Adding upstream version 6.4.3+dfsg1.upstream/6.4.3+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2229 insertions, 0 deletions

diff --git a/wp-includes/class-wp-customize-widgets.php b/wp-includes/class-wp-customize-widgets.php
new file mode 100644
index 0000000..c8a00c7
--- /dev/null
+++ b/wp-includes/class-wp-customize-widgets.php
@@ -0,0 +1,2229 @@
+<?php
+/**
+ * WordPress Customize Widgets classes
+ *
+ * @package WordPress
+ * @subpackage Customize
+ * @since 3.9.0
+ */
+
+/**
+ * Customize Widgets class.
+ *
+ * Implements widget management in the Customizer.
+ *
+ * @since 3.9.0
+ *
+ * @see WP_Customize_Manager
+ */
+#[AllowDynamicProperties]
+final class WP_Customize_Widgets {
+
+	/**
+	 * WP_Customize_Manager instance.
+	 *
+	 * @since 3.9.0
+	 * @var WP_Customize_Manager
+	 */
+	public $manager;
+
+	/**
+	 * All id_bases for widgets defined in core.
+	 *
+	 * @since 3.9.0
+	 * @var array
+	 */
+	protected $core_widget_id_bases = array(
+		'archives',
+		'calendar',
+		'categories',
+		'custom_html',
+		'links',
+		'media_audio',
+		'media_image',
+		'media_video',
+		'meta',
+		'nav_menu',
+		'pages',
+		'recent-comments',
+		'recent-posts',
+		'rss',
+		'search',
+		'tag_cloud',
+		'text',
+	);
+
+	/**
+	 * @since 3.9.0
+	 * @var array
+	 */
+	protected $rendered_sidebars = array();
+
+	/**
+	 * @since 3.9.0
+	 * @var array
+	 */
+	protected $rendered_widgets = array();
+
+	/**
+	 * @since 3.9.0
+	 * @var array
+	 */
+	protected $old_sidebars_widgets = array();
+
+	/**
+	 * Mapping of widget ID base to whether it supports selective refresh.
+	 *
+	 * @since 4.5.0
+	 * @var array
+	 */
+	protected $selective_refreshable_widgets;
+
+	/**
+	 * Mapping of setting type to setting ID pattern.
+	 *
+	 * @since 4.2.0
+	 * @var array
+	 */
+	protected $setting_id_patterns = array(
+		'widget_instance' => '/^widget_(?P<id_base>.+?)(?:\[(?P<widget_number>\d+)\])?$/',
+		'sidebar_widgets' => '/^sidebars_widgets\[(?P<sidebar_id>.+?)\]$/',
+	);
+
+	/**
+	 * Initial loader.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param WP_Customize_Manager $manager Customizer bootstrap instance.
+	 */
+	public function __construct( $manager ) {
+		$this->manager = $manager;
+
+		// See https://github.com/xwp/wp-customize-snapshots/blob/962586659688a5b1fd9ae93618b7ce2d4e7a421c/php/class-customize-snapshot-manager.php#L420-L449
+		add_filter( 'customize_dynamic_setting_args', array( $this, 'filter_customize_dynamic_setting_args' ), 10, 2 );
+		add_action( 'widgets_init', array( $this, 'register_settings' ), 95 );
+		add_action( 'customize_register', array( $this, 'schedule_customize_register' ), 1 );
+
+		// Skip remaining hooks when the user can't manage widgets anyway.
+		if ( ! current_user_can( 'edit_theme_options' ) ) {
+			return;
+		}
+
+		add_action( 'wp_loaded', array( $this, 'override_sidebars_widgets_for_theme_switch' ) );
+		add_action( 'customize_controls_init', array( $this, 'customize_controls_init' ) );
+		add_action( 'customize_controls_enqueue_scripts', array( $this, 'enqueue_scripts' ) );
+		add_action( 'customize_controls_print_styles', array( $this, 'print_styles' ) );
+		add_action( 'customize_controls_print_scripts', array( $this, 'print_scripts' ) );
+		add_action( 'customize_controls_print_footer_scripts', array( $this, 'print_footer_scripts' ) );
+		add_action( 'customize_controls_print_footer_scripts', array( $this, 'output_widget_control_templates' ) );
+		add_action( 'customize_preview_init', array( $this, 'customize_preview_init' ) );
+		add_filter( 'customize_refresh_nonces', array( $this, 'refresh_nonces' ) );
+		add_filter( 'should_load_block_editor_scripts_and_styles', array( $this, 'should_load_block_editor_scripts_and_styles' ) );
+
+		add_action( 'dynamic_sidebar', array( $this, 'tally_rendered_widgets' ) );
+		add_filter( 'is_active_sidebar', array( $this, 'tally_sidebars_via_is_active_sidebar_calls' ), 10, 2 );
+		add_filter( 'dynamic_sidebar_has_widgets', array( $this, 'tally_sidebars_via_dynamic_sidebar_calls' ), 10, 2 );
+
+		// Selective Refresh.
+		add_filter( 'customize_dynamic_partial_args', array( $this, 'customize_dynamic_partial_args' ), 10, 2 );
+		add_action( 'customize_preview_init', array( $this, 'selective_refresh_init' ) );
+	}
+
+	/**
+	 * List whether each registered widget can be use selective refresh.
+	 *
+	 * If the theme does not support the customize-selective-refresh-widgets feature,
+	 * then this will always return an empty array.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @global WP_Widget_Factory $wp_widget_factory
+	 *
+	 * @return array Mapping of id_base to support. If theme doesn't support
+	 *               selective refresh, an empty array is returned.
+	 */
+	public function get_selective_refreshable_widgets() {
+		global $wp_widget_factory;
+		if ( ! current_theme_supports( 'customize-selective-refresh-widgets' ) ) {
+			return array();
+		}
+		if ( ! isset( $this->selective_refreshable_widgets ) ) {
+			$this->selective_refreshable_widgets = array();
+			foreach ( $wp_widget_factory->widgets as $wp_widget ) {
+				$this->selective_refreshable_widgets[ $wp_widget->id_base ] = ! empty( $wp_widget->widget_options['customize_selective_refresh'] );
+			}
+		}
+		return $this->selective_refreshable_widgets;
+	}
+
+	/**
+	 * Determines if a widget supports selective refresh.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param string $id_base Widget ID Base.
+	 * @return bool Whether the widget can be selective refreshed.
+	 */
+	public function is_widget_selective_refreshable( $id_base ) {
+		$selective_refreshable_widgets = $this->get_selective_refreshable_widgets();
+		return ! empty( $selective_refreshable_widgets[ $id_base ] );
+	}
+
+	/**
+	 * Retrieves the widget setting type given a setting ID.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param string $setting_id Setting ID.
+	 * @return string|void Setting type.
+	 */
+	protected function get_setting_type( $setting_id ) {
+		static $cache = array();
+		if ( isset( $cache[ $setting_id ] ) ) {
+			return $cache[ $setting_id ];
+		}
+		foreach ( $this->setting_id_patterns as $type => $pattern ) {
+			if ( preg_match( $pattern, $setting_id ) ) {
+				$cache[ $setting_id ] = $type;
+				return $type;
+			}
+		}
+	}
+
+	/**
+	 * Inspects the incoming customized data for any widget settings, and dynamically adds
+	 * them up-front so widgets will be initialized properly.
+	 *
+	 * @since 4.2.0
+	 */
+	public function register_settings() {
+		$widget_setting_ids   = array();
+		$incoming_setting_ids = array_keys( $this->manager->unsanitized_post_values() );
+		foreach ( $incoming_setting_ids as $setting_id ) {
+			if ( ! is_null( $this->get_setting_type( $setting_id ) ) ) {
+				$widget_setting_ids[] = $setting_id;
+			}
+		}
+		if ( $this->manager->doing_ajax( 'update-widget' ) && isset( $_REQUEST['widget-id'] ) ) {
+			$widget_setting_ids[] = $this->get_setting_id( wp_unslash( $_REQUEST['widget-id'] ) );
+		}
+
+		$settings = $this->manager->add_dynamic_settings( array_unique( $widget_setting_ids ) );
+
+		if ( $this->manager->settings_previewed() ) {
+			foreach ( $settings as $setting ) {
+				$setting->preview();
+			}
+		}
+	}
+
+	/**
+	 * Determines the arguments for a dynamically-created setting.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param false|array $args       The arguments to the WP_Customize_Setting constructor.
+	 * @param string      $setting_id ID for dynamic setting, usually coming from `$_POST['customized']`.
+	 * @return array|false Setting arguments, false otherwise.
+	 */
+	public function filter_customize_dynamic_setting_args( $args, $setting_id ) {
+		if ( $this->get_setting_type( $setting_id ) ) {
+			$args = $this->get_setting_args( $setting_id );
+		}
+		return $args;
+	}
+
+	/**
+	 * Retrieves an unslashed post value or return a default.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $name          Post value.
+	 * @param mixed  $default_value Default post value.
+	 * @return mixed Unslashed post value or default value.
+	 */
+	protected function get_post_value( $name, $default_value = null ) {
+		if ( ! isset( $_POST[ $name ] ) ) {
+			return $default_value;
+		}
+
+		return wp_unslash( $_POST[ $name ] );
+	}
+
+	/**
+	 * Override sidebars_widgets for theme switch.
+	 *
+	 * When switching a theme via the Customizer, supply any previously-configured
+	 * sidebars_widgets from the target theme as the initial sidebars_widgets
+	 * setting. Also store the old theme's existing settings so that they can
+	 * be passed along for storing in the sidebars_widgets theme_mod when the
+	 * theme gets switched.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $sidebars_widgets
+	 * @global array $_wp_sidebars_widgets
+	 */
+	public function override_sidebars_widgets_for_theme_switch() {
+		global $sidebars_widgets;
+
+		if ( $this->manager->doing_ajax() || $this->manager->is_theme_active() ) {
+			return;
+		}
+
+		$this->old_sidebars_widgets = wp_get_sidebars_widgets();
+		add_filter( 'customize_value_old_sidebars_widgets_data', array( $this, 'filter_customize_value_old_sidebars_widgets_data' ) );
+		$this->manager->set_post_value( 'old_sidebars_widgets_data', $this->old_sidebars_widgets ); // Override any value cached in changeset.
