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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/. */
export function EventEmitter() {}
let loggingEnabled = Services.prefs.getBoolPref("toolkit.dump.emit");
Services.prefs.addObserver("toolkit.dump.emit", {
observe: () => {
loggingEnabled = Services.prefs.getBoolPref("toolkit.dump.emit");
},
});
/**
* 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);
};
function describeNthCaller(n) {
let caller = Components.stack;
// Do one extra iteration to skip this function.
while (n >= 0) {
--n;
caller = caller.caller;
}
let func = caller.name;
let file = caller.filename;
if (file.includes(" -> ")) {
file = caller.filename.split(/ -> /)[1];
}
let path = file + ":" + caller.lineNumber;
return func + "() -> " + path;
}
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) {
return new Promise(resolve => {
let handler = (_, first, ...rest) => {
this.off(event, handler);
if (listener) {
listener(event, first, ...rest);
}
resolve(first);
};
handler._originalListener = listener;
this.on(event, handler);
});
},
/**
* 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) {
console.error(ex);
}
}
}
},
logEvent(event, args) {
if (!loggingEnabled) {
return;
}
let description = describeNthCaller(2);
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 " + description + "\n";
dump(out);
},
};
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