\version "2.19.8"

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% DIAGONAL-STROKE
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% taken from:
%% http://lilypond.org/doc/v2.18/Documentation/music-glossary/functional-harmony

#(define-markup-command (diagonal-stroke layout props arg)
  (markup?)
  #:category font
  #:properties ((font-size 0) (thickness 1.5) (extension 0.07))
"
 Draw a diagonal stroke through @var{arg} arg.
"
  (let*
   ((thick (* (magstep font-size)
      (ly:output-def-lookup layout 'line-thickness)))
    (underline-thick (* thickness thick))
    (markup (interpret-markup layout props arg))
    (x1 (car (ly:stencil-extent markup X)))
    (x2 (cdr (ly:stencil-extent markup X)))
    (y1 (car (ly:stencil-extent markup Y)))
    (y2 (cdr (ly:stencil-extent markup Y)))
    (dx (* extension (- x2 x1)))
    (dy (* extension (- y2 y1)))
    (line (make-line-stencil underline-thick
      (- x1 dx) (- y1 dy)
      (+ x2 dx) (+ y2 dy))))
   (ly:stencil-add markup line)))

stroke =
#(define-scheme-function (parser location color x-ext y-ext)
  ((symbol? #f) pair? pair?)
"
 Returns a diagonal stroke.
 For use with @code{\\mark}
"
#{
  \markup {
    \null
    \with-dimensions #empty-interval #empty-interval
    \with-color #(x11-color color)
    \diagonal-stroke 
    \with-dimensions #x-ext #y-ext
    \null
  }
#})

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% BRACKETS
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% after: http://lsr.di.unimi.it/LSR/Item?id=377
 
#(define-markup-command (square-bracket layout props dir) 
  (number?)
  #:properties  ((up 0)
                 (down 0)
                 (color #f))
"
 Draw a square-bracket.
 The vertical extension may be adjusted by overriding @var{up} and/or @var{down}
"
(let* ((th 0.2)
       (width (* 2.5 dir th))
       (ext (cons (+ -2.8 down)  (+ 2.8 up))))
       (stencil-with-color
         (ly:bracket Y ext th width)
         (x11-color color))))

leftBracket = {
  \once\override BreathingSign.text = 
    \markup 
      \with-dimensions #'(0 . 0 ) #'(0 . 0) 
      \override #'(color . grey)
      \override #'(down . -18)
      \square-bracket #1
  \once\override BreathingSign.break-visibility = #end-of-line-invisible
  \once\override BreathingSign.Y-offset = ##f
  \once\override Score.Clef.space-alist.breathing-sign = 
    #'(extra-space . 1.0)
  \once\override Score.KeyCancellation.space-alist.breathing-sign = 
    #'(extra-space . 1.0)
  \once\override Score.KeySignature.space-alist.breathing-sign = 
    #'(extra-space . 1.0)
  \once\override Score.TimeSignature.space-alist.breathing-sign = 
    #'(extra-space . 1.0)
  \once\override Score.BarLine.space-alist.breathing-sign = 
    #'(extra-space . 1.0)
  %% rearrange the order items
  \once \override Score.BreakAlignment #'break-align-orders =
    ##(
       (left-edge 
        cue-end-clef 
        ambitus 
        breathing-sign 
        clef 
        cue-clef 
        staff-bar 
        key-cancellation 
        key-signature 
        time-signature 
        custos) 
       (left-edge 
        cue-end-clef 
        ambitus 
        breathing-sign 
        clef 
        cue-clef 
        staff-bar 
        key-cancellation 
        key-signature 
        time-signature 
        custos) 
       (left-edge 
        ambitus 
        clef 
        key-cancellation 
        key-signature 
        time-signature 
        staff-bar 
        cue-clef 
        custos
        breathing-sign))
  
  \breathe 
}

rightBracket = {
  \once\override BreathingSign.text = 
    \markup 
      \with-dimensions #'(0 . 0 ) #'(0 . 0) 
      \override #'(down . -18)
      \square-bracket  #-1
  \once\override BreathingSign.Y-offset = ##f
  \breathe
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% FONT-SIZE AND COLOR
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% after: http://lsr.di.unimi.it/LSR/Item?id=889
mapList =
#(define-music-function (parser location fun lst)
   (ly:music-function? list?)
"
 Apply @var{fun}, which is supposed to be a music-function to all elements of
 @var{lst}
"
   #{ $@(map (lambda (s) #{ $fun $s #}) lst) #})
   
foo =
#(define-music-function (parser location item)
   (symbol-list-or-music?)
;; TODO: make the color variable
   #{ 
   	   \tweak font-size #-3 #item 
   	   \tweak color #grey #item 
   #})
   
revfoo=
#(define-music-function (parser location item)
   (symbol-list-or-music?)
   #{ 
   	   \tweak font-size ##f #item
   	   \tweak color ##f #item 
   #})
   
grey-tiny-grobs =
#(define-music-function (parser location music)(ly:music?)
"
 Return music with smaller font-size and colored grey.
 Note: some grobs can't be colored this way, p.e. @code{RehearsalMark}
"
#{
  \mapList #foo #(map car all-grob-descriptions)
  $music
  \mapList #revfoo #(map car all-grob-descriptions)
#})

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% EXAMPLE
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\new StaffGroup 
<<
\new Staff
\relative c' {
	c1
	\leftBracket
	\grey-tiny-grobs {
	  %% If there is a RehearsalMark already, use \markup instead, with
	  %% slightly different values
	  %%
	  %% you'll have to manually insert the values,
	  %% the color-argument is optional
	  \mark \stroke #'grey #'(4 . 46) #'(-22 . 2)
	  d8 
	    ^\markup 
	       \with-dimensions #empty-interval #empty-interval 
	       "grobs, stroke, bracket are colored grey"
	  d2..
	  \break
	  \mark \stroke #'(4 . 43) #'(-22 . 2)
	  e1 
	    ^\markup 
	       \with-color #black
	       \with-dimensions #empty-interval #empty-interval 
	       "stroke and bracket have default color"
	}
	\rightBracket
	f
}
\new Staff 
\relative c' {
	c \grey-tiny-grobs { d e } f
}
\new Staff 
\relative c' {
	c \grey-tiny-grobs { d e } f
}
>>