'Backend derived classes should call this function when leaving
canvas
Parameters
guiEvent
the native UI event that generated the mpl event'

def leave_notify_event(self, guiEvent=None):

    self.callbacks.process(u'figure_leave_event', LocationEvent.lastevent)
    LocationEvent.lastevent = None
    (self._lastx, self._lasty) = (None, None)
