FSE: load content in iframe

lib/client-assets.php

@@ -669,3 +669,40 @@ function gutenberg_extend_block_editor_settings_with_fse_theme_flag( $settings )
 	return $settings;
 }
 add_filter( 'block_editor_settings', 'gutenberg_extend_block_editor_settings_with_fse_theme_flag' );
+
+/**
+ * Sets the editor styles to be consumed by JS.
+ */
+function gutenberg_extend_block_editor_styles_html() {
+	$handles = array(
+		'wp-block-editor',
+		'wp-block-library',
+		'wp-edit-blocks',
+	);
+
+	$block_registry = WP_Block_Type_Registry::get_instance();
+
+	foreach ( $block_registry->get_all_registered() as $block_name => $block_type ) {
+		if ( ! empty( $block_type->style ) ) {
+			$handles[] = $block_type->style;
+		}
+
+		if ( ! empty( $block_type->editor_style ) ) {
+			$handles[] = $block_type->editor_style;
+		}
+	}
+
+	$handles = array_unique( $handles );
+	$done    = wp_styles()->done;
+
+	ob_start();
+
+	wp_styles()->done = array();
+	wp_styles()->do_items( $handles );
+	wp_styles()->done = $done;
+
+	$editor_styles = wp_json_encode( array( 'html' => ob_get_clean() ) );
+
+	echo "<script>window.__editorStyles = $editor_styles</script>";
+}
+add_action( 'admin_footer-toplevel_page_gutenberg-edit-site', 'gutenberg_extend_block_editor_styles_html' );

packages/block-editor/package.json

@@ -60,6 +60,7 @@
 		"lodash": "^4.17.19",
 		"memize": "^1.1.0",
 		"react-autosize-textarea": "^7.1.0",
+		"react-merge-refs": "^1.0.0",
 		"react-spring": "^8.0.19",
 		"reakit": "1.3.4",
 		"redux-multi": "^0.1.12",

packages/block-editor/src/components/block-list/block-popover.js

@@ -167,7 +167,13 @@ function BlockPopover( {
 		: 'top right left';
 	const stickyBoundaryElement = showEmptyBlockSideInserter
 		? undefined
-		: getScrollContainer( node ) || ownerDocument.body;
+		: // The sticky boundary element should be the boundary at which the
+		  // the block toolbar becomes sticky when the block scolls out of view.
+		  // In case of an iframe, this should be the iframe boundary, otherwise
+		  // the scroll container.
+		  ownerDocument.defaultView.frameElement ||
+		  getScrollContainer( node ) ||
+		  ownerDocument.body;
 
 	return (
 		<Popover

packages/block-editor/src/components/block-list/block-selection-button.js

@@ -223,6 +223,12 @@ function BlockSelectionButton( { clientId, rootClientId, blockElement } ) {
 
 				if ( navigateDown ) {
 					nextTabbable = focus.tabbable.findNext( blockElement );
+
+					if ( ! nextTabbable ) {
+						nextTabbable =
+							blockElement.ownerDocument.defaultView.frameElement;
+						nextTabbable = focus.tabbable.findNext( nextTabbable );
+					}
 				} else {
 					nextTabbable = focus.tabbable.findPrevious( blockElement );
 				}

