path.MoveToPoint (time_x (position) + 2, y_pos (_track.get()) + 4);
path.AddLineToPoint (time_x (position + len) - 1, y_pos (_track.get()) + 4);
path.AddLineToPoint (time_x (position + len) - 1, y_pos (_track.get() + 1) - 4);
path.MoveToPoint (time_x (position) + 2, y_pos (_track.get()) + 4);
path.AddLineToPoint (time_x (position + len) - 1, y_pos (_track.get()) + 4);
path.AddLineToPoint (time_x (position + len) - 1, y_pos (_track.get() + 1) - 4);