s within content blobs as they need to be handled together with the other * images within the post content or widget content. * Without this clause, they would already be considered within their own context which skews the image count and * can result in the first post content image being lazy-loaded or an image further down the page being marked as a * high priority. */ if ( 'the_content' !== $context && doing_filter( 'the_content' ) || 'widget_text_content' !== $context && doing_filter( 'widget_text_content' ) || 'widget_block_content' !== $context && doing_filter( 'widget_block_content' ) ) { /** This filter is documented in wp-includes/media.php */ return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context ); } /* * Add `decoding` with a value of "async" for every image unless it has a * conflicting `decoding` attribute already present. */ if ( 'img' === $tag_name ) { if ( isset( $attr['decoding'] ) ) { $loading_attrs['decoding'] = $attr['decoding']; } else { $loading_attrs['decoding'] = 'async'; } } // For any resources, width and height must be provided, to avoid layout shifts. if ( ! isset( $attr['width'], $attr['height'] ) ) { /** This filter is documented in wp-includes/media.php */ return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context ); } /* * The key function logic starts here. */ $maybe_in_viewport = null; $increase_count = false; $maybe_increase_count = false; // Logic to handle a `loading` attribute that is already provided. if ( isset( $attr['loading'] ) ) { /* * Interpret "lazy" as not in viewport. Any other value can be * interpreted as in viewport (realistically only "eager" or `false` * to force-omit the attribute are other potential values). */ if ( 'lazy' === $attr['loading'] ) { $maybe_in_viewport = false; } else { $maybe_in_viewport = true; } } // Logic to handle a `fetchpriority` attribute that is already provided. if ( isset( $attr['fetchpriority'] ) && 'high' === $attr['fetchpriority'] ) { /* * If the image was already determined to not be in the viewport (e.g. * from an already provided `loading` attribute), trigger a warning. * Otherwise, the value can be interpreted as in viewport, since only * the most important in-viewport image should have `fetchpriority` set * to "high". */ if ( false === $maybe_in_viewport ) { _doing_it_wrong( __FUNCTION__, __( 'An image should not be lazy-loaded and marked as high priority at the same time.' ), '6.3.0' ); /* * Set `fetchpriority` here for backward-compatibility as we should * not override what a developer decided, even though it seems * incorrect. */ $loading_attrs['fetchpriority'] = 'high'; } else { $maybe_in_viewport = true; } } if ( null === $maybe_in_viewport ) { $header_enforced_contexts = array( 'template_part_' . WP_TEMPLATE_PART_AREA_HEADER => true, 'get_header_image_tag' => true, ); /** * Filters the header-specific contexts. * * @since 6.4.0 * * @param array $default_header_enforced_contexts Map of contexts for which elements should be considered * in the header of the page, as $context => $enabled * pairs. The $enabled should always be true. */ $header_enforced_contexts = apply_filters( 'wp_loading_optimization_force_header_contexts', $header_enforced_contexts ); // Consider elements with these header-specific contexts to be in viewport. if ( isset( $header_enforced_contexts[ $context ] ) ) { $maybe_in_viewport = true; $maybe_increase_count = true; } elseif ( ! is_admin() && in_the_loop() && is_main_query() ) { /* * Get the content media count, since this is a main query * content element. This is accomplished by "increasing" * the count by zero, as the only way to get the count is * to call this function. * The actual count increase happens further below, based * on the `$increase_count` flag set here. */ $content_media_count = wp_increase_content_media_count( 0 ); $increase_count = true; // If the count so far is below the threshold, `loading` attribute is omitted. if ( $content_media_count < wp_omit_loading_attr_threshold() ) { $maybe_in_viewport = true; } else { $maybe_in_viewport = false; } } elseif ( // Only apply for main query but before the loop. $wp_query->before_loop && $wp_query->is_main_query() /* * Any image before the loop, but after the header has started should not be lazy-loaded, * except when the footer has already started which can happen when the current template * does not include any loop. */ && did_action( 'get_header' ) && ! did_action( 'get_footer' ) ) { $maybe_in_viewport = true; $maybe_increase_count = true; } } /* * If the element is in the viewport (`true`), potentially add * `fetchpriority` with a value of "high". Otherwise, i.e. if the element * is not not in the viewport (`false`) or it is unknown (`null`), add * `loading` with a value of "lazy". */ if ( $maybe_in_viewport ) { $loading_attrs = wp_maybe_add_fetchpriority_high_attr( $loading_attrs, $tag_name, $attr ); } else { // Only add `loading="lazy"` if the feature is