This program can be used to list all the desktop files that are detected when using a specific menu file.

AppList.vala

/* Author: Akshay Shekher
 *
 * build: valac --pkg gio-unix-2.0 --pkg libgnome-menu-3.0 -X -DGMENU_I_KNOW_THIS_IS_UNSTABLE  applist.vala
 * run: ./applist gnome-applications.menu
 *  or  ./applist pantheon-applications.menu
 */

int main(string[] args) {
    if (args.length < 2) {
        print ("Please specify the file to load\n");
        return 1;
    }
    var apps_menu = new GMenu.Tree(args[1],
                                   GMenu.TreeFlags.INCLUDE_EXCLUDED);
    try {
        if (!apps_menu.load_sync ()) {
            print ("Could not load menu");
        }
    } catch (Error e) {
        print ("Error loading menu file: %s", e.message);
        return 0;
    }

    var iter = apps_menu.get_root_directory ().iter ();
    assert (iter != null);
    print ("Dir: %s\n", apps_menu.get_root_directory ().get_name ());
    process (iter);

    return 0;
}

void process(GMenu.TreeIter iter) {
    GMenu.TreeItemType type;

    while((type = iter.next ()) != GMenu.TreeItemType.INVALID) {
        switch (type) {

        case GMenu.TreeItemType.ALIAS:
        case GMenu.TreeItemType.ENTRY:
            var entry = iter.get_entry ();

            var appinfo = entry.get_app_info ();
            var desktop_file =  entry.get_desktop_file_path ();

            print ("App: %s\nDesktop File: %s\n\n", appinfo.get_display_name (),
                                                    desktop_file);
            break;

        case GMenu.TreeItemType.DIRECTORY:
            process (iter.get_directory ().iter ());
            break;

        default:
            print ("Some Other Type");
            break;
         }
    }

}