since it's mostly all metadata
add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_assets' ) );
// Do not lazy load avatar in admin bar
add_action( 'admin_bar_menu', array( $this, 'remove_filters' ), 0 );
add_filter( 'wp_kses_allowed_html', array( $this, 'allow_lazy_attributes' ) );
}
public function setup_filters() {
add_filter( 'the_content', array( $this, 'add_image_placeholders' ), PHP_INT_MAX ); // run this later, so other content filters have run, including image_add_wh on WP.com
add_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
add_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
add_filter( 'widget_text', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
add_filter( 'get_image_tag', array( $this, 'add_image_placeholders' ), PHP_INT_MAX);
add_filter( 'wp_get_attachment_image_attributes', array( __CLASS__, 'process_image_attributes' ), PHP_INT_MAX );
}
public function remove_filters() {
remove_filter( 'the_content', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
remove_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
remove_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
remove_filter( 'widget_text', array( $this, 'add_image_placeholders' ), PHP_INT_MAX );
remove_filter( 'get_image_tag', array( $this, 'add_image_placeholders' ), PHP_INT_MAX);
remove_filter( 'wp_get_attachment_image_attributes', array( __CLASS__, 'process_image_attributes' ), PHP_INT_MAX );
}
/**
* Ensure that our lazy image attributes are not filtered out of image tags.
*
* @param array $allowed_tags The allowed tags and their attributes.
* @return array
*/
public function allow_lazy_attributes( $allowed_tags ) {
if ( ! isset( $allowed_tags['img'] ) ) {
return $allowed_tags;
}
// But, if images are allowed, ensure that our attributes are allowed!
$img_attributes = array_merge( $allowed_tags['img'], array(
'data-lazy-src' => 1,
'data-lazy-srcset' => 1,
'data-lazy-sizes' => 1,
) );
$allowed_tags['img'] = $img_attributes;
return $allowed_tags;
}
public function add_image_placeholders( $content ) {
// Don't lazyload for feeds, previews
if ( is_feed() || is_preview() ) {
return $content;
}
// Don't lazy-load if the content has already been run through previously
if ( false !== strpos( $content, 'data-lazy-src' ) ) {
return $content;
}
// Don't lazyload for amp-wp content
if ( function_exists( 'is_amp_endpoint' ) && is_amp_endpoint() ) {
return $content;
}
// This is a pretty simple regex, but it works
$content = preg_replace_callback( '#<(img)([^>]+?)(>(.*?)|[\/]?>)#si', array( __CLASS__, 'process_image' ), $content );
return $content;
}
/**
* Returns true when a given string of classes contains a class signifying lazy images
* should not process the image.
*
* @since 5.9.0
*
* @param string $classes A string of space-separated classes.
* @return bool
*/
public static function should_skip_image_with_blacklisted_class( $classes ) {
$blacklisted_classes = array(
'skip-lazy',
'gazette-featured-content-thumbnail',
);
/**
* Allow plugins and themes to tell lazy images to skip an image with a given class.
*
* @module lazy-images
*
* @since 5.9.0
*
* @param array An array of strings where each string is a class.
*/
$blacklisted_classes = apply_filters( 'jetpack_lazy_images_blacklisted_classes', $blacklisted_classes );
if ( ! is_array( $blacklisted_classes ) || empty( $blacklisted_classes ) ) {
return false;
}
foreach ( $blacklisted_classes as $class ) {
if ( false !== strpos( $classes, $class ) ) {
return true;
}
}
return false;
}
/**
* Processes images in content by acting as the preg_replace_callback
*
* @since 5.6.0
*
* @param array $matches
*
* @return string The image with updated lazy attributes
*/
static function process_image( $matches ) {
$old_attributes_str = $matches[2];
$old_attributes_kses_hair = wp_kses_hair( $old_attributes_str, wp_allowed_protocols() );
if ( empty( $old_attributes_kses_hair['src'] ) ) {
return $matches[0];
}
$old_attributes = self::flatten_kses_hair_data( $old_attributes_kses_hair );
$new_attributes = self::process_image_attributes( $old_attributes );
// If we didn't add lazy attributes, just return the original image source.
if ( empty( $new_attributes['data-lazy-src'] ) ) {
return $matches[0];
}
$new_attributes_str = self::build_attributes_string( $new_attributes );
return sprintf( '![]()
', $new_attributes_str, $matches[0] );
}
/**
* Given an array of image attributes, updates the `src`, `srcset`, and `sizes` attributes so
* that they load lazily.
