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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/. */
"use strict";
module.metadata = {
"stability": "experimental"
};
const { Cc, Ci, Cr, Cu } = require("chrome");
const { Class } = require("./heritage");
const { isWeak } = require("./reference");
const method = require("../../method/core");
const observerService = Cc['@mozilla.org/observer-service;1'].
getService(Ci.nsIObserverService);
const { ShimWaiver } = Cu.import("resource://gre/modules/ShimWaiver.jsm");
const addObserver = ShimWaiver.getProperty(observerService, "addObserver");
const removeObserver = ShimWaiver.getProperty(observerService, "removeObserver");
// This is a method that will be invoked when notification observer
// subscribed to occurs.
const observe = method("observer/observe");
exports.observe = observe;
// Method to subscribe to the observer notification.
const subscribe = method("observe/subscribe");
exports.subscribe = subscribe;
// Method to unsubscribe from the observer notifications.
const unsubscribe = method("observer/unsubscribe");
exports.unsubscribe = unsubscribe;
// This is wrapper class that takes a `delegate` and produces
// instance of `nsIObserver` which will delegate to a given
// object when observer notification occurs.
const ObserverDelegee = Class({
initialize: function(delegate) {
this.delegate = delegate;
},
QueryInterface: function(iid) {
if (!iid.equals(Ci.nsIObserver) &&
!iid.equals(Ci.nsISupportsWeakReference) &&
!iid.equals(Ci.nsISupports))
throw Cr.NS_ERROR_NO_INTERFACE;
return this;
},
observe: function(subject, topic, data) {
observe(this.delegate, subject, topic, data);
}
});
// Class that can be either mixed in or inherited from in
// order to subscribe / unsubscribe for observer notifications.
const Observer = Class({});
exports.Observer = Observer;
// Weak maps that associates instance of `ObserverDelegee` with
// an actual observer. It ensures that `ObserverDelegee` instance
// won't be GC-ed until given `observer` is.
const subscribers = new WeakMap();
// Implementation of `subscribe` for `Observer` type just registers
// observer for an observer service. If `isWeak(observer)` is `true`
// observer service won't hold strong reference to a given `observer`.
subscribe.define(Observer, (observer, topic) => {
if (!subscribers.has(observer)) {
const delegee = new ObserverDelegee(observer);
subscribers.set(observer, delegee);
addObserver(delegee, topic, isWeak(observer));
}
});
// Unsubscribes `observer` from observer notifications for the
// given `topic`.
unsubscribe.define(Observer, (observer, topic) => {
const delegee = subscribers.get(observer);
if (delegee) {
subscribers.delete(observer);
removeObserver(delegee, topic);
}
});
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