How to develop addons for rtl locales

The topic was initiated from url: http://www.babelzilla.org/content/view/316/. But the approach provided below doesn't work at all.

---

function getDirection() {

var myLocalBundleService = Components.classes ["@mozilla.org/intl/stringbundle;1"].getService(Components.interfaces.nsIStringBundleService);
var myLocalStrings = myLocalBundleService.createBundle("chrome://global/locale/global.dtd");
return myLocalStrings.GetStringFromName("locale.dir");
}

---

Good thing is that we can still read the direction property from document.dir and preference bidi.direction. The definition of bidi.direction can be found in source code:

// ------------------
 //  Text Direction
 // ------------------
 // 1 = directionLTRBidi *
 // 2 = directionRTLBidi
 pref("bidi.direction", 1);

Both of them are r/o, but here we just need to read the information.