a 8 pt font (set 8 pt in preferences.xml, too)
- fix vertical alignment of digits in label and ladder (temporary
solution -- the whole font handling needs to be reviewd and fixed)
- simplify nadir and zenith (they always want to be horizontally centered
on the ladder lines, no?)
- simplify and abstract label box drawing (no need for stippled side lines)
- align text (more) correctly in label boxes
- move variable declaration near their first use (c++ style rather than c)
- rename (zenith|nadir|hat) to enable-(zenith|nadir|hat) and make them bool
(for consistency reasons)
