(print): read quantized-positions, so we can force
Beam::set_stem_lengths to occur.
(rest_collision_callback): use common X parent.
"neutral-direction "
"positions "
"quant-score "
+ "quantized-positions "
"shorten "
"stems "
"thickness "
;; TODO: use interface for this!
+ (quantized-positions ,number-pair? "Beam positions after quanting.")
(chord-tremolo ,boolean? "if set, this beam is a tremolo. ")
(begin-of-line-visible ,boolean? "Used for marking ChordNames that should only show changes.")