\version "2.19.27"

%% CUSTOM GROB PROPERTIES

% Taken from http://www.mail-archive.com/lilypond-user%40gnu.org/msg97663.html
% (Paul Morris)

% function from "scm/define-grob-properties.scm" (modified)
#(define (cn-define-grob-property symbol type?)
   (set-object-property! symbol 'backend-type? type?)
   (set-object-property! symbol 'backend-doc "custom grob property")
   symbol)

% For internal use.
#(cn-define-grob-property 'text-spanner-stencils list?)

% user interface
#(cn-define-grob-property 'text-spanner-line-count number-list?)

% List of booleans describing connections between text items regardless
% of line breaks.
#(cn-define-grob-property 'connectors list?)

% How much space between line and object to left and right?
% Default is '(0.0 . 0.0).
#(cn-define-grob-property 'line-X-offset number-pair?)

% Vertical shift of connector line, independenf of texts.
#(cn-define-grob-property 'line-Y-offset number?)

#(define (get-text-distribution text-list line-extents)
   ;; Given a list of texts and a list of line extents, attempt to
   ;; find a decent line distribution.  The goal is to put more texts
   ;; on longer lines, while ensuring that first and last lines are texted.
   ;; TODO: ideally, we should consider extents of text, rather than
   ;; simply their number.
   (let* ((line-count (length line-extents))
          (text-count (length text-list))
          (line-lengths
           (map (lambda (line) (interval-length line))
             line-extents))
          (total-line-len (apply + line-lengths))
          (exact-per-line
           (map (lambda (line-len)
                  (* text-count (/ line-len total-line-len)))
             line-lengths))
          ;; First and last lines can't be untexted.
          (adjusted
           (let loop ((epl exact-per-line) (idx 0) (result '()))
             (if (null? epl)
                 result
                 (if (and (or (= idx 0)
                              (= idx (1- line-count)))
                          (< (car epl) 1))
                     (loop (cdr epl) (1+ idx)
                       (append result (list 1.0)))
                     (loop (cdr epl) (1+ idx)
                       (append result (list (car epl)))))))))

     ;; The idea is to raise the "most roundable" line's count, then the
     ;; "next most roundable," and so forth, until we account for all texts.
     ;; Everything else is rounded down (except those lines which need to be
     ;; bumped up to get the minimum of one text), so we shouldn't exceed our
     ;; total number of texts.
     ;; TODO: Need a promote-demote-until-flush to be safe, unless this is
     ;; mathematically sound!
     (define (promote-until-flush result)
       (let* ((floored (map floor result))
              (total (apply + floored)))

         (if (>= total text-count)
             (begin
              ;(format #t "guess: ~a~%~%~%" result)
              floored)
             (let* ((decimal-amount
                     (map (lambda (x) (- x (floor x))) result))
                    (maximum (apply max decimal-amount))
                    (max-location
                     (list-index
                      (lambda (x) (= x maximum))
                      decimal-amount))
                    (item-to-bump (list-ref result max-location)))
               ;(format #t "guess: ~a~%" result)
               (list-set! result max-location (1+ (floor item-to-bump)))
               (promote-until-flush result)))))

     (let ((result (map inexact->exact
                     (promote-until-flush adjusted))))
       (if (not (= (apply + result) text-count))
           ;; If this doesn't work, discard, triggering crude
           ;; distribution elsewhere.
           '()
           result))))

#(define (get-connectors grob text-distribution)
   "Modify @var{text-distribution} to reflect line breaks.  Return a list
of lists of booleans representing whether to draw a connecting line
between successive texts."
   ;; The property TextSpanner.connectors holds a list of booleans representing
   ;; whether a line will be drawn between two texts.  (Thus, there will be
   ;; one fewer boolean than texts.)  This does NOT include spacers: "".
   ;; This function transforms the list of booleans into a list of lists
   ;; of booleans which reflects line breaks and the additional lines
   ;; which must be drawn.
   ;;
   ;; Given an input of '(#t #t #f)
   ;;
   ;;    '((#t        #t            #f))
   ;; one_ _ _ _two_ _ _ _ _three        four  (one line)
   ;;
   ;;     '((#t       #t)
   ;; one_ _ _ _two_ _ _ _ _                   (two lines)
   ;;   (#t         #f))
   ;; _ _ _ _three     four
   ;;
   ;;     '((#t)
   ;; one_ _ _ _                               (four lines/blank)
   ;; (#t       #t)
   ;; _ _ _two_ _ _
   ;;      (#t)
   ;; _ _ _ _ _ _ _
   ;; (#t      #f))
   ;; _ _three    four
   (let* ((connectors? (ly:grob-property grob 'connectors))
          (text-distribution (vector->list text-distribution)))

