%% LSR: http://lsr.di.unimi.it/LSR/Item?id=1016

%% Oultliner defs:
%% Credits Harm => http://lilypond.1069038.n5.nabble.com/Outliner-markup-command-tt185810.html#a185946
#(define (lists-map function ls)
"Apply @var{function} to @var{ls} and all of it sublists.

First it recurses over the children, then the function is applied to
@var{ls}."
    (if (list? ls)
        (set! ls (map (lambda (y) (lists-map function y)) ls))
        ls)
    (function ls))

#(define (uncolor-stencil stil)
"Delete colors from stencil @var{stil}"
  (let* ((x-ext (ly:stencil-extent stil X))
         (y-ext (ly:stencil-extent stil Y))
         (stil-expr (ly:stencil-expr stil))
         (get-caddr-if-condition
           (lambda (e)
             (if (and (list? e) (member 'color e))
                 ;; the stencil-expr of a colored stencil is of type
                 ;; (list 'color (list r g b) (list rest-of-stencil-expr))
                 ;; Thus we can be sure that (caddr e) is valid
                 ;; Even for an empty-stencil it evaluates to '()
                 (caddr e)
                 e))))
     (ly:make-stencil
       (lists-map get-caddr-if-condition stil-expr)
       x-ext
       y-ext)))
%% If LSR is upgrade to 2.20, please check whether this version 
%% of`stencil-whiteout-box-outline' is in the source.
#(define*-public (stencil-whiteout-box-outline
                 stil #:optional (thickness 0.3) (color white)
                 (angle-increments 16) (radial-increments 1))
  "This function works by creating a series of white or @var{color}
stencils radially offset from the original stencil with angles from
0 to 2*pi, at an increment of @code{angle-inc}, and with radii
from @code{radial-inc} to @var{thickness}.  @var{thickness} is how big
the white outline is, as a multiple of line-thickness.
@var{radial-increments} is how many copies of the white stencil we make
on our way out to thickness.  @var{angle-increments} is how many copies
of the white stencil we make between 0 and 2*pi."
  (if (or (not (positive? angle-increments))
          (not (positive? radial-increments)))
      (begin
       (ly:warning "Both angle-increments and radial-increments must be positive numbers.")
       stil)
      (let* ((2pi 6.283185307)
             (angle-inc (/ 2pi angle-increments))
             (radial-inc (/ thickness radial-increments)))

        (define (circle-plot ang dec radius original-stil new-stil)
          ;; ang (angle) and dec (decrement) are in radians, not degrees
          (if (<= ang 0)
              new-stil
              (circle-plot (- ang dec) dec radius original-stil
                (ly:stencil-add
                 new-stil
                 (ly:stencil-translate original-stil
                   (cons
                    (* radius (cos ang))
                    (* radius (sin ang))))))))

        (define (radial-plot radius original-stil new-stil)
          (if (<= radius 0)
              new-stil
              (ly:stencil-add new-stil
                (radial-plot
                 (- radius radial-inc)
                 original-stil
                 (circle-plot 2pi angle-inc
                   radius original-stil empty-stencil)))))

        (let ((whiteout-expr
                (ly:stencil-expr
                 (stencil-with-color
                  ;;;; `uncolor-stencil' applied
                  (radial-plot thickness (uncolor-stencil stil) empty-stencil)
                  color))))
          (ly:stencil-add
            (ly:make-stencil
              `(delay-stencil-evaluation ,(delay whiteout-expr)))
            stil)))))

#(define-markup-command (outliner layout props thickness color arg)
  (number? color? markup?)
  #:category other
  #:properties ((angle-increments 16)
                (radial-increments 1))

  (stencil-whiteout-box-outline
    (interpret-markup layout props arg)
    (* thickness (ly:output-def-lookup layout 'line-thickness))
    color
    angle-increments
    radial-increments))