+
+		// retrieve_widgets() looks at the global $sidebars_widgets.
+		$sidebars_widgets = $this->old_sidebars_widgets;
+		$sidebars_widgets = retrieve_widgets( 'customize' );
+		add_filter( 'option_sidebars_widgets', array( $this, 'filter_option_sidebars_widgets_for_theme_switch' ), 1 );
+		// Reset global cache var used by wp_get_sidebars_widgets().
+		unset( $GLOBALS['_wp_sidebars_widgets'] );
+	}
+
+	/**
+	 * Filters old_sidebars_widgets_data Customizer setting.
+	 *
+	 * When switching themes, filter the Customizer setting old_sidebars_widgets_data
+	 * to supply initial $sidebars_widgets before they were overridden by retrieve_widgets().
+	 * The value for old_sidebars_widgets_data gets set in the old theme's sidebars_widgets
+	 * theme_mod.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @see WP_Customize_Widgets::handle_theme_switch()
+	 *
+	 * @param array $old_sidebars_widgets
+	 * @return array
+	 */
+	public function filter_customize_value_old_sidebars_widgets_data( $old_sidebars_widgets ) {
+		return $this->old_sidebars_widgets;
+	}
+
+	/**
+	 * Filters sidebars_widgets option for theme switch.
+	 *
+	 * When switching themes, the retrieve_widgets() function is run when the Customizer initializes,
+	 * and then the new sidebars_widgets here get supplied as the default value for the sidebars_widgets
+	 * option.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @see WP_Customize_Widgets::handle_theme_switch()
+	 * @global array $sidebars_widgets
+	 *
+	 * @param array $sidebars_widgets
+	 * @return array
+	 */
+	public function filter_option_sidebars_widgets_for_theme_switch( $sidebars_widgets ) {
+		$sidebars_widgets                  = $GLOBALS['sidebars_widgets'];
+		$sidebars_widgets['array_version'] = 3;
+		return $sidebars_widgets;
+	}
+
+	/**
+	 * Ensures all widgets get loaded into the Customizer.
+	 *
+	 * Note: these actions are also fired in wp_ajax_update_widget().
+	 *
+	 * @since 3.9.0
+	 */
+	public function customize_controls_init() {
+		/** This action is documented in wp-admin/includes/ajax-actions.php */
+		do_action( 'load-widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/includes/ajax-actions.php */
+		do_action( 'widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/widgets.php */
+		do_action( 'sidebar_admin_setup' );
+	}
+
+	/**
+	 * Ensures widgets are available for all types of previews.
+	 *
+	 * When in preview, hook to {@see 'customize_register'} for settings after WordPress is loaded
+	 * so that all filters have been initialized (e.g. Widget Visibility).
+	 *
+	 * @since 3.9.0
+	 */
+	public function schedule_customize_register() {
+		if ( is_admin() ) {
+			$this->customize_register();
+		} else {
+			add_action( 'wp', array( $this, 'customize_register' ) );
+		}
+	}
+
+	/**
+	 * Registers Customizer settings and controls for all sidebars and widgets.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_widgets
+	 * @global array $wp_registered_widget_controls
+	 * @global array $wp_registered_sidebars
+	 */
+	public function customize_register() {
+		global $wp_registered_widgets, $wp_registered_widget_controls, $wp_registered_sidebars;
+
+		$use_widgets_block_editor = wp_use_widgets_block_editor();
+
+		add_filter( 'sidebars_widgets', array( $this, 'preview_sidebars_widgets' ), 1 );
+
+		$sidebars_widgets = array_merge(
+			array( 'wp_inactive_widgets' => array() ),
+			array_fill_keys( array_keys( $wp_registered_sidebars ), array() ),
+			wp_get_sidebars_widgets()
+		);
+
+		$new_setting_ids = array();
+
+		/*
+		 * Register a setting for all widgets, including those which are active,
+		 * inactive, and orphaned since a widget may get suppressed from a sidebar
+		 * via a plugin (like Widget Visibility).
+		 */
+		foreach ( array_keys( $wp_registered_widgets ) as $widget_id ) {
+			$setting_id   = $this->get_setting_id( $widget_id );
+			$setting_args = $this->get_setting_args( $setting_id );
+			if ( ! $this->manager->get_setting( $setting_id ) ) {
+				$this->manager->add_setting( $setting_id, $setting_args );
+			}
+			$new_setting_ids[] = $setting_id;
+		}
+
+		/*
+		 * Add a setting which will be supplied for the theme's sidebars_widgets
+		 * theme_mod when the theme is switched.
+		 */
+		if ( ! $this->manager->is_theme_active() ) {
+			$setting_id   = 'old_sidebars_widgets_data';
+			$setting_args = $this->get_setting_args(
+				$setting_id,
+				array(
+					'type'  => 'global_variable',
+					'dirty' => true,
+				)
+			);
+			$this->manager->add_setting( $setting_id, $setting_args );
+		}
+
+		$this->manager->add_panel(
+			'widgets',
+			array(
+				'type'                     => 'widgets',
+				'title'                    => __( 'Widgets' ),
+				'description'              => __( 'Widgets are independent sections of content that can be placed into widgetized areas provided by your theme (commonly called sidebars).' ),
+				'priority'                 => 110,
+				'active_callback'          => array( $this, 'is_panel_active' ),
+				'auto_expand_sole_section' => true,
+				'theme_supports'           => 'widgets',
+			)
+		);
+
+		foreach ( $sidebars_widgets as $sidebar_id => $sidebar_widget_ids ) {
+			if ( empty( $sidebar_widget_ids ) ) {
+				$sidebar_widget_ids = array();
+			}
+
+			$is_registered_sidebar = is_registered_sidebar( $sidebar_id );
+			$is_inactive_widgets   = ( 'wp_inactive_widgets' === $sidebar_id );
+			$is_active_sidebar     = ( $is_registered_sidebar && ! $is_inactive_widgets );
+
+			// Add setting for managing the sidebar's widgets.
+			if ( $is_registered_sidebar || $is_inactive_widgets ) {
+				$setting_id   = sprintf( 'sidebars_widgets[%s]', $sidebar_id );
+				$setting_args = $this->get_setting_args( $setting_id );
+				if ( ! $this->manager->get_setting( $setting_id ) ) {
+					if ( ! $this->manager->is_theme_active() ) {
+						$setting_args['dirty'] = true;
+					}
+					$this->manager->add_setting( $setting_id, $setting_args );
+				}
+				$new_setting_ids[] = $setting_id;
+
+				// Add section to contain controls.
+				$section_id = sprintf( 'sidebar-widgets-%s', $sidebar_id );
+				if ( $is_active_sidebar ) {
+
+					$section_args = array(
+						'title'      => $wp_registered_sidebars[ $sidebar_id ]['name'],
+						'priority'   => array_search( $sidebar_id, array_keys( $wp_registered_sidebars ), true ),
+						'panel'      => 'widgets',
+						'sidebar_id' => $sidebar_id,
+					);
+
+					if ( $use_widgets_block_editor ) {
+						$section_args['description'] = '';
+					} else {
+						$section_args['description'] = $wp_registered_sidebars[ $sidebar_id ]['description'];
+					}
+
+					/**
+					 * Filters Customizer widget section arguments for a given sidebar.
+					 *
+					 * @since 3.9.0
+					 *
+					 * @param array      $section_args Array of Customizer widget section arguments.
+					 * @param string     $section_id   Customizer section ID.
+					 * @param int|string $sidebar_id   Sidebar ID.
+					 */
+					$section_args = apply_filters( 'customizer_widgets_section_args', $section_args, $section_id, $sidebar_id );
+
+					$section = new WP_Customize_Sidebar_Section( $this->manager, $section_id, $section_args );
+					$this->manager->add_section( $section );
+
+					if ( $use_widgets_block_editor ) {
+						$control = new WP_Sidebar_Block_Editor_Control(
+							$this->manager,
+							$setting_id,
+							array(
+								'section'     => $section_id,
+								'sidebar_id'  => $sidebar_id,
+								'label'       => $section_args['title'],
+								'description' => $section_args['description'],
+							)
+						);
+					} else {
+						$control = new WP_Widget_Area_Customize_Control(
+							$this->manager,
+							$setting_id,
+							array(
+								'section'    => $section_id,
+								'sidebar_id' => $sidebar_id,
+								'priority'   => count( $sidebar_widget_ids ), // place 'Add Widget' and 'Reorder' buttons at end.
+							)
+						);
+					}
+
+					$this->manager->add_control( $control );
+
+					$new_setting_ids[] = $setting_id;
+				}
+			}
+
+			if ( ! $use_widgets_block_editor ) {
+				// Add a control for each active widget (located in a sidebar).
+				foreach ( $sidebar_widget_ids as $i => $widget_id ) {
+
+					// Skip widgets that may have gone away due to a plugin being deactivated.
+					if ( ! $is_active_sidebar || ! isset( $wp_registered_widgets[ $widget_id ] ) ) {
+						continue;
+					}
+
+					$registered_widget = $wp_registered_widgets[ $widget_id ];
+					$setting_id        = $this->get_setting_id( $widget_id );
+					$id_base           = $wp_registered_widget_controls[ $widget_id ]['id_base'];
+
+					$control = new WP_Widget_Form_Customize_Control(
+						$this->manager,
+						$setting_id,
+						array(
+							'label'          => $registered_widget['name'],
+							'section'        => $section_id,
+							'sidebar_id'     => $sidebar_id,
+							'widget_id'      => $widget_id,
+							'widget_id_base' => $id_base,
+							'priority'       => $i,
+							'width'          => $wp_registered_widget_controls[ $widget_id ]['width'],
+							'height'         => $wp_registered_widget_controls[ $widget_id ]['height'],
+							'is_wide'        => $this->is_wide_widget( $widget_id ),
+						)
+					);
+					$this->manager->add_control( $control );
+				}
+			}
+		}
+
+		if ( $this->manager->settings_previewed() ) {
+			foreach ( $new_setting_ids as $new_setting_id ) {
+				$this->manager->get_setting( $new_setting_id )->preview();
+			}
+		}
+	}
+
+	/**
+	 * Determines whether the widgets panel is active, based on whether there are sidebars registered.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @see WP_Customize_Panel::$active_callback
+	 *
+	 * @global array $wp_registered_sidebars
+	 * @return bool Active.
