Ticket #44427: 44427.3.diff

src/wp-includes/default-filters.php

@@ -176 +176 @@
 add_filter( 'the_content', 'shortcode_unautop' );
 add_filter( 'the_content', 'prepend_attachment' );
 add_filter( 'the_content', 'wp_make_content_images_responsive' );
+add_filter( 'the_content', 'wp_lazy_load_content_media' );
 
 add_filter( 'the_excerpt', 'wptexturize' );
 add_filter( 'the_excerpt', 'convert_smilies' );

src/wp-includes/media.php

@@ -1013 +1013 @@
                         'alt'   => trim( strip_tags( get_post_meta( $attachment_id, '_wp_attachment_image_alt', true ) ) ),
                 );
 
+                /** This filter is documented in wp-includes/media.php */
+                if ( apply_filters( 'wp_lazy_load_content_media', true ) ) {
+                        $default_attr['loading'] = 'lazy';
+                }
+
                 $attr = wp_parse_args( $attr, $default_attr );
 
                 // Generate 'srcset' and 'sizes' if not already present.
@@ -1595 +1600 @@
 }
 
 /**
+ * Filters 'img' and 'iframe' elements in post content to add 'loading' attributes.
+ *
+ * @since 5.4.0
+ *
+ * @param string $content The raw post content to be filtered.
+ * @return string Converted content with 'loading' attributes added to images.
+ */
+function wp_lazy_load_content_media( $content ) {
+        $tags = array( 'img', 'iframe' );
+
+        /**
+         * Filters whether media in post content should be lazy-loaded with 'loading' attributes.
+         *
+         * @since 5.4.0
+         *
+         * @param bool $enabled Whether to lazy-load content media. Default true.
+         */
+        if ( ! apply_filters( 'wp_lazy_load_content_media', true ) ) {
+                return $content;
+        }
+
+        return preg_replace_callback(
+                '/<(' . implode( '|', $tags ) . ') [^>]+>/',
+                function( array $matches ) {
+                        if ( false === strpos( $matches[0], ' loading=' ) ) {
+                                $tag = $matches[1];
+                                return str_replace( '<' . $tag . ' ', '<' . $tag . ' loading="lazy" ', $matches[0] );
+                        }
+                        return $matches[0];
+                },
+                $content
+        );
+}
+
+/**
  * Adds a 'wp-post-image' class to post thumbnails. Internal use only.
  *
  * Uses the {@see 'begin_fetch_post_thumbnail_html'} and {@see 'end_fetch_post_thumbnail_html'}

src/wp-includes/pluggable.php

@@ -2591 +2591 @@
                         'extra_attr'    => '',
                 );
 
+                /** This filter is documented in wp-includes/media.php */
+                if ( apply_filters( 'wp_lazy_load_content_media', true ) ) {
+                        $defaults['loading'] = 'lazy';
+                }
+
                 if ( empty( $args ) ) {
                         $args = array();
                 }