     (if (pair? connectors?)
         (let loop ((td text-distribution)
                    (c? connectors?)
                    (result '()))
           (if (null? td)
               result
               (let inner ((texts (car td))
                           (bools c?)
                           (inner-result '()))
                 (cond
                  ((null? (cdr texts))
                   (loop (cdr td) bools
                     (append result (list inner-result))))
                  ((null? bools)
                   (ly:warning
                    "too few connections specified.  Reverting to default.")
                   '())
                  ;; Ignore spacers since they don't represent a new line.
                  ((equal? "" (cadr texts))
                   (inner (cdr texts) bools inner-result))
                  ((equal? (cadr texts) #{ \markup \null #})
                   (inner (cdr texts) bools
                     (append inner-result (list (car bools)))))
                  (else
                   (inner (cdr texts) (cdr bools)
                     (append inner-result (list (car bools)))))))))
         '())))


#(define (get-line-arrangement siblings extents texts)
   "Given a list of spanner extents and texts, return a vector of lists
of the texts to be used for each line.  Using @code{'()} for @var{siblings}
returns a vector for an unbroken spanner."
   (let ((sib-len (length siblings)))
     (if (= sib-len 0)
         ;; only one line...
         (make-vector 1 texts)
         (let* ((texts-len (length texts))
                (text-counts
                 (ly:grob-property
                  (car siblings) 'text-spanner-line-count))
                (text-counts
                 (cond
                  ((pair? text-counts) text-counts) ; manual override
                  ((null? siblings) '())
                  (else (get-text-distribution texts extents))))
                (text-counts
                 (if (and (pair? text-counts)
                          (not (= (apply + text-counts) texts-len)))
                     (begin
                      (ly:warning "Count doesn't match number of texts.")
                      '())
                     text-counts))
                (text-lines (make-vector sib-len 0))
                ;; If user hasn't specified a count elsewhere, or the result
                ;; from 'get-text-distribution' failed, we have this method.
                ;; Populate vector in a simple way: with two lines,
                ;; give one text to the first line, one to the second,
                ;; a second for the first, and second for the second--
                ;; and so forth, until all texts have been exhausted.  So
                ;; for 3 lines and 7 texts we would get this arrangement:
                ;; 3, 2, 2.
                (text-counts
                 (cond
                  ((null? text-counts)
                   (let loop ((txts texts) (idx 0))
                     (cond
                      ((null? txts) text-lines)
                      ;; We need to ensure that the last line has text.
                      ;; This may require skipping lines.
                      ((and (null? (cdr txts))
                            (< idx (1- sib-len))
                            (= 0 (vector-ref text-lines (1- sib-len))))
                       (vector-set! text-lines (1- sib-len) 1)
                       text-lines)
                      (else
                       (vector-set! text-lines idx
                         (1+ (vector-ref text-lines idx)))
                       (loop (cdr txts)
                         (if (= idx (1- sib-len)) 0 (1+ idx)))))))
                  (else (set! text-lines (list->vector text-counts)))))
                ;; read texts into vector
                (texts-by-line
                 (let loop ((idx 0) (texts texts))
                   (if (= idx sib-len)
                       text-lines
                       (let ((num (vector-ref text-lines idx)))
                         (vector-set! text-lines idx
                           (list-head texts num))
                         (loop (1+ idx)
                           (list-tail texts num)))))))

           text-lines))))

#(define (add-markers text-lines)
   ;; Markers are added to the broken edges of spanners to serve as anchors
   ;; for connector lines beginning and ending systems.
   ;; Add null-markup at the beginning of lines 2...n.
   ;; Add null-markup at the end of lines 1...(n-1).
   ;; Note: this modifies the vector 'text-lines'.
   (let loop ((idx 0))
     (if (= idx (vector-length text-lines))
         text-lines
         (begin
          (if (> idx 0)
              (vector-set! text-lines idx
                (cons #{ \markup \null #}
                  (vector-ref text-lines idx))))
          (if (< idx (1- (vector-length text-lines)))
              (vector-set! text-lines idx
                (append (vector-ref text-lines idx)
                  (list #{ \markup \null #}))))
          (loop (1+ idx))))))

