If QMenu is taller than whole screen estate and when popping open QMenu does not set active action and previous selection of the menu was done to bottom one items,
QMenu does not enable scrolling of the list to the top items at all.
This easiest to repro with QCalendarWidget and Symbian 5th Edition emulator. Launch application with QCalendarWidget and press month button to open month context menu.
Note that context menu does not quite fit into screen - last month - December is not visible. Scroll down to December and select that one.
Re-open the list. Note that December is not highlighted as QCalendarWidget does not set any action active and see that December is lowest item shown. January is not visible.
Try to scroll up to January. It is not possible.
Problem relates to QMenu::popup where it only sets the "up scroller" if atAction is given.