Wordpress 4.6
[autoinstalls/wordpress.git] / wp-includes / class-wp-customize-manager.php
index 4465a80545c5bfcef01059d320dd6300b2b43921..09e48b290cc11ed7a33d51002abcf7054a78b0e0 100644 (file)
@@ -1,6 +1,14 @@
 <?php
 /**
- * Customize Manager.
+ * WordPress Customize Manager classes
+ *
+ * @package WordPress
+ * @subpackage Customize
+ * @since 3.4.0
+ */
+
+/**
+ * Customize Manager class.
  *
  * Bootstraps the Customize experience on the server-side.
  *
  * Serves as a factory for Customize Controls and Settings, and
  * instantiates default Customize Controls and Settings.
  *
- * @package WordPress
- * @subpackage Customize
  * @since 3.4.0
  */
 final class WP_Customize_Manager {
        /**
         * An instance of the theme being previewed.
         *
+        * @since 3.4.0
+        * @access protected
         * @var WP_Theme
         */
        protected $theme;
@@ -25,6 +33,8 @@ final class WP_Customize_Manager {
        /**
         * The directory name of the previously active theme (within the theme_root).
         *
+        * @since 3.4.0
+        * @access protected
         * @var string
         */
        protected $original_stylesheet;
@@ -32,29 +42,158 @@ final class WP_Customize_Manager {
        /**
         * Whether this is a Customizer pageload.
         *
-        * @var boolean
+        * @since 3.4.0
+        * @access protected
+        * @var bool
         */
        protected $previewing = false;
 
        /**
-        * Methods and properties deailing with managing widgets in the customizer.
+        * Methods and properties dealing with managing widgets in the Customizer.
         *
+        * @since 3.9.0
+        * @access public
         * @var WP_Customize_Widgets
         */
        public $widgets;
 
-       protected $settings   = array();
+       /**
+        * Methods and properties dealing with managing nav menus in the Customizer.
+        *
+        * @since 4.3.0
+        * @access public
+        * @var WP_Customize_Nav_Menus
+        */
+       public $nav_menus;
+
+       /**
+        * Methods and properties dealing with selective refresh in the Customizer preview.
+        *
+        * @since 4.5.0
+        * @access public
+        * @var WP_Customize_Selective_Refresh
+        */
+       public $selective_refresh;
+
+       /**
+        * Registered instances of WP_Customize_Setting.
+        *
+        * @since 3.4.0
+        * @access protected
+        * @var array
+        */
+       protected $settings = array();
+
+       /**
+        * Sorted top-level instances of WP_Customize_Panel and WP_Customize_Section.
+        *
+        * @since 4.0.0
+        * @access protected
+        * @var array
+        */
        protected $containers = array();
-       protected $panels     = array();
-       protected $sections   = array();
-       protected $controls   = array();
 
+       /**
+        * Registered instances of WP_Customize_Panel.
+        *
+        * @since 4.0.0
+        * @access protected
+        * @var array
+        */
+       protected $panels = array();
+
+       /**
+        * List of core components.
+        *
+        * @since 4.5.0
+        * @access protected
+        * @var array
+        */
+       protected $components = array( 'widgets', 'nav_menus' );
+
+       /**
+        * Registered instances of WP_Customize_Section.
+        *
+        * @since 3.4.0
+        * @access protected
+        * @var array
+        */
+       protected $sections = array();
+
+       /**
+        * Registered instances of WP_Customize_Control.
+        *
+        * @since 3.4.0
+        * @access protected
+        * @var array
+        */
+       protected $controls = array();
+
+       /**
+        * Return value of check_ajax_referer() in customize_preview_init() method.
+        *
+        * @since 3.5.0
+        * @access protected
+        * @var false|int
+        */
        protected $nonce_tick;
 
-       protected $customized;
+       /**
+        * Panel types that may be rendered from JS templates.
+        *
+        * @since 4.3.0
+        * @access protected
+        * @var array
+        */
+       protected $registered_panel_types = array();
+
+       /**
+        * Section types that may be rendered from JS templates.
+        *
+        * @since 4.3.0
+        * @access protected
+        * @var array
+        */
+       protected $registered_section_types = array();
+
+       /**
+        * Control types that may be rendered from JS templates.
+        *
+        * @since 4.1.0
+        * @access protected
+        * @var array
+        */
+       protected $registered_control_types = array();
+
+       /**
+        * Initial URL being previewed.
+        *
+        * @since 4.4.0
+        * @access protected
+        * @var string
+        */
+       protected $preview_url;
+
+       /**
+        * URL to link the user to when closing the Customizer.
+        *
+        * @since 4.4.0
+        * @access protected
+        * @var string
+        */
+       protected $return_url;
+
+       /**
+        * Mapping of 'panel', 'section', 'control' to the ID which should be autofocused.
+        *
+        * @since 4.4.0
+        * @access protected
+        * @var array
+        */
+       protected $autofocus = array();
 
        /**
-        * $_POST values for Customize Settings.
+        * Unsanitized values for Customize Settings parsed from $_POST['customized'].
         *
         * @var array
         */
@@ -66,23 +205,81 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         */
        public function __construct() {
-               require( ABSPATH . WPINC . '/class-wp-customize-setting.php' );
-               require( ABSPATH . WPINC . '/class-wp-customize-panel.php' );
-               require( ABSPATH . WPINC . '/class-wp-customize-section.php' );
-               require( ABSPATH . WPINC . '/class-wp-customize-control.php' );
-               require( ABSPATH . WPINC . '/class-wp-customize-widgets.php' );
+               require_once( ABSPATH . WPINC . '/class-wp-customize-setting.php' );
+               require_once( ABSPATH . WPINC . '/class-wp-customize-panel.php' );
+               require_once( ABSPATH . WPINC . '/class-wp-customize-section.php' );
+               require_once( ABSPATH . WPINC . '/class-wp-customize-control.php' );
+
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-color-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-media-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-upload-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-image-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-background-image-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-cropped-image-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-site-icon-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-header-image-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-theme-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-widget-area-customize-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-widget-form-customize-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-item-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-location-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-name-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-auto-add-control.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-new-menu-control.php' );
+
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menus-panel.php' );
+
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-themes-section.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-sidebar-section.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-section.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-new-menu-section.php' );
+
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-filter-setting.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-header-image-setting.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-background-image-setting.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-item-setting.php' );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-setting.php' );
+
+               /**
+                * Filters the core Customizer components to load.
+                *
+                * This allows Core components to be excluded from being instantiated by
+                * filtering them out of the array. Note that this filter generally runs
+                * during the {@see 'plugins_loaded'} action, so it cannot be added
+                * in a theme.
+                *
+                * @since 4.4.0
+                *
+                * @see WP_Customize_Manager::__construct()
+                *
+                * @param array                $components List of core components to load.
+                * @param WP_Customize_Manager $this       WP_Customize_Manager instance.
+                */
+               $components = apply_filters( 'customize_loaded_components', $this->components, $this );
 
-               $this->widgets = new WP_Customize_Widgets( $this );
+               require_once( ABSPATH . WPINC . '/customize/class-wp-customize-selective-refresh.php' );
+               $this->selective_refresh = new WP_Customize_Selective_Refresh( $this );
+
+               if ( in_array( 'widgets', $components, true ) ) {
+                       require_once( ABSPATH . WPINC . '/class-wp-customize-widgets.php' );
+                       $this->widgets = new WP_Customize_Widgets( $this );
+               }
+
+               if ( in_array( 'nav_menus', $components, true ) ) {
+                       require_once( ABSPATH . WPINC . '/class-wp-customize-nav-menus.php' );
+                       $this->nav_menus = new WP_Customize_Nav_Menus( $this );
+               }
 
                add_filter( 'wp_die_handler', array( $this, 'wp_die_handler' ) );
 
-               add_action( 'setup_theme',  array( $this, 'setup_theme' ) );
-               add_action( 'wp_loaded',    array( $this, 'wp_loaded' ) );
+               add_action( 'setup_theme', array( $this, 'setup_theme' ) );
+               add_action( 'wp_loaded',   array( $this, 'wp_loaded' ) );
 
                // Run wp_redirect_status late to make sure we override the status last.
                add_action( 'wp_redirect_status', array( $this, 'wp_redirect_status' ), 1000 );
 
-               // Do not spawn cron (especially the alternate cron) while running the customizer.
+               // Do not spawn cron (especially the alternate cron) while running the Customizer.
                remove_action( 'init', 'wp_cron' );
 
                // Do not run update checks when rendering the controls.
@@ -90,53 +287,82 @@ final class WP_Customize_Manager {
                remove_action( 'admin_init', '_maybe_update_plugins' );
                remove_action( 'admin_init', '_maybe_update_themes' );
 
