gecko-dev/devtools/shared/event-emitter.js

260 строки
8.2 KiB
JavaScript

/* 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/. */
"use strict";
(function (factory) {
// This file can be loaded in several different ways. It can be
// require()d, either from the main thread or from a worker thread;
// or it can be imported via Cu.import. These different forms
// explain some of the hairiness of this code.
//
// It's important for the devtools-as-html project that a require()
// on the main thread not use any chrome privileged APIs. Instead,
// the body of the main function can only require() (not Cu.import)
// modules that are available in the devtools content mode. This,
// plus the lack of |console| in workers, results in some gyrations
// in the definition of |console|.
if (this.module && module.id.indexOf("event-emitter") >= 0) {
let console;
if (isWorker) {
console = {
error: () => {}
};
} else {
console = this.console;
}
// require
factory.call(this, require, exports, module, console);
} else {
// Cu.import. This snippet implements a sort of miniature loader,
// which is responsible for appropriately translating require()
// requests from the client function. This code can use
// Cu.import, because it is never run in the devtools-in-content
// mode.
this.isWorker = false;
const Cu = Components.utils;
let console = Cu.import("resource://gre/modules/Console.jsm", {}).console;
// Bug 1259045: This module is loaded early in firefox startup as a JSM,
// but it doesn't depends on any real module. We can save a few cycles
// and bytes by not loading Loader.jsm.
let require = function (module) {
switch (module) {
case "devtools/shared/defer":
return Cu.import("resource://gre/modules/Promise.jsm", {}).Promise.defer;
case "Services":
return Cu.import("resource://gre/modules/Services.jsm", {}).Services;
case "chrome":
return {
Cu,
components: Components
};
}
return null;
};
factory.call(this, require, this, { exports: this }, console);
this.EXPORTED_SYMBOLS = ["EventEmitter"];
}
}).call(this, function (require, exports, module, console) {
// ⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠
// After this point the code may not use Cu.import, and should only
// require() modules that are "clean-for-content".
let EventEmitter = this.EventEmitter = function () {};
module.exports = EventEmitter;
// See comment in JSM module boilerplate when adding a new dependency.
const { components } = require("chrome");
const Services = require("Services");
const defer = require("devtools/shared/defer");
let 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 objectToDecorate
* Bind all public methods of EventEmitter to
* the objectToDecorate object.
*/
EventEmitter.decorate = function (objectToDecorate) {
let emitter = new EventEmitter();
objectToDecorate.on = emitter.on.bind(emitter);
objectToDecorate.off = emitter.off.bind(emitter);
objectToDecorate.once = emitter.once.bind(emitter);
objectToDecorate.emit = emitter.emit.bind(emitter);
};
EventEmitter.prototype = {
/**
* Connect a listener.
*
* @param string event
* The event name to which we're connecting.
* @param function listener
* Called when the event is fired.
*/
on(event, listener) {
if (!this._eventEmitterListeners) {
this._eventEmitterListeners = new Map();
}
if (!this._eventEmitterListeners.has(event)) {
this._eventEmitterListeners.set(event, []);
}
this._eventEmitterListeners.get(event).push(listener);
},
/**
* Listen for the next time an event is fired.
*
* @param string event
* The event name to which we're connecting.
* @param function listener
* (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 listener
*/
once(event, listener) {
let deferred = defer();
let handler = (_, first, ...rest) => {
this.off(event, handler);
if (listener) {
listener.apply(null, [event, first, ...rest]);
}
deferred.resolve(first);
};
handler._originalListener = listener;
this.on(event, handler);
return deferred.promise;
},
/**
* Remove a previously-registered event listener. Works for events
* registered with either on or once.
*
* @param string event
* The event name whose listener we're disconnecting.
* @param function listener
* The listener to remove.
*/
off(event, listener) {
if (!this._eventEmitterListeners) {
return;
}
let listeners = this._eventEmitterListeners.get(event);
if (listeners) {
this._eventEmitterListeners.set(event, listeners.filter(l => {
return l !== listener && l._originalListener !== listener;
}));
}
},
/**
* Emit an event. All arguments to this method will
* be sent to listener functions.
*/
emit(event) {
this.logEvent(event, arguments);
if (!this._eventEmitterListeners || !this._eventEmitterListeners.has(event)) {
return;
}
let originalListeners = this._eventEmitterListeners.get(event);
for (let listener of this._eventEmitterListeners.get(event)) {
// 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(event) ||
this._eventEmitterListeners.get(event).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;
console.error(msg);
dump(msg + "\n");
}
}
}
},
logEvent(event, 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 += event;
}
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 = "(" + event + ", ";
} 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);
},
};
});