+	 */
+	public function is_panel_active() {
+		global $wp_registered_sidebars;
+		return ! empty( $wp_registered_sidebars );
+	}
+
+	/**
+	 * Converts a widget_id into its corresponding Customizer setting ID (option name).
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $widget_id Widget ID.
+	 * @return string Maybe-parsed widget ID.
+	 */
+	public function get_setting_id( $widget_id ) {
+		$parsed_widget_id = $this->parse_widget_id( $widget_id );
+		$setting_id       = sprintf( 'widget_%s', $parsed_widget_id['id_base'] );
+
+		if ( ! is_null( $parsed_widget_id['number'] ) ) {
+			$setting_id .= sprintf( '[%d]', $parsed_widget_id['number'] );
+		}
+		return $setting_id;
+	}
+
+	/**
+	 * Determines whether the widget is considered "wide".
+	 *
+	 * Core widgets which may have controls wider than 250, but can still be shown
+	 * in the narrow Customizer panel. The RSS and Text widgets in Core, for example,
+	 * have widths of 400 and yet they still render fine in the Customizer panel.
+	 *
+	 * This method will return all Core widgets as being not wide, but this can be
+	 * overridden with the {@see 'is_wide_widget_in_customizer'} filter.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_widget_controls
+	 *
+	 * @param string $widget_id Widget ID.
+	 * @return bool Whether or not the widget is a "wide" widget.
+	 */
+	public function is_wide_widget( $widget_id ) {
+		global $wp_registered_widget_controls;
+
+		$parsed_widget_id = $this->parse_widget_id( $widget_id );
+		$width            = $wp_registered_widget_controls[ $widget_id ]['width'];
+		$is_core          = in_array( $parsed_widget_id['id_base'], $this->core_widget_id_bases, true );
+		$is_wide          = ( $width > 250 && ! $is_core );
+
+		/**
+		 * Filters whether the given widget is considered "wide".
+		 *
+		 * @since 3.9.0
+		 *
+		 * @param bool   $is_wide   Whether the widget is wide, Default false.
+		 * @param string $widget_id Widget ID.
+		 */
+		return apply_filters( 'is_wide_widget_in_customizer', $is_wide, $widget_id );
+	}
+
+	/**
+	 * Converts a widget ID into its id_base and number components.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $widget_id Widget ID.
+	 * @return array Array containing a widget's id_base and number components.
+	 */
+	public function parse_widget_id( $widget_id ) {
+		$parsed = array(
+			'number'  => null,
+			'id_base' => null,
+		);
+
+		if ( preg_match( '/^(.+)-(\d+)$/', $widget_id, $matches ) ) {
+			$parsed['id_base'] = $matches[1];
+			$parsed['number']  = (int) $matches[2];
+		} else {
+			// Likely an old single widget.
+			$parsed['id_base'] = $widget_id;
+		}
+		return $parsed;
+	}
+
+	/**
+	 * Converts a widget setting ID (option path) to its id_base and number components.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $setting_id Widget setting ID.
+	 * @return array|WP_Error Array containing a widget's id_base and number components,
+	 *                        or a WP_Error object.
+	 */
+	public function parse_widget_setting_id( $setting_id ) {
+		if ( ! preg_match( '/^(widget_(.+?))(?:\[(\d+)\])?$/', $setting_id, $matches ) ) {
+			return new WP_Error( 'widget_setting_invalid_id' );
+		}
+
+		$id_base = $matches[2];
+		$number  = isset( $matches[3] ) ? (int) $matches[3] : null;
+
+		return compact( 'id_base', 'number' );
+	}
+
+	/**
+	 * Calls admin_print_styles-widgets.php and admin_print_styles hooks to
+	 * allow custom styles from plugins.
+	 *
+	 * @since 3.9.0
+	 */
+	public function print_styles() {
+		/** This action is documented in wp-admin/admin-header.php */
+		do_action( 'admin_print_styles-widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/admin-header.php */
+		do_action( 'admin_print_styles' );
+	}
+
+	/**
+	 * Calls admin_print_scripts-widgets.php and admin_print_scripts hooks to
+	 * allow custom scripts from plugins.
+	 *
+	 * @since 3.9.0
+	 */
+	public function print_scripts() {
+		/** This action is documented in wp-admin/admin-header.php */
+		do_action( 'admin_print_scripts-widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/admin-header.php */
+		do_action( 'admin_print_scripts' );
+	}
+
+	/**
+	 * Enqueues scripts and styles for Customizer panel and export data to JavaScript.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global WP_Scripts $wp_scripts
+	 * @global array $wp_registered_sidebars
+	 * @global array $wp_registered_widgets
+	 */
+	public function enqueue_scripts() {
+		global $wp_scripts, $wp_registered_sidebars, $wp_registered_widgets;
+
+		wp_enqueue_style( 'customize-widgets' );
+		wp_enqueue_script( 'customize-widgets' );
+
+		/** This action is documented in wp-admin/admin-header.php */
+		do_action( 'admin_enqueue_scripts', 'widgets.php' );
+
+		/*
+		 * Export available widgets with control_tpl removed from model
+		 * since plugins need templates to be in the DOM.
+		 */
+		$available_widgets = array();
+
+		foreach ( $this->get_available_widgets() as $available_widget ) {
+			unset( $available_widget['control_tpl'] );
+			$available_widgets[] = $available_widget;
+		}
+
+		$widget_reorder_nav_tpl = sprintf(
+			'<div class="widget-reorder-nav"><span class="move-widget" tabindex="0">%1$s</span><span class="move-widget-down" tabindex="0">%2$s</span><span class="move-widget-up" tabindex="0">%3$s</span></div>',
+			__( 'Move to another area&hellip;' ),
+			__( 'Move down' ),
+			__( 'Move up' )
+		);
+
+		$move_widget_area_tpl = str_replace(
+			array( '{description}', '{btn}' ),
+			array(
+				__( 'Select an area to move this widget into:' ),
+				_x( 'Move', 'Move widget' ),
+			),
+			'<div class="move-widget-area">
+				<p class="description">{description}</p>
+				<ul class="widget-area-select">
+					<% _.each( sidebars, function ( sidebar ){ %>
+						<li class="" data-id="<%- sidebar.id %>" title="<%- sidebar.description %>" tabindex="0"><%- sidebar.name %></li>
+					<% }); %>
+				</ul>
+				<div class="move-widget-actions">
+					<button class="move-widget-btn button" type="button">{btn}</button>
+				</div>
+			</div>'
+		);
+
+		/*
+		 * Gather all strings in PHP that may be needed by JS on the client.
+		 * Once JS i18n is implemented (in #20491), this can be removed.
+		 */
+		$some_non_rendered_areas_messages    = array();
+		$some_non_rendered_areas_messages[1] = html_entity_decode(
+			__( 'Your theme has 1 other widget area, but this particular page does not display it.' ),
+			ENT_QUOTES,
+			get_bloginfo( 'charset' )
+		);
+		$registered_sidebar_count            = count( $wp_registered_sidebars );
+		for ( $non_rendered_count = 2; $non_rendered_count < $registered_sidebar_count; $non_rendered_count++ ) {
+			$some_non_rendered_areas_messages[ $non_rendered_count ] = html_entity_decode(
+				sprintf(
+					/* translators: %s: The number of other widget areas registered but not rendered. */
+					_n(
+						'Your theme has %s other widget area, but this particular page does not display it.',
+						'Your theme has %s other widget areas, but this particular page does not display them.',
+						$non_rendered_count
+					),
+					number_format_i18n( $non_rendered_count )
+				),
+				ENT_QUOTES,
+				get_bloginfo( 'charset' )
+			);
+		}
+
+		if ( 1 === $registered_sidebar_count ) {
+			$no_areas_shown_message = html_entity_decode(
+				sprintf(
+					__( 'Your theme has 1 widget area, but this particular page does not display it.' )
+				),
+				ENT_QUOTES,
+				get_bloginfo( 'charset' )
+			);
+		} else {
+			$no_areas_shown_message = html_entity_decode(
+				sprintf(
+					/* translators: %s: The total number of widget areas registered. */
+					_n(
+						'Your theme has %s widget area, but this particular page does not display it.',
+						'Your theme has %s widget areas, but this particular page does not display them.',
+						$registered_sidebar_count
+					),
+					number_format_i18n( $registered_sidebar_count )
+				),
+				ENT_QUOTES,
+				get_bloginfo( 'charset' )
+			);
+		}
+
+		$settings = array(
+			'registeredSidebars'          => array_values( $wp_registered_sidebars ),
+			'registeredWidgets'           => $wp_registered_widgets,
+			'availableWidgets'            => $available_widgets, // @todo Merge this with registered_widgets.
