Files
wordpress/wp-includes
Felix Arntz c6f9238b77 Media: Conditionally skip lazy-loading on images before the loop to improve LCP performance.
When the logic to exclude images that likely appear above the fold from being lazy-loaded was introduced in WordPress 5.9, initially only images that appear within the main query loop were being considered. However, there is a good chance that images above the fold are rendered before the loop starts, for example in the header template part.

It is particularly common for a theme to display the featured image for a single post in the header. Based on HTTP Archive data from February 2023, the majority of LCP images that are still being lazy-loaded on WordPress sites use the `wp-post-image` class, i.e. are featured images.

This changeset enhances the logic in `wp_get_loading_attr_default()` to not lazy-load images that appear within or after the header template part and before the query loop, using a new `WP_Query::$before_loop` property.

For block themes, this was for the most part already addressed in [55318], however this enhancement implements the solution in a more generally applicable way that brings the improvement to classic themes as well.

Props thekt12, flixos90, spacedmonkey, costdev, zunaid321, mukesh27.
Fixes #58211.
See #53675, #56930.

Built from https://develop.svn.wordpress.org/trunk@55847


git-svn-id: http://core.svn.wordpress.org/trunk@55359 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2023-05-22 19:13:21 +00:00
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