Using the scrolling function on my kensington orbital scroll wheel mouse in
xev I see that two
ButtonRelease events of button 5 are triggered during a very small movement, followed by a long movement with no button pressing.
During normal usage, the use of the scroll wheel is very "jumpy" compared to other non-smooth scrolling wheels.
Here is the output from xinput:
Virtual core pointer id=2 [master pointer (3)] ↳ Virtual core XTEST pointer id=4 [slave pointer (2)] ↳ Primax Kensington Eagle Trackball id=9 [slave pointer (2)]