+			'l10n'                        => array(
+				'saveBtnLabel'     => __( 'Apply' ),
+				'saveBtnTooltip'   => __( 'Save and preview changes before publishing them.' ),
+				'removeBtnLabel'   => __( 'Remove' ),
+				'removeBtnTooltip' => __( 'Keep widget settings and move it to the inactive widgets' ),
+				'error'            => __( 'An error has occurred. Please reload the page and try again.' ),
+				'widgetMovedUp'    => __( 'Widget moved up' ),
+				'widgetMovedDown'  => __( 'Widget moved down' ),
+				'navigatePreview'  => __( 'You can navigate to other pages on your site while using the Customizer to view and edit the widgets displayed on those pages.' ),
+				'someAreasShown'   => $some_non_rendered_areas_messages,
+				'noAreasShown'     => $no_areas_shown_message,
+				'reorderModeOn'    => __( 'Reorder mode enabled' ),
+				'reorderModeOff'   => __( 'Reorder mode closed' ),
+				'reorderLabelOn'   => esc_attr__( 'Reorder widgets' ),
+				/* translators: %d: The number of widgets found. */
+				'widgetsFound'     => __( 'Number of widgets found: %d' ),
+				'noWidgetsFound'   => __( 'No widgets found.' ),
+			),
+			'tpl'                         => array(
+				'widgetReorderNav' => $widget_reorder_nav_tpl,
+				'moveWidgetArea'   => $move_widget_area_tpl,
+			),
+			'selectiveRefreshableWidgets' => $this->get_selective_refreshable_widgets(),
+		);
+
+		foreach ( $settings['registeredWidgets'] as &$registered_widget ) {
+			unset( $registered_widget['callback'] ); // May not be JSON-serializeable.
+		}
+
+		$wp_scripts->add_data(
+			'customize-widgets',
+			'data',
+			sprintf( 'var _wpCustomizeWidgetsSettings = %s;', wp_json_encode( $settings ) )
+		);
+
+		/*
+		 * TODO: Update 'wp-customize-widgets' to not rely so much on things in
+		 * 'customize-widgets'. This will let us skip most of the above and not
+		 * enqueue 'customize-widgets' which saves bytes.
+		 */
+
+		if ( wp_use_widgets_block_editor() ) {
+			$block_editor_context = new WP_Block_Editor_Context(
+				array(
+					'name' => 'core/customize-widgets',
+				)
+			);
+
+			$editor_settings = get_block_editor_settings(
+				get_legacy_widget_block_editor_settings(),
+				$block_editor_context
+			);
+
+			wp_add_inline_script(
+				'wp-customize-widgets',
+				sprintf(
+					'wp.domReady( function() {
+					   wp.customizeWidgets.initialize( "widgets-customizer", %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( $block_editor_context ) ) ),
+				'after'
+			);
+
+			wp_enqueue_script( 'wp-customize-widgets' );
+			wp_enqueue_style( 'wp-customize-widgets' );
+
+			/** This action is documented in edit-form-blocks.php */
+			do_action( 'enqueue_block_editor_assets' );
+		}
+	}
+
+	/**
+	 * Renders the widget form control templates into the DOM.
+	 *
+	 * @since 3.9.0
+	 */
+	public function output_widget_control_templates() {
+		?>
+		<div id="widgets-left"><!-- compatibility with JS which looks for widget templates here -->
+		<div id="available-widgets">
+			<div class="customize-section-title">
+				<button class="customize-section-back" tabindex="-1">
+					<span class="screen-reader-text">
+						<?php
+						/* translators: Hidden accessibility text. */
+						_e( 'Back' );
+						?>
+					</span>
+				</button>
+				<h3>
+					<span class="customize-action">
+					<?php
+						/* translators: &#9656; is the unicode right-pointing triangle. %s: Section title in the Customizer. */
+						printf( __( 'Customizing &#9656; %s' ), esc_html( $this->manager->get_panel( 'widgets' )->title ) );
+					?>
+					</span>
+					<?php _e( 'Add a Widget' ); ?>
+				</h3>
+			</div>
+			<div id="available-widgets-filter">
+				<label class="screen-reader-text" for="widgets-search">
+					<?php
+					/* translators: Hidden accessibility text. */
+					_e( 'Search Widgets' );
+					?>
+				</label>
+				<input type="text" id="widgets-search" placeholder="<?php esc_attr_e( 'Search widgets&hellip;' ); ?>" aria-describedby="widgets-search-desc" />
+				<div class="search-icon" aria-hidden="true"></div>
+				<button type="button" class="clear-results"><span class="screen-reader-text">
+					<?php
+					/* translators: Hidden accessibility text. */
+					_e( 'Clear Results' );
+					?>
+				</span></button>
+				<p class="screen-reader-text" id="widgets-search-desc">
+					<?php
+					/* translators: Hidden accessibility text. */
+					_e( 'The search results will be updated as you type.' );
+					?>
+				</p>
+			</div>
+			<div id="available-widgets-list">
+			<?php foreach ( $this->get_available_widgets() as $available_widget ) : ?>
+				<div id="widget-tpl-<?php echo esc_attr( $available_widget['id'] ); ?>" data-widget-id="<?php echo esc_attr( $available_widget['id'] ); ?>" class="widget-tpl <?php echo esc_attr( $available_widget['id'] ); ?>" tabindex="0">
+					<?php echo $available_widget['control_tpl']; ?>
+				</div>
+			<?php endforeach; ?>
+			<p class="no-widgets-found-message"><?php _e( 'No widgets found.' ); ?></p>
+			</div><!-- #available-widgets-list -->
+		</div><!-- #available-widgets -->
+		</div><!-- #widgets-left -->
+		<?php
+	}
+
+	/**
+	 * Calls admin_print_footer_scripts and admin_print_scripts hooks to
+	 * allow custom scripts from plugins.
+	 *
+	 * @since 3.9.0
+	 */
+	public function print_footer_scripts() {
+		/** This action is documented in wp-admin/admin-footer.php */
+		do_action( 'admin_print_footer_scripts-widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/admin-footer.php */
+		do_action( 'admin_print_footer_scripts' );
+
+		/** This action is documented in wp-admin/admin-footer.php */
+		do_action( 'admin_footer-widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+	}
+
+	/**
+	 * Retrieves common arguments to supply when constructing a Customizer setting.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $id        Widget setting ID.
+	 * @param array  $overrides Array of setting overrides.
+	 * @return array Possibly modified setting arguments.
+	 */
+	public function get_setting_args( $id, $overrides = array() ) {
+		$args = array(
+			'type'       => 'option',
+			'capability' => 'edit_theme_options',
+			'default'    => array(),
+		);
+
+		if ( preg_match( $this->setting_id_patterns['sidebar_widgets'], $id, $matches ) ) {
+			$args['sanitize_callback']    = array( $this, 'sanitize_sidebar_widgets' );
+			$args['sanitize_js_callback'] = array( $this, 'sanitize_sidebar_widgets_js_instance' );
+			$args['transport']            = current_theme_supports( 'customize-selective-refresh-widgets' ) ? 'postMessage' : 'refresh';
+		} elseif ( preg_match( $this->setting_id_patterns['widget_instance'], $id, $matches ) ) {
+			$id_base                      = $matches['id_base'];
+			$args['sanitize_callback']    = function ( $value ) use ( $id_base ) {
+				return $this->sanitize_widget_instance( $value, $id_base );
+			};
+			$args['sanitize_js_callback'] = function ( $value ) use ( $id_base ) {
+				return $this->sanitize_widget_js_instance( $value, $id_base );
+			};
+			$args['transport']            = $this->is_widget_selective_refreshable( $matches['id_base'] ) ? 'postMessage' : 'refresh';
+		}
+
+		$args = array_merge( $args, $overrides );
+
+		/**
+		 * Filters the common arguments supplied when constructing a Customizer setting.
+		 *
+		 * @since 3.9.0
+		 *
+		 * @see WP_Customize_Setting
+		 *
+		 * @param array  $args Array of Customizer setting arguments.
+		 * @param string $id   Widget setting ID.
+		 */
+		return apply_filters( 'widget_customizer_setting_args', $args, $id );
+	}
+
+	/**
+	 * Ensures sidebar widget arrays only ever contain widget IDS.
+	 *
+	 * Used as the 'sanitize_callback' for each $sidebars_widgets setting.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string[] $widget_ids Array of widget IDs.
+	 * @return string[] Array of sanitized widget IDs.
+	 */
+	public function sanitize_sidebar_widgets( $widget_ids ) {
+		$widget_ids           = array_map( 'strval', (array) $widget_ids );
+		$sanitized_widget_ids = array();
+		foreach ( $widget_ids as $widget_id ) {
+			$sanitized_widget_ids[] = preg_replace( '/[^a-z0-9_\-]/', '', $widget_id );
+		}
+		return $sanitized_widget_ids;
+	}
+
+	/**
+	 * Builds up an index of all available widgets for use in Backbone models.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_widgets
+	 * @global array $wp_registered_widget_controls
+	 *
+	 * @see wp_list_widgets()
+	 *
+	 * @return array List of available widgets.
+	 */
+	public function get_available_widgets() {
+		static $available_widgets = array();
+		if ( ! empty( $available_widgets ) ) {
+			return $available_widgets;
+		}
+
+		global $wp_registered_widgets, $wp_registered_widget_controls;
+		require_once ABSPATH . 'wp-admin/includes/widgets.php'; // For next_widget_id_number().
+
+		$sort = $wp_registered_widgets;
+		usort( $sort, array( $this, '_sort_name_callback' ) );
+		$done = array();
+
+		foreach ( $sort as $widget ) {
+			if ( in_array( $widget['callback'], $done, true ) ) { // We already showed this multi-widget.
+				continue;
+			}
+
+			$sidebar = is_active_widget( $widget['callback'], $widget['id'], false, false );
+			$done[]  = $widget['callback'];
+
+			if ( ! isset( $widget['params'][0] ) ) {
+				$widget['params'][0] = array();
+			}
+
+			$available_widget = $widget;
+			unset( $available_widget['callback'] ); // Not serializable to JSON.
