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wp-admin/js/customize-controls.js

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/**
 * @output wp-admin/js/customize-controls.js
 */

/* global _wpCustomizeHeader, _wpCustomizeBackground, _wpMediaViewsL10n, MediaElementPlayer, console, confirm */
(function( exports, $ ){
    var Container, focus, normalizedTransitionendEventName, api = wp.customize;

    var reducedMotionMediaQuery = window.matchMedia( '(prefers-reduced-motion: reduce)' );
    var isReducedMotion = reducedMotionMediaQuery.matches;
    reducedMotionMediaQuery.addEventListener( 'change' , function handleReducedMotionChange( event ) {
        isReducedMotion = event.matches;
    });

    api.OverlayNotification = api.Notification.extend(/** @lends wp.customize.OverlayNotification.prototype */{

        /**
         * Whether the notification should show a loading spinner.
         *
         * @since 4.9.0
         * @var {boolean}
         */
        loading: false,

        /**
         * A notification that is displayed in a full-screen overlay.
         *
         * @constructs wp.customize.OverlayNotification
         * @augments   wp.customize.Notification
         *
         * @since 4.9.0
         *
         * @param {string} code - Code.
         * @param {Object} params - Params.
         */
        initialize: function( code, params ) {
            var notification = this;
            api.Notification.prototype.initialize.call( notification, code, params );
            notification.containerClasses += ' notification-overlay';
            if ( notification.loading ) {
                notification.containerClasses += ' notification-loading';
            }
        },

        /**
         * Render notification.
         *
         * @since 4.9.0
         *
         * @return {jQuery} Notification container.
         */
        render: function() {
            var li = api.Notification.prototype.render.call( this );
            li.on( 'keydown', _.bind( this.handleEscape, this ) );
            return li;
        },

        /**
         * Stop propagation on escape key presses, but also dismiss notification if it is dismissible.
         *
         * @since 4.9.0
         *
         * @param {jQuery.Event} event - Event.
         * @return {void}
         */
        handleEscape: function( event ) {
            var notification = this;
            if ( 27 === event.which ) {
                event.stopPropagation();
                if ( notification.dismissible && notification.parent ) {
                    notification.parent.remove( notification.code );
                }
            }
        }
    });

    api.Notifications = api.Values.extend(/** @lends wp.customize.Notifications.prototype */{

        /**
         * Whether the alternative style should be used.
         *
         * @since 4.9.0
         * @type {boolean}
         */
        alt: false,

        /**
         * The default constructor for items of the collection.
         *
         * @since 4.9.0
         * @type {object}
         */
        defaultConstructor: api.Notification,

        /**
         * A collection of observable notifications.
         *
         * @since 4.9.0
         *
         * @constructs wp.customize.Notifications
         * @augments   wp.customize.Values
         *
         * @param {Object}  options - Options.
         * @param {jQuery}  [options.container] - Container element for notifications. This can be injected later.
         * @param {boolean} [options.alt] - Whether alternative style should be used when rendering notifications.
         *
         * @return {void}
         */
        initialize: function( options ) {
            var collection = this;

            api.Values.prototype.initialize.call( collection, options );

            _.bindAll( collection, 'constrainFocus' );

            // Keep track of the order in which the notifications were added for sorting purposes.
            collection._addedIncrement = 0;
            collection._addedOrder = {};

            // Trigger change event when notification is added or removed.
            collection.bind( 'add', function( notification ) {
                collection.trigger( 'change', notification );
            });
            collection.bind( 'removed', function( notification ) {
                collection.trigger( 'change', notification );
            });
        },

        /**
         * Get the number of notifications added.
         *
         * @since 4.9.0
         * @return {number} Count of notifications.
         */
        count: function() {
            return _.size( this._value );
        },

        /**
         * Add notification to the collection.
         *
         * @since 4.9.0
         *
         * @param {string|wp.customize.Notification} notification - Notification object to add. Alternatively code may be supplied, and in that case the second notificationObject argument must be supplied.
         * @param {wp.customize.Notification} [notificationObject] - Notification to add when first argument is the code string.
         * @return {wp.customize.Notification} Added notification (or existing instance if it was already added).
         */
        add: function( notification, notificationObject ) {
            var collection = this, code, instance;
            if ( 'string' === typeof notification ) {
                code = notification;
                instance = notificationObject;
            } else {
                code = notification.code;
                instance = notification;
            }
            if ( ! collection.has( code ) ) {
                collection._addedIncrement += 1;
                collection._addedOrder[ code ] = collection._addedIncrement;
            }
            return api.Values.prototype.add.call( collection, code, instance );
        },

        /**
         * Add notification to the collection.
         *
         * @since 4.9.0
         * @param {string} code - Notification code to remove.
         * @return {api.Notification} Added instance (or existing instance if it was already added).
         */
        remove: function( code ) {
            var collection = this;
            delete collection._addedOrder[ code ];
            return api.Values.prototype.remove.call( this, code );
        },

        /**
         * Get list of notifications.
         *
         * Notifications may be sorted by type followed by added time.
         *
         * @since 4.9.0
         * @param {Object}  args - Args.
         * @param {boolean} [args.sort=false] - Whether to return the notifications sorted.
         * @return {Array.<wp.customize.Notification>} Notifications.
         */
        get: function( args ) {
            var collection = this, notifications, errorTypePriorities, params;
            notifications = _.values( collection._value );

            params = _.extend(
                { sort: false },
                args
            );

            if ( params.sort ) {
                errorTypePriorities = { error: 4, warning: 3, success: 2, info: 1 };
                notifications.sort( function( a, b ) {
                    var aPriority = 0, bPriority = 0;
                    if ( ! _.isUndefined( errorTypePriorities[ a.type ] ) ) {
                        aPriority = errorTypePriorities[ a.type ];
                    }
                    if ( ! _.isUndefined( errorTypePriorities[ b.type ] ) ) {
                        bPriority = errorTypePriorities[ b.type ];
                    }
                    if ( aPriority !== bPriority ) {
                        return bPriority - aPriority; // Show errors first.
                    }
                    return collection._addedOrder[ b.code ] - collection._addedOrder[ a.code ]; // Show newer notifications higher.
                });
            }

            return notifications;
        },

        /**
         * Render notifications area.
         *
         * @since 4.9.0
         * @return {void}
         */
        render: function() {
            var collection = this,
                notifications, hadOverlayNotification = false, hasOverlayNotification, overlayNotifications = [],
                previousNotificationsByCode = {},
                listElement, focusableElements;

            // Short-circuit if there are no container to render into.
            if ( ! collection.container || ! collection.container.length ) {
                return;
            }

            notifications = collection.get( { sort: true } );
            collection.container.toggle( 0 !== notifications.length );

            // Short-circuit if there are no changes to the notifications.
            if ( collection.container.is( collection.previousContainer ) && _.isEqual( notifications, collection.previousNotifications ) ) {
                return;
            }

            // Make sure list is part of the container.
            listElement = collection.container.children( 'ul' ).first();
            if ( ! listElement.length ) {
                listElement = $( '<ul></ul>' );
                collection.container.append( listElement );
            }

            // Remove all notifications prior to re-rendering.
            listElement.find( '> [data-code]' ).remove();

            _.each( collection.previousNotifications, function( notification ) {
                previousNotificationsByCode[ notification.code ] = notification;
            });

            // Add all notifications in the sorted order.
            _.each( notifications, function( notification ) {
                var notificationContainer;
                if ( wp.a11y && ( ! previousNotificationsByCode[ notification.code ] || ! _.isEqual( notification.message, previousNotificationsByCode[ notification.code ].message ) ) ) {
                    wp.a11y.speak( notification.message, 'assertive' );
                }
                notificationContainer = $( notification.render() );
                notification.container = notificationContainer;
                listElement.append( notificationContainer ); // @todo Consider slideDown() as enhancement.

                if ( notification.extended( api.OverlayNotification ) ) {
                    overlayNotifications.push( notification );
                }
            });
            hasOverlayNotification = Boolean( overlayNotifications.length );

            if ( collection.previousNotifications ) {
                hadOverlayNotification = Boolean( _.find( collection.previousNotifications, function( notification ) {
                    return notification.extended( api.OverlayNotification );
                } ) );
            }

            if ( hasOverlayNotification !== hadOverlayNotification ) {
                $( document.body ).toggleClass( 'customize-loading', hasOverlayNotification );
                collection.container.toggleClass( 'has-overlay-notifications', hasOverlayNotification );
                if ( hasOverlayNotification ) {
                    collection.previousActiveElement = document.activeElement;
                    $( document ).on( 'keydown', collection.constrainFocus );
                } else {
                    $( document ).off( 'keydown', collection.constrainFocus );
                }
            }

            if ( hasOverlayNotification ) {
                collection.focusContainer = overlayNotifications[ overlayNotifications.length - 1 ].container;
                collection.focusContainer.prop( 'tabIndex', -1 );
                focusableElements = collection.focusContainer.find( ':focusable' );
                if ( focusableElements.length ) {
                    focusableElements.first().focus();
                } else {
                    collection.focusContainer.focus();
                }
            } else if ( collection.previousActiveElement ) {
                $( collection.previousActiveElement ).trigger( 'focus' );
                collection.previousActiveElement = null;
            }

            collection.previousNotifications = notifications;
            collection.previousContainer = collection.container;
            collection.trigger( 'rendered' );
        },

        /**
         * Constrain focus on focus container.
         *
         * @since 4.9.0
         *
         * @param {jQuery.Event} event - Event.
         * @return {void}
         */
        constrainFocus: function constrainFocus( event ) {
            var collection = this, focusableElements;

            // Prevent keys from escaping.
            event.stopPropagation();

            if ( 9 !== event.which ) { // Tab key.
                return;
            }

            focusableElements = collection.focusContainer.find( ':focusable' );
            if ( 0 === focusableElements.length ) {
                focusableElements = collection.focusContainer;
            }

            if ( ! $.contains( collection.focusContainer[0], event.target ) || ! $.contains( collection.focusContainer[0], document.activeElement ) ) {
                event.preventDefault();
                focusableElements.first().focus();
            } else if ( focusableElements.last().is( event.target ) && ! event.shiftKey ) {
                event.preventDefault();
                focusableElements.first().focus();
            } else if ( focusableElements.first().is( event.target ) && event.shiftKey ) {
                event.preventDefault();
                focusableElements.last().focus();
            }
        }
    });

    api.Setting = api.Value.extend(/** @lends wp.customize.Setting.prototype */{

        /**
         * Default params.
         *
         * @since 4.9.0
         * @var {object}
         */
        defaults: {
            transport: 'refresh',
            dirty: false
        },

        /**
         * A Customizer Setting.
         *
         * A setting is WordPress data (theme mod, option, menu, etc.) that the user can
         * draft changes to in the Customizer.
         *
         * @see PHP class WP_Customize_Setting.
         *
         * @constructs wp.customize.Setting
         * @augments   wp.customize.Value
         *
         * @since 3.4.0
         *
         * @param {string}  id                          - The setting ID.
         * @param {*}       value                       - The initial value of the setting.
         * @param {Object}  [options={}]                - Options.
         * @param {string}  [options.transport=refresh] - The transport to use for previewing. Supports 'refresh' and 'postMessage'.
         * @param {boolean} [options.dirty=false]       - Whether the setting should be considered initially dirty.
         * @param {Object}  [options.previewer]         - The Previewer instance to sync with. Defaults to wp.customize.previewer.
         */
        initialize: function( id, value, options ) {
            var setting = this, params;
            params = _.extend(
                { previewer: api.previewer },
                setting.defaults,
                options || {}
            );

            api.Value.prototype.initialize.call( setting, value, params );

            setting.id = id;
            setting._dirty = params.dirty; // The _dirty property is what the Customizer reads from.
            setting.notifications = new api.Notifications();

            // Whenever the setting's value changes, refresh the preview.
            setting.bind( setting.preview );
        },

        /**
         * Refresh the preview, respective of the setting's refresh policy.
         *
         * If the preview hasn't sent a keep-alive message and is likely
         * disconnected by having navigated to a non-allowed URL, then the
         * refresh transport will be forced when postMessage is the transport.
         * Note that postMessage does not throw an error when the recipient window
         * fails to match the origin window, so using try/catch around the
         * previewer.send() call to then fallback to refresh will not work.
         *
         * @since 3.4.0
         * @access public
         *
         * @return {void}
         */
        preview: function() {
            var setting = this, transport;
            transport = setting.transport;

            if ( 'postMessage' === transport && ! api.state( 'previewerAlive' ).get() ) {
                transport = 'refresh';
            }

            if ( 'postMessage' === transport ) {
                setting.previewer.send( 'setting', [ setting.id, setting() ] );
            } else if ( 'refresh' === transport ) {
                setting.previewer.refresh();
            }
        },

        /**
         * Find controls associated with this setting.
         *
         * @since 4.6.0
         * @return {wp.customize.Control[]} Controls associated with setting.
         */
        findControls: function() {
            var setting = this, controls = [];
            api.control.each( function( control ) {
                _.each( control.settings, function( controlSetting ) {
                    if ( controlSetting.id === setting.id ) {
                        controls.push( control );
                    }
                } );
            } );
            return controls;
        }
    });

    /**
     * Current change count.
     *
     * @alias wp.customize._latestRevision
     *
     * @since 4.7.0
     * @type {number}
     * @protected
     */
    api._latestRevision = 0;

    /**
     * Last revision that was saved.
     *
     * @alias wp.customize._lastSavedRevision
     *
     * @since 4.7.0
     * @type {number}
     * @protected
     */
    api._lastSavedRevision = 0;

    /**
     * Latest revisions associated with the updated setting.
     *
     * @alias wp.customize._latestSettingRevisions
     *
     * @since 4.7.0
     * @type {object}
     * @protected
     */
    api._latestSettingRevisions = {};

    /*
     * Keep track of the revision associated with each updated setting so that
     * requestChangesetUpdate knows which dirty settings to include. Also, once
     * ready is triggered and all initial settings have been added, increment
     * revision for each newly-created initially-dirty setting so that it will
     * also be included in changeset update requests.
     */
    api.bind( 'change', function incrementChangedSettingRevision( setting ) {
        api._latestRevision += 1;
        api._latestSettingRevisions[ setting.id ] = api._latestRevision;
    } );
    api.bind( 'ready', function() {
        api.bind( 'add', function incrementCreatedSettingRevision( setting ) {
            if ( setting._dirty ) {
                api._latestRevision += 1;
                api._latestSettingRevisions[ setting.id ] = api._latestRevision;
            }
        } );
    } );

    /**
     * Get the dirty setting values.
     *
     * @alias wp.customize.dirtyValues
     *
     * @since 4.7.0
     * @access public
     *
     * @param {Object} [options] Options.
     * @param {boolean} [options.unsaved=false] Whether only values not saved yet into a changeset will be returned (differential changes).
     * @return {Object} Dirty setting values.
     */
    api.dirtyValues = function dirtyValues( options ) {
        var values = {};
        api.each( function( setting ) {
            var settingRevision;

            if ( ! setting._dirty ) {
                return;
            }

            settingRevision = api._latestSettingRevisions[ setting.id ];

            // Skip including settings that have already been included in the changeset, if only requesting unsaved.
            if ( api.state( 'changesetStatus' ).get() && ( options && options.unsaved ) && ( _.isUndefined( settingRevision ) || settingRevision <= api._lastSavedRevision ) ) {
                return;
            }

            values[ setting.id ] = setting.get();
        } );
        return values;
    };

    /**
     * Request updates to the changeset.
     *
     * @alias wp.customize.requestChangesetUpdate
     *
     * @since 4.7.0
     * @access public
     *
     * @param {Object}  [changes] - Mapping of setting IDs to setting params each normally including a value property, or mapping to null.
     *                             If not provided, then the changes will still be obtained from unsaved dirty settings.
     * @param {Object}  [args] - Additional options for the save request.
     * @param {boolean} [args.autosave=false] - Whether changes will be stored in autosave revision if the changeset has been promoted from an auto-draft.
     * @param {boolean} [args.force=false] - Send request to update even when there are no changes to submit. This can be used to request the latest status of the changeset on the server.
     * @param {string}  [args.title] - Title to update in the changeset. Optional.
     * @param {string}  [args.date] - Date to update in the changeset. Optional.
     * @return {jQuery.Promise} Promise resolving with the response data.
     */
    api.requestChangesetUpdate = function requestChangesetUpdate( changes, args ) {
        var deferred, request, submittedChanges = {}, data, submittedArgs;
        deferred = new $.Deferred();

        // Prevent attempting changeset update while request is being made.
        if ( 0 !== api.state( 'processing' ).get() ) {
            deferred.reject( 'already_processing' );
            return deferred.promise();
        }

        submittedArgs = _.extend( {
            title: null,
            date: null,
            autosave: false,
            force: false
        }, args );

        if ( changes ) {
            _.extend( submittedChanges, changes );
        }

        // Ensure all revised settings (changes pending save) are also included, but not if marked for deletion in changes.
        _.each( api.dirtyValues( { unsaved: true } ), function( dirtyValue, settingId ) {
            if ( ! changes || null !== changes[ settingId ] ) {
                submittedChanges[ settingId ] = _.extend(
                    {},
                    submittedChanges[ settingId ] || {},
                    { value: dirtyValue }
                );
            }
        } );

        // Allow plugins to attach additional params to the settings.
        api.trigger( 'changeset-save', submittedChanges, submittedArgs );

        // Short-circuit when there are no pending changes.
        if ( ! submittedArgs.force && _.isEmpty( submittedChanges ) && null === submittedArgs.title && null === submittedArgs.date ) {
            deferred.resolve( {} );
            return deferred.promise();
        }

        // A status would cause a revision to be made, and for this wp.customize.previewer.save() should be used.
        // Status is also disallowed for revisions regardless.
        if ( submittedArgs.status ) {
            return deferred.reject( { code: 'illegal_status_in_changeset_update' } ).promise();
        }

        // Dates not beung allowed for revisions are is a technical limitation of post revisions.
        if ( submittedArgs.date && submittedArgs.autosave ) {
            return deferred.reject( { code: 'illegal_autosave_with_date_gmt' } ).promise();
        }

        // Make sure that publishing a changeset waits for all changeset update requests to complete.
        api.state( 'processing' ).set( api.state( 'processing' ).get() + 1 );
        deferred.always( function() {
            api.state( 'processing' ).set( api.state( 'processing' ).get() - 1 );
        } );

        // Ensure that if any plugins add data to save requests by extending query() that they get included here.
        data = api.previewer.query( { excludeCustomizedSaved: true } );
        delete data.customized; // Being sent in customize_changeset_data instead.
        _.extend( data, {
            nonce: api.settings.nonce.save,
            customize_theme: api.settings.theme.stylesheet,
            customize_changeset_data: JSON.stringify( submittedChanges )
        } );
        if ( null !== submittedArgs.title ) {
            data.customize_changeset_title = submittedArgs.title;
        }
        if ( null !== submittedArgs.date ) {
            data.customize_changeset_date = submittedArgs.date;
        }
        if ( false !== submittedArgs.autosave ) {
            data.customize_changeset_autosave = 'true';
        }

        // Allow plugins to modify the params included with the save request.
        api.trigger( 'save-request-params', data );

        request = wp.ajax.post( 'customize_save', data );

        request.done( function requestChangesetUpdateDone( data ) {
            var savedChangesetValues = {};

            // Ensure that all settings updated subsequently will be included in the next changeset update request.
            api._lastSavedRevision = Math.max( api._latestRevision, api._lastSavedRevision );

            api.state( 'changesetStatus' ).set( data.changeset_status );

            if ( data.changeset_date ) {
                api.state( 'changesetDate' ).set( data.changeset_date );
            }

            deferred.resolve( data );
            api.trigger( 'changeset-saved', data );

            if ( data.setting_validities ) {
                _.each( data.setting_validities, function( validity, settingId ) {
                    if ( true === validity && _.isObject( submittedChanges[ settingId ] ) && ! _.isUndefined( submittedChanges[ settingId ].value ) ) {
                        savedChangesetValues[ settingId ] = submittedChanges[ settingId ].value;
                    }
                } );
            }

            api.previewer.send( 'changeset-saved', _.extend( {}, data, { saved_changeset_values: savedChangesetValues } ) );
        } );
        request.fail( function requestChangesetUpdateFail( data ) {
            deferred.reject( data );
            api.trigger( 'changeset-error', data );
        } );
        request.always( function( data ) {
            if ( data.setting_validities ) {
                api._handleSettingValidities( {
                    settingValidities: data.setting_validities
                } );
            }
        } );

        return deferred.promise();
    };

    /**
     * Watch all changes to Value properties, and bubble changes to parent Values instance
     *
     * @alias wp.customize.utils.bubbleChildValueChanges
     *
     * @since 4.1.0
     *
     * @param {wp.customize.Class} instance
     * @param {Array}              properties  The names of the Value instances to watch.
     */
    api.utils.bubbleChildValueChanges = function ( instance, properties ) {
        $.each( properties, function ( i, key ) {
            instance[ key ].bind( function ( to, from ) {
                if ( instance.parent && to !== from ) {
                    instance.parent.trigger( 'change', instance );
                }
            } );
        } );
    };

    /**
     * Expand a panel, section, or control and focus on the first focusable element.
     *
     * @alias wp.customize~focus
     *
     * @since 4.1.0
     *
     * @param {Object}   [params]
     * @param {Function} [params.completeCallback]
     */
    focus = function ( params ) {
        var construct, completeCallback, focus, focusElement, sections;
        construct = this;
        params = params || {};
        focus = function () {
            // If a child section is currently expanded, collapse it.
            if ( construct.extended( api.Panel ) ) {
                sections = construct.sections();
                if ( 1 < sections.length ) {
                    sections.forEach( function ( section ) {
                        if ( section.expanded() ) {
                            section.collapse();
                        }
                    } );
                }
            }

            var focusContainer;
            if ( ( construct.extended( api.Panel ) || construct.extended( api.Section ) ) && construct.expanded && construct.expanded() ) {
                focusContainer = construct.contentContainer;
            } else {
                focusContainer = construct.container;
            }

            focusElement = focusContainer.find( '.control-focus:first' );
            if ( 0 === focusElement.length ) {
                // Note that we can't use :focusable due to a jQuery UI issue. See: https://github.com/jquery/jquery-ui/pull/1583
                focusElement = focusContainer.find( 'input, select, textarea, button, object, a[href], [tabindex]' ).filter( ':visible' ).first();
            }
            focusElement.focus();
        };
        if ( params.completeCallback ) {
            completeCallback = params.completeCallback;
            params.completeCallback = function () {
                focus();
                completeCallback();
            };
        } else {
            params.completeCallback = focus;
        }

        api.state( 'paneVisible' ).set( true );
        if ( construct.expand ) {
            construct.expand( params );
        } else {
            params.completeCallback();
        }
    };

    /**
     * Stable sort for Panels, Sections, and Controls.
     *
     * If a.priority() === b.priority(), then sort by their respective params.instanceNumber.
     *
     * @alias wp.customize.utils.prioritySort
     *
     * @since 4.1.0
     *
     * @param {(wp.customize.Panel|wp.customize.Section|wp.customize.Control)} a
     * @param {(wp.customize.Panel|wp.customize.Section|wp.customize.Control)} b
     * @return {number}
     */
    api.utils.prioritySort = function ( a, b ) {
        if ( a.priority() === b.priority() && typeof a.params.instanceNumber === 'number' && typeof b.params.instanceNumber === 'number' ) {
            return a.params.instanceNumber - b.params.instanceNumber;
        } else {
            return a.priority() - b.priority();
        }
    };

    /**
     * Return whether the supplied Event object is for a keydown event but not the Enter key.
     *
     * @alias wp.customize.utils.isKeydownButNotEnterEvent
     *
     * @since 4.1.0
     *
     * @param {jQuery.Event} event
     * @return {boolean}
     */
    api.utils.isKeydownButNotEnterEvent = function ( event ) {
        return ( 'keydown' === event.type && 13 !== event.which );
    };

    /**
     * Return whether the two lists of elements are the same and are in the same order.
     *
     * @alias wp.customize.utils.areElementListsEqual
     *
     * @since 4.1.0
     *
     * @param {Array|jQuery} listA
     * @param {Array|jQuery} listB
     * @return {boolean}
     */
    api.utils.areElementListsEqual = function ( listA, listB ) {
        var equal = (
            listA.length === listB.length && // If lists are different lengths, then naturally they are not equal.
            -1 === _.indexOf( _.map(         // Are there any false values in the list returned by map?
                _.zip( listA, listB ),       // Pair up each element between the two lists.
                function ( pair ) {
                    return $( pair[0] ).is( pair[1] ); // Compare to see if each pair is equal.
                }
            ), false ) // Check for presence of false in map's return value.
        );
        return equal;
    };

    /**
     * Highlight the existence of a button.
     *
     * This function reminds the user of a button represented by the specified
     * UI element, after an optional delay. If the user focuses the element
     * before the delay passes, the reminder is canceled.
     *
     * @alias wp.customize.utils.highlightButton
     *
     * @since 4.9.0
     *
     * @param {jQuery} button - The element to highlight.
     * @param {Object} [options] - Options.
     * @param {number} [options.delay=0] - Delay in milliseconds.
     * @param {jQuery} [options.focusTarget] - A target for user focus that defaults to the highlighted element.
     *                                         If the user focuses the target before the delay passes, the reminder
     *                                         is canceled. This option exists to accommodate compound buttons
     *                                         containing auxiliary UI, such as the Publish button augmented with a
     *                                         Settings button.
     * @return {Function} An idempotent function that cancels the reminder.
     */
    api.utils.highlightButton = function highlightButton( button, options ) {
        var animationClass = 'button-see-me',
            canceled = false,
            params;

        params = _.extend(
            {
                delay: 0,
                focusTarget: button
            },
            options
        );

        function cancelReminder() {
            canceled = true;
        }

        params.focusTarget.on( 'focusin', cancelReminder );
        setTimeout( function() {
            params.focusTarget.off( 'focusin', cancelReminder );

            if ( ! canceled ) {
                button.addClass( animationClass );
                button.one( 'animationend', function() {
                    /*
                     * Remove animation class to avoid situations in Customizer where
                     * DOM nodes are moved (re-inserted) and the animation repeats.
                     */
                    button.removeClass( animationClass );
                } );
            }
        }, params.delay );

        return cancelReminder;
    };

    /**
     * Get current timestamp adjusted for server clock time.
     *
     * Same functionality as the `current_time( 'mysql', false )` function in PHP.
     *
     * @alias wp.customize.utils.getCurrentTimestamp
     *
     * @since 4.9.0
     *
     * @return {number} Current timestamp.
     */
    api.utils.getCurrentTimestamp = function getCurrentTimestamp() {
        var currentDate, currentClientTimestamp, timestampDifferential;
        currentClientTimestamp = _.now();
        currentDate = new Date( api.settings.initialServerDate.replace( /-/g, '/' ) );
        timestampDifferential = currentClientTimestamp - api.settings.initialClientTimestamp;
        timestampDifferential += api.settings.initialClientTimestamp - api.settings.initialServerTimestamp;
        currentDate.setTime( currentDate.getTime() + timestampDifferential );
        return currentDate.getTime();
    };

    /**
     * Get remaining time of when the date is set.
     *
     * @alias wp.customize.utils.getRemainingTime
     *
     * @since 4.9.0
     *
     * @param {string|number|Date} datetime - Date time or timestamp of the future date.
     * @return {number} remainingTime - Remaining time in milliseconds.
     */
    api.utils.getRemainingTime = function getRemainingTime( datetime ) {
        var millisecondsDivider = 1000, remainingTime, timestamp;
        if ( datetime instanceof Date ) {
            timestamp = datetime.getTime();
        } else if ( 'string' === typeof datetime ) {
            timestamp = ( new Date( datetime.replace( /-/g, '/' ) ) ).getTime();
        } else {
            timestamp = datetime;
        }

        remainingTime = timestamp - api.utils.getCurrentTimestamp();
        remainingTime = Math.ceil( remainingTime / millisecondsDivider );
        return remainingTime;
    };

    /**
     * Return browser supported `transitionend` event name.
     *
     * @since 4.7.0
     *
     * @ignore
     *
     * @return {string|null} Normalized `transitionend` event name or null if CSS transitions are not supported.
     */
    normalizedTransitionendEventName = (function () {
        var el, transitions, prop;
        el = document.createElement( 'div' );
        transitions = {
            'transition'      : 'transitionend',
            'OTransition'     : 'oTransitionEnd',
            'MozTransition'   : 'transitionend',
            'WebkitTransition': 'webkitTransitionEnd'
        };
        prop = _.find( _.keys( transitions ), function( prop ) {
            return ! _.isUndefined( el.style[ prop ] );
        } );
        if ( prop ) {
            return transitions[ prop ];
        } else {
            return null;
        }
    })();

    Container = api.Class.extend(/** @lends wp.customize~Container.prototype */{
        defaultActiveArguments: { duration: 'fast', completeCallback: $.noop },
        defaultExpandedArguments: { duration: 'fast', completeCallback: $.noop },
        containerType: 'container',
        defaults: {
            title: '',
            description: '',
            priority: 100,
            type: 'default',
            content: null,
            active: true,
            instanceNumber: null
        },

        /**
         * Base class for Panel and Section.
         *
         * @constructs wp.customize~Container
         * @augments   wp.customize.Class
         *
         * @since 4.1.0
         *
         * @borrows wp.customize~focus as focus
         *
         * @param {string}  id - The ID for the container.
         * @param {Object}  options - Object containing one property: params.
         * @param {string}  options.title - Title shown when panel is collapsed and expanded.
         * @param {string}  [options.description] - Description shown at the top of the panel.
         * @param {number}  [options.priority=100] - The sort priority for the panel.
         * @param {string}  [options.templateId] - Template selector for container.
         * @param {string}  [options.type=default] - The type of the panel. See wp.customize.panelConstructor.
         * @param {string}  [options.content] - The markup to be used for the panel container. If empty, a JS template is used.
         * @param {boolean} [options.active=true] - Whether the panel is active or not.
         * @param {Object}  [options.params] - Deprecated wrapper for the above properties.
         */
        initialize: function ( id, options ) {
            var container = this;
            container.id = id;

            if ( ! Container.instanceCounter ) {
                Container.instanceCounter = 0;
            }
            Container.instanceCounter++;

            $.extend( container, {
                params: _.defaults(
                    options.params || options, // Passing the params is deprecated.
                    container.defaults
                )
            } );
            if ( ! container.params.instanceNumber ) {
                container.params.instanceNumber = Container.instanceCounter;
            }
            container.notifications = new api.Notifications();
            container.templateSelector = container.params.templateId || 'customize-' + container.containerType + '-' + container.params.type;
            container.container = $( container.params.content );
            if ( 0 === container.container.length ) {
                container.container = $( container.getContainer() );
            }
            container.headContainer = container.container;
            container.contentContainer = container.getContent();
            container.container = container.container.add( container.contentContainer );

            container.deferred = {
                embedded: new $.Deferred()
            };
            container.priority = new api.Value();
            container.active = new api.Value();
            container.activeArgumentsQueue = [];
            container.expanded = new api.Value();
            container.expandedArgumentsQueue = [];

            container.active.bind( function ( active ) {
                var args = container.activeArgumentsQueue.shift();
                args = $.extend( {}, container.defaultActiveArguments, args );
                active = ( active && container.isContextuallyActive() );
                container.onChangeActive( active, args );
            });
            container.expanded.bind( function ( expanded ) {
                var args = container.expandedArgumentsQueue.shift();
                args = $.extend( {}, container.defaultExpandedArguments, args );
                container.onChangeExpanded( expanded, args );
            });

            container.deferred.embedded.done( function () {
                container.setupNotifications();
                container.attachEvents();
            });

            api.utils.bubbleChildValueChanges( container, [ 'priority', 'active' ] );

            container.priority.set( container.params.priority );
            container.active.set( container.params.active );
            container.expanded.set( false );
        },

        /**
         * Get the element that will contain the notifications.
         *
         * @since 4.9.0
         * @return {jQuery} Notification container element.
         */
        getNotificationsContainerElement: function() {
            var container = this;
            return container.contentContainer.find( '.customize-control-notifications-container:first' );
        },

        /**
         * Set up notifications.
         *
         * @since 4.9.0
         * @return {void}
         */
        setupNotifications: function() {
            var container = this, renderNotifications;
            container.notifications.container = container.getNotificationsContainerElement();

            // Render notifications when they change and when the construct is expanded.
            renderNotifications = function() {
                if ( container.expanded.get() ) {
                    container.notifications.render();
                }
            };
            container.expanded.bind( renderNotifications );
            renderNotifications();
            container.notifications.bind( 'change', _.debounce( renderNotifications ) );
        },

        /**
         * @since 4.1.0
         *
         * @abstract
         */
        ready: function() {},

        /**
         * Get the child models associated with this parent, sorting them by their priority Value.
         *
         * @since 4.1.0
         *
         * @param {string} parentType
         * @param {string} childType
         * @return {Array}
         */
        _children: function ( parentType, childType ) {
            var parent = this,
                children = [];
            api[ childType ].each( function ( child ) {
                if ( child[ parentType ].get() === parent.id ) {
                    children.push( child );
                }
            } );
            children.sort( api.utils.prioritySort );
            return children;
        },

        /**
         * To override by subclass, to return whether the container has active children.
         *
         * @since 4.1.0
         *
         * @abstract
         */
        isContextuallyActive: function () {
            throw new Error( 'Container.isContextuallyActive() must be overridden in a subclass.' );
        },

        /**
         * Active state change handler.
         *
         * Shows the container if it is active, hides it if not.
         *
         * To override by subclass, update the container's UI to reflect the provided active state.
         *
         * @since 4.1.0
         *
         * @param {boolean}  active - The active state to transiution to.
         * @param {Object}   [args] - Args.
         * @param {Object}   [args.duration] - The duration for the slideUp/slideDown animation.
         * @param {boolean}  [args.unchanged] - Whether the state is already known to not be changed, and so short-circuit with calling completeCallback early.
         * @param {Function} [args.completeCallback] - Function to call when the slideUp/slideDown has completed.
         */
        onChangeActive: function( active, args ) {
            var construct = this,
                headContainer = construct.headContainer,
                duration, expandedOtherPanel;

            if ( args.unchanged ) {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
                return;
            }

            duration = ( 'resolved' === api.previewer.deferred.active.state() ? args.duration : 0 );

            if ( construct.extended( api.Panel ) ) {
                // If this is a panel is not currently expanded but another panel is expanded, do not animate.
                api.panel.each(function ( panel ) {
                    if ( panel !== construct && panel.expanded() ) {
                        expandedOtherPanel = panel;
                        duration = 0;
                    }
                });

                // Collapse any expanded sections inside of this panel first before deactivating.
                if ( ! active ) {
                    _.each( construct.sections(), function( section ) {
                        section.collapse( { duration: 0 } );
                    } );
                }
            }

            if ( ! $.contains( document, headContainer.get( 0 ) ) ) {
                // If the element is not in the DOM, then jQuery.fn.slideUp() does nothing.
                // In this case, a hard toggle is required instead.
                headContainer.toggle( active );
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
            } else if ( active ) {
                headContainer.slideDown( duration, args.completeCallback );
            } else {
                if ( construct.expanded() ) {
                    construct.collapse({
                        duration: duration,
                        completeCallback: function() {
                            headContainer.slideUp( duration, args.completeCallback );
                        }
                    });
                } else {
                    headContainer.slideUp( duration, args.completeCallback );
                }
            }
        },

