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

On Mon, Nov 4, 2013 at 10:19 PM, Ryosuke Niwa 
<rn...@webkit.org<mailto:rn...@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 ph...@0.5x.jpg, 1x ph...@1x.jpg, 2x 
ph...@2x.jpg"
     src-2="0.5x photo-c...@0.5x.jpg, 1x photo-c...@1x.jpg, 2x 
photo-c...@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 ph...@0.5x.jpg, 1x ph...@1x.jpg, 2x 
ph...@2x.jpg || 0.5x photo-c...@0.5x.jpg, 1x photo-c...@1x.jpg, 2x 
photo-c...@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 <y...@yoav.ws<mailto:y...@yoav.ws>> 
wrote:



On Thu, Oct 24, 2013 at 9:33 AM, Ryosuke Niwa 
<rn...@webkit.org<mailto:rn...@webkit.org>> wrote:
On Wed, Oct 23, 2013 at 11:24 PM, Yoav Weiss 
<y...@yoav.ws<mailto:y...@yoav.ws>> wrote:
On Wed, Oct 23, 2013 at 10:22 PM, Ryosuke Niwa 
<rn...@webkit.org<mailto:rn...@webkit.org>> wrote:
On Tue, Oct 22, 2013 at 1:50 PM, Tab Atkins Jr. 
<jackalm...@gmail.com<mailto:jackalm...@gmail.com>> wrote:
On Sun, Oct 20, 2013 at 10:07 AM, Antti Koivisto 
<koivi...@iki.fi<mailto:koivi...@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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