def _prev_index(self, s):
        self.set_index(max(0, self.index - 1))
def drawMe(self, g):
        self.g = g
        self.g.beginPath()
        self.g.moveTo(self.p1.x,self.p1.y)
        self.g.lineTo(self.p2.x,self.p2.y)
        self.g.stroke()