michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 'use strict';
michael@0: 
michael@0: module.metadata = {
michael@0:   "stability": "unstable"
michael@0: };
michael@0: 
michael@0: const { Cc, Ci } = require('chrome');
michael@0: const { Class } = require('../core/heritage');
michael@0: const { EventTarget } = require('../event/target');
michael@0: const { Branch } = require('./service');
michael@0: const { emit, off } = require('../event/core');
michael@0: const { when: unload } = require('../system/unload');
michael@0: 
michael@0: const prefTargetNS = require('../core/namespace').ns();
michael@0: 
michael@0: const PrefsTarget = Class({
michael@0:   extends: EventTarget,
michael@0:   initialize: function(options) {
michael@0:     options = options || {};
michael@0:     EventTarget.prototype.initialize.call(this, options);
michael@0: 
michael@0:     let branchName = options.branchName || '';
michael@0:     let branch = Cc["@mozilla.org/preferences-service;1"].
michael@0:         getService(Ci.nsIPrefService).
michael@0:         getBranch(branchName).
michael@0:         QueryInterface(Ci.nsIPrefBranch2);
michael@0:     prefTargetNS(this).branch = branch;
michael@0: 
michael@0:     // provides easy access to preference values
michael@0:     this.prefs = Branch(branchName);
michael@0: 
michael@0:     // start listening to preference changes
michael@0:     let observer = prefTargetNS(this).observer = onChange.bind(this);
michael@0:     branch.addObserver('', observer, false);
michael@0: 
michael@0:     // Make sure to destroy this on unload
michael@0:     unload(destroy.bind(this));
michael@0:   }
michael@0: });
michael@0: exports.PrefsTarget = PrefsTarget;
michael@0: 
michael@0: /* HELPERS */
michael@0: 
michael@0: function onChange(subject, topic, name) {
michael@0:   if (topic === 'nsPref:changed') {
michael@0:     emit(this, name, name);
michael@0:     emit(this, '', name);
michael@0:   }
michael@0: }
michael@0: 
michael@0: function destroy() {
michael@0:   off(this);
michael@0: 
michael@0:   // stop listening to preference changes
michael@0:   let branch = prefTargetNS(this).branch;
michael@0:   branch.removeObserver('', prefTargetNS(this).observer, false);
michael@0:   prefTargetNS(this).observer = null;
michael@0: }