Automattic · jason10lee · Mar 12, 2026 · Mar 12, 2026 · Mar 13, 2026 · Mar 14, 2026
@@ -1,7 +1,10 @@
 {
+	"$schema": "https://schemas.wp.org/trunk/block.json",
+	"apiVersion": 3,
 	"name": "newspack-block-theme/article-subtitle",
 	"title": "Article Subtitle",
 	"category": "newspack",
+	"usesContext": [ "postId", "postType" ],
 	"attributes": {},
 	"supports": {
 		"html": false,

@@ -21,15 +21,15 @@ final class Subtitle_Block {
 	 */
 	public static function init() {
 		\add_action( 'init', [ __CLASS__, 'register_block_and_post_meta' ] );
-		\add_action( 'enqueue_block_editor_assets', [ __CLASS__, 'enqueue_block_editor_assets' ] );
+		\add_action( 'enqueue_block_assets', [ __CLASS__, 'enqueue_block_assets' ] );
 	}
 
 	/**
 	 * Register the block.
 	 */
 	public static function register_block_and_post_meta() {
 		register_block_type_from_metadata(
-			__DIR__ . '/block.json',
+			__DIR__,
 			[
 				'render_callback' => [ __CLASS__, 'render_block' ],
 			]
@@ -52,29 +52,31 @@ public static function register_block_and_post_meta() {
 	public static function render_block() {
 		$post_subtitle = get_post_meta( get_the_ID(), self::POST_META_NAME, true );
 		$wrapper_attributes = get_block_wrapper_attributes();
-		return sprintf( '<p %1$s>%2$s</p>', $wrapper_attributes, $post_subtitle );
+		return sprintf( '<p %1$s>%2$s</p>', $wrapper_attributes, esc_html( $post_subtitle ) );
 	}
 
 	/**
-	 * Enqueue block editor ad suppression assets for any post type considered
-	 * "viewable".
+	 * Enqueue block editor subtitle assets for the appropriate editor context.
 	 */
-	public static function enqueue_block_editor_assets() {
+	public static function enqueue_block_assets() {
+		if ( ! \wp_should_load_block_editor_scripts_and_styles() ) {
+			return;
+		}
+
 		$script_data = [
 			'post_meta_name' => self::POST_META_NAME,
 		];
 
 		global $pagenow;
 		if ( $pagenow === 'site-editor.php' ) {
 			$handle = 'newspack-block-theme-subtitle-block-site-editor';
-			\wp_enqueue_script( $handle, \get_theme_file_uri( 'dist/subtitle-block-site-editor.js' ), [], NEWSPACK_BLOCK_THEME_VERSION, true );
+			$asset  = require \get_theme_file_path( 'dist/subtitle-block-site-editor.asset.php' );
+			\wp_enqueue_script( $handle, \get_theme_file_uri( 'dist/subtitle-block-site-editor.js' ), $asset['dependencies'], $asset['version'], true );
 			\wp_localize_script( $handle, 'newspack_block_theme_subtitle_block', $script_data );
-		}
-
-		$post_type = \get_current_screen()->post_type;
-		if ( $post_type === 'post' ) {
+		} elseif ( \get_current_screen() && \get_current_screen()->post_type === 'post' ) {
 			$handle = 'newspack-block-theme-subtitle-block-post-editor';
-			\wp_enqueue_script( $handle, \get_theme_file_uri( 'dist/subtitle-block-post-editor.js' ), [], NEWSPACK_BLOCK_THEME_VERSION, true );
+			$asset  = require \get_theme_file_path( 'dist/subtitle-block-post-editor.asset.php' );
+			\wp_enqueue_script( $handle, \get_theme_file_uri( 'dist/subtitle-block-post-editor.js' ), $asset['dependencies'], $asset['version'], true );
 			\wp_localize_script( $handle, 'newspack_block_theme_subtitle_block', $script_data );
 		}
 	}

@@ -6,22 +6,36 @@
  */
 import { registerPlugin } from '@wordpress/plugins';
 import { useSelect, useDispatch } from '@wordpress/data';
-import { useEffect } from '@wordpress/element';
+import { useEffect, useCallback, useRef } from '@wordpress/element';
 
 const META_FIELD_NAME = newspack_block_theme_subtitle_block.post_meta_name;
 
 const SUBTITLE_ID = 'newspack-post-subtitle-element';
 const SUBTITLE_STYLE_ID = 'newspack-post-subtitle-element-style';
 
