One of the nice little additions in iOS SDK 4.2 are two new properties for CAShapeLayer: strokeStart and strokeEnd. Both are floats that hold a value between 0.0 and 1.0, indicating the relative location along the shape layer’s path at which to start and stop stroking the path. The default values are 0.0 for strokeStart and 1.0 for strokeEnd, obviously, which causes the shape layer’s path to be st