https://github.com/zkoss/zk/blob/ebbd54d5fc1eff6c0f9cf7692a2fe99522f324e1/zk/src/archive/web/js/zk/anima.js#L145
Assume we have
<progressmeter ca:data-animationspeed="0">
After calling getAnimationSpeed(), we will get 1, it might confuse user, this function should return the same value as given animationspeed setting, in this example, is 0.