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-admin/site-editor.php

@@ -0,0 +1,115 @@
+<?php
+/**
+ * Site Editor administration screen.
+ *
+ * @package WordPress
+ * @subpackage Administration
+ */
+
+global $post, $editor_styles;
+
+/** WordPress Administration Bootstrap */
+require_once __DIR__ . '/admin.php';
+
+if ( ! current_user_can( 'edit_theme_options' ) ) {
+	wp_die(
+		'<h1>' . __( 'You need a higher level of permission.' ) . '</h1>' .
+		'<p>' . __( 'Sorry, you are not allowed to edit theme options on this site.' ) . '</p>',
+		403
+	);
+}
+
+if ( ! wp_is_block_template_theme() ) {
+	wp_die( __( 'The theme you are currently using is not compatible with Full Site Editing.' ) );
+}
+
+// Used in the HTML title tag.
+$title       = __( 'Editor (beta)' );
+$parent_file = 'themes.php';
+
+// Flag that we're loading the block editor.
+$current_screen = get_current_screen();
+$current_screen->is_block_editor( true );
+
+$block_editor_context = new WP_Block_Editor_Context();
+
+$active_global_styles_id = WP_Theme_JSON_Resolver::get_user_custom_post_type_id();
+$active_theme            = wp_get_theme()->get_stylesheet();
+$preload_paths           = array(
+	array( '/wp/v2/media', 'OPTIONS' ),
+	'/',
+	'/wp/v2/types?context=edit',
+	'/wp/v2/taxonomies?context=edit',
+	'/wp/v2/pages?context=edit',
+	'/wp/v2/categories?context=edit',
+	'/wp/v2/posts?context=edit',
+	'/wp/v2/tags?context=edit',
+	'/wp/v2/templates?context=edit',
+	'/wp/v2/template-parts?context=edit',
+	'/wp/v2/settings',
+	'/wp/v2/themes?context=edit&status=active',
+	'/wp/v2/global-styles/' . $active_global_styles_id . '?context=edit',
+	'/wp/v2/global-styles/' . $active_global_styles_id,
+	'/wp/v2/themes/' . $active_theme . '/global-styles',
+);
+block_editor_rest_api_preload( $preload_paths, $block_editor_context );
+
+$editor_settings = get_block_editor_settings(
+	array(
+		'siteUrl'                              => site_url(),
+		'postsPerPage'                         => get_option( 'posts_per_page' ),
+		'styles'                               => get_block_editor_theme_styles(),
+		'defaultTemplateTypes'                 => get_default_block_template_types(),
+		'defaultTemplatePartAreas'             => get_allowed_block_template_part_areas(),
+		'__experimentalBlockPatterns'          => WP_Block_Patterns_Registry::get_instance()->get_all_registered(),
+		'__experimentalBlockPatternCategories' => WP_Block_Pattern_Categories_Registry::get_instance()->get_all_registered(),
+	),
+	$block_editor_context
+);
+
+wp_add_inline_script(
+	'wp-edit-site',
+	sprintf(
+		'wp.domReady( function() {
+			wp.editSite.initialize( "site-editor", %s );
+		} );',
+		wp_json_encode( $editor_settings )
+	)
+);
+
+// Preload server-registered block schemas.
+wp_add_inline_script(
+	'wp-blocks',
+	'wp.blocks.unstable__bootstrapServerSideBlockDefinitions(' . wp_json_encode( get_block_editor_server_block_settings() ) . ');'
+);
+
+wp_add_inline_script(
+	'wp-blocks',
+	sprintf( 'wp.blocks.setCategories( %s );', wp_json_encode( get_block_categories( $post ) ) ),
+	'after'
+);
+
+wp_enqueue_script( 'wp-edit-site' );
+wp_enqueue_script( 'wp-format-library' );
+wp_enqueue_style( 'wp-edit-site' );
+wp_enqueue_style( 'wp-format-library' );
+wp_enqueue_media();
+
+if (
+	current_theme_supports( 'wp-block-styles' ) ||
+	( ! is_array( $editor_styles ) || count( $editor_styles ) === 0 )
+) {
+	wp_enqueue_style( 'wp-block-library-theme' );
+}
+
+/** This action is documented in wp-admin/edit-form-blocks.php */
+do_action( 'enqueue_block_editor_assets' );
+
+require_once ABSPATH . 'wp-admin/admin-header.php';
+?>
+
+<div id="site-editor" class="edit-site"></div>
+
+<?php
+
+require_once ABSPATH . 'wp-admin/admin-footer.php';