n.
* 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;
}
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