Question

I am working on Firefox addon on Mac OS, where I want to notify my XPCOM component when user disables the add-on.This is working except for the event is posted more than once(equal to the number of FF Windows open), this is happening since the AddonManager.addAddonListener(nsListener); is called on the onload(window.addEventListener(“load”, function(e) { TopWnd.onLoad(e); }, false);) in browser overlay js for all windows and the event “onDisabling” is called in each window.

var nsListener = {
    onDisabling: function(addon, needsRestart) 
{
        if (addon.id.toLowerCase() == "XXXXXXX") 
{
        var observerService = Components.classes["@mozilla.org/observer-service;1"]
                            .getService(Components.interfaces.nsIObserverService);
            if (observerService) {
                observerService.notifyObservers(null, "ext-disable", "Ext is disabled");
            }

        }
    }

}

To avoid notifying XPCOM component from all windows, I want to determine if the current opened tab/window is the add-on page and only then add the AddonManager.addAddonListener(nsListener); or notify only from that page.What is the best way to determine if the current window/tab is add-on page.

Please help.

Answer 1

I think that this approach is wrong. You shouldn’t register this listener in each window, it should be registered only once in a central place. You avoid the problem with multiple windows then and also the problem that sometimes no windows are open (possible on Mac OS X). It would make sense to register that listener directly in your XPCOM component. However, if for some reason this isn’t possible – you can still have a JavaScript module that each window will import and that will register this listener (a JavaScript module loads only once, no matter how often it is imported, so only one listener will be registered).

Side-notes: Don’t use generic topic names like ext-disabled (assuming that this is really the topic you are using), other extensions might decide to use the same name and there will be a huge mess. Use something that relates to the name of your extension so that it won’t be chosen by other developers. Also, using observer service to communicate with your own XPCOM component is strange to say the least, why not get an instance of that XPCOM component and call its methods directly?