packages/block-editor/src/components/iframe/index.js

@@ -0,0 +1,189 @@
+/**
+ * External dependencies
+ */
+import mergeRefs from 'react-merge-refs';
+
+/**
+ * WordPress dependencies
+ */
+import {
+	useState,
+	createPortal,
+	useCallback,
+	forwardRef,
+} from '@wordpress/element';
+import { __ } from '@wordpress/i18n';
+
+const BODY_CLASS_NAME = 'editor-styles-wrapper';
+const BLOCK_PREFIX = 'wp-block';
+
+/**
+ * Clones stylesheets targetting the editor canvas to the given document. A
+ * stylesheet is considered targetting the editor a canvas if it contains the
+ * `editor-styles-wrapper`, `wp-block`, or `wp-block-*` class selectors.
+ *
+ * Ideally, this hook should be removed in the future and styles should be added
+ * explicitly as editor styles.
+ *
+ * @param {Document} doc The document to append cloned stylesheets to.
+ */
+function styleSheetsCompat( doc ) {
+	// Search the document for stylesheets targetting the editor canvas.
+	Array.from( document.styleSheets ).forEach( ( styleSheet ) => {
+		try {
+			// May fail for external styles.
+			// eslint-disable-next-line no-unused-expressions
+			styleSheet.cssRules;
+		} catch ( e ) {
+			return;
+		}
+
+		const { ownerNode, cssRules } = styleSheet;
+
+		if ( ! cssRules ) {
+			return;
+		}
+
+		const isMatch = Array.from( cssRules ).find(
+			( { selectorText } ) =>
+				selectorText &&
+				( selectorText.includes( `.${ BODY_CLASS_NAME }` ) ||
+					selectorText.includes( `.${ BLOCK_PREFIX }` ) )
+		);
+
+		if ( isMatch && ! doc.getElementById( ownerNode.id ) ) {
+			doc.head.appendChild( ownerNode.cloneNode( true ) );
+		}
+	} );
+}
+
+/**
+ * Bubbles some event types (keydown, keypress, and dragover) to parent document
+ * document to ensure that the keyboard shortcuts and drag and drop work.
+ *
+ * Ideally, we should remove event bubbling in the future. Keyboard shortcuts
+ * should be context dependent, e.g. actions on blocks like Cmd+A should not
+ * work globally outside the block editor.
+ *
+ * @param {Document} doc Document to attach listeners to.
+ */
+function bubbleEvents( doc ) {
+	const { defaultView } = doc;
+	const { frameElement } = defaultView;
+
+	function bubbleEvent( event ) {
+		const prototype = Object.getPrototypeOf( event );
+		const constructorName = prototype.constructor.name;
+		const Constructor = window[ constructorName ];
+
+		const init = {};
+
+		for ( const key in event ) {
+			init[ key ] = event[ key ];
+		}
+
+		if ( event instanceof defaultView.MouseEvent ) {
+			const rect = frameElement.getBoundingClientRect();
+			init.clientX += rect.left;
+			init.clientY += rect.top;
+		}
+
+		const newEvent = new Constructor( event.type, init );
+		const cancelled = ! frameElement.dispatchEvent( newEvent );
+
+		if ( cancelled ) {
+			event.preventDefault();
+		}
+	}
+
+	const eventTypes = [ 'keydown', 'keypress', 'dragover' ];
+
+	for ( const name of eventTypes ) {
+		doc.addEventListener( name, bubbleEvent );
+	}
+}
+
+/**
+ * Sets the document direction.
+ *
+ * Sets the `editor-styles-wrapper` class name on the body.
+ *
+ * Copies the `admin-color-*` class name to the body so that the admin color
+ * scheme applies to components in the iframe.
+ *
+ * @param {Document} doc Document to add class name to.
+ */
+function setBodyClassName( doc ) {
+	doc.dir = document.dir;
+	doc.body.className = BODY_CLASS_NAME;
+
+	for ( const name of document.body.classList ) {
+		if ( name.startsWith( 'admin-color-' ) ) {
+			doc.body.classList.add( name );
+		}
+	}
+}
+
+/**
+ * Sets the document head and default styles.
+ *
+ * @param {Document} doc  Document to set the head for.
+ * @param {string}   head HTML to set as the head.
+ */
+function setHead( doc, head ) {
+	doc.head.innerHTML =
+		// Body margin must be overridable by themes.
+		'<style>body{margin:0}</style>' + head;
+}
+
+function Iframe( { contentRef, children, head, ...props }, ref ) {
+	const [ iframeDocument, setIframeDocument ] = useState();
+
+	const setRef = useCallback( ( node ) => {
+		if ( ! node ) {
+			return;
+		}
+
+		function setDocumentIfReady() {
+			const { contentDocument } = node;
+			const { readyState } = contentDocument;
+
+			if ( readyState !== 'interactive' && readyState !== 'complete' ) {
+				return false;
+			}
+
+			setIframeDocument( contentDocument );
+			setHead( contentDocument, head );
+			setBodyClassName( contentDocument );
+			styleSheetsCompat( contentDocument );
+			bubbleEvents( contentDocument );
+			setBodyClassName( contentDocument );
+			contentRef.current = contentDocument.body;
+
+			return true;
+		}
+
+		if ( setDocumentIfReady() ) {
+			return;
+		}
+
+		// Document is not immediately loaded in Firefox.
+		node.addEventListener( 'load', () => {
+			setDocumentIfReady();
+		} );
+	}, [] );
+
+	return (
+		<iframe
+			{ ...props }
+			ref={ useCallback( mergeRefs( [ ref, setRef ] ), [] ) }
+			tabIndex="0"
+			title={ __( 'Editor canvas' ) }
+			name="editor-canvas"
+		>
+			{ iframeDocument && createPortal( children, iframeDocument.body ) }
+		</iframe>
+	);
+}
+
+export default forwardRef( Iframe );

packages/block-editor/src/components/index.js

@@ -108,6 +108,7 @@ export { default as NavigableToolbar } from './navigable-toolbar';
 export {
 	default as ObserveTyping,
 	useTypingObserver as __unstableUseTypingObserver,
+	useMouseMoveTypingReset as __unstableUseMouseMoveTypingReset,
 } from './observe-typing';
 export { default as PreserveScrollInReorder } from './preserve-scroll-in-reorder';
 export { default as SkipToSelectedBlock } from './skip-to-selected-block';
@@ -119,6 +120,7 @@ export { default as Warning } from './warning';
 export { default as WritingFlow } from './writing-flow';
 export { useCanvasClickRedirect as __unstableUseCanvasClickRedirect } from './use-canvas-click-redirect';
 export { default as useBlockDisplayInformation } from './use-block-display-information';
+export { default as __unstableIframe } from './iframe';
 
 /*
  * State Related Components