Hi Carren,
I don't see another possibility. But I'm willing to implement 2) if it
fits your need.
Maybe something like this?
\version "2.25.23"
keysig-colors =
#(list
(cons #{ as #} blue)
(cons #{ es #} green)
(cons #{ ges #} red)
)
%{
keysig stencils have the form:
(translate-stencil (horizontal...)
(combine-stencil
[all the individual accidentals]
))
the individual accidentals have the form
(translate-stencil [...]
(translate-stencil [...]
(...)
where the innermost translation (it's two layers or one layer) is the Y
translation
responsible for the pitch.
%}
% todo: replace cdadaddr overkill by match structure!
#(define (cadaddr lst) (car (cdaddr lst)))
#(define (cdadaddr lst) (cdr (cadaddr lst)))
#(define (translation? lst)
(and (pair? lst)
(eq? (car lst) 'translate-stencil)))
#(define (innermost-translation stencil-expr)
(if (translation? stencil-expr)
(let ((inner-stencil-expr (caddr stencil-expr)))
(if (translation? inner-stencil-expr)
(innermost-translation inner-stencil-expr)
(cadr stencil-expr)))))
colouredKeySignature =
#(define-music-function (pitch-color-alist) (alist?)
#{
\override Staff.KeySignature.stencil =
#(grob-transformer
'stencil
(lambda (grob keysig)
(define notename-color-alist
(map (lambda (pitch-color-pair)
(cons (ly:pitch-notename (car pitch-color-pair))
(cdr pitch-color-pair)))
pitch-color-alist))
(define (colourise-single-accidental stencil-expr Y-position)
(let*
((c0-position (ly:grob-property grob 'c0-position))
(Y-notename (modulo (inexact->exact (- (* Y-position 2)
c0-position))
7))
(color (assq-ref notename-color-alist Y-notename)))
(if (color? color)
`(color ,(normalize-color color) ,stencil-expr)
stencil-expr)))
(let*
((keysig-expr (ly:stencil-expr keysig))
(keysig-xext (ly:stencil-extent keysig X))
(keysig-yext (ly:stencil-extent keysig Y))
(translation (cadr keysig-expr))
(accidentals (cdaddr keysig-expr))
(accidentals-Y (map cdr (map innermost-translation
accidentals)))
(coloured-accidentals (map colourise-single-accidental
accidentals
accidentals-Y)))
(ly:make-stencil
(list 'translate-stencil
translation
(cons 'combine-stencil coloured-accidentals))
keysig-xext
keysig-yext))))
#})
{
\colouredKeySignature \keysig-colors
\key des \major
c'1
\clef bass \break
c1
}
