diff -r 34716fd837a4 -r be944660c56a wp/wp-includes/block-supports/layout.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/block-supports/layout.php	Wed Sep 21 18:19:35 2022 +0200
@@ -0,0 +1,142 @@
+<?php
+/**
+ * Layout block support flag.
+ *
+ * @package WordPress
+ * @since 5.8.0
+ */
+
+/**
+ * Registers the layout block attribute for block types that support it.
+ *
+ * @since 5.8.0
+ * @access private
+ *
+ * @param WP_Block_Type $block_type Block Type.
+ */
+function wp_register_layout_support( $block_type ) {
+	$support_layout = block_has_support( $block_type, array( '__experimentalLayout' ), false );
+	if ( $support_layout ) {
+		if ( ! $block_type->attributes ) {
+			$block_type->attributes = array();
+		}
+
+		if ( ! array_key_exists( 'layout', $block_type->attributes ) ) {
+			$block_type->attributes['layout'] = array(
+				'type' => 'object',
+			);
+		}
+	}
+}
+
+/**
+ * Renders the layout config to the block wrapper.
+ *
+ * @since 5.8.0
+ * @access private
+ *
+ * @param  string $block_content Rendered block content.
+ * @param  array  $block         Block object.
+ * @return string                Filtered block content.
+ */
+function wp_render_layout_support_flag( $block_content, $block ) {
+	$block_type     = WP_Block_Type_Registry::get_instance()->get_registered( $block['blockName'] );
+	$support_layout = block_has_support( $block_type, array( '__experimentalLayout' ), false );
+	if ( ! $support_layout || ! isset( $block['attrs']['layout'] ) ) {
+		return $block_content;
+	}
+
+	$used_layout = $block['attrs']['layout'];
+	if ( isset( $used_layout['inherit'] ) && $used_layout['inherit'] ) {
+		$tree           = WP_Theme_JSON_Resolver::get_merged_data();
+		$default_layout = _wp_array_get( $tree->get_settings(), array( 'layout' ) );
+		if ( ! $default_layout ) {
+			return $block_content;
+		}
+		$used_layout = $default_layout;
+	}
+
+	$id           = uniqid();
+	$content_size = isset( $used_layout['contentSize'] ) ? $used_layout['contentSize'] : null;
+	$wide_size    = isset( $used_layout['wideSize'] ) ? $used_layout['wideSize'] : null;
+
+	$all_max_width_value  = $content_size ? $content_size : $wide_size;
+	$wide_max_width_value = $wide_size ? $wide_size : $content_size;
+
+	// Make sure there is a single CSS rule, and all tags are stripped for security.
+	$all_max_width_value  = safecss_filter_attr( explode( ';', $all_max_width_value )[0] );
+	$wide_max_width_value = safecss_filter_attr( explode( ';', $wide_max_width_value )[0] );
+
+	$style = '';
+	if ( $content_size || $wide_size ) {
+		$style  = ".wp-container-$id > * {";
+		$style .= 'max-width: ' . esc_html( $all_max_width_value ) . ';';
+		$style .= 'margin-left: auto !important;';
+		$style .= 'margin-right: auto !important;';
+		$style .= '}';
+
+		$style .= ".wp-container-$id > .alignwide { max-width: " . esc_html( $wide_max_width_value ) . ';}';
+
+		$style .= ".wp-container-$id .alignfull { max-width: none; }";
+	}
+
+	$style .= ".wp-container-$id .alignleft { float: left; margin-right: 2em; }";
+	$style .= ".wp-container-$id .alignright { float: right; margin-left: 2em; }";
+
+	// This assumes the hook only applies to blocks with a single wrapper.
+	// I think this is a reasonable limitation for that particular hook.
+	$content = preg_replace(
+		'/' . preg_quote( 'class="', '/' ) . '/',
+		'class="wp-container-' . $id . ' ',
+		$block_content,
+		1
+	);
+
+	return $content . '<style>' . $style . '</style>';
+}
+
+// Register the block support.
+WP_Block_Supports::get_instance()->register(
+	'layout',
+	array(
+		'register_attribute' => 'wp_register_layout_support',
+	)
+);
+add_filter( 'render_block', 'wp_render_layout_support_flag', 10, 2 );
+
+/**
+ * For themes without theme.json file, make sure
+ * to restore the inner div for the group block
+ * to avoid breaking styles relying on that div.
+ *
+ * @since 5.8.0
+ * @access private
+ *
+ * @param string $block_content Rendered block content.
+ * @param array  $block         Block object.
+ *
+ * @return string Filtered block content.
+ */
+function wp_restore_group_inner_container( $block_content, $block ) {
+	$group_with_inner_container_regex = '/(^\s*<div\b[^>]*wp-block-group(\s|")[^>]*>)(\s*<div\b[^>]*wp-block-group__inner-container(\s|")[^>]*>)((.|\S|\s)*)/';
+
+	if (
+		'core/group' !== $block['blockName'] ||
+		WP_Theme_JSON_Resolver::theme_has_support() ||
+		1 === preg_match( $group_with_inner_container_regex, $block_content )
+	) {
+		return $block_content;
+	}
+
+	$replace_regex   = '/(^\s*<div\b[^>]*wp-block-group[^>]*>)(.*)(<\/div>\s*$)/ms';
+	$updated_content = preg_replace_callback(
+		$replace_regex,
+		function( $matches ) {
+			return $matches[1] . '<div class="wp-block-group__inner-container">' . $matches[2] . '</div>' . $matches[3];
+		},
+		$block_content
+	);
+	return $updated_content;
+}
+
+add_filter( 'render_block', 'wp_restore_group_inner_container', 10, 2 );