        /**
         * @since 4.1.0
         *
         * @param {boolean} active
         * @param {Object}  [params]
         * @return {boolean} False if state already applied.
         */
        _toggleActive: function ( active, params ) {
            var self = this;
            params = params || {};
            if ( ( active && this.active.get() ) || ( ! active && ! this.active.get() ) ) {
                params.unchanged = true;
                self.onChangeActive( self.active.get(), params );
                return false;
            } else {
                params.unchanged = false;
                this.activeArgumentsQueue.push( params );
                this.active.set( active );
                return true;
            }
        },

        /**
         * @param {Object} [params]
         * @return {boolean} False if already active.
         */
        activate: function ( params ) {
            return this._toggleActive( true, params );
        },

        /**
         * @param {Object} [params]
         * @return {boolean} False if already inactive.
         */
        deactivate: function ( params ) {
            return this._toggleActive( false, params );
        },

        /**
         * To override by subclass, update the container's UI to reflect the provided active state.
         * @abstract
         */
        onChangeExpanded: function () {
            throw new Error( 'Must override with subclass.' );
        },

        /**
         * Handle the toggle logic for expand/collapse.
         *
         * @param {boolean}  expanded - The new state to apply.
         * @param {Object}   [params] - Object containing options for expand/collapse.
         * @param {Function} [params.completeCallback] - Function to call when expansion/collapse is complete.
         * @return {boolean} False if state already applied or active state is false.
         */
        _toggleExpanded: function( expanded, params ) {
            var instance = this, previousCompleteCallback;
            params = params || {};
            previousCompleteCallback = params.completeCallback;

            // Short-circuit expand() if the instance is not active.
            if ( expanded && ! instance.active() ) {
                return false;
            }

            api.state( 'paneVisible' ).set( true );
            params.completeCallback = function() {
                if ( previousCompleteCallback ) {
                    previousCompleteCallback.apply( instance, arguments );
                }
                if ( expanded ) {
                    instance.container.trigger( 'expanded' );
                } else {
                    instance.container.trigger( 'collapsed' );
                }
            };
            if ( ( expanded && instance.expanded.get() ) || ( ! expanded && ! instance.expanded.get() ) ) {
                params.unchanged = true;
                instance.onChangeExpanded( instance.expanded.get(), params );
                return false;
            } else {
                params.unchanged = false;
                instance.expandedArgumentsQueue.push( params );
                instance.expanded.set( expanded );
                return true;
            }
        },

        /**
         * @param {Object} [params]
         * @return {boolean} False if already expanded or if inactive.
         */
        expand: function ( params ) {
            return this._toggleExpanded( true, params );
        },

        /**
         * @param {Object} [params]
         * @return {boolean} False if already collapsed.
         */
        collapse: function ( params ) {
            return this._toggleExpanded( false, params );
        },

        /**
         * Animate container state change if transitions are supported by the browser.
         *
         * @since 4.7.0
         * @private
         *
         * @param {function} completeCallback Function to be called after transition is completed.
         * @return {void}
         */
        _animateChangeExpanded: function( completeCallback ) {
            // Return if CSS transitions are not supported or if reduced motion is enabled.
            if ( ! normalizedTransitionendEventName || isReducedMotion ) {
                // Schedule the callback until the next tick to prevent focus loss.
                _.defer( function () {
                    if ( completeCallback ) {
                        completeCallback();
                    }
                } );
                return;
            }

            var construct = this,
                content = construct.contentContainer,
                overlay = content.closest( '.wp-full-overlay' ),
                elements, transitionEndCallback, transitionParentPane;

            // Determine set of elements that are affected by the animation.
            elements = overlay.add( content );

            if ( ! construct.panel || '' === construct.panel() ) {
                transitionParentPane = true;
            } else if ( api.panel( construct.panel() ).contentContainer.hasClass( 'skip-transition' ) ) {
                transitionParentPane = true;
            } else {
                transitionParentPane = false;
            }
            if ( transitionParentPane ) {
                elements = elements.add( '#customize-info, .customize-pane-parent' );
            }

            // Handle `transitionEnd` event.
            transitionEndCallback = function( e ) {
                if ( 2 !== e.eventPhase || ! $( e.target ).is( content ) ) {
                    return;
                }
                content.off( normalizedTransitionendEventName, transitionEndCallback );
                elements.removeClass( 'busy' );
                if ( completeCallback ) {
                    completeCallback();
                }
            };
            content.on( normalizedTransitionendEventName, transitionEndCallback );
            elements.addClass( 'busy' );

            // Prevent screen flicker when pane has been scrolled before expanding.
            _.defer( function() {
                var container = content.closest( '.wp-full-overlay-sidebar-content' ),
                    currentScrollTop = container.scrollTop(),
                    previousScrollTop = content.data( 'previous-scrollTop' ) || 0,
                    expanded = construct.expanded();

                if ( expanded && 0 < currentScrollTop ) {
                    content.css( 'top', currentScrollTop + 'px' );
                    content.data( 'previous-scrollTop', currentScrollTop );
                } else if ( ! expanded && 0 < currentScrollTop + previousScrollTop ) {
                    content.css( 'top', previousScrollTop - currentScrollTop + 'px' );
                    container.scrollTop( previousScrollTop );
                }
            } );
        },

        /*
         * is documented using @borrows in the constructor.
         */
        focus: focus,

        /**
         * Return the container html, generated from its JS template, if it exists.
         *
         * @since 4.3.0
         */
        getContainer: function () {
            var template,
                container = this;

            if ( 0 !== $( '#tmpl-' + container.templateSelector ).length ) {
                template = wp.template( container.templateSelector );
            } else {
                template = wp.template( 'customize-' + container.containerType + '-default' );
            }
            if ( template && container.container ) {
                return template( _.extend(
                    { id: container.id },
                    container.params
                ) ).toString().trim();
            }

            return '<li></li>';
        },

        /**
         * Find content element which is displayed when the section is expanded.
         *
         * After a construct is initialized, the return value will be available via the `contentContainer` property.
         * By default the element will be related it to the parent container with `aria-owns` and detached.
         * Custom panels and sections (such as the `NewMenuSection`) that do not have a sliding pane should
         * just return the content element without needing to add the `aria-owns` element or detach it from
         * the container. Such non-sliding pane custom sections also need to override the `onChangeExpanded`
         * method to handle animating the panel/section into and out of view.
         *
         * @since 4.7.0
         * @access public
         *
         * @return {jQuery} Detached content element.
         */
        getContent: function() {
            var construct = this,
                container = construct.container,
                content = container.find( '.accordion-section-content, .control-panel-content' ).first(),
                contentId = 'sub-' + container.attr( 'id' ),
                ownedElements = contentId,
                alreadyOwnedElements = container.attr( 'aria-owns' );

            if ( alreadyOwnedElements ) {
                ownedElements = ownedElements + ' ' + alreadyOwnedElements;
            }
            container.attr( 'aria-owns', ownedElements );

            return content.detach().attr( {
                'id': contentId,
                'class': 'customize-pane-child ' + content.attr( 'class' ) + ' ' + container.attr( 'class' )
            } );
        }
    });

    api.Section = Container.extend(/** @lends wp.customize.Section.prototype */{
        containerType: 'section',
        containerParent: '#customize-theme-controls',
        containerPaneParent: '.customize-pane-parent',
        defaults: {
            title: '',
            description: '',
            priority: 100,
            type: 'default',
            content: null,
            active: true,
            instanceNumber: null,
            panel: null,
            customizeAction: ''
        },

        /**
         * @constructs wp.customize.Section
         * @augments   wp.customize~Container
         *
         * @since 4.1.0
         *
         * @param {string}  id - The ID for the section.
         * @param {Object}  options - Options.
         * @param {string}  options.title - Title shown when section is collapsed and expanded.
         * @param {string}  [options.description] - Description shown at the top of the section.
         * @param {number}  [options.priority=100] - The sort priority for the section.
         * @param {string}  [options.type=default] - The type of the section. See wp.customize.sectionConstructor.
         * @param {string}  [options.content] - The markup to be used for the section container. If empty, a JS template is used.
         * @param {boolean} [options.active=true] - Whether the section is active or not.
         * @param {string}  options.panel - The ID for the panel this section is associated with.
         * @param {string}  [options.customizeAction] - Additional context information shown before the section title when expanded.
         * @param {Object}  [options.params] - Deprecated wrapper for the above properties.
         */
        initialize: function ( id, options ) {
            var section = this, params;
            params = options.params || options;

            // Look up the type if one was not supplied.
            if ( ! params.type ) {
                _.find( api.sectionConstructor, function( Constructor, type ) {
                    if ( Constructor === section.constructor ) {
                        params.type = type;
                        return true;
                    }
                    return false;
                } );
            }

            Container.prototype.initialize.call( section, id, params );

            section.id = id;
            section.panel = new api.Value();
            section.panel.bind( function ( id ) {
                $( section.headContainer ).toggleClass( 'control-subsection', !! id );
            });
            section.panel.set( section.params.panel || '' );
            api.utils.bubbleChildValueChanges( section, [ 'panel' ] );

            section.embed();
            section.deferred.embedded.done( function () {
                section.ready();
            });
        },

        /**
         * Embed the container in the DOM when any parent panel is ready.
         *
         * @since 4.1.0
         */
        embed: function () {
            var inject,
                section = this;

            section.containerParent = api.ensure( section.containerParent );

            // Watch for changes to the panel state.
            inject = function ( panelId ) {
                var parentContainer;
                if ( panelId ) {
                    // The panel has been supplied, so wait until the panel object is registered.
                    api.panel( panelId, function ( panel ) {
                        // The panel has been registered, wait for it to become ready/initialized.
                        panel.deferred.embedded.done( function () {
                            parentContainer = panel.contentContainer;
                            if ( ! section.headContainer.parent().is( parentContainer ) ) {
                                parentContainer.append( section.headContainer );
                            }
                            if ( ! section.contentContainer.parent().is( section.headContainer ) ) {
                                section.containerParent.append( section.contentContainer );
                            }
                            section.deferred.embedded.resolve();
                        });
                    } );
                } else {
                    // There is no panel, so embed the section in the root of the customizer.
                    parentContainer = api.ensure( section.containerPaneParent );
                    if ( ! section.headContainer.parent().is( parentContainer ) ) {
                        parentContainer.append( section.headContainer );
                    }
                    if ( ! section.contentContainer.parent().is( section.headContainer ) ) {
                        section.containerParent.append( section.contentContainer );
                    }
                    section.deferred.embedded.resolve();
                }
            };
            section.panel.bind( inject );
            inject( section.panel.get() ); // Since a section may never get a panel, assume that it won't ever get one.
        },

        /**
         * Add behaviors for the accordion section.
         *
         * @since 4.1.0
         */
        attachEvents: function () {
            var meta, content, section = this;

            if ( section.container.hasClass( 'cannot-expand' ) ) {
                return;
            }

            // Expand/Collapse accordion sections on click.
            section.container.find( '.accordion-section-title, .customize-section-back' ).on( 'click keydown', function( event ) {
                if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                    return;
                }
                event.preventDefault(); // Keep this AFTER the key filter above.

                if ( section.expanded() ) {
                    section.collapse();
                } else {
                    section.expand();
                }
            });

            // This is very similar to what is found for api.Panel.attachEvents().
            section.container.find( '.customize-section-title .customize-help-toggle' ).on( 'click', function() {

                meta = section.container.find( '.section-meta' );
                if ( meta.hasClass( 'cannot-expand' ) ) {
                    return;
                }
                content = meta.find( '.customize-section-description:first' );
                content.toggleClass( 'open' );
                content.slideToggle( section.defaultExpandedArguments.duration, function() {
                    content.trigger( 'toggled' );
                } );
                $( this ).attr( 'aria-expanded', function( i, attr ) {
                    return 'true' === attr ? 'false' : 'true';
                });
            });
        },

        /**
         * Return whether this section has any active controls.
         *
         * @since 4.1.0
         *
         * @return {boolean}
         */
        isContextuallyActive: function () {
            var section = this,
                controls = section.controls(),
                activeCount = 0;
            _( controls ).each( function ( control ) {
                if ( control.active() ) {
                    activeCount += 1;
                }
            } );
            return ( activeCount !== 0 );
        },

        /**
         * Get the controls that are associated with this section, sorted by their priority Value.
         *
         * @since 4.1.0
         *
         * @return {Array}
         */
        controls: function () {
            return this._children( 'section', 'control' );
        },

        /**
         * Update UI to reflect expanded state.
         *
         * @since 4.1.0
         *
         * @param {boolean} expanded
         * @param {Object}  args
         */
        onChangeExpanded: function ( expanded, args ) {
            var section = this,
                container = section.headContainer.closest( '.wp-full-overlay-sidebar-content' ),
                content = section.contentContainer,
                overlay = section.headContainer.closest( '.wp-full-overlay' ),
                backBtn = content.find( '.customize-section-back' ),
                sectionTitle = section.headContainer.find( '.accordion-section-title' ).first(),
                expand, panel;

            if ( expanded && ! content.hasClass( 'open' ) ) {

                if ( args.unchanged ) {
                    expand = args.completeCallback;
                } else {
                    expand = function() {
                        section._animateChangeExpanded( function() {
                            sectionTitle.attr( 'tabindex', '-1' );
                            backBtn.attr( 'tabindex', '0' );

                            backBtn.trigger( 'focus' );
                            content.css( 'top', '' );
                            container.scrollTop( 0 );

                            if ( args.completeCallback ) {
                                args.completeCallback();
                            }
                        } );

                        content.addClass( 'open' );
                        overlay.addClass( 'section-open' );
                        api.state( 'expandedSection' ).set( section );
                    }.bind( this );
                }

                if ( ! args.allowMultiple ) {
                    api.section.each( function ( otherSection ) {
                        if ( otherSection !== section ) {
                            otherSection.collapse( { duration: args.duration } );
                        }
                    });
                }

                if ( section.panel() ) {
                    api.panel( section.panel() ).expand({
                        duration: args.duration,
                        completeCallback: expand
                    });
                } else {
                    if ( ! args.allowMultiple ) {
                        api.panel.each( function( panel ) {
                            panel.collapse();
                        });
                    }
                    expand();
                }

            } else if ( ! expanded && content.hasClass( 'open' ) ) {
                if ( section.panel() ) {
                    panel = api.panel( section.panel() );
                    if ( panel.contentContainer.hasClass( 'skip-transition' ) ) {
                        panel.collapse();
                    }
                }
                section._animateChangeExpanded( function() {
                    backBtn.attr( 'tabindex', '-1' );
                    sectionTitle.attr( 'tabindex', '0' );

                    sectionTitle.trigger( 'focus' );
                    content.css( 'top', '' );

                    if ( args.completeCallback ) {
                        args.completeCallback();
                    }
                } );

                content.removeClass( 'open' );
                overlay.removeClass( 'section-open' );
                if ( section === api.state( 'expandedSection' ).get() ) {
                    api.state( 'expandedSection' ).set( false );
                }

            } else {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
            }
        }
    });

    api.ThemesSection = api.Section.extend(/** @lends wp.customize.ThemesSection.prototype */{
        currentTheme: '',
        overlay: '',
        template: '',
        screenshotQueue: null,
        $window: null,
        $body: null,
        loaded: 0,
        loading: false,
        fullyLoaded: false,
        term: '',
        tags: '',
        nextTerm: '',
        nextTags: '',
        filtersHeight: 0,
        headerContainer: null,
        updateCountDebounced: null,

        /**
         * wp.customize.ThemesSection
         *
         * Custom section for themes that loads themes by category, and also
         * handles the theme-details view rendering and navigation.
         *
         * @constructs wp.customize.ThemesSection
         * @augments   wp.customize.Section
         *
         * @since 4.9.0
         *
         * @param {string} id - ID.
         * @param {Object} options - Options.
         * @return {void}
         */
        initialize: function( id, options ) {
            var section = this;
            section.headerContainer = $();
            section.$window = $( window );
            section.$body = $( document.body );
            api.Section.prototype.initialize.call( section, id, options );
            section.updateCountDebounced = _.debounce( section.updateCount, 500 );
        },

        /**
         * Embed the section in the DOM when the themes panel is ready.
         *
         * Insert the section before the themes container. Assume that a themes section is within a panel, but not necessarily the themes panel.
         *
         * @since 4.9.0
         */
        embed: function() {
            var inject,
                section = this;

            // Watch for changes to the panel state.
            inject = function( panelId ) {
                var parentContainer;
                api.panel( panelId, function( panel ) {

                    // The panel has been registered, wait for it to become ready/initialized.
                    panel.deferred.embedded.done( function() {
                        parentContainer = panel.contentContainer;
                        if ( ! section.headContainer.parent().is( parentContainer ) ) {
                            parentContainer.find( '.customize-themes-full-container-container' ).before( section.headContainer );
                        }
                        if ( ! section.contentContainer.parent().is( section.headContainer ) ) {
                            section.containerParent.append( section.contentContainer );
                        }
                        section.deferred.embedded.resolve();
                    });
                } );
            };
            section.panel.bind( inject );
            inject( section.panel.get() ); // Since a section may never get a panel, assume that it won't ever get one.
        },

        /**
         * Set up.
         *
         * @since 4.2.0
         *
         * @return {void}
         */
        ready: function() {
            var section = this;
            section.overlay = section.container.find( '.theme-overlay' );
            section.template = wp.template( 'customize-themes-details-view' );

            // Bind global keyboard events.
            section.container.on( 'keydown', function( event ) {
                if ( ! section.overlay.find( '.theme-wrap' ).is( ':visible' ) ) {
                    return;
                }

                // Pressing the right arrow key fires a theme:next event.
                if ( 39 === event.keyCode ) {
                    section.nextTheme();
                }

                // Pressing the left arrow key fires a theme:previous event.
                if ( 37 === event.keyCode ) {
                    section.previousTheme();
                }

                // Pressing the escape key fires a theme:collapse event.
                if ( 27 === event.keyCode ) {
                    if ( section.$body.hasClass( 'modal-open' ) ) {

                        // Escape from the details modal.
                        section.closeDetails();
                    } else {

                        // Escape from the infinite scroll list.
                        section.headerContainer.find( '.customize-themes-section-title' ).focus();
                    }
                    event.stopPropagation(); // Prevent section from being collapsed.
                }
            });

            section.renderScreenshots = _.throttle( section.renderScreenshots, 100 );

            _.bindAll( section, 'renderScreenshots', 'loadMore', 'checkTerm', 'filtersChecked' );
        },

        /**
         * Override Section.isContextuallyActive method.
         *
         * Ignore the active states' of the contained theme controls, and just
         * use the section's own active state instead. This prevents empty search
         * results for theme sections from causing the section to become inactive.
         *
         * @since 4.2.0
         *
         * @return {boolean}
         */
        isContextuallyActive: function () {
            return this.active();
        },

        /**
         * Attach events.
         *
         * @since 4.2.0
         *
         * @return {void}
         */
        attachEvents: function () {
            var section = this, debounced;

            // Expand/Collapse accordion sections on click.
            section.container.find( '.customize-section-back' ).on( 'click keydown', function( event ) {
                if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                    return;
                }
                event.preventDefault(); // Keep this AFTER the key filter above.
                section.collapse();
            });

            section.headerContainer = $( '#accordion-section-' + section.id );

            // Expand section/panel. Only collapse when opening another section.
            section.headerContainer.on( 'click', '.customize-themes-section-title', function() {

                // Toggle accordion filters under section headers.
                if ( section.headerContainer.find( '.filter-details' ).length ) {
                    section.headerContainer.find( '.customize-themes-section-title' )
                        .toggleClass( 'details-open' )
                        .attr( 'aria-expanded', function( i, attr ) {
                            return 'true' === attr ? 'false' : 'true';
                        });
                    section.headerContainer.find( '.filter-details' ).slideToggle( 180 );
                }

                // Open the section.
                if ( ! section.expanded() ) {
                    section.expand();
                }
            });

            // Preview installed themes.
            section.container.on( 'click', '.theme-actions .preview-theme', function() {
                api.panel( 'themes' ).loadThemePreview( $( this ).data( 'slug' ) );
            });

            // Theme navigation in details view.
            section.container.on( 'click', '.left', function() {
                section.previousTheme();
            });

            section.container.on( 'click', '.right', function() {
                section.nextTheme();
            });

            section.container.on( 'click', '.theme-backdrop, .close', function() {
                section.closeDetails();
            });

            if ( 'local' === section.params.filter_type ) {

                // Filter-search all theme objects loaded in the section.
                section.container.on( 'input', '.wp-filter-search-themes', function( event ) {
                    section.filterSearch( event.currentTarget.value );
                });

            } else if ( 'remote' === section.params.filter_type ) {

                // Event listeners for remote queries with user-entered terms.
                // Search terms.
                debounced = _.debounce( section.checkTerm, 500 ); // Wait until there is no input for 500 milliseconds to initiate a search.
                section.contentContainer.on( 'input', '.wp-filter-search', function() {
                    if ( ! api.panel( 'themes' ).expanded() ) {
                        return;
                    }
                    debounced( section );
                    if ( ! section.expanded() ) {
                        section.expand();
                    }
                });

                // Feature filters.
                section.contentContainer.on( 'click', '.filter-group input', function() {
                    section.filtersChecked();
                    section.checkTerm( section );
                });
            }

            // Toggle feature filters.
            section.contentContainer.on( 'click', '.feature-filter-toggle', function( e ) {
                var $themeContainer = $( '.customize-themes-full-container' ),
                    $filterToggle = $( e.currentTarget );
                section.filtersHeight = $filterToggle.parent().next( '.filter-drawer' ).height();

                if ( 0 < $themeContainer.scrollTop() ) {
                    $themeContainer.animate( { scrollTop: 0 }, 400 );

                    if ( $filterToggle.hasClass( 'open' ) ) {
                        return;
                    }
                }

                $filterToggle
                    .toggleClass( 'open' )
                    .attr( 'aria-expanded', function( i, attr ) {
                        return 'true' === attr ? 'false' : 'true';
                    })
                    .parent().next( '.filter-drawer' ).slideToggle( 180, 'linear' );

                if ( $filterToggle.hasClass( 'open' ) ) {
                    var marginOffset = 1018 < window.innerWidth ? 50 : 76;

                    section.contentContainer.find( '.themes' ).css( 'margin-top', section.filtersHeight + marginOffset );
                } else {
                    section.contentContainer.find( '.themes' ).css( 'margin-top', 0 );
                }
            });

            // Setup section cross-linking.
            section.contentContainer.on( 'click', '.no-themes-local .search-dotorg-themes', function() {
                api.section( 'wporg_themes' ).focus();
            });

            function updateSelectedState() {
                var el = section.headerContainer.find( '.customize-themes-section-title' );
                el.toggleClass( 'selected', section.expanded() );
                el.attr( 'aria-expanded', section.expanded() ? 'true' : 'false' );
                if ( ! section.expanded() ) {
                    el.removeClass( 'details-open' );
                }
            }
            section.expanded.bind( updateSelectedState );
            updateSelectedState();

            // Move section controls to the themes area.
            api.bind( 'ready', function () {
                section.contentContainer = section.container.find( '.customize-themes-section' );
                section.contentContainer.appendTo( $( '.customize-themes-full-container' ) );
                section.container.add( section.headerContainer );
            });
        },

        /**
         * Update UI to reflect expanded state
         *
         * @since 4.2.0
         *
         * @param {boolean}  expanded
         * @param {Object}   args
         * @param {boolean}  args.unchanged
         * @param {Function} args.completeCallback
         * @return {void}
         */
        onChangeExpanded: function ( expanded, args ) {

            // Note: there is a second argument 'args' passed.
            var section = this,
                container = section.contentContainer.closest( '.customize-themes-full-container' );

            // Immediately call the complete callback if there were no changes.
            if ( args.unchanged ) {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
                return;
            }

            function expand() {

                // Try to load controls if none are loaded yet.
                if ( 0 === section.loaded ) {
                    section.loadThemes();
                }

                // Collapse any sibling sections/panels.
                api.section.each( function ( otherSection ) {
                    var searchTerm;

                    if ( otherSection !== section ) {

                        // Try to sync the current search term to the new section.
                        if ( 'themes' === otherSection.params.type ) {
                            searchTerm = otherSection.contentContainer.find( '.wp-filter-search' ).val();
                            section.contentContainer.find( '.wp-filter-search' ).val( searchTerm );

                            // Directly initialize an empty remote search to avoid a race condition.
                            if ( '' === searchTerm && '' !== section.term && 'local' !== section.params.filter_type ) {
                                section.term = '';
                                section.initializeNewQuery( section.term, section.tags );
                            } else {
                                if ( 'remote' === section.params.filter_type ) {
                                    section.checkTerm( section );
                                } else if ( 'local' === section.params.filter_type ) {
                                    section.filterSearch( searchTerm );
                                }
                            }
                            otherSection.collapse( { duration: args.duration } );
                        }
                    }
                });

                section.contentContainer.addClass( 'current-section' );
                container.scrollTop();

                container.on( 'scroll', _.throttle( section.renderScreenshots, 300 ) );
                container.on( 'scroll', _.throttle( section.loadMore, 300 ) );

                if ( args.completeCallback ) {
                    args.completeCallback();
                }
                section.updateCount(); // Show this section's count.
            }

            if ( expanded ) {
                if ( section.panel() && api.panel.has( section.panel() ) ) {
                    api.panel( section.panel() ).expand({
                        duration: args.duration,
                        completeCallback: expand
                    });
                } else {
                    expand();
                }
            } else {
                section.contentContainer.removeClass( 'current-section' );

                // Always hide, even if they don't exist or are already hidden.
                section.headerContainer.find( '.filter-details' ).slideUp( 180 );

                container.off( 'scroll' );

                if ( args.completeCallback ) {
                    args.completeCallback();
                }
            }
        },

        /**
         * Return the section's content element without detaching from the parent.
         *
         * @since 4.9.0
         *
         * @return {jQuery}
         */
        getContent: function() {
            return this.container.find( '.control-section-content' );
        },

        /**
         * Load theme data via Ajax and add themes to the section as controls.
         *
         * @since 4.9.0
         *
         * @return {void}
         */
        loadThemes: function() {
            var section = this, params, page, request;

            if ( section.loading ) {
                return; // We're already loading a batch of themes.
            }

            // Parameters for every API query. Additional params are set in PHP.
            page = Math.ceil( section.loaded / 100 ) + 1;
            params = {
                'nonce': api.settings.nonce.switch_themes,
                'wp_customize': 'on',
                'theme_action': section.params.action,
                'customized_theme': api.settings.theme.stylesheet,
                'page': page
            };

            // Add fields for remote filtering.
            if ( 'remote' === section.params.filter_type ) {
                params.search = section.term;
                params.tags = section.tags;
            }

            // Load themes.
            section.headContainer.closest( '.wp-full-overlay' ).addClass( 'loading' );
            section.loading = true;
            section.container.find( '.no-themes' ).hide();
            request = wp.ajax.post( 'customize_load_themes', params );
            request.done(function( data ) {
                var themes = data.themes;

                // Stop and try again if the term changed while loading.
                if ( '' !== section.nextTerm || '' !== section.nextTags ) {
                    if ( section.nextTerm ) {
                        section.term = section.nextTerm;
                    }
                    if ( section.nextTags ) {
                        section.tags = section.nextTags;
                    }
                    section.nextTerm = '';
                    section.nextTags = '';
                    section.loading = false;
                    section.loadThemes();
                    return;
                }

                if ( 0 !== themes.length ) {

                    section.loadControls( themes, page );

                    if ( 1 === page ) {

                        // Pre-load the first 3 theme screenshots.
                        _.each( section.controls().slice( 0, 3 ), function( control ) {
                            var img, src = control.params.theme.screenshot[0];
                            if ( src ) {
                                img = new Image();
                                img.src = src;
                            }
                        });
                        if ( 'local' !== section.params.filter_type ) {
                            wp.a11y.speak( api.settings.l10n.themeSearchResults.replace( '%d', data.info.results ) );
                        }
                    }

                    _.delay( section.renderScreenshots, 100 ); // Wait for the controls to become visible.

                    if ( 'local' === section.params.filter_type || 100 > themes.length ) {
                        // If we have less than the requested 100 themes, it's the end of the list.
                        section.fullyLoaded = true;
                    }
                } else {
                    if ( 0 === section.loaded ) {
                        section.container.find( '.no-themes' ).show();
                        wp.a11y.speak( section.container.find( '.no-themes' ).text() );
                    } else {
                        section.fullyLoaded = true;
                    }
                }
                if ( 'local' === section.params.filter_type ) {
                    section.updateCount(); // Count of visible theme controls.
                } else {
                    section.updateCount( data.info.results ); // Total number of results including pages not yet loaded.
                }
                section.container.find( '.unexpected-error' ).hide(); // Hide error notice in case it was previously shown.

                // This cannot run on request.always, as section.loading may turn false before the new controls load in the success case.
                section.headContainer.closest( '.wp-full-overlay' ).removeClass( 'loading' );
                section.loading = false;
            });
            request.fail(function( data ) {
                if ( 'undefined' === typeof data ) {
                    section.container.find( '.unexpected-error' ).show();
                    wp.a11y.speak( section.container.find( '.unexpected-error' ).text() );
                } else if ( 'undefined' !== typeof console && console.error ) {
                    console.error( data );
                }

                // This cannot run on request.always, as section.loading may turn false before the new controls load in the success case.
                section.headContainer.closest( '.wp-full-overlay' ).removeClass( 'loading' );
                section.loading = false;
            });
        },

        /**
         * Loads controls into the section from data received from loadThemes().
         *
         * @since 4.9.0
         * @param {Array}  themes - Array of theme data to create controls with.
         * @param {number} page   - Page of results being loaded.
         * @return {void}
         */
        loadControls: function( themes, page ) {
            var newThemeControls = [],
                section = this;

            // Add controls for each theme.
            _.each( themes, function( theme ) {
                var themeControl = new api.controlConstructor.theme( section.params.action + '_theme_' + theme.id, {
                    type: 'theme',
                    section: section.params.id,
                    theme: theme,
                    priority: section.loaded + 1
                } );

                api.control.add( themeControl );
                newThemeControls.push( themeControl );
                section.loaded = section.loaded + 1;
            });

            if ( 1 !== page ) {
                Array.prototype.push.apply( section.screenshotQueue, newThemeControls ); // Add new themes to the screenshot queue.
            }
        },

        /**
         * Determines whether more themes should be loaded, and loads them.
         *
         * @since 4.9.0
         * @return {void}
         */
        loadMore: function() {
            var section = this, container, bottom, threshold;
            if ( ! section.fullyLoaded && ! section.loading ) {
                container = section.container.closest( '.customize-themes-full-container' );

                bottom = container.scrollTop() + container.height();
                // Use a fixed distance to the bottom of loaded results to avoid unnecessarily
                // loading results sooner when using a percentage of scroll distance.
                threshold = container.prop( 'scrollHeight' ) - 3000;

                if ( bottom > threshold ) {
                    section.loadThemes();
                }
            }
        },

        /**
         * Event handler for search input that filters visible controls.
         *
         * @since 4.9.0
         *
         * @param {string} term - The raw search input value.
         * @return {void}
         */
        filterSearch: function( term ) {
            var count = 0,
                visible = false,
                section = this,
                noFilter = ( api.section.has( 'wporg_themes' ) && 'remote' !== section.params.filter_type ) ? '.no-themes-local' : '.no-themes',
                controls = section.controls(),
                terms;

            if ( section.loading ) {
                return;
            }

            // Standardize search term format and split into an array of individual words.
            terms = term.toLowerCase().trim().replace( /-/g, ' ' ).split( ' ' );

            _.each( controls, function( control ) {
                visible = control.filter( terms ); // Shows/hides and sorts control based on the applicability of the search term.
                if ( visible ) {
                    count = count + 1;
                }
            });

            if ( 0 === count ) {
                section.container.find( noFilter ).show();
                wp.a11y.speak( section.container.find( noFilter ).text() );
            } else {
                section.container.find( noFilter ).hide();
            }

            section.renderScreenshots();
            api.reflowPaneContents();

            // Update theme count.
            section.updateCountDebounced( count );
        },

        /**
         * Event handler for search input that determines if the terms have changed and loads new controls as needed.
         *
         * @since 4.9.0
         *
         * @param {wp.customize.ThemesSection} section - The current theme section, passed through the debouncer.
         * @return {void}
         */
        checkTerm: function( section ) {
            var newTerm;
            if ( 'remote' === section.params.filter_type ) {
                newTerm = section.contentContainer.find( '.wp-filter-search' ).val();
                if ( section.term !== newTerm.trim() ) {
                    section.initializeNewQuery( newTerm, section.tags );
                }
            }
        },

        /**
         * Check for filters checked in the feature filter list and initialize a new query.
         *
         * @since 4.9.0
         *
         * @return {void}
         */
        filtersChecked: function() {
            var section = this,
                items = section.container.find( '.filter-group' ).find( ':checkbox' ),
                tags = [];

            _.each( items.filter( ':checked' ), function( item ) {
                tags.push( $( item ).prop( 'value' ) );
            });

            // When no filters are checked, restore initial state. Update filter count.
            if ( 0 === tags.length ) {
                tags = '';
                section.contentContainer.find( '.feature-filter-toggle .filter-count-0' ).show();
                section.contentContainer.find( '.feature-filter-toggle .filter-count-filters' ).hide();
            } else {
                section.contentContainer.find( '.feature-filter-toggle .theme-filter-count' ).text( tags.length );
                section.contentContainer.find( '.feature-filter-toggle .filter-count-0' ).hide();
                section.contentContainer.find( '.feature-filter-toggle .filter-count-filters' ).show();
            }

            // Check whether tags have changed, and either load or queue them.
            if ( ! _.isEqual( section.tags, tags ) ) {
                if ( section.loading ) {
                    section.nextTags = tags;
                } else {
                    if ( 'remote' === section.params.filter_type ) {
                        section.initializeNewQuery( section.term, tags );
                    } else if ( 'local' === section.params.filter_type ) {
                        section.filterSearch( tags.join( ' ' ) );
                    }
                }
            }
        },

        /**
         * Reset the current query and load new results.
         *
         * @since 4.9.0
         *
         * @param {string} newTerm - New term.
         * @param {Array} newTags - New tags.
         * @return {void}
         */
        initializeNewQuery: function( newTerm, newTags ) {
            var section = this;

            // Clear the controls in the section.
            _.each( section.controls(), function( control ) {
                control.container.remove();
                api.control.remove( control.id );
            });
            section.loaded = 0;
            section.fullyLoaded = false;
            section.screenshotQueue = null;

            // Run a new query, with loadThemes handling paging, etc.
            if ( ! section.loading ) {
                section.term = newTerm;
                section.tags = newTags;
                section.loadThemes();
            } else {
                section.nextTerm = newTerm; // This will reload from loadThemes() with the newest term once the current batch is loaded.
                section.nextTags = newTags; // This will reload from loadThemes() with the newest tags once the current batch is loaded.
            }
            if ( ! section.expanded() ) {
                section.expand(); // Expand the section if it isn't expanded.
            }
        },

        /**
         * Render control's screenshot if the control comes into view.
         *
         * @since 4.2.0
         *
         * @return {void}
         */
        renderScreenshots: function() {
            var section = this;

            // Fill queue initially, or check for more if empty.
            if ( null === section.screenshotQueue || 0 === section.screenshotQueue.length ) {

                // Add controls that haven't had their screenshots rendered.
                section.screenshotQueue = _.filter( section.controls(), function( control ) {
                    return ! control.screenshotRendered;
                });
            }

