On 2021-03-19 12:30 pm, Dimitris Marinakis wrote:
I don't like manually setting Y values of glissando endpoints. I'd
appreciate a more thoughtful approach.
Is it possible to reference the calculation Lilypond already does and
add a
value to it without trying to guesstimate what the actual value is from
scratch? The default placement is sometimes 95% fine but I'd like to
nudge
it a bit upwards or downwards without tweaking the padding.
This makes cross-staff glissando editing really annoying. If my
thinking
makes sense, this would solve the problem partially since Lilypond will
do
its best each time the staff spacing gets changed but the tweak will
help
on top of that.
Normally, this would be a job for \offset. However, \offset does not
work with all properties, in particular, nested properties like the
bound-details of the line-spanner-interface.
But you can effect the same change by using extra-dy and Y-offset with a
little bit of arithmetic:
%%%%
\version "2.22.0"
offsetGlissando =
#(begin
(define (number-or-number-list? arg)
(or (number? arg) (number-list? arg)))
(define ((indexed lst) grob)
(list-ref lst (ly:grob-property grob 'glissando-index)))
(define-event-function
(left-dy right-dy)
(number-or-number-list? number-or-number-list?)
(if (number? left-dy) (set! left-dy (list left-dy)))
(if (number? right-dy) (set! right-dy (list right-dy)))
(let ((extra-dy (map (lambda (l r) (- r l)) left-dy right-dy))
(Y-offset (map (lambda (l r) (/ (+ l r) 2)) left-dy right-dy)))
#{ \tweak extra-dy #(indexed extra-dy)
\tweak Y-offset #(indexed Y-offset)
\glissando #})))
\paper { indent = 0 line-width = 10\cm}
{ f'2 \glissando c''2
f'2 \offsetGlissando #-1 #-1 c''2
f'2 \offsetGlissando #1 #1 c''2
f'2 \offsetGlissando #-2 #0 c''2
f'2 \offsetGlissando #2 #0 c''2 \break
f'2 \offsetGlissando #0 #-2 c''2
f'2 \offsetGlissando #0 #2 c''2 \bar "||"
\override Glissando.before-line-breaking =
#(lambda (grob)
(ly:grob-set-property! grob 'color
(list-ref (list black red blue)
(ly:grob-property grob 'glissando-index))))
<f' a' c''>2 \glissando <c'' g' e'>2
<f' a' c''>2 \offsetGlissando #'(1 1 -2) #'(-1.5 1.5 0)
<c'' g' e'>2 \bar "|." }
%%%%
The parameters to \offsetGlissando are delta-Y values for the left and
right bounds respectively. If there are multiple glissandi, then the
arguments should be lists of numbers, each value corresponding to a
particular glissando. Shown above is an untangling of the crossing
glissandi, which the coloring should make clearer.
P.S. I am ignoring the possibility of broken glissandi, as they are not
supported by default.
-- Aaron Hill
