from preamble:
"Change Set: scrollport Date: 28 December 2002 Author: Steven Swerling
I was adding a horizontal scrollbar to the SimpleHierarchicalListMorph, but realized that many of the methods would be generic to any subclass of ScrollPane. And there were many methods. So I moved the changes up to ScrollPane. This changeset adds a horizontal scrollbar to ScrollPane, which appears as needed. I don't know if there is any demand for this, so I'm just running it up the flagpole.
WARNING: The last thing you need is for a bug in ScrollPane. I don't know of any in this code, but better safe then sorry. So consider this a beta. Please tinker around with your applications to make sure everything is working ok before saving your image.
Tested on a fresh 3.4 image w/ updates up to #5138. "!