This works in a different way compared to the old widget.
To make it work we use vieport()'s height() and width()
and simplify the scroll position to:
scrollPosition = (mousePosition / totalLength) * scrollMaximum
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>