            // Are all screenshots rendered (for now)?
            if ( ! section.screenshotQueue.length ) {
                return;
            }

            section.screenshotQueue = _.filter( section.screenshotQueue, function( control ) {
                var $imageWrapper = control.container.find( '.theme-screenshot' ),
                    $image = $imageWrapper.find( 'img' );

                if ( ! $image.length ) {
                    return false;
                }

                if ( $image.is( ':hidden' ) ) {
                    return true;
                }

                // Based on unveil.js.
                var wt = section.$window.scrollTop(),
                    wb = wt + section.$window.height(),
                    et = $image.offset().top,
                    ih = $imageWrapper.height(),
                    eb = et + ih,
                    threshold = ih * 3,
                    inView = eb >= wt - threshold && et <= wb + threshold;

                if ( inView ) {
                    control.container.trigger( 'render-screenshot' );
                }

                // If the image is in view return false so it's cleared from the queue.
                return ! inView;
            } );
        },

        /**
         * Get visible count.
         *
         * @since 4.9.0
         *
         * @return {number} Visible count.
         */
        getVisibleCount: function() {
            return this.contentContainer.find( 'li.customize-control:visible' ).length;
        },

        /**
         * Update the number of themes in the section.
         *
         * @since 4.9.0
         *
         * @return {void}
         */
        updateCount: function( count ) {
            var section = this, countEl, displayed;

            if ( ! count && 0 !== count ) {
                count = section.getVisibleCount();
            }

            displayed = section.contentContainer.find( '.themes-displayed' );
            countEl = section.contentContainer.find( '.theme-count' );

            if ( 0 === count ) {
                countEl.text( '0' );
            } else {

                // Animate the count change for emphasis.
                displayed.fadeOut( 180, function() {
                    countEl.text( count );
                    displayed.fadeIn( 180 );
                } );
                wp.a11y.speak( api.settings.l10n.announceThemeCount.replace( '%d', count ) );
            }
        },

        /**
         * Advance the modal to the next theme.
         *
         * @since 4.2.0
         *
         * @return {void}
         */
        nextTheme: function () {
            var section = this;
            if ( section.getNextTheme() ) {
                section.showDetails( section.getNextTheme(), function() {
                    section.overlay.find( '.right' ).focus();
                } );
            }
        },

        /**
         * Get the next theme model.
         *
         * @since 4.2.0
         *
         * @return {wp.customize.ThemeControl|boolean} Next theme.
         */
        getNextTheme: function () {
            var section = this, control, nextControl, sectionControls, i;
            control = api.control( section.params.action + '_theme_' + section.currentTheme );
            sectionControls = section.controls();
            i = _.indexOf( sectionControls, control );
            if ( -1 === i ) {
                return false;
            }

            nextControl = sectionControls[ i + 1 ];
            if ( ! nextControl ) {
                return false;
            }
            return nextControl.params.theme;
        },

        /**
         * Advance the modal to the previous theme.
         *
         * @since 4.2.0
         * @return {void}
         */
        previousTheme: function () {
            var section = this;
            if ( section.getPreviousTheme() ) {
                section.showDetails( section.getPreviousTheme(), function() {
                    section.overlay.find( '.left' ).focus();
                } );
            }
        },

        /**
         * Get the previous theme model.
         *
         * @since 4.2.0
         * @return {wp.customize.ThemeControl|boolean} Previous theme.
         */
        getPreviousTheme: function () {
            var section = this, control, nextControl, sectionControls, i;
            control = api.control( section.params.action + '_theme_' + section.currentTheme );
            sectionControls = section.controls();
            i = _.indexOf( sectionControls, control );
            if ( -1 === i ) {
                return false;
            }

            nextControl = sectionControls[ i - 1 ];
            if ( ! nextControl ) {
                return false;
            }
            return nextControl.params.theme;
        },

        /**
         * Disable buttons when we're viewing the first or last theme.
         *
         * @since 4.2.0
         *
         * @return {void}
         */
        updateLimits: function () {
            if ( ! this.getNextTheme() ) {
                this.overlay.find( '.right' ).addClass( 'disabled' );
            }
            if ( ! this.getPreviousTheme() ) {
                this.overlay.find( '.left' ).addClass( 'disabled' );
            }
        },

        /**
         * Load theme preview.
         *
         * @since 4.7.0
         * @access public
         *
         * @deprecated
         * @param {string} themeId Theme ID.
         * @return {jQuery.promise} Promise.
         */
        loadThemePreview: function( themeId ) {
            return api.ThemesPanel.prototype.loadThemePreview.call( this, themeId );
        },

        /**
         * Render & show the theme details for a given theme model.
         *
         * @since 4.2.0
         *
         * @param {Object} theme - Theme.
         * @param {Function} [callback] - Callback once the details have been shown.
         * @return {void}
         */
        showDetails: function ( theme, callback ) {
            var section = this, panel = api.panel( 'themes' );
            section.currentTheme = theme.id;
            section.overlay.html( section.template( theme ) )
                .fadeIn( 'fast' )
                .focus();

            function disableSwitchButtons() {
                return ! panel.canSwitchTheme( theme.id );
            }

            // Temporary special function since supplying SFTP credentials does not work yet. See #42184.
            function disableInstallButtons() {
                return disableSwitchButtons() || false === api.settings.theme._canInstall || true === api.settings.theme._filesystemCredentialsNeeded;
            }

            section.overlay.find( 'button.preview, button.preview-theme' ).toggleClass( 'disabled', disableSwitchButtons() );
            section.overlay.find( 'button.theme-install' ).toggleClass( 'disabled', disableInstallButtons() );

            section.$body.addClass( 'modal-open' );
            section.containFocus( section.overlay );
            section.updateLimits();
            wp.a11y.speak( api.settings.l10n.announceThemeDetails.replace( '%s', theme.name ) );
            if ( callback ) {
                callback();
            }
        },

        /**
         * Close the theme details modal.
         *
         * @since 4.2.0
         *
         * @return {void}
         */
        closeDetails: function () {
            var section = this;
            section.$body.removeClass( 'modal-open' );
            section.overlay.fadeOut( 'fast' );
            api.control( section.params.action + '_theme_' + section.currentTheme ).container.find( '.theme' ).focus();
        },

        /**
         * Keep tab focus within the theme details modal.
         *
         * @since 4.2.0
         *
         * @param {jQuery} el - Element to contain focus.
         * @return {void}
         */
        containFocus: function( el ) {
            var tabbables;

            el.on( 'keydown', function( event ) {

                // Return if it's not the tab key
                // When navigating with prev/next focus is already handled.
                if ( 9 !== event.keyCode ) {
                    return;
                }

                // Uses jQuery UI to get the tabbable elements.
                tabbables = $( ':tabbable', el );

                // Keep focus within the overlay.
                if ( tabbables.last()[0] === event.target && ! event.shiftKey ) {
                    tabbables.first().focus();
                    return false;
                } else if ( tabbables.first()[0] === event.target && event.shiftKey ) {
                    tabbables.last().focus();
                    return false;
                }
            });
        }
    });

    api.OuterSection = api.Section.extend(/** @lends wp.customize.OuterSection.prototype */{

        /**
         * Class wp.customize.OuterSection.
         *
         * Creates section outside of the sidebar, there is no ui to trigger collapse/expand so
         * it would require custom handling.
         *
         * @constructs wp.customize.OuterSection
         * @augments   wp.customize.Section
         *
         * @since 4.9.0
         *
         * @return {void}
         */
        initialize: function() {
            var section = this;
            section.containerParent = '#customize-outer-theme-controls';
            section.containerPaneParent = '.customize-outer-pane-parent';
            api.Section.prototype.initialize.apply( section, arguments );
        },

        /**
         * Overrides api.Section.prototype.onChangeExpanded to prevent collapse/expand effect
         * on other sections and panels.
         *
         * @since 4.9.0
         *
         * @param {boolean}  expanded - The expanded state to transition to.
         * @param {Object}   [args] - Args.
         * @param {boolean}  [args.unchanged] - Whether the state is already known to not be changed, and so short-circuit with calling completeCallback early.
         * @param {Function} [args.completeCallback] - Function to call when the slideUp/slideDown has completed.
         * @param {Object}   [args.duration] - The duration for the animation.
         */
        onChangeExpanded: function( expanded, args ) {
            var section = this,
                container = section.headContainer.closest( '.wp-full-overlay-sidebar-content' ),
                content = section.contentContainer,
                backBtn = content.find( '.customize-section-back' ),
                sectionTitle = section.headContainer.find( '.accordion-section-title' ).first(),
                body = $( document.body ),
                expand, panel;

            body.toggleClass( 'outer-section-open', expanded );
            section.container.toggleClass( 'open', expanded );
            section.container.removeClass( 'busy' );
            api.section.each( function( _section ) {
                if ( 'outer' === _section.params.type && _section.id !== section.id ) {
                    _section.container.removeClass( 'open' );
                }
            } );

            if ( expanded && ! content.hasClass( 'open' ) ) {

                if ( args.unchanged ) {
                    expand = args.completeCallback;
                } else {
                    expand = function() {
                        section._animateChangeExpanded( function() {
                            sectionTitle.attr( 'tabindex', '-1' );
                            backBtn.attr( 'tabindex', '0' );

                            backBtn.trigger( 'focus' );
                            content.css( 'top', '' );
                            container.scrollTop( 0 );

                            if ( args.completeCallback ) {
                                args.completeCallback();
                            }
                        } );

                        content.addClass( 'open' );
                    }.bind( this );
                }

                if ( section.panel() ) {
                    api.panel( section.panel() ).expand({
                        duration: args.duration,
                        completeCallback: expand
                    });
                } else {
                    expand();
                }

            } else if ( ! expanded && content.hasClass( 'open' ) ) {
                if ( section.panel() ) {
                    panel = api.panel( section.panel() );
                    if ( panel.contentContainer.hasClass( 'skip-transition' ) ) {
                        panel.collapse();
                    }
                }
                section._animateChangeExpanded( function() {
                    backBtn.attr( 'tabindex', '-1' );
                    sectionTitle.attr( 'tabindex', '0' );

                    sectionTitle.trigger( 'focus' );
                    content.css( 'top', '' );

                    if ( args.completeCallback ) {
                        args.completeCallback();
                    }
                } );

                content.removeClass( 'open' );

            } else {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
            }
        }
    });

    api.Panel = Container.extend(/** @lends wp.customize.Panel.prototype */{
        containerType: 'panel',

        /**
         * @constructs wp.customize.Panel
         * @augments   wp.customize~Container
         *
         * @since 4.1.0
         *
         * @param {string}  id - The ID for the panel.
         * @param {Object}  options - Object containing one property: params.
         * @param {string}  options.title - Title shown when panel is collapsed and expanded.
         * @param {string}  [options.description] - Description shown at the top of the panel.
         * @param {number}  [options.priority=100] - The sort priority for the panel.
         * @param {string}  [options.type=default] - The type of the panel. See wp.customize.panelConstructor.
         * @param {string}  [options.content] - The markup to be used for the panel container. If empty, a JS template is used.
         * @param {boolean} [options.active=true] - Whether the panel is active or not.
         * @param {Object}  [options.params] - Deprecated wrapper for the above properties.
         */
        initialize: function ( id, options ) {
            var panel = this, params;
            params = options.params || options;

            // Look up the type if one was not supplied.
            if ( ! params.type ) {
                _.find( api.panelConstructor, function( Constructor, type ) {
                    if ( Constructor === panel.constructor ) {
                        params.type = type;
                        return true;
                    }
                    return false;
                } );
            }

            Container.prototype.initialize.call( panel, id, params );

            panel.embed();
            panel.deferred.embedded.done( function () {
                panel.ready();
            });
        },

        /**
         * Embed the container in the DOM when any parent panel is ready.
         *
         * @since 4.1.0
         */
        embed: function () {
            var panel = this,
                container = $( '#customize-theme-controls' ),
                parentContainer = $( '.customize-pane-parent' ); // @todo This should be defined elsewhere, and to be configurable.

            if ( ! panel.headContainer.parent().is( parentContainer ) ) {
                parentContainer.append( panel.headContainer );
            }
            if ( ! panel.contentContainer.parent().is( panel.headContainer ) ) {
                container.append( panel.contentContainer );
            }
            panel.renderContent();

            panel.deferred.embedded.resolve();
        },

        /**
         * @since 4.1.0
         */
        attachEvents: function () {
            var meta, panel = this;

            // Expand/Collapse accordion sections on click.
            panel.headContainer.find( '.accordion-section-title' ).on( 'click keydown', function( event ) {
                if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                    return;
                }
                event.preventDefault(); // Keep this AFTER the key filter above.

                if ( ! panel.expanded() ) {
                    panel.expand();
                }
            });

            // Close panel.
            panel.container.find( '.customize-panel-back' ).on( 'click keydown', function( event ) {
                if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                    return;
                }
                event.preventDefault(); // Keep this AFTER the key filter above.

                if ( panel.expanded() ) {
                    panel.collapse();
                }
            });

            meta = panel.container.find( '.panel-meta:first' );

            meta.find( '> .accordion-section-title .customize-help-toggle' ).on( 'click', function() {
                if ( meta.hasClass( 'cannot-expand' ) ) {
                    return;
                }

                var content = meta.find( '.customize-panel-description:first' );
                if ( meta.hasClass( 'open' ) ) {
                    meta.toggleClass( 'open' );
                    content.slideUp( panel.defaultExpandedArguments.duration, function() {
                        content.trigger( 'toggled' );
                    } );
                    $( this ).attr( 'aria-expanded', false );
                } else {
                    content.slideDown( panel.defaultExpandedArguments.duration, function() {
                        content.trigger( 'toggled' );
                    } );
                    meta.toggleClass( 'open' );
                    $( this ).attr( 'aria-expanded', true );
                }
            });

        },

        /**
         * Get the sections that are associated with this panel, sorted by their priority Value.
         *
         * @since 4.1.0
         *
         * @return {Array}
         */
        sections: function () {
            return this._children( 'panel', 'section' );
        },

        /**
         * Return whether this panel has any active sections.
         *
         * @since 4.1.0
         *
         * @return {boolean} Whether contextually active.
         */
        isContextuallyActive: function () {
            var panel = this,
                sections = panel.sections(),
                activeCount = 0;
            _( sections ).each( function ( section ) {
                if ( section.active() && section.isContextuallyActive() ) {
                    activeCount += 1;
                }
            } );
            return ( activeCount !== 0 );
        },

        /**
         * Update UI to reflect expanded state.
         *
         * @since 4.1.0
         *
         * @param {boolean}  expanded
         * @param {Object}   args
         * @param {boolean}  args.unchanged
         * @param {Function} args.completeCallback
         * @return {void}
         */
        onChangeExpanded: function ( expanded, args ) {

            // Immediately call the complete callback if there were no changes.
            if ( args.unchanged ) {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
                return;
            }

            // Note: there is a second argument 'args' passed.
            var panel = this,
                accordionSection = panel.contentContainer,
                overlay = accordionSection.closest( '.wp-full-overlay' ),
                container = accordionSection.closest( '.wp-full-overlay-sidebar-content' ),
                topPanel = panel.headContainer.find( '.accordion-section-title' ),
                backBtn = accordionSection.find( '.customize-panel-back' ),
                childSections = panel.sections(),
                skipTransition;

            if ( expanded && ! accordionSection.hasClass( 'current-panel' ) ) {
                // Collapse any sibling sections/panels.
                api.section.each( function ( section ) {
                    if ( panel.id !== section.panel() ) {
                        section.collapse( { duration: 0 } );
                    }
                });
                api.panel.each( function ( otherPanel ) {
                    if ( panel !== otherPanel ) {
                        otherPanel.collapse( { duration: 0 } );
                    }
                });

                if ( panel.params.autoExpandSoleSection && 1 === childSections.length && childSections[0].active.get() ) {
                    accordionSection.addClass( 'current-panel skip-transition' );
                    overlay.addClass( 'in-sub-panel' );

                    childSections[0].expand( {
                        completeCallback: args.completeCallback
                    } );
                } else {
                    panel._animateChangeExpanded( function() {
                        topPanel.attr( 'tabindex', '-1' );
                        backBtn.attr( 'tabindex', '0' );

                        backBtn.trigger( 'focus' );
                        accordionSection.css( 'top', '' );
                        container.scrollTop( 0 );

                        if ( args.completeCallback ) {
                            args.completeCallback();
                        }
                    } );

                    accordionSection.addClass( 'current-panel' );
                    overlay.addClass( 'in-sub-panel' );
                }

                api.state( 'expandedPanel' ).set( panel );

            } else if ( ! expanded && accordionSection.hasClass( 'current-panel' ) ) {
                skipTransition = accordionSection.hasClass( 'skip-transition' );
                if ( ! skipTransition ) {
                    panel._animateChangeExpanded( function() {
                        topPanel.attr( 'tabindex', '0' );
                        backBtn.attr( 'tabindex', '-1' );

                        topPanel.focus();
                        accordionSection.css( 'top', '' );

                        if ( args.completeCallback ) {
                            args.completeCallback();
                        }
                    } );
                } else {
                    accordionSection.removeClass( 'skip-transition' );
                }

                overlay.removeClass( 'in-sub-panel' );
                accordionSection.removeClass( 'current-panel' );
                if ( panel === api.state( 'expandedPanel' ).get() ) {
                    api.state( 'expandedPanel' ).set( false );
                }
            }
        },

        /**
         * Render the panel from its JS template, if it exists.
         *
         * The panel's container must already exist in the DOM.
         *
         * @since 4.3.0
         */
        renderContent: function () {
            var template,
                panel = this;

            // Add the content to the container.
            if ( 0 !== $( '#tmpl-' + panel.templateSelector + '-content' ).length ) {
                template = wp.template( panel.templateSelector + '-content' );
            } else {
                template = wp.template( 'customize-panel-default-content' );
            }
            if ( template && panel.headContainer ) {
                panel.contentContainer.html( template( _.extend(
                    { id: panel.id },
                    panel.params
                ) ) );
            }
        }
    });

    api.ThemesPanel = api.Panel.extend(/** @lends wp.customize.ThemsPanel.prototype */{

        /**
         *  Class wp.customize.ThemesPanel.
         *
         * Custom section for themes that displays without the customize preview.
         *
         * @constructs wp.customize.ThemesPanel
         * @augments   wp.customize.Panel
         *
         * @since 4.9.0
         *
         * @param {string} id - The ID for the panel.
         * @param {Object} options - Options.
         * @return {void}
         */
        initialize: function( id, options ) {
            var panel = this;
            panel.installingThemes = [];
            api.Panel.prototype.initialize.call( panel, id, options );
        },

        /**
         * Determine whether a given theme can be switched to, or in general.
         *
         * @since 4.9.0
         *
         * @param {string} [slug] - Theme slug.
         * @return {boolean} Whether the theme can be switched to.
         */
        canSwitchTheme: function canSwitchTheme( slug ) {
            if ( slug && slug === api.settings.theme.stylesheet ) {
                return true;
            }
            return 'publish' === api.state( 'selectedChangesetStatus' ).get() && ( '' === api.state( 'changesetStatus' ).get() || 'auto-draft' === api.state( 'changesetStatus' ).get() );
        },

        /**
         * Attach events.
         *
         * @since 4.9.0
         * @return {void}
         */
        attachEvents: function() {
            var panel = this;

            // Attach regular panel events.
            api.Panel.prototype.attachEvents.apply( panel );

            // Temporary since supplying SFTP credentials does not work yet. See #42184.
            if ( api.settings.theme._canInstall && api.settings.theme._filesystemCredentialsNeeded ) {
                panel.notifications.add( new api.Notification( 'theme_install_unavailable', {
                    message: api.l10n.themeInstallUnavailable,
                    type: 'info',
                    dismissible: true
                } ) );
            }

            function toggleDisabledNotifications() {
                if ( panel.canSwitchTheme() ) {
                    panel.notifications.remove( 'theme_switch_unavailable' );
                } else {
                    panel.notifications.add( new api.Notification( 'theme_switch_unavailable', {
                        message: api.l10n.themePreviewUnavailable,
                        type: 'warning'
                    } ) );
                }
            }
            toggleDisabledNotifications();
            api.state( 'selectedChangesetStatus' ).bind( toggleDisabledNotifications );
            api.state( 'changesetStatus' ).bind( toggleDisabledNotifications );

            // Collapse panel to customize the current theme.
            panel.contentContainer.on( 'click', '.customize-theme', function() {
                panel.collapse();
            });

            // Toggle between filtering and browsing themes on mobile.
            panel.contentContainer.on( 'click', '.customize-themes-section-title, .customize-themes-mobile-back', function() {
                $( '.wp-full-overlay' ).toggleClass( 'showing-themes' );
            });

            // Install (and maybe preview) a theme.
            panel.contentContainer.on( 'click', '.theme-install', function( event ) {
                panel.installTheme( event );
            });

            // Update a theme. Theme cards have the class, the details modal has the id.
            panel.contentContainer.on( 'click', '.update-theme, #update-theme', function( event ) {

                // #update-theme is a link.
                event.preventDefault();
                event.stopPropagation();

                panel.updateTheme( event );
            });

            // Delete a theme.
            panel.contentContainer.on( 'click', '.delete-theme', function( event ) {
                panel.deleteTheme( event );
            });

            _.bindAll( panel, 'installTheme', 'updateTheme' );
        },

        /**
         * Update UI to reflect expanded state
         *
         * @since 4.9.0
         *
         * @param {boolean}  expanded - Expanded state.
         * @param {Object}   args - Args.
         * @param {boolean}  args.unchanged - Whether or not the state changed.
         * @param {Function} args.completeCallback - Callback to execute when the animation completes.
         * @return {void}
         */
        onChangeExpanded: function( expanded, args ) {
            var panel = this, overlay, sections, hasExpandedSection = false;

            // Expand/collapse the panel normally.
            api.Panel.prototype.onChangeExpanded.apply( this, [ expanded, args ] );

            // Immediately call the complete callback if there were no changes.
            if ( args.unchanged ) {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
                return;
            }

            overlay = panel.headContainer.closest( '.wp-full-overlay' );

            if ( expanded ) {
                overlay
                    .addClass( 'in-themes-panel' )
                    .delay( 200 ).find( '.customize-themes-full-container' ).addClass( 'animate' );

                _.delay( function() {
                    overlay.addClass( 'themes-panel-expanded' );
                }, 200 );

                // Automatically open the first section (except on small screens), if one isn't already expanded.
                if ( 600 < window.innerWidth ) {
                    sections = panel.sections();
                    _.each( sections, function( section ) {
                        if ( section.expanded() ) {
                            hasExpandedSection = true;
                        }
                    } );
                    if ( ! hasExpandedSection && sections.length > 0 ) {
                        sections[0].expand();
                    }
                }
            } else {
                overlay
                    .removeClass( 'in-themes-panel themes-panel-expanded' )
                    .find( '.customize-themes-full-container' ).removeClass( 'animate' );
            }
        },

        /**
         * Install a theme via wp.updates.
         *
         * @since 4.9.0
         *
         * @param {jQuery.Event} event - Event.
         * @return {jQuery.promise} Promise.
         */
        installTheme: function( event ) {
            var panel = this, preview, onInstallSuccess, slug = $( event.target ).data( 'slug' ), deferred = $.Deferred(), request;
            preview = $( event.target ).hasClass( 'preview' );

            // Temporary since supplying SFTP credentials does not work yet. See #42184.
            if ( api.settings.theme._filesystemCredentialsNeeded ) {
                deferred.reject({
                    errorCode: 'theme_install_unavailable'
                });
                return deferred.promise();
            }

            // Prevent loading a non-active theme preview when there is a drafted/scheduled changeset.
            if ( ! panel.canSwitchTheme( slug ) ) {
                deferred.reject({
                    errorCode: 'theme_switch_unavailable'
                });
                return deferred.promise();
            }

            // Theme is already being installed.
            if ( _.contains( panel.installingThemes, slug ) ) {
                deferred.reject({
                    errorCode: 'theme_already_installing'
                });
                return deferred.promise();
            }

            wp.updates.maybeRequestFilesystemCredentials( event );

            onInstallSuccess = function( response ) {
                var theme = false, themeControl;
                if ( preview ) {
                    api.notifications.remove( 'theme_installing' );

                    panel.loadThemePreview( slug );

                } else {
                    api.control.each( function( control ) {
                        if ( 'theme' === control.params.type && control.params.theme.id === response.slug ) {
                            theme = control.params.theme; // Used below to add theme control.
                            control.rerenderAsInstalled( true );
                        }
                    });

                    // Don't add the same theme more than once.
                    if ( ! theme || api.control.has( 'installed_theme_' + theme.id ) ) {
                        deferred.resolve( response );
                        return;
                    }

                    // Add theme control to installed section.
                    theme.type = 'installed';
                    themeControl = new api.controlConstructor.theme( 'installed_theme_' + theme.id, {
                        type: 'theme',
                        section: 'installed_themes',
                        theme: theme,
                        priority: 0 // Add all newly-installed themes to the top.
                    } );

                    api.control.add( themeControl );
                    api.control( themeControl.id ).container.trigger( 'render-screenshot' );

                    // Close the details modal if it's open to the installed theme.
                    api.section.each( function( section ) {
                        if ( 'themes' === section.params.type ) {
                            if ( theme.id === section.currentTheme ) { // Don't close the modal if the user has navigated elsewhere.
                                section.closeDetails();
                            }
                        }
                    });
                }
                deferred.resolve( response );
            };

            panel.installingThemes.push( slug ); // Note: we don't remove elements from installingThemes, since they shouldn't be installed again.
            request = wp.updates.installTheme( {
                slug: slug
            } );

            // Also preview the theme as the event is triggered on Install & Preview.
            if ( preview ) {
                api.notifications.add( new api.OverlayNotification( 'theme_installing', {
                    message: api.l10n.themeDownloading,
                    type: 'info',
                    loading: true
                } ) );
            }

            request.done( onInstallSuccess );
            request.fail( function() {
                api.notifications.remove( 'theme_installing' );
            } );

            return deferred.promise();
        },

        /**
         * Load theme preview.
         *
         * @since 4.9.0
         *
         * @param {string} themeId Theme ID.
         * @return {jQuery.promise} Promise.
         */
        loadThemePreview: function( themeId ) {
            var panel = this, deferred = $.Deferred(), onceProcessingComplete, urlParser, queryParams;

            // Prevent loading a non-active theme preview when there is a drafted/scheduled changeset.
            if ( ! panel.canSwitchTheme( themeId ) ) {
                deferred.reject({
                    errorCode: 'theme_switch_unavailable'
                });
                return deferred.promise();
            }

            urlParser = document.createElement( 'a' );
            urlParser.href = location.href;
            queryParams = _.extend(
                api.utils.parseQueryString( urlParser.search.substr( 1 ) ),
                {
                    theme: themeId,
                    changeset_uuid: api.settings.changeset.uuid,
                    'return': api.settings.url['return']
                }
            );

            // Include autosaved param to load autosave revision without prompting user to restore it.
            if ( ! api.state( 'saved' ).get() ) {
                queryParams.customize_autosaved = 'on';
            }

            urlParser.search = $.param( queryParams );

            // Update loading message. Everything else is handled by reloading the page.
            api.notifications.add( new api.OverlayNotification( 'theme_previewing', {
                message: api.l10n.themePreviewWait,
                type: 'info',
                loading: true
            } ) );

            onceProcessingComplete = function() {
                var request;
                if ( api.state( 'processing' ).get() > 0 ) {
                    return;
                }

                api.state( 'processing' ).unbind( onceProcessingComplete );

                request = api.requestChangesetUpdate( {}, { autosave: true } );
                request.done( function() {
                    deferred.resolve();
                    $( window ).off( 'beforeunload.customize-confirm' );
                    location.replace( urlParser.href );
                } );
                request.fail( function() {

                    // @todo Show notification regarding failure.
                    api.notifications.remove( 'theme_previewing' );

                    deferred.reject();
                } );
            };

            if ( 0 === api.state( 'processing' ).get() ) {
                onceProcessingComplete();
            } else {
                api.state( 'processing' ).bind( onceProcessingComplete );
            }

            return deferred.promise();
        },

        /**
         * Update a theme via wp.updates.
         *
         * @since 4.9.0
         *
         * @param {jQuery.Event} event - Event.
         * @return {void}
         */
        updateTheme: function( event ) {
            wp.updates.maybeRequestFilesystemCredentials( event );

            $( document ).one( 'wp-theme-update-success', function( e, response ) {

                // Rerender the control to reflect the update.
                api.control.each( function( control ) {
                    if ( 'theme' === control.params.type && control.params.theme.id === response.slug ) {
                        control.params.theme.hasUpdate = false;
                        control.params.theme.version = response.newVersion;
                        setTimeout( function() {
                            control.rerenderAsInstalled( true );
                        }, 2000 );
                    }
                });
            } );

            wp.updates.updateTheme( {
                slug: $( event.target ).closest( '.notice' ).data( 'slug' )
            } );
        },

        /**
         * Delete a theme via wp.updates.
         *
         * @since 4.9.0
         *
         * @param {jQuery.Event} event - Event.
         * @return {void}
         */
        deleteTheme: function( event ) {
            var theme, section;
            theme = $( event.target ).data( 'slug' );
            section = api.section( 'installed_themes' );

            event.preventDefault();

            // Temporary since supplying SFTP credentials does not work yet. See #42184.
            if ( api.settings.theme._filesystemCredentialsNeeded ) {
                return;
            }

            // Confirmation dialog for deleting a theme.
            if ( ! window.confirm( api.settings.l10n.confirmDeleteTheme ) ) {
                return;
            }

            wp.updates.maybeRequestFilesystemCredentials( event );

            $( document ).one( 'wp-theme-delete-success', function() {
                var control = api.control( 'installed_theme_' + theme );

                // Remove theme control.
                control.container.remove();
                api.control.remove( control.id );

                // Update installed count.
                section.loaded = section.loaded - 1;
                section.updateCount();

                // Rerender any other theme controls as uninstalled.
                api.control.each( function( control ) {
                    if ( 'theme' === control.params.type && control.params.theme.id === theme ) {
                        control.rerenderAsInstalled( false );
                    }
                });
            } );

            wp.updates.deleteTheme( {
                slug: theme
            } );

            // Close modal and focus the section.
            section.closeDetails();
            section.focus();
        }
    });

    api.Control = api.Class.extend(/** @lends wp.customize.Control.prototype */{
        defaultActiveArguments: { duration: 'fast', completeCallback: $.noop },

        /**
         * Default params.
         *
         * @since 4.9.0
         * @var {object}
         */
        defaults: {
            label: '',
            description: '',
            active: true,
            priority: 10
        },

        /**
         * A Customizer Control.
         *
         * A control provides a UI element that allows a user to modify a Customizer Setting.
         *
         * @see PHP class WP_Customize_Control.
         *
         * @constructs wp.customize.Control
         * @augments   wp.customize.Class
         *
         * @borrows wp.customize~focus as this#focus
         * @borrows wp.customize~Container#activate as this#activate
         * @borrows wp.customize~Container#deactivate as this#deactivate
         * @borrows wp.customize~Container#_toggleActive as this#_toggleActive
         *
         * @param {string} id                       - Unique identifier for the control instance.
         * @param {Object} options                  - Options hash for the control instance.
         * @param {Object} options.type             - Type of control (e.g. text, radio, dropdown-pages, etc.)
         * @param {string} [options.content]        - The HTML content for the control or at least its container. This should normally be left blank and instead supplying a templateId.
         * @param {string} [options.templateId]     - Template ID for control's content.
         * @param {string} [options.priority=10]    - Order of priority to show the control within the section.
         * @param {string} [options.active=true]    - Whether the control is active.
         * @param {string} options.section          - The ID of the section the control belongs to.
         * @param {mixed}  [options.setting]        - The ID of the main setting or an instance of this setting.
         * @param {mixed}  options.settings         - An object with keys (e.g. default) that maps to setting IDs or Setting/Value objects, or an array of setting IDs or Setting/Value objects.
         * @param {mixed}  options.settings.default - The ID of the setting the control relates to.
         * @param {string} options.settings.data    - @todo Is this used?
         * @param {string} options.label            - Label.
         * @param {string} options.description      - Description.
         * @param {number} [options.instanceNumber] - Order in which this instance was created in relation to other instances.
         * @param {Object} [options.params]         - Deprecated wrapper for the above properties.
         * @return {void}
         */
        initialize: function( id, options ) {
            var control = this, deferredSettingIds = [], settings, gatherSettings;

            control.params = _.extend(
                {},
                control.defaults,
                control.params || {}, // In case subclass already defines.
                options.params || options || {} // The options.params property is deprecated, but it is checked first for back-compat.
            );

            if ( ! api.Control.instanceCounter ) {
                api.Control.instanceCounter = 0;
            }
            api.Control.instanceCounter++;
            if ( ! control.params.instanceNumber ) {
                control.params.instanceNumber = api.Control.instanceCounter;
            }

            // Look up the type if one was not supplied.
            if ( ! control.params.type ) {
                _.find( api.controlConstructor, function( Constructor, type ) {
                    if ( Constructor === control.constructor ) {
                        control.params.type = type;
                        return true;
                    }
                    return false;
                } );
            }

            if ( ! control.params.content ) {
                control.params.content = $( '<li></li>', {
                    id: 'customize-control-' + id.replace( /]/g, '' ).replace( /\[/g, '-' ),
                    'class': 'customize-control customize-control-' + control.params.type
                } );
            }

            control.id = id;
            control.selector = '#customize-control-' + id.replace( /\]/g, '' ).replace( /\[/g, '-' ); // Deprecated, likely dead code from time before #28709.
            if ( control.params.content ) {
                control.container = $( control.params.content );
            } else {
                control.container = $( control.selector ); // Likely dead, per above. See #28709.
            }

            if ( control.params.templateId ) {
                control.templateSelector = control.params.templateId;
            } else {
                control.templateSelector = 'customize-control-' + control.params.type + '-content';
            }

            control.deferred = _.extend( control.deferred || {}, {
                embedded: new $.Deferred()
            } );
            control.section = new api.Value();
            control.priority = new api.Value();
            control.active = new api.Value();
            control.activeArgumentsQueue = [];
            control.notifications = new api.Notifications({
                alt: control.altNotice
            });

            control.elements = [];

            control.active.bind( function ( active ) {
                var args = control.activeArgumentsQueue.shift();
                args = $.extend( {}, control.defaultActiveArguments, args );
                control.onChangeActive( active, args );
            } );

            control.section.set( control.params.section );
            control.priority.set( isNaN( control.params.priority ) ? 10 : control.params.priority );
            control.active.set( control.params.active );

            api.utils.bubbleChildValueChanges( control, [ 'section', 'priority', 'active' ] );

            control.settings = {};

            settings = {};
            if ( control.params.setting ) {
                settings['default'] = control.params.setting;
            }
            _.extend( settings, control.params.settings );

            // Note: Settings can be an array or an object, with values being either setting IDs or Setting (or Value) objects.
            _.each( settings, function( value, key ) {
                var setting;
                if ( _.isObject( value ) && _.isFunction( value.extended ) && value.extended( api.Value ) ) {
                    control.settings[ key ] = value;
                } else if ( _.isString( value ) ) {
                    setting = api( value );
                    if ( setting ) {
                        control.settings[ key ] = setting;
                    } else {
                        deferredSettingIds.push( value );
                    }
                }
            } );

            gatherSettings = function() {

                // Fill-in all resolved settings.
                _.each( settings, function ( settingId, key ) {
                    if ( ! control.settings[ key ] && _.isString( settingId ) ) {
                        control.settings[ key ] = api( settingId );
                    }
                } );