enabled. if ( wp_lazy_loading_enabled( $tag_name, $context ) ) { $loading_attrs['loading'] = 'lazy'; } } /* * If flag was set based on contextual logic above, increase the content * media count, either unconditionally, or based on whether the image size * is larger than the threshold. */ if ( $increase_count ) { wp_increase_content_media_count(); } elseif ( $maybe_increase_count ) { /** This filter is documented in wp-includes/media.php */ $wp_min_priority_img_pixels = apply_filters( 'wp_min_priority_img_pixels', 50000 ); if ( $wp_min_priority_img_pixels <= $attr['width'] * $attr['height'] ) { wp_increase_content_media_count(); } } /** * Filters the loading optimization attributes. * * @since 6.4.0 * * @param array $loading_attrs The loading optimization attributes. * @param string $tag_name The tag name. * @param array $attr Array of the attributes for the tag. * @param string $context Context for the element for which the loading optimization attribute is requested. */ return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context ); } /** * Gets the threshold for how many of the first content media elements to not lazy-load. * * This function runs the {@see 'wp_omit_loading_attr_threshold'} filter, which uses a default threshold value of 3. * The filter is only run once per page load, unless the `$force` parameter is used. * * @since 5.9.0 * * @param bool $force Optional. If set to true, the filter will be (re-)applied even if it already has been before. * Default false. * @return int The number of content media elements to not lazy-load. */ function wp_omit_loading_attr_threshold( $force = false ) { static $omit_threshold; // This function may be called multiple times. Run the filter only once per page load. if ( ! isset( $omit_threshold ) || $force ) { /** * Filters the threshold for how many of the first content media elements to not lazy-load. * * For these first content media elements, the `loading` attribute will be omitted. By default, this is the case * for only the very first content media element. * * @since 5.9.0 * @since 6.3.0 The default threshold was changed from 1 to 3. * * @param int $omit_threshold The number of media elements where the `loading` attribute will not be added. Default 3. */ $omit_threshold = apply_filters( 'wp_omit_loading_attr_threshold', 3 ); } return $omit_threshold; } /** * Increases an internal content media count variable. * * @since 5.9.0 * @access private * * @param int $amount Optional. Amount to increase by. Default 1. * @return int The latest content media count, after the increase. */ function wp_increase_content_media_count( $amount = 1 ) { static $content_media_count = 0; $content_media_count += $amount; return $content_media_count; } /** * Determines whether to add `fetchpriority='high'` to loading attributes. * * @since 6.3.0 * @access private * * @param array $loading_attrs Array of the loading optimization attributes for the element. * @param string $tag_name The tag name. * @param array $attr Array of the attributes for the element. * @return array Updated loading optimization attributes for the element. */ function wp_maybe_add_fetchpriority_high_attr( $loading_attrs, $tag_name, $attr ) { // For now, adding `fetchpriority="high"` is only supported for images. if ( 'img' !== $tag_name ) { return $loading_attrs; } if ( isset( $attr['fetchpriority'] ) ) { /* * While any `fetchpriority` value could be set in `$loading_attrs`, * for consistency we only do it for `fetchpriority="high"` since that * is the only possible value that WordPress core would apply on its * own. */ if ( 'high' === $attr['fetchpriority'] ) { $loading_attrs['fetchpriority'] = 'high'; wp_high_priority_element_flag( false ); } return $loading_attrs; } // Lazy-loading and `fetchpriority="high"` are mutually exclusive. if ( isset( $loading_attrs['loading'] ) && 'lazy' === $loading_attrs['loading'] ) { return $loading_attrs; } if ( ! wp_high_priority_element_flag() ) { return $loading_attrs; } /** * Filters the minimum square-pixels threshold for an image to be eligible as the high-priority image. * * @since 6.3.0 * * @param int $threshold Minimum square-pixels threshold. Default 50000. */ $wp_min_priority_img_pixels = apply_filters( 'wp_min_priority_img_pixels', 50000 ); if ( $wp_min_priority_img_pixels <= $attr['width'] * $attr['height'] ) { $loading_attrs['fetchpriority'] = 'high'; wp_high_priority_element_flag( false ); } return $loading_attrs; } /** * Accesses a flag that indicates if an element is a possible candidate for `fetchpriority='high'`. * * @since 6.3.0 * @access private * * @param bool $value Optional. Used to change the static variable. Default null. * @return bool Returns true if high-priority element was marked already, otherwise false. */ function wp_high_priority_element_flag( $value = null ) { static $high_priority_element = true; if ( is_bool( $value ) ) { $high_priority_element = $value; } return $high_priority_element; }