[whatwg] The src-N proposal

James Graham james at hoppipolla.co.uk
Mon Nov 18 08:47:08 PST 2013

On 18/11/13 16:36, matmarquis.com wrote:
> I recall that some of the more
> specific resistance was due to the complication involved in
> implementing and testing existing media elements, but I can’t claim
> to understand precisely what manner of browser-internal complications
> `source` elements brought to the table.

The fundamental issue is atomicity; setting one or N attributes is an 
atomic operation from the point of view of script; creating N elements 
is not. This creates complexity because the algorithm has to deal with 
the possibility of DOM mutation changing the set of available sources 
before it has selected the correct one. I believe there was a proposal 
that simplified the semantics by ignoring mutations, but I hear it ran 
into problems with animated images, which I haven't understood in detail.

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