import time

class Timeout:
   """ Timeout timer for use with Tkinter.
   It uses repeated calls to "after" instead of a single
   call to "after" with a long timeout, because the
   "cancel" routine seems to have a memory leak.
   """
   def __init__(self, master, poll = 1, timeout = 1000, callback = None):
      self.__callback = callback
      self.__poll_ms = int(1000 * poll)
      self.__timeout = timeout
      self.__running = 0
      self.__master = master

   def start(self):
      self.__last_time = time.time()
      self.__run = 1
      if not self.__running:
         self.__master.after(self.__poll_ms, self.__check)
         self.__running = 1

   def stop(self):
      self.__run = 0

   def __check(self):
      if not self.__run:
         self.__running = 0
         return
      if time.time() - self.__last_time > self.__timeout:
         self.__callback()
      self.__master.after(self.__poll_ms, self.__check)
      self.__running = 1