beamlet is determined by taking either the default length or the
length specified by @code{beamlet-max-length-proportion}, whichever is
smaller.")
- (beam-gap ,number-pair? "Size of a gap in a @code{Beam}.")
(beamlet-max-length-proportion ,pair? "The maximum length of a
beamlet, as a proportion of the distance between two adjacent stems.")
(before-line-breaking ,boolean? "Dummy property, used to trigger