Call back user functions with the specified timing 


/* Timers are identified by display:timer_id */
typedef long mbtk_timer_id_t;

/* Timer callback function return value determines whether the timer continues
   running after the call */
typedef enum mbtk_timer_res_e {
  MBTK_TIMER_CONTINUE = 0,
  MBTK_TIMER_STOP = 1
} mbtk_timer_res_t;

/* use thsi value if a timer shouldn't stop repeating */
#define MBTK_TIMER_REPEAT_FOREVER (-2)

/* create a timer that calls cb() rep times with at least period seconds in
   between the calls. The callback gets an user data and the number of calls
   left to be done. */
mbtk_timer_id_t mbtk_timer_new(mbtk_display_t *disp, long rep, double period, mbtk_timer_res_t (*cb)(long repleft, void *user_data), void *user_data);

/* Stop and remove a timer. Returns 0 on success, -1 on error. Error is
   "invalid tid". */
int mbtk_timer_stop(mbtk_display_t *disp, mbtk_timer_id_t tid);

/* Returns the number of iterations left for a timer; may be
   MBTK_TIMER_REPEAT_FOREVER or -1 on error (invalid tid) */
long mbtk_timer_get_repleft(mbtk_display_t *disp, mbtk_timer_id_t tid);