Changeset 47554 for trunk/src/wp-includes/media.php

Timestamp:

04/08/2020 12:53:18 AM (5 years ago)

Author:

azaozz

Message:

Media: Enable lazy-loading of images by automatically adding the new loading="lazy" attribute to image tags on the front-end.

• Introduces wp_lazy_loading_enabled(), wp_filter_content_tags(), wp_img_tag_add_loading_attr(), and wp_img_tag_add_srcset_and_sizes_attr() functions.
• Introduces wp_lazy_loading_enabled, wp_img_tag_add_loading_attr, and wp_img_tag_add_srcset_and_sizes_attr filters.

Props flixos90, addyosmani, mor10, swissspidy, pierlo, westonruter, spacedmonkey, mikeschroder, jonoaldersonwp, peterwilsoncc, narwen, jeffpaul, OptimizingMatters, futtta, mukeshpanchal27, azaozz.

Fixes #44427.

File:

• trunk/src/wp-includes/media.php (modified) (6 diffs)

trunk/src/wp-includes/media.php

@@ -1022 +1022 @@
     $html  = '';
     $image = wp_get_attachment_image_src( $attachment_id, $size, $icon );
+
     if ( $image ) {
         list( $src, $width, $height ) = $image;
-        $hwstring                     = image_hwstring( $width, $height );
-        $size_class                   = $size;
+
+        $attachment = get_post( $attachment_id );
+        $hwstring   = image_hwstring( $width, $height );
+        $size_class = $size;
+
         if ( is_array( $size_class ) ) {
             $size_class = join( 'x', $size_class );
         }
-        $attachment   = get_post( $attachment_id );
+
         $default_attr = array(
             'src'   => $src,
@@ -1036 +1040 @@
         );
 
+        // Add `loading` attribute.
+        if ( wp_lazy_loading_enabled( 'img', 'wp_get_attachment_image' ) ) {
+            $default_attr['loading'] = 'lazy';
+        }
+
         $attr = wp_parse_args( $attr, $default_attr );
 
@@ -1062 +1071 @@
          * @since 2.8.0
          *
-         * @param string[]     $attr       Array of attribute values for the image markup, keyed by attribute name.
+         * @param array        $attr       Array of attribute values for the image markup, keyed by attribute name.
          *                                 See wp_get_attachment_image().
          * @param WP_Post      $attachment Image attachment post.
@@ -1069 +1078 @@
          */
         $attr = apply_filters( 'wp_get_attachment_image_attributes', $attr, $attachment, $size );
+
         $attr = array_map( 'esc_attr', $attr );
         $html = rtrim( "<img $hwstring" );
+
         foreach ( $attr as $name => $value ) {
             $html .= " $name=" . '"' . $value . '"';
         }
+
         $html .= ' />';
     }
@@ -1479 +1491 @@
 
