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event-emitter.js
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event-emitter.js
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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* EventEmitter.
*/
(function (factory) { // Module boilerplate
if (this.module && module.id.indexOf("event-emitter") >= 0) { // require
factory.call(this, require, exports, module);
} else { // Cu.import
const Cu = Components.utils;
const { require } = Cu.import("resource://devtools/shared/Loader.jsm", {});
this.isWorker = false;
this.promise = Cu.import("resource://gre/modules/Promise.jsm", {}).Promise;
factory.call(this, require, this, { exports: this });
this.EXPORTED_SYMBOLS = ["EventEmitter"];
}
}).call(this, function (require, exports, module) {
this.EventEmitter = function EventEmitter() {};
module.exports = EventEmitter;
const { Cu, components } = require("chrome");
const Services = require("Services");
const promise = require("promise");
var loggingEnabled = true;
if (!isWorker) {
loggingEnabled = Services.prefs.getBoolPref("devtools.dump.emit");
Services.prefs.addObserver("devtools.dump.emit", {
observe: () => {
loggingEnabled = Services.prefs.getBoolPref("devtools.dump.emit");
}
}, false);
}
/**
* Decorate an object with event emitter functionality.
*
* @param Object aObjectToDecorate
* Bind all public methods of EventEmitter to
* the aObjectToDecorate object.
*/
EventEmitter.decorate = function EventEmitter_decorate (aObjectToDecorate) {
let emitter = new EventEmitter();
aObjectToDecorate.on = emitter.on.bind(emitter);
aObjectToDecorate.off = emitter.off.bind(emitter);
aObjectToDecorate.once = emitter.once.bind(emitter);
aObjectToDecorate.emit = emitter.emit.bind(emitter);
};
EventEmitter.prototype = {
/**
* Connect a listener.
*
* @param string aEvent
* The event name to which we're connecting.
* @param function aListener
* Called when the event is fired.
*/
on: function EventEmitter_on(aEvent, aListener) {
if (!this._eventEmitterListeners)
this._eventEmitterListeners = new Map();
if (!this._eventEmitterListeners.has(aEvent)) {
this._eventEmitterListeners.set(aEvent, []);
}
this._eventEmitterListeners.get(aEvent).push(aListener);
},
/**
* Listen for the next time an event is fired.
*
* @param string aEvent
* The event name to which we're connecting.
* @param function aListener
* (Optional) Called when the event is fired. Will be called at most
* one time.
* @return promise
* A promise which is resolved when the event next happens. The
* resolution value of the promise is the first event argument. If
* you need access to second or subsequent event arguments (it's rare
* that this is needed) then use aListener
*/
once: function EventEmitter_once(aEvent, aListener) {
let deferred = promise.defer();
let handler = (aEvent, aFirstArg, ...aRest) => {
this.off(aEvent, handler);
if (aListener) {
aListener.apply(null, [aEvent, aFirstArg, ...aRest]);
}
deferred.resolve(aFirstArg);
};
handler._originalListener = aListener;
this.on(aEvent, handler);
return deferred.promise;
},
/**
* Remove a previously-registered event listener. Works for events
* registered with either on or once.
*
* @param string aEvent
* The event name whose listener we're disconnecting.
* @param function aListener
* The listener to remove.
*/
off: function EventEmitter_off(aEvent, aListener) {
if (!this._eventEmitterListeners)
return;
let listeners = this._eventEmitterListeners.get(aEvent);
if (listeners) {
this._eventEmitterListeners.set(aEvent, listeners.filter(l => {
return l !== aListener && l._originalListener !== aListener;
}));
}
},
/**
* Emit an event. All arguments to this method will
* be sent to listener functions.
*/
emit: function EventEmitter_emit(aEvent) {
this.logEvent(aEvent, arguments);
if (!this._eventEmitterListeners || !this._eventEmitterListeners.has(aEvent)) {
return;
}
let originalListeners = this._eventEmitterListeners.get(aEvent);
for (let listener of this._eventEmitterListeners.get(aEvent)) {
// If the object was destroyed during event emission, stop
// emitting.
if (!this._eventEmitterListeners) {
break;
}
// If listeners were removed during emission, make sure the
// event handler we're going to fire wasn't removed.
if (originalListeners === this._eventEmitterListeners.get(aEvent) ||
this._eventEmitterListeners.get(aEvent).some(l => l === listener)) {
try {
listener.apply(null, arguments);
}
catch (ex) {
// Prevent a bad listener from interfering with the others.
let msg = ex + ": " + ex.stack;
Cu.reportError(msg);
dump(msg + "\n");
}
}
}
},
logEvent: function(aEvent, args) {
if (!loggingEnabled) {
return;
}
let caller, func, path;
if (!isWorker) {
caller = components.stack.caller.caller;
func = caller.name;
let file = caller.filename;
if (file.includes(" -> ")) {
file = caller.filename.split(/ -> /)[1];
}
path = file + ":" + caller.lineNumber;
}
let argOut = "(";
if (args.length === 1) {
argOut += aEvent;
}
let out = "EMITTING: ";
// We need this try / catch to prevent any dead object errors.
try {
for (let i = 1; i < args.length; i++) {
if (i === 1) {
argOut = "(" + aEvent + ", ";
} else {
argOut += ", ";
}
let arg = args[i];
argOut += arg;
if (arg && arg.nodeName) {
argOut += " (" + arg.nodeName;
if (arg.id) {
argOut += "#" + arg.id;
}
if (arg.className) {
argOut += "." + arg.className;
}
argOut += ")";
}
}
} catch(e) {
// Object is dead so the toolbox is most likely shutting down,
// do nothing.
}
argOut += ")";
out += "emit" + argOut + " from " + func + "() -> " + path + "\n";
dump(out);
},
};
});