+
+			$args = array(
+				'widget_id'   => $widget['id'],
+				'widget_name' => $widget['name'],
+				'_display'    => 'template',
+			);
+
+			$is_disabled     = false;
+			$is_multi_widget = ( isset( $wp_registered_widget_controls[ $widget['id'] ]['id_base'] ) && isset( $widget['params'][0]['number'] ) );
+			if ( $is_multi_widget ) {
+				$id_base            = $wp_registered_widget_controls[ $widget['id'] ]['id_base'];
+				$args['_temp_id']   = "$id_base-__i__";
+				$args['_multi_num'] = next_widget_id_number( $id_base );
+				$args['_add']       = 'multi';
+			} else {
+				$args['_add'] = 'single';
+
+				if ( $sidebar && 'wp_inactive_widgets' !== $sidebar ) {
+					$is_disabled = true;
+				}
+				$id_base = $widget['id'];
+			}
+
+			$list_widget_controls_args = wp_list_widget_controls_dynamic_sidebar(
+				array(
+					0 => $args,
+					1 => $widget['params'][0],
+				)
+			);
+			$control_tpl               = $this->get_widget_control( $list_widget_controls_args );
+
+			// The properties here are mapped to the Backbone Widget model.
+			$available_widget = array_merge(
+				$available_widget,
+				array(
+					'temp_id'      => isset( $args['_temp_id'] ) ? $args['_temp_id'] : null,
+					'is_multi'     => $is_multi_widget,
+					'control_tpl'  => $control_tpl,
+					'multi_number' => ( 'multi' === $args['_add'] ) ? $args['_multi_num'] : false,
+					'is_disabled'  => $is_disabled,
+					'id_base'      => $id_base,
+					'transport'    => $this->is_widget_selective_refreshable( $id_base ) ? 'postMessage' : 'refresh',
+					'width'        => $wp_registered_widget_controls[ $widget['id'] ]['width'],
+					'height'       => $wp_registered_widget_controls[ $widget['id'] ]['height'],
+					'is_wide'      => $this->is_wide_widget( $widget['id'] ),
+				)
+			);
+
+			$available_widgets[] = $available_widget;
+		}
+
+		return $available_widgets;
+	}
+
+	/**
+	 * Naturally orders available widgets by name.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param array $widget_a The first widget to compare.
+	 * @param array $widget_b The second widget to compare.
+	 * @return int Reorder position for the current widget comparison.
+	 */
+	protected function _sort_name_callback( $widget_a, $widget_b ) {
+		return strnatcasecmp( $widget_a['name'], $widget_b['name'] );
+	}
+
+	/**
+	 * Retrieves the widget control markup.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param array $args Widget control arguments.
+	 * @return string Widget control form HTML markup.
+	 */
+	public function get_widget_control( $args ) {
+		$args[0]['before_form']           = '<div class="form">';
+		$args[0]['after_form']            = '</div><!-- .form -->';
+		$args[0]['before_widget_content'] = '<div class="widget-content">';
+		$args[0]['after_widget_content']  = '</div><!-- .widget-content -->';
+		ob_start();
+		wp_widget_control( ...$args );
+		$control_tpl = ob_get_clean();
+		return $control_tpl;
+	}
+
+	/**
+	 * Retrieves the widget control markup parts.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param array $args Widget control arguments.
+	 * @return array {
+	 *     @type string $control Markup for widget control wrapping form.
+	 *     @type string $content The contents of the widget form itself.
+	 * }
+	 */
+	public function get_widget_control_parts( $args ) {
+		$args[0]['before_widget_content'] = '<div class="widget-content">';
+		$args[0]['after_widget_content']  = '</div><!-- .widget-content -->';
+		$control_markup                   = $this->get_widget_control( $args );
+
+		$content_start_pos = strpos( $control_markup, $args[0]['before_widget_content'] );
+		$content_end_pos   = strrpos( $control_markup, $args[0]['after_widget_content'] );
+
+		$control  = substr( $control_markup, 0, $content_start_pos + strlen( $args[0]['before_widget_content'] ) );
+		$control .= substr( $control_markup, $content_end_pos );
+		$content  = trim(
+			substr(
+				$control_markup,
+				$content_start_pos + strlen( $args[0]['before_widget_content'] ),
+				$content_end_pos - $content_start_pos - strlen( $args[0]['before_widget_content'] )
+			)
+		);
+
+		return compact( 'control', 'content' );
+	}
+
+	/**
+	 * Adds hooks for the Customizer preview.
+	 *
+	 * @since 3.9.0
+	 */
+	public function customize_preview_init() {
+		add_action( 'wp_enqueue_scripts', array( $this, 'customize_preview_enqueue' ) );
+		add_action( 'wp_print_styles', array( $this, 'print_preview_css' ), 1 );
+		add_action( 'wp_footer', array( $this, 'export_preview_data' ), 20 );
+	}
+
+	/**
+	 * Refreshes the nonce for widget updates.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param array $nonces Array of nonces.
+	 * @return array Array of nonces.
+	 */
+	public function refresh_nonces( $nonces ) {
+		$nonces['update-widget'] = wp_create_nonce( 'update-widget' );
+		return $nonces;
+	}
+
+	/**
+	 * Tells the script loader to load the scripts and styles of custom blocks
+	 * if the widgets block editor is enabled.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param bool $is_block_editor_screen Current decision about loading block assets.
+	 * @return bool Filtered decision about loading block assets.
+	 */
+	public function should_load_block_editor_scripts_and_styles( $is_block_editor_screen ) {
+		if ( wp_use_widgets_block_editor() ) {
+			return true;
+		}
+
+		return $is_block_editor_screen;
+	}
+
+	/**
+	 * When previewing, ensures the proper previewing widgets are used.
+	 *
+	 * Because wp_get_sidebars_widgets() gets called early at {@see 'init' } (via
+	 * wp_convert_widget_settings()) and can set global variable `$_wp_sidebars_widgets`
+	 * to the value of `get_option( 'sidebars_widgets' )` before the Customizer preview
+	 * filter is added, it has to be reset after the filter has been added.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param array $sidebars_widgets List of widgets for the current sidebar.
+	 * @return array
+	 */
+	public function preview_sidebars_widgets( $sidebars_widgets ) {
+		$sidebars_widgets = get_option( 'sidebars_widgets', array() );
+
+		unset( $sidebars_widgets['array_version'] );
+		return $sidebars_widgets;
+	}
+
+	/**
+	 * Enqueues scripts for the Customizer preview.
+	 *
+	 * @since 3.9.0
+	 */
+	public function customize_preview_enqueue() {
+		wp_enqueue_script( 'customize-preview-widgets' );
+	}
+
+	/**
+	 * Inserts default style for highlighted widget at early point so theme
+	 * stylesheet can override.
+	 *
+	 * @since 3.9.0
+	 */
+	public function print_preview_css() {
+		?>
+		<style>
+		.widget-customizer-highlighted-widget {
+			outline: none;
+			-webkit-box-shadow: 0 0 2px rgba(30, 140, 190, 0.8);
+			box-shadow: 0 0 2px rgba(30, 140, 190, 0.8);
+			position: relative;
+			z-index: 1;
+		}
+		</style>
+		<?php
+	}
+
+	/**
+	 * Communicates the sidebars that appeared on the page at the very end of the page,
+	 * and at the very end of the wp_footer,
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_sidebars
+	 * @global array $wp_registered_widgets
+	 */
+	public function export_preview_data() {
+		global $wp_registered_sidebars, $wp_registered_widgets;
+
+		$switched_locale = switch_to_user_locale( get_current_user_id() );
+
+		$l10n = array(
+			'widgetTooltip' => __( 'Shift-click to edit this widget.' ),
+		);
+
+		if ( $switched_locale ) {
+			restore_previous_locale();
+		}
+
+		$rendered_sidebars = array_filter( $this->rendered_sidebars );
+		$rendered_widgets  = array_filter( $this->rendered_widgets );
+
+		// Prepare Customizer settings to pass to JavaScript.
+		$settings = array(
+			'renderedSidebars'            => array_fill_keys( array_keys( $rendered_sidebars ), true ),
+			'renderedWidgets'             => array_fill_keys( array_keys( $rendered_widgets ), true ),
+			'registeredSidebars'          => array_values( $wp_registered_sidebars ),
+			'registeredWidgets'           => $wp_registered_widgets,
+			'l10n'                        => $l10n,
+			'selectiveRefreshableWidgets' => $this->get_selective_refreshable_widgets(),
+		);
+
+		foreach ( $settings['registeredWidgets'] as &$registered_widget ) {
+			unset( $registered_widget['callback'] ); // May not be JSON-serializeable.
+		}
+		wp_print_inline_script_tag(
+			sprintf( 'var _wpWidgetCustomizerPreviewSettings = %s;', wp_json_encode( $settings ) )
+		);
+	}
+
+	/**
+	 * Tracks the widgets that were rendered.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param array $widget Rendered widget to tally.
+	 */
+	public function tally_rendered_widgets( $widget ) {
+		$this->rendered_widgets[ $widget['id'] ] = true;
+	}
+
+	/**
+	 * Determine if a widget is rendered on the page.
+	 *
+	 * @since 4.0.0
+	 *
+	 * @param string $widget_id Widget ID to check.
+	 * @return bool Whether the widget is rendered.
+	 */
+	public function is_widget_rendered( $widget_id ) {
+		return ! empty( $this->rendered_widgets[ $widget_id ] );
+	}
+
+	/**
+	 * Determines if a sidebar is rendered on the page.
+	 *
+	 * @since 4.0.0
+	 *
+	 * @param string $sidebar_id Sidebar ID to check.
+	 * @return bool Whether the sidebar is rendered.
+	 */
+	public function is_sidebar_rendered( $sidebar_id ) {
+		return ! empty( $this->rendered_sidebars[ $sidebar_id ] );
+	}
+
+	/**
+	 * Tallies the sidebars rendered via is_active_sidebar().
+	 *
+	 * Keep track of the times that is_active_sidebar() is called in the template,
+	 * and assume that this means that the sidebar would be rendered on the template
+	 * if there were widgets populating it.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param bool   $is_active  Whether the sidebar is active.
+	 * @param string $sidebar_id Sidebar ID.
+	 * @return bool Whether the sidebar is active.
