in Snippets - LilyPond

Staff notation 111
}
Adding indicators to staves which get split after a break
This snippet defines the \splitStaffBarLine command, which adds arrows in north-east and
south-east directions at a bar line, to denote that several voices sharing a staff will each continue
on a staff of their own in the next system.
#(define-markup-command (arrow-at-angle layout props angle-deg length fill)
(number? number? boolean?)
(let* (
;; PI-OVER-180 and degrees->radians are taken from flag-styles.scm
(PI-OVER-180 (/ (atan 1 1) 45))
(degrees->radians (lambda (degrees) (* degrees PI-OVER-180)))
(angle-rad (degrees->radians angle-deg))
(target-x (* length (cos angle-rad)))
(target-y (* length (sin angle-rad))))
(interpret-markup layout props
(markup
#:translate (cons (/ target-x 2) (/ target-y 2))
#:rotate angle-deg
#:translate (cons (/ length -2) 0)
#:concat (#:draw-line (cons length 0)
#:arrow-head X RIGHT fill)))))
splitStaffBarLineMarkup = \markup \with-dimensions #'(0 . 0) #'(0 . 0) {
\combine
\arrow-at-angle #45 #(sqrt 8) ##f
\arrow-at-angle #-45 #(sqrt 8) ##f
}
splitStaffBarLine = {
\once \override Staff.BarLine #'stencil =
#(lambda (grob)
(ly:stencil-combine-at-edge
(ly:bar-line::print grob)
X RIGHT
(grob-interpret-markup grob splitStaffBarLineMarkup)
0))
\break
}