Smooth scrolling (scroll per pixel) in ItemViews does not work as expected

Scrolling in listviews when set to scroll per pixel will scroll either 3 items at a time, or with large items the heigth of the visible part of the listview.

Docs say: QAbstractItemView::ScrollPerPixel - The view will scroll the contents one pixel at a time.

This is especially visible and annoying in KDE when using delegates with big height, as described here:
https://bugs.kde.org/show_bug.cgi?id=188757
(for example KDE's wallpaper list with previews, get hot new stuff dialog)

Attached is a simple qt-only testcase to make the problem visible.

I created a workaround as a starting point to find the right fix.
http://qt.gitorious.org/~frederik/qt/frederiks-qt/commit/4a10fde34c478a512acae113fa7e4d083e36ec16

Cheers
Frederik