-               add_action( 'wp_ajax_customize_save', array( $this, 'save' ) );
+               add_action( 'wp_ajax_customize_save',           array( $this, 'save' ) );
+               add_action( 'wp_ajax_customize_refresh_nonces', array( $this, 'refresh_nonces' ) );
 
                add_action( 'customize_register',                 array( $this, 'register_controls' ) );
+               add_action( 'customize_register',                 array( $this, 'register_dynamic_settings' ), 11 ); // allow code to create settings first
                add_action( 'customize_controls_init',            array( $this, 'prepare_controls' ) );
                add_action( 'customize_controls_enqueue_scripts', array( $this, 'enqueue_control_scripts' ) );
+
+               // Render Panel, Section, and Control templates.
+               add_action( 'customize_controls_print_footer_scripts', array( $this, 'render_panel_templates' ), 1 );
+               add_action( 'customize_controls_print_footer_scripts', array( $this, 'render_section_templates' ), 1 );
+               add_action( 'customize_controls_print_footer_scripts', array( $this, 'render_control_templates' ), 1 );
+
+               // Export the settings to JS via the _wpCustomizeSettings variable.
+               add_action( 'customize_controls_print_footer_scripts', array( $this, 'customize_pane_settings' ), 1000 );
        }
 
        /**
-        * Return true if it's an AJAX request.
+        * Return true if it's an Ajax request.
         *
         * @since 3.4.0
+        * @since 4.2.0 Added `$action` param.
+        * @access public
         *
-        * @return bool
+        * @param string|null $action Whether the supplied Ajax action is being run.
+        * @return bool True if it's an Ajax request, false otherwise.
         */
-       public function doing_ajax() {
-               return isset( $_POST['customized'] ) || ( defined( 'DOING_AJAX' ) && DOING_AJAX );
+       public function doing_ajax( $action = null ) {
+               $doing_ajax = ( defined( 'DOING_AJAX' ) && DOING_AJAX );
+               if ( ! $doing_ajax ) {
+                       return false;
+               }
+
+               if ( ! $action ) {
+                       return true;
+               } else {
+                       /*
+                        * Note: we can't just use doing_action( "wp_ajax_{$action}" ) because we need
+                        * to check before admin-ajax.php gets to that point.
+                        */
+                       return isset( $_REQUEST['action'] ) && wp_unslash( $_REQUEST['action'] ) === $action;
+               }
        }
 
        /**
         * Custom wp_die wrapper. Returns either the standard message for UI
-        * or the AJAX message.
+        * or the Ajax message.
         *
         * @since 3.4.0
         *
-        * @param mixed $ajax_message AJAX return
+        * @param mixed $ajax_message Ajax return
         * @param mixed $message UI message
         */
        protected function wp_die( $ajax_message, $message = null ) {
-               if ( $this->doing_ajax() )
+               if ( $this->doing_ajax() || isset( $_POST['customized'] ) ) {
                        wp_die( $ajax_message );
+               }
 
-               if ( ! $message )
+               if ( ! $message ) {
                        $message = __( 'Cheatin&#8217; uh?' );
+               }
 
                wp_die( $message );
        }
 
        /**
-        * Return the AJAX wp_die() handler if it's a customized request.
+        * Return the Ajax wp_die() handler if it's a customized request.
         *
         * @since 3.4.0
         *
         * @return string
         */
        public function wp_die_handler() {
-               if ( $this->doing_ajax() )
+               if ( $this->doing_ajax() || isset( $_POST['customized'] ) ) {
                        return '_ajax_wp_die_handler';
+               }
 
                return '_default_wp_die_handler';
        }
@@ -151,15 +377,17 @@ final class WP_Customize_Manager {
        public function setup_theme() {
                send_origin_headers();
 
-               if ( is_admin() && ! $this->doing_ajax() )
-                   auth_redirect();
-               elseif ( $this->doing_ajax() && ! is_user_logged_in() )
-                   $this->wp_die( 0 );
+               $doing_ajax_or_is_customized = ( $this->doing_ajax() || isset( $_POST['customized'] ) );
+               if ( is_admin() && ! $doing_ajax_or_is_customized ) {
+                       auth_redirect();
+               } elseif ( $doing_ajax_or_is_customized && ! is_user_logged_in() ) {
+                       $this->wp_die( 0, __( 'You must be logged in to complete this action.' ) );
+               }
 
                show_admin_bar( false );
 
                if ( ! current_user_can( 'customize' ) ) {
-                       $this->wp_die( -1 );
+                       $this->wp_die( -1, __( 'Sorry, you are not allowed to customize this site.' ) );
                }
 
                $this->original_stylesheet = get_stylesheet();
@@ -172,16 +400,19 @@ final class WP_Customize_Manager {
                } else {
                        // If the requested theme is not the active theme and the user doesn't have the
                        // switch_themes cap, bail.
-                       if ( ! current_user_can( 'switch_themes' ) )
-                               $this->wp_die( -1 );
+                       if ( ! current_user_can( 'switch_themes' ) ) {
+                               $this->wp_die( -1, __( 'Sorry, you are not allowed to edit theme options on this site.' ) );
+                       }
 
                        // If the theme has errors while loading, bail.
-                       if ( $this->theme()->errors() )
-                               $this->wp_die( -1 );
+                       if ( $this->theme()->errors() ) {
+                               $this->wp_die( -1, $this->theme()->errors()->get_error_message() );
+                       }
 
                        // If the theme isn't allowed per multisite settings, bail.
-                       if ( ! $this->theme()->is_allowed() )
-                               $this->wp_die( -1 );
+                       if ( ! $this->theme()->is_allowed() ) {
+                               $this->wp_die( -1, __( 'The requested theme does not exist.' ) );
+                       }
                }
 
                $this->start_previewing_theme();
@@ -193,7 +424,8 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         */
        public function after_setup_theme() {
-               if ( ! $this->doing_ajax() && ! validate_current_theme() ) {
+               $doing_ajax_or_is_customized = ( $this->doing_ajax() || isset( $_POST['customized'] ) );
+               if ( ! $doing_ajax_or_is_customized && ! validate_current_theme() ) {
                        wp_redirect( 'themes.php?broken=true' );
                        exit;
                }
@@ -207,8 +439,9 @@ final class WP_Customize_Manager {
         */
        public function start_previewing_theme() {
                // Bail if we're already previewing.
-               if ( $this->is_preview() )
+               if ( $this->is_preview() ) {
                        return;
+               }
 
                $this->previewing = true;
 
@@ -217,7 +450,7 @@ final class WP_Customize_Manager {
                        add_filter( 'stylesheet', array( $this, 'get_stylesheet' ) );
                        add_filter( 'pre_option_current_theme', array( $this, 'current_theme' ) );
 
-                       // @link: http://core.trac.wordpress.org/ticket/20027
+                       // @link: https://core.trac.wordpress.org/ticket/20027
                        add_filter( 'pre_option_stylesheet', array( $this, 'get_stylesheet' ) );
                        add_filter( 'pre_option_template', array( $this, 'get_template' ) );
 
@@ -244,8 +477,9 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         */
        public function stop_previewing_theme() {
-               if ( ! $this->is_preview() )
+               if ( ! $this->is_preview() ) {
                        return;
+               }
 
                $this->previewing = false;
 
@@ -254,7 +488,7 @@ final class WP_Customize_Manager {
                        remove_filter( 'stylesheet', array( $this, 'get_stylesheet' ) );
                        remove_filter( 'pre_option_current_theme', array( $this, 'current_theme' ) );
 
-                       // @link: http://core.trac.wordpress.org/ticket/20027
+                       // @link: https://core.trac.wordpress.org/ticket/20027
                        remove_filter( 'pre_option_stylesheet', array( $this, 'get_stylesheet' ) );
                        remove_filter( 'pre_option_template', array( $this, 'get_template' ) );
 
@@ -281,6 +515,9 @@ final class WP_Customize_Manager {
         * @return WP_Theme
         */
        public function theme() {
+               if ( ! $this->theme ) {
+                       $this->theme = wp_get_theme();
+               }
                return $this->theme;
        }
 