                // Make sure settings passed as array gets associated with default.
                if ( control.settings[0] && ! control.settings['default'] ) {
                    control.settings['default'] = control.settings[0];
                }

                // Identify the main setting.
                control.setting = control.settings['default'] || null;

                control.linkElements(); // Link initial elements present in server-rendered content.
                control.embed();
            };

            if ( 0 === deferredSettingIds.length ) {
                gatherSettings();
            } else {
                api.apply( api, deferredSettingIds.concat( gatherSettings ) );
            }

            // After the control is embedded on the page, invoke the "ready" method.
            control.deferred.embedded.done( function () {
                control.linkElements(); // Link any additional elements after template is rendered by renderContent().
                control.setupNotifications();
                control.ready();
            });
        },

        /**
         * Link elements between settings and inputs.
         *
         * @since 4.7.0
         * @access public
         *
         * @return {void}
         */
        linkElements: function () {
            var control = this, nodes, radios, element;

            nodes = control.container.find( '[data-customize-setting-link], [data-customize-setting-key-link]' );
            radios = {};

            nodes.each( function () {
                var node = $( this ), name, setting;

                if ( node.data( 'customizeSettingLinked' ) ) {
                    return;
                }
                node.data( 'customizeSettingLinked', true ); // Prevent re-linking element.

                if ( node.is( ':radio' ) ) {
                    name = node.prop( 'name' );
                    if ( radios[name] ) {
                        return;
                    }

                    radios[name] = true;
                    node = nodes.filter( '[name="' + name + '"]' );
                }

                // Let link by default refer to setting ID. If it doesn't exist, fallback to looking up by setting key.
                if ( node.data( 'customizeSettingLink' ) ) {
                    setting = api( node.data( 'customizeSettingLink' ) );
                } else if ( node.data( 'customizeSettingKeyLink' ) ) {
                    setting = control.settings[ node.data( 'customizeSettingKeyLink' ) ];
                }

                if ( setting ) {
                    element = new api.Element( node );
                    control.elements.push( element );
                    element.sync( setting );
                    element.set( setting() );
                }
            } );
        },

        /**
         * Embed the control into the page.
         */
        embed: function () {
            var control = this,
                inject;

            // Watch for changes to the section state.
            inject = function ( sectionId ) {
                var parentContainer;
                if ( ! sectionId ) { // @todo Allow a control to be embedded without a section, for instance a control embedded in the front end.
                    return;
                }
                // Wait for the section to be registered.
                api.section( sectionId, function ( section ) {
                    // Wait for the section to be ready/initialized.
                    section.deferred.embedded.done( function () {
                        parentContainer = ( section.contentContainer.is( 'ul' ) ) ? section.contentContainer : section.contentContainer.find( 'ul:first' );
                        if ( ! control.container.parent().is( parentContainer ) ) {
                            parentContainer.append( control.container );
                        }
                        control.renderContent();
                        control.deferred.embedded.resolve();
                    });
                });
            };
            control.section.bind( inject );
            inject( control.section.get() );
        },

        /**
         * Triggered when the control's markup has been injected into the DOM.
         *
         * @return {void}
         */
        ready: function() {
            var control = this, newItem;
            if ( 'dropdown-pages' === control.params.type && control.params.allow_addition ) {
                newItem = control.container.find( '.new-content-item' );
                newItem.hide(); // Hide in JS to preserve flex display when showing.
                control.container.on( 'click', '.add-new-toggle', function( e ) {
                    $( e.currentTarget ).slideUp( 180 );
                    newItem.slideDown( 180 );
                    newItem.find( '.create-item-input' ).focus();
                });
                control.container.on( 'click', '.add-content', function() {
                    control.addNewPage();
                });
                control.container.on( 'keydown', '.create-item-input', function( e ) {
                    if ( 13 === e.which ) { // Enter.
                        control.addNewPage();
                    }
                });
            }
        },

        /**
         * Get the element inside of a control's container that contains the validation error message.
         *
         * Control subclasses may override this to return the proper container to render notifications into.
         * Injects the notification container for existing controls that lack the necessary container,
         * including special handling for nav menu items and widgets.
         *
         * @since 4.6.0
         * @return {jQuery} Setting validation message element.
         */
        getNotificationsContainerElement: function() {
            var control = this, controlTitle, notificationsContainer;

            notificationsContainer = control.container.find( '.customize-control-notifications-container:first' );
            if ( notificationsContainer.length ) {
                return notificationsContainer;
            }

            notificationsContainer = $( '<div class="customize-control-notifications-container"></div>' );

            if ( control.container.hasClass( 'customize-control-nav_menu_item' ) ) {
                control.container.find( '.menu-item-settings:first' ).prepend( notificationsContainer );
            } else if ( control.container.hasClass( 'customize-control-widget_form' ) ) {
                control.container.find( '.widget-inside:first' ).prepend( notificationsContainer );
            } else {
                controlTitle = control.container.find( '.customize-control-title' );
                if ( controlTitle.length ) {
                    controlTitle.after( notificationsContainer );
                } else {
                    control.container.prepend( notificationsContainer );
                }
            }
            return notificationsContainer;
        },

        /**
         * Set up notifications.
         *
         * @since 4.9.0
         * @return {void}
         */
        setupNotifications: function() {
            var control = this, renderNotificationsIfVisible, onSectionAssigned;

            // Add setting notifications to the control notification.
            _.each( control.settings, function( setting ) {
                if ( ! setting.notifications ) {
                    return;
                }
                setting.notifications.bind( 'add', function( settingNotification ) {
                    var params = _.extend(
                        {},
                        settingNotification,
                        {
                            setting: setting.id
                        }
                    );
                    control.notifications.add( new api.Notification( setting.id + ':' + settingNotification.code, params ) );
                } );
                setting.notifications.bind( 'remove', function( settingNotification ) {
                    control.notifications.remove( setting.id + ':' + settingNotification.code );
                } );
            } );

            renderNotificationsIfVisible = function() {
                var sectionId = control.section();
                if ( ! sectionId || ( api.section.has( sectionId ) && api.section( sectionId ).expanded() ) ) {
                    control.notifications.render();
                }
            };

            control.notifications.bind( 'rendered', function() {
                var notifications = control.notifications.get();
                control.container.toggleClass( 'has-notifications', 0 !== notifications.length );
                control.container.toggleClass( 'has-error', 0 !== _.where( notifications, { type: 'error' } ).length );
            } );

            onSectionAssigned = function( newSectionId, oldSectionId ) {
                if ( oldSectionId && api.section.has( oldSectionId ) ) {
                    api.section( oldSectionId ).expanded.unbind( renderNotificationsIfVisible );
                }
                if ( newSectionId ) {
                    api.section( newSectionId, function( section ) {
                        section.expanded.bind( renderNotificationsIfVisible );
                        renderNotificationsIfVisible();
                    });
                }
            };

            control.section.bind( onSectionAssigned );
            onSectionAssigned( control.section.get() );
            control.notifications.bind( 'change', _.debounce( renderNotificationsIfVisible ) );
        },

        /**
         * Render notifications.
         *
         * Renders the `control.notifications` into the control's container.
         * Control subclasses may override this method to do their own handling
         * of rendering notifications.
         *
         * @deprecated in favor of `control.notifications.render()`
         * @since 4.6.0
         * @this {wp.customize.Control}
         */
        renderNotifications: function() {
            var control = this, container, notifications, hasError = false;

            if ( 'undefined' !== typeof console && console.warn ) {
                console.warn( '[DEPRECATED] wp.customize.Control.prototype.renderNotifications() is deprecated in favor of instantiating a wp.customize.Notifications and calling its render() method.' );
            }

            container = control.getNotificationsContainerElement();
            if ( ! container || ! container.length ) {
                return;
            }
            notifications = [];
            control.notifications.each( function( notification ) {
                notifications.push( notification );
                if ( 'error' === notification.type ) {
                    hasError = true;
                }
            } );

            if ( 0 === notifications.length ) {
                container.stop().slideUp( 'fast' );
            } else {
                container.stop().slideDown( 'fast', null, function() {
                    $( this ).css( 'height', 'auto' );
                } );
            }

            if ( ! control.notificationsTemplate ) {
                control.notificationsTemplate = wp.template( 'customize-control-notifications' );
            }

            control.container.toggleClass( 'has-notifications', 0 !== notifications.length );
            control.container.toggleClass( 'has-error', hasError );
            container.empty().append(
                control.notificationsTemplate( { notifications: notifications, altNotice: Boolean( control.altNotice ) } ).trim()
            );
        },

        /**
         * Normal controls do not expand, so just expand its parent
         *
         * @param {Object} [params]
         */
        expand: function ( params ) {
            api.section( this.section() ).expand( params );
        },

        /*
         * Documented using @borrows in the constructor.
         */
        focus: focus,

        /**
         * Update UI in response to a change in the control's active state.
         * This does not change the active state, it merely handles the behavior
         * for when it does change.
         *
         * @since 4.1.0
         *
         * @param {boolean}  active
         * @param {Object}   args
         * @param {number}   args.duration
         * @param {Function} args.completeCallback
         */
        onChangeActive: function ( active, args ) {
            if ( args.unchanged ) {
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
                return;
            }

            if ( ! $.contains( document, this.container[0] ) ) {
                // jQuery.fn.slideUp is not hiding an element if it is not in the DOM.
                this.container.toggle( active );
                if ( args.completeCallback ) {
                    args.completeCallback();
                }
            } else if ( active ) {
                this.container.slideDown( args.duration, args.completeCallback );
            } else {
                this.container.slideUp( args.duration, args.completeCallback );
            }
        },

        /**
         * @deprecated 4.1.0 Use this.onChangeActive() instead.
         */
        toggle: function ( active ) {
            return this.onChangeActive( active, this.defaultActiveArguments );
        },

        /*
         * Documented using @borrows in the constructor
         */
        activate: Container.prototype.activate,

        /*
         * Documented using @borrows in the constructor
         */
        deactivate: Container.prototype.deactivate,

        /*
         * Documented using @borrows in the constructor
         */
        _toggleActive: Container.prototype._toggleActive,

        // @todo This function appears to be dead code and can be removed.
        dropdownInit: function() {
            var control      = this,
                statuses     = this.container.find('.dropdown-status'),
                params       = this.params,
                toggleFreeze = false,
                update       = function( to ) {
                    if ( 'string' === typeof to && params.statuses && params.statuses[ to ] ) {
                        statuses.html( params.statuses[ to ] ).show();
                    } else {
                        statuses.hide();
                    }
                };

            // Support the .dropdown class to open/close complex elements.
            this.container.on( 'click keydown', '.dropdown', function( event ) {
                if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                    return;
                }

                event.preventDefault();

                if ( ! toggleFreeze ) {
                    control.container.toggleClass( 'open' );
                }

                if ( control.container.hasClass( 'open' ) ) {
                    control.container.parent().parent().find( 'li.library-selected' ).focus();
                }

                // Don't want to fire focus and click at same time.
                toggleFreeze = true;
                setTimeout(function () {
                    toggleFreeze = false;
                }, 400);
            });

            this.setting.bind( update );
            update( this.setting() );
        },

        /**
         * Render the control from its JS template, if it exists.
         *
         * The control's container must already exist in the DOM.
         *
         * @since 4.1.0
         */
        renderContent: function () {
            var control = this, template, standardTypes, templateId, sectionId;

            standardTypes = [
                'button',
                'checkbox',
                'date',
                'datetime-local',
                'email',
                'month',
                'number',
                'password',
                'radio',
                'range',
                'search',
                'select',
                'tel',
                'time',
                'text',
                'textarea',
                'week',
                'url'
            ];

            templateId = control.templateSelector;

            // Use default content template when a standard HTML type is used,
            // there isn't a more specific template existing, and the control container is empty.
            if ( templateId === 'customize-control-' + control.params.type + '-content' &&
                _.contains( standardTypes, control.params.type ) &&
                ! document.getElementById( 'tmpl-' + templateId ) &&
                0 === control.container.children().length )
            {
                templateId = 'customize-control-default-content';
            }

            // Replace the container element's content with the control.
            if ( document.getElementById( 'tmpl-' + templateId ) ) {
                template = wp.template( templateId );
                if ( template && control.container ) {
                    control.container.html( template( control.params ) );
                }
            }

            // Re-render notifications after content has been re-rendered.
            control.notifications.container = control.getNotificationsContainerElement();
            sectionId = control.section();
            if ( ! sectionId || ( api.section.has( sectionId ) && api.section( sectionId ).expanded() ) ) {
                control.notifications.render();
            }
        },

        /**
         * Add a new page to a dropdown-pages control reusing menus code for this.
         *
         * @since 4.7.0
         * @access private
         *
         * @return {void}
         */
        addNewPage: function () {
            var control = this, promise, toggle, container, input, title, select;

            if ( 'dropdown-pages' !== control.params.type || ! control.params.allow_addition || ! api.Menus ) {
                return;
            }

            toggle = control.container.find( '.add-new-toggle' );
            container = control.container.find( '.new-content-item' );
            input = control.container.find( '.create-item-input' );
            title = input.val();
            select = control.container.find( 'select' );

            if ( ! title ) {
                input.addClass( 'invalid' );
                return;
            }

            input.removeClass( 'invalid' );
            input.attr( 'disabled', 'disabled' );

            // The menus functions add the page, publish when appropriate,
            // and also add the new page to the dropdown-pages controls.
            promise = api.Menus.insertAutoDraftPost( {
                post_title: title,
                post_type: 'page'
            } );
            promise.done( function( data ) {
                var availableItem, $content, itemTemplate;

                // Prepare the new page as an available menu item.
                // See api.Menus.submitNew().
                availableItem = new api.Menus.AvailableItemModel( {
                    'id': 'post-' + data.post_id, // Used for available menu item Backbone models.
                    'title': title,
                    'type': 'post_type',
                    'type_label': api.Menus.data.l10n.page_label,
                    'object': 'page',
                    'object_id': data.post_id,
                    'url': data.url
                } );

                // Add the new item to the list of available menu items.
                api.Menus.availableMenuItemsPanel.collection.add( availableItem );
                $content = $( '#available-menu-items-post_type-page' ).find( '.available-menu-items-list' );
                itemTemplate = wp.template( 'available-menu-item' );
                $content.prepend( itemTemplate( availableItem.attributes ) );

                // Focus the select control.
                select.focus();
                control.setting.set( String( data.post_id ) ); // Triggers a preview refresh and updates the setting.

                // Reset the create page form.
                container.slideUp( 180 );
                toggle.slideDown( 180 );
            } );
            promise.always( function() {
                input.val( '' ).removeAttr( 'disabled' );
            } );
        }
    });

    /**
     * A colorpicker control.
     *
     * @class    wp.customize.ColorControl
     * @augments wp.customize.Control
     */
    api.ColorControl = api.Control.extend(/** @lends wp.customize.ColorControl.prototype */{
        ready: function() {
            var control = this,
                isHueSlider = this.params.mode === 'hue',
                updating = false,
                picker;

            if ( isHueSlider ) {
                picker = this.container.find( '.color-picker-hue' );
                picker.val( control.setting() ).wpColorPicker({
                    change: function( event, ui ) {
                        updating = true;
                        control.setting( ui.color.h() );
                        updating = false;
                    }
                });
            } else {
                picker = this.container.find( '.color-picker-hex' );
                picker.val( control.setting() ).wpColorPicker({
                    change: function() {
                        updating = true;
                        control.setting.set( picker.wpColorPicker( 'color' ) );
                        updating = false;
                    },
                    clear: function() {
                        updating = true;
                        control.setting.set( '' );
                        updating = false;
                    }
                });
            }

            control.setting.bind( function ( value ) {
                // Bail if the update came from the control itself.
                if ( updating ) {
                    return;
                }
                picker.val( value );
                picker.wpColorPicker( 'color', value );
            } );

            // Collapse color picker when hitting Esc instead of collapsing the current section.
            control.container.on( 'keydown', function( event ) {
                var pickerContainer;
                if ( 27 !== event.which ) { // Esc.
                    return;
                }
                pickerContainer = control.container.find( '.wp-picker-container' );
                if ( pickerContainer.hasClass( 'wp-picker-active' ) ) {
                    picker.wpColorPicker( 'close' );
                    control.container.find( '.wp-color-result' ).focus();
                    event.stopPropagation(); // Prevent section from being collapsed.
                }
            } );
        }
    });

    /**
     * A control that implements the media modal.
     *
     * @class    wp.customize.MediaControl
     * @augments wp.customize.Control
     */
    api.MediaControl = api.Control.extend(/** @lends wp.customize.MediaControl.prototype */{

        /**
         * When the control's DOM structure is ready,
         * set up internal event bindings.
         */
        ready: function() {
            var control = this;
            // Shortcut so that we don't have to use _.bind every time we add a callback.
            _.bindAll( control, 'restoreDefault', 'removeFile', 'openFrame', 'select', 'pausePlayer' );

            // Bind events, with delegation to facilitate re-rendering.
            control.container.on( 'click keydown', '.upload-button', control.openFrame );
            control.container.on( 'click keydown', '.upload-button', control.pausePlayer );
            control.container.on( 'click keydown', '.thumbnail-image img', control.openFrame );
            control.container.on( 'click keydown', '.default-button', control.restoreDefault );
            control.container.on( 'click keydown', '.remove-button', control.pausePlayer );
            control.container.on( 'click keydown', '.remove-button', control.removeFile );
            control.container.on( 'click keydown', '.remove-button', control.cleanupPlayer );

            // Resize the player controls when it becomes visible (ie when section is expanded).
            api.section( control.section() ).container
                .on( 'expanded', function() {
                    if ( control.player ) {
                        control.player.setControlsSize();
                    }
                })
                .on( 'collapsed', function() {
                    control.pausePlayer();
                });

            /**
             * Set attachment data and render content.
             *
             * Note that BackgroundImage.prototype.ready applies this ready method
             * to itself. Since BackgroundImage is an UploadControl, the value
             * is the attachment URL instead of the attachment ID. In this case
             * we skip fetching the attachment data because we have no ID available,
             * and it is the responsibility of the UploadControl to set the control's
             * attachmentData before calling the renderContent method.
             *
             * @param {number|string} value Attachment
             */
            function setAttachmentDataAndRenderContent( value ) {
                var hasAttachmentData = $.Deferred();

                if ( control.extended( api.UploadControl ) ) {
                    hasAttachmentData.resolve();
                } else {
                    value = parseInt( value, 10 );
                    if ( _.isNaN( value ) || value <= 0 ) {
                        delete control.params.attachment;
                        hasAttachmentData.resolve();
                    } else if ( control.params.attachment && control.params.attachment.id === value ) {
                        hasAttachmentData.resolve();
                    }
                }

                // Fetch the attachment data.
                if ( 'pending' === hasAttachmentData.state() ) {
                    wp.media.attachment( value ).fetch().done( function() {
                        control.params.attachment = this.attributes;
                        hasAttachmentData.resolve();

                        // Send attachment information to the preview for possible use in `postMessage` transport.
                        wp.customize.previewer.send( control.setting.id + '-attachment-data', this.attributes );
                    } );
                }

                hasAttachmentData.done( function() {
                    control.renderContent();
                } );
            }

            // Ensure attachment data is initially set (for dynamically-instantiated controls).
            setAttachmentDataAndRenderContent( control.setting() );

            // Update the attachment data and re-render the control when the setting changes.
            control.setting.bind( setAttachmentDataAndRenderContent );
        },

        pausePlayer: function () {
            this.player && this.player.pause();
        },

        cleanupPlayer: function () {
            this.player && wp.media.mixin.removePlayer( this.player );
        },

        /**
         * Open the media modal.
         */
        openFrame: function( event ) {
            if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                return;
            }

            event.preventDefault();

            if ( ! this.frame ) {
                this.initFrame();
            }

            this.frame.open();
        },

        /**
         * Create a media modal select frame, and store it so the instance can be reused when needed.
         */
        initFrame: function() {
            this.frame = wp.media({
                button: {
                    text: this.params.button_labels.frame_button
                },
                states: [
                    new wp.media.controller.Library({
                        title:     this.params.button_labels.frame_title,
                        library:   wp.media.query({ type: this.params.mime_type }),
                        multiple:  false,
                        date:      false
                    })
                ]
            });

            // When a file is selected, run a callback.
            this.frame.on( 'select', this.select );
        },

        /**
         * Callback handler for when an attachment is selected in the media modal.
         * Gets the selected image information, and sets it within the control.
         */
        select: function() {
            // Get the attachment from the modal frame.
            var node,
                attachment = this.frame.state().get( 'selection' ).first().toJSON(),
                mejsSettings = window._wpmejsSettings || {};

            this.params.attachment = attachment;

            // Set the Customizer setting; the callback takes care of rendering.
            this.setting( attachment.id );
            node = this.container.find( 'audio, video' ).get(0);

            // Initialize audio/video previews.
            if ( node ) {
                this.player = new MediaElementPlayer( node, mejsSettings );
            } else {
                this.cleanupPlayer();
            }
        },

        /**
         * Reset the setting to the default value.
         */
        restoreDefault: function( event ) {
            if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                return;
            }
            event.preventDefault();

            this.params.attachment = this.params.defaultAttachment;
            this.setting( this.params.defaultAttachment.url );
        },

        /**
         * Called when the "Remove" link is clicked. Empties the setting.
         *
         * @param {Object} event jQuery Event object
         */
        removeFile: function( event ) {
            if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                return;
            }
            event.preventDefault();

            this.params.attachment = {};
            this.setting( '' );
            this.renderContent(); // Not bound to setting change when emptying.
        }
    });

    /**
     * An upload control, which utilizes the media modal.
     *
     * @class    wp.customize.UploadControl
     * @augments wp.customize.MediaControl
     */
    api.UploadControl = api.MediaControl.extend(/** @lends wp.customize.UploadControl.prototype */{

        /**
         * Callback handler for when an attachment is selected in the media modal.
         * Gets the selected image information, and sets it within the control.
         */
        select: function() {
            // Get the attachment from the modal frame.
            var node,
                attachment = this.frame.state().get( 'selection' ).first().toJSON(),
                mejsSettings = window._wpmejsSettings || {};

            this.params.attachment = attachment;

            // Set the Customizer setting; the callback takes care of rendering.
            this.setting( attachment.url );
            node = this.container.find( 'audio, video' ).get(0);

            // Initialize audio/video previews.
            if ( node ) {
                this.player = new MediaElementPlayer( node, mejsSettings );
            } else {
                this.cleanupPlayer();
            }
        },

        // @deprecated
        success: function() {},

        // @deprecated
        removerVisibility: function() {}
    });

    /**
     * A control for uploading images.
     *
     * This control no longer needs to do anything more
     * than what the upload control does in JS.
     *
     * @class    wp.customize.ImageControl
     * @augments wp.customize.UploadControl
     */
    api.ImageControl = api.UploadControl.extend(/** @lends wp.customize.ImageControl.prototype */{
        // @deprecated
        thumbnailSrc: function() {}
    });

    /**
     * A control for uploading background images.
     *
     * @class    wp.customize.BackgroundControl
     * @augments wp.customize.UploadControl
     */
    api.BackgroundControl = api.UploadControl.extend(/** @lends wp.customize.BackgroundControl.prototype */{

        /**
         * When the control's DOM structure is ready,
         * set up internal event bindings.
         */
        ready: function() {
            api.UploadControl.prototype.ready.apply( this, arguments );
        },

        /**
         * Callback handler for when an attachment is selected in the media modal.
         * Does an additional Ajax request for setting the background context.
         */
        select: function() {
            api.UploadControl.prototype.select.apply( this, arguments );

            wp.ajax.post( 'custom-background-add', {
                nonce: _wpCustomizeBackground.nonces.add,
                wp_customize: 'on',
                customize_theme: api.settings.theme.stylesheet,
                attachment_id: this.params.attachment.id
            } );
        }
    });

    /**
     * A control for positioning a background image.
     *
     * @since 4.7.0
     *
     * @class    wp.customize.BackgroundPositionControl
     * @augments wp.customize.Control
     */
    api.BackgroundPositionControl = api.Control.extend(/** @lends wp.customize.BackgroundPositionControl.prototype */{

        /**
         * Set up control UI once embedded in DOM and settings are created.
         *
         * @since 4.7.0
         * @access public
         */
        ready: function() {
            var control = this, updateRadios;

            control.container.on( 'change', 'input[name="background-position"]', function() {
                var position = $( this ).val().split( ' ' );
                control.settings.x( position[0] );
                control.settings.y( position[1] );
            } );

            updateRadios = _.debounce( function() {
                var x, y, radioInput, inputValue;
                x = control.settings.x.get();
                y = control.settings.y.get();
                inputValue = String( x ) + ' ' + String( y );
                radioInput = control.container.find( 'input[name="background-position"][value="' + inputValue + '"]' );
                radioInput.trigger( 'click' );
            } );
            control.settings.x.bind( updateRadios );
            control.settings.y.bind( updateRadios );

            updateRadios(); // Set initial UI.
        }
    } );

    /**
     * A control for selecting and cropping an image.
     *
     * @class    wp.customize.CroppedImageControl
     * @augments wp.customize.MediaControl
     */
    api.CroppedImageControl = api.MediaControl.extend(/** @lends wp.customize.CroppedImageControl.prototype */{

        /**
         * Open the media modal to the library state.
         */
        openFrame: function( event ) {
            if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                return;
            }

            this.initFrame();
            this.frame.setState( 'library' ).open();
        },

        /**
         * Create a media modal select frame, and store it so the instance can be reused when needed.
         */
        initFrame: function() {
            var l10n = _wpMediaViewsL10n;

            this.frame = wp.media({
                button: {
                    text: l10n.select,
                    close: false
                },
                states: [
                    new wp.media.controller.Library({
                        title: this.params.button_labels.frame_title,
                        library: wp.media.query({ type: 'image' }),
                        multiple: false,
                        date: false,
                        priority: 20,
                        suggestedWidth: this.params.width,
                        suggestedHeight: this.params.height
                    }),
                    new wp.media.controller.CustomizeImageCropper({
                        imgSelectOptions: this.calculateImageSelectOptions,
                        control: this
                    })
                ]
            });

            this.frame.on( 'select', this.onSelect, this );
            this.frame.on( 'cropped', this.onCropped, this );
            this.frame.on( 'skippedcrop', this.onSkippedCrop, this );
        },

        /**
         * After an image is selected in the media modal, switch to the cropper
         * state if the image isn't the right size.
         */
        onSelect: function() {
            var attachment = this.frame.state().get( 'selection' ).first().toJSON();

            if ( this.params.width === attachment.width && this.params.height === attachment.height && ! this.params.flex_width && ! this.params.flex_height ) {
                this.setImageFromAttachment( attachment );
                this.frame.close();
            } else {
                this.frame.setState( 'cropper' );
            }
        },

        /**
         * After the image has been cropped, apply the cropped image data to the setting.
         *
         * @param {Object} croppedImage Cropped attachment data.
         */
        onCropped: function( croppedImage ) {
            this.setImageFromAttachment( croppedImage );
        },

        /**
         * Returns a set of options, computed from the attached image data and
         * control-specific data, to be fed to the imgAreaSelect plugin in
         * wp.media.view.Cropper.
         *
         * @param {wp.media.model.Attachment} attachment
         * @param {wp.media.controller.Cropper} controller
         * @return {Object} Options
         */
        calculateImageSelectOptions: function( attachment, controller ) {
            var control    = controller.get( 'control' ),
                flexWidth  = !! parseInt( control.params.flex_width, 10 ),
                flexHeight = !! parseInt( control.params.flex_height, 10 ),
                realWidth  = attachment.get( 'width' ),
                realHeight = attachment.get( 'height' ),
                xInit = parseInt( control.params.width, 10 ),
                yInit = parseInt( control.params.height, 10 ),
                ratio = xInit / yInit,
                xImg  = xInit,
                yImg  = yInit,
                x1, y1, imgSelectOptions;

            controller.set( 'canSkipCrop', ! control.mustBeCropped( flexWidth, flexHeight, xInit, yInit, realWidth, realHeight ) );

            if ( realWidth / realHeight > ratio ) {
                yInit = realHeight;
                xInit = yInit * ratio;
            } else {
                xInit = realWidth;
                yInit = xInit / ratio;
            }

            x1 = ( realWidth - xInit ) / 2;
            y1 = ( realHeight - yInit ) / 2;

            imgSelectOptions = {
                handles: true,
                keys: true,
                instance: true,
                persistent: true,
                imageWidth: realWidth,
                imageHeight: realHeight,
                minWidth: xImg > xInit ? xInit : xImg,
                minHeight: yImg > yInit ? yInit : yImg,
                x1: x1,
                y1: y1,
                x2: xInit + x1,
                y2: yInit + y1
            };

            if ( flexHeight === false && flexWidth === false ) {
                imgSelectOptions.aspectRatio = xInit + ':' + yInit;
            }

            if ( true === flexHeight ) {
                delete imgSelectOptions.minHeight;
                imgSelectOptions.maxWidth = realWidth;
            }

            if ( true === flexWidth ) {
                delete imgSelectOptions.minWidth;
                imgSelectOptions.maxHeight = realHeight;
            }

            return imgSelectOptions;
        },

        /**
         * Return whether the image must be cropped, based on required dimensions.
         *
         * @param {boolean} flexW
         * @param {boolean} flexH
         * @param {number}  dstW
         * @param {number}  dstH
         * @param {number}  imgW
         * @param {number}  imgH
         * @return {boolean}
         */
        mustBeCropped: function( flexW, flexH, dstW, dstH, imgW, imgH ) {
            if ( true === flexW && true === flexH ) {
                return false;
            }

            if ( true === flexW && dstH === imgH ) {
                return false;
            }

            if ( true === flexH && dstW === imgW ) {
                return false;
            }

            if ( dstW === imgW && dstH === imgH ) {
                return false;
            }

            if ( imgW <= dstW ) {
                return false;
            }

            return true;
        },

        /**
         * If cropping was skipped, apply the image data directly to the setting.
         */
        onSkippedCrop: function() {
            var attachment = this.frame.state().get( 'selection' ).first().toJSON();
            this.setImageFromAttachment( attachment );
        },

        /**
         * Updates the setting and re-renders the control UI.
         *
         * @param {Object} attachment
         */
        setImageFromAttachment: function( attachment ) {
            this.params.attachment = attachment;

            // Set the Customizer setting; the callback takes care of rendering.
            this.setting( attachment.id );
        }
    });

    /**
     * A control for selecting and cropping Site Icons.
     *
     * @class    wp.customize.SiteIconControl
     * @augments wp.customize.CroppedImageControl
     */
    api.SiteIconControl = api.CroppedImageControl.extend(/** @lends wp.customize.SiteIconControl.prototype */{

        /**
         * Create a media modal select frame, and store it so the instance can be reused when needed.
         */
        initFrame: function() {
            var l10n = _wpMediaViewsL10n;

            this.frame = wp.media({
                button: {
                    text: l10n.select,
                    close: false
                },
                states: [
                    new wp.media.controller.Library({
                        title: this.params.button_labels.frame_title,
                        library: wp.media.query({ type: 'image' }),
                        multiple: false,
                        date: false,
                        priority: 20,
                        suggestedWidth: this.params.width,
                        suggestedHeight: this.params.height
                    }),
                    new wp.media.controller.SiteIconCropper({
                        imgSelectOptions: this.calculateImageSelectOptions,
                        control: this
                    })
                ]
            });

            this.frame.on( 'select', this.onSelect, this );
            this.frame.on( 'cropped', this.onCropped, this );
            this.frame.on( 'skippedcrop', this.onSkippedCrop, this );
        },

        /**
         * After an image is selected in the media modal, switch to the cropper
         * state if the image isn't the right size.
         */
        onSelect: function() {
            var attachment = this.frame.state().get( 'selection' ).first().toJSON(),
                controller = this;

            if ( this.params.width === attachment.width && this.params.height === attachment.height && ! this.params.flex_width && ! this.params.flex_height ) {
                wp.ajax.post( 'crop-image', {
                    nonce: attachment.nonces.edit,
                    id: attachment.id,
                    context: 'site-icon',
                    cropDetails: {
                        x1: 0,
                        y1: 0,
                        width: this.params.width,
                        height: this.params.height,
                        dst_width: this.params.width,
                        dst_height: this.params.height
                    }
                } ).done( function( croppedImage ) {
                    controller.setImageFromAttachment( croppedImage );
                    controller.frame.close();
                } ).fail( function() {
                    controller.frame.trigger('content:error:crop');
                } );
            } else {
                this.frame.setState( 'cropper' );
            }
        },

        /**
         * Updates the setting and re-renders the control UI.
         *
         * @param {Object} attachment
         */
        setImageFromAttachment: function( attachment ) {
            var sizes = [ 'site_icon-32', 'thumbnail', 'full' ], link,
                icon;

            _.each( sizes, function( size ) {
                if ( ! icon && ! _.isUndefined ( attachment.sizes[ size ] ) ) {
                    icon = attachment.sizes[ size ];
                }
            } );

            this.params.attachment = attachment;

            // Set the Customizer setting; the callback takes care of rendering.
            this.setting( attachment.id );

            if ( ! icon ) {
                return;
            }

            // Update the icon in-browser.
            link = $( 'link[rel="icon"][sizes="32x32"]' );
            link.attr( 'href', icon.url );
        },

        /**
         * Called when the "Remove" link is clicked. Empties the setting.
         *
         * @param {Object} event jQuery Event object
         */
        removeFile: function( event ) {
            if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                return;
            }
            event.preventDefault();

            this.params.attachment = {};
            this.setting( '' );
            this.renderContent(); // Not bound to setting change when emptying.
            $( 'link[rel="icon"][sizes="32x32"]' ).attr( 'href', '/favicon.ico' ); // Set to default.
        }
    });

    /**
     * @class    wp.customize.HeaderControl
     * @augments wp.customize.Control
     */
    api.HeaderControl = api.Control.extend(/** @lends wp.customize.HeaderControl.prototype */{
        ready: function() {
            this.btnRemove = $('#customize-control-header_image .actions .remove');
            this.btnNew    = $('#customize-control-header_image .actions .new');

            _.bindAll(this, 'openMedia', 'removeImage');

            this.btnNew.on( 'click', this.openMedia );
            this.btnRemove.on( 'click', this.removeImage );

            api.HeaderTool.currentHeader = this.getInitialHeaderImage();

            new api.HeaderTool.CurrentView({
                model: api.HeaderTool.currentHeader,
                el: '#customize-control-header_image .current .container'
            });

            new api.HeaderTool.ChoiceListView({
                collection: api.HeaderTool.UploadsList = new api.HeaderTool.ChoiceList(),
                el: '#customize-control-header_image .choices .uploaded .list'
            });

            new api.HeaderTool.ChoiceListView({
                collection: api.HeaderTool.DefaultsList = new api.HeaderTool.DefaultsList(),
                el: '#customize-control-header_image .choices .default .list'
            });

            api.HeaderTool.combinedList = api.HeaderTool.CombinedList = new api.HeaderTool.CombinedList([
                api.HeaderTool.UploadsList,
                api.HeaderTool.DefaultsList
            ]);

            // Ensure custom-header-crop Ajax requests bootstrap the Customizer to activate the previewed theme.
            wp.media.controller.Cropper.prototype.defaults.doCropArgs.wp_customize = 'on';
            wp.media.controller.Cropper.prototype.defaults.doCropArgs.customize_theme = api.settings.theme.stylesheet;
        },