%% Adapted from 'justify-line-helper' in scm/define-markup-commands.scm.
#(define (markup-list->stencils-and-extents-for-line grob texts extent padding)
   "Given a list of markups @var{texts}, return a list of stencils and extents
spread along an extent @var{extent}, such that the intervening spaces are
equal."
   (let* ((orig-stencils
           (map (lambda (a) (grob-interpret-markup grob a)) texts))
          (stencils
           (map (lambda (stc)
                  (if (ly:stencil-empty? stc X)
                      (ly:make-stencil (ly:stencil-expr stc)
                        '(0 . 0) (ly:stencil-extent stc Y))
                      stc))
             orig-stencils))
          (line-contents
           (if (= (length stencils) 1)
               (list point-stencil (car stencils) point-stencil)
               stencils))
          (text-extents
           (map (lambda (stc) (ly:stencil-extent stc X))
             line-contents))
          (te1 text-extents)
          ;; How much shift is necessary to align left edge of first
          ;; stencil with extent?  Apply this shift to all stencils.
          (text-extents
           (map (lambda (stc)
                  (coord-translate
                   stc
                   (- (car extent) (caar text-extents))))
             text-extents))
          ;; how much does the last stencil need to be translated for
          ;; its right edge to touch the end of the spanner?
          (last-shift (- (cdr extent) (cdr (last text-extents))))
          (word-count (length line-contents))
          ;; Make a list of stencils and their extents, scaling the
          ;; extents across extent. The right edge of the last stencil
          ;; is now aligned with the right edge of the spanner.  The
          ;; first stencil will be moved 0.0, the last stencil the
          ;; amount given by last-shift.
          (stencils-shifted-extents-list
           (let loop ((contents line-contents) (exts text-extents)
                       (idx 0) (result '()))
             (if (null? contents)
                 result
                 (loop
                  (cdr contents) (cdr exts) (1+ idx)
                  (append result
                    (list
                     (cons (car contents)
                       (coord-translate
                        (car exts)
                        (* idx
                          (/ last-shift (1- word-count)))))))))))
          ;; Remove non-marker spacers from list of extents.  This is done
          ;; so that a single line is drawn to cover the total gap rather
          ;; than several. (A single line is needed since successive dashed
          ;; lines will not connect properly.)
          (stencils-extents-list-no-spacers
           (let loop ((orig stencils-shifted-extents-list) (idx 0) (result '()))
             (cond
              ((= idx (length stencils-shifted-extents-list)) result)
              ;; Ignore first and last stencils, which--if point stencil--
              ;; will be markers.
              ((or (= idx 0)
                   (= idx (1- (length stencils-shifted-extents-list))))
               (loop (cdr orig) (1+ idx)
                 (append result (list (car orig)))))
              ;; Remove spacers.  Better way to identify them than comparing
              ;; left and right extents?
              ((= (cadar orig) (cddar orig))
               (loop (cdr orig) (1+ idx) result))
              ;; Keep any visible stencil.
              (else (loop (cdr orig) (1+ idx)
                      (append result (list (car orig)))))))))

     stencils-extents-list-no-spacers))

#(define (check-for-overlaps stil-extent-list)
   (let* ((collision
           (lambda (line)
             (let loop ((exts line) (result '()))
               (if (null? (cdr exts))
                   result
                   (loop (cdr exts)
                     (append result
                       (list
                        (not (interval-empty?
                              (interval-intersection
                               (cdar exts) (cdadr exts)))))))))))
          ;; List of lists of booleans comparing first element to second,
          ;; second to third, etc., for each line.  #f = no collision
          (all-successive-collisions
           (map (lambda (line) (collision line))
             stil-extent-list)))

     ;; For now, just print a warning and return #t if any collision anywhere.
     (let loop ((lines all-successive-collisions) (idx 0) (collisions? #f))
       (cond
        ((null? lines) collisions?)
        ((any (lambda (p) (eq? p #t)) (car lines))
         (ly:warning
          "overlap(s) found on line ~a; redistribute manually"
          (1+ idx))
         (loop (cdr lines) (1+ idx) #t))
        (else
         (loop (cdr lines) (1+ idx) collisions?))))))


#(define (make-distributed-line-stencil grob stil-stil-extent-list connectors)
   "Take a list of stencils and arbitrary extents and return a combined
stencil conforming to the given extents.  Lines separate the stencils.
TODO: lines should be suppressed if not enough space."
   (let* ((padding (ly:grob-property grob 'line-X-offset (cons 0.0 0.0)))
          (padding-L (car padding))
          (padding-R (cdr padding))
          (padded-stencils-extents-list
           (let loop ((orig stil-stil-extent-list) (idx 0) (result '()))
             (cond
              ((= idx (length stil-stil-extent-list)) result)
              ;; don't widen line markers
              ((= (cadar orig) (cddar orig))
               (loop (cdr orig) (1+ idx)
                 (append result (list (car orig)))))
              ;; right padding only if object starts line
              ((= idx 0)
               (loop (cdr orig) (1+ idx)
                 (append
                  result
                  (list (cons (caar orig)
                          (coord-translate
                           (cdar orig) (cons 0 padding-R)))))))
              ;; left padding only if object ends a line
              ((= idx (1- (length stil-stil-extent-list)))
               (loop (cdr orig) (1+ idx)
                 (append
                  result
                  (list (cons (caar orig)
                          (coord-translate
                           (cdar orig) (cons (- padding-L) 0.0)))))))
              ;; otherwise right- and left-padding
              (else
               (loop (cdr orig) (1+ idx)
                 (append
                  result
                  (list (cons (caar orig)
                          (coord-translate
                           (cdar orig)
                           (cons (- padding-L)
                             padding-R))))))))))
          ;; Spaces between the text stencils will be filled with lines.
          (spaces
           (if (> (length padded-stencils-extents-list) 1)
               (let loop ((orig padded-stencils-extents-list)
                          (result '()))
                 (if (null? (cdr orig))
                     result
                     (loop
                      (cdr orig)
                      (append
                       result
                       (list (cons (cdr (cdr (first orig)))
                               (car (cdr (second orig)))))))))
               '()))
          (line-contents
           (let loop ((contents stil-stil-extent-list)
                      (stil empty-stencil))
             (if (null? contents)
                 stil
                 (loop
                  (cdr contents)
                  (ly:stencil-add stil
                    (ly:stencil-translate-axis
                     (caar contents)
                     (- (car (cdr (car contents)))
                       (car (ly:stencil-extent (car (car contents)) X)))
                     X))))))
          ;; By default, lines are drawn between all texts
          (join-all (null? connectors))
          (offset-Y (ly:grob-property grob 'line-Y-offset 0.0))
          (line-contents
           (let loop ((exts spaces)
                      (result line-contents)
                      (join connectors))
             (if (null? exts)
                 result
                 (loop
                  (cdr exts)
                  (if (and
                       ;; space too short for line
                       (not (interval-empty? (car exts)))
                       (or join-all
                           (car join)))
                      (ly:stencil-add
                       result
                       ;(make-line-stencil 0.1
                       ;; For versions < 2.19.27, replace line below with
                       ;; commented line.  No dashed lines!
                       (ly:line-interface::line grob
                         (caar exts) offset-Y
                         (cdar exts) offset-Y))
                      result)
                  (if join-all join (cdr join)))))))

     line-contents))


#(define (make-stencils grob siblings stil-extent-list connectors)
   ;; entry point for stencil construction
   (if (null? siblings)
       (list (make-distributed-line-stencil grob
               (car stil-extent-list)
               (if (pair? connectors)
                   (car connectors)
                   connectors)))
       (map (lambda (sib)
              (make-distributed-line-stencil sib
                (list-ref
                 stil-extent-list
                 (list-index
                  (lambda (x) (eq? x sib))
                  siblings))
                (if (pair? connectors)
                    (list-ref
                     connectors
                     (list-index
                      (lambda (x) (eq? x sib))
                      siblings))
                    '())))
         siblings)))

%% Based on addTextSpannerText, by Thomas Morley.  See
%% http://www.mail-archive.com/lilypond-user%40gnu.org/msg81685.html
addTextSpannerText =
#(define-music-function (texts) (list?)
   (if (< (length texts) 2)
       (begin
        (ly:warning "At least two texts required for `addTextSpannerText'.")
        (make-music 'Music))

       #{
         % The following overrides of 'bound-details are needed to give the
         % correct length to the default spanner we replace.
         \once \override TextSpanner.bound-details.left.text = #(car texts)
         \once \override TextSpanner.bound-details.left-broken.text = ##f
         \once \override TextSpanner.bound-details.right.text = #(last texts)
         \once \override TextSpanner.bound-details.right-broken.text = ##f

         \once \override TextSpanner.stencil =
         #(lambda (grob)
            (let* (;; have we been split?
                    (orig (ly:grob-original grob))
                    ;; if yes, get the split pieces (our siblings)
                    (siblings (if (ly:grob? orig)
                                  (ly:spanner-broken-into orig)
                                  '()))
                    (stils (ly:grob-property grob 'text-spanner-stencils)))
              ;; If stencils haven't been calculated, calculate them.  Once
              ;; we have results prompted by one sibling, no need to go
              ;; through elaborate calculation (stencils, collisions, ideal
              ;; line contents...) for remaining pieces.
              (if (null? stils)
                  (let* (;; pieces and their default stencils
                          (grobs-and-stils
                           (if (null? siblings) ; unbroken
                               (list (cons grob (ly:line-spanner::print grob)))
                               (map
                                (lambda (sib)
                                  (cons sib (ly:line-spanner::print sib)))
                                siblings)))
                          (line-stils
                           (map (lambda (gs) (cdr gs)) grobs-and-stils))
                          (line-extents
                           (map (lambda (s) (ly:stencil-extent s X))
                             line-stils))
                          (our-stil
                           (cdr (find (lambda (x) (eq? (car x) grob))
                                  grobs-and-stils)))
                          (padding (ly:grob-property grob 'padding 0.0)))

                    (define (get-stil-extent-list text-distrib)
                      (if (null? siblings)
                          (list
                           (markup-list->stencils-and-extents-for-line
                            grob
                            (vector-ref text-distrib 0)
                            (ly:stencil-extent our-stil X)
                            padding))
                          (map
                           (lambda (sib)
                             (markup-list->stencils-and-extents-for-line
                              sib
                              (vector-ref text-distrib
                                (list-index
                                 (lambda (y) (eq? y sib)) siblings))
                              (ly:stencil-extent
                               (cdr (find
                                     (lambda (z) (eq? (car z) sib))
                                     grobs-and-stils))
                               X)
                              padding))
                           siblings)))

                    (let*
                     (;; vector which gives the text for unbroken spanner
                       ;; or for siblings.  This is a preliminary
                       ;; arrangement, to be tweaked below.
                       (text-distribution
                        (get-line-arrangement siblings line-extents texts))

                       (text-distribution (add-markers text-distribution))
                       (connectors (get-connectors grob text-distribution))
                       (all-stils-and-extents
                        (get-stil-extent-list text-distribution))
                       ;; warning printed
                       (overlaps (check-for-overlaps all-stils-and-extents))
                       ;; convert stencil/extent list into finished stencil
                       (line-stils
                        (make-stencils
                         grob siblings all-stils-and-extents connectors)))

                     (if (null? siblings)
                         (set! (ly:grob-property grob 'text-spanner-stencils)
                               line-stils)
                         (for-each
                          (lambda (sib)
                            (set!
                             (ly:grob-property sib 'text-spanner-stencils)
                             line-stils))
                          siblings))

                     (set! stils line-stils))))

              ;; Return our stencil
              (if (null? siblings)
                  (car stils)
                  (list-ref stils
                    (list-index (lambda (x) (eq? x grob)) siblings)))))
       #}))


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% EXAMPLES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\markup \bold "Default (no inner text possible)"

\relative c'' {
  \textLengthOff
  \override TextSpanner.bound-details.left.text = #"ral"
  \override TextSpanner.bound-details.left-broken.text = ##f
  \override TextSpanner.bound-details.right.text = #"do"
  \override TextSpanner.bound-details.right-broken.text = ##f
  c,1\startTextSpan
  d'1\stopTextSpan
}

\markup \bold "All on one line"

\relative c' {
  \addTextSpannerText #'("ral" "len" "tan" "do")
  c1\startTextSpan
  d'1\stopTextSpan
}

\markup \bold "Broken"

\relative c' {
  %% to show collision detection
  %\override TextSpanner.text-spanner-line-count = #'(2 2)
  \addTextSpannerText #'("ral" "len" "tan" "do")
  c1\startTextSpan
  \break
  d'1\stopTextSpan
}

\markup \bold "Empty line/manual distribution"

\relative c' {
  \override TextSpanner.text-spanner-line-count = #'(1 0 1 1)
  \addTextSpannerText #(list "one" "two" "three")
  c1~\startTextSpan
  \break
  c1~
  \break
  c1~
  \break
  c1\stopTextSpan
}

\markup \bold "Changes of ends"

\relative c' {
  \addTextSpannerText #'("one" "two" "three")
  c1\startTextSpan
  c1\stopTextSpan
  \once \override TextSpanner.bound-details.left.padding = #-2
  \once \override TextSpanner.bound-details.right.padding = #-5
  \addTextSpannerText #'("one" "two" "three")
  c1\startTextSpan
  c1\stopTextSpan
}

\markup \bold "Markups"

\relative c' {
  \addTextSpannerText #(list
                        #{ \markup "one" #}
                        #{ \markup "two" #}
                        #{ \markup "three" #})
  c1\startTextSpan
  c1\stopTextSpan
  \addTextSpannerText
  #(list
    #{ \markup "one" #}
    #{ \markup \with-color #red \translate #'(-3 . 0) "two" #}
    #{ \markup "three" #})
  c1\startTextSpan
  c1\stopTextSpan
  \override TextSpanner.style = #'dotted-line
  \override TextSpanner.dash-period = #0.5
  \addTextSpannerText #(list
                        #{ \markup \right-align  "one" #}
                        "two"
                        #{ \markup \center-align "three" #})
  c1\startTextSpan
  c1\stopTextSpan
}

\relative c'' {
  \override TextSpanner.style = #'zigzag
  \override TextSpanner.line-X-offset = #'(0.5 . 0.5)
  \addTextSpannerText
  #(list
    #{ \markup \draw-circle #1 #0.2 ##f #}
    #{ \markup \with-color #grey \draw-circle #1 #0.2 ##t #}
    #{ \markup \draw-circle #1 #0.2 ##t #}
    #{ \markup \with-color #grey \draw-circle #1 #0.2 ##t #}
    #{ \markup \draw-circle #1 #0.2 ##f #} )
  c1\startTextSpan
  %\break
  d'1 d\stopTextSpan
}

\relative c'' {
  \override TextSpanner.line-X-offset = #'(0.7 . 0.4)
  \override TextSpanner.style = #'trill
  r2 r4 r8 r16
  \addTextSpannerText
  #(append
    (make-list 29
      #{ \markup \general-align #Y #CENTER \musicglyph #"scripts.trill" #})
    (list #{ \markup \musicglyph #"scripts.caesura.straight" #} ))
  d'16~\startTextSpan
  \break
  \repeat unfold 3 {
    d1~
    \break
  }
  d8~ d\stopTextSpan r4 r2
}

\markup \bold "Showing/hiding connectors"

\relative c' {
  c1
  \override TextSpanner.padding = 3
  \override TextSpanner.direction = #DOWN
  \override TextSpanner.connectors = #'(#f #f #f #t)
  \override TextSpanner.text-spanner-line-count = #'(4 0 1)
  \addTextSpannerText
  #(list "poco" "a" "poco" "dim." #{ \markup \dynamic "mf" #})
  c1\startTextSpan
  c1 c1
  \break
  c1 c1 c1 c1
  \break
  c1 c1 c1
  c1\stopTextSpan
}

\markup \bold "Raising/lowering of connector line"

\relative c' {
  \override TextSpanner.line-X-offset = #'(0.5 . 0.5)
  \override TextSpanner.line-Y-offset = 0.5
  \addTextSpannerText #'("ral" "len" "tan" "do")
  c1\startTextSpan
  d'1\stopTextSpan
}

\layout {
  indent = 0
  ragged-right = ##f
}