Ticket #44427: 44427.2.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_make_content_images_lazy' );
 
 add_filter( 'the_excerpt', 'wptexturize' );
 add_filter( 'the_excerpt', 'convert_smilies' );

src/wp-includes/media.php

@@ -966 +966 @@
                         'class' => "attachment-$size_class size-$size_class",
                         'alt'   => trim( strip_tags( get_post_meta( $attachment_id, '_wp_attachment_image_alt', true ) ) ),
                 );
-
+                if ( current_theme_supports( 'lazy-loading-images' ) ) {
+                        $default_attr['loading'] = 'lazy';
+        }
                 $attr = wp_parse_args( $attr, $default_attr );
 
                 // Generate 'srcset' and 'sizes' if not already present.
@@ -1528 +1530 @@
         return $image;
 }
 
+/**
+ * Filters 'img' elements in post content to add 'loading' attributes.
+ *
+ * @param string $content The raw post content to be filtered.
+ *
+ * @since 5.x.x
+ *
+ * @return string Converted content with 'loading' attributes added to images.
+ * @see   wp_tag_add_lazy_load()
+ *
+ */
+function wp_make_content_images_lazy( $content ) {
+        if ( current_theme_supports( 'lazy-loading-images' ) ) {
+                $content = wp_tag_add_lazy_load( $content, 'img' );
+        }
+
+        return $content;
+}
+
+
+/**
+ * Filters html tag elements in post content to add 'loading' attributes.
+ *
+ * @param string $content The raw post content to be filtered.
+ * @param string $tag     The html tag to scan and replace with loading attribute. Default: img
+ *
+ * @since 5.x.x
+ *
+ * @return string Converted content with 'loading' attributes added to images.
+ */
+function wp_tag_add_lazy_load( $content, $tag = 'img' ) {
+        if ( ! preg_match_all( '/<' . $tag . ' [^>]+>/', $content, $matches ) ) {
+                return $content;
+        }
+
+        $images = array_shift( $matches );
+
+        foreach ( $images as $image ) {
+                if ( false === strpos( $image, ' loading=' ) ) {
+                        $lazy_image = str_replace( '<' . $tag . ' ', '<' . $tag . ' loading="lazy" ', $image );
+                        $content    = str_replace( $image, $lazy_image, $content );
+                }
+        }
+
+        return $content;
+}
+
 /**
  * Adds a 'wp-post-image' class to post thumbnails. Internal use only.
  *

src/wp-includes/pluggable.php

@@ -2561 +2561 @@
                         'extra_attr'    => '',
                 );
 
+                if ( current_theme_supports( 'lazy-loading-images' ) ) {
+                        $defaults['loading'] = 'lazy';
+                }
+
                 if ( empty( $args ) ) {
                         $args = array();
                 }