The drawn thumb always stopped 16 points short of its far end, leaving
room for the other axis's bar even in a menu or list, which has none, so
at the bottom of a long menu it still looked scrollable. The corner is now
left only where both axes scroll, as on the page, and the thumb keeps the
same 4 points from either end; the platform's scrollers on Mac OS X 10.6
run full length the same way.

Assisted-by: claude-opus-5.5