[webkit-dev] The SrcN responsive images proposal

Benjamin Poulain benjamin at webkit.org
Wed Nov 6 18:32:15 PST 2013

On 11/6/13, 3:24 PM, Yoav Weiss wrote:
> On Wed, Nov 6, 2013 at 11:33 PM, Benjamin Poulain <benjamin at webkit.org
> <mailto:benjamin at webkit.org>> wrote:
>     On 11/6/13, 10:53 AM, John Mellor wrote:
>         On Sun, Oct 20, 2013 at 2:00 AM, Maciej Stachowiak
>         <mjs at apple.com <mailto:mjs at apple.com>
>         <mailto:mjs at apple.com <mailto:mjs at apple.com>>> wrote:
>           >
>           > My initial impression is that it seems a bit overengineered.
>         I sympathize. The issue of srcN appearing to be a complex
>         solution to a
>         seemingly simple problem came up again on IRC chatting to rniwa,
>         so I
>         thought I'd try to explain this briefly.
>         Unfortunately, responsive images is a deceptively complex
>         problem. There
>         are 3 main use cases:
>         1. dpr-switching: fixed-width image resolution based on
>         devicePixelRatio.
>         2. viewport-switching: flexible-width image resolution based on
>         viewport
>         width and devicePixelRatio.
>         3. art direction: same as #1 or #2, except additionally, must serve
>         completely different images based on viewport width.
>     How important and common are each of those use cases?
>     Handling every imaginable use case by the Engine is a non-goal.
>     There has been a lot of demand for dpr-switching since the first
>     iPad Retina. This has caused some very ugly hacks on the Web. It is
>     very important to address that issue.
>     Viewport switching is usually done to adapt images for mobile device
>     VS large/huge display devices. It is a valid concern but it is not
>     easily addressed. Srcset can/should likely be improved regarding this.
>     I believe (feel free to prove me wrong) dynamic viewport adaptation
>     and what you call "art direction" is not as common.
> On a survey ran at the last Mobilism conference (and on Twitter) 41% of
> respondents said they're already using some hack to get their responsive
> image "art-directed".
> A manual responsive site survey
> <http://japborst.net/blog/the-current-state-of-art-direction.html> showed that
> 23% of the sites "art-direct" their images, and 58% do that when
> (subjectively) the design requires it.
> So it might not be as common as viewport switching (which is practically
> everywhere), but it is pretty common.

The survey you linked 
(http://japborst.net/blog/the-current-state-of-art-direction.html) was 
targeting specifically responsive websites. Those websites represents 
only an unquantified subset of the web.

Even with that very targeted subset, only a small percentage was 
actually implementing art-direction.

It looks to me like art-direction should not be imposing all the design 
constraints over the more important use cases.

Something that is still unclear to me is why srcN would be doing a 
better job than JavaScript for art-direction?
There are many complex cases that are handled dynamically (changing 
images on zoom; tiling large images on zoom; changing layout on 
rotation; creating popover style layout when switching 
portrait/landscape, etc).


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