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Copyright (c) 2010, Yahoo! Inc. All rights reserved.
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Code licensed under the BSD License:
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http://developer.yahoo.com/yui/license.html
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YUI.add('async-queue', function(Y) {
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* <p>AsyncQueue allows you create a chain of function callbacks executed
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* via setTimeout (or synchronously) that are guaranteed to run in order.
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* Items in the queue can be promoted or removed. Start or resume the
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* execution chain with run(). pause() to temporarily delay execution, or
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* stop() to halt and clear the queue.</p>
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* <p>A specialized queue class that supports scheduling callbacks to execute
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* sequentially, iteratively, even asynchronously.</p>
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* <p>Callbacks can be function refs or objects with the following keys. Only
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* the <code>fn</code> key is required.</p>
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* <li><code>fn</code> -- The callback function</li>
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* <li><code>context</code> -- The execution context for the callbackFn.</li>
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* <li><code>args</code> -- Arguments to pass to callbackFn.</li>
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* <li><code>timeout</code> -- Millisecond delay before executing callbackFn.
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* (Applies to each iterative execution of callback)</li>
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* <li><code>iterations</code> -- Number of times to repeat the callback.
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* <li><code>until</code> -- Repeat the callback until this function returns
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* true. This setting trumps iterations.</li>
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* <li><code>autoContinue</code> -- Set to false to prevent the AsyncQueue from
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* executing the next callback in the Queue after
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* the callback completes.</li>
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* <li><code>id</code> -- Name that can be used to get, promote, get the
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* indexOf, or delete this callback.</li>
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* @extends EventTarget
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* @param callback* {Function|Object} 0..n callbacks to seed the queue
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Y.AsyncQueue = function() {
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this.add.apply(this, arguments);
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var Queue = Y.AsyncQueue,
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isObject = Y.Lang.isObject,
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isFunction = Y.Lang.isFunction;
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* <p>Static default values used to populate callback configuration properties.
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* Preconfigured defaults include:</p>
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* <li><code>autoContinue</code>: <code>true</code></li>
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* <li><code>iterations</code>: 1</li>
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* <li><code>timeout</code>: 10 (10ms between callbacks)</li>
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* <li><code>until</code>: (function to run until iterations <= 0)</li>
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* @property AsyncQueue.defaults
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Queue.defaults = Y.mix({
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return this.iterations <= 0;
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}, Y.config.queueDefaults || {});
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Y.extend(Queue, Y.EventTarget, {
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* Used to indicate the queue is currently executing a callback.
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* @type {Boolean|Object} true for synchronous callback execution, the
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* return handle from Y.later for async callbacks.
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* Initializes the AsyncQueue instance properties and events.
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_init : function () {
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Y.EventTarget.call(this, { emitFacade: true });
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* Callback defaults for this instance. Static defaults that are not
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* overridden are also included.
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* Initializes the instance events.
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* @method _initEvents
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_initEvents : function () {
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'execute' : { defaultFn : this._defExecFn, emitFacade: true },
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'shift' : { defaultFn : this._defShiftFn, emitFacade: true },
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'add' : { defaultFn : this._defAddFn, emitFacade: true },
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'promote' : { defaultFn : this._defPromoteFn, emitFacade: true },
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'remove' : { defaultFn : this._defRemoveFn, emitFacade: true }
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* Returns the next callback needing execution. If a callback is
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* configured to repeat via iterations or until, it will be returned until
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* the completion criteria is met.
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* When the queue is empty, null is returned.
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* @return {Function} the callback to execute
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while (this._q.length) {
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callback = this._q[0] = this._prepare(this._q[0]);
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if (callback && callback.until()) {
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this.fire(SHIFT, { callback: callback });
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return callback || null;
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* Default functionality for the "shift" event. Shifts the
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* callback stored in the event object's <em>callback</em> property from
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* the queue if it is the first item.
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* @method _defShiftFn
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* @param e {Event} The event object
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_defShiftFn : function (e) {
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if (this.indexOf(e.callback) === 0) {
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* Creates a wrapper function to execute the callback using the aggregated
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* configuration generated by combining the static AsyncQueue.defaults, the
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* instance defaults, and the specified callback settings.
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* The wrapper function is decorated with the callback configuration as
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* properties for runtime modification.
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* @param callback {Object|Function} the raw callback
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* @return {Function} a decorated function wrapper to execute the callback
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_prepare: function (callback) {
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if (isFunction(callback) && callback._prepared) {
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var config = Y.merge(
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{ context : this, args: [], _prepared: true },
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(isFunction(callback) ? { fn: callback } : callback)),
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wrapper = Y.bind(function () {
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if (!wrapper._running) {
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wrapper.iterations--;
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if (isFunction(wrapper.fn)) {
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wrapper.fn.apply(wrapper.context || Y,
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Y.Array(wrapper.args));
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return Y.mix(wrapper, config);
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* Sets the queue in motion. All queued callbacks will be executed in
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* order unless pause() or stop() is called or if one of the callbacks is
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* configured with autoContinue: false.
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* @return {AsyncQueue} the AsyncQueue instance
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for (callback = this.next();
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cont && callback && !this.isRunning();
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callback = this.next())
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cont = (callback.timeout < 0) ?