+	 */
+	public function tally_sidebars_via_is_active_sidebar_calls( $is_active, $sidebar_id ) {
+		if ( is_registered_sidebar( $sidebar_id ) ) {
+			$this->rendered_sidebars[ $sidebar_id ] = true;
+		}
+
+		/*
+		 * We may need to force this to true, and also force-true the value
+		 * for 'dynamic_sidebar_has_widgets' if we want to ensure that there
+		 * is an area to drop widgets into, if the sidebar is empty.
+		 */
+		return $is_active;
+	}
+
+	/**
+	 * Tallies the sidebars rendered via dynamic_sidebar().
+	 *
+	 * Keep track of the times that dynamic_sidebar() is called in the template,
+	 * and assume this means the sidebar would be rendered on the template if
+	 * there were widgets populating it.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param bool   $has_widgets Whether the current sidebar has widgets.
+	 * @param string $sidebar_id  Sidebar ID.
+	 * @return bool Whether the current sidebar has widgets.
+	 */
+	public function tally_sidebars_via_dynamic_sidebar_calls( $has_widgets, $sidebar_id ) {
+		if ( is_registered_sidebar( $sidebar_id ) ) {
+			$this->rendered_sidebars[ $sidebar_id ] = true;
+		}
+
+		/*
+		 * We may need to force this to true, and also force-true the value
+		 * for 'is_active_sidebar' if we want to ensure there is an area to
+		 * drop widgets into, if the sidebar is empty.
+		 */
+		return $has_widgets;
+	}
+
+	/**
+	 * Retrieves MAC for a serialized widget instance string.
+	 *
+	 * Allows values posted back from JS to be rejected if any tampering of the
+	 * data has occurred.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $serialized_instance Widget instance.
+	 * @return string MAC for serialized widget instance.
+	 */
+	protected function get_instance_hash_key( $serialized_instance ) {
+		return wp_hash( $serialized_instance );
+	}
+
+	/**
+	 * Sanitizes a widget instance.
+	 *
+	 * Unserialize the JS-instance for storing in the options. It's important that this filter
+	 * only get applied to an instance *once*.
+	 *
+	 * @since 3.9.0
+	 * @since 5.8.0 Added the `$id_base` parameter.
+	 *
+	 * @global WP_Widget_Factory $wp_widget_factory
+	 *
+	 * @param array  $value   Widget instance to sanitize.
+	 * @param string $id_base Optional. Base of the ID of the widget being sanitized. Default null.
+	 * @return array|void Sanitized widget instance.
+	 */
+	public function sanitize_widget_instance( $value, $id_base = null ) {
+		global $wp_widget_factory;
+
+		if ( array() === $value ) {
+			return $value;
+		}
+
+		if ( isset( $value['raw_instance'] ) && $id_base && wp_use_widgets_block_editor() ) {
+			$widget_object = $wp_widget_factory->get_widget_object( $id_base );
+			if ( ! empty( $widget_object->widget_options['show_instance_in_rest'] ) ) {
+				if ( 'block' === $id_base && ! current_user_can( 'unfiltered_html' ) ) {
+					/*
+					 * The content of the 'block' widget is not filtered on the fly while editing.
+					 * Filter the content here to prevent vulnerabilities.
+					 */
+					$value['raw_instance']['content'] = wp_kses_post( $value['raw_instance']['content'] );
+				}
+
+				return $value['raw_instance'];
+			}
+		}
+
+		if (
+			empty( $value['is_widget_customizer_js_value'] ) ||
+			empty( $value['instance_hash_key'] ) ||
+			empty( $value['encoded_serialized_instance'] )
+		) {
+			return;
+		}
+
+		$decoded = base64_decode( $value['encoded_serialized_instance'], true );
+		if ( false === $decoded ) {
+			return;
+		}
+
+		if ( ! hash_equals( $this->get_instance_hash_key( $decoded ), $value['instance_hash_key'] ) ) {
+			return;
+		}
+
+		$instance = unserialize( $decoded );
+		if ( false === $instance ) {
+			return;
+		}
+
+		return $instance;
+	}
+
+	/**
+	 * Converts a widget instance into JSON-representable format.
+	 *
+	 * @since 3.9.0
+	 * @since 5.8.0 Added the `$id_base` parameter.
+	 *
+	 * @global WP_Widget_Factory $wp_widget_factory
+	 *
+	 * @param array  $value   Widget instance to convert to JSON.
+	 * @param string $id_base Optional. Base of the ID of the widget being sanitized. Default null.
+	 * @return array JSON-converted widget instance.
+	 */
+	public function sanitize_widget_js_instance( $value, $id_base = null ) {
+		global $wp_widget_factory;
+
+		if ( empty( $value['is_widget_customizer_js_value'] ) ) {
+			$serialized = serialize( $value );
+
+			$js_value = array(
+				'encoded_serialized_instance'   => base64_encode( $serialized ),
+				'title'                         => empty( $value['title'] ) ? '' : $value['title'],
+				'is_widget_customizer_js_value' => true,
+				'instance_hash_key'             => $this->get_instance_hash_key( $serialized ),
+			);
+
+			if ( $id_base && wp_use_widgets_block_editor() ) {
+				$widget_object = $wp_widget_factory->get_widget_object( $id_base );
+				if ( ! empty( $widget_object->widget_options['show_instance_in_rest'] ) ) {
+					$js_value['raw_instance'] = (object) $value;
+				}
+			}
+
+			return $js_value;
+		}
+
+		return $value;
+	}
+
+	/**
+	 * Strips out widget IDs for widgets which are no longer registered.
+	 *
+	 * One example where this might happen is when a plugin orphans a widget
+	 * in a sidebar upon deactivation.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_widgets
+	 *
+	 * @param array $widget_ids List of widget IDs.
+	 * @return array Parsed list of widget IDs.
+	 */
+	public function sanitize_sidebar_widgets_js_instance( $widget_ids ) {
+		global $wp_registered_widgets;
+		$widget_ids = array_values( array_intersect( $widget_ids, array_keys( $wp_registered_widgets ) ) );
+		return $widget_ids;
+	}
+
+	/**
+	 * Finds and invokes the widget update and control callbacks.
+	 *
+	 * Requires that `$_POST` be populated with the instance data.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_widget_updates
+	 * @global array $wp_registered_widget_controls
+	 *
+	 * @param string $widget_id Widget ID.
+	 * @return array|WP_Error Array containing the updated widget information.
+	 *                        A WP_Error object, otherwise.
+	 */
+	public function call_widget_update( $widget_id ) {
+		global $wp_registered_widget_updates, $wp_registered_widget_controls;
+
+		$setting_id = $this->get_setting_id( $widget_id );
+
+		/*
+		 * Make sure that other setting changes have previewed since this widget
+		 * may depend on them (e.g. Menus being present for Navigation Menu widget).
+		 */
+		if ( ! did_action( 'customize_preview_init' ) ) {
+			foreach ( $this->manager->settings() as $setting ) {
+				if ( $setting->id !== $setting_id ) {
+					$setting->preview();
+				}
+			}
+		}
+
+		$this->start_capturing_option_updates();
+		$parsed_id   = $this->parse_widget_id( $widget_id );
+		$option_name = 'widget_' . $parsed_id['id_base'];
+
+		/*
+		 * If a previously-sanitized instance is provided, populate the input vars
+		 * with its values so that the widget update callback will read this instance
+		 */
+		$added_input_vars = array();
+		if ( ! empty( $_POST['sanitized_widget_setting'] ) ) {
+			$sanitized_widget_setting = json_decode( $this->get_post_value( 'sanitized_widget_setting' ), true );
+			if ( false === $sanitized_widget_setting ) {
+				$this->stop_capturing_option_updates();
+				return new WP_Error( 'widget_setting_malformed' );
+			}
+
+			$instance = $this->sanitize_widget_instance( $sanitized_widget_setting, $parsed_id['id_base'] );
+			if ( is_null( $instance ) ) {
+				$this->stop_capturing_option_updates();
+				return new WP_Error( 'widget_setting_unsanitized' );
+			}
+
+			if ( ! is_null( $parsed_id['number'] ) ) {
+				$value                         = array();
+				$value[ $parsed_id['number'] ] = $instance;
+				$key                           = 'widget-' . $parsed_id['id_base'];
+				$_REQUEST[ $key ]              = wp_slash( $value );
+				$_POST[ $key ]                 = $_REQUEST[ $key ];
+				$added_input_vars[]            = $key;
+			} else {
+				foreach ( $instance as $key => $value ) {
+					$_REQUEST[ $key ]   = wp_slash( $value );
+					$_POST[ $key ]      = $_REQUEST[ $key ];
+					$added_input_vars[] = $key;
+				}
+			}
+		}
+
+		// Invoke the widget update callback.
+		foreach ( (array) $wp_registered_widget_updates as $name => $control ) {
+			if ( $name === $parsed_id['id_base'] && is_callable( $control['callback'] ) ) {
+				ob_start();
+				call_user_func_array( $control['callback'], $control['params'] );
+				ob_end_clean();
+				break;
+			}
+		}
+
+		// Clean up any input vars that were manually added.
+		foreach ( $added_input_vars as $key ) {
+			unset( $_POST[ $key ] );
+			unset( $_REQUEST[ $key ] );
+		}
+
+		// Make sure the expected option was updated.
+		if ( 0 !== $this->count_captured_options() ) {
+			if ( $this->count_captured_options() > 1 ) {
+				$this->stop_capturing_option_updates();
+				return new WP_Error( 'widget_setting_too_many_options' );
+			}
+
+			$updated_option_name = key( $this->get_captured_options() );
+			if ( $updated_option_name !== $option_name ) {
+				$this->stop_capturing_option_updates();
+				return new WP_Error( 'widget_setting_unexpected_option' );
+			}
+		}
+
+		// Obtain the widget instance.
