Stop scrolling behaviour until animation is finished

[dstN]

I want to prevent my users to scroll for ages just to be sure the animation finishes, so my question is, are there any events like "onStart" / "onComplete" for the animation, so I could stop the scrolling behaviour with overflow: hidden; on the body until the animation is done and remove that afterwards?

I checked the (old) gsap Docs and there are onStart/onComplete Events either for TweenMax.to and TimelineMax - I tried using them, but they fired immediately after page-load and I don't know why.

(https://greensock.com/docs/v2/TimelineMax/TimelineMax())
(https://greensock.com/docs/v2/TweenMax/static.to())

I'm animating svg-Font to achieve a "draw"-like feeling on the page.

Fiddle: https://jsfiddle.net/yf89Lhzv/1/

(Hello World should be fully animated until the user can scroll again)