Maybe it would be possible to refine harm's function (which at the
moment uses stencil-with-color, which simply puts a color-selection
command in front of the stencil expression as far as I can see) so
that it walks through the page stencil expression and turns any
explicit "white" into the selected background color. That could work,
but it would mess up any construction where white is being used in a
non-background meaning (i.e. for some rehearsal mark with
white-on-black design) - which would probably be acceptable as a first
approximation.
I just tested this approach: This is possible, but please don't use my
terrible proof-of-concept hack (which misses, at the very least, a call
to normalize-color which I couldn't make available in \paper, and a
thorough cleaning up of the recursion logic) in production work.
\version "2.24.0"
\paper {
background-color = #(x11-color "gray20")
print-color = "ivory"
#(define (page-post-process layout pages)
(let ((print-color (ly:output-def-lookup $defaultpaper
'print-color #f))
(background-color
(ly:output-def-lookup $defaultpaper 'background-color #f)))
(define (de-white-stencil-expr expr)
(if (pair? expr)
(begin
(if (eq? (car expr) 'color)
(if (equal? (cadr expr) white)
(set-car! (cdr expr) background-color)))
(cons (de-white-stencil-expr (car expr))
(de-white-stencil-expr (cdr expr))))
expr))
(for-each
(lambda (page)
(let* ((page-stencil (ly:prob-property page 'stencil))
(X-ext (ly:stencil-extent page-stencil X))
(Y-ext (ly:stencil-extent page-stencil Y)))
(set! (ly:prob-property page 'stencil)
(if (not background-color)
(stencil-with-color page-stencil print-color)
(ly:stencil-add
(stencil-with-color (make-filled-box-stencil
X-ext Y-ext)
background-color)
(stencil-with-color
(ly:make-stencil
(de-white-stencil-expr (ly:stencil-expr
page-stencil))
X-ext
Y-ext)
print-color))))))
pages)))
}
\layout { }
\markup { Here’s an example of \override #'(color . "green") \whiteout
\line { whiteout in markup. } }
{ \override Staff.TimeSignature.whiteout = ##t 1 } \addlyrics { test }
Lukas