@@ -372,7 +609,7 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Prevents AJAX requests from following redirects when previewing a theme
+        * Prevents Ajax requests from following redirects when previewing a theme
         * by issuing a 200 response instead of a 30x.
         *
         * Instead, the JS will sniff out the location header.
@@ -390,27 +627,109 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Decode the $_POST['customized'] values for a specific Customize Setting.
+        * Parse the incoming $_POST['customized'] JSON data and store the unsanitized
+        * settings for subsequent post_value() lookups.
         *
-        * @since 3.4.0
+        * @since 4.1.1
         *
-        * @param mixed $setting A WP_Customize_Setting derived object
-        * @return string $post_value Sanitized value
+        * @return array
         */
-       public function post_value( $setting ) {
+       public function unsanitized_post_values() {
                if ( ! isset( $this->_post_values ) ) {
-                       if ( isset( $_POST['customized'] ) )
+                       if ( isset( $_POST['customized'] ) ) {
                                $this->_post_values = json_decode( wp_unslash( $_POST['customized'] ), true );
-                       else
-                               $this->_post_values = false;
+                       }
+                       if ( empty( $this->_post_values ) ) { // if not isset or if JSON error
+                               $this->_post_values = array();
+                       }
+               }
+               if ( empty( $this->_post_values ) ) {
+                       return array();
+               } else {
+                       return $this->_post_values;
+               }
+       }
+
+       /**
+        * Returns the sanitized value for a given setting from the request's POST data.
+        *
+        * @since 3.4.0
+        * @since 4.1.1 Introduced the `$default` parameter.
+        * @since 4.6.0 `$default` is now returned early when the setting post value is invalid.
+        * @access public
+        *
+        * @see WP_REST_Server::dispatch()
+        * @see WP_Rest_Request::sanitize_params()
+        * @see WP_Rest_Request::has_valid_params()
+        *
+        * @param WP_Customize_Setting $setting A WP_Customize_Setting derived object.
+        * @param mixed                $default Value returned $setting has no post value (added in 4.2.0)
+        *                                      or the post value is invalid (added in 4.6.0).
+        * @return string|mixed $post_value Sanitized value or the $default provided.
+        */
+       public function post_value( $setting, $default = null ) {
+               $post_values = $this->unsanitized_post_values();
+               if ( ! array_key_exists( $setting->id, $post_values ) ) {
+                       return $default;
+               }
+               $value = $post_values[ $setting->id ];
+               $valid = $setting->validate( $value );
+               if ( is_wp_error( $valid ) ) {
+                       return $default;
+               }
+               $value = $setting->sanitize( $value );
+               if ( is_null( $value ) || is_wp_error( $value ) ) {
+                       return $default;
                }
+               return $value;
+       }
+
+       /**
+        * Override a setting's (unsanitized) value as found in any incoming $_POST['customized'].
+        *
+        * @since 4.2.0
+        * @access public
+        *
+        * @param string $setting_id ID for the WP_Customize_Setting instance.
+        * @param mixed  $value      Post value.
+        */
+       public function set_post_value( $setting_id, $value ) {
+               $this->unsanitized_post_values();
+               $this->_post_values[ $setting_id ] = $value;
+
+               /**
+                * Announce when a specific setting's unsanitized post value has been set.
+                *
+                * Fires when the WP_Customize_Manager::set_post_value() method is called.
+                *
+                * The dynamic portion of the hook name, `$setting_id`, refers to the setting ID.
+                *
+                * @since 4.4.0
+                *
+                * @param mixed                $value Unsanitized setting post value.
+                * @param WP_Customize_Manager $this  WP_Customize_Manager instance.
+                */
+               do_action( "customize_post_value_set_{$setting_id}", $value, $this );
 
-               if ( isset( $this->_post_values[ $setting->id ] ) )
-                       return $setting->sanitize( $this->_post_values[ $setting->id ] );
+               /**
+                * Announce when any setting's unsanitized post value has been set.
+                *
+                * Fires when the WP_Customize_Manager::set_post_value() method is called.
+                *
+                * This is useful for `WP_Customize_Setting` instances to watch
+                * in order to update a cached previewed value.
+                *
+                * @since 4.4.0
+                *
+                * @param string               $setting_id Setting ID.
+                * @param mixed                $value      Unsanitized setting post value.
+                * @param WP_Customize_Manager $this       WP_Customize_Manager instance.
+                */
+               do_action( 'customize_post_value_set', $setting_id, $value, $this );
        }
 
        /**
-        * Print javascript settings.
+        * Print JavaScript settings.
         *
         * @since 3.4.0
         */
@@ -423,6 +742,7 @@ final class WP_Customize_Manager {
                add_action( 'wp', array( $this, 'customize_preview_override_404_status' ) );
                add_action( 'wp_head', array( $this, 'customize_preview_base' ) );
                add_action( 'wp_head', array( $this, 'customize_preview_html5' ) );
+               add_action( 'wp_head', array( $this, 'customize_preview_loading_style' ) );
                add_action( 'wp_footer', array( $this, 'customize_preview_settings' ), 20 );
                add_action( 'shutdown', array( $this, 'customize_preview_signature' ), 1000 );
                add_filter( 'wp_die_handler', array( $this, 'remove_preview_signature' ) );
@@ -444,7 +764,7 @@ final class WP_Customize_Manager {
 
        /**
         * Prevent sending a 404 status when returning the response for the customize
-        * preview, since it causes the jQuery AJAX to fail. Send 200 instead.
+        * preview, since it causes the jQuery Ajax to fail. Send 200 instead.
         *
         * @since 4.0.0
         * @access public
@@ -465,7 +785,7 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Print a workaround to handle HTML5 tags in IE < 9
+        * Print a workaround to handle HTML5 tags in IE < 9.
         *
         * @since 3.4.0
         */
@@ -483,40 +803,103 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Print javascript settings for preview frame.
+        * Print CSS for loading indicators for the Customizer preview.
+        *
+        * @since 4.2.0
+        * @access public
+        */
+       public function customize_preview_loading_style() {
+               ?><style>
+                       body.wp-customizer-unloading {
+                               opacity: 0.25;
+                               cursor: progress !important;
+                               -webkit-transition: opacity 0.5s;
+                               transition: opacity 0.5s;
+                       }
+                       body.wp-customizer-unloading * {
+                               pointer-events: none !important;
+                       }
+               </style><?php
+       }
+
+       /**
+        * Print JavaScript settings for preview frame.
         *
         * @since 3.4.0
         */
        public function customize_preview_settings() {
+               $setting_validities = $this->validate_setting_values( $this->unsanitized_post_values() );
+               $exported_setting_validities = array_map( array( $this, 'prepare_setting_validity_for_js' ), $setting_validities );
+
                $settings = array(
-                       'values'  => array(),
+                       'theme' => array(
+                               'stylesheet' => $this->get_stylesheet(),
+                               'active'     => $this->is_theme_active(),
+                       ),
+                       'url' => array(
+                               'self' => empty( $_SERVER['REQUEST_URI'] ) ? home_url( '/' ) : esc_url_raw( wp_unslash( $_SERVER['REQUEST_URI'] ) ),
+                       ),
                        'channel' => wp_unslash( $_POST['customize_messenger_channel'] ),
+                       'activePanels' => array(),
+                       'activeSections' => array(),
                        'activeControls' => array(),
+                       'settingValidities' => $exported_setting_validities,
+                       'nonce' => $this->get_nonces(),
+                       'l10n' => array(
+                               'shiftClickToEdit' => __( 'Shift-click to edit this element.' ),
+                       ),
+                       '_dirty' => array_keys( $this->unsanitized_post_values() ),
                );
 
-               if ( 2 == $this->nonce_tick ) {
-                       $settings['nonce'] = array(
-                               'save' => wp_create_nonce( 'save-customize_' . $this->get_stylesheet() ),
-                               'preview' => wp_create_nonce( 'preview-customize_' . $this->get_stylesheet() )
-                       );
+               foreach ( $this->panels as $panel_id => $panel ) {
+                       if ( $panel->check_capabilities() ) {
+                               $settings['activePanels'][ $panel_id ] = $panel->active();
+                               foreach ( $panel->sections as $section_id => $section ) {
+                                       if ( $section->check_capabilities() ) {
+                                               $settings['activeSections'][ $section_id ] = $section->active();
+                                       }
+                               }
+                       }
                }
-
-               foreach ( $this->settings as $id => $setting ) {
-                       $settings['values'][ $id ] = $setting->js_value();
+               foreach ( $this->sections as $id => $section ) {
+                       if ( $section->check_capabilities() ) {
+                               $settings['activeSections'][ $id ] = $section->active();
+                       }
                }
                foreach ( $this->controls as $id => $control ) {
-                       $settings['activeControls'][ $id ] = $control->active();
+                       if ( $control->check_capabilities() ) {
+                               $settings['activeControls'][ $id ] = $control->active();
+                       }
                }
 
                ?>
                <script type="text/javascript">
-                       var _wpCustomizeSettings = <?php echo json_encode( $settings ); ?>;
+                       var _wpCustomizeSettings = <?php echo wp_json_encode( $settings ); ?>;
+                       _wpCustomizeSettings.values = {};
+                       (function( v ) {
+                               <?php
+                               /*
+                                * Serialize settings separately from the initial _wpCustomizeSettings
+                                * serialization in order to avoid a peak memory usage spike.
+                                * @todo We may not even need to export the values at all since the pane syncs them anyway.
+                                */
+                               foreach ( $this->settings as $id => $setting ) {
+                                       if ( $setting->check_capabilities() ) {
+                                               printf(
+                                                       "v[%s] = %s;\n",
+                                                       wp_json_encode( $id ),
+                                                       wp_json_encode( $setting->js_value() )
+                                               );
+                                       }
+                               }
+                               ?>
+                       })( _wpCustomizeSettings.values );
                </script>
                <?php
        }
 
        /**
-        * Prints a signature so we can ensure the customizer was properly executed.
+        * Prints a signature so we can ensure the Customizer was properly executed.
         *
         * @since 3.4.0
         */
@@ -525,9 +908,12 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Removes the signature in case we experience a case where the customizer was not properly executed.
+        * Removes the signature in case we experience a case where the Customizer was not properly executed.
         *
         * @since 3.4.0
+        *
+        * @param mixed $return Value passed through for {@see 'wp_die_handler'} filter.
+        * @return mixed Value passed through for {@see 'wp_die_handler'} filter.
         */
        public function remove_preview_signature( $return = null ) {
                remove_action( 'shutdown', array( $this, 'customize_preview_signature' ), 1000 );
@@ -591,7 +977,7 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Filter the current theme and return the name of the previewed theme.
+        * Filters the current theme and return the name of the previewed theme.
         *
         * @since 3.4.0
         *
@@ -602,16 +988,125 @@ final class WP_Customize_Manager {
                return $this->theme()->display('Name');
        }
 
