def do_back_forward(self, sens):
        self.bf = 1
        bt = Thread(target=self.back_forward_loop, args=(sens, ), daemon=True)
        bt.start()

    def back_forward_loop(self, sens):
        while self.bf:
            sleep(0.1)
            self.gap = self.gap + sens*10
            if self.gap > 0: self.gap = 0
            l = len(self.app.osc.histo_xyz)
            if self.gap < -l + 500: self.gap = -l + 500
            print("Gap:", self.gap)

    def do_end(self):
        self.bf = 0