+		$option = $this->get_captured_option( $option_name );
+		if ( null !== $parsed_id['number'] ) {
+			$instance = $option[ $parsed_id['number'] ];
+		} else {
+			$instance = $option;
+		}
+
+		/*
+		 * Override the incoming $_POST['customized'] for a newly-created widget's
+		 * setting with the new $instance so that the preview filter currently
+		 * in place from WP_Customize_Setting::preview() will use this value
+		 * instead of the default widget instance value (an empty array).
+		 */
+		$this->manager->set_post_value( $setting_id, $this->sanitize_widget_js_instance( $instance, $parsed_id['id_base'] ) );
+
+		// Obtain the widget control with the updated instance in place.
+		ob_start();
+		$form = $wp_registered_widget_controls[ $widget_id ];
+		if ( $form ) {
+			call_user_func_array( $form['callback'], $form['params'] );
+		}
+		$form = ob_get_clean();
+
+		$this->stop_capturing_option_updates();
+
+		return compact( 'instance', 'form' );
+	}
+
+	/**
+	 * Updates widget settings asynchronously.
+	 *
+	 * Allows the Customizer to update a widget using its form, but return the new
+	 * instance info via Ajax instead of saving it to the options table.
+	 *
+	 * Most code here copied from wp_ajax_save_widget().
+	 *
+	 * @since 3.9.0
+	 *
+	 * @see wp_ajax_save_widget()
+	 */
+	public function wp_ajax_update_widget() {
+
+		if ( ! is_user_logged_in() ) {
+			wp_die( 0 );
+		}
+
+		check_ajax_referer( 'update-widget', 'nonce' );
+
+		if ( ! current_user_can( 'edit_theme_options' ) ) {
+			wp_die( -1 );
+		}
+
+		if ( empty( $_POST['widget-id'] ) ) {
+			wp_send_json_error( 'missing_widget-id' );
+		}
+
+		/** This action is documented in wp-admin/includes/ajax-actions.php */
+		do_action( 'load-widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/includes/ajax-actions.php */
+		do_action( 'widgets.php' ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+
+		/** This action is documented in wp-admin/widgets.php */
+		do_action( 'sidebar_admin_setup' );
+
+		$widget_id = $this->get_post_value( 'widget-id' );
+		$parsed_id = $this->parse_widget_id( $widget_id );
+		$id_base   = $parsed_id['id_base'];
+
+		$is_updating_widget_template = (
+			isset( $_POST[ 'widget-' . $id_base ] )
+			&&
+			is_array( $_POST[ 'widget-' . $id_base ] )
+			&&
+			preg_match( '/__i__|%i%/', key( $_POST[ 'widget-' . $id_base ] ) )
+		);
+		if ( $is_updating_widget_template ) {
+			wp_send_json_error( 'template_widget_not_updatable' );
+		}
+
+		$updated_widget = $this->call_widget_update( $widget_id ); // => {instance,form}
+		if ( is_wp_error( $updated_widget ) ) {
+			wp_send_json_error( $updated_widget->get_error_code() );
+		}
+
+		$form     = $updated_widget['form'];
+		$instance = $this->sanitize_widget_js_instance( $updated_widget['instance'], $id_base );
+
+		wp_send_json_success( compact( 'form', 'instance' ) );
+	}
+
+	/*
+	 * Selective Refresh Methods
+	 */
+
+	/**
+	 * Filters arguments for dynamic widget partials.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param array|false $partial_args Partial arguments.
+	 * @param string      $partial_id   Partial ID.
+	 * @return array (Maybe) modified partial arguments.
+	 */
+	public function customize_dynamic_partial_args( $partial_args, $partial_id ) {
+		if ( ! current_theme_supports( 'customize-selective-refresh-widgets' ) ) {
+			return $partial_args;
+		}
+
+		if ( preg_match( '/^widget\[(?P<widget_id>.+)\]$/', $partial_id, $matches ) ) {
+			if ( false === $partial_args ) {
+				$partial_args = array();
+			}
+			$partial_args = array_merge(
+				$partial_args,
+				array(
+					'type'                => 'widget',
+					'render_callback'     => array( $this, 'render_widget_partial' ),
+					'container_inclusive' => true,
+					'settings'            => array( $this->get_setting_id( $matches['widget_id'] ) ),
+					'capability'          => 'edit_theme_options',
+				)
+			);
+		}
+
+		return $partial_args;
+	}
+
+	/**
+	 * Adds hooks for selective refresh.
+	 *
+	 * @since 4.5.0
+	 */
+	public function selective_refresh_init() {
+		if ( ! current_theme_supports( 'customize-selective-refresh-widgets' ) ) {
+			return;
+		}
+		add_filter( 'dynamic_sidebar_params', array( $this, 'filter_dynamic_sidebar_params' ) );
+		add_filter( 'wp_kses_allowed_html', array( $this, 'filter_wp_kses_allowed_data_attributes' ) );
+		add_action( 'dynamic_sidebar_before', array( $this, 'start_dynamic_sidebar' ) );
+		add_action( 'dynamic_sidebar_after', array( $this, 'end_dynamic_sidebar' ) );
+	}
+
+	/**
+	 * Inject selective refresh data attributes into widget container elements.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param array $params {
+	 *     Dynamic sidebar params.
+	 *
+	 *     @type array $args        Sidebar args.
+	 *     @type array $widget_args Widget args.
+	 * }
+	 * @see WP_Customize_Nav_Menus::filter_wp_nav_menu_args()
+	 *
+	 * @return array Params.
+	 */
+	public function filter_dynamic_sidebar_params( $params ) {
+		$sidebar_args = array_merge(
+			array(
+				'before_widget' => '',
+				'after_widget'  => '',
+			),
+			$params[0]
+		);
+
+		// Skip widgets not in a registered sidebar or ones which lack a proper wrapper element to attach the data-* attributes to.
+		$matches  = array();
+		$is_valid = (
+			isset( $sidebar_args['id'] )
+			&&
+			is_registered_sidebar( $sidebar_args['id'] )
+			&&
+			( isset( $this->current_dynamic_sidebar_id_stack[0] ) && $this->current_dynamic_sidebar_id_stack[0] === $sidebar_args['id'] )
+			&&
+			preg_match( '#^<(?P<tag_name>\w+)#', $sidebar_args['before_widget'], $matches )
+		);
+		if ( ! $is_valid ) {
+			return $params;
+		}
+		$this->before_widget_tags_seen[ $matches['tag_name'] ] = true;
+
+		$context = array(
+			'sidebar_id' => $sidebar_args['id'],
+		);
+		if ( isset( $this->context_sidebar_instance_number ) ) {
+			$context['sidebar_instance_number'] = $this->context_sidebar_instance_number;
+		} elseif ( isset( $sidebar_args['id'] ) && isset( $this->sidebar_instance_count[ $sidebar_args['id'] ] ) ) {
+			$context['sidebar_instance_number'] = $this->sidebar_instance_count[ $sidebar_args['id'] ];
+		}
+
+		$attributes                    = sprintf( ' data-customize-partial-id="%s"', esc_attr( 'widget[' . $sidebar_args['widget_id'] . ']' ) );
+		$attributes                   .= ' data-customize-partial-type="widget"';
+		$attributes                   .= sprintf( ' data-customize-partial-placement-context="%s"', esc_attr( wp_json_encode( $context ) ) );
+		$attributes                   .= sprintf( ' data-customize-widget-id="%s"', esc_attr( $sidebar_args['widget_id'] ) );
+		$sidebar_args['before_widget'] = preg_replace( '#^(<\w+)#', '$1 ' . $attributes, $sidebar_args['before_widget'] );
+
+		$params[0] = $sidebar_args;
+		return $params;
+	}
+
+	/**
+	 * List of the tag names seen for before_widget strings.
+	 *
+	 * This is used in the {@see 'filter_wp_kses_allowed_html'} filter to ensure that the
+	 * data-* attributes can be allowed.
+	 *
+	 * @since 4.5.0
+	 * @var array
+	 */
+	protected $before_widget_tags_seen = array();
+
+	/**
+	 * Ensures the HTML data-* attributes for selective refresh are allowed by kses.
+	 *
+	 * This is needed in case the `$before_widget` is run through wp_kses() when printed.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param array $allowed_html Allowed HTML.
+	 * @return array (Maybe) modified allowed HTML.
+	 */
+	public function filter_wp_kses_allowed_data_attributes( $allowed_html ) {
+		foreach ( array_keys( $this->before_widget_tags_seen ) as $tag_name ) {
+			if ( ! isset( $allowed_html[ $tag_name ] ) ) {
+				$allowed_html[ $tag_name ] = array();
+			}
+			$allowed_html[ $tag_name ] = array_merge(
+				$allowed_html[ $tag_name ],
+				array_fill_keys(
+					array(
+						'data-customize-partial-id',
+						'data-customize-partial-type',
+						'data-customize-partial-placement-context',
+						'data-customize-partial-widget-id',
+						'data-customize-partial-options',
+					),
+					true
+				)
+			);
+		}
+		return $allowed_html;
+	}
+
+	/**
+	 * Keep track of the number of times that dynamic_sidebar() was called for a given sidebar index.
+	 *
+	 * This helps facilitate the uncommon scenario where a single sidebar is rendered multiple times on a template.
+	 *
+	 * @since 4.5.0
+	 * @var array
+	 */
+	protected $sidebar_instance_count = array();
+
+	/**
+	 * The current request's sidebar_instance_number context.
+	 *
+	 * @since 4.5.0
+	 * @var int|null
+	 */
+	protected $context_sidebar_instance_number;
+
+	/**
+	 * Current sidebar ID being rendered.
+	 *
+	 * @since 4.5.0
+	 * @var array
+	 */
+	protected $current_dynamic_sidebar_id_stack = array();
+
+	/**
+	 * Begins keeping track of the current sidebar being rendered.
+	 *
+	 * Insert marker before widgets are rendered in a dynamic sidebar.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param int|string $index Index, name, or ID of the dynamic sidebar.