        /**
         * Returns a new instance of api.HeaderTool.ImageModel based on the currently
         * saved header image (if any).
         *
         * @since 4.2.0
         *
         * @return {Object} Options
         */
        getInitialHeaderImage: function() {
            if ( ! api.get().header_image || ! api.get().header_image_data || _.contains( [ 'remove-header', 'random-default-image', 'random-uploaded-image' ], api.get().header_image ) ) {
                return new api.HeaderTool.ImageModel();
            }

            // Get the matching uploaded image object.
            var currentHeaderObject = _.find( _wpCustomizeHeader.uploads, function( imageObj ) {
                return ( imageObj.attachment_id === api.get().header_image_data.attachment_id );
            } );
            // Fall back to raw current header image.
            if ( ! currentHeaderObject ) {
                currentHeaderObject = {
                    url: api.get().header_image,
                    thumbnail_url: api.get().header_image,
                    attachment_id: api.get().header_image_data.attachment_id
                };
            }

            return new api.HeaderTool.ImageModel({
                header: currentHeaderObject,
                choice: currentHeaderObject.url.split( '/' ).pop()
            });
        },

        /**
         * Returns a set of options, computed from the attached image data and
         * theme-specific data, to be fed to the imgAreaSelect plugin in
         * wp.media.view.Cropper.
         *
         * @param {wp.media.model.Attachment} attachment
         * @param {wp.media.controller.Cropper} controller
         * @return {Object} Options
         */
        calculateImageSelectOptions: function(attachment, controller) {
            var xInit = parseInt(_wpCustomizeHeader.data.width, 10),
                yInit = parseInt(_wpCustomizeHeader.data.height, 10),
                flexWidth = !! parseInt(_wpCustomizeHeader.data['flex-width'], 10),
                flexHeight = !! parseInt(_wpCustomizeHeader.data['flex-height'], 10),
                ratio, xImg, yImg, realHeight, realWidth,
                imgSelectOptions;

            realWidth = attachment.get('width');
            realHeight = attachment.get('height');

            this.headerImage = new api.HeaderTool.ImageModel();
            this.headerImage.set({
                themeWidth: xInit,
                themeHeight: yInit,
                themeFlexWidth: flexWidth,
                themeFlexHeight: flexHeight,
                imageWidth: realWidth,
                imageHeight: realHeight
            });

            controller.set( 'canSkipCrop', ! this.headerImage.shouldBeCropped() );

            ratio = xInit / yInit;
            xImg = realWidth;
            yImg = realHeight;

            if ( xImg / yImg > ratio ) {
                yInit = yImg;
                xInit = yInit * ratio;
            } else {
                xInit = xImg;
                yInit = xInit / ratio;
            }

            imgSelectOptions = {
                handles: true,
                keys: true,
                instance: true,
                persistent: true,
                imageWidth: realWidth,
                imageHeight: realHeight,
                x1: 0,
                y1: 0,
                x2: xInit,
                y2: yInit
            };

            if (flexHeight === false && flexWidth === false) {
                imgSelectOptions.aspectRatio = xInit + ':' + yInit;
            }
            if (flexHeight === false ) {
                imgSelectOptions.maxHeight = yInit;
            }
            if (flexWidth === false ) {
                imgSelectOptions.maxWidth = xInit;
            }

            return imgSelectOptions;
        },

        /**
         * Sets up and opens the Media Manager in order to select an image.
         * Depending on both the size of the image and the properties of the
         * current theme, a cropping step after selection may be required or
         * skippable.
         *
         * @param {event} event
         */
        openMedia: function(event) {
            var l10n = _wpMediaViewsL10n;

            event.preventDefault();

            this.frame = wp.media({
                button: {
                    text: l10n.selectAndCrop,
                    close: false
                },
                states: [
                    new wp.media.controller.Library({
                        title:     l10n.chooseImage,
                        library:   wp.media.query({ type: 'image' }),
                        multiple:  false,
                        date:      false,
                        priority:  20,
                        suggestedWidth: _wpCustomizeHeader.data.width,
                        suggestedHeight: _wpCustomizeHeader.data.height
                    }),
                    new wp.media.controller.Cropper({
                        imgSelectOptions: this.calculateImageSelectOptions
                    })
                ]
            });

            this.frame.on('select', this.onSelect, this);
            this.frame.on('cropped', this.onCropped, this);
            this.frame.on('skippedcrop', this.onSkippedCrop, this);

            this.frame.open();
        },

        /**
         * After an image is selected in the media modal,
         * switch to the cropper state.
         */
        onSelect: function() {
            this.frame.setState('cropper');
        },

        /**
         * After the image has been cropped, apply the cropped image data to the setting.
         *
         * @param {Object} croppedImage Cropped attachment data.
         */
        onCropped: function(croppedImage) {
            var url = croppedImage.url,
                attachmentId = croppedImage.attachment_id,
                w = croppedImage.width,
                h = croppedImage.height;
            this.setImageFromURL(url, attachmentId, w, h);
        },

        /**
         * If cropping was skipped, apply the image data directly to the setting.
         *
         * @param {Object} selection
         */
        onSkippedCrop: function(selection) {
            var url = selection.get('url'),
                w = selection.get('width'),
                h = selection.get('height');
            this.setImageFromURL(url, selection.id, w, h);
        },

        /**
         * Creates a new wp.customize.HeaderTool.ImageModel from provided
         * header image data and inserts it into the user-uploaded headers
         * collection.
         *
         * @param {string} url
         * @param {number} attachmentId
         * @param {number} width
         * @param {number} height
         */
        setImageFromURL: function(url, attachmentId, width, height) {
            var choice, data = {};

            data.url = url;
            data.thumbnail_url = url;
            data.timestamp = _.now();

            if (attachmentId) {
                data.attachment_id = attachmentId;
            }

            if (width) {
                data.width = width;
            }

            if (height) {
                data.height = height;
            }

            choice = new api.HeaderTool.ImageModel({
                header: data,
                choice: url.split('/').pop()
            });
            api.HeaderTool.UploadsList.add(choice);
            api.HeaderTool.currentHeader.set(choice.toJSON());
            choice.save();
            choice.importImage();
        },

        /**
         * Triggers the necessary events to deselect an image which was set as
         * the currently selected one.
         */
        removeImage: function() {
            api.HeaderTool.currentHeader.trigger('hide');
            api.HeaderTool.CombinedList.trigger('control:removeImage');
        }

    });

    /**
     * wp.customize.ThemeControl
     *
     * @class    wp.customize.ThemeControl
     * @augments wp.customize.Control
     */
    api.ThemeControl = api.Control.extend(/** @lends wp.customize.ThemeControl.prototype */{

        touchDrag: false,
        screenshotRendered: false,

        /**
         * @since 4.2.0
         */
        ready: function() {
            var control = this, panel = api.panel( 'themes' );

            function disableSwitchButtons() {
                return ! panel.canSwitchTheme( control.params.theme.id );
            }

            // Temporary special function since supplying SFTP credentials does not work yet. See #42184.
            function disableInstallButtons() {
                return disableSwitchButtons() || false === api.settings.theme._canInstall || true === api.settings.theme._filesystemCredentialsNeeded;
            }
            function updateButtons() {
                control.container.find( 'button.preview, button.preview-theme' ).toggleClass( 'disabled', disableSwitchButtons() );
                control.container.find( 'button.theme-install' ).toggleClass( 'disabled', disableInstallButtons() );
            }

            api.state( 'selectedChangesetStatus' ).bind( updateButtons );
            api.state( 'changesetStatus' ).bind( updateButtons );
            updateButtons();

            control.container.on( 'touchmove', '.theme', function() {
                control.touchDrag = true;
            });

            // Bind details view trigger.
            control.container.on( 'click keydown touchend', '.theme', function( event ) {
                var section;
                if ( api.utils.isKeydownButNotEnterEvent( event ) ) {
                    return;
                }

                // Bail if the user scrolled on a touch device.
                if ( control.touchDrag === true ) {
                    return control.touchDrag = false;
                }

                // Prevent the modal from showing when the user clicks the action button.
                if ( $( event.target ).is( '.theme-actions .button, .update-theme' ) ) {
                    return;
                }

                event.preventDefault(); // Keep this AFTER the key filter above.
                section = api.section( control.section() );
                section.showDetails( control.params.theme, function() {

                    // Temporary special function since supplying SFTP credentials does not work yet. See #42184.
                    if ( api.settings.theme._filesystemCredentialsNeeded ) {
                        section.overlay.find( '.theme-actions .delete-theme' ).remove();
                    }
                } );
            });

            control.container.on( 'render-screenshot', function() {
                var $screenshot = $( this ).find( 'img' ),
                    source = $screenshot.data( 'src' );

                if ( source ) {
                    $screenshot.attr( 'src', source );
                }
                control.screenshotRendered = true;
            });
        },

        /**
         * Show or hide the theme based on the presence of the term in the title, description, tags, and author.
         *
         * @since 4.2.0
         * @param {Array} terms - An array of terms to search for.
         * @return {boolean} Whether a theme control was activated or not.
         */
        filter: function( terms ) {
            var control = this,
                matchCount = 0,
                haystack = control.params.theme.name + ' ' +
                    control.params.theme.description + ' ' +
                    control.params.theme.tags + ' ' +
                    control.params.theme.author + ' ';
            haystack = haystack.toLowerCase().replace( '-', ' ' );

            // Back-compat for behavior in WordPress 4.2.0 to 4.8.X.
            if ( ! _.isArray( terms ) ) {
                terms = [ terms ];
            }

            // Always give exact name matches highest ranking.
            if ( control.params.theme.name.toLowerCase() === terms.join( ' ' ) ) {
                matchCount = 100;
            } else {

                // Search for and weight (by 10) complete term matches.
                matchCount = matchCount + 10 * ( haystack.split( terms.join( ' ' ) ).length - 1 );

                // Search for each term individually (as whole-word and partial match) and sum weighted match counts.
                _.each( terms, function( term ) {
                    matchCount = matchCount + 2 * ( haystack.split( term + ' ' ).length - 1 ); // Whole-word, double-weighted.
                    matchCount = matchCount + haystack.split( term ).length - 1; // Partial word, to minimize empty intermediate searches while typing.
                });

                // Upper limit on match ranking.
                if ( matchCount > 99 ) {
                    matchCount = 99;
                }
            }

            if ( 0 !== matchCount ) {
                control.activate();
                control.params.priority = 101 - matchCount; // Sort results by match count.
                return true;
            } else {
                control.deactivate(); // Hide control.
                control.params.priority = 101;
                return false;
            }
        },

        /**
         * Rerender the theme from its JS template with the installed type.
         *
         * @since 4.9.0
         *
         * @return {void}
         */
        rerenderAsInstalled: function( installed ) {
            var control = this, section;
            if ( installed ) {
                control.params.theme.type = 'installed';
            } else {
                section = api.section( control.params.section );
                control.params.theme.type = section.params.action;
            }
            control.renderContent(); // Replaces existing content.
            control.container.trigger( 'render-screenshot' );
        }
    });

    /**
     * Class wp.customize.CodeEditorControl
     *
     * @since 4.9.0
     *
     * @class    wp.customize.CodeEditorControl
     * @augments wp.customize.Control
     */
    api.CodeEditorControl = api.Control.extend(/** @lends wp.customize.CodeEditorControl.prototype */{

        /**
         * Initialize.
         *
         * @since 4.9.0
         * @param {string} id      - Unique identifier for the control instance.
         * @param {Object} options - Options hash for the control instance.
         * @return {void}
         */
        initialize: function( id, options ) {
            var control = this;
            control.deferred = _.extend( control.deferred || {}, {
                codemirror: $.Deferred()
            } );
            api.Control.prototype.initialize.call( control, id, options );

            // Note that rendering is debounced so the props will be used when rendering happens after add event.
            control.notifications.bind( 'add', function( notification ) {

                // Skip if control notification is not from setting csslint_error notification.
                if ( notification.code !== control.setting.id + ':csslint_error' ) {
                    return;
                }

                // Customize the template and behavior of csslint_error notifications.
                notification.templateId = 'customize-code-editor-lint-error-notification';
                notification.render = (function( render ) {
                    return function() {
                        var li = render.call( this );
                        li.find( 'input[type=checkbox]' ).on( 'click', function() {
                            control.setting.notifications.remove( 'csslint_error' );
                        } );
                        return li;
                    };
                })( notification.render );
            } );
        },

        /**
         * Initialize the editor when the containing section is ready and expanded.
         *
         * @since 4.9.0
         * @return {void}
         */
        ready: function() {
            var control = this;
            if ( ! control.section() ) {
                control.initEditor();
                return;
            }

            // Wait to initialize editor until section is embedded and expanded.
            api.section( control.section(), function( section ) {
                section.deferred.embedded.done( function() {
                    var onceExpanded;
                    if ( section.expanded() ) {
                        control.initEditor();
                    } else {
                        onceExpanded = function( isExpanded ) {
                            if ( isExpanded ) {
                                control.initEditor();
                                section.expanded.unbind( onceExpanded );
                            }
                        };
                        section.expanded.bind( onceExpanded );
                    }
                } );
            } );
        },

        /**
         * Initialize editor.
         *
         * @since 4.9.0
         * @return {void}
         */
        initEditor: function() {
            var control = this, element, editorSettings = false;

            // Obtain editorSettings for instantiation.
            if ( wp.codeEditor && ( _.isUndefined( control.params.editor_settings ) || false !== control.params.editor_settings ) ) {

                // Obtain default editor settings.
                editorSettings = wp.codeEditor.defaultSettings ? _.clone( wp.codeEditor.defaultSettings ) : {};
                editorSettings.codemirror = _.extend(
                    {},
                    editorSettings.codemirror,
                    {
                        indentUnit: 2,
                        tabSize: 2
                    }
                );

                // Merge editor_settings param on top of defaults.
                if ( _.isObject( control.params.editor_settings ) ) {
                    _.each( control.params.editor_settings, function( value, key ) {
                        if ( _.isObject( value ) ) {
                            editorSettings[ key ] = _.extend(
                                {},
                                editorSettings[ key ],
                                value
                            );
                        }
                    } );
                }
            }

            element = new api.Element( control.container.find( 'textarea' ) );
            control.elements.push( element );
            element.sync( control.setting );
            element.set( control.setting() );

            if ( editorSettings ) {
                control.initSyntaxHighlightingEditor( editorSettings );
            } else {
                control.initPlainTextareaEditor();
            }
        },

        /**
         * Make sure editor gets focused when control is focused.
         *
         * @since 4.9.0
         * @param {Object}   [params] - Focus params.
         * @param {Function} [params.completeCallback] - Function to call when expansion is complete.
         * @return {void}
         */
        focus: function( params ) {
            var control = this, extendedParams = _.extend( {}, params ), originalCompleteCallback;
            originalCompleteCallback = extendedParams.completeCallback;
            extendedParams.completeCallback = function() {
                if ( originalCompleteCallback ) {
                    originalCompleteCallback();
                }
                if ( control.editor ) {
                    control.editor.codemirror.focus();
                }
            };
            api.Control.prototype.focus.call( control, extendedParams );
        },

        /**
         * Initialize syntax-highlighting editor.
         *
         * @since 4.9.0
         * @param {Object} codeEditorSettings - Code editor settings.
         * @return {void}
         */
        initSyntaxHighlightingEditor: function( codeEditorSettings ) {
            var control = this, $textarea = control.container.find( 'textarea' ), settings, suspendEditorUpdate = false;

            settings = _.extend( {}, codeEditorSettings, {
                onTabNext: _.bind( control.onTabNext, control ),
                onTabPrevious: _.bind( control.onTabPrevious, control ),
                onUpdateErrorNotice: _.bind( control.onUpdateErrorNotice, control )
            });

            control.editor = wp.codeEditor.initialize( $textarea, settings );

            // Improve the editor accessibility.
            $( control.editor.codemirror.display.lineDiv )
                .attr({
                    role: 'textbox',
                    'aria-multiline': 'true',
                    'aria-label': control.params.label,
                    'aria-describedby': 'editor-keyboard-trap-help-1 editor-keyboard-trap-help-2 editor-keyboard-trap-help-3 editor-keyboard-trap-help-4'
                });

            // Focus the editor when clicking on its label.
            control.container.find( 'label' ).on( 'click', function() {
                control.editor.codemirror.focus();
            });

            /*
             * When the CodeMirror instance changes, mirror to the textarea,
             * where we have our "true" change event handler bound.
             */
            control.editor.codemirror.on( 'change', function( codemirror ) {
                suspendEditorUpdate = true;
                $textarea.val( codemirror.getValue() ).trigger( 'change' );
                suspendEditorUpdate = false;
            });

            // Update CodeMirror when the setting is changed by another plugin.
            control.setting.bind( function( value ) {
                if ( ! suspendEditorUpdate ) {
                    control.editor.codemirror.setValue( value );
                }
            });

            // Prevent collapsing section when hitting Esc to tab out of editor.
            control.editor.codemirror.on( 'keydown', function onKeydown( codemirror, event ) {
                var escKeyCode = 27;
                if ( escKeyCode === event.keyCode ) {
                    event.stopPropagation();
                }
            });

            control.deferred.codemirror.resolveWith( control, [ control.editor.codemirror ] );
        },

        /**
         * Handle tabbing to the field after the editor.
         *
         * @since 4.9.0
         * @return {void}
         */
        onTabNext: function onTabNext() {
            var control = this, controls, controlIndex, section;
            section = api.section( control.section() );
            controls = section.controls();
            controlIndex = controls.indexOf( control );
            if ( controls.length === controlIndex + 1 ) {
                $( '#customize-footer-actions .collapse-sidebar' ).trigger( 'focus' );
            } else {
                controls[ controlIndex + 1 ].container.find( ':focusable:first' ).focus();
            }
        },

        /**
         * Handle tabbing to the field before the editor.
         *
         * @since 4.9.0
         * @return {void}
         */
        onTabPrevious: function onTabPrevious() {
            var control = this, controls, controlIndex, section;
            section = api.section( control.section() );
            controls = section.controls();
            controlIndex = controls.indexOf( control );
            if ( 0 === controlIndex ) {
                section.contentContainer.find( '.customize-section-title .customize-help-toggle, .customize-section-title .customize-section-description.open .section-description-close' ).last().focus();
            } else {
                controls[ controlIndex - 1 ].contentContainer.find( ':focusable:first' ).focus();
            }
        },

        /**
         * Update error notice.
         *
         * @since 4.9.0
         * @param {Array} errorAnnotations - Error annotations.
         * @return {void}
         */
        onUpdateErrorNotice: function onUpdateErrorNotice( errorAnnotations ) {
            var control = this, message;
            control.setting.notifications.remove( 'csslint_error' );

            if ( 0 !== errorAnnotations.length ) {
                if ( 1 === errorAnnotations.length ) {
                    message = api.l10n.customCssError.singular.replace( '%d', '1' );
                } else {
                    message = api.l10n.customCssError.plural.replace( '%d', String( errorAnnotations.length ) );
                }
                control.setting.notifications.add( new api.Notification( 'csslint_error', {
                    message: message,
                    type: 'error'
                } ) );
            }
        },

        /**
         * Initialize plain-textarea editor when syntax highlighting is disabled.
         *
         * @since 4.9.0
         * @return {void}
         */
        initPlainTextareaEditor: function() {
            var control = this, $textarea = control.container.find( 'textarea' ), textarea = $textarea[0];

            $textarea.on( 'blur', function onBlur() {
                $textarea.data( 'next-tab-blurs', false );
            } );

            $textarea.on( 'keydown', function onKeydown( event ) {
                var selectionStart, selectionEnd, value, tabKeyCode = 9, escKeyCode = 27;

                if ( escKeyCode === event.keyCode ) {
                    if ( ! $textarea.data( 'next-tab-blurs' ) ) {
                        $textarea.data( 'next-tab-blurs', true );
                        event.stopPropagation(); // Prevent collapsing the section.
                    }
                    return;
                }

                // Short-circuit if tab key is not being pressed or if a modifier key *is* being pressed.
                if ( tabKeyCode !== event.keyCode || event.ctrlKey || event.altKey || event.shiftKey ) {
                    return;
                }

                // Prevent capturing Tab characters if Esc was pressed.
                if ( $textarea.data( 'next-tab-blurs' ) ) {
                    return;
                }

                selectionStart = textarea.selectionStart;
                selectionEnd = textarea.selectionEnd;
                value = textarea.value;

                if ( selectionStart >= 0 ) {
                    textarea.value = value.substring( 0, selectionStart ).concat( '\t', value.substring( selectionEnd ) );
                    $textarea.selectionStart = textarea.selectionEnd = selectionStart + 1;
                }

                event.stopPropagation();
                event.preventDefault();
            });

            control.deferred.codemirror.rejectWith( control );
        }
    });

    /**
     * Class wp.customize.DateTimeControl.
     *
     * @since 4.9.0
     * @class    wp.customize.DateTimeControl
     * @augments wp.customize.Control
     */
    api.DateTimeControl = api.Control.extend(/** @lends wp.customize.DateTimeControl.prototype */{

        /**
         * Initialize behaviors.
         *
         * @since 4.9.0
         * @return {void}
         */
        ready: function ready() {
            var control = this;

            control.inputElements = {};
            control.invalidDate = false;

            _.bindAll( control, 'populateSetting', 'updateDaysForMonth', 'populateDateInputs' );

            if ( ! control.setting ) {
                throw new Error( 'Missing setting' );
            }

            control.container.find( '.date-input' ).each( function() {
                var input = $( this ), component, element;
                component = input.data( 'component' );
                element = new api.Element( input );
                control.inputElements[ component ] = element;
                control.elements.push( element );

                // Add invalid date error once user changes (and has blurred the input).
                input.on( 'change', function() {
                    if ( control.invalidDate ) {
                        control.notifications.add( new api.Notification( 'invalid_date', {
                            message: api.l10n.invalidDate
                        } ) );
                    }
                } );

                // Remove the error immediately after validity change.
                input.on( 'input', _.debounce( function() {
                    if ( ! control.invalidDate ) {
                        control.notifications.remove( 'invalid_date' );
                    }
                } ) );

                // Add zero-padding when blurring field.
                input.on( 'blur', _.debounce( function() {
                    if ( ! control.invalidDate ) {
                        control.populateDateInputs();
                    }
                } ) );
            } );

            control.inputElements.month.bind( control.updateDaysForMonth );
            control.inputElements.year.bind( control.updateDaysForMonth );
            control.populateDateInputs();
            control.setting.bind( control.populateDateInputs );

            // Start populating setting after inputs have been populated.
            _.each( control.inputElements, function( element ) {
                element.bind( control.populateSetting );
            } );
        },

        /**
         * Parse datetime string.
         *
         * @since 4.9.0
         *
         * @param {string} datetime - Date/Time string. Accepts Y-m-d[ H:i[:s]] format.
         * @return {Object|null} Returns object containing date components or null if parse error.
         */
        parseDateTime: function parseDateTime( datetime ) {
            var control = this, matches, date, midDayHour = 12;

            if ( datetime ) {
                matches = datetime.match( /^(\d\d\d\d)-(\d\d)-(\d\d)(?: (\d\d):(\d\d)(?::(\d\d))?)?$/ );
            }

            if ( ! matches ) {
                return null;
            }

            matches.shift();

            date = {
                year: matches.shift(),
                month: matches.shift(),
                day: matches.shift(),
                hour: matches.shift() || '00',
                minute: matches.shift() || '00',
                second: matches.shift() || '00'
            };

            if ( control.params.includeTime && control.params.twelveHourFormat ) {
                date.hour = parseInt( date.hour, 10 );
                date.meridian = date.hour >= midDayHour ? 'pm' : 'am';
                date.hour = date.hour % midDayHour ? String( date.hour % midDayHour ) : String( midDayHour );
                delete date.second; // @todo Why only if twelveHourFormat?
            }

            return date;
        },

        /**
         * Validates if input components have valid date and time.
         *
         * @since 4.9.0
         * @return {boolean} If date input fields has error.
         */
        validateInputs: function validateInputs() {
            var control = this, components, validityInput;

            control.invalidDate = false;

            components = [ 'year', 'day' ];
            if ( control.params.includeTime ) {
                components.push( 'hour', 'minute' );
            }

            _.find( components, function( component ) {
                var element, max, min, value;

                element = control.inputElements[ component ];
                validityInput = element.element.get( 0 );
                max = parseInt( element.element.attr( 'max' ), 10 );
                min = parseInt( element.element.attr( 'min' ), 10 );
                value = parseInt( element(), 10 );
                control.invalidDate = isNaN( value ) || value > max || value < min;

                if ( ! control.invalidDate ) {
                    validityInput.setCustomValidity( '' );
                }

                return control.invalidDate;
            } );

            if ( control.inputElements.meridian && ! control.invalidDate ) {
                validityInput = control.inputElements.meridian.element.get( 0 );
                if ( 'am' !== control.inputElements.meridian.get() && 'pm' !== control.inputElements.meridian.get() ) {
                    control.invalidDate = true;
                } else {
                    validityInput.setCustomValidity( '' );
                }
            }

            if ( control.invalidDate ) {
                validityInput.setCustomValidity( api.l10n.invalidValue );
            } else {
                validityInput.setCustomValidity( '' );
            }
            if ( ! control.section() || api.section.has( control.section() ) && api.section( control.section() ).expanded() ) {
                _.result( validityInput, 'reportValidity' );
            }

            return control.invalidDate;
        },

        /**
         * Updates number of days according to the month and year selected.
         *
         * @since 4.9.0
         * @return {void}
         */
        updateDaysForMonth: function updateDaysForMonth() {
            var control = this, daysInMonth, year, month, day;

            month = parseInt( control.inputElements.month(), 10 );
            year = parseInt( control.inputElements.year(), 10 );
            day = parseInt( control.inputElements.day(), 10 );

            if ( month && year ) {
                daysInMonth = new Date( year, month, 0 ).getDate();
                control.inputElements.day.element.attr( 'max', daysInMonth );

                if ( day > daysInMonth ) {
                    control.inputElements.day( String( daysInMonth ) );
                }
            }
        },

        /**
         * Populate setting value from the inputs.
         *
         * @since 4.9.0
         * @return {boolean} If setting updated.
         */
        populateSetting: function populateSetting() {
            var control = this, date;

            if ( control.validateInputs() || ! control.params.allowPastDate && ! control.isFutureDate() ) {
                return false;
            }

            date = control.convertInputDateToString();
            control.setting.set( date );
            return true;
        },

        /**
         * Converts input values to string in Y-m-d H:i:s format.
         *
         * @since 4.9.0
         * @return {string} Date string.
         */
        convertInputDateToString: function convertInputDateToString() {
            var control = this, date = '', dateFormat, hourInTwentyFourHourFormat,
                getElementValue, pad;

            pad = function( number, padding ) {
                var zeros;
                if ( String( number ).length < padding ) {
                    zeros = padding - String( number ).length;
                    number = Math.pow( 10, zeros ).toString().substr( 1 ) + String( number );
                }
                return number;
            };

            getElementValue = function( component ) {
                var value = parseInt( control.inputElements[ component ].get(), 10 );

                if ( _.contains( [ 'month', 'day', 'hour', 'minute' ], component ) ) {
                    value = pad( value, 2 );
                } else if ( 'year' === component ) {
                    value = pad( value, 4 );
                }
                return value;
            };

            dateFormat = [ 'year', '-', 'month', '-', 'day' ];
            if ( control.params.includeTime ) {
                hourInTwentyFourHourFormat = control.inputElements.meridian ? control.convertHourToTwentyFourHourFormat( control.inputElements.hour(), control.inputElements.meridian() ) : control.inputElements.hour();
                dateFormat = dateFormat.concat( [ ' ', pad( hourInTwentyFourHourFormat, 2 ), ':', 'minute', ':', '00' ] );
            }

            _.each( dateFormat, function( component ) {
                date += control.inputElements[ component ] ? getElementValue( component ) : component;
            } );

            return date;
        },

        /**
         * Check if the date is in the future.
         *
         * @since 4.9.0
         * @return {boolean} True if future date.
         */
        isFutureDate: function isFutureDate() {
            var control = this;
            return 0 < api.utils.getRemainingTime( control.convertInputDateToString() );
        },

        /**
         * Convert hour in twelve hour format to twenty four hour format.
         *
         * @since 4.9.0
         * @param {string} hourInTwelveHourFormat - Hour in twelve hour format.
         * @param {string} meridian - Either 'am' or 'pm'.
         * @return {string} Hour in twenty four hour format.
         */
        convertHourToTwentyFourHourFormat: function convertHour( hourInTwelveHourFormat, meridian ) {
            var hourInTwentyFourHourFormat, hour, midDayHour = 12;

            hour = parseInt( hourInTwelveHourFormat, 10 );
            if ( isNaN( hour ) ) {
                return '';
            }

            if ( 'pm' === meridian && hour < midDayHour ) {
                hourInTwentyFourHourFormat = hour + midDayHour;
            } else if ( 'am' === meridian && midDayHour === hour ) {
                hourInTwentyFourHourFormat = hour - midDayHour;
            } else {
                hourInTwentyFourHourFormat = hour;
            }

            return String( hourInTwentyFourHourFormat );
        },

        /**
         * Populates date inputs in date fields.
         *
         * @since 4.9.0
         * @return {boolean} Whether the inputs were populated.
         */
        populateDateInputs: function populateDateInputs() {
            var control = this, parsed;

            parsed = control.parseDateTime( control.setting.get() );

            if ( ! parsed ) {
                return false;
            }

            _.each( control.inputElements, function( element, component ) {
                var value = parsed[ component ]; // This will be zero-padded string.

                // Set month and meridian regardless of focused state since they are dropdowns.
                if ( 'month' === component || 'meridian' === component ) {

                    // Options in dropdowns are not zero-padded.
                    value = value.replace( /^0/, '' );

                    element.set( value );
                } else {

                    value = parseInt( value, 10 );
                    if ( ! element.element.is( document.activeElement ) ) {

                        // Populate element with zero-padded value if not focused.
                        element.set( parsed[ component ] );
                    } else if ( value !== parseInt( element(), 10 ) ) {

                        // Forcibly update the value if its underlying value changed, regardless of zero-padding.
                        element.set( String( value ) );
                    }
                }
            } );

            return true;
        },

        /**
         * Toggle future date notification for date control.
         *
         * @since 4.9.0
         * @param {boolean} notify Add or remove the notification.
         * @return {wp.customize.DateTimeControl}
         */
        toggleFutureDateNotification: function toggleFutureDateNotification( notify ) {
            var control = this, notificationCode, notification;

            notificationCode = 'not_future_date';

            if ( notify ) {
                notification = new api.Notification( notificationCode, {
                    type: 'error',
                    message: api.l10n.futureDateError
                } );
                control.notifications.add( notification );
            } else {
                control.notifications.remove( notificationCode );
            }

            return control;
        }
    });

    /**
     * Class PreviewLinkControl.
     *
     * @since 4.9.0
     * @class    wp.customize.PreviewLinkControl
     * @augments wp.customize.Control
     */
    api.PreviewLinkControl = api.Control.extend(/** @lends wp.customize.PreviewLinkControl.prototype */{

        defaults: _.extend( {}, api.Control.prototype.defaults, {
            templateId: 'customize-preview-link-control'
        } ),

        /**
         * Initialize behaviors.
         *
         * @since 4.9.0
         * @return {void}
         */
        ready: function ready() {
            var control = this, element, component, node, url, input, button;

            _.bindAll( control, 'updatePreviewLink' );

            if ( ! control.setting ) {
                control.setting = new api.Value();
            }

            control.previewElements = {};

            control.container.find( '.preview-control-element' ).each( function() {
                node = $( this );
                component = node.data( 'component' );
                element = new api.Element( node );
                control.previewElements[ component ] = element;
                control.elements.push( element );
            } );

            url = control.previewElements.url;
            input = control.previewElements.input;
            button = control.previewElements.button;

            input.link( control.setting );
            url.link( control.setting );

            url.bind( function( value ) {
                url.element.parent().attr( {
                    href: value,
                    target: api.settings.changeset.uuid
                } );
            } );

            api.bind( 'ready', control.updatePreviewLink );
            api.state( 'saved' ).bind( control.updatePreviewLink );
            api.state( 'changesetStatus' ).bind( control.updatePreviewLink );
            api.state( 'activated' ).bind( control.updatePreviewLink );
            api.previewer.previewUrl.bind( control.updatePreviewLink );

            button.element.on( 'click', function( event ) {
                event.preventDefault();
                if ( control.setting() ) {
                    input.element.select();
                    document.execCommand( 'copy' );
                    button( button.element.data( 'copied-text' ) );
                }
            } );

            url.element.parent().on( 'click', function( event ) {
                if ( $( this ).hasClass( 'disabled' ) ) {
                    event.preventDefault();
                }
            } );

            button.element.on( 'mouseenter', function() {
                if ( control.setting() ) {
                    button( button.element.data( 'copy-text' ) );
                }
            } );
        },

        /**
         * Updates Preview Link
         *
         * @since 4.9.0
         * @return {void}
         */
        updatePreviewLink: function updatePreviewLink() {
            var control = this, unsavedDirtyValues;

            unsavedDirtyValues = ! api.state( 'saved' ).get() || '' === api.state( 'changesetStatus' ).get() || 'auto-draft' === api.state( 'changesetStatus' ).get();

            control.toggleSaveNotification( unsavedDirtyValues );
            control.previewElements.url.element.parent().toggleClass( 'disabled', unsavedDirtyValues );
            control.previewElements.button.element.prop( 'disabled', unsavedDirtyValues );
            control.setting.set( api.previewer.getFrontendPreviewUrl() );
        },

        /**
         * Toggles save notification.
         *
         * @since 4.9.0
         * @param {boolean} notify Add or remove notification.
         * @return {void}
         */
        toggleSaveNotification: function toggleSaveNotification( notify ) {
            var control = this, notificationCode, notification;

            notificationCode = 'changes_not_saved';

            if ( notify ) {
                notification = new api.Notification( notificationCode, {
                    type: 'info',
                    message: api.l10n.saveBeforeShare
                } );
                control.notifications.add( notification );
            } else {
                control.notifications.remove( notificationCode );
            }
        }
    });

    /**
     * Change objects contained within the main customize object to Settings.
     *
     * @alias wp.customize.defaultConstructor
     */
    api.defaultConstructor = api.Setting;

    /**
     * Callback for resolved controls.
     *
     * @callback wp.customize.deferredControlsCallback
     * @param {wp.customize.Control[]} controls Resolved controls.
     */

