gMaiHook = &sMaiHook;
mai_create_root(void){    if (!mai_initialized) {        return NULL;    }    if (!sRootAccessible) {        sRootAccessible = new MaiAppRoot();        NS_ASSERTION(sRootAccessible, "Fail to create MaiAppRoot");        /* initialize the MAI hook         * MAI provide the functions of "startup", "shutdown", "add toplvel"         * "remove toplevel", which are used by Mozilla through the MAI hook.         */        gMaiHook = &sMaiHook;        sMaiHook.MaiShutdown = mai_shutdown;        sMaiHook.MaiStartup = mai_init;        sMaiHook.AddTopLevelAccessible = mai_add_toplevel_accessible;        sMaiHook.RemoveTopLevelAccessible = mai_remove_toplevel_accessible;    }    return sRootAccessible;}