 /**
- * Filters 'img' elements in post content to add 'srcset' and 'sizes' attributes.
- *
- * @since 4.4.0
- *
- * @see wp_image_add_srcset_and_sizes()
- *
- * @param string $content The raw post content to be filtered.
- * @return string Converted content with 'srcset' and 'sizes' attributes added to images.
- */
-function wp_make_content_images_responsive( $content ) {
-    if ( ! preg_match_all( '/<img [^>]+>/', $content, $matches ) ) {
-        return $content;
-    }
-
-    $selected_images = array();
-    $attachment_ids  = array();
-
-    foreach ( $matches[0] as $image ) {
-        if ( false === strpos( $image, ' srcset=' ) && preg_match( '/wp-image-([0-9]+)/i', $image, $class_id ) ) {
-            $attachment_id = absint( $class_id[1] );
-
-            if ( $attachment_id ) {
-                /*
-                 * If exactly the same image tag is used more than once, overwrite it.
-                 * All identical tags will be replaced later with 'str_replace()'.
-                 */
-                $selected_images[ $image ] = $attachment_id;
-                // Overwrite the ID when the same image is included more than once.
-                $attachment_ids[ $attachment_id ] = true;
-            }
-        }
-    }
-
-    if ( count( $attachment_ids ) > 1 ) {
-        /*
-         * Warm the object cache with post and meta information for all found
-         * images to avoid making individual database calls.
-         */
-        _prime_post_caches( array_keys( $attachment_ids ), false, true );
-    }
-
-    foreach ( $selected_images as $image => $attachment_id ) {
-        $image_meta = wp_get_attachment_metadata( $attachment_id );
-        $content    = str_replace( $image, wp_image_add_srcset_and_sizes( $image, $image_meta, $attachment_id ), $content );
-    }
-
-    return $content;
-}
-
-/**
  * Adds 'srcset' and 'sizes' attributes to an existing 'img' element.
  *
@@ -1612 +1574 @@
         // Add 'srcset' and 'sizes' attributes to the image markup.
         $image = preg_replace( '/<img ([^>]+?)[\/ ]*>/', '<img $1' . $attr . ' />', $image );
+    }
+
+    return $image;
+}
+
+/**
+ * Determine whether to add the `loading` attribute to the specified tag in the specified context.
+ *
+ * @since 5.5.0
+ *
+ * @param string $tag_name The tag name.
+ * @param string $context Additional context, like the current filter name or the function name from where this was called.
+ * @return bool Whether to add the attribute.
+ */
+function wp_lazy_loading_enabled( $tag_name, $context ) {
+    // By default add to all 'img' tags.
+    // See https://html.spec.whatwg.org/multipage/embedded-content.html#attr-img-loading
+    $default = ( 'img' === $tag_name );
+
+    /**
+     * Filters whether to add the `loading` attribute to the specified tag in the specified context.
+     *
+     * @since 5.5.0
+     *
+     * @param bool   $default Default value.
+     * @param string $tag_name The tag name.
+     * @param string $context Additional context, like the current filter name or the function name from where this was called.
+     */
+    return (bool) apply_filters( 'wp_lazy_loading_enabled', $default, $tag_name, $context );
+}
+
+/**
+ * Filters specific tags in post content and modifies their markup.
+ *
+ * This function adds `srcset`, `sizes`, and `loading` attributes to `img` HTML tags.
+ *
+ * @since 5.5.0
+ *
+ * @see wp_img_tag_add_loading_attr()
+ * @see wp_img_tag_add_srcset_and_sizes_attr()
+ *
+ * @param string $content The HTML content to be filtered.
+ * @param string $context Optional. Additional context to pass to the filters. Defaults to `current_filter()` when not set.
+ * @return string Converted content with images modified.
+ */
+function wp_filter_content_tags( $content, $context = null ) {
+    if ( null === $context ) {
+        $context = current_filter();
+    }
+
+    $add_loading_attr = wp_lazy_loading_enabled( 'img', $context );
+
+    if ( false === strpos( $content, '<img' ) ) {
+        return $content;
+    }
+
+    if ( ! preg_match_all( '/<img\s[^>]+>/', $content, $matches ) ) {
+        return $content;
+    }
+
+    // List of the unique `img` tags found in $content.
+    $images = array();
+
+    foreach ( $matches[0] as $image ) {
+        if ( preg_match( '/wp-image-([0-9]+)/i', $image, $class_id ) ) {
+            $attachment_id = absint( $class_id[1] );
+
+            if ( $attachment_id ) {
+                // If exactly the same image tag is used more than once, overwrite it.