    /**
     * Collection of all registered controls.
     *
     * @alias wp.customize.control
     *
     * @since 3.4.0
     *
     * @type {Function}
     * @param {...string} ids - One or more ids for controls to obtain.
     * @param {deferredControlsCallback} [callback] - Function called when all supplied controls exist.
     * @return {wp.customize.Control|undefined|jQuery.promise} Control instance or undefined (if function called with one id param),
     *                                                         or promise resolving to requested controls.
     *
     * @example <caption>Loop over all registered controls.</caption>
     * wp.customize.control.each( function( control ) { ... } );
     *
     * @example <caption>Getting `background_color` control instance.</caption>
     * control = wp.customize.control( 'background_color' );
     *
     * @example <caption>Check if control exists.</caption>
     * hasControl = wp.customize.control.has( 'background_color' );
     *
     * @example <caption>Deferred getting of `background_color` control until it exists, using callback.</caption>
     * wp.customize.control( 'background_color', function( control ) { ... } );
     *
     * @example <caption>Get title and tagline controls when they both exist, using promise (only available when multiple IDs are present).</caption>
     * promise = wp.customize.control( 'blogname', 'blogdescription' );
     * promise.done( function( titleControl, taglineControl ) { ... } );
     *
     * @example <caption>Get title and tagline controls when they both exist, using callback.</caption>
     * wp.customize.control( 'blogname', 'blogdescription', function( titleControl, taglineControl ) { ... } );
     *
     * @example <caption>Getting setting value for `background_color` control.</caption>
     * value = wp.customize.control( 'background_color ').setting.get();
     * value = wp.customize( 'background_color' ).get(); // Same as above, since setting ID and control ID are the same.
     *
     * @example <caption>Add new control for site title.</caption>
     * wp.customize.control.add( new wp.customize.Control( 'other_blogname', {
     *     setting: 'blogname',
     *     type: 'text',
     *     label: 'Site title',
     *     section: 'other_site_identify'
     * } ) );
     *
     * @example <caption>Remove control.</caption>
     * wp.customize.control.remove( 'other_blogname' );
     *
     * @example <caption>Listen for control being added.</caption>
     * wp.customize.control.bind( 'add', function( addedControl ) { ... } )
     *
     * @example <caption>Listen for control being removed.</caption>
     * wp.customize.control.bind( 'removed', function( removedControl ) { ... } )
     */
    api.control = new api.Values({ defaultConstructor: api.Control });

    /**
     * Callback for resolved sections.
     *
     * @callback wp.customize.deferredSectionsCallback
     * @param {wp.customize.Section[]} sections Resolved sections.
     */

    /**
     * Collection of all registered sections.
     *
     * @alias wp.customize.section
     *
     * @since 3.4.0
     *
     * @type {Function}
     * @param {...string} ids - One or more ids for sections to obtain.
     * @param {deferredSectionsCallback} [callback] - Function called when all supplied sections exist.
     * @return {wp.customize.Section|undefined|jQuery.promise} Section instance or undefined (if function called with one id param),
     *                                                         or promise resolving to requested sections.
     *
     * @example <caption>Loop over all registered sections.</caption>
     * wp.customize.section.each( function( section ) { ... } )
     *
     * @example <caption>Getting `title_tagline` section instance.</caption>
     * section = wp.customize.section( 'title_tagline' )
     *
     * @example <caption>Expand dynamically-created section when it exists.</caption>
     * wp.customize.section( 'dynamically_created', function( section ) {
     *     section.expand();
     * } );
     *
     * @see {@link wp.customize.control} for further examples of how to interact with {@link wp.customize.Values} instances.
     */
    api.section = new api.Values({ defaultConstructor: api.Section });

    /**
     * Callback for resolved panels.
     *
     * @callback wp.customize.deferredPanelsCallback
     * @param {wp.customize.Panel[]} panels Resolved panels.
     */

    /**
     * Collection of all registered panels.
     *
     * @alias wp.customize.panel
     *
     * @since 4.0.0
     *
     * @type {Function}
     * @param {...string} ids - One or more ids for panels to obtain.
     * @param {deferredPanelsCallback} [callback] - Function called when all supplied panels exist.
     * @return {wp.customize.Panel|undefined|jQuery.promise} Panel instance or undefined (if function called with one id param),
     *                                                       or promise resolving to requested panels.
     *
     * @example <caption>Loop over all registered panels.</caption>
     * wp.customize.panel.each( function( panel ) { ... } )
     *
     * @example <caption>Getting nav_menus panel instance.</caption>
     * panel = wp.customize.panel( 'nav_menus' );
     *
     * @example <caption>Expand dynamically-created panel when it exists.</caption>
     * wp.customize.panel( 'dynamically_created', function( panel ) {
     *     panel.expand();
     * } );
     *
     * @see {@link wp.customize.control} for further examples of how to interact with {@link wp.customize.Values} instances.
     */
    api.panel = new api.Values({ defaultConstructor: api.Panel });

    /**
     * Callback for resolved notifications.
     *
     * @callback wp.customize.deferredNotificationsCallback
     * @param {wp.customize.Notification[]} notifications Resolved notifications.
     */

    /**
     * Collection of all global notifications.
     *
     * @alias wp.customize.notifications
     *
     * @since 4.9.0
     *
     * @type {Function}
     * @param {...string} codes - One or more codes for notifications to obtain.
     * @param {deferredNotificationsCallback} [callback] - Function called when all supplied notifications exist.
     * @return {wp.customize.Notification|undefined|jQuery.promise} Notification instance or undefined (if function called with one code param),
     *                                                              or promise resolving to requested notifications.
     *
     * @example <caption>Check if existing notification</caption>
     * exists = wp.customize.notifications.has( 'a_new_day_arrived' );
     *
     * @example <caption>Obtain existing notification</caption>
     * notification = wp.customize.notifications( 'a_new_day_arrived' );
     *
     * @example <caption>Obtain notification that may not exist yet.</caption>
     * wp.customize.notifications( 'a_new_day_arrived', function( notification ) { ... } );
     *
     * @example <caption>Add a warning notification.</caption>
     * wp.customize.notifications.add( new wp.customize.Notification( 'midnight_almost_here', {
     *     type: 'warning',
     *     message: 'Midnight has almost arrived!',
     *     dismissible: true
     * } ) );
     *
     * @example <caption>Remove a notification.</caption>
     * wp.customize.notifications.remove( 'a_new_day_arrived' );
     *
     * @see {@link wp.customize.control} for further examples of how to interact with {@link wp.customize.Values} instances.
     */
    api.notifications = new api.Notifications();

    api.PreviewFrame = api.Messenger.extend(/** @lends wp.customize.PreviewFrame.prototype */{
        sensitivity: null, // Will get set to api.settings.timeouts.previewFrameSensitivity.

        /**
         * An object that fetches a preview in the background of the document, which
         * allows for seamless replacement of an existing preview.
         *
         * @constructs wp.customize.PreviewFrame
         * @augments   wp.customize.Messenger
         *
         * @param {Object} params.container
         * @param {Object} params.previewUrl
         * @param {Object} params.query
         * @param {Object} options
         */
        initialize: function( params, options ) {
            var deferred = $.Deferred();

            /*
             * Make the instance of the PreviewFrame the promise object
             * so other objects can easily interact with it.
             */
            deferred.promise( this );

            this.container = params.container;

            $.extend( params, { channel: api.PreviewFrame.uuid() });

            api.Messenger.prototype.initialize.call( this, params, options );

            this.add( 'previewUrl', params.previewUrl );

            this.query = $.extend( params.query || {}, { customize_messenger_channel: this.channel() });

            this.run( deferred );
        },

        /**
         * Run the preview request.
         *
         * @param {Object} deferred jQuery Deferred object to be resolved with
         *                          the request.
         */
        run: function( deferred ) {
            var previewFrame = this,
                loaded = false,
                ready = false,
                readyData = null,
                hasPendingChangesetUpdate = '{}' !== previewFrame.query.customized,
                urlParser,
                params,
                form;

            if ( previewFrame._ready ) {
                previewFrame.unbind( 'ready', previewFrame._ready );
            }

            previewFrame._ready = function( data ) {
                ready = true;
                readyData = data;
                previewFrame.container.addClass( 'iframe-ready' );
                if ( ! data ) {
                    return;
                }

                if ( loaded ) {
                    deferred.resolveWith( previewFrame, [ data ] );
                }
            };

            previewFrame.bind( 'ready', previewFrame._ready );

            urlParser = document.createElement( 'a' );
            urlParser.href = previewFrame.previewUrl();

            params = _.extend(
                api.utils.parseQueryString( urlParser.search.substr( 1 ) ),
                {
                    customize_changeset_uuid: previewFrame.query.customize_changeset_uuid,
                    customize_theme: previewFrame.query.customize_theme,
                    customize_messenger_channel: previewFrame.query.customize_messenger_channel
                }
            );
            if ( api.settings.changeset.autosaved || ! api.state( 'saved' ).get() ) {
                params.customize_autosaved = 'on';
            }

            urlParser.search = $.param( params );
            previewFrame.iframe = $( '<iframe />', {
                title: api.l10n.previewIframeTitle,
                name: 'customize-' + previewFrame.channel()
            } );
            previewFrame.iframe.attr( 'onmousewheel', '' ); // Workaround for Safari bug. See WP Trac #38149.
            previewFrame.iframe.attr( 'sandbox', 'allow-forms allow-modals allow-orientation-lock allow-pointer-lock allow-popups allow-popups-to-escape-sandbox allow-presentation allow-same-origin allow-scripts' );

            if ( ! hasPendingChangesetUpdate ) {
                previewFrame.iframe.attr( 'src', urlParser.href );
            } else {
                previewFrame.iframe.attr( 'data-src', urlParser.href ); // For debugging purposes.
            }

            previewFrame.iframe.appendTo( previewFrame.container );
            previewFrame.targetWindow( previewFrame.iframe[0].contentWindow );

            /*
             * Submit customized data in POST request to preview frame window since
             * there are setting value changes not yet written to changeset.
             */
            if ( hasPendingChangesetUpdate ) {
                form = $( '<form>', {
                    action: urlParser.href,
                    target: previewFrame.iframe.attr( 'name' ),
                    method: 'post',
                    hidden: 'hidden'
                } );
                form.append( $( '<input>', {
                    type: 'hidden',
                    name: '_method',
                    value: 'GET'
                } ) );
                _.each( previewFrame.query, function( value, key ) {
                    form.append( $( '<input>', {
                        type: 'hidden',
                        name: key,
                        value: value
                    } ) );
                } );
                previewFrame.container.append( form );
                form.trigger( 'submit' );
                form.remove(); // No need to keep the form around after submitted.
            }

            previewFrame.bind( 'iframe-loading-error', function( error ) {
                previewFrame.iframe.remove();

                // Check if the user is not logged in.
                if ( 0 === error ) {
                    previewFrame.login( deferred );
                    return;
                }

                // Check for cheaters.
                if ( -1 === error ) {
                    deferred.rejectWith( previewFrame, [ 'cheatin' ] );
                    return;
                }

                deferred.rejectWith( previewFrame, [ 'request failure' ] );
            } );

            previewFrame.iframe.one( 'load', function() {
                loaded = true;

                if ( ready ) {
                    deferred.resolveWith( previewFrame, [ readyData ] );
                } else {
                    setTimeout( function() {
                        deferred.rejectWith( previewFrame, [ 'ready timeout' ] );
                    }, previewFrame.sensitivity );
                }
            });
        },

        login: function( deferred ) {
            var self = this,
                reject;

            reject = function() {
                deferred.rejectWith( self, [ 'logged out' ] );
            };

            if ( this.triedLogin ) {
                return reject();
            }

            // Check if we have an admin cookie.
            $.get( api.settings.url.ajax, {
                action: 'logged-in'
            }).fail( reject ).done( function( response ) {
                var iframe;

                if ( '1' !== response ) {
                    reject();
                }

                iframe = $( '<iframe />', { 'src': self.previewUrl(), 'title': api.l10n.previewIframeTitle } ).hide();
                iframe.appendTo( self.container );
                iframe.on( 'load', function() {
                    self.triedLogin = true;

                    iframe.remove();
                    self.run( deferred );
                });
            });
        },

        destroy: function() {
            api.Messenger.prototype.destroy.call( this );

            if ( this.iframe ) {
                this.iframe.remove();
            }

            delete this.iframe;
            delete this.targetWindow;
        }
    });

    (function(){
        var id = 0;
        /**
         * Return an incremented ID for a preview messenger channel.
         *
         * This function is named "uuid" for historical reasons, but it is a
         * misnomer as it is not an actual UUID, and it is not universally unique.
         * This is not to be confused with `api.settings.changeset.uuid`.
         *
         * @return {string}
         */
        api.PreviewFrame.uuid = function() {
            return 'preview-' + String( id++ );
        };
    }());

    /**
     * Set the document title of the customizer.
     *
     * @alias wp.customize.setDocumentTitle
     *
     * @since 4.1.0
     *
     * @param {string} documentTitle
     */
    api.setDocumentTitle = function ( documentTitle ) {
        var tmpl, title;
        tmpl = api.settings.documentTitleTmpl;
        title = tmpl.replace( '%s', documentTitle );
        document.title = title;
        api.trigger( 'title', title );
    };

    api.Previewer = api.Messenger.extend(/** @lends wp.customize.Previewer.prototype */{
        refreshBuffer: null, // Will get set to api.settings.timeouts.windowRefresh.

        /**
         * @constructs wp.customize.Previewer
         * @augments   wp.customize.Messenger
         *
         * @param {Array}  params.allowedUrls
         * @param {string} params.container   A selector or jQuery element for the preview
         *                                    frame to be placed.
         * @param {string} params.form
         * @param {string} params.previewUrl  The URL to preview.
         * @param {Object} options
         */
        initialize: function( params, options ) {
            var previewer = this,
                urlParser = document.createElement( 'a' );

            $.extend( previewer, options || {} );
            previewer.deferred = {
                active: $.Deferred()
            };

            // Debounce to prevent hammering server and then wait for any pending update requests.
            previewer.refresh = _.debounce(
                ( function( originalRefresh ) {
                    return function() {
                        var isProcessingComplete, refreshOnceProcessingComplete;
                        isProcessingComplete = function() {
                            return 0 === api.state( 'processing' ).get();
                        };
                        if ( isProcessingComplete() ) {
                            originalRefresh.call( previewer );
                        } else {
                            refreshOnceProcessingComplete = function() {
                                if ( isProcessingComplete() ) {
                                    originalRefresh.call( previewer );
                                    api.state( 'processing' ).unbind( refreshOnceProcessingComplete );
                                }
                            };
                            api.state( 'processing' ).bind( refreshOnceProcessingComplete );
                        }
                    };
                }( previewer.refresh ) ),
                previewer.refreshBuffer
            );

            previewer.container   = api.ensure( params.container );
            previewer.allowedUrls = params.allowedUrls;

            params.url = window.location.href;

            api.Messenger.prototype.initialize.call( previewer, params );

            urlParser.href = previewer.origin();
            previewer.add( 'scheme', urlParser.protocol.replace( /:$/, '' ) );

            /*
             * Limit the URL to internal, front-end links.
             *
             * 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.
             */

            previewer.add( 'previewUrl', params.previewUrl ).setter( function( to ) {
                var result = null, urlParser, queryParams, parsedAllowedUrl, parsedCandidateUrls = [];
                urlParser = document.createElement( 'a' );
                urlParser.href = to;

                // Abort if URL is for admin or (static) files in wp-includes or wp-content.
                if ( /\/wp-(admin|includes|content)(\/|$)/.test( urlParser.pathname ) ) {
                    return null;
                }

                // Remove state query params.
                if ( urlParser.search.length > 1 ) {
                    queryParams = api.utils.parseQueryString( urlParser.search.substr( 1 ) );
                    delete queryParams.customize_changeset_uuid;
                    delete queryParams.customize_theme;
                    delete queryParams.customize_messenger_channel;
                    delete queryParams.customize_autosaved;
                    if ( _.isEmpty( queryParams ) ) {
                        urlParser.search = '';
                    } else {
                        urlParser.search = $.param( queryParams );
                    }
                }

                parsedCandidateUrls.push( urlParser );

                // Prepend list with URL that matches the scheme/protocol of the iframe.
                if ( previewer.scheme.get() + ':' !== urlParser.protocol ) {
                    urlParser = document.createElement( 'a' );
                    urlParser.href = parsedCandidateUrls[0].href;
                    urlParser.protocol = previewer.scheme.get() + ':';
                    parsedCandidateUrls.unshift( urlParser );
                }

                // Attempt to match the URL to the control frame's scheme and check if it's allowed. If not, try the original URL.
                parsedAllowedUrl = document.createElement( 'a' );
                _.find( parsedCandidateUrls, function( parsedCandidateUrl ) {
                    return ! _.isUndefined( _.find( previewer.allowedUrls, function( allowedUrl ) {
                        parsedAllowedUrl.href = allowedUrl;
                        if ( urlParser.protocol === parsedAllowedUrl.protocol && urlParser.host === parsedAllowedUrl.host && 0 === urlParser.pathname.indexOf( parsedAllowedUrl.pathname.replace( /\/$/, '' ) ) ) {
                            result = parsedCandidateUrl.href;
                            return true;
                        }
                    } ) );
                } );

                return result;
            });

            previewer.bind( 'ready', previewer.ready );

            // Start listening for keep-alive messages when iframe first loads.
            previewer.deferred.active.done( _.bind( previewer.keepPreviewAlive, previewer ) );

            previewer.bind( 'synced', function() {
                previewer.send( 'active' );
            } );

            // Refresh the preview when the URL is changed (but not yet).
            previewer.previewUrl.bind( previewer.refresh );

            previewer.scroll = 0;
            previewer.bind( 'scroll', function( distance ) {
                previewer.scroll = distance;
            });

            // Update the URL when the iframe sends a URL message, resetting scroll position. If URL is unchanged, then refresh.
            previewer.bind( 'url', function( url ) {
                var onUrlChange, urlChanged = false;
                previewer.scroll = 0;
                onUrlChange = function() {
                    urlChanged = true;
                };
                previewer.previewUrl.bind( onUrlChange );
                previewer.previewUrl.set( url );
                previewer.previewUrl.unbind( onUrlChange );
                if ( ! urlChanged ) {
                    previewer.refresh();
                }
            } );

            // Update the document title when the preview changes.
            previewer.bind( 'documentTitle', function ( title ) {
                api.setDocumentTitle( title );
            } );
        },

        /**
         * Handle the preview receiving the ready message.
         *
         * @since 4.7.0
         * @access public
         *
         * @param {Object} data - Data from preview.
         * @param {string} data.currentUrl - Current URL.
         * @param {Object} data.activePanels - Active panels.
         * @param {Object} data.activeSections Active sections.
         * @param {Object} data.activeControls Active controls.
         * @return {void}
         */
        ready: function( data ) {
            var previewer = this, synced = {}, constructs;

            synced.settings = api.get();
            synced['settings-modified-while-loading'] = previewer.settingsModifiedWhileLoading;
            if ( 'resolved' !== previewer.deferred.active.state() || previewer.loading ) {
                synced.scroll = previewer.scroll;
            }
            synced['edit-shortcut-visibility'] = api.state( 'editShortcutVisibility' ).get();
            previewer.send( 'sync', synced );

            // Set the previewUrl without causing the url to set the iframe.
            if ( data.currentUrl ) {
                previewer.previewUrl.unbind( previewer.refresh );
                previewer.previewUrl.set( data.currentUrl );
                previewer.previewUrl.bind( previewer.refresh );
            }

            /*
             * Walk over all panels, sections, and controls and set their
             * respective active states to true if the preview explicitly
             * indicates as such.
             */
            constructs = {
                panel: data.activePanels,
                section: data.activeSections,
                control: data.activeControls
            };
            _( constructs ).each( function ( activeConstructs, type ) {
                api[ type ].each( function ( construct, id ) {
                    var isDynamicallyCreated = _.isUndefined( api.settings[ type + 's' ][ id ] );

                    /*
                     * If the construct was created statically in PHP (not dynamically in JS)
                     * then consider a missing (undefined) value in the activeConstructs to
                     * mean it should be deactivated (since it is gone). But if it is
                     * dynamically created then only toggle activation if the value is defined,
                     * as this means that the construct was also then correspondingly
                     * created statically in PHP and the active callback is available.
                     * Otherwise, dynamically-created constructs should normally have
                     * their active states toggled in JS rather than from PHP.
                     */
                    if ( ! isDynamicallyCreated || ! _.isUndefined( activeConstructs[ id ] ) ) {
                        if ( activeConstructs[ id ] ) {
                            construct.activate();
                        } else {
                            construct.deactivate();
                        }
                    }
                } );
            } );

            if ( data.settingValidities ) {
                api._handleSettingValidities( {
                    settingValidities: data.settingValidities,
                    focusInvalidControl: false
                } );
            }
        },

        /**
         * Keep the preview alive by listening for ready and keep-alive messages.
         *
         * If a message is not received in the allotted time then the iframe will be set back to the last known valid URL.
         *
         * @since 4.7.0
         * @access public
         *
         * @return {void}
         */
        keepPreviewAlive: function keepPreviewAlive() {
            var previewer = this, keepAliveTick, timeoutId, handleMissingKeepAlive, scheduleKeepAliveCheck;

            /**
             * Schedule a preview keep-alive check.
             *
             * Note that if a page load takes longer than keepAliveCheck milliseconds,
             * the keep-alive messages will still be getting sent from the previous
             * URL.
             */
            scheduleKeepAliveCheck = function() {
                timeoutId = setTimeout( handleMissingKeepAlive, api.settings.timeouts.keepAliveCheck );
            };

            /**
             * Set the previewerAlive state to true when receiving a message from the preview.
             */
            keepAliveTick = function() {
                api.state( 'previewerAlive' ).set( true );
                clearTimeout( timeoutId );
                scheduleKeepAliveCheck();
            };

            /**
             * Set the previewerAlive state to false if keepAliveCheck milliseconds have transpired without a message.
             *
             * This is most likely to happen in the case of a connectivity error, or if the theme causes the browser
             * to navigate to a non-allowed URL. Setting this state to false will force settings with a postMessage
             * transport to use refresh instead, causing the preview frame also to be replaced with the current
             * allowed preview URL.
             */
            handleMissingKeepAlive = function() {
                api.state( 'previewerAlive' ).set( false );
            };
            scheduleKeepAliveCheck();

            previewer.bind( 'ready', keepAliveTick );
            previewer.bind( 'keep-alive', keepAliveTick );
        },

        /**
         * Query string data sent with each preview request.
         *
         * @abstract
         */
        query: function() {},

        abort: function() {
            if ( this.loading ) {
                this.loading.destroy();
                delete this.loading;
            }
        },

        /**
         * Refresh the preview seamlessly.
         *
         * @since 3.4.0
         * @access public
         *
         * @return {void}
         */
        refresh: function() {
            var previewer = this, onSettingChange;

            // Display loading indicator.
            previewer.send( 'loading-initiated' );

            previewer.abort();

            previewer.loading = new api.PreviewFrame({
                url:        previewer.url(),
                previewUrl: previewer.previewUrl(),
                query:      previewer.query( { excludeCustomizedSaved: true } ) || {},
                container:  previewer.container
            });

            previewer.settingsModifiedWhileLoading = {};
            onSettingChange = function( setting ) {
                previewer.settingsModifiedWhileLoading[ setting.id ] = true;
            };
            api.bind( 'change', onSettingChange );
            previewer.loading.always( function() {
                api.unbind( 'change', onSettingChange );
            } );

            previewer.loading.done( function( readyData ) {
                var loadingFrame = this, onceSynced;

                previewer.preview = loadingFrame;
                previewer.targetWindow( loadingFrame.targetWindow() );
                previewer.channel( loadingFrame.channel() );

                onceSynced = function() {
                    loadingFrame.unbind( 'synced', onceSynced );
                    if ( previewer._previousPreview ) {
                        previewer._previousPreview.destroy();
                    }
                    previewer._previousPreview = previewer.preview;
                    previewer.deferred.active.resolve();
                    delete previewer.loading;
                };
                loadingFrame.bind( 'synced', onceSynced );

                // This event will be received directly by the previewer in normal navigation; this is only needed for seamless refresh.
                previewer.trigger( 'ready', readyData );
            });

            previewer.loading.fail( function( reason ) {
                previewer.send( 'loading-failed' );

                if ( 'logged out' === reason ) {
                    if ( previewer.preview ) {
                        previewer.preview.destroy();
                        delete previewer.preview;
                    }

                    previewer.login().done( previewer.refresh );
                }

                if ( 'cheatin' === reason ) {
                    previewer.cheatin();
                }
            });
        },

        login: function() {
            var previewer = this,
                deferred, messenger, iframe;

            if ( this._login ) {
                return this._login;
            }

            deferred = $.Deferred();
            this._login = deferred.promise();

            messenger = new api.Messenger({
                channel: 'login',
                url:     api.settings.url.login
            });

            iframe = $( '<iframe />', { 'src': api.settings.url.login, 'title': api.l10n.loginIframeTitle } ).appendTo( this.container );

            messenger.targetWindow( iframe[0].contentWindow );

            messenger.bind( 'login', function () {
                var refreshNonces = previewer.refreshNonces();

                refreshNonces.always( function() {
                    iframe.remove();
                    messenger.destroy();
                    delete previewer._login;
                });

                refreshNonces.done( function() {
                    deferred.resolve();
                });

                refreshNonces.fail( function() {
                    previewer.cheatin();
                    deferred.reject();
                });
            });

            return this._login;
        },

        cheatin: function() {
            $( document.body ).empty().addClass( 'cheatin' ).append(
                '<h1>' + api.l10n.notAllowedHeading + '</h1>' +
                '<p>' + api.l10n.notAllowed + '</p>'
            );
        },

        refreshNonces: function() {
            var request, deferred = $.Deferred();

            deferred.promise();

            request = wp.ajax.post( 'customize_refresh_nonces', {
                wp_customize: 'on',
                customize_theme: api.settings.theme.stylesheet
            });

            request.done( function( response ) {
                api.trigger( 'nonce-refresh', response );
                deferred.resolve();
            });

            request.fail( function() {
                deferred.reject();
            });

            return deferred;
        }
    });

    api.settingConstructor = {};
    api.controlConstructor = {
        color:               api.ColorControl,
        media:               api.MediaControl,
        upload:              api.UploadControl,
        image:               api.ImageControl,
        cropped_image:       api.CroppedImageControl,
        site_icon:           api.SiteIconControl,
        header:              api.HeaderControl,
        background:          api.BackgroundControl,
        background_position: api.BackgroundPositionControl,
        theme:               api.ThemeControl,
        date_time:           api.DateTimeControl,
        code_editor:         api.CodeEditorControl
    };
    api.panelConstructor = {
        themes: api.ThemesPanel
    };
    api.sectionConstructor = {
        themes: api.ThemesSection,
        outer: api.OuterSection
    };

    /**
     * Handle setting_validities in an error response for the customize-save request.
     *
     * Add notifications to the settings and focus on the first control that has an invalid setting.
     *
     * @alias wp.customize._handleSettingValidities
     *
     * @since 4.6.0
     * @private
     *
     * @param {Object}  args
     * @param {Object}  args.settingValidities
     * @param {boolean} [args.focusInvalidControl=false]
     * @return {void}
     */
    api._handleSettingValidities = function handleSettingValidities( args ) {
        var invalidSettingControls, invalidSettings = [], wasFocused = false;

        // Find the controls that correspond to each invalid setting.
        _.each( args.settingValidities, function( validity, settingId ) {
            var setting = api( settingId );
            if ( setting ) {

                // Add notifications for invalidities.
                if ( _.isObject( validity ) ) {
                    _.each( validity, function( params, code ) {
                        var notification, existingNotification, needsReplacement = false;
                        notification = new api.Notification( code, _.extend( { fromServer: true }, params ) );

                        // Remove existing notification if already exists for code but differs in parameters.
                        existingNotification = setting.notifications( notification.code );
                        if ( existingNotification ) {
                            needsReplacement = notification.type !== existingNotification.type || notification.message !== existingNotification.message || ! _.isEqual( notification.data, existingNotification.data );
                        }
                        if ( needsReplacement ) {
                            setting.notifications.remove( code );
                        }

                        if ( ! setting.notifications.has( notification.code ) ) {
                            setting.notifications.add( notification );
                        }
                        invalidSettings.push( setting.id );
                    } );
                }

                // Remove notification errors that are no longer valid.
                setting.notifications.each( function( notification ) {
                    if ( notification.fromServer && 'error' === notification.type && ( true === validity || ! validity[ notification.code ] ) ) {
                        setting.notifications.remove( notification.code );
                    }
                } );
            }
        } );

        if ( args.focusInvalidControl ) {
            invalidSettingControls = api.findControlsForSettings( invalidSettings );

            // Focus on the first control that is inside of an expanded section (one that is visible).
            _( _.values( invalidSettingControls ) ).find( function( controls ) {
                return _( controls ).find( function( control ) {
                    var isExpanded = control.section() && api.section.has( control.section() ) && api.section( control.section() ).expanded();
                    if ( isExpanded && control.expanded ) {
                        isExpanded = control.expanded();
                    }
                    if ( isExpanded ) {
                        control.focus();
                        wasFocused = true;
                    }
                    return wasFocused;
                } );
            } );

            // Focus on the first invalid control.
            if ( ! wasFocused && ! _.isEmpty( invalidSettingControls ) ) {
                _.values( invalidSettingControls )[0][0].focus();
            }
        }
    };

    /**
     * Find all controls associated with the given settings.
     *
     * @alias wp.customize.findControlsForSettings
     *
     * @since 4.6.0
     * @param {string[]} settingIds Setting IDs.
     * @return {Object<string, wp.customize.Control>} Mapping setting ids to arrays of controls.
     */
    api.findControlsForSettings = function findControlsForSettings( settingIds ) {
        var controls = {}, settingControls;
        _.each( _.unique( settingIds ), function( settingId ) {
            var setting = api( settingId );
            if ( setting ) {
                settingControls = setting.findControls();
                if ( settingControls && settingControls.length > 0 ) {
                    controls[ settingId ] = settingControls;
                }
            }
        } );
        return controls;
    };

    /**
     * Sort panels, sections, controls by priorities. Hide empty sections and panels.
     *
     * @alias wp.customize.reflowPaneContents
     *
     * @since 4.1.0
     */
    api.reflowPaneContents = _.bind( function () {

        var appendContainer, activeElement, rootHeadContainers, rootNodes = [], wasReflowed = false;

        if ( document.activeElement ) {
            activeElement = $( document.activeElement );
        }

        // Sort the sections within each panel.
        api.panel.each( function ( panel ) {
            if ( 'themes' === panel.id ) {
                return; // Don't reflow theme sections, as doing so moves them after the themes container.
            }

            var sections = panel.sections(),
                sectionHeadContainers = _.pluck( sections, 'headContainer' );
            rootNodes.push( panel );
            appendContainer = ( panel.contentContainer.is( 'ul' ) ) ? panel.contentContainer : panel.contentContainer.find( 'ul:first' );
            if ( ! api.utils.areElementListsEqual( sectionHeadContainers, appendContainer.children( '[id]' ) ) ) {
                _( sections ).each( function ( section ) {
                    appendContainer.append( section.headContainer );
                } );
                wasReflowed = true;
            }
        } );

        // Sort the controls within each section.
        api.section.each( function ( section ) {
            var controls = section.controls(),
                controlContainers = _.pluck( controls, 'container' );
            if ( ! section.panel() ) {
                rootNodes.push( section );
            }
            appendContainer = ( section.contentContainer.is( 'ul' ) ) ? section.contentContainer : section.contentContainer.find( 'ul:first' );
            if ( ! api.utils.areElementListsEqual( controlContainers, appendContainer.children( '[id]' ) ) ) {
                _( controls ).each( function ( control ) {
                    appendContainer.append( control.container );
                } );
                wasReflowed = true;
            }
        } );

        // Sort the root panels and sections.
        rootNodes.sort( api.utils.prioritySort );
        rootHeadContainers = _.pluck( rootNodes, 'headContainer' );
        appendContainer = $( '#customize-theme-controls .customize-pane-parent' ); // @todo This should be defined elsewhere, and to be configurable.
        if ( ! api.utils.areElementListsEqual( rootHeadContainers, appendContainer.children() ) ) {
            _( rootNodes ).each( function ( rootNode ) {
                appendContainer.append( rootNode.headContainer );
            } );
            wasReflowed = true;
        }

        // Now re-trigger the active Value callbacks so that the panels and sections can decide whether they can be rendered.
        api.panel.each( function ( panel ) {
            var value = panel.active();
            panel.active.callbacks.fireWith( panel.active, [ value, value ] );
        } );
        api.section.each( function ( section ) {
            var value = section.active();
            section.active.callbacks.fireWith( section.active, [ value, value ] );
        } );

        // Restore focus if there was a reflow and there was an active (focused) element.
        if ( wasReflowed && activeElement ) {
            activeElement.trigger( 'focus' );
        }
        api.trigger( 'pane-contents-reflowed' );
    }, api );

    // Define state values.
    api.state = new api.Values();
    _.each( [
        'saved',
        'saving',
        'trashing',
        'activated',
        'processing',
        'paneVisible',
        'expandedPanel',
        'expandedSection',
        'changesetDate',
        'selectedChangesetDate',
        'changesetStatus',
        'selectedChangesetStatus',
        'remainingTimeToPublish',
        'previewerAlive',
        'editShortcutVisibility',
        'changesetLocked',
        'previewedDevice'
    ], function( name ) {
        api.state.create( name );
    });

    $( function() {
        api.settings = window._wpCustomizeSettings;
        api.l10n = window._wpCustomizeControlsL10n;

        // Check if we can run the Customizer.
        if ( ! api.settings ) {
            return;
        }

        // Bail if any incompatibilities are found.
        if ( ! $.support.postMessage || ( ! $.support.cors && api.settings.isCrossDomain ) ) {
            return;
        }

        if ( null === api.PreviewFrame.prototype.sensitivity ) {
            api.PreviewFrame.prototype.sensitivity = api.settings.timeouts.previewFrameSensitivity;
        }
        if ( null === api.Previewer.prototype.refreshBuffer ) {
            api.Previewer.prototype.refreshBuffer = api.settings.timeouts.windowRefresh;
        }

        var parent,
            body = $( document.body ),
            overlay = body.children( '.wp-full-overlay' ),
            title = $( '#customize-info .panel-title.site-title' ),
            closeBtn = $( '.customize-controls-close' ),
            saveBtn = $( '#save' ),
            btnWrapper = $( '#customize-save-button-wrapper' ),
            publishSettingsBtn = $( '#publish-settings' ),
            footerActions = $( '#customize-footer-actions' );

        // Add publish settings section in JS instead of PHP since the Customizer depends on it to function.
        api.bind( 'ready', function() {
            api.section.add( new api.OuterSection( 'publish_settings', {
                title: api.l10n.publishSettings,
                priority: 0,
                active: api.settings.theme.active
            } ) );
        } );

        // Set up publish settings section and its controls.
        api.section( 'publish_settings', function( section ) {
            var updateButtonsState, trashControl, updateSectionActive, isSectionActive, statusControl, dateControl, toggleDateControl, publishWhenTime, pollInterval, updateTimeArrivedPoller, cancelScheduleButtonReminder, timeArrivedPollingInterval = 1000;

            trashControl = new api.Control( 'trash_changeset', {
                type: 'button',
                section: section.id,
                priority: 30,
                input_attrs: {
                    'class': 'button-link button-link-delete',
                    value: api.l10n.discardChanges
                }
            } );
            api.control.add( trashControl );
            trashControl.deferred.embedded.done( function() {
                trashControl.container.find( '.button-link' ).on( 'click', function() {
                    if ( confirm( api.l10n.trashConfirm ) ) {
                        wp.customize.previewer.trash();
                    }
                } );
            } );

            api.control.add( new api.PreviewLinkControl( 'changeset_preview_link', {
                section: section.id,
                priority: 100
            } ) );

            /**
             * Return whether the publish settings section should be active.
             *
             * @return {boolean} Is section active.
             */
            isSectionActive = function() {
                if ( ! api.state( 'activated' ).get() ) {
                    return false;
                }
                if ( api.state( 'trashing' ).get() || 'trash' === api.state( 'changesetStatus' ).get() ) {
                    return false;
                }
                if ( '' === api.state( 'changesetStatus' ).get() && api.state( 'saved' ).get() ) {
                    return false;
                }
                return true;
            };

