alerts_timer
if (!event_initialized(&w->alerts_timer))
evtimer_set(&w->alerts_timer, alerts_timer, w);
event_del(&w->alerts_timer);
event_add(&w->alerts_timer, &tv);
static void alerts_timer(int, short, void *);
struct event alerts_timer;
if (event_initialized(&w->alerts_timer))
evtimer_del(&w->alerts_timer);