[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:  feature request           |      Status:  assigned
 Priority:  normal                    |   Milestone:  5.4
Component:  Media                     |     Version:
 Severity:  normal                    |  Resolution:
 Keywords:  has-patch has-unit-tests  |     Focuses:  performance
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Comment (by spacedmonkey):

 Reviewing
 [https://core.trac.wordpress.org/attachment/ticket/44427/44427.7.diff
 44427.7.diff]

 - Agree iframes should be removed, as they are problematic.

 {{{#!php
 foreach ( array( 'the_content', 'the_excerpt', 'comment_text',
 'widget_text_content' ) as $filter ) {
                 add_filter( $filter, 'wp_lazy_load_content_media' );
  }
 }}}
 - These lines above. I think the priority should be changed to 8. This
 means it fire way before most plugins. It also means that added before
 blocks and shortcodes are added. This stops any image tags that are added
 in via a third party block/shortcode from getting the lazy loading
 attribute. There maybe good reason a develop might want a image to not
 lazy loading, like if they are using a tracking pixel in a shortcode (I
 have done myself so I know that happens).
 - Should we disable lazy loading image if the theme has not
  defined add_theme_support for
 [https://developer.wordpress.org/reference/functions/add_theme_support/#html5
 html5]? This would stop older theme written in XHTML from becoming invalid
 markup. A simple workout like this might work.
 {{{#!php
 add_action( 'template_redirect', 'wp_remove_lazy_tags', 5 );
 function wp_remove_lazy_tags(){
     if( false === get_theme_support( 'html5' ) ) {
         add_filter( 'wp_lazy_load_content_media', '__return_empty_array');
     }
 }

 }}}
 - I think we need more unit tests, especially ones with malforms img tags,
 like attributes on new lines, data attributes and the like.


 Generally I think we are nearly there.

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Ticket URL: <https://core.trac.wordpress.org/ticket/44427#comment:64>
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