<?php
/**
* Server-side rendering of the `core/details` block.
*
* @package WordPress
*/
/**
* Sets fetchpriority="low" on all IMG tags within the collapsed Details block.
*
* Images in a collapsed Details block are hidden until the block is expanded, so they should
* not compete with any resources in the critical rendering path, such as the LCP element image.
*
* @since 7.0.0
*
* @param string $block_content The block content.
* @param array $block The full block, including name and attributes.
* @return string Modified HTML with fetchpriority="low" on all IMG tags when the showContent attribute is false.
*/
function block_core_details_set_img_fetchpriority_low( $block_content, array $block ): string {
if ( ! is_string( $block_content ) ) {
return '';
}
// If the Details block is open by default, short-circuit to let core add fetchpriority=high if appropriate.
if ( $block['attrs']['showContent'] ?? false ) {
return $block_content;
}
$tags = new WP_HTML_Tag_Processor( $block_content );
while ( $tags->next_tag( 'IMG' ) ) {
$tags->set_attribute( 'fetchpriority', 'low' );
}
return $tags->get_updated_html();
}
add_filter( 'render_block_core/details', 'block_core_details_set_img_fetchpriority_low', 10, 2 );
/**
* Registers the `core/details` block on server.
*
* @since 7.0.0
*/
function register_block_core_details() {
register_block_type_from_metadata( __DIR__ . '/details' );
}
add_action( 'init', 'register_block_core_details' );