51 lines
1.5 KiB
JavaScript
51 lines
1.5 KiB
JavaScript
/* -*- Mode: js2; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
// https://developer.mozilla.org/en/Code_snippets/Preferences
|
|
|
|
var EXPORTED_SYMBOLS = [ "PrefListener" ];
|
|
|
|
const Cc = Components.classes;
|
|
const Ci = Components.interfaces;
|
|
const Cu = Components.utils;
|
|
|
|
|
|
/**
|
|
* @constructor
|
|
*
|
|
* @param {string} branch_name
|
|
* @param {Function} callback must have the following arguments:
|
|
* branch, pref_leaf_name
|
|
*/
|
|
function PrefListener(branch_name, callback) {
|
|
// Keeping a reference to the observed preference branch or it will get
|
|
// garbage collected.
|
|
var prefService = Components.classes["@mozilla.org/preferences-service;1"]
|
|
.getService(Components.interfaces.nsIPrefService);
|
|
this._branch = prefService.getBranch(branch_name);
|
|
this._branch.QueryInterface(Ci.nsIPrefBranch);
|
|
this._callback = callback;
|
|
}
|
|
|
|
PrefListener.prototype.observe = function(subject, topic, data) {
|
|
if (topic == 'nsPref:changed')
|
|
this._callback(this._branch, data);
|
|
};
|
|
|
|
/**
|
|
* @param {boolean=} trigger if true triggers the registered function
|
|
* on registration, that is, when this method is called.
|
|
*/
|
|
PrefListener.prototype.register = function(trigger) {
|
|
this._branch.addObserver('', this, false);
|
|
if (trigger) {
|
|
let that = this;
|
|
this._branch.getChildList('', {}).
|
|
forEach(function (pref_leaf_name)
|
|
{ that._callback(that._branch, pref_leaf_name); });
|
|
}
|
|
};
|
|
|
|
PrefListener.prototype.unregister = function() {
|
|
if (this._branch)
|
|
this._branch.removeObserver('', this);
|
|
};
|