            // Make sure publish settings are not available while the theme is not active and the customizer is in a published state.
            section.active.validate = isSectionActive;
            updateSectionActive = function() {
                section.active.set( isSectionActive() );
            };
            api.state( 'activated' ).bind( updateSectionActive );
            api.state( 'trashing' ).bind( updateSectionActive );
            api.state( 'saved' ).bind( updateSectionActive );
            api.state( 'changesetStatus' ).bind( updateSectionActive );
            updateSectionActive();

            // Bind visibility of the publish settings button to whether the section is active.
            updateButtonsState = function() {
                publishSettingsBtn.toggle( section.active.get() );
                saveBtn.toggleClass( 'has-next-sibling', section.active.get() );
            };
            updateButtonsState();
            section.active.bind( updateButtonsState );

            function highlightScheduleButton() {
                if ( ! cancelScheduleButtonReminder ) {
                    cancelScheduleButtonReminder = api.utils.highlightButton( btnWrapper, {
                        delay: 1000,

                        /*
                         * Only abort the reminder when the save button is focused.
                         * If the user clicks the settings button to toggle the
                         * settings closed, we'll still remind them.
                         */
                        focusTarget: saveBtn
                    } );
                }
            }
            function cancelHighlightScheduleButton() {
                if ( cancelScheduleButtonReminder ) {
                    cancelScheduleButtonReminder();
                    cancelScheduleButtonReminder = null;
                }
            }
            api.state( 'selectedChangesetStatus' ).bind( cancelHighlightScheduleButton );

            section.contentContainer.find( '.customize-action' ).text( api.l10n.updating );
            section.contentContainer.find( '.customize-section-back' ).removeAttr( 'tabindex' );
            publishSettingsBtn.prop( 'disabled', false );

            publishSettingsBtn.on( 'click', function( event ) {
                event.preventDefault();
                section.expanded.set( ! section.expanded.get() );
            } );

            section.expanded.bind( function( isExpanded ) {
                var defaultChangesetStatus;
                publishSettingsBtn.attr( 'aria-expanded', String( isExpanded ) );
                publishSettingsBtn.toggleClass( 'active', isExpanded );

                if ( isExpanded ) {
                    cancelHighlightScheduleButton();
                    return;
                }

                defaultChangesetStatus = api.state( 'changesetStatus' ).get();
                if ( '' === defaultChangesetStatus || 'auto-draft' === defaultChangesetStatus ) {
                    defaultChangesetStatus = 'publish';
                }

                if ( api.state( 'selectedChangesetStatus' ).get() !== defaultChangesetStatus ) {
                    highlightScheduleButton();
                } else if ( 'future' === api.state( 'selectedChangesetStatus' ).get() && api.state( 'selectedChangesetDate' ).get() !== api.state( 'changesetDate' ).get() ) {
                    highlightScheduleButton();
                }
            } );

            statusControl = new api.Control( 'changeset_status', {
                priority: 10,
                type: 'radio',
                section: 'publish_settings',
                setting: api.state( 'selectedChangesetStatus' ),
                templateId: 'customize-selected-changeset-status-control',
                label: api.l10n.action,
                choices: api.settings.changeset.statusChoices
            } );
            api.control.add( statusControl );

            dateControl = new api.DateTimeControl( 'changeset_scheduled_date', {
                priority: 20,
                section: 'publish_settings',
                setting: api.state( 'selectedChangesetDate' ),
                minYear: ( new Date() ).getFullYear(),
                allowPastDate: false,
                includeTime: true,
                twelveHourFormat: /a/i.test( api.settings.timeFormat ),
                description: api.l10n.scheduleDescription
            } );
            dateControl.notifications.alt = true;
            api.control.add( dateControl );

            publishWhenTime = function() {
                api.state( 'selectedChangesetStatus' ).set( 'publish' );
                api.previewer.save();
            };

            // Start countdown for when the dateTime arrives, or clear interval when it is .
            updateTimeArrivedPoller = function() {
                var shouldPoll = (
                    'future' === api.state( 'changesetStatus' ).get() &&
                    'future' === api.state( 'selectedChangesetStatus' ).get() &&
                    api.state( 'changesetDate' ).get() &&
                    api.state( 'selectedChangesetDate' ).get() === api.state( 'changesetDate' ).get() &&
                    api.utils.getRemainingTime( api.state( 'changesetDate' ).get() ) >= 0
                );

                if ( shouldPoll && ! pollInterval ) {
                    pollInterval = setInterval( function() {
                        var remainingTime = api.utils.getRemainingTime( api.state( 'changesetDate' ).get() );
                        api.state( 'remainingTimeToPublish' ).set( remainingTime );
                        if ( remainingTime <= 0 ) {
                            clearInterval( pollInterval );
                            pollInterval = 0;
                            publishWhenTime();
                        }
                    }, timeArrivedPollingInterval );
                } else if ( ! shouldPoll && pollInterval ) {
                    clearInterval( pollInterval );
                    pollInterval = 0;
                }
            };

            api.state( 'changesetDate' ).bind( updateTimeArrivedPoller );
            api.state( 'selectedChangesetDate' ).bind( updateTimeArrivedPoller );
            api.state( 'changesetStatus' ).bind( updateTimeArrivedPoller );
            api.state( 'selectedChangesetStatus' ).bind( updateTimeArrivedPoller );
            updateTimeArrivedPoller();

            // Ensure dateControl only appears when selected status is future.
            dateControl.active.validate = function() {
                return 'future' === api.state( 'selectedChangesetStatus' ).get();
            };
            toggleDateControl = function( value ) {
                dateControl.active.set( 'future' === value );
            };
            toggleDateControl( api.state( 'selectedChangesetStatus' ).get() );
            api.state( 'selectedChangesetStatus' ).bind( toggleDateControl );

            // Show notification on date control when status is future but it isn't a future date.
            api.state( 'saving' ).bind( function( isSaving ) {
                if ( isSaving && 'future' === api.state( 'selectedChangesetStatus' ).get() ) {
                    dateControl.toggleFutureDateNotification( ! dateControl.isFutureDate() );
                }
            } );
        } );

        // Prevent the form from saving when enter is pressed on an input or select element.
        $('#customize-controls').on( 'keydown', function( e ) {
            var isEnter = ( 13 === e.which ),
                $el = $( e.target );

            if ( isEnter && ( $el.is( 'input:not([type=button])' ) || $el.is( 'select' ) ) ) {
                e.preventDefault();
            }
        });

        // Expand/Collapse the main customizer customize info.
        $( '.customize-info' ).find( '> .accordion-section-title .customize-help-toggle' ).on( 'click', function() {
            var section = $( this ).closest( '.accordion-section' ),
                content = section.find( '.customize-panel-description:first' );

            if ( section.hasClass( 'cannot-expand' ) ) {
                return;
            }

            if ( section.hasClass( 'open' ) ) {
                section.toggleClass( 'open' );
                content.slideUp( api.Panel.prototype.defaultExpandedArguments.duration, function() {
                    content.trigger( 'toggled' );
                } );
                $( this ).attr( 'aria-expanded', false );
            } else {
                content.slideDown( api.Panel.prototype.defaultExpandedArguments.duration, function() {
                    content.trigger( 'toggled' );
                } );
                section.toggleClass( 'open' );
                $( this ).attr( 'aria-expanded', true );
            }
        });

        /**
         * Initialize Previewer
         *
         * @alias wp.customize.previewer
         */
        api.previewer = new api.Previewer({
            container:   '#customize-preview',
            form:        '#customize-controls',
            previewUrl:  api.settings.url.preview,
            allowedUrls: api.settings.url.allowed
        },/** @lends wp.customize.previewer */{

            nonce: api.settings.nonce,

            /**
             * Build the query to send along with the Preview request.
             *
             * @since 3.4.0
             * @since 4.7.0 Added options param.
             * @access public
             *
             * @param {Object}  [options] Options.
             * @param {boolean} [options.excludeCustomizedSaved=false] Exclude saved settings in customized response (values pending writing to changeset).
             * @return {Object} Query vars.
             */
            query: function( options ) {
                var queryVars = {
                    wp_customize: 'on',
                    customize_theme: api.settings.theme.stylesheet,
                    nonce: this.nonce.preview,
                    customize_changeset_uuid: api.settings.changeset.uuid
                };
                if ( api.settings.changeset.autosaved || ! api.state( 'saved' ).get() ) {
                    queryVars.customize_autosaved = 'on';
                }

                /*
                 * Exclude customized data if requested especially for calls to requestChangesetUpdate.
                 * Changeset updates are differential and so it is a performance waste to send all of
                 * the dirty settings with each update.
                 */
                queryVars.customized = JSON.stringify( api.dirtyValues( {
                    unsaved: options && options.excludeCustomizedSaved
                } ) );

                return queryVars;
            },

            /**
             * Save (and publish) the customizer changeset.
             *
             * Updates to the changeset are transactional. If any of the settings
             * are invalid then none of them will be written into the changeset.
             * A revision will be made for the changeset post if revisions support
             * has been added to the post type.
             *
             * @since 3.4.0
             * @since 4.7.0 Added args param and return value.
             *
             * @param {Object} [args] Args.
             * @param {string} [args.status=publish] Status.
             * @param {string} [args.date] Date, in local time in MySQL format.
             * @param {string} [args.title] Title
             * @return {jQuery.promise} Promise.
             */
            save: function( args ) {
                var previewer = this,
                    deferred = $.Deferred(),
                    changesetStatus = api.state( 'selectedChangesetStatus' ).get(),
                    selectedChangesetDate = api.state( 'selectedChangesetDate' ).get(),
                    processing = api.state( 'processing' ),
                    submitWhenDoneProcessing,
                    submit,
                    modifiedWhileSaving = {},
                    invalidSettings = [],
                    invalidControls = [],
                    invalidSettingLessControls = [];

                if ( args && args.status ) {
                    changesetStatus = args.status;
                }

                if ( api.state( 'saving' ).get() ) {
                    deferred.reject( 'already_saving' );
                    deferred.promise();
                }

                api.state( 'saving' ).set( true );

                function captureSettingModifiedDuringSave( setting ) {
                    modifiedWhileSaving[ setting.id ] = true;
                }

                submit = function () {
                    var request, query, settingInvalidities = {}, latestRevision = api._latestRevision, errorCode = 'client_side_error';

                    api.bind( 'change', captureSettingModifiedDuringSave );
                    api.notifications.remove( errorCode );

                    /*
                     * Block saving if there are any settings that are marked as
                     * invalid from the client (not from the server). Focus on
                     * the control.
                     */
                    api.each( function( setting ) {
                        setting.notifications.each( function( notification ) {
                            if ( 'error' === notification.type && ! notification.fromServer ) {
                                invalidSettings.push( setting.id );
                                if ( ! settingInvalidities[ setting.id ] ) {
                                    settingInvalidities[ setting.id ] = {};
                                }
                                settingInvalidities[ setting.id ][ notification.code ] = notification;
                            }
                        } );
                    } );

                    // Find all invalid setting less controls with notification type error.
                    api.control.each( function( control ) {
                        if ( ! control.setting || ! control.setting.id && control.active.get() ) {
                            control.notifications.each( function( notification ) {
                                if ( 'error' === notification.type ) {
                                    invalidSettingLessControls.push( [ control ] );
                                }
                            } );
                        }
                    } );

                    invalidControls = _.union( invalidSettingLessControls, _.values( api.findControlsForSettings( invalidSettings ) ) );
                    if ( ! _.isEmpty( invalidControls ) ) {

                        invalidControls[0][0].focus();
                        api.unbind( 'change', captureSettingModifiedDuringSave );

                        if ( invalidSettings.length ) {
                            api.notifications.add( new api.Notification( errorCode, {
                                message: ( 1 === invalidSettings.length ? api.l10n.saveBlockedError.singular : api.l10n.saveBlockedError.plural ).replace( /%s/g, String( invalidSettings.length ) ),
                                type: 'error',
                                dismissible: true,
                                saveFailure: true
                            } ) );
                        }

                        deferred.rejectWith( previewer, [
                            { setting_invalidities: settingInvalidities }
                        ] );
                        api.state( 'saving' ).set( false );
                        return deferred.promise();
                    }

                    /*
                     * Note that excludeCustomizedSaved is intentionally false so that the entire
                     * set of customized data will be included if bypassed changeset update.
                     */
                    query = $.extend( previewer.query( { excludeCustomizedSaved: false } ), {
                        nonce: previewer.nonce.save,
                        customize_changeset_status: changesetStatus
                    } );

                    if ( args && args.date ) {
                        query.customize_changeset_date = args.date;
                    } else if ( 'future' === changesetStatus && selectedChangesetDate ) {
                        query.customize_changeset_date = selectedChangesetDate;
                    }

                    if ( args && args.title ) {
                        query.customize_changeset_title = args.title;
                    }

                    // Allow plugins to modify the params included with the save request.
                    api.trigger( 'save-request-params', query );

                    /*
                     * Note that the dirty customized values will have already been set in the
                     * changeset and so technically query.customized could be deleted. However,
                     * it is remaining here to make sure that any settings that got updated
                     * quietly which may have not triggered an update request will also get
                     * included in the values that get saved to the changeset. This will ensure
                     * that values that get injected via the saved event will be included in
                     * the changeset. This also ensures that setting values that were invalid
                     * will get re-validated, perhaps in the case of settings that are invalid
                     * due to dependencies on other settings.
                     */
                    request = wp.ajax.post( 'customize_save', query );
                    api.state( 'processing' ).set( api.state( 'processing' ).get() + 1 );

                    api.trigger( 'save', request );

                    request.always( function () {
                        api.state( 'processing' ).set( api.state( 'processing' ).get() - 1 );
                        api.state( 'saving' ).set( false );
                        api.unbind( 'change', captureSettingModifiedDuringSave );
                    } );

                    // Remove notifications that were added due to save failures.
                    api.notifications.each( function( notification ) {
                        if ( notification.saveFailure ) {
                            api.notifications.remove( notification.code );
                        }
                    });

                    request.fail( function ( response ) {
                        var notification, notificationArgs;
                        notificationArgs = {
                            type: 'error',
                            dismissible: true,
                            fromServer: true,
                            saveFailure: true
                        };

                        if ( '0' === response ) {
                            response = 'not_logged_in';
                        } else if ( '-1' === response ) {
                            // Back-compat in case any other check_ajax_referer() call is dying.
                            response = 'invalid_nonce';
                        }

                        if ( 'invalid_nonce' === response ) {
                            previewer.cheatin();
                        } else if ( 'not_logged_in' === response ) {
                            previewer.preview.iframe.hide();
                            previewer.login().done( function() {
                                previewer.save();
                                previewer.preview.iframe.show();
                            } );
                        } else if ( response.code ) {
                            if ( 'not_future_date' === response.code && api.section.has( 'publish_settings' ) && api.section( 'publish_settings' ).active.get() && api.control.has( 'changeset_scheduled_date' ) ) {
                                api.control( 'changeset_scheduled_date' ).toggleFutureDateNotification( true ).focus();
                            } else if ( 'changeset_locked' !== response.code ) {
                                notification = new api.Notification( response.code, _.extend( notificationArgs, {
                                    message: response.message
                                } ) );
                            }
                        } else {
                            notification = new api.Notification( 'unknown_error', _.extend( notificationArgs, {
                                message: api.l10n.unknownRequestFail
                            } ) );
                        }

                        if ( notification ) {
                            api.notifications.add( notification );
                        }

                        if ( response.setting_validities ) {
                            api._handleSettingValidities( {
                                settingValidities: response.setting_validities,
                                focusInvalidControl: true
                            } );
                        }

                        deferred.rejectWith( previewer, [ response ] );
                        api.trigger( 'error', response );

                        // Start a new changeset if the underlying changeset was published.
                        if ( 'changeset_already_published' === response.code && response.next_changeset_uuid ) {
                            api.settings.changeset.uuid = response.next_changeset_uuid;
                            api.state( 'changesetStatus' ).set( '' );
                            if ( api.settings.changeset.branching ) {
                                parent.send( 'changeset-uuid', api.settings.changeset.uuid );
                            }
                            api.previewer.send( 'changeset-uuid', api.settings.changeset.uuid );
                        }
                    } );

                    request.done( function( response ) {

                        previewer.send( 'saved', response );

                        api.state( 'changesetStatus' ).set( response.changeset_status );
                        if ( response.changeset_date ) {
                            api.state( 'changesetDate' ).set( response.changeset_date );
                        }

                        if ( 'publish' === response.changeset_status ) {

                            // Mark all published as clean if they haven't been modified during the request.
                            api.each( function( setting ) {
                                /*
                                 * Note that the setting revision will be undefined in the case of setting
                                 * values that are marked as dirty when the customizer is loaded, such as
                                 * when applying starter content. All other dirty settings will have an
                                 * associated revision due to their modification triggering a change event.
                                 */
                                if ( setting._dirty && ( _.isUndefined( api._latestSettingRevisions[ setting.id ] ) || api._latestSettingRevisions[ setting.id ] <= latestRevision ) ) {
                                    setting._dirty = false;
                                }
                            } );

                            api.state( 'changesetStatus' ).set( '' );
                            api.settings.changeset.uuid = response.next_changeset_uuid;
                            if ( api.settings.changeset.branching ) {
                                parent.send( 'changeset-uuid', api.settings.changeset.uuid );
                            }
                        }

                        // Prevent subsequent requestChangesetUpdate() calls from including the settings that have been saved.
                        api._lastSavedRevision = Math.max( latestRevision, api._lastSavedRevision );

                        if ( response.setting_validities ) {
                            api._handleSettingValidities( {
                                settingValidities: response.setting_validities,
                                focusInvalidControl: true
                            } );
                        }

                        deferred.resolveWith( previewer, [ response ] );
                        api.trigger( 'saved', response );

                        // Restore the global dirty state if any settings were modified during save.
                        if ( ! _.isEmpty( modifiedWhileSaving ) ) {
                            api.state( 'saved' ).set( false );
                        }
                    } );
                };

                if ( 0 === processing() ) {
                    submit();
                } else {
                    submitWhenDoneProcessing = function () {
                        if ( 0 === processing() ) {
                            api.state.unbind( 'change', submitWhenDoneProcessing );
                            submit();
                        }
                    };
                    api.state.bind( 'change', submitWhenDoneProcessing );
                }

                return deferred.promise();
            },

            /**
             * Trash the current changes.
             *
             * Revert the Customizer to its previously-published state.
             *
             * @since 4.9.0
             *
             * @return {jQuery.promise} Promise.
             */
            trash: function trash() {
                var request, success, fail;

                api.state( 'trashing' ).set( true );
                api.state( 'processing' ).set( api.state( 'processing' ).get() + 1 );

                request = wp.ajax.post( 'customize_trash', {
                    customize_changeset_uuid: api.settings.changeset.uuid,
                    nonce: api.settings.nonce.trash
                } );
                api.notifications.add( new api.OverlayNotification( 'changeset_trashing', {
                    type: 'info',
                    message: api.l10n.revertingChanges,
                    loading: true
                } ) );

                success = function() {
                    var urlParser = document.createElement( 'a' ), queryParams;

                    api.state( 'changesetStatus' ).set( 'trash' );
                    api.each( function( setting ) {
                        setting._dirty = false;
                    } );
                    api.state( 'saved' ).set( true );

                    // Go back to Customizer without changeset.
                    urlParser.href = location.href;
                    queryParams = api.utils.parseQueryString( urlParser.search.substr( 1 ) );
                    delete queryParams.changeset_uuid;
                    queryParams['return'] = api.settings.url['return'];
                    urlParser.search = $.param( queryParams );
                    location.replace( urlParser.href );
                };

                fail = function( code, message ) {
                    var notificationCode = code || 'unknown_error';
                    api.state( 'processing' ).set( api.state( 'processing' ).get() - 1 );
                    api.state( 'trashing' ).set( false );
                    api.notifications.remove( 'changeset_trashing' );
                    api.notifications.add( new api.Notification( notificationCode, {
                        message: message || api.l10n.unknownError,
                        dismissible: true,
                        type: 'error'
                    } ) );
                };

                request.done( function( response ) {
                    success( response.message );
                } );

                request.fail( function( response ) {
                    var code = response.code || 'trashing_failed';
                    if ( response.success || 'non_existent_changeset' === code || 'changeset_already_trashed' === code ) {
                        success( response.message );
                    } else {
                        fail( code, response.message );
                    }
                } );
            },

            /**
             * Builds the front preview URL with the current state of customizer.
             *
             * @since 4.9.0
             *
             * @return {string} Preview URL.
             */
            getFrontendPreviewUrl: function() {
                var previewer = this, params, urlParser;
                urlParser = document.createElement( 'a' );
                urlParser.href = previewer.previewUrl.get();
                params = api.utils.parseQueryString( urlParser.search.substr( 1 ) );

                if ( api.state( 'changesetStatus' ).get() && 'publish' !== api.state( 'changesetStatus' ).get() ) {
                    params.customize_changeset_uuid = api.settings.changeset.uuid;
                }
                if ( ! api.state( 'activated' ).get() ) {
                    params.customize_theme = api.settings.theme.stylesheet;
                }

                urlParser.search = $.param( params );
                return urlParser.href;
            }
        });

        // Ensure preview nonce is included with every customized request, to allow post data to be read.
        $.ajaxPrefilter( function injectPreviewNonce( options ) {
            if ( ! /wp_customize=on/.test( options.data ) ) {
                return;
            }
            options.data += '&' + $.param({
                customize_preview_nonce: api.settings.nonce.preview
            });
        });

        // Refresh the nonces if the preview sends updated nonces over.
        api.previewer.bind( 'nonce', function( nonce ) {
            $.extend( this.nonce, nonce );
        });

        // Refresh the nonces if login sends updated nonces over.
        api.bind( 'nonce-refresh', function( nonce ) {
            $.extend( api.settings.nonce, nonce );
            $.extend( api.previewer.nonce, nonce );
            api.previewer.send( 'nonce-refresh', nonce );
        });

        // Create Settings.
        $.each( api.settings.settings, function( id, data ) {
            var Constructor = api.settingConstructor[ data.type ] || api.Setting;
            api.add( new Constructor( id, data.value, {
                transport: data.transport,
                previewer: api.previewer,
                dirty: !! data.dirty
            } ) );
        });

        // Create Panels.
        $.each( api.settings.panels, function ( id, data ) {
            var Constructor = api.panelConstructor[ data.type ] || api.Panel, options;
            // Inclusion of params alias is for back-compat for custom panels that expect to augment this property.
            options = _.extend( { params: data }, data );
            api.panel.add( new Constructor( id, options ) );
        });

        // Create Sections.
        $.each( api.settings.sections, function ( id, data ) {
            var Constructor = api.sectionConstructor[ data.type ] || api.Section, options;
            // Inclusion of params alias is for back-compat for custom sections that expect to augment this property.
            options = _.extend( { params: data }, data );
            api.section.add( new Constructor( id, options ) );
        });

        // Create Controls.
        $.each( api.settings.controls, function( id, data ) {
            var Constructor = api.controlConstructor[ data.type ] || api.Control, options;
            // Inclusion of params alias is for back-compat for custom controls that expect to augment this property.
            options = _.extend( { params: data }, data );
            api.control.add( new Constructor( id, options ) );
        });

        // Focus the autofocused element.
        _.each( [ 'panel', 'section', 'control' ], function( type ) {
            var id = api.settings.autofocus[ type ];
            if ( ! id ) {
                return;
            }

            /*
             * Defer focus until:
             * 1. The panel, section, or control exists (especially for dynamically-created ones).
             * 2. The instance is embedded in the document (and so is focusable).
             * 3. The preview has finished loading so that the active states have been set.
             */
            api[ type ]( id, function( instance ) {
                instance.deferred.embedded.done( function() {
                    api.previewer.deferred.active.done( function() {
                        instance.focus();
                    });
                });
            });
        });

        api.bind( 'ready', api.reflowPaneContents );
        $( [ api.panel, api.section, api.control ] ).each( function ( i, values ) {
            var debouncedReflowPaneContents = _.debounce( api.reflowPaneContents, api.settings.timeouts.reflowPaneContents );
            values.bind( 'add', debouncedReflowPaneContents );
            values.bind( 'change', debouncedReflowPaneContents );
            values.bind( 'remove', debouncedReflowPaneContents );
        } );

        // Set up global notifications area.
        api.bind( 'ready', function setUpGlobalNotificationsArea() {
            var sidebar, containerHeight, containerInitialTop;
            api.notifications.container = $( '#customize-notifications-area' );

            api.notifications.bind( 'change', _.debounce( function() {
                api.notifications.render();
            } ) );

            sidebar = $( '.wp-full-overlay-sidebar-content' );
            api.notifications.bind( 'rendered', function updateSidebarTop() {
                sidebar.css( 'top', '' );
                if ( 0 !== api.notifications.count() ) {
                    containerHeight = api.notifications.container.outerHeight() + 1;
                    containerInitialTop = parseInt( sidebar.css( 'top' ), 10 );
                    sidebar.css( 'top', containerInitialTop + containerHeight + 'px' );
                }
                api.notifications.trigger( 'sidebarTopUpdated' );
            });

            api.notifications.render();
        });

        // Save and activated states.
        (function( state ) {
            var saved = state.instance( 'saved' ),
                saving = state.instance( 'saving' ),
                trashing = state.instance( 'trashing' ),
                activated = state.instance( 'activated' ),
                processing = state.instance( 'processing' ),
                paneVisible = state.instance( 'paneVisible' ),
                expandedPanel = state.instance( 'expandedPanel' ),
                expandedSection = state.instance( 'expandedSection' ),
                changesetStatus = state.instance( 'changesetStatus' ),
                selectedChangesetStatus = state.instance( 'selectedChangesetStatus' ),
                changesetDate = state.instance( 'changesetDate' ),
                selectedChangesetDate = state.instance( 'selectedChangesetDate' ),
                previewerAlive = state.instance( 'previewerAlive' ),
                editShortcutVisibility  = state.instance( 'editShortcutVisibility' ),
                changesetLocked = state.instance( 'changesetLocked' ),
                populateChangesetUuidParam, defaultSelectedChangesetStatus;

            state.bind( 'change', function() {
                var canSave;

                if ( ! activated() ) {
                    saveBtn.val( api.l10n.activate );
                    closeBtn.find( '.screen-reader-text' ).text( api.l10n.cancel );

                } else if ( '' === changesetStatus.get() && saved() ) {
                    if ( api.settings.changeset.currentUserCanPublish ) {
                        saveBtn.val( api.l10n.published );
                    } else {
                        saveBtn.val( api.l10n.saved );
                    }
                    closeBtn.find( '.screen-reader-text' ).text( api.l10n.close );

                } else {
                    if ( 'draft' === selectedChangesetStatus() ) {
                        if ( saved() && selectedChangesetStatus() === changesetStatus() ) {
                            saveBtn.val( api.l10n.draftSaved );
                        } else {
                            saveBtn.val( api.l10n.saveDraft );
                        }
                    } else if ( 'future' === selectedChangesetStatus() ) {
                        if ( saved() && selectedChangesetStatus() === changesetStatus() ) {
                            if ( changesetDate.get() !== selectedChangesetDate.get() ) {
                                saveBtn.val( api.l10n.schedule );
                            } else {
                                saveBtn.val( api.l10n.scheduled );
                            }
                        } else {
                            saveBtn.val( api.l10n.schedule );
                        }
                    } else if ( api.settings.changeset.currentUserCanPublish ) {
                        saveBtn.val( api.l10n.publish );
                    }
                    closeBtn.find( '.screen-reader-text' ).text( api.l10n.cancel );
                }

                /*
                 * Save (publish) button should be enabled if saving is not currently happening,
                 * and if the theme is not active or the changeset exists but is not published.
                 */
                canSave = ! saving() && ! trashing() && ! changesetLocked() && ( ! activated() || ! saved() || ( changesetStatus() !== selectedChangesetStatus() && '' !== changesetStatus() ) || ( 'future' === selectedChangesetStatus() && changesetDate.get() !== selectedChangesetDate.get() ) );

                saveBtn.prop( 'disabled', ! canSave );
            });

            selectedChangesetStatus.validate = function( status ) {
                if ( '' === status || 'auto-draft' === status ) {
                    return null;
                }
                return status;
            };

            defaultSelectedChangesetStatus = api.settings.changeset.currentUserCanPublish ? 'publish' : 'draft';

            // Set default states.
            changesetStatus( api.settings.changeset.status );
            changesetLocked( Boolean( api.settings.changeset.lockUser ) );
            changesetDate( api.settings.changeset.publishDate );
            selectedChangesetDate( api.settings.changeset.publishDate );
            selectedChangesetStatus( '' === api.settings.changeset.status || 'auto-draft' === api.settings.changeset.status ? defaultSelectedChangesetStatus : api.settings.changeset.status );
            selectedChangesetStatus.link( changesetStatus ); // Ensure that direct updates to status on server via wp.customizer.previewer.save() will update selection.
            saved( true );
            if ( '' === changesetStatus() ) { // Handle case for loading starter content.
                api.each( function( setting ) {
                    if ( setting._dirty ) {
                        saved( false );
                    }
                } );
            }
            saving( false );
            activated( api.settings.theme.active );
            processing( 0 );
            paneVisible( true );
            expandedPanel( false );
            expandedSection( false );
            previewerAlive( true );
            editShortcutVisibility( 'visible' );

            api.bind( 'change', function() {
                if ( state( 'saved' ).get() ) {
                    state( 'saved' ).set( false );
                }
            });

            // Populate changeset UUID param when state becomes dirty.
            if ( api.settings.changeset.branching ) {
                saved.bind( function( isSaved ) {
                    if ( ! isSaved ) {
                        populateChangesetUuidParam( true );
                    }
                });
            }

            saving.bind( function( isSaving ) {
                body.toggleClass( 'saving', isSaving );
            } );
            trashing.bind( function( isTrashing ) {
                body.toggleClass( 'trashing', isTrashing );
            } );

            api.bind( 'saved', function( response ) {
                state('saved').set( true );
                if ( 'publish' === response.changeset_status ) {
                    state( 'activated' ).set( true );
                }
            });

            activated.bind( function( to ) {
                if ( to ) {
                    api.trigger( 'activated' );
                }
            });

            /**
             * Populate URL with UUID via `history.replaceState()`.
             *
             * @since 4.7.0
             * @access private
             *
             * @param {boolean} isIncluded Is UUID included.
             * @return {void}
             */
            populateChangesetUuidParam = function( isIncluded ) {
                var urlParser, queryParams;

                // Abort on IE9 which doesn't support history management.
                if ( ! history.replaceState ) {
                    return;
                }

                urlParser = document.createElement( 'a' );
                urlParser.href = location.href;
                queryParams = api.utils.parseQueryString( urlParser.search.substr( 1 ) );
                if ( isIncluded ) {
                    if ( queryParams.changeset_uuid === api.settings.changeset.uuid ) {
                        return;
                    }
                    queryParams.changeset_uuid = api.settings.changeset.uuid;
                } else {
                    if ( ! queryParams.changeset_uuid ) {
                        return;
                    }
                    delete queryParams.changeset_uuid;
                }
                urlParser.search = $.param( queryParams );
                history.replaceState( {}, document.title, urlParser.href );
            };

            // Show changeset UUID in URL when in branching mode and there is a saved changeset.
            if ( api.settings.changeset.branching ) {
                changesetStatus.bind( function( newStatus ) {
                    populateChangesetUuidParam( '' !== newStatus && 'publish' !== newStatus && 'trash' !== newStatus );
                } );
            }
        }( api.state ) );

        /**
         * Handles lock notice and take over request.
         *
         * @since 4.9.0
         */
        ( function checkAndDisplayLockNotice() {

            var LockedNotification = api.OverlayNotification.extend(/** @lends wp.customize~LockedNotification.prototype */{

                /**
                 * Template ID.
                 *
                 * @type {string}
                 */
                templateId: 'customize-changeset-locked-notification',

                /**
                 * Lock user.
                 *
                 * @type {object}
                 */
                lockUser: null,

                /**
                 * A notification that is displayed in a full-screen overlay with information about the locked changeset.
                 *
                 * @constructs wp.customize~LockedNotification
                 * @augments   wp.customize.OverlayNotification
                 *
                 * @since 4.9.0
                 *
                 * @param {string} [code] - Code.
                 * @param {Object} [params] - Params.
                 */
                initialize: function( code, params ) {
                    var notification = this, _code, _params;
                    _code = code || 'changeset_locked';
                    _params = _.extend(
                        {
                            message: '',
                            type: 'warning',
                            containerClasses: '',
                            lockUser: {}
                        },
                        params
                    );
                    _params.containerClasses += ' notification-changeset-locked';
                    api.OverlayNotification.prototype.initialize.call( notification, _code, _params );
                },

                /**
                 * Render notification.
                 *
                 * @since 4.9.0
                 *
                 * @return {jQuery} Notification container.
                 */
                render: function() {
                    var notification = this, li, data, takeOverButton, request;
                    data = _.extend(
                        {
                            allowOverride: false,
                            returnUrl: api.settings.url['return'],
                            previewUrl: api.previewer.previewUrl.get(),
                            frontendPreviewUrl: api.previewer.getFrontendPreviewUrl()
                        },
                        this
                    );

                    li = api.OverlayNotification.prototype.render.call( data );

                    // Try to autosave the changeset now.
                    api.requestChangesetUpdate( {}, { autosave: true } ).fail( function( response ) {
                        if ( ! response.autosaved ) {
                            li.find( '.notice-error' ).prop( 'hidden', false ).text( response.message || api.l10n.unknownRequestFail );
                        }
                    } );

                    takeOverButton = li.find( '.customize-notice-take-over-button' );
                    takeOverButton.on( 'click', function( event ) {
                        event.preventDefault();
                        if ( request ) {
                            return;
                        }

                        takeOverButton.addClass( 'disabled' );
                        request = wp.ajax.post( 'customize_override_changeset_lock', {
                            wp_customize: 'on',
                            customize_theme: api.settings.theme.stylesheet,
                            customize_changeset_uuid: api.settings.changeset.uuid,
                            nonce: api.settings.nonce.override_lock
                        } );

                        request.done( function() {
                            api.notifications.remove( notification.code ); // Remove self.
                            api.state( 'changesetLocked' ).set( false );
                        } );

                        request.fail( function( response ) {
                            var message = response.message || api.l10n.unknownRequestFail;
                            li.find( '.notice-error' ).prop( 'hidden', false ).text( message );

                            request.always( function() {
                                takeOverButton.removeClass( 'disabled' );
                            } );
                        } );

                        request.always( function() {
                            request = null;
                        } );
                    } );

                    return li;
                }
            });

            /**
             * Start lock.
             *
             * @since 4.9.0
             *
             * @param {Object} [args] - Args.
             * @param {Object} [args.lockUser] - Lock user data.
             * @param {boolean} [args.allowOverride=false] - Whether override is allowed.
             * @return {void}
             */
            function startLock( args ) {
                if ( args && args.lockUser ) {
                    api.settings.changeset.lockUser = args.lockUser;
                }
                api.state( 'changesetLocked' ).set( true );
                api.notifications.add( new LockedNotification( 'changeset_locked', {
                    lockUser: api.settings.changeset.lockUser,
                    allowOverride: Boolean( args && args.allowOverride )
                } ) );
            }

            // Show initial notification.
            if ( api.settings.changeset.lockUser ) {
                startLock( { allowOverride: true } );
            }

            // Check for lock when sending heartbeat requests.
            $( document ).on( 'heartbeat-send.update_lock_notice', function( event, data ) {
                data.check_changeset_lock = true;
                data.changeset_uuid = api.settings.changeset.uuid;
            } );