+       /**
+        * Validates setting values.
+        *
+        * Sanitization is applied to the values before being passed for validation.
+        * Validation is skipped for unregistered settings or for values that are
+        * already null since they will be skipped anyway.
+        *
+        * @since 4.6.0
+        * @access public
+        *
+        * @see WP_REST_Request::has_valid_params()
+        * @see WP_Customize_Setting::validate()
+        *
+        * @param array $setting_values Mapping of setting IDs to values to sanitize and validate.
+        * @return array Mapping of setting IDs to return value of validate method calls, either `true` or `WP_Error`.
+        */
+       public function validate_setting_values( $setting_values ) {
+               $validities = array();
+               foreach ( $setting_values as $setting_id => $unsanitized_value ) {
+                       $setting = $this->get_setting( $setting_id );
+                       if ( ! $setting || is_null( $unsanitized_value ) ) {
+                               continue;
+                       }
+                       $validity = $setting->validate( $unsanitized_value );
+                       if ( ! is_wp_error( $validity ) ) {
+                               $value = $setting->sanitize( $unsanitized_value );
+                               if ( is_null( $value ) ) {
+                                       $validity = false;
+                               } elseif ( is_wp_error( $value ) ) {
+                                       $validity = $value;
+                               }
+                       }
+                       if ( false === $validity ) {
+                               $validity = new WP_Error( 'invalid_value', __( 'Invalid value.' ) );
+                       }
+                       $validities[ $setting_id ] = $validity;
+               }
+               return $validities;
+       }
+
+       /**
+        * Prepares setting validity for exporting to the client (JS).
+        *
+        * Converts `WP_Error` instance into array suitable for passing into the
+        * `wp.customize.Notification` JS model.
+        *
+        * @since 4.6.0
+        * @access public
+        *
+        * @param true|WP_Error $validity Setting validity.
+        * @return true|array If `$validity` was a WP_Error, the error codes will be array-mapped
+        *                    to their respective `message` and `data` to pass into the
+        *                    `wp.customize.Notification` JS model.
+        */
+       public function prepare_setting_validity_for_js( $validity ) {
+               if ( is_wp_error( $validity ) ) {
+                       $notification = array();
+                       foreach ( $validity->errors as $error_code => $error_messages ) {
+                               $error_data = $validity->get_error_data( $error_code );
+                               if ( is_null( $error_data ) ) {
+                                       $error_data = array();
+                               }
+                               $error_data = array_merge(
+                                       $error_data,
+                                       array( 'from_server' => true )
+                               );
+                               $notification[ $error_code ] = array(
+                                       'message' => join( ' ', $error_messages ),
+                                       'data' => $error_data,
+                               );
+                       }
+                       return $notification;
+               } else {
+                       return true;
+               }
+       }
+
        /**
         * Switch the theme and trigger the save() method on each setting.
         *
         * @since 3.4.0
         */
        public function save() {
-               if ( ! $this->is_preview() )
-                       die;
+               if ( ! $this->is_preview() ) {
+                       wp_send_json_error( 'not_preview' );
+               }
+
+               $action = 'save-customize_' . $this->get_stylesheet();
+               if ( ! check_ajax_referer( $action, 'nonce', false ) ) {
+                       wp_send_json_error( 'invalid_nonce' );
+               }
+
+               /**
+                * Fires before save validation happens.
+                *
+                * Plugins can add just-in-time {@see 'customize_validate_{$this->ID}'} filters
+                * at this point to catch any settings registered after `customize_register`.
+                * The dynamic portion of the hook name, `$this->ID` refers to the setting ID.
+                *
+                * @since 4.6.0
+                *
+                * @param WP_Customize_Manager $this WP_Customize_Manager instance.
+                */
+               do_action( 'customize_save_validation_before', $this );
+
+               // Validate settings.
+               $setting_validities = $this->validate_setting_values( $this->unsanitized_post_values() );
+               $invalid_setting_count = count( array_filter( $setting_validities, 'is_wp_error' ) );
+               $exported_setting_validities = array_map( array( $this, 'prepare_setting_validity_for_js' ), $setting_validities );
+               if ( $invalid_setting_count > 0 ) {
+                       $response = array(
+                               'setting_validities' => $exported_setting_validities,
+                               'message' => sprintf( _n( 'There is %s invalid setting.', 'There are %s invalid settings.', $invalid_setting_count ), number_format_i18n( $invalid_setting_count ) ),
+                       );
 
-               check_ajax_referer( 'save-customize_' . $this->get_stylesheet(), 'nonce' );
+                       /** This filter is documented in wp-includes/class-wp-customize-manager.php */
+                       $response = apply_filters( 'customize_save_response', $response, $this );
+                       wp_send_json_error( $response );
+               }
 
                // Do we have to switch themes?
                if ( ! $this->is_theme_active() ) {
@@ -646,25 +1141,129 @@ final class WP_Customize_Manager {
                 */
                do_action( 'customize_save_after', $this );
 
-               die;
+               $data = array(
+                       'setting_validities' => $exported_setting_validities,
+               );
+
+               /**
+                * Filters response data for a successful customize_save Ajax request.
+                *
+                * This filter does not apply if there was a nonce or authentication failure.
+                *
+                * @since 4.2.0
+                *
+                * @param array                $data Additional information passed back to the 'saved'
+                *                                   event on `wp.customize`.
+                * @param WP_Customize_Manager $this WP_Customize_Manager instance.
+                */
+               $response = apply_filters( 'customize_save_response', $data, $this );
+               wp_send_json_success( $response );
+       }
+
+       /**
+        * Refresh nonces for the current preview.
+        *
+        * @since 4.2.0
+        */
+       public function refresh_nonces() {
+               if ( ! $this->is_preview() ) {
+                       wp_send_json_error( 'not_preview' );
+               }
+
+               wp_send_json_success( $this->get_nonces() );
        }
 
        /**
         * Add a customize setting.
         *
         * @since 3.4.0
+        * @since 4.5.0 Return added WP_Customize_Setting instance.
+        * @access public
         *
-        * @param WP_Customize_Setting|string $id Customize Setting object, or ID.
-        * @param array $args                     Setting arguments; passed to WP_Customize_Setting
-        *                                        constructor.
+        * @param WP_Customize_Setting|string $id   Customize Setting object, or ID.
+        * @param array                       $args Setting arguments; passed to WP_Customize_Setting
+        *                                          constructor.
+        * @return WP_Customize_Setting             The instance of the setting that was added.
         */
        public function add_setting( $id, $args = array() ) {
-               if ( is_a( $id, 'WP_Customize_Setting' ) )
+               if ( $id instanceof WP_Customize_Setting ) {
                        $setting = $id;
-               else
-                       $setting = new WP_Customize_Setting( $this, $id, $args );
+               } else {
+                       $class = 'WP_Customize_Setting';
+
+                       /** This filter is documented in wp-includes/class-wp-customize-manager.php */
+                       $args = apply_filters( 'customize_dynamic_setting_args', $args, $id );
+
+                       /** This filter is documented in wp-includes/class-wp-customize-manager.php */
+                       $class = apply_filters( 'customize_dynamic_setting_class', $class, $id, $args );
+
+                       $setting = new $class( $this, $id, $args );
+               }
 
                $this->settings[ $setting->id ] = $setting;
+               return $setting;
+       }
+
+       /**
+        * Register any dynamically-created settings, such as those from $_POST['customized']
+        * that have no corresponding setting created.
+        *
+        * This is a mechanism to "wake up" settings that have been dynamically created
+        * on the front end and have been sent to WordPress in `$_POST['customized']`. When WP
+        * loads, the dynamically-created settings then will get created and previewed
+        * even though they are not directly created statically with code.
+        *
+        * @since 4.2.0
+        * @access public
+        *
+        * @param array $setting_ids The setting IDs to add.
+        * @return array The WP_Customize_Setting objects added.
+        */
+       public function add_dynamic_settings( $setting_ids ) {
+               $new_settings = array();
+               foreach ( $setting_ids as $setting_id ) {
+                       // Skip settings already created
+                       if ( $this->get_setting( $setting_id ) ) {
+                               continue;
+                       }
+
+                       $setting_args = false;
+                       $setting_class = 'WP_Customize_Setting';
+
+                       /**
+                        * Filters a dynamic setting's constructor args.
+                        *
+                        * For a dynamic setting to be registered, this filter must be employed
+                        * to override the default false value with an array of args to pass to
+                        * the WP_Customize_Setting constructor.
+                        *
+                        * @since 4.2.0
+                        *
+                        * @param false|array $setting_args The arguments to the WP_Customize_Setting constructor.
+                        * @param string      $setting_id   ID for dynamic setting, usually coming from `$_POST['customized']`.
+                        */
+                       $setting_args = apply_filters( 'customize_dynamic_setting_args', $setting_args, $setting_id );
+                       if ( false === $setting_args ) {
+                               continue;
+                       }
+
+                       /**
+                        * Allow non-statically created settings to be constructed with custom WP_Customize_Setting subclass.
+                        *
+                        * @since 4.2.0
+                        *
+                        * @param string $setting_class WP_Customize_Setting or a subclass.
+                        * @param string $setting_id    ID for dynamic setting, usually coming from `$_POST['customized']`.
+                        * @param array  $setting_args  WP_Customize_Setting or a subclass.
+                        */
+                       $setting_class = apply_filters( 'customize_dynamic_setting_class', $setting_class, $setting_id, $setting_args );
+
+                       $setting = new $setting_class( $this, $setting_id, $setting_args );
+
+                       $this->add_setting( $setting );
+                       $new_settings[] = $setting;
+               }
+               return $new_settings;
        }
 
