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Re: Simplified source selection algorithm

From: Marcos Caceres <w3c@marcosc.com>
Date: Tue, 17 Sep 2013 15:32:47 +0100
To: Kornel Lesiński <kornel@geekhood.net>
Cc: public-respimg@w3.org
Message-ID: <66976A381FB04704BC760886983628D2@marcosc.com>

On Monday, September 16, 2013 at 11:53 PM, Kornel Lesiński wrote:

> In response to Simon Pieters' criticism that <source> selection algorithm  
> is too complex[1], I've drafted a simpler one:
> https://github.com/ResponsiveImagesCG/picture-element/issues/62#issuecomment-24479164
Just a quick note that we've (the Editors) been thinking along the same lines (and I've got a hacked up version of the spec over in my repo that already does some of the above). It's also what I presented during the workshop (i.e. "we are getting rid of the kitchen sink!")
> Simon finds this algorithm acceptable[2]. I'd like to hear your opinion  
> whether such solution is OK.

I thought his concern was more about having multiple elements … but anyway :)   
> - Dependency on Media Element and <video>-like algorithm is gone. There's  
> no networkState property.

> - The algorithm picks the first <source> that matches. Matching is done  
> based on media and type attributes.

> - I haven't written that explicitly on github, but selected <source  
> src/srcset> is interpreted pretty much like copying of its attributes to  
> <img src/srcset>.

Yep. Note also that <picture> no longer has a src or srcset attribute.   

> - Browser will re-evaluate sources whenever conditions change (so if  
> device is rotated or window is resized a different source may be picked,  
> and different image may be loaded).

> - Choice is made asynchronously and atomically from JavaScript's  
> perspective (i.e. messing with <source> DOM elements won't change the  
> selected source until next event loop tick).

Nice. Had not talked about this in the spec yet - but we were thinking the same thing.   
> - If you use <source media> with media query that browser cannot evaluate  
> immediately (e.g. min-width: in an iframe that has no layout yet) browser  
> may delay fetching of the image until CSS is loaded.

Nice too :)  

Received on Tuesday, 17 September 2013 14:33:25 UTC

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