-const appendSubtitleToTitleDOMElement = ( subtitle, callback ) => {
-	const titleWrapperEl = document.querySelector( '.edit-post-visual-editor__post-title-wrapper' );
+/**
+ * Get the correct document for the editor canvas.
+ * In iframe mode, the editor content is inside an iframe with name="editor-canvas".
+ * In non-iframe mode, falls back to the admin document.
+ */
+const getEditorCanvas = () => {
+	const iframe = document.querySelector( 'iframe[name="editor-canvas"]' );
+	if ( iframe?.contentDocument ) {
+		return iframe.contentDocument;
+	}
+	return document;
+};
+
+const appendSubtitleToTitleDOMElement = ( subtitle, editorDoc, callback ) => {
+	const titleWrapperEl = editorDoc.querySelector( '.edit-post-visual-editor__post-title-wrapper' );
 
-	if ( titleWrapperEl && typeof subtitle === 'string' ) {
-		let subtitleEl = document.getElementById( SUBTITLE_ID );
+	if ( titleWrapperEl ) {
+		let subtitleEl = editorDoc.getElementById( SUBTITLE_ID );
 		const titleParent = titleWrapperEl.parentNode;
 
-		if ( ! document.getElementById( SUBTITLE_STYLE_ID ) ) {
-			const style = document.createElement( 'style' );
+		if ( ! editorDoc.getElementById( SUBTITLE_STYLE_ID ) ) {
+			const style = editorDoc.createElement( 'style' );
+			style.id = SUBTITLE_STYLE_ID;
 			style.innerHTML = `
                 #${ SUBTITLE_ID } {
                     font-style: italic;
@@ -33,19 +47,23 @@ const appendSubtitleToTitleDOMElement = ( subtitle, callback ) => {
                     padding-right: var(--wp--preset--spacing--30);
                 }
             `;
-			document.head.appendChild( style );
+			editorDoc.head.appendChild( style );
 		}
 
 		if ( ! subtitleEl ) {
-			subtitleEl = document.createElement( 'div' );
+			subtitleEl = editorDoc.createElement( 'div' );
 			subtitleEl.setAttribute( 'contenteditable', 'plaintext-only' );
 			subtitleEl.addEventListener( 'input', () => {
-				callback( subtitleEl.innerHTML );
+				callback( subtitleEl.textContent );
 			} );
 			subtitleEl.id = SUBTITLE_ID;
 			titleParent.insertBefore( subtitleEl, titleWrapperEl.nextSibling );
 		}
-		subtitleEl.innerHTML = subtitle;
+		// Only update textContent if it differs, to avoid frustrating fast typists.
+		const subtitleText = subtitle ?? '';
+		if ( subtitleEl.textContent !== subtitleText ) {
+			subtitleEl.textContent = subtitleText;
+		}
 	}
 };
 