        /**
@@ -673,11 +1272,12 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         *
         * @param string $id Customize Setting ID.
-        * @return WP_Customize_Setting
+        * @return WP_Customize_Setting|void The setting, if set.
         */
        public function get_setting( $id ) {
-               if ( isset( $this->settings[ $id ] ) )
+               if ( isset( $this->settings[ $id ] ) ) {
                        return $this->settings[ $id ];
+               }
        }
 
        /**
@@ -695,20 +1295,23 @@ final class WP_Customize_Manager {
         * Add a customize panel.
         *
         * @since 4.0.0
+        * @since 4.5.0 Return added WP_Customize_Panel instance.
         * @access public
         *
         * @param WP_Customize_Panel|string $id   Customize Panel object, or Panel ID.
         * @param array                     $args Optional. Panel arguments. Default empty array.
+        *
+        * @return WP_Customize_Panel             The instance of the panel that was added.
         */
        public function add_panel( $id, $args = array() ) {
-               if ( is_a( $id, 'WP_Customize_Panel' ) ) {
+               if ( $id instanceof WP_Customize_Panel ) {
                        $panel = $id;
-               }
-               else {
+               } else {
                        $panel = new WP_Customize_Panel( $this, $id, $args );
                }
 
                $this->panels[ $panel->id ] = $panel;
+               return $panel;
        }
 
        /**
@@ -718,7 +1321,7 @@ final class WP_Customize_Manager {
         * @access public
         *
         * @param string $id Panel ID to get.
-        * @return WP_Customize_Panel Requested panel instance.
+        * @return WP_Customize_Panel|void Requested panel instance, if set.
         */
        public function get_panel( $id ) {
                if ( isset( $this->panels[ $id ] ) ) {
@@ -735,24 +1338,69 @@ final class WP_Customize_Manager {
         * @param string $id Panel ID to remove.
         */
        public function remove_panel( $id ) {
+               // Removing core components this way is _doing_it_wrong().
+               if ( in_array( $id, $this->components, true ) ) {
+                       /* translators: 1: panel id, 2: link to 'customize_loaded_components' filter reference */
+                       $message = sprintf( __( 'Removing %1$s manually will cause PHP warnings. Use the %2$s filter instead.' ),
+                               $id,
+                               '<a href="' . esc_url( 'https://developer.wordpress.org/reference/hooks/customize_loaded_components/' ) . '"><code>customize_loaded_components</code></a>'
+                       );
+
+                       _doing_it_wrong( __METHOD__, $message, '4.5.0' );
+               }
                unset( $this->panels[ $id ] );
        }
 
+       /**
+        * Register a customize panel type.
+        *
+        * Registered types are eligible to be rendered via JS and created dynamically.
+        *
+        * @since 4.3.0
+        * @access public
+        *
+        * @see WP_Customize_Panel
+        *
+        * @param string $panel Name of a custom panel which is a subclass of WP_Customize_Panel.
+        */
+       public function register_panel_type( $panel ) {
+               $this->registered_panel_types[] = $panel;
+       }
+
+       /**
+        * Render JS templates for all registered panel types.
+        *
+        * @since 4.3.0
+        * @access public
+        */
+       public function render_panel_templates() {
+               foreach ( $this->registered_panel_types as $panel_type ) {
+                       $panel = new $panel_type( $this, 'temp', array() );
+                       $panel->print_template();
+               }
+       }
+
        /**
         * Add a customize section.
         *
         * @since 3.4.0
+        * @since 4.5.0 Return added WP_Customize_Section instance.
+        * @access public
         *
         * @param WP_Customize_Section|string $id   Customize Section object, or Section ID.
         * @param array                       $args Section arguments.
+        *
+        * @return WP_Customize_Section             The instance of the section that was added.
         */
        public function add_section( $id, $args = array() ) {
-               if ( is_a( $id, 'WP_Customize_Section' ) )
+               if ( $id instanceof WP_Customize_Section ) {
                        $section = $id;
-               else
+               } else {
                        $section = new WP_Customize_Section( $this, $id, $args );
+               }
 
                $this->sections[ $section->id ] = $section;
+               return $section;
        }
 
        /**
@@ -761,7 +1409,7 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         *
         * @param string $id Section ID.
-        * @return WP_Customize_Section
+        * @return WP_Customize_Section|void The section, if set.
         */
        public function get_section( $id ) {
                if ( isset( $this->sections[ $id ] ) )
@@ -779,22 +1427,56 @@ final class WP_Customize_Manager {
                unset( $this->sections[ $id ] );
        }
 
+       /**
+        * Register a customize section type.
+        *
+        * Registered types are eligible to be rendered via JS and created dynamically.
+        *
+        * @since 4.3.0
+        * @access public
+        *
+        * @see WP_Customize_Section
+        *
+        * @param string $section Name of a custom section which is a subclass of WP_Customize_Section.
+        */
+       public function register_section_type( $section ) {
+               $this->registered_section_types[] = $section;
+       }
+
+       /**
+        * Render JS templates for all registered section types.
+        *
+        * @since 4.3.0
+        * @access public
+        */
+       public function render_section_templates() {
+               foreach ( $this->registered_section_types as $section_type ) {
+                       $section = new $section_type( $this, 'temp', array() );
+                       $section->print_template();
+               }
+       }
+
        /**
         * Add a customize control.
         *
         * @since 3.4.0
+        * @since 4.5.0 Return added WP_Customize_Control instance.
+        * @access public
         *
         * @param WP_Customize_Control|string $id   Customize Control object, or ID.
         * @param array                       $args Control arguments; passed to WP_Customize_Control
         *                                          constructor.
+        * @return WP_Customize_Control             The instance of the control that was added.
         */
        public function add_control( $id, $args = array() ) {
-               if ( is_a( $id, 'WP_Customize_Control' ) )
+               if ( $id instanceof WP_Customize_Control ) {
                        $control = $id;
-               else
+               } else {
                        $control = new WP_Customize_Control( $this, $id, $args );
+               }
 
                $this->controls[ $control->id ] = $control;
+               return $control;
        }
 
        /**
@@ -803,7 +1485,7 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         *
         * @param string $id ID of the control.
-        * @return WP_Customize_Control $control The control object.
+        * @return WP_Customize_Control|void The control object, if set.
         */
        public function get_control( $id ) {
                if ( isset( $this->controls[ $id ] ) )
@@ -822,21 +1504,59 @@ final class WP_Customize_Manager {
        }
 
        /**
-        * Helper function to compare two objects by priority.
+        * Register a customize control type.
+        *
+        * Registered types are eligible to be rendered via JS and created dynamically.
+        *
+        * @since 4.1.0
+        * @access public
+        *
+        * @param string $control Name of a custom control which is a subclass of
+        *                        WP_Customize_Control.
+        */
+       public function register_control_type( $control ) {
+               $this->registered_control_types[] = $control;
+       }
+
+       /**
+        * Render JS templates for all registered control types.
+        *
+        * @since 4.1.0
+        * @access public
+        */
+       public function render_control_templates() {
+               foreach ( $this->registered_control_types as $control_type ) {
+                       $control = new $control_type( $this, 'temp', array(
+                               'settings' => array(),
+                       ) );
+                       $control->print_template();
+               }
+               ?>
+               <script type="text/html" id="tmpl-customize-control-notifications">
+                       <ul>
+                               <# _.each( data.notifications, function( notification ) { #>
+                                       <li class="notice notice-{{ notification.type || 'info' }} {{ data.altNotice ? 'notice-alt' : '' }}" data-code="{{ notification.code }}" data-type="{{ notification.type }}">{{ notification.message || notification.code }}</li>
+                               <# } ); #>
+                       </ul>
+               </script>
+               <?php
+       }
+
+       /**
+        * Helper function to compare two objects by priority, ensuring sort stability via instance_number.
         *
         * @since 3.4.0
         *
-        * @param object $a Object A.
-        * @param object $b Object B.
+        * @param WP_Customize_Panel|WP_Customize_Section|WP_Customize_Control $a Object A.
+        * @param WP_Customize_Panel|WP_Customize_Section|WP_Customize_Control $b Object B.
         * @return int
         */
-       protected final function _cmp_priority( $a, $b ) {
-               $ap = $a->priority;
-               $bp = $b->priority;
-
-               if ( $ap == $bp )
-                       return 0;
-               return ( $ap > $bp ) ? 1 : -1;
+       protected function _cmp_priority( $a, $b ) {
+               if ( $a->priority === $b->priority ) {
+                       return $a->instance_number - $b->instance_number;
+               } else {
+                       return $a->priority - $b->priority;
+               }
        }
 
        /**
@@ -850,8 +1570,8 @@ final class WP_Customize_Manager {
         */
        public function prepare_controls() {
 