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this._execute(callback) :
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this._schedule(callback);
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* Event fired after the last queued callback is executed.
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this.fire('complete');
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* Handles the execution of callbacks. Returns a boolean indicating
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* whether it is appropriate to continue running.
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* @param callback {Object} the callback object to execute
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* @return {Boolean} whether the run loop should continue
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_execute : function (callback) {
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this._running = callback._running = true;
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callback.iterations--;
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this.fire(EXECUTE, { callback: callback });
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var cont = this._running && callback.autoContinue;
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this._running = callback._running = false;
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* Schedules the execution of asynchronous callbacks.
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* @param callback {Object} the callback object to execute
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* @return {Boolean} whether the run loop should continue
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_schedule : function (callback) {
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this._running = Y.later(callback.timeout, this, function () {
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if (this._execute(callback)) {
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* Determines if the queue is waiting for a callback to complete execution.
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* @return {Boolean} true if queue is waiting for a
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* from any initiated transactions
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isRunning : function () {
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return !!this._running;
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* Default functionality for the "execute" event. Executes the
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* @param e {Event} the event object
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_defExecFn : function (e) {
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* Add any number of callbacks to the end of the queue. Callbacks may be
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* provided as functions or objects.
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* @param callback* {Function|Object} 0..n callbacks
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* @return {AsyncQueue} the AsyncQueue instance
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this.fire('add', { callbacks: Y.Array(arguments,0,true) });
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* Default functionality for the "add" event. Adds the callbacks
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* in the event facade to the queue. Callbacks successfully added to the
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* queue are present in the event's <code>added</code> property in the
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* @param e {Event} the event object
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_defAddFn : function(e) {
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Y.Array.each(e.callbacks, function (c) {
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* Pause the execution of the queue after the execution of the current
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* callback completes. If called from code outside of a queued callback,
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* clears the timeout for the pending callback. Paused queue can be
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* restarted with q.run()
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* @return {AsyncQueue} the AsyncQueue instance
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if (isObject(this._running)) {
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this._running.cancel();
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this._running = false;
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* Stop and clear the queue after the current execution of the
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* current callback completes.
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* @return {AsyncQueue} the AsyncQueue instance
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* Returns the current index of a callback. Pass in either the id or
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* callback function from getCallback.
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* @param callback {String|Function} the callback or its specified id
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* @return {Number} index of the callback or -1 if not found
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indexOf : function (callback) {
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var i = 0, len = this._q.length, c;
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for (; i < len; ++i) {
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if (c === callback || c.id === callback) {
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* Retrieve a callback by its id. Useful to modify the configuration
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* while the queue is running.
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* @method getCallback
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* @param id {String} the id assigned to the callback
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* @return {Object} the callback object
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getCallback : function (id) {
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var i = this.indexOf(id);
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return (i > -1) ? this._q[i] : null;
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* Promotes the named callback to the top of the queue. If a callback is
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* currently executing or looping (via until or iterations), the promotion
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* is scheduled to occur after the current callback has completed.
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* @param callback {String|Object} the callback object or a callback's id
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* @return {AsyncQueue} the AsyncQueue instance
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promote : function (callback) {
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var payload = { callback : callback },e;
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if (this.isRunning()) {
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e = this.after(SHIFT, function () {
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this.fire(PROMOTE, payload);
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this.fire(PROMOTE, payload);
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* <p>Default functionality for the "promote" event. Promotes the
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* named callback to the head of the queue.</p>
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* <p>The event object will contain a property "callback", which
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* holds the id of a callback or the callback object itself.</p>
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* @method _defPromoteFn
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* @param e {Event} the custom event
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_defPromoteFn : function (e) {
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var i = this.indexOf(e.callback),
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promoted = (i > -1) ? this._q.splice(i,1)[0] : null;
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e.promoted = promoted;
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this._q.unshift(promoted);
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* Removes the callback from the queue. If the queue is active, the
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* removal is scheduled to occur after the current callback has completed.
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* @param callback {String|Object} the callback object or a callback's id
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* @return {AsyncQueue} the AsyncQueue instance
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remove : function (callback) {
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var payload = { callback : callback },e;
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// Can't return the removed callback because of the deferral until
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// current callback is complete
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if (this.isRunning()) {
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e = this.after(SHIFT, function () {
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this.fire(REMOVE, payload);
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this.fire(REMOVE, payload);
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* <p>Default functionality for the "remove" event. Removes the
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* callback from the queue.</p>
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* <p>The event object will contain a property "callback", which
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* holds the id of a callback or the callback object itself.</p>
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* @method _defRemoveFn
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* @param e {Event} the custom event
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_defRemoveFn : function (e) {
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var i = this.indexOf(e.callback);
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e.removed = (i > -1) ? this._q.splice(i,1)[0] : null;
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* Returns the number of callbacks in the queue.
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// next() flushes callbacks that have met their until() criteria and
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// therefore shouldn't count since they wouldn't execute anyway.
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if (!this.isRunning()) {
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return this._q.length;
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}, '3.2.0' ,{requires:['event-custom']});
added
removed
src-js/lazrjs/yui/async-queue/async-queue-debug.js
