    // @tag dom,core
    // @require ../Support.js
    // @define Ext.util.DelayedTask

    /**
     * @class Ext.util.DelayedTask
     *
     * The DelayedTask class provides a convenient way to "buffer" the execution of a method,
     * performing setTimeout where a new timeout cancels the old timeout. When called, the
     * task will wait the specified time period before executing. If durng that time period,
     * the task is called again, the original call will be cancelled. This continues so that
     * the function is only called a single time for each iteration.
     *
     * This method is especially useful for things like detecting whether a user has finished
     * typing in a text field. An example would be performing validation on a keypress. You can
     * use this class to buffer the keypress events for a certain number of milliseconds, and
     * perform only if they stop for that amount of time.
     *
     * ## Usage
     *
     *     var task = new Ext.util.DelayedTask(function(){
     *         alert(Ext.getDom('myInputField').value.length);
     *     });
     *
     *     // Wait 500ms before calling our function. If the user presses another key
     *     // during that 500ms, it will be cancelled and we'll wait another 500ms.
     *     Ext.get('myInputField').on('keypress', function() {
     *         task.{@link #delay}(500);
     *     });
     *
     * Note that we are using a DelayedTask here to illustrate a point. The configuration
     * option `buffer` for {@link Ext.util.Observable#addListener addListener/on} will
     * also setup a delayed task for you to buffer events.
     *
     * @constructor The parameters to this constructor serve as defaults and are not required.
     * @param {Function} fn (optional) The default function to call. If not specified here, it must be specified during the {@link #delay} call.
     * @param {Object} scope (optional) The default scope (The **`this`** reference) in which the
     * function is called. If not specified, `this` will refer to the browser window.
     * @param {Array} args (optional) The default Array of arguments.
     * @param {Boolean} [cancelOnDelay=true] By default, each call to {@link #delay} cancels any pending invocation and reschedules a new
     * invocation. Specifying this as `false` means that calls to {@link #delay} when an invocation is pending just update the call settings,
     * `newDelay`, `newFn`, `newScope` or `newArgs`, whichever are passed.
     */
    Ext.util.DelayedTask = function(fn, scope, args, cancelOnDelay) {
        var me = this,
            delay,
            call = function() {
                clearInterval(me.id);
                me.id = null;
                fn.apply(scope, args || []);
                Ext.EventManager.idleEvent.fire();
            };

        cancelOnDelay = typeof cancelOnDelay === 'boolean' ? cancelOnDelay : true;

        /**
         * @property {Number} id
         * The id of the currently pending invocation.  Will be set to `null` if there is no
         * invocation pending.
         */
        me.id = null;

        /**
         * By default, cancels any pending timeout and queues a new one.
         *
         * If the `cancelOnDelay` parameter was specified as `false` in the constructor, this does not cancel and
         * reschedule, but just updates the call settings, `newDelay`, `newFn`, `newScope` or `newArgs`, whichever are passed.
         *
         * @param {Number} newDelay The milliseconds to delay
         * @param {Function} newFn (optional) Overrides function passed to constructor
         * @param {Object} newScope (optional) Overrides scope passed to constructor. Remember that if no scope
         * is specified, <code>this</code> will refer to the browser window.
         * @param {Array} newArgs (optional) Overrides args passed to constructor
         */
        me.delay = function(newDelay, newFn, newScope, newArgs) {
            if (cancelOnDelay) {
                me.cancel();
            }
            if (typeof newDelay === 'number') {
                delay = newDelay;
            }
            fn    = newFn    || fn;
            scope = newScope || scope;
            args  = newArgs  || args;
            if (!me.id) {
                me.id = setInterval(call, delay);
            }
        };

        /**
         * Cancel the last queued timeout
         */
        me.cancel = function() {
            if (me.id) {
                clearInterval(me.id);
                me.id = null;
            }
        };
    };