Having a look at the scrolling times, normalized to Joost's 1.4 buildJoost 1.4 : 1 Joost 1.5 : >2 cmake 1.5 : 1.4 indicates that some compiler flags and macro definitions could speed up the 1.4 without only further changes.
I think it's more likely that it depends on the window size. We should compare performance both in a small / large windows.
Joost