribute for this feature.

The thing is, srcN isn't a list, it's a list of lists. Consider the following srcN for a fixed-width image with art direction:

<img src-1="(min-width: 640px) 0.5x photo at 0.5x.jpg, 1x photo at 1x.jpg, 2x photo at 2x.jpg"
     src-2="0.5x photo-crop at 0.5x.jpg, 1x photo-crop at 1x.jpg, 2x photo-crop at 2x.jpg">

I guess one could combine it all into one attribute, e.g. by introducing "||" as an 3rd separator, in addition to the existing "," and ";". For example:

<img srcset="(min-width: 640px) 0.5x photo at 0.5x.jpg, 1x photo at 1x.jpg, 2x photo at 2x.jpg || 0.5x photo-crop at 0.5x.jpg, 1x photo-crop at 1x.jpg, 2x photo-crop at 2x.jpg”>

I assume authors would just create a new line for each list. That is basically what you do with src-1 and src-2 as well in your example. Writing both beyond each other wouldn’t be very helpful for readability either. I personally do not see where authors would really care if the lists are in two attributes or one. It seems rather a matter of taste or even believe. The point is that srcset can be extended to support more as you suggest in your example.

Greetings,
Dirk



But that seems rather harder to read...

- R. Niwa

On Mon, Nov 4, 2013 at 2:04 PM, Yoav Weiss <yoav at yoav.ws<mailto:yoav at yoav.ws>> wrote:



On Thu, Oct 24, 2013 at 9:33 AM, Ryosuke Niwa <rniwa at webkit.org<mailto:rniwa at webkit.org>> wrote:
On Wed, Oct 23, 2013 at 11:24 PM, Yoav Weiss <yoav at yoav.ws<mailto:yoav at yoav.ws>> wrote:
On Wed, Oct 23, 2013 at 10:22 PM, Ryosuke Niwa <rniwa at webkit.org<mailto:rniwa at webkit.org>> wrote:
On Tue, Oct 22, 2013 at 1:50 PM, Tab Atkins Jr. <jackalmage at gmail.com<mailto:jackalmage at gmail.com>> wrote:
On Sun, Oct 20, 2013 at 10:07 AM, Antti Koivisto <koivisto at iki.fi<mailto:koivisto at iki.fi>> wrote:
> Ignoring other aspects of this, the idea of making attribute name an
> enumeration is somewhat distasteful. It will require ugly special parsing.
> The platform has plenty of attribute values that are lists already.

The parsing aspect isn't particularly new - parsing data-* attributes
presents the same problem.  You just need to filter the list of
attributes on the element to look for things with a src- prefix.  I've
heard direct feedback from Yoav, implementing in Blink, that it's not
a big problem.

Just because it was not a big problem in one engine, it doesn't mean it won't be in other engines.
If we're supporting src-N attributes in WebKit, I'd like to see N to have a small upper bound; e.g. 10.
so that we can enumerate all parsed attributes statically at the compilation time.

Out of curiosity, what would be the benefits of such a restriction?

We're considering to implement an optimization that takes the advantage of parsed attributes being a finite set at the compilation time.

Having this feature will make it much harder to implement such an optimization.  Note that data-* attributes don't need to be parsed since it doesn't synchronously update Element's internal states.

- R. Niwa

Will setting the limit on the number of possible attributes at 99 still enable that optimization?
Many people (on the RICG's IRC and on Blink-dev) feel that setting the limit to 9, even if it'd be enough today, leaves fairly little space for future evolution. Setting it to some random number between 10 and 99 feels arbitrary to me. So, will 99 be OK with you?



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