-               $this->controls = array_reverse( $this->controls );
                $controls = array();
+               uasort( $this->controls, array( $this, '_cmp_priority' ) );
 
                foreach ( $this->controls as $id => $control ) {
                        if ( ! isset( $this->sections[ $control->section ] ) || ! $control->check_capabilities() ) {
@@ -864,13 +1584,11 @@ final class WP_Customize_Manager {
                $this->controls = $controls;
 
                // Prepare sections.
-               // Reversing makes uasort sort by time added when conflicts occur.
-               $this->sections = array_reverse( $this->sections );
                uasort( $this->sections, array( $this, '_cmp_priority' ) );
                $sections = array();
 
                foreach ( $this->sections as $section ) {
-                       if ( ! $section->check_capabilities() || ! $section->controls ) {
+                       if ( ! $section->check_capabilities() ) {
                                continue;
                        }
 
@@ -878,29 +1596,27 @@ final class WP_Customize_Manager {
 
                        if ( ! $section->panel ) {
                                // Top-level section.
-                               $sections[] = $section;
+                               $sections[ $section->id ] = $section;
                        } else {
                                // This section belongs to a panel.
                                if ( isset( $this->panels [ $section->panel ] ) ) {
-                                       $this->panels[ $section->panel ]->sections[] = $section;
+                                       $this->panels[ $section->panel ]->sections[ $section->id ] = $section;
                                }
                        }
                }
                $this->sections = $sections;
 
                // Prepare panels.
-               // Reversing makes uasort sort by time added when conflicts occur.
-               $this->panels = array_reverse( $this->panels );
                uasort( $this->panels, array( $this, '_cmp_priority' ) );
                $panels = array();
 
                foreach ( $this->panels as $panel ) {
-                       if ( ! $panel->check_capabilities() || ! $panel->sections ) {
+                       if ( ! $panel->check_capabilities() ) {
                                continue;
                        }
 
-                       usort( $panel->sections, array( $this, '_cmp_priority' ) );
-                       $panels[] = $panel;
+                       uasort( $panel->sections, array( $this, '_cmp_priority' ) );
+                       $panels[ $panel->id ] = $panel;
                }
                $this->panels = $panels;
 
@@ -920,6 +1636,331 @@ final class WP_Customize_Manager {
                }
        }
 
+       /**
+        * Determine whether the user agent is iOS.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @return bool Whether the user agent is iOS.
+        */
+       public function is_ios() {
+               return wp_is_mobile() && preg_match( '/iPad|iPod|iPhone/', $_SERVER['HTTP_USER_AGENT'] );
+       }
+
+       /**
+        * Get the template string for the Customizer pane document title.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @return string The template string for the document title.
+        */
+       public function get_document_title_template() {
+               if ( $this->is_theme_active() ) {
+                       /* translators: %s: document title from the preview */
+                       $document_title_tmpl = __( 'Customize: %s' );
+               } else {
+                       /* translators: %s: document title from the preview */
+                       $document_title_tmpl = __( 'Live Preview: %s' );
+               }
+               $document_title_tmpl = html_entity_decode( $document_title_tmpl, ENT_QUOTES, 'UTF-8' ); // Because exported to JS and assigned to document.title.
+               return $document_title_tmpl;
+       }
+
+       /**
+        * Set the initial URL to be previewed.
+        *
+        * URL is validated.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @param string $preview_url URL to be previewed.
+        */
+       public function set_preview_url( $preview_url ) {
+               $preview_url = esc_url_raw( $preview_url );
+               $this->preview_url = wp_validate_redirect( $preview_url, home_url( '/' ) );
+       }
+
+       /**
+        * Get the initial URL to be previewed.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @return string URL being previewed.
+        */
+       public function get_preview_url() {
+               if ( empty( $this->preview_url ) ) {
+                       $preview_url = home_url( '/' );
+               } else {
+                       $preview_url = $this->preview_url;
+               }
+               return $preview_url;
+       }
+
+       /**
+        * Set URL to link the user to when closing the Customizer.
+        *
+        * URL is validated.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @param string $return_url URL for return link.
+        */
+       public function set_return_url( $return_url ) {
+               $return_url = esc_url_raw( $return_url );
+               $return_url = remove_query_arg( wp_removable_query_args(), $return_url );
+               $return_url = wp_validate_redirect( $return_url );
+               $this->return_url = $return_url;
+       }
+
+       /**
+        * Get URL to link the user to when closing the Customizer.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @return string URL for link to close Customizer.
+        */
+       public function get_return_url() {
+               $referer = wp_get_referer();
+               $excluded_referer_basenames = array( 'customize.php', 'wp-login.php' );
+
+               if ( $this->return_url ) {
+                       $return_url = $this->return_url;
+               } else if ( $referer && ! in_array( basename( parse_url( $referer, PHP_URL_PATH ) ), $excluded_referer_basenames, true ) ) {
+                       $return_url = $referer;
+               } else if ( $this->preview_url ) {
+                       $return_url = $this->preview_url;
+               } else {
+                       $return_url = home_url( '/' );
+               }
+               return $return_url;
+       }
+
+       /**
+        * Set the autofocused constructs.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @param array $autofocus {
+        *     Mapping of 'panel', 'section', 'control' to the ID which should be autofocused.
+        *
+        *     @type string [$control]  ID for control to be autofocused.
+        *     @type string [$section]  ID for section to be autofocused.
+        *     @type string [$panel]    ID for panel to be autofocused.
+        * }
+        */
+       public function set_autofocus( $autofocus ) {
+               $this->autofocus = array_filter( wp_array_slice_assoc( $autofocus, array( 'panel', 'section', 'control' ) ), 'is_string' );
+       }
+
+       /**
+        * Get the autofocused constructs.
+        *
+        * @since 4.4.0
+        * @access public
+        *
+        * @return array {
+        *     Mapping of 'panel', 'section', 'control' to the ID which should be autofocused.
+        *
+        *     @type string [$control]  ID for control to be autofocused.
+        *     @type string [$section]  ID for section to be autofocused.
+        *     @type string [$panel]    ID for panel to be autofocused.
+        * }
+        */
+       public function get_autofocus() {
+               return $this->autofocus;
+       }
+
+       /**
+        * Get nonces for the Customizer.
+        *
+        * @since 4.5.0
+        * @return array Nonces.
+        */
+       public function get_nonces() {
+               $nonces = array(
+                       'save' => wp_create_nonce( 'save-customize_' . $this->get_stylesheet() ),
+                       'preview' => wp_create_nonce( 'preview-customize_' . $this->get_stylesheet() ),
+               );
+
+               /**
+                * Filters nonces for Customizer.
+                *
+                * @since 4.2.0
+                *
+                * @param array                $nonces Array of refreshed nonces for save and
+                *                                     preview actions.
+                * @param WP_Customize_Manager $this   WP_Customize_Manager instance.
+                */
+               $nonces = apply_filters( 'customize_refresh_nonces', $nonces, $this );
+
+               return $nonces;
+       }
+
+       /**
+        * Print JavaScript settings for parent window.
+        *
+        * @since 4.4.0
+        */
+       public function customize_pane_settings() {
+               /*
+                * If the front end and the admin are served from the same domain, load the
+                * preview over ssl if the Customizer is being loaded over ssl. This avoids
+                * insecure content warnings. This is not attempted if the admin and front end
+                * are on different domains to avoid the case where the front end doesn't have
+                * ssl certs. Domain mapping plugins can allow other urls in these conditions
+                * using the customize_allowed_urls filter.
+                */
+
+               $allowed_urls = array( home_url( '/' ) );
+               $admin_origin = parse_url( admin_url() );
+               $home_origin  = parse_url( home_url() );
+               $cross_domain = ( strtolower( $admin_origin['host'] ) !== strtolower( $home_origin['host'] ) );
+
+               if ( is_ssl() && ! $cross_domain ) {
+                       $allowed_urls[] = home_url( '/', 'https' );
+               }
+
+               /**
+                * Filters the list of URLs allowed to be clicked and followed in the Customizer preview.
+                *
+                * @since 3.4.0
+                *
+                * @param array $allowed_urls An array of allowed URLs.
+                */
+               $allowed_urls = array_unique( apply_filters( 'customize_allowed_urls', $allowed_urls ) );
+
+               $login_url = add_query_arg( array(
+                       'interim-login' => 1,
+                       'customize-login' => 1,
+               ), wp_login_url() );
+
+               // Prepare Customizer settings to pass to JavaScript.
+               $settings = array(
+                       'theme'    => array(
+                               'stylesheet' => $this->get_stylesheet(),
+                               'active'     => $this->is_theme_active(),
+                       ),
+                       'url'      => array(
+                               'preview'       => esc_url_raw( $this->get_preview_url() ),
+                               'parent'        => esc_url_raw( admin_url() ),
+                               'activated'     => esc_url_raw( home_url( '/' ) ),
+                               'ajax'          => esc_url_raw( admin_url( 'admin-ajax.php', 'relative' ) ),
+                               'allowed'       => array_map( 'esc_url_raw', $allowed_urls ),
+                               'isCrossDomain' => $cross_domain,
+                               'home'          => esc_url_raw( home_url( '/' ) ),
+                               'login'         => esc_url_raw( $login_url ),
+                       ),
+                       'browser'  => array(
+                               'mobile' => wp_is_mobile(),
+                               'ios'    => $this->is_ios(),
+                       ),
+                       'panels'   => array(),
+                       'sections' => array(),
+                       'nonce'    => $this->get_nonces(),
+                       'autofocus' => $this->get_autofocus(),
+                       'documentTitleTmpl' => $this->get_document_title_template(),
+                       'previewableDevices' => $this->get_previewable_devices(),
+               );
+
+               // Prepare Customize Section objects to pass to JavaScript.
+               foreach ( $this->sections() as $id => $section ) {
+                       if ( $section->check_capabilities() ) {
+                               $settings['sections'][ $id ] = $section->json();
+                       }
+               }
+
+               // Prepare Customize Panel objects to pass to JavaScript.
+               foreach ( $this->panels() as $panel_id => $panel ) {
+                       if ( $panel->check_capabilities() ) {
+                               $settings['panels'][ $panel_id ] = $panel->json();
+                               foreach ( $panel->sections as $section_id => $section ) {
+                                       if ( $section->check_capabilities() ) {
+                                               $settings['sections'][ $section_id ] = $section->json();
+                                       }
+                               }
+                       }
+               }
+
+               ?>
+               <script type="text/javascript">
+                       var _wpCustomizeSettings = <?php echo wp_json_encode( $settings ); ?>;
+                       _wpCustomizeSettings.controls = {};
+                       _wpCustomizeSettings.settings = {};
+                       <?php
+
+                       // Serialize settings one by one to improve memory usage.
+                       echo "(function ( s ){\n";
+                       foreach ( $this->settings() as $setting ) {
+                               if ( $setting->check_capabilities() ) {
+                                       printf(
+                                               "s[%s] = %s;\n",
+                                               wp_json_encode( $setting->id ),
+                                               wp_json_encode( $setting->json() )
+                                       );
+                               }
+                       }
+                       echo "})( _wpCustomizeSettings.settings );\n";
+
+                       // Serialize controls one by one to improve memory usage.
+                       echo "(function ( c ){\n";
+                       foreach ( $this->controls() as $control ) {
+                               if ( $control->check_capabilities() ) {
+                                       printf(
+                                               "c[%s] = %s;\n",
+                                               wp_json_encode( $control->id ),
+                                               wp_json_encode( $control->json() )
+                                       );
+                               }
+                       }
+                       echo "})( _wpCustomizeSettings.controls );\n";
+               ?>
+               </script>
+               <?php
+       }
+
+       /**
+        * Returns a list of devices to allow previewing.
+        *
+        * @access public
+        * @since 4.5.0
+        *
+        * @return array List of devices with labels and default setting.
+        */
+       public function get_previewable_devices() {
+               $devices = array(
+                       'desktop' => array(
+                               'label' => __( 'Enter desktop preview mode' ),
+                               'default' => true,
+                       ),
+                       'tablet' => array(
+                               'label' => __( 'Enter tablet preview mode' ),
+                       ),
+                       'mobile' => array(
+                               'label' => __( 'Enter mobile preview mode' ),
+                       ),
+               );
+
+               /**
+                * Filters the available devices to allow previewing in the Customizer.
+                *
+                * @since 4.5.0
+                *
+                * @see WP_Customize_Manager::get_previewable_devices()
+                *
+                * @param array $devices List of devices with labels and default setting.
+                */
+               $devices = apply_filters( 'customize_previewable_devices', $devices );
+
+               return $devices;
+       }
+
        /**
         * Register some default controls.
         *
@@ -927,10 +1968,67 @@ final class WP_Customize_Manager {
         */
        public function register_controls() {
 
