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Bug 798353 - Make SettingsListener reuse the lock. r=fabrice

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This commit is contained in:
Tim Chien 2013-09-04 08:28:28 -04:00
parent bb892dac92
commit fd9ba8a89b
1 changed files with 43 additions and 25 deletions
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68
b2g/chrome/content/settings.js
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@ -4,7 +4,7 @@
* 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;"
"use strict";
const Cc = Components.classes;
const Ci = Components.interfaces;
@ -21,47 +21,65 @@ XPCOMUtils.defineLazyGetter(this, "libcutils", function () {
});
#endif
// Once Bug 731746 - Allow chrome JS object to implement nsIDOMEventTarget
// is resolved this helper could be removed.
var SettingsListener = {
_callbacks: {},
// Timer to remove the lock.
_timer: null,
init: function sl_init() {
if ('mozSettings' in navigator && navigator.mozSettings) {
navigator.mozSettings.onsettingchange = this.onchange.bind(this);
}
},
// lock stores here
_lock: null,
onchange: function sl_onchange(evt) {
var callback = this._callbacks[evt.settingName];
if (callback) {
callback(evt.settingValue);
/**
* getSettingsLock: create a lock or retrieve one that we saved.
* mozSettings.createLock() is expensive and lock should be reused
* whenever possible.
*/
getSettingsLock: function sl_getSettingsLock() {
// Each time there is a getSettingsLock call, we postpone the removal.
clearTimeout(this._timer);
this._timer = setTimeout((function() {
this._lock = null;
}).bind(this), 0);
// If there is a lock present we return that.
if (this._lock) {
return this._lock;
}
// If there isn't we create a new one.
let settings = window.navigator.mozSettings;
return (this._lock = settings.createLock());
},
observe: function sl_observe(name, defaultValue, callback) {
var settings = window.navigator.mozSettings;
if (!settings) {
window.setTimeout(function() { callback(defaultValue); });
return;
let settings = window.navigator.mozSettings;
let req;
try {
req = this.getSettingsLock().get(name);
} catch (e) {
// It is possible (but rare) for getSettingsLock() to return
// a SettingsLock object that is no longer valid.
// Until https://bugzilla.mozilla.org/show_bug.cgi?id=793239
// is fixed, we just catch the resulting exception and try
// again with a fresh lock
console.warn('Stale lock in settings.js.',
'See https://bugzilla.mozilla.org/show_bug.cgi?id=793239');
this._lock = null;
req = this.getSettingsLock().get(name);
}
if (!callback || typeof callback !== 'function') {
throw new Error('Callback is not a function');
}
var req = settings.createLock().get(name);
req.addEventListener('success', (function onsuccess() {
callback(typeof(req.result[name]) != 'undefined' ?
req.result[name] : defaultValue);
}));
this._callbacks[name] = callback;
settings.addObserver(name, function settingChanged(evt) {
callback(evt.settingValue);
});
}
};
SettingsListener.init();
// =================== Console ======================
SettingsListener.observe('debug.console.enabled', true, function(value) {