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-rw-r--r--addon-sdk/source/lib/sdk/preferences/event-target.js61
1 files changed, 61 insertions, 0 deletions
diff --git a/addon-sdk/source/lib/sdk/preferences/event-target.js b/addon-sdk/source/lib/sdk/preferences/event-target.js
new file mode 100644
index 000000000..b64ba303c
--- /dev/null
+++ b/addon-sdk/source/lib/sdk/preferences/event-target.js
@@ -0,0 +1,61 @@
+/* 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": "unstable"
+};
+
+const { Cc, Ci } = require('chrome');
+const { Class } = require('../core/heritage');
+const { EventTarget } = require('../event/target');
+const { Branch } = require('./service');
+const { emit, off } = require('../event/core');
+const { when: unload } = require('../system/unload');
+
+const prefTargetNS = require('../core/namespace').ns();
+
+const PrefsTarget = Class({
+ extends: EventTarget,
+ initialize: function(options) {
+ options = options || {};
+ EventTarget.prototype.initialize.call(this, options);
+
+ let branchName = options.branchName || '';
+ let branch = Cc["@mozilla.org/preferences-service;1"].
+ getService(Ci.nsIPrefService).
+ getBranch(branchName).
+ QueryInterface(Ci.nsIPrefBranch2);
+ prefTargetNS(this).branch = branch;
+
+ // provides easy access to preference values
+ this.prefs = Branch(branchName);
+
+ // start listening to preference changes
+ let observer = prefTargetNS(this).observer = onChange.bind(this);
+ branch.addObserver('', observer, false);
+
+ // Make sure to destroy this on unload
+ unload(destroy.bind(this));
+ }
+});
+exports.PrefsTarget = PrefsTarget;
+
+/* HELPERS */
+
+function onChange(subject, topic, name) {
+ if (topic === 'nsPref:changed') {
+ emit(this, name, name);
+ emit(this, '', name);
+ }
+}
+
+function destroy() {
+ off(this);
+
+ // stop listening to preference changes
+ let branch = prefTargetNS(this).branch;
+ branch.removeObserver('', prefTargetNS(this).observer, false);
+ prefTargetNS(this).observer = null;
+}