            // Handle heartbeat ticks.
            $( document ).on( 'heartbeat-tick.update_lock_notice', function( event, data ) {
                var notification, code = 'changeset_locked';
                if ( ! data.customize_changeset_lock_user ) {
                    return;
                }

                // Update notification when a different user takes over.
                notification = api.notifications( code );
                if ( notification && notification.lockUser.id !== api.settings.changeset.lockUser.id ) {
                    api.notifications.remove( code );
                }

                startLock( {
                    lockUser: data.customize_changeset_lock_user
                } );
            } );

            // Handle locking in response to changeset save errors.
            api.bind( 'error', function( response ) {
                if ( 'changeset_locked' === response.code && response.lock_user ) {
                    startLock( {
                        lockUser: response.lock_user
                    } );
                }
            } );
        } )();

        // Set up initial notifications.
        (function() {
            var removedQueryParams = [], autosaveDismissed = false;

            /**
             * Obtain the URL to restore the autosave.
             *
             * @return {string} Customizer URL.
             */
            function getAutosaveRestorationUrl() {
                var urlParser, queryParams;
                urlParser = document.createElement( 'a' );
                urlParser.href = location.href;
                queryParams = api.utils.parseQueryString( urlParser.search.substr( 1 ) );
                if ( api.settings.changeset.latestAutoDraftUuid ) {
                    queryParams.changeset_uuid = api.settings.changeset.latestAutoDraftUuid;
                } else {
                    queryParams.customize_autosaved = 'on';
                }
                queryParams['return'] = api.settings.url['return'];
                urlParser.search = $.param( queryParams );
                return urlParser.href;
            }

            /**
             * Remove parameter from the URL.
             *
             * @param {Array} params - Parameter names to remove.
             * @return {void}
             */
            function stripParamsFromLocation( params ) {
                var urlParser = document.createElement( 'a' ), queryParams, strippedParams = 0;
                urlParser.href = location.href;
                queryParams = api.utils.parseQueryString( urlParser.search.substr( 1 ) );
                _.each( params, function( param ) {
                    if ( 'undefined' !== typeof queryParams[ param ] ) {
                        strippedParams += 1;
                        delete queryParams[ param ];
                    }
                } );
                if ( 0 === strippedParams ) {
                    return;
                }

                urlParser.search = $.param( queryParams );
                history.replaceState( {}, document.title, urlParser.href );
            }

            /**
             * Displays a Site Editor notification when a block theme is activated.
             *
             * @since 4.9.0
             *
             * @param {string} [notification] - A notification to display.
             * @return {void}
             */
            function addSiteEditorNotification( notification ) {
                api.notifications.add( new api.Notification( 'site_editor_block_theme_notice', {
                    message: notification,
                    type: 'info',
                    dismissible: false,
                    render: function() {
                        var notification = api.Notification.prototype.render.call( this ),
                            button = notification.find( 'button.switch-to-editor' );

                        button.on( 'click', function( event ) {
                            event.preventDefault();
                            location.assign( button.data( 'action' ) );
                        } );

                        return notification;
                    }
                } ) );
            }

            /**
             * Dismiss autosave.
             *
             * @return {void}
             */
            function dismissAutosave() {
                if ( autosaveDismissed ) {
                    return;
                }
                wp.ajax.post( 'customize_dismiss_autosave_or_lock', {
                    wp_customize: 'on',
                    customize_theme: api.settings.theme.stylesheet,
                    customize_changeset_uuid: api.settings.changeset.uuid,
                    nonce: api.settings.nonce.dismiss_autosave_or_lock,
                    dismiss_autosave: true
                } );
                autosaveDismissed = true;
            }

            /**
             * Add notification regarding the availability of an autosave to restore.
             *
             * @return {void}
             */
            function addAutosaveRestoreNotification() {
                var code = 'autosave_available', onStateChange;

                // Since there is an autosave revision and the user hasn't loaded with autosaved, add notification to prompt to load autosaved version.
                api.notifications.add( new api.Notification( code, {
                    message: api.l10n.autosaveNotice,
                    type: 'warning',
                    dismissible: true,
                    render: function() {
                        var li = api.Notification.prototype.render.call( this ), link;

                        // Handle clicking on restoration link.
                        link = li.find( 'a' );
                        link.prop( 'href', getAutosaveRestorationUrl() );
                        link.on( 'click', function( event ) {
                            event.preventDefault();
                            location.replace( getAutosaveRestorationUrl() );
                        } );

                        // Handle dismissal of notice.
                        li.find( '.notice-dismiss' ).on( 'click', dismissAutosave );

                        return li;
                    }
                } ) );

                // Remove the notification once the user starts making changes.
                onStateChange = function() {
                    dismissAutosave();
                    api.notifications.remove( code );
                    api.unbind( 'change', onStateChange );
                    api.state( 'changesetStatus' ).unbind( onStateChange );
                };
                api.bind( 'change', onStateChange );
                api.state( 'changesetStatus' ).bind( onStateChange );
            }

            if ( api.settings.changeset.autosaved ) {
                api.state( 'saved' ).set( false );
                removedQueryParams.push( 'customize_autosaved' );
            }
            if ( ! api.settings.changeset.branching && ( ! api.settings.changeset.status || 'auto-draft' === api.settings.changeset.status ) ) {
                removedQueryParams.push( 'changeset_uuid' ); // Remove UUID when restoring autosave auto-draft.
            }
            if ( removedQueryParams.length > 0 ) {
                stripParamsFromLocation( removedQueryParams );
            }
            if ( api.settings.changeset.latestAutoDraftUuid || api.settings.changeset.hasAutosaveRevision ) {
                addAutosaveRestoreNotification();
            }
            var shouldDisplayBlockThemeNotification = !! parseInt( $( '#customize-info' ).data( 'block-theme' ), 10 );
            if (shouldDisplayBlockThemeNotification) {
                addSiteEditorNotification( api.l10n.blockThemeNotification );
            }
        })();

        // Check if preview url is valid and load the preview frame.
        if ( api.previewer.previewUrl() ) {
            api.previewer.refresh();
        } else {
            api.previewer.previewUrl( api.settings.url.home );
        }

        // Button bindings.
        saveBtn.on( 'click', function( event ) {
            api.previewer.save();
            event.preventDefault();
        }).on( 'keydown', function( event ) {
            if ( 9 === event.which ) { // Tab.
                return;
            }
            if ( 13 === event.which ) { // Enter.
                api.previewer.save();
            }
            event.preventDefault();
        });

        closeBtn.on( 'keydown', function( event ) {
            if ( 9 === event.which ) { // Tab.
                return;
            }
            if ( 13 === event.which ) { // Enter.
                this.click();
            }
            event.preventDefault();
        });

        $( '.collapse-sidebar' ).on( 'click', function() {
            api.state( 'paneVisible' ).set( ! api.state( 'paneVisible' ).get() );
        });

        api.state( 'paneVisible' ).bind( function( paneVisible ) {
            overlay.toggleClass( 'preview-only', ! paneVisible );
            overlay.toggleClass( 'expanded', paneVisible );
            overlay.toggleClass( 'collapsed', ! paneVisible );

            if ( ! paneVisible ) {
                $( '.collapse-sidebar' ).attr({ 'aria-expanded': 'false', 'aria-label': api.l10n.expandSidebar });
            } else {
                $( '.collapse-sidebar' ).attr({ 'aria-expanded': 'true', 'aria-label': api.l10n.collapseSidebar });
            }
        });

        // Keyboard shortcuts - esc to exit section/panel.
        body.on( 'keydown', function( event ) {
            var collapsedObject, expandedControls = [], expandedSections = [], expandedPanels = [];

            if ( 27 !== event.which ) { // Esc.
                return;
            }

            /*
             * Abort if the event target is not the body (the default) and not inside of #customize-controls.
             * This ensures that ESC meant to collapse a modal dialog or a TinyMCE toolbar won't collapse something else.
             */
            if ( ! $( event.target ).is( 'body' ) && ! $.contains( $( '#customize-controls' )[0], event.target ) ) {
                return;
            }

            // Abort if we're inside of a block editor instance.
            if ( event.target.closest( '.block-editor-writing-flow' ) !== null ||
                event.target.closest( '.block-editor-block-list__block-popover' ) !== null
            ) {
                return;
            }

            // Check for expanded expandable controls (e.g. widgets and nav menus items), sections, and panels.
            api.control.each( function( control ) {
                if ( control.expanded && control.expanded() && _.isFunction( control.collapse ) ) {
                    expandedControls.push( control );
                }
            });
            api.section.each( function( section ) {
                if ( section.expanded() ) {
                    expandedSections.push( section );
                }
            });
            api.panel.each( function( panel ) {
                if ( panel.expanded() ) {
                    expandedPanels.push( panel );
                }
            });

            // Skip collapsing expanded controls if there are no expanded sections.
            if ( expandedControls.length > 0 && 0 === expandedSections.length ) {
                expandedControls.length = 0;
            }

            // Collapse the most granular expanded object.
            collapsedObject = expandedControls[0] || expandedSections[0] || expandedPanels[0];
            if ( collapsedObject ) {
                if ( 'themes' === collapsedObject.params.type ) {

                    // Themes panel or section.
                    if ( body.hasClass( 'modal-open' ) ) {
                        collapsedObject.closeDetails();
                    } else if ( api.panel.has( 'themes' ) ) {

                        // If we're collapsing a section, collapse the panel also.
                        api.panel( 'themes' ).collapse();
                    }
                    return;
                }
                collapsedObject.collapse();
                event.preventDefault();
            }
        });

        $( '.customize-controls-preview-toggle' ).on( 'click', function() {
            api.state( 'paneVisible' ).set( ! api.state( 'paneVisible' ).get() );
        });

        /*
         * Sticky header feature.
         */
        (function initStickyHeaders() {
            var parentContainer = $( '.wp-full-overlay-sidebar-content' ),
                changeContainer, updateHeaderHeight, releaseStickyHeader, resetStickyHeader, positionStickyHeader,
                activeHeader, lastScrollTop;

            /**
             * Determine which panel or section is currently expanded.
             *
             * @since 4.7.0
             * @access private
             *
             * @param {wp.customize.Panel|wp.customize.Section} container Construct.
             * @return {void}
             */
            changeContainer = function( container ) {
                var newInstance = container,
                    expandedSection = api.state( 'expandedSection' ).get(),
                    expandedPanel = api.state( 'expandedPanel' ).get(),
                    headerElement;

                if ( activeHeader && activeHeader.element ) {
                    // Release previously active header element.
                    releaseStickyHeader( activeHeader.element );

                    // Remove event listener in the previous panel or section.
                    activeHeader.element.find( '.description' ).off( 'toggled', updateHeaderHeight );
                }

                if ( ! newInstance ) {
                    if ( ! expandedSection && expandedPanel && expandedPanel.contentContainer ) {
                        newInstance = expandedPanel;
                    } else if ( ! expandedPanel && expandedSection && expandedSection.contentContainer ) {
                        newInstance = expandedSection;
                    } else {
                        activeHeader = false;
                        return;
                    }
                }

                headerElement = newInstance.contentContainer.find( '.customize-section-title, .panel-meta' ).first();
                if ( headerElement.length ) {
                    activeHeader = {
                        instance: newInstance,
                        element:  headerElement,
                        parent:   headerElement.closest( '.customize-pane-child' ),
                        height:   headerElement.outerHeight()
                    };

                    // Update header height whenever help text is expanded or collapsed.
                    activeHeader.element.find( '.description' ).on( 'toggled', updateHeaderHeight );

                    if ( expandedSection ) {
                        resetStickyHeader( activeHeader.element, activeHeader.parent );
                    }
                } else {
                    activeHeader = false;
                }
            };
            api.state( 'expandedSection' ).bind( changeContainer );
            api.state( 'expandedPanel' ).bind( changeContainer );

            // Throttled scroll event handler.
            parentContainer.on( 'scroll', _.throttle( function() {
                if ( ! activeHeader ) {
                    return;
                }

                var scrollTop = parentContainer.scrollTop(),
                    scrollDirection;

                if ( ! lastScrollTop ) {
                    scrollDirection = 1;
                } else {
                    if ( scrollTop === lastScrollTop ) {
                        scrollDirection = 0;
                    } else if ( scrollTop > lastScrollTop ) {
                        scrollDirection = 1;
                    } else {
                        scrollDirection = -1;
                    }
                }
                lastScrollTop = scrollTop;
                if ( 0 !== scrollDirection ) {
                    positionStickyHeader( activeHeader, scrollTop, scrollDirection );
                }
            }, 8 ) );

            // Update header position on sidebar layout change.
            api.notifications.bind( 'sidebarTopUpdated', function() {
                if ( activeHeader && activeHeader.element.hasClass( 'is-sticky' ) ) {
                    activeHeader.element.css( 'top', parentContainer.css( 'top' ) );
                }
            });

            // Release header element if it is sticky.
            releaseStickyHeader = function( headerElement ) {
                if ( ! headerElement.hasClass( 'is-sticky' ) ) {
                    return;
                }
                headerElement
                    .removeClass( 'is-sticky' )
                    .addClass( 'maybe-sticky is-in-view' )
                    .css( 'top', parentContainer.scrollTop() + 'px' );
            };

            // Reset position of the sticky header.
            resetStickyHeader = function( headerElement, headerParent ) {
                if ( headerElement.hasClass( 'is-in-view' ) ) {
                    headerElement
                        .removeClass( 'maybe-sticky is-in-view' )
                        .css( {
                            width: '',
                            top:   ''
                        } );
                    headerParent.css( 'padding-top', '' );
                }
            };

            /**
             * Update active header height.
             *
             * @since 4.7.0
             * @access private
             *
             * @return {void}
             */
            updateHeaderHeight = function() {
                activeHeader.height = activeHeader.element.outerHeight();
            };

            /**
             * Reposition header on throttled `scroll` event.
             *
             * @since 4.7.0
             * @access private
             *
             * @param {Object} header - Header.
             * @param {number} scrollTop - Scroll top.
             * @param {number} scrollDirection - Scroll direction, negative number being up and positive being down.
             * @return {void}
             */
            positionStickyHeader = function( header, scrollTop, scrollDirection ) {
                var headerElement = header.element,
                    headerParent = header.parent,
                    headerHeight = header.height,
                    headerTop = parseInt( headerElement.css( 'top' ), 10 ),
                    maybeSticky = headerElement.hasClass( 'maybe-sticky' ),
                    isSticky = headerElement.hasClass( 'is-sticky' ),
                    isInView = headerElement.hasClass( 'is-in-view' ),
                    isScrollingUp = ( -1 === scrollDirection );

                // When scrolling down, gradually hide sticky header.
                if ( ! isScrollingUp ) {
                    if ( isSticky ) {
                        headerTop = scrollTop;
                        headerElement
                            .removeClass( 'is-sticky' )
                            .css( {
                                top:   headerTop + 'px',
                                width: ''
                            } );
                    }
                    if ( isInView && scrollTop > headerTop + headerHeight ) {
                        headerElement.removeClass( 'is-in-view' );
                        headerParent.css( 'padding-top', '' );
                    }
                    return;
                }

                // Scrolling up.
                if ( ! maybeSticky && scrollTop >= headerHeight ) {
                    maybeSticky = true;
                    headerElement.addClass( 'maybe-sticky' );
                } else if ( 0 === scrollTop ) {
                    // Reset header in base position.
                    headerElement
                        .removeClass( 'maybe-sticky is-in-view is-sticky' )
                        .css( {
                            top:   '',
                            width: ''
                        } );
                    headerParent.css( 'padding-top', '' );
                    return;
                }

                if ( isInView && ! isSticky ) {
                    // Header is in the view but is not yet sticky.
                    if ( headerTop >= scrollTop ) {
                        // Header is fully visible.
                        headerElement
                            .addClass( 'is-sticky' )
                            .css( {
                                top:   parentContainer.css( 'top' ),
                                width: headerParent.outerWidth() + 'px'
                            } );
                    }
                } else if ( maybeSticky && ! isInView ) {
                    // Header is out of the view.
                    headerElement
                        .addClass( 'is-in-view' )
                        .css( 'top', ( scrollTop - headerHeight ) + 'px' );
                    headerParent.css( 'padding-top', headerHeight + 'px' );
                }
            };
        }());

        // Previewed device bindings. (The api.previewedDevice property
        // is how this Value was first introduced, but since it has moved to api.state.)
        api.previewedDevice = api.state( 'previewedDevice' );

        // Set the default device.
        api.bind( 'ready', function() {
            _.find( api.settings.previewableDevices, function( value, key ) {
                if ( true === value['default'] ) {
                    api.previewedDevice.set( key );
                    return true;
                }
            } );
        } );

        // Set the toggled device.
        footerActions.find( '.devices button' ).on( 'click', function( event ) {
            api.previewedDevice.set( $( event.currentTarget ).data( 'device' ) );
        });

        // Bind device changes.
        api.previewedDevice.bind( function( newDevice ) {
            var overlay = $( '.wp-full-overlay' ),
                devices = '';

            footerActions.find( '.devices button' )
                .removeClass( 'active' )
                .attr( 'aria-pressed', false );

            footerActions.find( '.devices .preview-' + newDevice )
                .addClass( 'active' )
                .attr( 'aria-pressed', true );

            $.each( api.settings.previewableDevices, function( device ) {
                devices += ' preview-' + device;
            } );

            overlay
                .removeClass( devices )
                .addClass( 'preview-' + newDevice );
        } );

        // Bind site title display to the corresponding field.
        if ( title.length ) {
            api( 'blogname', function( setting ) {
                var updateTitle = function() {
                    var blogTitle = setting() || '';
                    title.text( blogTitle.toString().trim() || api.l10n.untitledBlogName );
                };
                setting.bind( updateTitle );
                updateTitle();
            } );
        }

        /*
         * Create a postMessage connection with a parent frame,
         * in case the Customizer frame was opened with the Customize loader.
         *
         * @see wp.customize.Loader
         */
        parent = new api.Messenger({
            url: api.settings.url.parent,
            channel: 'loader'
        });

        // Handle exiting of Customizer.
        (function() {
            var isInsideIframe = false;

            function isCleanState() {
                var defaultChangesetStatus;

                /*
                 * Handle special case of previewing theme switch since some settings (for nav menus and widgets)
                 * are pre-dirty and non-active themes can only ever be auto-drafts.
                 */
                if ( ! api.state( 'activated' ).get() ) {
                    return 0 === api._latestRevision;
                }

                // Dirty if the changeset status has been changed but not saved yet.
                defaultChangesetStatus = api.state( 'changesetStatus' ).get();
                if ( '' === defaultChangesetStatus || 'auto-draft' === defaultChangesetStatus ) {
                    defaultChangesetStatus = 'publish';
                }
                if ( api.state( 'selectedChangesetStatus' ).get() !== defaultChangesetStatus ) {
                    return false;
                }

                // Dirty if scheduled but the changeset date hasn't been saved yet.
                if ( 'future' === api.state( 'selectedChangesetStatus' ).get() && api.state( 'selectedChangesetDate' ).get() !== api.state( 'changesetDate' ).get() ) {
                    return false;
                }

                return api.state( 'saved' ).get() && 'auto-draft' !== api.state( 'changesetStatus' ).get();
            }

            /*
             * If we receive a 'back' event, we're inside an iframe.
             * Send any clicks to the 'Return' link to the parent page.
             */
            parent.bind( 'back', function() {
                isInsideIframe = true;
            });

            function startPromptingBeforeUnload() {
                api.unbind( 'change', startPromptingBeforeUnload );
                api.state( 'selectedChangesetStatus' ).unbind( startPromptingBeforeUnload );
                api.state( 'selectedChangesetDate' ).unbind( startPromptingBeforeUnload );

                // Prompt user with AYS dialog if leaving the Customizer with unsaved changes.
                $( window ).on( 'beforeunload.customize-confirm', function() {
                    if ( ! isCleanState() && ! api.state( 'changesetLocked' ).get() ) {
                        setTimeout( function() {
                            overlay.removeClass( 'customize-loading' );
                        }, 1 );
                        return api.l10n.saveAlert;
                    }
                });
            }
            api.bind( 'change', startPromptingBeforeUnload );
            api.state( 'selectedChangesetStatus' ).bind( startPromptingBeforeUnload );
            api.state( 'selectedChangesetDate' ).bind( startPromptingBeforeUnload );

            function requestClose() {
                var clearedToClose = $.Deferred(), dismissAutoSave = false, dismissLock = false;

                if ( isCleanState() ) {
                    dismissLock = true;
                } else if ( confirm( api.l10n.saveAlert ) ) {

                    dismissLock = true;

                    // Mark all settings as clean to prevent another call to requestChangesetUpdate.
                    api.each( function( setting ) {
                        setting._dirty = false;
                    });
                    $( document ).off( 'visibilitychange.wp-customize-changeset-update' );
                    $( window ).off( 'beforeunload.wp-customize-changeset-update' );

                    closeBtn.css( 'cursor', 'progress' );
                    if ( '' !== api.state( 'changesetStatus' ).get() ) {
                        dismissAutoSave = true;
                    }
                } else {
                    clearedToClose.reject();
                }

                if ( dismissLock || dismissAutoSave ) {
                    wp.ajax.send( 'customize_dismiss_autosave_or_lock', {
                        timeout: 500, // Don't wait too long.
                        data: {
                            wp_customize: 'on',
                            customize_theme: api.settings.theme.stylesheet,
                            customize_changeset_uuid: api.settings.changeset.uuid,
                            nonce: api.settings.nonce.dismiss_autosave_or_lock,
                            dismiss_autosave: dismissAutoSave,
                            dismiss_lock: dismissLock
                        }
                    } ).always( function() {
                        clearedToClose.resolve();
                    } );
                }

                return clearedToClose.promise();
            }

            parent.bind( 'confirm-close', function() {
                requestClose().done( function() {
                    parent.send( 'confirmed-close', true );
                } ).fail( function() {
                    parent.send( 'confirmed-close', false );
                } );
            } );

            closeBtn.on( 'click.customize-controls-close', function( event ) {
                event.preventDefault();
                if ( isInsideIframe ) {
                    parent.send( 'close' ); // See confirm-close logic above.
                } else {
                    requestClose().done( function() {
                        $( window ).off( 'beforeunload.customize-confirm' );
                        window.location.href = closeBtn.prop( 'href' );
                    } );
                }
            });
        })();

        // Pass events through to the parent.
        $.each( [ 'saved', 'change' ], function ( i, event ) {
            api.bind( event, function() {
                parent.send( event );
            });
        } );

        // Pass titles to the parent.
        api.bind( 'title', function( newTitle ) {
            parent.send( 'title', newTitle );
        });

        if ( api.settings.changeset.branching ) {
            parent.send( 'changeset-uuid', api.settings.changeset.uuid );
        }

        // Initialize the connection with the parent frame.
        parent.send( 'ready' );

        // Control visibility for default controls.
        $.each({
            'background_image': {
                controls: [ 'background_preset', 'background_position', 'background_size', 'background_repeat', 'background_attachment' ],
                callback: function( to ) { return !! to; }
            },
            'show_on_front': {
                controls: [ 'page_on_front', 'page_for_posts' ],
                callback: function( to ) { return 'page' === to; }
            },
            'header_textcolor': {
                controls: [ 'header_textcolor' ],
                callback: function( to ) { return 'blank' !== to; }
            }
        }, function( settingId, o ) {
            api( settingId, function( setting ) {
                $.each( o.controls, function( i, controlId ) {
                    api.control( controlId, function( control ) {
                        var visibility = function( to ) {
                            control.container.toggle( o.callback( to ) );
                        };

                        visibility( setting.get() );
                        setting.bind( visibility );
                    });
                });
            });
        });

        api.control( 'background_preset', function( control ) {
            var visibility, defaultValues, values, toggleVisibility, updateSettings, preset;

            visibility = { // position, size, repeat, attachment.
                'default': [ false, false, false, false ],
                'fill': [ true, false, false, false ],
                'fit': [ true, false, true, false ],
                'repeat': [ true, false, false, true ],
                'custom': [ true, true, true, true ]
            };

            defaultValues = [
                _wpCustomizeBackground.defaults['default-position-x'],
                _wpCustomizeBackground.defaults['default-position-y'],
                _wpCustomizeBackground.defaults['default-size'],
                _wpCustomizeBackground.defaults['default-repeat'],
                _wpCustomizeBackground.defaults['default-attachment']
            ];

            values = { // position_x, position_y, size, repeat, attachment.
                'default': defaultValues,
                'fill': [ 'left', 'top', 'cover', 'no-repeat', 'fixed' ],
                'fit': [ 'left', 'top', 'contain', 'no-repeat', 'fixed' ],
                'repeat': [ 'left', 'top', 'auto', 'repeat', 'scroll' ]
            };

            // @todo These should actually toggle the active state,
            // but without the preview overriding the state in data.activeControls.
            toggleVisibility = function( preset ) {
                _.each( [ 'background_position', 'background_size', 'background_repeat', 'background_attachment' ], function( controlId, i ) {
                    var control = api.control( controlId );
                    if ( control ) {
                        control.container.toggle( visibility[ preset ][ i ] );
                    }
                } );
            };

            updateSettings = function( preset ) {
                _.each( [ 'background_position_x', 'background_position_y', 'background_size', 'background_repeat', 'background_attachment' ], function( settingId, i ) {
                    var setting = api( settingId );
                    if ( setting ) {
                        setting.set( values[ preset ][ i ] );
                    }
                } );
            };

            preset = control.setting.get();
            toggleVisibility( preset );

            control.setting.bind( 'change', function( preset ) {
                toggleVisibility( preset );
                if ( 'custom' !== preset ) {
                    updateSettings( preset );
                }
            } );
        } );

        api.control( 'background_repeat', function( control ) {
            control.elements[0].unsync( api( 'background_repeat' ) );

            control.element = new api.Element( control.container.find( 'input' ) );
            control.element.set( 'no-repeat' !== control.setting() );

            control.element.bind( function( to ) {
                control.setting.set( to ? 'repeat' : 'no-repeat' );
            } );

            control.setting.bind( function( to ) {
                control.element.set( 'no-repeat' !== to );
            } );
        } );

        api.control( 'background_attachment', function( control ) {
            control.elements[0].unsync( api( 'background_attachment' ) );

            control.element = new api.Element( control.container.find( 'input' ) );
            control.element.set( 'fixed' !== control.setting() );

            control.element.bind( function( to ) {
                control.setting.set( to ? 'scroll' : 'fixed' );
            } );

            control.setting.bind( function( to ) {
                control.element.set( 'fixed' !== to );
            } );
        } );

        // Juggle the two controls that use header_textcolor.
        api.control( 'display_header_text', function( control ) {
            var last = '';

            control.elements[0].unsync( api( 'header_textcolor' ) );

            control.element = new api.Element( control.container.find('input') );
            control.element.set( 'blank' !== control.setting() );

            control.element.bind( function( to ) {
                if ( ! to ) {
                    last = api( 'header_textcolor' ).get();
                }

                control.setting.set( to ? last : 'blank' );
            });

            control.setting.bind( function( to ) {
                control.element.set( 'blank' !== to );
            });
        });

        // Add behaviors to the static front page controls.
        api( 'show_on_front', 'page_on_front', 'page_for_posts', function( showOnFront, pageOnFront, pageForPosts ) {
            var handleChange = function() {
                var setting = this, pageOnFrontId, pageForPostsId, errorCode = 'show_on_front_page_collision';
                pageOnFrontId = parseInt( pageOnFront(), 10 );
                pageForPostsId = parseInt( pageForPosts(), 10 );

                if ( 'page' === showOnFront() ) {

                    // Change previewed URL to the homepage when changing the page_on_front.
                    if ( setting === pageOnFront && pageOnFrontId > 0 ) {
                        api.previewer.previewUrl.set( api.settings.url.home );
                    }

                    // Change the previewed URL to the selected page when changing the page_for_posts.
                    if ( setting === pageForPosts && pageForPostsId > 0 ) {
                        api.previewer.previewUrl.set( api.settings.url.home + '?page_id=' + pageForPostsId );
                    }
                }

                // Toggle notification when the homepage and posts page are both set and the same.
                if ( 'page' === showOnFront() && pageOnFrontId && pageForPostsId && pageOnFrontId === pageForPostsId ) {
                    showOnFront.notifications.add( new api.Notification( errorCode, {
                        type: 'error',
                        message: api.l10n.pageOnFrontError
                    } ) );
                } else {
                    showOnFront.notifications.remove( errorCode );
                }
            };
            showOnFront.bind( handleChange );
            pageOnFront.bind( handleChange );
            pageForPosts.bind( handleChange );
            handleChange.call( showOnFront, showOnFront() ); // Make sure initial notification is added after loading existing changeset.

            // Move notifications container to the bottom.
            api.control( 'show_on_front', function( showOnFrontControl ) {
                showOnFrontControl.deferred.embedded.done( function() {
                    showOnFrontControl.container.append( showOnFrontControl.getNotificationsContainerElement() );
                });
            });
        });

        // Add code editor for Custom CSS.
        (function() {
            var sectionReady = $.Deferred();

            api.section( 'custom_css', function( section ) {
                section.deferred.embedded.done( function() {
                    if ( section.expanded() ) {
                        sectionReady.resolve( section );
                    } else {
                        section.expanded.bind( function( isExpanded ) {
                            if ( isExpanded ) {
                                sectionReady.resolve( section );
                            }
                        } );
                    }
                });
            });

            // Set up the section description behaviors.
            sectionReady.done( function setupSectionDescription( section ) {
                var control = api.control( 'custom_css' );

                // Hide redundant label for visual users.
                control.container.find( '.customize-control-title:first' ).addClass( 'screen-reader-text' );

                // Close the section description when clicking the close button.
                section.container.find( '.section-description-buttons .section-description-close' ).on( 'click', function() {
                    section.container.find( '.section-meta .customize-section-description:first' )
                        .removeClass( 'open' )
                        .slideUp();

                    section.container.find( '.customize-help-toggle' )
                        .attr( 'aria-expanded', 'false' )
                        .focus(); // Avoid focus loss.
                });

                // Reveal help text if setting is empty.
                if ( control && ! control.setting.get() ) {
                    section.container.find( '.section-meta .customize-section-description:first' )
                        .addClass( 'open' )
                        .show()
                        .trigger( 'toggled' );

                    section.container.find( '.customize-help-toggle' ).attr( 'aria-expanded', 'true' );
                }
            });
        })();

        // Toggle visibility of Header Video notice when active state change.
        api.control( 'header_video', function( headerVideoControl ) {
            headerVideoControl.deferred.embedded.done( function() {
                var toggleNotice = function() {
                    var section = api.section( headerVideoControl.section() ), noticeCode = 'video_header_not_available';
                    if ( ! section ) {
                        return;
                    }
                    if ( headerVideoControl.active.get() ) {
                        section.notifications.remove( noticeCode );
                    } else {
                        section.notifications.add( new api.Notification( noticeCode, {
                            type: 'info',
                            message: api.l10n.videoHeaderNotice
                        } ) );
                    }
                };
                toggleNotice();
                headerVideoControl.active.bind( toggleNotice );
            } );
        } );

        // Update the setting validities.
        api.previewer.bind( 'selective-refresh-setting-validities', function handleSelectiveRefreshedSettingValidities( settingValidities ) {
            api._handleSettingValidities( {
                settingValidities: settingValidities,
                focusInvalidControl: false
            } );
        } );

        // Focus on the control that is associated with the given setting.
        api.previewer.bind( 'focus-control-for-setting', function( settingId ) {
            var matchedControls = [];
            api.control.each( function( control ) {
                var settingIds = _.pluck( control.settings, 'id' );
                if ( -1 !== _.indexOf( settingIds, settingId ) ) {
                    matchedControls.push( control );
                }
            } );

            // Focus on the matched control with the lowest priority (appearing higher).
            if ( matchedControls.length ) {
                matchedControls.sort( function( a, b ) {
                    return a.priority() - b.priority();
                } );
                matchedControls[0].focus();
            }
        } );

        // Refresh the preview when it requests.
        api.previewer.bind( 'refresh', function() {
            api.previewer.refresh();
        });

        // Update the edit shortcut visibility state.
        api.state( 'paneVisible' ).bind( function( isPaneVisible ) {
            var isMobileScreen;
            if ( window.matchMedia ) {
                isMobileScreen = window.matchMedia( 'screen and ( max-width: 640px )' ).matches;
            } else {
                isMobileScreen = $( window ).width() <= 640;
            }
            api.state( 'editShortcutVisibility' ).set( isPaneVisible || isMobileScreen ? 'visible' : 'hidden' );
        } );
        if ( window.matchMedia ) {
            window.matchMedia( 'screen and ( max-width: 640px )' ).addListener( function() {
                var state = api.state( 'paneVisible' );
                state.callbacks.fireWith( state, [ state.get(), state.get() ] );
            } );
        }
        api.previewer.bind( 'edit-shortcut-visibility', function( visibility ) {
            api.state( 'editShortcutVisibility' ).set( visibility );
        } );
        api.state( 'editShortcutVisibility' ).bind( function( visibility ) {
            api.previewer.send( 'edit-shortcut-visibility', visibility );
        } );

        // Autosave changeset.
        function startAutosaving() {
            var timeoutId, updateChangesetWithReschedule, scheduleChangesetUpdate, updatePending = false;

            api.unbind( 'change', startAutosaving ); // Ensure startAutosaving only fires once.

            function onChangeSaved( isSaved ) {
                if ( ! isSaved && ! api.settings.changeset.autosaved ) {
                    api.settings.changeset.autosaved = true; // Once a change is made then autosaving kicks in.
                    api.previewer.send( 'autosaving' );
                }
            }
            api.state( 'saved' ).bind( onChangeSaved );
            onChangeSaved( api.state( 'saved' ).get() );

            /**
             * Request changeset update and then re-schedule the next changeset update time.
             *
             * @since 4.7.0
             * @private
             */
            updateChangesetWithReschedule = function() {
                if ( ! updatePending ) {
                    updatePending = true;
                    api.requestChangesetUpdate( {}, { autosave: true } ).always( function() {
                        updatePending = false;
                    } );
                }
                scheduleChangesetUpdate();
            };

            /**
             * Schedule changeset update.
             *
             * @since 4.7.0
             * @private
             */
            scheduleChangesetUpdate = function() {
                clearTimeout( timeoutId );
                timeoutId = setTimeout( function() {
                    updateChangesetWithReschedule();
                }, api.settings.timeouts.changesetAutoSave );
            };

            // Start auto-save interval for updating changeset.
            scheduleChangesetUpdate();

            // Save changeset when focus removed from window.
            $( document ).on( 'visibilitychange.wp-customize-changeset-update', function() {
                if ( document.hidden ) {
                    updateChangesetWithReschedule();
                }
            } );

            // Save changeset before unloading window.
            $( window ).on( 'beforeunload.wp-customize-changeset-update', function() {
                updateChangesetWithReschedule();
            } );
        }
        api.bind( 'change', startAutosaving );

        // Make sure TinyMCE dialogs appear above Customizer UI.
        $( document ).one( 'tinymce-editor-setup', function() {
            if ( window.tinymce.ui.FloatPanel && ( ! window.tinymce.ui.FloatPanel.zIndex || window.tinymce.ui.FloatPanel.zIndex < 500001 ) ) {
                window.tinymce.ui.FloatPanel.zIndex = 500001;
            }
        } );

        body.addClass( 'ready' );
        api.trigger( 'ready' );
    });

})( wp, jQuery );