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% A new G clef defs:
clef-henle =
#(ly:make-stencil
    ;; path line thickness is set to 0.001 
    `(path 0.001
       ;; path coordinates
       (moveto    0.00   0.45
         curveto   0.00   2.12   2.22   2.45   2.22   3.70
         curveto   2.22   3.70   2.22   4.19   2.01   4.19
         curveto   1.90   4.19   1.15   3.95   1.51   1.90
         lineto    2.06  -1.75
         curveto   2.13  -2.15   2.00  -2.83   1.20  -2.83
         curveto   0.70  -2.82   0.50  -2.50   0.50  -2.15
         curveto   0.50  -1.90   0.72  -1.65   0.95  -1.65
         curveto   1.21  -1.65   1.36  -1.80   1.36  -2.05
         curveto   1.36  -2.18   1.22  -2.40   0.95  -2.41
         curveto   0.90  -2.41   0.80  -2.43   0.80  -2.47
         curveto   0.80  -2.57   1.00  -2.68   1.20  -2.68
         curveto   1.50  -2.68   2.05  -2.53   1.91  -1.65
         lineto    1.30   2.40
         curveto   0.92   4.40   1.90   4.71   1.96   4.71
         curveto   2.20   4.71   2.36   4.00   2.36   3.55
         curveto   2.36   1.62   0.28   1.78   0.28   0.15
         curveto   0.28  -1.27   2.50  -1.34   2.50  -0.05
         curveto   2.50   0.76   1.07   0.82   1.07   0.05
         curveto   1.07  -0.25   1.10  -0.34   1.44  -0.61
         curveto   1.54  -0.68   1.47  -0.68   1.45  -0.68
         curveto   1.24  -0.68   0.83  -0.34   0.83   0.14
         curveto   0.83   0.60   1.20   1.05   1.70   1.05
         curveto   2.40   1.05   2.70   0.40   2.70   0.05
         curveto   2.70  -0.60   2.28  -1.11   1.40  -1.11
         curveto   0.70  -1.11   0.00  -0.50   0.00   0.45
         closepath)
        ;; path cap style
        round
        ;; path join style
        round
        ;; path filled?  #t or #f
        #t)
    ;; horizontal extent
    (cons 0 2.7)
    ;; vertical extent
    (cons -2.8 4.7))

%% Example:
#(set-global-staff-size 30)

some-music = \score {
  \relative { 
    \tempo "Allegro"
    c'_( d e f g a b c)
    \bar "|."
  }
  \layout { 
    indent = 0 
    \context {
      \Staff
      %%% Apply a new G clef ('outliner' works fine here too):
      \override Clef.stencil = #(lambda (grob)
          (let ((sz (ly:grob-property grob 'font-size 0.0)))
            (ly:stencil-scale clef-henle 1 1)))
    }
  }
}

\header {
  title = \markup {
    \with-color  #yellow
    %% 'ouliner' with x11 color:
    \outliner #3 #(x11-color 'orange) { Some music }
  }
  subtitle = \markup {
    %% 'ouliner' with rgb color:
    \outliner #2 #(rgb-color 1 0.5 0.5) { 
      \with-color #cyan { with a }
      \with-color #white funny 
      \with-color #red look 
      
    }
  }
}

%% Define a score as a markup 
%% in order to be able to apply 'outliner':
\markup\left-column {
  \with-color  #white
  \outliner #1.3 #(x11-color 'black)
  \score { \some-music }
  \vspace #2
  
  \fill-line\bold\fontsize #2  {
    \combine
    \with-color  #(x11-color 'DimGrey)
    \outliner #1.5 #(x11-color 'DimGrey)
    "Or shadowed:"
    \translate #'(0.05 . 0.1)
    \with-color  #white
    "Or shadowed:"
    
  }
  \vspace #1
  
  \combine
  \with-color  #(x11-color 'DimGrey)
  \outliner #1 #(x11-color 'DimGrey)
  \score { \some-music }
  \translate #'(0.05 . 0.1)
  \with-color  #white
  \score { \some-music }
}

\paper { tagline = ##f }