I can say this method would be a real pain if you use alot of scrollable listBoxes.
Someone put up a scrollable implementation of listBox for dialogs but I cant remember what thread it was under. It was really not a viable option for me since it used like 4 listeners and required almost half a dozen classes to implement the thing.
If you want pixel level scrolling then I think you have to use a ViewPort. JME clipping is only available as a special hack that things like Nifty could use that do direct rendering. It’s not available to the scene graph.
Folks have tried to add it (myself included). The issue is that clipping is ViewPort specific but a particular Spatial can be in any number of ViewPorts. Makes it tricky.