[wp-trac] [WordPress Trac] #58773: Improve oEmbed lazy loading

[WordPress Trac]

#58773: Improve oEmbed lazy loading
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 Reporter:  adamsilverstein          |       Owner:  adamsilverstein
     Type:  defect (bug)             |      Status:  assigned
 Priority:  normal                   |   Milestone:  6.6
Component:  Embeds                   |     Version:
 Severity:  normal                   |  Resolution:
 Keywords:  has-patch has-unit-      |     Focuses:  performance,
  tests                              |  sustainability
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Changes (by westonruter):

 * milestone:  Future Release => 6.6


Comment:

 I think I have a solution for fixing lazy-loading of post embed iframes.
 See https://github.com/WordPress/performance/pull/1192

 I found that Chrome didn't reliably load the lazy-loaded post iframe when
 it had the `clip: rect(1px, 1px, 1px, 1px)` style present. Strangely, the
 iframe would load when navigating to the page but it wouldn't load when
 reloading the page. However, if the `clip` is replaced with `opacity:0;
 pointer-events:none;` then it works as expected. I tested in Chrome,
 Safari, and Firefox. I've opened a PR to apply this change to core as
 well: https://github.com/WordPress/wordpress-develop/pull/6474

 When testing this, remember to insert three images into the post content
 prior to the post embed. This  I had to first insert 3 images into the
 post content followed by the post embeds. This is because
 `wp_omit_loading_attr_threshold()` returns 3 so that lazy-loading is only
 applied to images and iframes after the 3rd.

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Ticket URL: <https://core.trac.wordpress.org/ticket/58773#comment:26>
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