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<?php |
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class Jetpack_Lazy_Images { |
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private static $__instance = null; |
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/** |
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* Singleton implementation |
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* |
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* @return object |
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*/ |
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public static function instance() { |
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if ( is_null( self::$__instance ) ) { |
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self::$__instance = new Jetpack_Lazy_Images(); |
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} |
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return self::$__instance; |
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} |
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/** |
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* Registers actions |
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*/ |
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private function __construct() { |
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if ( is_admin() ) { |
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return; |
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} |
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/** |
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* Whether the lazy-images module should load. |
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* |
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* This filter is not prefixed with jetpack_ to provide a smoother migration |
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* process from the WordPress Lazy Load plugin. |
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* |
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* @module lazy-images |
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* |
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* @since 5.6.0 |
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* |
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* @param bool true Whether lazy image loading should occur. |
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*/ |
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if ( ! apply_filters( 'lazyload_is_enabled', true ) ) { |
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return; |
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} |
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add_action( 'wp_head', array( $this, 'setup_filters' ), 9999 ); // we don't really want to modify anything in <head> since it's mostly all metadata |
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add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_assets' ) ); |
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// Do not lazy load avatar in admin bar |
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add_action( 'admin_bar_menu', array( $this, 'remove_filters' ), 0 ); |
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} |
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public function setup_filters() { |
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add_filter( 'the_content', array( $this, 'add_image_placeholders' ), 99 ); // run this later, so other content filters have run, including image_add_wh on WP.com |
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add_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), 11 ); |
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add_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), 11 ); |
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} |
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public function remove_filters() { |
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remove_filter( 'the_content', array( $this, 'add_image_placeholders' ), 99 ); |
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remove_filter( 'post_thumbnail_html', array( $this, 'add_image_placeholders' ), 11 ); |
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remove_filter( 'get_avatar', array( $this, 'add_image_placeholders' ), 11 ); |
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} |
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public function add_image_placeholders( $content ) { |
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// Don't lazyload for feeds, previews |
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if ( is_feed() || is_preview() ) { |
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return $content; |
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} |
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// Don't lazy-load if the content has already been run through previously |
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if ( false !== strpos( $content, 'data-lazy-src' ) ) { |
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return $content; |
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} |
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// Don't lazyload for amp-wp content |
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if ( function_exists( 'is_amp_endpoint' ) && is_amp_endpoint() ) { |
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return $content; |
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} |
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// This is a pretty simple regex, but it works |
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$content = preg_replace_callback( '#<(img)([^>]+?)(>(.*?)</\\1>|[\/]?>)#si', array( __CLASS__, 'process_image' ), $content ); |
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return $content; |
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} |
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static function process_image( $matches ) { |
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$old_attributes_str = $matches[2]; |
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$old_attributes_kses_hair = wp_kses_hair( $old_attributes_str, wp_allowed_protocols() ); |
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if ( empty( $old_attributes_kses_hair['src'] ) ) { |
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return $matches[0]; |
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} |
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$old_attributes = self::flatten_kses_hair_data( $old_attributes_kses_hair ); |
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$new_attributes = $old_attributes; |
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// Set placeholder and lazy-src |
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$new_attributes['src'] = self::get_placeholder_image(); |
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$new_attributes['data-lazy-src'] = $old_attributes['src']; |
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// Handle `srcset` |
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if ( ! empty( $new_attributes['srcset'] ) ) { |
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$new_attributes['data-lazy-srcset'] = $old_attributes['srcset']; |
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unset( $new_attributes['srcset'] ); |
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} |
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// Handle `sizes` |
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if ( ! empty( $new_attributes['sizes'] ) ) { |
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$new_attributes['data-lazy-sizes'] = $old_attributes['sizes']; |
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unset( $new_attributes['sizes'] ); |
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} |
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/** |
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* Allow plugins and themes to override the attributes on the image before the content is updated. |
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* |
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* One potential use of this filter is for themes that set `height:auto` on the `img` tag. |
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* With this filter, the theme could get the width and height attributes from the |
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* $new_attributes array and then add a style tag that sets those values as well, which could |
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* minimize reflow as images load. |
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* |
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* @module lazy-images |
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* |
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* @since 5.6.0 |
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* |
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* @param array An array containing the attributes for the image, where the key is the attribute name |
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* and the value is the attribute value. |
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*/ |
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$new_attributes = apply_filters( 'jetpack_lazy_images_new_attributes', $new_attributes ); |
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$new_attributes_str = self::build_attributes_string( $new_attributes ); |
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return sprintf( '<img %1$s><noscript>%2$s</noscript>', $new_attributes_str, $matches[0] ); |
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} |
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private static function get_placeholder_image() { |
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/** |
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* Allows plugins and themes to modify the placeholder image. |
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* |
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* This filter is not prefixed with jetpack_ to provide a smoother migration |
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* process from the WordPress Lazy Load plugin. |
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* |
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* @module lazy-images |
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* |
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* @since 5.6.0 |
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* |
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* @param string The URL to the placeholder image |
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*/ |
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return apply_filters( |
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'lazyload_images_placeholder_image', |
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plugins_url( 'modules/lazy-images/images/1x1.trans.gif', JETPACK__PLUGIN_FILE ) |
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); |
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} |
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private static function flatten_kses_hair_data( $attributes ) { |
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$flattened_attributes = array(); |
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foreach ( $attributes as $name => $attribute ) { |
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$flattened_attributes[ $name ] = $attribute['value']; |
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} |
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return $flattened_attributes; |
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} |
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private static function build_attributes_string( $attributes ) { |
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$string = array(); |
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foreach ( $attributes as $name => $value ) { |
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if ( '' === $value ) { |
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$string[] = sprintf( '%s', $name ); |
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} else { |
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$string[] = sprintf( '%s="%s"', $name, esc_attr( $value ) ); |
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} |
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} |
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return implode( ' ', $string ); |
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} |
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public function enqueue_assets() { |
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wp_enqueue_script( |
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'jetpack-lazy-images', |
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plugins_url( 'modules/lazy-images/js/lazy-images.js', JETPACK__PLUGIN_FILE ), |
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array( 'jquery' ), |
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JETPACK__VERSION, |
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true |
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); |
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} |
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} |
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Automattic /
jetpack
