    /**
     * @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
         * 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 {@link #stateId} 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.
         *
         * 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.
         *
         * To set the state provider for the current page:
         *
         *    Ext.state.Manager.setProvider(new Ext.state.CookieProvider({
         *        expires: new Date(new Date().getTime()+(1000*60*60*24*7)), //7 days from now
         *    }));
         *
         * A stateful object attempts to save state when one of the events
         * listed in the {@link #stateEvents} configuration fires.
         *
         * To save state, a stateful object first serializes its state by
         * calling *{@link #getState}*.
         *
         * The Component base class implements {@link #getState} to save its width and height within the state
         * only if they were initially configured, and have changed from the configured value.
         *
         * The Panel class saves its collapsed state in addition to that.
         *
         * The Grid class saves its column state in addition to its superclass state.
         *
         * If there is more application state to be save, the developer must provide an implementation which
         * first calls the superclass method to inherit the above behaviour, and then injects new properties
         * into the returned object.
         *
         * 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 {@link #stateId}.
         *
         * During construction, a stateful object attempts to *restore* its state by calling
         * {@link Ext.state.Manager#get} passing the {@link #stateId}
         *
         * The resulting object is passed to {@link #applyState}*. The default implementation of
         * {@link #applyState} simply copies properties into the object, but a developer may
         * override this to support restoration of more complex application state.
         *
         * 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.
         */
        stateful: false,

        /**
         * @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 {String[]} 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} saveDelay
         * A buffer to be applied if many state events are fired within a short period.
         */
        saveDelay: 100,

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

            config = config || {};
            if (config.stateful !== undefined) {
                me.stateful = config.stateful;
            }
            if (config.saveDelay !== undefined) {
                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.addStateEvents(me.stateEvents);
                me.initState();
            }
        },

        /**
         * Add events that will trigger the state to be saved. If the first argument is an
         * array, each element of that array is the name of a state event. Otherwise, each
         * argument passed to this method is the name of a state event.
         *
         * @param {String/String[]} events The event name or an array of event names.
         */
        addStateEvents: function (events) {
            var me = this,
                i, event, stateEventsByName;

            if (me.stateful && me.getStateId()) {
                if (typeof events == 'string') {
                    events = Array.prototype.slice.call(arguments, 0);
                }

                stateEventsByName = me.stateEventsByName || (me.stateEventsByName = {});

                for (i = events.length; i--; ) {
                    event = events[i];

                    if (!stateEventsByName[event]) {
                        stateEventsByName[event] = 1;
                        me.on(event, me.onStateChange, me);
                    }
                }
            }
        },

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

            if (!me.stateful) {
                return;
            }

            if (delay) {
                if (!me.stateTask) {
                    statics = Ext.state.Stateful;
                    runner = statics.runner || (statics.runner = new Ext.util.TaskRunner());

                    me.stateTask = runner.newTask({
                        run: me.saveState,
                        scope: me,
                        interval: delay,
                        repeat: 1
                    });
                }

                me.stateTask.start();
            } else {
                me.saveState();
            }
        },

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

            if (id) {
                state = me.getState() || {};    //pass along for custom interactions
                if (!hasListeners.beforestatesave || me.fireEvent('beforestatesave', me, state) !== false) {
                    Ext.state.Manager.set(id, state);
                    if (hasListeners.statesave) {
                        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 'stateId' or the implicit 'id' specified by component configuration.
         * @private
         */
        getStateId: function() {
            var me = this;
            return me.stateId || (me.autoGenId ? null : me.id);
        },

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

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

        /**
         * Conditionally saves a single property from this object to the given state object.
         * The idea is to only save state which has changed from the initial state so that
         * current software settings do not override future software settings. Only those
         * values that are user-changed state should be saved.
         *
         * @param {String} propName The name of the property to save.
         * @param {Object} state The state object in to which to save the property.
         * @param {String} stateName (optional) The name to use for the property in state.
         * @return {Boolean} True if the property was saved, false if not.
         */
        savePropToState: function (propName, state, stateName) {
            var me = this,
                value = me[propName],
                config = me.initialConfig;

            if (me.hasOwnProperty(propName)) {
                if (!config || config[propName] !== value) {
                    if (state) {
                        state[stateName || propName] = value;
                    }
                    return true;
                }
            }
            return false;
        },

        /**
         * Gathers additional named properties of the instance and adds their current values
         * to the passed state object.
         * @param {String/String[]} propNames The name (or array of names) of the property to save.
         * @param {Object} state The state object in to which to save the property values.
         * @return {Object} state
         */
        savePropsToState: function (propNames, state) {
            var me = this,
                i, n;

            if (typeof propNames == 'string') {
                me.savePropToState(propNames, state);
            } else {
                for (i = 0, n = propNames.length; i < n; ++i) {
                    me.savePropToState(propNames[i], state);
                }
            }

            return state;
        },

        /**
         * Destroys this stateful object.
         */
        destroy: function(){
            var me = this,
                task = me.stateTask;

            if (task) {
                task.destroy();
                me.stateTask = null;
            }

            me.clearListeners();
        }
    });