    /**
     * @class Ext.state.Stateful
     * A mixin for being able to save the state of an object to an underlying
     * {@link Ext.state.Provider}.
     */
    Ext.define('Ext.state.Stateful', {

        /* Begin Definitions */

       mixins: {
            observable: 'Ext.util.Observable'
        },

        requires: ['Ext.state.Manager'],

        /* End Definitions */

        /**
         * @cfg {Boolean} stateful
         * <p>A flag which causes the object to attempt to restore the state of
         * internal properties from a saved state on startup. The object must have
         * a <code>{@link #stateId}</code> for state to be managed.
         * Auto-generated ids are not guaranteed to be stable across page loads and
         * cannot be relied upon to save and restore the same state for a object.<p>
         * <p>For state saving to work, the state manager's provider must have been
         * set to an implementation of {@link Ext.state.Provider} which overrides the
         * {@link Ext.state.Provider#set set} and {@link Ext.state.Provider#get get}
         * methods to save and recall name/value pairs. A built-in implementation,
         * {@link Ext.state.CookieProvider} is available.</p>
         * <p>To set the state provider for the current page:</p>
         * <pre><code>
    Ext.state.Manager.setProvider(new Ext.state.CookieProvider({
        expires: new Date(new Date().getTime()+(1000*60*60*24*7)), //7 days from now
    }));
         * </code></pre>
         * <p>A stateful object attempts to save state when one of the events
         * listed in the <code>{@link #stateEvents}</code> configuration fires.</p>
         * <p>To save state, a stateful object first serializes its state by
         * calling <b><code>{@link #getState}</code></b>. By default, this function does
         * nothing. The developer must provide an implementation which returns an
         * object hash which represents the restorable state of the object.</p>
         * <p>The value yielded by getState is passed to {@link Ext.state.Manager#set}
         * which uses the configured {@link Ext.state.Provider} to save the object
         * keyed by the <code>{@link #stateId}</code></p>.
         * <p>During construction, a stateful object attempts to <i>restore</i>
         * its state by calling {@link Ext.state.Manager#get} passing the
         * <code>{@link #stateId}</code></p>
         * <p>The resulting object is passed to <b><code>{@link #applyState}</code></b>.
         * The default implementation of <code>{@link #applyState}</code> simply copies
         * properties into the object, but a developer may override this to support
         * more behaviour.</p>
         * <p>You can perform extra processing on state save and restore by attaching
         * handlers to the {@link #beforestaterestore}, {@link #staterestore},
         * {@link #beforestatesave} and {@link #statesave} events.</p>
         */
        stateful: true,

        /**
         * @cfg {String} stateId
         * The unique id for this object to use for state management purposes.
         * <p>See {@link #stateful} for an explanation of saving and restoring state.</p>
         */

        /**
         * @cfg {Array} stateEvents
         * <p>An array of events that, when fired, should trigger this object to
         * save its state (defaults to none). <code>stateEvents</code> may be any type
         * of event supported by this object, including browser or custom events
         * (e.g., <tt>['click', 'customerchange']</tt>).</p>
         * <p>See <code>{@link #stateful}</code> for an explanation of saving and
         * restoring object state.</p>
         */

        /**
         * @cfg {Number} saveBuffer A buffer to be applied if many state events are fired within
         * a short period. Defaults to 100.
         */
        saveDelay: 100,

        autoGenIdRe: /^((\w+-)|(ext-comp-))\d{4,}$/i,

        constructor: function(config) {
            var me = this;

            config = config || {};
            if (Ext.isDefined(config.stateful)) {
                me.stateful = config.stateful;
            }
            if (Ext.isDefined(config.saveDelay)) {
                me.saveDelay = config.saveDelay;
            }
            me.stateId = me.stateId || config.stateId;

            if (!me.stateEvents) {
                me.stateEvents = [];
            }
            if (config.stateEvents) {
                me.stateEvents.concat(config.stateEvents);
            }
            this.addEvents(
                /**
                 * @event beforestaterestore
                 * Fires before the state of the object is restored. Return false from an event handler to stop the restore.
                 * @param {Ext.state.Stateful} this
                 * @param {Object} state The hash of state values returned from the StateProvider. If this
                 * event is not vetoed, then the state object is passed to <b><tt>applyState</tt></b>. By default,
                 * that simply copies property values into this object. The method maybe overriden to
                 * provide custom state restoration.
                 */
                'beforestaterestore',