+                // All identical tags will be replaced later with 'str_replace()'.
+                $images[ $image ] = $attachment_id;
+                continue;
+            }
+        }
+
+        $images[ $image ] = 0;
+    }
+
+    // Reduce the array to unique attachment IDs.
+    $attachment_ids = array_unique( array_filter( array_values( $images ) ) );
+
+    if ( count( $attachment_ids ) > 1 ) {
+        /*
+         * Warm the object cache with post and meta information for all found
+         * images to avoid making individual database calls.
+         */
+        _prime_post_caches( $attachment_ids, false, true );
+    }
+
+    foreach ( $images as $image => $attachment_id ) {
+        $filtered_image = $image;
+
+        // Add 'srcset' and 'sizes' attributes if applicable.
+        if ( $attachment_id > 0 && false === strpos( $filtered_image, ' srcset=' ) ) {
+            $filtered_image = wp_img_tag_add_srcset_and_sizes_attr( $filtered_image, $context, $attachment_id );
+        }
+
+        // Add 'loading' attribute if applicable.
+        if ( $add_loading_attr && false === strpos( $filtered_image, ' loading=' ) ) {
+            $filtered_image = wp_img_tag_add_loading_attr( $filtered_image, $context );
+        }
+
+        if ( $filtered_image !== $image ) {
+            $content = str_replace( $image, $filtered_image, $content );
+        }
+    }
+
+    return $content;
+}
+
+/**
+ * Adds `loading` attribute to an `img` HTML tag.
+ *
+ * @since 5.5.0
+ *
+ * @param string $image   The HTML `img` tag where the attribute should be added.
+ * @param string $context Additional context to pass to the filters.
+ * @return string Converted `img` tag with `loading` attribute added.
+ */
+function wp_img_tag_add_loading_attr( $image, $context ) {
+    /**
+     * Filters the `loading` attribute value. Default `lazy`.
+     *
+     * Returning `false` or an empty string will not add the attribute.
+     * Returning `true` will add the default value.
+     *
+     * @since 5.5.0
+     *
+     * @param string $value   The `loading` attribute value, defaults to `lazy`.
+     * @param string $image   The HTML `img` tag to be filtered.
+     * @param string $context Additional context about how the function was called or where the img tag is.
+     */
+    $value = apply_filters( 'wp_img_tag_add_loading_attr', 'lazy', $image, $context );
+
+    if ( $value ) {
+        if ( ! in_array( $value, array( 'lazy', 'eager' ), true ) ) {
+            $value = 'lazy';
+        }
+
+        $quote = null;
+
+        // Check if the img tag is valid (has `src` attribute) and get the quote character.
+        // In almost all cases it will have src and a double quote.
+        if ( false !== strpos( $image, ' src="' ) ) {
+            $quote = '"';
+        } elseif ( preg_match( '/\ssrc\s*=(["\'])/', $image, $matches ) ) {
+            $quote = $matches[1];
+        }
+
+        if ( $quote ) {
+            $loading = "loading={$quote}{$value}{$quote}";
+
+            return str_replace( '<img', "<img {$loading}", $image );
+        }
+    }
+
+    return $image;
+}
+
+/**
+ * Adds `srcset` and `sizes` attributes to an existing `img` HTML tag.
+ *
+ * @since 5.5.0
+ *
+ * @param string $image         The HTML `img` tag where the attribute should be added.
+ * @param string $context       Additional context to pass to the filters.
+ * @param int    $attachment_id Image attachment ID.
+ * @return string Converted 'img' element with 'loading' attribute added.
+ */
+function wp_img_tag_add_srcset_and_sizes_attr( $image, $context, $attachment_id ) {
+    /**
+     * Filters whether to add the `srcset` and `sizes` HTML attributes to the img tag. Default `true`.
+     *
+     * Returning anything else than `true` will not add the attributes.
+     *
+     * @since 5.5.0
+     *
+     * @param bool   $value         The filtered value, defaults to `true`.
+     * @param string $image         The HTML `img` tag where the attribute should be added.
+     * @param string $context       Additional context about how the function was called or where the img tag is.
+     * @param int    $attachment_id The image attachment ID.
+     */
+    $add = apply_filters( 'wp_img_tag_add_srcset_and_sizes_attr', true, $image, $context, $attachment_id );
+
+    if ( true === $add ) {
+        $image_meta = wp_get_attachment_metadata( $attachment_id );
+        return wp_image_add_srcset_and_sizes( $image, $image_meta, $attachment_id );
     }