+	 */
+	public function start_dynamic_sidebar( $index ) {
+		array_unshift( $this->current_dynamic_sidebar_id_stack, $index );
+		if ( ! isset( $this->sidebar_instance_count[ $index ] ) ) {
+			$this->sidebar_instance_count[ $index ] = 0;
+		}
+		$this->sidebar_instance_count[ $index ] += 1;
+		if ( ! $this->manager->selective_refresh->is_render_partials_request() ) {
+			printf( "\n<!--dynamic_sidebar_before:%s:%d-->\n", esc_html( $index ), (int) $this->sidebar_instance_count[ $index ] );
+		}
+	}
+
+	/**
+	 * Finishes keeping track of the current sidebar being rendered.
+	 *
+	 * Inserts a marker after widgets are rendered in a dynamic sidebar.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param int|string $index Index, name, or ID of the dynamic sidebar.
+	 */
+	public function end_dynamic_sidebar( $index ) {
+		array_shift( $this->current_dynamic_sidebar_id_stack );
+		if ( ! $this->manager->selective_refresh->is_render_partials_request() ) {
+			printf( "\n<!--dynamic_sidebar_after:%s:%d-->\n", esc_html( $index ), (int) $this->sidebar_instance_count[ $index ] );
+		}
+	}
+
+	/**
+	 * Current sidebar being rendered.
+	 *
+	 * @since 4.5.0
+	 * @var string|null
+	 */
+	protected $rendering_widget_id;
+
+	/**
+	 * Current widget being rendered.
+	 *
+	 * @since 4.5.0
+	 * @var string|null
+	 */
+	protected $rendering_sidebar_id;
+
+	/**
+	 * Filters sidebars_widgets to ensure the currently-rendered widget is the only widget in the current sidebar.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param array $sidebars_widgets Sidebars widgets.
+	 * @return array Filtered sidebars widgets.
+	 */
+	public function filter_sidebars_widgets_for_rendering_widget( $sidebars_widgets ) {
+		$sidebars_widgets[ $this->rendering_sidebar_id ] = array( $this->rendering_widget_id );
+		return $sidebars_widgets;
+	}
+
+	/**
+	 * Renders a specific widget using the supplied sidebar arguments.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @see dynamic_sidebar()
+	 *
+	 * @param WP_Customize_Partial $partial Partial.
+	 * @param array                $context {
+	 *     Sidebar args supplied as container context.
+	 *
+	 *     @type string $sidebar_id              ID for sidebar for widget to render into.
+	 *     @type int    $sidebar_instance_number Disambiguating instance number.
+	 * }
+	 * @return string|false
+	 */
+	public function render_widget_partial( $partial, $context ) {
+		$id_data   = $partial->id_data();
+		$widget_id = array_shift( $id_data['keys'] );
+
+		if ( ! is_array( $context )
+			|| empty( $context['sidebar_id'] )
+			|| ! is_registered_sidebar( $context['sidebar_id'] )
+		) {
+			return false;
+		}
+
+		$this->rendering_sidebar_id = $context['sidebar_id'];
+
+		if ( isset( $context['sidebar_instance_number'] ) ) {
+			$this->context_sidebar_instance_number = (int) $context['sidebar_instance_number'];
+		}
+
+		// Filter sidebars_widgets so that only the queried widget is in the sidebar.
+		$this->rendering_widget_id = $widget_id;
+
+		$filter_callback = array( $this, 'filter_sidebars_widgets_for_rendering_widget' );
+		add_filter( 'sidebars_widgets', $filter_callback, 1000 );
+
+		// Render the widget.
+		ob_start();
+		$this->rendering_sidebar_id = $context['sidebar_id'];
+		dynamic_sidebar( $this->rendering_sidebar_id );
+		$container = ob_get_clean();
+
+		// Reset variables for next partial render.
+		remove_filter( 'sidebars_widgets', $filter_callback, 1000 );
+
+		$this->context_sidebar_instance_number = null;
+		$this->rendering_sidebar_id            = null;
+		$this->rendering_widget_id             = null;
+
+		return $container;
+	}
+
+	//
+	// Option Update Capturing.
+	//
+
+	/**
+	 * List of captured widget option updates.
+	 *
+	 * @since 3.9.0
+	 * @var array $_captured_options Values updated while option capture is happening.
+	 */
+	protected $_captured_options = array();
+
+	/**
+	 * Whether option capture is currently happening.
+	 *
+	 * @since 3.9.0
+	 * @var bool $_is_current Whether option capture is currently happening or not.
+	 */
+	protected $_is_capturing_option_updates = false;
+
+	/**
+	 * Determines whether the captured option update should be ignored.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param string $option_name Option name.
+	 * @return bool Whether the option capture is ignored.
+	 */
+	protected function is_option_capture_ignored( $option_name ) {
+		return ( str_starts_with( $option_name, '_transient_' ) );
+	}
+
+	/**
+	 * Retrieves captured widget option updates.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @return array Array of captured options.
+	 */
+	protected function get_captured_options() {
+		return $this->_captured_options;
+	}
+
+	/**
+	 * Retrieves the option that was captured from being saved.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param string $option_name   Option name.
+	 * @param mixed  $default_value Optional. Default value to return if the option does not exist. Default false.
+	 * @return mixed Value set for the option.
+	 */
+	protected function get_captured_option( $option_name, $default_value = false ) {
+		if ( array_key_exists( $option_name, $this->_captured_options ) ) {
+			$value = $this->_captured_options[ $option_name ];
+		} else {
+			$value = $default_value;
+		}
+		return $value;
+	}
+
+	/**
+	 * Retrieves the number of captured widget option updates.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @return int Number of updated options.
+	 */
+	protected function count_captured_options() {
+		return count( $this->_captured_options );
+	}
+
+	/**
+	 * Begins keeping track of changes to widget options, caching new values.
+	 *
+	 * @since 3.9.0
+	 */
+	protected function start_capturing_option_updates() {
+		if ( $this->_is_capturing_option_updates ) {
+			return;
+		}
+
+		$this->_is_capturing_option_updates = true;
+
+		add_filter( 'pre_update_option', array( $this, 'capture_filter_pre_update_option' ), 10, 3 );
+	}
+
+	/**
+	 * Pre-filters captured option values before updating.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param mixed  $new_value   The new option value.
+	 * @param string $option_name Name of the option.
+	 * @param mixed  $old_value   The old option value.
+	 * @return mixed Filtered option value.
+	 */
+	public function capture_filter_pre_update_option( $new_value, $option_name, $old_value ) {
+		if ( $this->is_option_capture_ignored( $option_name ) ) {
+			return $new_value;
+		}
+
+		if ( ! isset( $this->_captured_options[ $option_name ] ) ) {
+			add_filter( "pre_option_{$option_name}", array( $this, 'capture_filter_pre_get_option' ) );
+		}
+
+		$this->_captured_options[ $option_name ] = $new_value;
+
+		return $old_value;
+	}
+
+	/**
+	 * Pre-filters captured option values before retrieving.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param mixed $value Value to return instead of the option value.
+	 * @return mixed Filtered option value.
+	 */
+	public function capture_filter_pre_get_option( $value ) {
+		$option_name = preg_replace( '/^pre_option_/', '', current_filter() );
+
+		if ( isset( $this->_captured_options[ $option_name ] ) ) {
+			$value = $this->_captured_options[ $option_name ];
+
+			/** This filter is documented in wp-includes/option.php */
+			$value = apply_filters( 'option_' . $option_name, $value, $option_name );
+		}
+
+		return $value;
+	}
+
+	/**
+	 * Undoes any changes to the options since options capture began.
+	 *
+	 * @since 3.9.0
+	 */
+	protected function stop_capturing_option_updates() {
+		if ( ! $this->_is_capturing_option_updates ) {
+			return;
+		}
+
+		remove_filter( 'pre_update_option', array( $this, 'capture_filter_pre_update_option' ), 10 );
+
+		foreach ( array_keys( $this->_captured_options ) as $option_name ) {
+			remove_filter( "pre_option_{$option_name}", array( $this, 'capture_filter_pre_get_option' ) );
+		}
+
+		$this->_captured_options            = array();
+		$this->_is_capturing_option_updates = false;
+	}
+
+	/**
+	 * {@internal Missing Summary}
+	 *
+	 * See the {@see 'customize_dynamic_setting_args'} filter.
+	 *
+	 * @since 3.9.0
+	 * @deprecated 4.2.0 Deprecated in favor of the {@see 'customize_dynamic_setting_args'} filter.
+	 */
+	public function setup_widget_addition_previews() {
+		_deprecated_function( __METHOD__, '4.2.0', 'customize_dynamic_setting_args' );
+	}
+
+	/**
+	 * {@internal Missing Summary}
+	 *
+	 * See the {@see 'customize_dynamic_setting_args'} filter.
+	 *
+	 * @since 3.9.0
+	 * @deprecated 4.2.0 Deprecated in favor of the {@see 'customize_dynamic_setting_args'} filter.
+	 */
+	public function prepreview_added_sidebars_widgets() {
+		_deprecated_function( __METHOD__, '4.2.0', 'customize_dynamic_setting_args' );
+	}
+
+	/**
+	 * {@internal Missing Summary}
+	 *
+	 * See the {@see 'customize_dynamic_setting_args'} filter.
+	 *
+	 * @since 3.9.0
+	 * @deprecated 4.2.0 Deprecated in favor of the {@see 'customize_dynamic_setting_args'} filter.
+	 */
+	public function prepreview_added_widget_instance() {
+		_deprecated_function( __METHOD__, '4.2.0', 'customize_dynamic_setting_args' );
+	}
+
+	/**
+	 * {@internal Missing Summary}
+	 *
+	 * See the {@see 'customize_dynamic_setting_args'} filter.
+	 *
+	 * @since 3.9.0
+	 * @deprecated 4.2.0 Deprecated in favor of the {@see 'customize_dynamic_setting_args'} filter.
+	 */
+	public function remove_prepreview_filters() {
+		_deprecated_function( __METHOD__, '4.2.0', 'customize_dynamic_setting_args' );
+	}
+}