/**
* @license
* Copyright 2016 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
goog.provide('shaka.util.FakeEventTarget');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.FakeEvent');
goog.require('shaka.util.MultiMap');
/**
* A work-alike for EventTarget. Only DOM elements may be true EventTargets,
* but this can be used as a base class to provide event dispatch to non-DOM
* classes. Only FakeEvents should be dispatched.
*
* @struct
* @constructor
* @implements {EventTarget}
* @exportInterface
*/
shaka.util.FakeEventTarget = function() {
/**
* @private {!shaka.util.MultiMap.<shaka.util.FakeEventTarget.ListenerType>}
*/
this.listeners_ = new shaka.util.MultiMap();
/**
* The target of all dispatched events. Defaults to |this|.
* @type {EventTarget}
*/
this.dispatchTarget = this;
};
/**
* These are the listener types defined in the closure extern for EventTarget.
* @typedef {EventListener|function(!Event):*}
* @exportInterface
*/
shaka.util.FakeEventTarget.ListenerType;
/**
* Add an event listener to this object.
*
* @param {string} type The event type to listen for.
* @param {shaka.util.FakeEventTarget.ListenerType} listener The callback or
* listener object to invoke.
* @param {(!AddEventListenerOptions|boolean)=} options Ignored.
* @override
* @exportInterface
*/
shaka.util.FakeEventTarget.prototype.addEventListener =
function(type, listener, options) {
this.listeners_.push(type, listener);
};
/**
* Remove an event listener from this object.
*
* @param {string} type The event type for which you wish to remove a listener.
* @param {shaka.util.FakeEventTarget.ListenerType} listener The callback or
* listener object to remove.
* @param {(EventListenerOptions|boolean)=} options Ignored.
* @override
* @exportInterface
*/
shaka.util.FakeEventTarget.prototype.removeEventListener =
function(type, listener, options) {
this.listeners_.remove(type, listener);
};
/**
* Dispatch an event from this object.
*
* @param {!Event} event The event to be dispatched from this object.
* @return {boolean} True if the default action was prevented.
* @override
* @exportInterface
*/
shaka.util.FakeEventTarget.prototype.dispatchEvent = function(event) {
// In many browsers, it is complex to overwrite properties of actual Events.
// Here we expect only to dispatch FakeEvents, which are simpler.
goog.asserts.assert(event instanceof shaka.util.FakeEvent,
'FakeEventTarget can only dispatch FakeEvents!');
const listeners = this.listeners_.get(event.type) || [];
// Execute this event on listeners until the event has been stopped or we
// run out of listeners.
for (let i = 0; i < listeners.length; ++i) {
// Do this every time, since events can be re-dispatched from handlers.
event.target = this.dispatchTarget;
event.currentTarget = this.dispatchTarget;
let listener = listeners[i];
try {
// Check for the |handleEvent| member to test if this is a
// |EventListener| instance or a basic function.
if (listener.handleEvent) {
listener.handleEvent(event);
} else {
listener.call(this, event);
}
} catch (exception) {
// Exceptions during event handlers should not affect the caller,
// but should appear on the console as uncaught, according to MDN:
// https://mzl.la/2JXgwRo
shaka.log.error('Uncaught exception in event handler', exception,
exception ? exception.message : null,
exception ? exception.stack : null);
}
if (event.stopped) {
break;
}
}
return event.defaultPrevented;
};