If you specify
None here, your listview
won't get a scroller at all and look much like a list object
alone. However, listviews without scroller are still more
powerful than list objects as they feature e.g. drag&drop
Creating listviews without a scrollbar makes sense if you want to have the scrollbar somewhere else, e.g. outside of a horizontal virtual group where the listview resides. This technique allows the creation of horizontally scrollable listviews.
The following options are possible: