\version "2.19.25"

#(define anchor-color blue)

% slightly modified/improved version of
% alignTo from http://lists.gnu.org/archive/html/lilypond-user/2015-07/msg00235.html
alignTo =
#(define-music-function (conductor music) (ly:music? ly:music?)
   "Lengthen any note or rest in the sequence MUSIC just before each tag
that matches a tag in the sequence CONDUCTOR, so that the tags occur
at the same times from to the beginnings of MUSIC and CONDUCTOR."
   (define (find-sequence music)
     (or (fold-some-music
          (lambda (x) (music-is-of-type? x 'sequential-music))
          (lambda (x e1) (or e1 ; use the first nonempty sequence
                             (let ((es (ly:music-property x 'elements)))
                               (if (null? es) #f es))))
          #f
          music)
         (begin
          (ly:input-warning (ly:music-property music 'origin)
            "alignTo: cannot find sequential music")
          '())))
   (let loop ((aligner (find-sequence conductor))
              (alignee (find-sequence music))
              (time-left (ly:music-length conductor)))
     (case (length alignee)
       ((0) music)
       ((1) music)
       (else
        (let* ((a (first alignee)) ; music that might be lengthened,
                (b (second alignee)) ; if this music is tagged
                ; if a has an until property, add this to tag (which is b’s tags)
                (tag (if (not (null? (ly:music-property a 'until)))
                         (cons (ly:music-property a 'until)
                           (ly:music-property b 'tags))
                         (ly:music-property b 'tags)))
                (tail (and (not (null? tag))
                           (find-tail
                            (lambda (x)
                              (not (null? (lset-intersection
                                           eq? tag
                                           (ly:music-property x 'tags)))))
                            aligner))))
          (if tail
              (let ((tail-length (ly:music-length
                                  (make-sequential-music tail))))
                (if (ly:moment<? time-left tail-length)
                    (ly:input-warning (ly:music-property b 'origin)
                      "alignTo: already beyond conductor's tag ~a"
                      (lset-intersection
                       eq? tag
                       (ly:music-property (car tail) 'tags)))
                    (let ((newdur
                           (make-duration-of-length
                            (ly:moment-sub time-left tail-length))))
                      (if (eq? (ly:music-property a 'name) 'QuoteMusic)
                          (begin
                           (if (null? (ly:music-property a 'until))
                               (ly:input-warning (ly:music-property a 'origin)
                                 "alignTo: cannot scale quoteDuring correctly, please use quoteUntil"))
                           (ly:music-set-property! a 'element
                             (if (null? (ly:music-property a 'quote-color))
                                 (make-music 'SkipEvent
                                   'duration newdur)
                                 (color-music-if-point-and-click
                                  (make-music 'SkipEvent
                                    'duration newdur)))))
                          (ly:music-set-property! a 'duration newdur))))))
          (loop (or tail aligner)
            (cdr alignee)
            (ly:moment-sub time-left (ly:music-length a))))))))

useAndAlignTo =
#(define-music-function (global music) (ly:music? ly:music?)
   #{
     <<
       #global
       #(alignTo global music)
     >>
   #})

anchor =
#(define-music-function (text) (string?)
   (if (ly:get-option 'point-and-click)
       #{
         \tag #(string->symbol text)
         \single \override RehearsalMark.self-alignment-X = #LEFT
         \mark \markup \with-color #anchor-color #text
       #}
       #{
         \tag #(string->symbol text) s1*0
       #}))

until =
#(define-music-function (anchor) (string?)
   #{
     \tag #(string->symbol anchor) s1*0
   #})

% don’t redefine quoteUntil if advancedQuote.ily was included before
% because of different transposition behaviour
#(if (not (defined? 'quoteUntil))
     (define quoteUntil
       (define-music-function (what anchor) (string? string?)
         (make-music 'QuoteMusic
           'until (string->symbol anchor)
           'quoted-music-name what))))