-               /* Site Title & Tagline */
+               /* Panel, Section, and Control Types */
+               $this->register_panel_type( 'WP_Customize_Panel' );
+               $this->register_section_type( 'WP_Customize_Section' );
+               $this->register_section_type( 'WP_Customize_Sidebar_Section' );
+               $this->register_control_type( 'WP_Customize_Color_Control' );
+               $this->register_control_type( 'WP_Customize_Media_Control' );
+               $this->register_control_type( 'WP_Customize_Upload_Control' );
+               $this->register_control_type( 'WP_Customize_Image_Control' );
+               $this->register_control_type( 'WP_Customize_Background_Image_Control' );
+               $this->register_control_type( 'WP_Customize_Cropped_Image_Control' );
+               $this->register_control_type( 'WP_Customize_Site_Icon_Control' );
+               $this->register_control_type( 'WP_Customize_Theme_Control' );
+
+               /* Themes */
+
+               $this->add_section( new WP_Customize_Themes_Section( $this, 'themes', array(
+                       'title'      => $this->theme()->display( 'Name' ),
+                       'capability' => 'switch_themes',
+                       'priority'   => 0,
+               ) ) );
+
+               // Themes Setting (unused - the theme is considerably more fundamental to the Customizer experience).
+               $this->add_setting( new WP_Customize_Filter_Setting( $this, 'active_theme', array(
+                       'capability' => 'switch_themes',
+               ) ) );
+
+               require_once( ABSPATH . 'wp-admin/includes/theme.php' );
+
+               // Theme Controls.
+
+               // Add a control for the active/original theme.
+               if ( ! $this->is_theme_active() ) {
+                       $themes = wp_prepare_themes_for_js( array( wp_get_theme( $this->original_stylesheet ) ) );
+                       $active_theme = current( $themes );
+                       $active_theme['isActiveTheme'] = true;
+                       $this->add_control( new WP_Customize_Theme_Control( $this, $active_theme['id'], array(
+                               'theme'    => $active_theme,
+                               'section'  => 'themes',
+                               'settings' => 'active_theme',
+                       ) ) );
+               }
+
+               $themes = wp_prepare_themes_for_js();
+               foreach ( $themes as $theme ) {
+                       if ( $theme['active'] || $theme['id'] === $this->original_stylesheet ) {
+                               continue;
+                       }
+
+                       $theme_id = 'theme_' . $theme['id'];
+                       $theme['isActiveTheme'] = false;
+                       $this->add_control( new WP_Customize_Theme_Control( $this, $theme_id, array(
+                               'theme'    => $theme,
+                               'section'  => 'themes',
+                               'settings' => 'active_theme',
+                       ) ) );
+               }
+
+               /* Site Identity */
 
                $this->add_section( 'title_tagline', array(
-                       'title'    => __( 'Site Title & Tagline' ),
+                       'title'    => __( 'Site Identity' ),
                        'priority' => 20,
                ) );
 
@@ -956,6 +2054,73 @@ final class WP_Customize_Manager {
                        'section'    => 'title_tagline',
                ) );
 
+               // Add a setting to hide header text if the theme doesn't support custom headers.
+               if ( ! current_theme_supports( 'custom-header', 'header-text' ) ) {
+                       $this->add_setting( 'header_text', array(
+                               'theme_supports'    => array( 'custom-logo', 'header-text' ),
+                               'default'           => 1,
+                               'sanitize_callback' => 'absint',
+                       ) );
+
+                       $this->add_control( 'header_text', array(
+                               'label'    => __( 'Display Site Title and Tagline' ),
+                               'section'  => 'title_tagline',
+                               'settings' => 'header_text',
+                               'type'     => 'checkbox',
+                       ) );
+               }
+
+               $this->add_setting( 'site_icon', array(
+                       'type'       => 'option',
+                       'capability' => 'manage_options',
+                       'transport'  => 'postMessage', // Previewed with JS in the Customizer controls window.
+               ) );
+
+               $this->add_control( new WP_Customize_Site_Icon_Control( $this, 'site_icon', array(
+                       'label'       => __( 'Site Icon' ),
+                       'description' => sprintf(
+                               /* translators: %s: site icon size in pixels */
+                               __( 'The Site Icon is used as a browser and app icon for your site. Icons must be square, and at least %s pixels wide and tall.' ),
+                               '<strong>512</strong>'
+                       ),
+                       'section'     => 'title_tagline',
+                       'priority'    => 60,
+                       'height'      => 512,
+                       'width'       => 512,
+               ) ) );
+
+               $this->add_setting( 'custom_logo', array(
+                       'theme_supports' => array( 'custom-logo' ),
+                       'transport'      => 'postMessage',
+               ) );
+
+               $custom_logo_args = get_theme_support( 'custom-logo' );
+               $this->add_control( new WP_Customize_Cropped_Image_Control( $this, 'custom_logo', array(
+                       'label'         => __( 'Logo' ),
+                       'section'       => 'title_tagline',
+                       'priority'      => 8,
+                       'height'        => $custom_logo_args[0]['height'],
+                       'width'         => $custom_logo_args[0]['width'],
+                       'flex_height'   => $custom_logo_args[0]['flex-height'],
+                       'flex_width'    => $custom_logo_args[0]['flex-width'],
+                       'button_labels' => array(
+                               'select'       => __( 'Select logo' ),
+                               'change'       => __( 'Change logo' ),
+                               'remove'       => __( 'Remove' ),
+                               'default'      => __( 'Default' ),
+                               'placeholder'  => __( 'No logo selected' ),
+                               'frame_title'  => __( 'Select logo' ),
+                               'frame_button' => __( 'Choose logo' ),
+                       ),
+               ) ) );
+
+               $this->selective_refresh->add_partial( 'custom_logo', array(
+                       'settings'            => array( 'custom_logo' ),
+                       'selector'            => '.custom-logo-link',
+                       'render_callback'     => array( $this, '_render_custom_logo_partial' ),
+                       'container_inclusive' => true,
+               ) );
+
                /* Colors */
 
