Add sanitizer to fixup issues with core themes

includes/amp-helper-functions.php

@@ -524,6 +524,10 @@ function amp_get_content_sanitizers( $post = null ) {
 	 */
 	$sanitizers = apply_filters( 'amp_content_sanitizers',
 		array(
+			'AMP_Core_Theme_Sanitizer'        => array(
+				'template'   => get_template(),
+				'stylesheet' => get_stylesheet(),
+			),
 			'AMP_Img_Sanitizer'               => array(),
 			'AMP_Form_Sanitizer'              => array(),
 			'AMP_Comments_Sanitizer'          => array(),

includes/class-amp-autoloader.php

@@ -82,6 +82,7 @@ class AMP_Autoloader {
 		'AMP_Style_Sanitizer'                         => 'includes/sanitizers/class-amp-style-sanitizer',
 		'AMP_Tag_And_Attribute_Sanitizer'             => 'includes/sanitizers/class-amp-tag-and-attribute-sanitizer',
 		'AMP_Video_Sanitizer'                         => 'includes/sanitizers/class-amp-video-sanitizer',
+		'AMP_Core_Theme_Sanitizer'                    => 'includes/sanitizers/class-amp-core-theme-sanitizer',
 		'AMP_Customizer_Design_Settings'              => 'includes/settings/class-amp-customizer-design-settings',
 		'AMP_Customizer_Settings'                     => 'includes/settings/class-amp-customizer-settings',
 		'AMP_Content'                                 => 'includes/templates/class-amp-content',

includes/class-amp-theme-support.php

@@ -159,6 +159,12 @@ public static function finish_init() {
 		self::$sanitizer_classes = amp_get_content_sanitizers();
 		self::$sanitizer_classes = AMP_Validation_Manager::filter_sanitizer_args( self::$sanitizer_classes );
 		self::$embed_handlers    = self::register_content_embed_handlers();
+
+		foreach ( self::$sanitizer_classes as $sanitizer_class => $args ) {
+			if ( method_exists( $sanitizer_class, 'add_buffering_hooks' ) ) {
+				call_user_func( array( $sanitizer_class, 'add_buffering_hooks' ), $args );
+			}
+		}
 	}
 
 	/**
@@ -303,6 +309,10 @@ public static function add_hooks() {
 		add_action( 'comment_form', array( __CLASS__, 'amend_comment_form' ), 100 );
 		remove_action( 'comment_form', 'wp_comment_form_unfiltered_html_nonce' );
 		add_filter( 'wp_kses_allowed_html', array( __CLASS__, 'whitelist_layout_in_wp_kses_allowed_html' ), 10 );
+		add_filter( 'get_header_image_tag', array( __CLASS__, 'conditionally_output_header' ), 10, 3 );
+		add_action( 'wp_enqueue_scripts', function() {
+			wp_dequeue_script( 'comment-reply' ); // Handled largely by AMP_Comments_Sanitizer and *reply* methods in this class.
+		} );
 
