[wp-trac] [WordPress Trac] #34292: Support for DNS Prefetching & Prerender

[WordPress Trac]

#34292: Support for DNS Prefetching & Prerender
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 Reporter:  bhubbard                             |       Owner:
     Type:  feature request                      |  voldemortensen
 Priority:  normal                               |      Status:  closed
Component:  Script Loader                        |   Milestone:  4.6
 Severity:  normal                               |     Version:
 Keywords:  has-patch has-unit-tests needs-docs  |  Resolution:  fixed
                                                 |     Focuses:
                                                 |  performance
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Comment (by peterwilsoncc):

 @superpoincare please note @swissspidy's comment about the function name
 being in flux, this may be causing your 500 error.

 A few notes:
 * I expect @barry has opinions about preconnecting to the CDN, I'm not
 overly concerned about preconnecting from the client side but Barry may be
 less keen for the sake of the CDN. We could add the preconnect headers
 using JavaScript in the detection script if needs be and preconnect while
 twemoji runs.
 * There is some validity to avoiding pre* for tags in the HTML header, if
 the HTML header before script output is > 14k (typical TCP packet size) a
 site has bigger problems. They could be removed later but that would raise
 backcompat concerns at the time.

 A couple of misses:
 * s.w.org is always https
 * there are two emoji CDNs, SVG and PNG, they happen to be on the same
 host by default
 * the filter on the emoji CDNs is missing

 Re [attachment:34292.10.diff]:
 * works, only shows for queued dependencies
 * is it more performant to run `in_array` on each iteration of the loop or
 wrap the return statement in `array_unique`. Does it even matter?

 I'll work up a patch covering the misses based off
 [attachment:34292.10.diff].

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Ticket URL: <https://core.trac.wordpress.org/ticket/34292#comment:58>
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