'Backend derived classes should call this function when entering
canvas
Parameters
guiEvent
the native UI event that generated the mpl event
xy : tuple of 2 scalars
the coordinate location of the pointer when the canvas is
entered'

def enter_notify_event(self, guiEvent=None, xy=None):

    if (xy is not None):
        (x, y) = xy
        (self._lastx, self._lasty) = (x, y)
    event = Event(u'figure_enter_event', self, guiEvent)
    self.callbacks.process(u'figure_enter_event', event)
