http://codereview.appspot.com/4237057/diff/11001/lily/beam.ccFile lily/beam.cc (right):
http://codereview.appspot.com/4237057/diff/11001/lily/beam.cc#newcode206
lily/beam.cc:206: orig->set_property ("feather-fraction", scm_cons
(scm_from_double (0.0), scm_from_double (orig->spanner_length ())));
my suggestion was for fraction to be a real fraction, ie. a number from
0.0 to 1.0, relative to the total length of the beam. That also gives
users a way to tune the featheriness they want from their beams (they
could set it to 0.0 - 2.0 to exaggerate the effect for instance), in a
scale-free way. My idea was also to put the effect of feather-dir into
this pair, ie. feather=LEFT => (1.0 . 0.0) and RIGHT => (0.0 . 1.0)
Does that sound right? I think you would be able to do without
feather-dir in the print callback.