@@ -56,17 +74,53 @@ const appendSubtitleToTitleDOMElement = ( subtitle, callback ) => {
  */
 const NewspackSubtitlePanel = () => {
 	const subtitle = useSelect( select => select( 'core/editor' ).getEditedPostAttribute( 'meta' )[ META_FIELD_NAME ] );
-	const dispatch = useDispatch();
-	const saveSubtitle = updatedSubtitle => {
-		dispatch( 'core/editor' ).editPost( {
-			meta: {
-				[ META_FIELD_NAME ]: updatedSubtitle,
-			},
-		} );
-	};
+	const { editPost } = useDispatch( 'core/editor' );
+	const saveSubtitle = useCallback(
+		updatedSubtitle => {
+			editPost( {
+				meta: {
+					[ META_FIELD_NAME ]: updatedSubtitle,
+				},
+			} );
+		},
+		[ editPost ]
+	);
+	// Keep current subtitle state visible within effect.
+	const subtitleRef = useRef( subtitle );
+	useEffect( () => {
+		subtitleRef.current = subtitle;
+	}, [ subtitle ] );
+	// Mount effect: poll for canvas, then create element.
+	const timeoutRef = useRef();
 	useEffect( () => {
-		appendSubtitleToTitleDOMElement( subtitle, saveSubtitle );
-	}, [] );
+		let retryCount = 0;
+		const maxRetries = 50; // 5 seconds at 100ms intervals.
+		const tryAppend = () => {
+			const editorDoc = getEditorCanvas();
+			const titleWrapperEl = editorDoc.querySelector( '.edit-post-visual-editor__post-title-wrapper' );
+			if ( titleWrapperEl ) {
+				appendSubtitleToTitleDOMElement( subtitleRef.current, editorDoc, saveSubtitle );
+			} else if ( retryCount < maxRetries ) {
+				retryCount++;
+				timeoutRef.current = setTimeout( tryAppend, 100 );
+			}
+		};
+		tryAppend();
+		return () => {
+			clearTimeout( timeoutRef.current );
+		};
+	}, [] ); // eslint-disable-line react-hooks/exhaustive-deps
+
+	// Sync effect: update element when subtitle changes.
+	// Extracted from appendSubtitleToTitleDOMElement() above.
+	useEffect( () => {
+		const editorDoc = getEditorCanvas();
+		const subtitleEl = editorDoc.getElementById( SUBTITLE_ID );
+		const subtitleText = typeof subtitle === 'string' ? subtitle : '';
+		if ( subtitleEl && subtitleEl.textContent !== subtitleText ) {
+			subtitleEl.textContent = subtitleText;
+		}
+	}, [ subtitle ] );
 };
 
 registerPlugin( 'plugin-document-setting-panel-newspack-subtitle', {

@@ -4,15 +4,18 @@
  * WordPress dependencies
  */
 import { registerBlockType } from '@wordpress/blocks';
+import { useBlockProps } from '@wordpress/block-editor';
 import { __ } from '@wordpress/i18n';
 import { Icon, listView } from '@wordpress/icons';
 import { useEntityProp } from '@wordpress/core-data';
 
 import metadata from './block.json';
 
-const EditComponent = ( { context: { postType, postId } } ) => {
+const EditComponent = ( { context: { postType, postId } = {} } ) => {
+	const blockProps = useBlockProps();
 	const [ postMeta = {} ] = useEntityProp( 'postType', postType, 'meta', postId );
-	return postMeta[ newspack_block_theme_subtitle_block.post_meta_name ] || __( 'Article subtitle', 'newspack-block-theme' );
+	const subtitle = postMeta[ newspack_block_theme_subtitle_block.post_meta_name ] || __( 'Article subtitle', 'newspack-block-theme' );
+	return <p { ...blockProps }>{ subtitle }</p>;
 };
 
 const blockData = {
@@ -22,7 +25,6 @@ const blockData = {
 		foreground: '#36f',
 	},
 	edit: EditComponent,
-	usesContext: [ 'postId', 'postType' ],
 	...metadata,
 };
 

@@ -20,7 +20,7 @@ final class Core {
 	public static function init() {
 		\add_action( 'after_setup_theme', [ __CLASS__, 'theme_support' ] );
 		\add_action( 'wp_enqueue_scripts', [ __CLASS__, 'theme_styles' ] );
-		\add_action( 'enqueue_block_editor_assets', [ __CLASS__, 'editor_scripts' ] );
+		\add_action( 'enqueue_block_assets', [ __CLASS__, 'enqueue_block_assets' ] );
 		\add_filter( 'body_class', [ __CLASS__, 'body_class' ] );
 		\add_filter( 'block_type_metadata', [ __CLASS__, 'block_variations' ] );
 	}
@@ -78,7 +78,10 @@ public static function theme_styles() {
 	/**
 	 * Enqueue editor scripts.
 	 */
-	public static function editor_scripts() {
+	public static function enqueue_block_assets() {
+		if ( ! wp_should_load_block_editor_scripts_and_styles() ) {
+			return;
+		}
 		// Enqueue editor JavaScript.
 		wp_enqueue_script( 'editor-script', get_theme_file_uri( '/dist/editor.js' ), array( 'wp-blocks', 'wp-dom' ), wp_get_theme()->get( 'Version' ), true );
 	}