with focus color when the scrollbar has keyboard focus. This should
help users figure out how one-handed nav works. Better would be to
override background color of the scrollbar and draw it full-sized, but
I havne't figured out how. This is good enough for beta.
This gets rid of what's visible behind the board when it's not
full-screen width, but causes a lot of flashing. Better will be to
make board.c own an entire rectangle and to decide board dimensions
itself.
