[wp-trac] [WordPress Trac] #44427: Introduce lazy-loading API for media and other elements

[WordPress Trac]

#44427: Introduce lazy-loading API for media and other elements
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 Reporter:  mor10                                |       Owner:  flixos90
     Type:  enhancement                          |      Status:  closed
 Priority:  normal                               |   Milestone:  5.5
Component:  Media                                |     Version:  5.4
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  has-patch has-unit-tests 2nd-        |     Focuses:
  opinion early needs-testing needs-dev-note     |  performance
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Comment (by flixos90):

 In [changeset:"48170" 48170]:
 {{{
 #!CommitTicketReference repository="" revision="48170"
 Media: Ensure images have dimensions to reduce layout shift and facilitate
 lazy-loading.

 This changeset ensures that attachment images which are inserted without
 `width` and `height` attributes still receive them in the frontend, to
 reduce cumulative layout shift. Adding the dimensions happens as part of
 the logic for adding `srcset` and `sizes` attributes, which already assume
 the specific width and height of the respective image.

 Images are now only lazy-loaded if they have `width` and `height`
 attributes present. While missing these attributes itself is what causes
 layout shifts, lazy-loading such images can make this problem more
 apparent to the user.

 Props adamsilverstein, westonruter.
 Fixes #50367. See #44427.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/44427#comment:108>
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