Add Site Editor and PHP changes from Gutenberg 10.1 - 11.9

- First pass at adding the site editor from the Gutenberg plugin to
  wp-admin/site-editor.php.
- Adds miscellaneous PHP changes from Gutenberg 10.1 - 11.9.

Follows [52042].
See #54337.
Props youknowriad, aristath, hellofromtonya, gziolo.


git-svn-id: https://develop.svn.wordpress.org/trunk@52069 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/blocks.php

@@ -1182,3 +1182,117 @@ function get_query_pagination_arrow( $block, $is_next ) {
 	}
 	return null;
 }
+
+/**
+ * Enqueue a stylesheet for a specific block.
+ *
+ * If the theme has opted-in to separate-styles loading,
+ * then the stylesheet will be enqueued on-render,
+ * otherwise when the block inits.
+ *
+ * @param string $block_name The block-name, including namespace.
+ * @param array  $args       An array of arguments [handle,src,deps,ver,media].
+ *
+ * @return void
+ */
+function wp_enqueue_block_style( $block_name, $args ) {
+	$args = wp_parse_args(
+		$args,
+		array(
+			'handle' => '',
+			'src'    => '',
+			'deps'   => array(),
+			'ver'    => false,
+			'media'  => 'all',
+		)
+	);
+
+	/**
+	 * Callback function to register and enqueue styles.
+	 *
+	 * @param string $content When the callback is used for the render_block filter,
+	 *                        the content needs to be returned so the function parameter
+	 *                        is to ensure the content exists.
+	 *
+	 * @return string
+	 */
+	$callback = static function( $content ) use ( $args ) {
+		// Register the stylesheet.
+		if ( ! empty( $args['src'] ) ) {
+			wp_register_style( $args['handle'], $args['src'], $args['deps'], $args['ver'], $args['media'] );
+		}
+
+		// Add `path` data if provided.
+		if ( isset( $args['path'] ) ) {
+			wp_style_add_data( $args['handle'], 'path', $args['path'] );
+
+			// Get the RTL file path.
+			$rtl_file_path = str_replace( '.css', '-rtl.css', $args['path'] );
+
+			// Add RTL stylesheet.
+			if ( file_exists( $rtl_file_path ) ) {
+				wp_style_add_data( $args['hanle'], 'rtl', 'replace' );
+
+				if ( is_rtl() ) {
+					wp_style_add_data( $args['handle'], 'path', $rtl_file_path );
+				}
+			}
+		}
+
+		// Enqueue the stylesheet.
+		wp_enqueue_style( $args['handle'] );
+
+		return $content;
+	};
+
+	$hook = did_action( 'wp_enqueue_scripts' ) ? 'wp_footer' : 'wp_enqueue_scripts';
+	if ( wp_should_load_separate_core_block_assets() ) {
+		$hook = "render_block_$block_name";
+	}
+
+	/*
+	 * The filter's callback here is an anonymous function because
+	 * using a named function in this case is not possible.
+	 *
+	 * The function cannot be unhooked, however, users are still able
+	 * to dequeue the stylesheets registered/enqueued by the callback
+	 * which is why in this case, using an anonymous function
+	 * was deemed acceptable.
+	 */
+	add_filter( $hook, $callback );
+
+	// Enqueue assets in the editor.
+	add_action( 'enqueue_block_assets', $callback );
+}
+
+/**
+ * Allow multiple block styles.
+ *
+ * @param array $metadata Metadata for registering a block type.
+ *
+ * @return array
+ */
+function _wp_multiple_block_styles( $metadata ) {
+	foreach ( array( 'style', 'editorStyle' ) as $key ) {
+		if ( ! empty( $metadata[ $key ] ) && is_array( $metadata[ $key ] ) ) {
+			$default_style = array_shift( $metadata[ $key ] );
+			foreach ( $metadata[ $key ] as $handle ) {
+				$args = array( 'handle' => $handle );
+				if ( 0 === strpos( $handle, 'file:' ) && isset( $metadata['file'] ) ) {
+					$style_path = remove_block_asset_path_prefix( $handle );
+					$args       = array(
+						'handle' => sanitize_key( "{$metadata['name']}-{$style_path}" ),
+						'src'    => plugins_url( $style_path, $metadata['file'] ),
+					);
+				}
+
+				wp_enqueue_block_style( $metadata['name'], $args );
+			}
+
+			// Only return the 1st item in the array.
+			$metadata[ $key ] = $default_style;
+		}
+	}
+	return $metadata;
+}
+add_filter( 'block_type_metadata', '_wp_multiple_block_styles' );