Affecting items only on the left or right of a line break (BarLines, KeySignatures, Clefs, etc.)

If you want to affect the behaviour (color, rotation, translate, etc.) of an item at a line break only on the left or the right side (like BarLines, KeySignatures, Clefs, TimeSignatures, etc.), use the definitions and functions as defined here. Several other definitions are possible by using this examples.

\version "2.24.0"

%% http://lsr.di.unimi.it/LSR/Item?id=775

% here starts the snippet:

% Contributed by harm6
% Code is taken from output-lib.scm and modified.
% This snippet was developed with 2.14.2, but there is no difficulty with 2.12.2
% Several other Definitions and functions are possible.

%------------ Definitions

#(define (color-at-line-begin g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) RIGHT))
      (ly:grob-set-property! g 'color red)))
      
#(define (rotate-at-line-begin g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) RIGHT))
      (ly:grob-set-property! g 'rotation (list 145 0 0))))
      
#(define (translate-at-line-begin g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) RIGHT))
      (and (ly:grob-translate-axis! g -3.5 Y)
           (ly:grob-translate-axis! g -3.5 X))
      ))
      
#(define (color-at-line-end g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) LEFT))
      (ly:grob-set-property! g 'color green)))
         
#(define (rotate-at-line-end g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) LEFT))
      (ly:grob-set-property! g 'rotation (list 45 0 0))))
      
%---------- music-functions
 
% In the music-functions colors are to be specified like rgb-colors.

colorBarLineBeg =      
#(define-music-function (color)(list?)
 (define (color-at-line-begin g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) RIGHT))
      (ly:grob-set-property! g 'color color)))
#{
        \once\override Staff.BarLine.after-line-breaking = #color-at-line-begin
#})

colorBarLineEnd =      
#(define-music-function (color)(list?)
 (define (color-at-line-end g)
  (if (and (ly:item? g)
	   (equal? (ly:item-break-dir g) LEFT))
      (ly:grob-set-property! g 'color color)))
#{
        \once\override Staff.BarLine.after-line-breaking = #color-at-line-end
#})
%---------------------- Test ---------------------------------------------------

\paper {
        ragged-right =##f
        indent = 0
        line-width = 90
}

\relative g' {
        	\once\override Staff.Clef.after-line-breaking = #color-at-line-begin
        	\repeat volta 2 { c1 }
\break
        	\once\override Staff.BarLine.after-line-breaking = #translate-at-line-begin 
        	\repeat volta 2 { d }
\break
        	\once\override Staff.TimeSignature.after-line-breaking = #rotate-at-line-begin
        	\time 2/4
        	\repeat volta 2 { c2 }
\break
        	\once\override Staff.KeySignature.after-line-breaking = #color-at-line-end
        	\key cis\major 
        	\repeat volta 2 { dis }
\break
        	\once\override Staff.BarLine.after-line-breaking = #color-at-line-end
        	\once\override Staff.KeySignature.after-line-breaking = #rotate-at-line-begin
        	\once\override Staff.Clef.after-line-breaking = #rotate-at-line-end
        	\once\override Staff.TimeSignature.after-line-breaking = #color-at-line-begin
        	\clef alto
        	\time 4/8
        	\repeat volta 2 { cis }
\break
        	\colorBarLineBeg #'(0 1 0)
        	\time 2/4
        	\repeat volta 2 { dis, }
\break
	\colorBarLineEnd #'(0.6 0 1)
	\repeat volta 2 { cis }

} 

\paper { tagline = ##f }