[wp-trac] [WordPress Trac] #52768: WordPress post URL oEmbed rendering blocked by iframe lazy-loading

[WordPress Trac]

#52768: WordPress post URL oEmbed rendering blocked by iframe lazy-loading
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 Reporter:  SirStuey                             |       Owner:
                                                 |  peterwilsoncc
     Type:  defect (bug)                         |      Status:  reviewing
 Priority:  normal                               |   Milestone:  5.7.1
Component:  Embeds                               |     Version:  5.7
 Severity:  normal                               |  Resolution:
 Keywords:  needs-testing has-patch has-unit-    |     Focuses:
  tests                                          |  performance
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Comment (by SirStuey):

 @joyously - the link ''is'' shown first, in the fallback blockquote.

 Why are the iframes hidden by default? I am guessing that it's because the
 fallback loads by default. The fallback link is displayed and then
 replaced by the iframe. Hiding the iframe ensures you get one or the
 other, and not both.

 Let's say that a WordPress URL is embedded in a post. That referenced link
 might change in time, either with a new URL, or it might be removed
 entirely. I've observed that, given the current way the embed is handled,
 the fallback URL will be displayed in blockquotes. If the target URL has
 changed or is removed, the iframe does not redirect, the fallback is
 displayed.

 When that fallback link is displayed, the iframe is hidden. If that iframe
 is able to load with content from the embed source, it loads visibly and
 the fallback is hidden.

 If there's nothing in that iframe, what's there to load? If the iframe
 isn't to be hidden by default, then that fallback might be redundant and
 you can have unpredictable display behavior.

 If the URL has changed and is properly redirected, clicking the blockquote
 link will still get you to the proper destination.

 There could be other reasons the fallback behavior was created.

 The question is this - can this WP embed hidden iframe behavior be
 reworked or removed, while still ensuring proper fallback link display
 when needed, and while keeping in mind any security concerns due to WP
 embeds coming in from potentially anywhere? How long would this take, and
 who might it involve, compared to the fix that the iframe lazy loading
 developer already came up with?

 The proposed fix should perfectly remedy things for the time being.

 With that update in place, the embed behavior can then be potentially
 reworked in a way that allows for iframe lazy loading. But, that's also a
 much bigger task since the developers will have to think about existing
 and future iframes. It also cannot be a theme-based css fix.

 There are 3 main approaches to fixing this bug.

 1) Revert the iframe lazy loading that was implemented in 5.7
 2) Update the 5.7 update to exclude Wordpress URL embed iframes from lazy
 loading
 3) Rework Wordpress URL embeds

 Option 2) is the fastest remedy for this issue, and it should not affect
 iframes unrelated to this issue, such as YouTube embeds.

 Option 3) should be the next step if lazy loading Wordpress URL embeds is
 still a priority. This would have also have to take into account both
 future and existing embeds.

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Ticket URL: <https://core.trac.wordpress.org/ticket/52768#comment:24>
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