                $this->add_section( 'colors', array(
@@ -975,9 +2140,10 @@ final class WP_Customize_Manager {
                // With custom value
                $this->add_control( 'display_header_text', array(
                        'settings' => 'header_textcolor',
-                       'label'    => __( 'Display Header Text' ),
+                       'label'    => __( 'Display Site Title and Tagline' ),
                        'section'  => 'title_tagline',
                        'type'     => 'checkbox',
+                       'priority' => 40,
                ) );
 
                $this->add_control( new WP_Customize_Color_Control( $this, 'header_textcolor', array(
@@ -1096,92 +2262,71 @@ final class WP_Customize_Manager {
                        }
                }
 
-               /* Nav Menus */
-
-               $locations      = get_registered_nav_menus();
-               $menus          = wp_get_nav_menus();
-               $num_locations  = count( array_keys( $locations ) );
-
-               $this->add_section( 'nav', array(
-                       'title'          => __( 'Navigation' ),
-                       'theme_supports' => 'menus',
-                       'priority'       => 100,
-                       'description'    => sprintf( _n('Your theme supports %s menu. Select which menu you would like to use.', 'Your theme supports %s menus. Select which menu appears in each location.', $num_locations ), number_format_i18n( $num_locations ) ) . "\n\n" . __('You can edit your menu content on the Menus screen in the Appearance section.'),
-               ) );
-
-               if ( $menus ) {
-                       $choices = array( 0 => __( '&mdash; Select &mdash;' ) );
-                       foreach ( $menus as $menu ) {
-                               $choices[ $menu->term_id ] = wp_html_excerpt( $menu->name, 40, '&hellip;' );
-                       }
-
-                       foreach ( $locations as $location => $description ) {
-                               $menu_setting_id = "nav_menu_locations[{$location}]";
-
-                               $this->add_setting( $menu_setting_id, array(
-                                       'sanitize_callback' => 'absint',
-                                       'theme_supports'    => 'menus',
-                               ) );
-
-                               $this->add_control( $menu_setting_id, array(
-                                       'label'   => $description,
-                                       'section' => 'nav',
-                                       'type'    => 'select',
-                                       'choices' => $choices,
-                               ) );
-                       }
-               }
-
                /* Static Front Page */
                // #WP19627
 
-               $this->add_section( 'static_front_page', array(
-                       'title'          => __( 'Static Front Page' ),
-               //      'theme_supports' => 'static-front-page',
-                       'priority'       => 120,
-                       'description'    => __( 'Your theme supports a static front page.' ),
-               ) );
-
-               $this->add_setting( 'show_on_front', array(
-                       'default'        => get_option( 'show_on_front' ),
-                       'capability'     => 'manage_options',
-                       'type'           => 'option',
-               //      'theme_supports' => 'static-front-page',
-               ) );
-
-               $this->add_control( 'show_on_front', array(
-                       'label'   => __( 'Front page displays' ),
-                       'section' => 'static_front_page',
-                       'type'    => 'radio',
-                       'choices' => array(
-                               'posts' => __( 'Your latest posts' ),
-                               'page'  => __( 'A static page' ),
-                       ),
-               ) );
-
-               $this->add_setting( 'page_on_front', array(
-                       'type'       => 'option',
-                       'capability' => 'manage_options',
-               //      'theme_supports' => 'static-front-page',
-               ) );
-
-               $this->add_control( 'page_on_front', array(
-                       'label'      => __( 'Front page' ),
-                       'section'    => 'static_front_page',
-                       'type'       => 'dropdown-pages',
-               ) );
-
-               $this->add_setting( 'page_for_posts', array(
-                       'type'           => 'option',
-                       'capability'     => 'manage_options',
-               //      'theme_supports' => 'static-front-page',
-               ) );
+               // Replicate behavior from options-reading.php and hide front page options if there are no pages
+               if ( get_pages() ) {
+                       $this->add_section( 'static_front_page', array(
+                               'title'          => __( 'Static Front Page' ),
+                       //      'theme_supports' => 'static-front-page',
+                               'priority'       => 120,
+                               'description'    => __( 'Your theme supports a static front page.' ),
+                       ) );
+
+                       $this->add_setting( 'show_on_front', array(
+                               'default'        => get_option( 'show_on_front' ),
+                               'capability'     => 'manage_options',
+                               'type'           => 'option',
+                       //      'theme_supports' => 'static-front-page',
+                       ) );
+
+                       $this->add_control( 'show_on_front', array(
+                               'label'   => __( 'Front page displays' ),
+                               'section' => 'static_front_page',
+                               'type'    => 'radio',
+                               'choices' => array(
+                                       'posts' => __( 'Your latest posts' ),
+                                       'page'  => __( 'A static page' ),
+                               ),
+                       ) );
+
+                       $this->add_setting( 'page_on_front', array(
+                               'type'       => 'option',
+                               'capability' => 'manage_options',
+                       //      'theme_supports' => 'static-front-page',
+                       ) );
+
+                       $this->add_control( 'page_on_front', array(
+                               'label'      => __( 'Front page' ),
+                               'section'    => 'static_front_page',
+                               'type'       => 'dropdown-pages',
+                       ) );
+
+                       $this->add_setting( 'page_for_posts', array(
+                               'type'           => 'option',
+                               'capability'     => 'manage_options',
+                       //      'theme_supports' => 'static-front-page',
+                       ) );
+
+                       $this->add_control( 'page_for_posts', array(
+                               'label'      => __( 'Posts page' ),
+                               'section'    => 'static_front_page',
+                               'type'       => 'dropdown-pages',
+                       ) );
+               }
+       }
 
-               $this->add_control( 'page_for_posts', array(
-                       'label'      => __( 'Posts page' ),
-                       'section'    => 'static_front_page',
-                       'type'       => 'dropdown-pages',
-               ) );
+       /**
+        * Add settings from the POST data that were not added with code, e.g. dynamically-created settings for Widgets
+        *
+        * @since 4.2.0
+        * @access public
+        *
+        * @see add_dynamic_settings()
+        */
+       public function register_dynamic_settings() {
+               $this->add_dynamic_settings( array_keys( $this->unsanitized_post_values() ) );
        }
 
        /**
@@ -1193,7 +2338,7 @@ final class WP_Customize_Manager {
         * @since 3.4.0
         *
         * @param string $color
-        * @return string
+        * @return mixed
         */
        public function _sanitize_header_textcolor( $color ) {
                if ( 'blank' === $color )
@@ -1205,68 +2350,24 @@ final class WP_Customize_Manager {
 
                return $color;
        }
-}
-
-/**
- * Sanitizes a hex color.
- *
- * Returns either '', a 3 or 6 digit hex color (with #), or null.
- * For sanitizing values without a #, see sanitize_hex_color_no_hash().
- *
- * @since 3.4.0
- *
- * @param string $color
- * @return string|null
- */
-function sanitize_hex_color( $color ) {
-       if ( '' === $color )
-               return '';
-
-       // 3 or 6 hex digits, or the empty string.
-       if ( preg_match('|^#([A-Fa-f0-9]{3}){1,2}$|', $color ) )
-               return $color;
 
-       return null;
-}
-
-/**
- * Sanitizes a hex color without a hash. Use sanitize_hex_color() when possible.
- *
- * Saving hex colors without a hash puts the burden of adding the hash on the
- * UI, which makes it difficult to use or upgrade to other color types such as
- * rgba, hsl, rgb, and html color names.
- *
- * Returns either '', a 3 or 6 digit hex color (without a #), or null.
- *
- * @since 3.4.0
- * @uses sanitize_hex_color()
- *
- * @param string $color
- * @return string|null
- */
-function sanitize_hex_color_no_hash( $color ) {
-       $color = ltrim( $color, '#' );
-
-       if ( '' === $color )
-               return '';
-
-       return sanitize_hex_color( '#' . $color ) ? $color : null;
-}
-
-/**
- * Ensures that any hex color is properly hashed.
- * Otherwise, returns value untouched.
- *
- * This method should only be necessary if using sanitize_hex_color_no_hash().
- *
- * @since 3.4.0
- *
- * @param string $color
- * @return string
- */
-function maybe_hash_hex_color( $color ) {
-       if ( $unhashed = sanitize_hex_color_no_hash( $color ) )
-               return '#' . $unhashed;
-
-       return $color;
+       /**
+        * Callback for rendering the custom logo, used in the custom_logo partial.
+        *
+        * This method exists because the partial object and context data are passed
+        * into a partial's render_callback so we cannot use get_custom_logo() as
+        * the render_callback directly since it expects a blog ID as the first
+        * argument. When WP no longer supports PHP 5.3, this method can be removed
+        * in favor of an anonymous function.
+        *
+        * @see WP_Customize_Manager::register_controls()
+        *
+        * @since 4.5.0
+        * @access private
+        *
+        * @return string Custom logo.
+        */
+       public function _render_custom_logo_partial() {
+               return get_custom_logo();
+       }
 }