*
* @since 5.7.0
*
* @param array $attributes
*
* @return array The updated image attributes array with lazy load attributes
*/
static function process_image_attributes( $attributes ) {
if ( empty( $attributes['src'] ) ) {
return $attributes;
}
if ( ! empty( $attributes['class'] ) && self::should_skip_image_with_blacklisted_class( $attributes['class'] ) ) {
return $attributes;
}
/**
* Allow plugins and themes to conditionally skip processing an image via its attributes.
*
* @module-lazy-images
*
* @since 5.9.0
*
* @param bool Default to not skip processing the current image.
* @param array An array of attributes via wp_kses_hair() for the current image.
*/
if ( apply_filters( 'jetpack_lazy_images_skip_image_with_atttributes', false, $attributes ) ) {
return $attributes;
}
$old_attributes = $attributes;
// Set placeholder and lazy-src
$attributes['src'] = self::get_placeholder_image();
$attributes['data-lazy-src'] = $old_attributes['src'];
// Handle `srcset`
if ( ! empty( $attributes['srcset'] ) ) {
$attributes['data-lazy-srcset'] = $old_attributes['srcset'];
unset( $attributes['srcset'] );
}
// Handle `sizes`
if ( ! empty( $attributes['sizes'] ) ) {
$attributes['data-lazy-sizes'] = $old_attributes['sizes'];
unset( $attributes['sizes'] );
}
/**
* Allow plugins and themes to override the attributes on the image before the content is updated.
*
* One potential use of this filter is for themes that set `height:auto` on the `img` tag.
* With this filter, the theme could get the width and height attributes from the
* $attributes array and then add a style tag that sets those values as well, which could
* minimize reflow as images load.
*
* @module lazy-images
*
* @since 5.6.0
*
* @param array An array containing the attributes for the image, where the key is the attribute name
* and the value is the attribute value.
*/
return apply_filters( 'jetpack_lazy_images_new_attributes', $attributes );
}
private static function get_placeholder_image() {
/**
* Allows plugins and themes to modify the placeholder image.
*
* This filter is not prefixed with jetpack_ to provide a smoother migration
* process from the WordPress Lazy Load plugin.
*
* @module lazy-images
*
* @since 5.6.0
*
* @param string The URL to the placeholder image
*/
return apply_filters(
'lazyload_images_placeholder_image',
plugins_url( 'modules/lazy-images/images/1x1.trans.gif', JETPACK__PLUGIN_FILE )
);
}
private static function flatten_kses_hair_data( $attributes ) {
$flattened_attributes = array();
foreach ( $attributes as $name => $attribute ) {
$flattened_attributes[ $name ] = $attribute['value'];
}
return $flattened_attributes;
}
private static function build_attributes_string( $attributes ) {
$string = array();
foreach ( $attributes as $name => $value ) {
if ( '' === $value ) {
$string[] = sprintf( '%s', $name );
} else {
$string[] = sprintf( '%s="%s"', $name, esc_attr( $value ) );
}
}
return implode( ' ', $string );
}
public function enqueue_assets() {
if ( Jetpack_AMP_Support::is_amp_request() ) {
return;
}
wp_enqueue_script(
'jetpack-lazy-images',
Jetpack::get_file_url_for_environment(
'_inc/build/lazy-images/js/lazy-images.min.js',
'modules/lazy-images/js/lazy-images.js'
),
array( 'jquery' ),
JETPACK__VERSION,
true
);
}
}