Filip, thanks a lot for quick answer. I've already solve the problem with ScrollViewer but this solution is far from ideal
I can see that you already have needsClipBounds field (http://emptykeys.com/EmptyKeysUI/?topic=html/06d821d7-0b67-2034-9105-e1ced5c06931.htm). Maybe you can convert it into property?
BTW Where I can find project source code or only UI generator is opened?