 		// @todo Add character conversion.
 	}
@@ -1264,4 +1274,89 @@ public static function enqueue_assets() {
 		// Enqueue default styles expected by sanitizer.
 		wp_enqueue_style( 'amp-default', amp_get_asset_url( 'css/amp-default.css' ), array(), AMP__VERSION );
 	}
+
+	/**
+	 * Conditionally replace the header image markup with a header video or image.
+	 *
+	 * This is JS-driven in Core themes like Twenty Sixteen and Twenty Seventeen.
+	 * So in order for the header video to display,
+	 * this replaces the markup of the header image.
+	 *
+	 * @since 1.0
+	 * @link https://github.com/WordPress/wordpress-develop/blob/d002fde80e5e3a083e5f950313163f566561517f/src/wp-includes/js/wp-custom-header.js#L54
+	 * @param string $html The image markup to filter.
+	 * @param array  $header The header config array.
+	 * @param array  $atts The image markup attributes.
+	 * @return string $html Filtered markup.
+	 */
+	public static function conditionally_output_header( $html, $header, $atts ) {
+		unset( $header );
+		if ( ! is_header_video_active() ) {
+			return $html;
+		};
+
+		if ( ! has_header_video() ) {
+			return AMP_HTML_Utils::build_tag( 'amp-img', $atts );
+		}
+
+		return self::output_header_video( $atts );
+	}
+
+	/**
+	 * Replace the header image markup with a header video.
+	 *
+	 * @since 1.0
+	 * @link https://github.com/WordPress/wordpress-develop/blob/d002fde80e5e3a083e5f950313163f566561517f/src/wp-includes/js/wp-custom-header.js#L54
+	 * @link https://github.com/WordPress/wordpress-develop/blob/d002fde80e5e3a083e5f950313163f566561517f/src/wp-includes/js/wp-custom-header.js#L78
+	 *
+	 * @param array $atts The header tag attributes array.
+	 * @return string $html Filtered markup.
+	 */
+	public static function output_header_video( $atts ) {
+		// Remove the script for video.
+		wp_deregister_script( 'wp-custom-header' );
+		$video_settings = get_header_video_settings();
+
+		$parsed_url       = wp_parse_url( $video_settings['videoUrl'] );
+		$query            = isset( $parsed_url['query'] ) ? wp_parse_args( $parsed_url['query'] ) : null;
+		$video_attributes = array(
+			'media'    => '(min-width: ' . $video_settings['minWidth'] . 'px)',
+			'width'    => $video_settings['width'],
+			'height'   => $video_settings['height'],
+			'layout'   => 'responsive',
+			'autoplay' => '',
+			'id'       => 'wp-custom-header-video',
+		);
+
+		// Create image banner to stay behind the video.
+		$image_header = AMP_HTML_Utils::build_tag( 'amp-img', $atts );
+
+		// If the video URL is for YouTube, return an <amp-youtube> element.
+		if ( isset( $parsed_url['host'], $query['v'] ) && ( false !== strpos( $parsed_url['host'], 'youtube' ) ) ) {
+			$video_header = AMP_HTML_Utils::build_tag(
+				'amp-youtube',
+				array_merge(
+					$video_attributes,
+					array(
+						'data-videoid'        => $query['v'],
+						'data-param-rel'      => '0', // Don't show related videos.
+						'data-param-showinfo' => '0', // Don't show video title at the top.
+						'data-param-controls' => '0', // Don't show video controls.
+					)
+				)
+			);
+		} else {
+			$video_header = AMP_HTML_Utils::build_tag(
+				'amp-video',
+				array_merge(
+					$video_attributes,
+					array(
+						'src' => $video_settings['videoUrl'],
+					)
+				)
+			);
+		}
+
+		return $image_header . $video_header;
+	}
 }

includes/sanitizers/class-amp-base-sanitizer.php

@@ -121,6 +121,22 @@ public function __construct( $dom, $args = array() ) {
 		}
 	}
 
+	/**
+	 * Add filters to manipulate output during output buffering before the DOM is constructed.
+	 *
+	 * Add actions and filters before the page is rendered so that the sanitizer can fix issues during output buffering.
+	 * This provides an alternative to manipulating the DOM in the sanitize method. This is a static function because
+	 * it is invoked before the class is instantiated, as the DOM is not available yet. This method is only called
+	 * when 'amp' theme support is present. It is conceptually similar to the AMP_Base_Embed_Handler class's register_embed
+	 * method.
+	 *
+	 * @since 1.0
+	 * @see \AMP_Base_Embed_Handler::register_embed()
+	 *
+	 * @param array $args Args.
+	 */
+	public static function add_buffering_hooks( $args = array() ) {}
+
 	/**
 	 * Get mapping of HTML selectors to the AMP component selectors which they may be converted into.
 	 *