                /**
                 * @event staterestore
                 * Fires after the state of the object is restored.
                 * @param {Ext.state.Stateful} this
                 * @param {Object} state The hash of state values returned from the StateProvider. This is passed
                 * to <b><tt>applyState</tt></b>. By default, that simply copies property values into this
                 * object. The method maybe overriden to provide custom state restoration.
                 */
                'staterestore',

                /**
                 * @event beforestatesave
                 * Fires before the state of the object is saved to the configured state provider. Return false to stop the save.
                 * @param {Ext.state.Stateful} this
                 * @param {Object} state The hash of state values. This is determined by calling
                 * <b><tt>getState()</tt></b> on the object. This method must be provided by the
                 * developer to return whetever representation of state is required, by default, Ext.state.Stateful
                 * has a null implementation.
                 */
                'beforestatesave',

                /**
                 * @event statesave
                 * Fires after the state of the object is saved to the configured state provider.
                 * @param {Ext.state.Stateful} this
                 * @param {Object} state The hash of state values. This is determined by calling
                 * <b><tt>getState()</tt></b> on the object. This method must be provided by the
                 * developer to return whetever representation of state is required, by default, Ext.state.Stateful
                 * has a null implementation.
                 */
                'statesave'
            );
            me.mixins.observable.constructor.call(me);
            if (me.stateful !== false) {
                me.initStateEvents();
                me.initState();
            }
        },

        /**
         * Initializes any state events for this object.
         * @private
         */
        initStateEvents: function() {
            this.addStateEvents(this.stateEvents);
        },

        /**
         * Add events that will trigger the state to be saved.
         * @param {String/Array} events The event name or an array of event names.
         */
        addStateEvents: function(events){
            if (!Ext.isArray(events)) {
                events = [events];
            }

            var me = this,
                i = 0,
                len = events.length;

            for (; i < len; ++i) {
                me.on(events[i], me.onStateChange, me);
            }
        },

        /**
         * This method is called when any of the {@link #stateEvents} are fired.
         * @private
         */
        onStateChange: function(){
            var me = this,
                delay = me.saveDelay;

            if (delay > 0) {
                if (!me.stateTask) {
                    me.stateTask = Ext.create('Ext.util.DelayedTask', me.saveState, me);
                }
                me.stateTask.delay(me.saveDelay);
            } else {
                me.saveState();
            }
        },

        /**
         * Saves the state of the object to the persistence store.
         * @private
         */
        saveState: function() {
            var me = this,
                id,
                state;

            if (me.stateful !== false) {
                id = me.getStateId();
                if (id) {
                    state = me.getState();
                    if (me.fireEvent('beforestatesave', me, state) !== false) {
                        Ext.state.Manager.set(id, state);
                        me.fireEvent('statesave', me, state);
                    }
                }
            }
        },

        /**
         * Gets the current state of the object. By default this function returns null,
         * it should be overridden in subclasses to implement methods for getting the state.
         * @return {Object} The current state
         */
        getState: function(){
            return null;
        },

        /**
         * Applies the state to the object. This should be overridden in subclasses to do
         * more complex state operations. By default it applies the state properties onto
         * the current object.
         * @param {Object} state The state
         */
        applyState: function(state) {
            if (state) {
                Ext.apply(this, state);
            }
        },

        /**
         * Gets the state id for this object.
         * @return {String} The state id, null if not found.
         */
        getStateId: function() {
            var me = this,
                id = me.stateId;

            if (!id) {
                id = me.autoGenIdRe.test(String(me.id)) ? null : me.id;
            }
            return id;
        },

        /**
         * Initializes the state of the object upon construction.
         * @private
         */
        initState: function(){
            var me = this,
                id = me.getStateId(),
                state;

            if (me.stateful !== false) {
                if (id) {
                    state = Ext.state.Manager.get(id);
                    if (state) {
                        state = Ext.apply({}, state);
                        if (me.fireEvent('beforestaterestore', me, state) !== false) {
                            me.applyState(state);
                            me.fireEvent('staterestore', me, state);
                        }
                    }
                }
            }
        },

        /**
         * Destroys this stateful object.
         */
        destroy: function(){
            var task = this.stateTask;
            if (task) {
                task.cancel();
            }
            this.clearListeners();

        }

    });