http://bugs.winehq.org/show_bug.cgi?id=10544
--- Comment #2 from Timo Kreuzer timo.kreuzer@web.de 2007-11-26 14:13:43 --- wine-0.9.49
The line is comctl32/treeview.c:3230
ScrollWindowEx will scroll the whole content of the scrollRect up by scrolldist pixels. At that point scrollRect covers the whole area below the collapsed item. ScrollWindowEx will draw outside the scrollRect, if no clipping rect is set, so the area below the collapsed item will be scrolled up and drawn over the upper part of the treeview.
btw: Windows regedit doesn't show this (don't know why), but ReactOS regedit does on windows xp+wine comctl32.dll, it works correctly with windows comctl32.dll