def __update_rollover_state(self, new_state, x, y):
self.__rollover_state = new_state<EOL>if not self.is_under_mouse(x, y):<EOL><INDENT>self.__rollover_state = '<STR_LIT>'<EOL><DEDENT>if self.__rollover_state != self.__last_rollover_state:<EOL><INDENT>self.dispatch_event(<EOL>'<STR_LIT>',<EOL>self, self.__rollover_state, self.__last_rollover_state,<EOL>)<EOL>self.__last_rollover_state = self.__rollover_state<EOL><DEDENT>
Notify anyone who's interested that the mouse just interacted with this 
widget.

The rollover event contains the current rollover state and the previous 
state.  This method helps keep track of those things, and also prevents 
the widget from dispatching rollover events if nothing actually changed
(i.e. you can't transition from "over" to "over").