\version "2.16.2"

% left-hand finger guide finger between notes
#(define (gx slope character fingering)
  ;; Purpose
  ;;   add ornamentation character before fingering symbol
  ;; Parameters
  ;;   slope : angle of rotation around right centre
  ;;   character : ornamentation character for fingering
  ;;   fingering : fingering designation for note
  ;; Examples
  ;;   (gx 0 #x2013 fingering)
  ;;       unicode #x2011 <-> #x2015 are different length "-" punctuation
  (let ((music (make-music 'FingeringEvent)))
    (set! (ly:music-property music 'tweaks)
          (acons 'stencil
                 (lambda (grob)
                   (let* ((finger (ly:music-property fingering 'digit))
                          (finger-stil (grob-interpret-markup grob (number->string finger)))
                          (finger-stil-ext (ly:stencil-extent finger-stil X))
                          (guide-char character)
                          (guide-stil (grob-interpret-markup grob (markup #:char guide-char)))
                          (stil
                            (ly:stencil-combine-at-edge
                              (ly:stencil-rotate guide-stil slope 1 0) ;; rotate "slope" around right centre
                              X 1   ;; combine stencils along X-axis on right
                              finger-stil
                              0.2)) ;; add padding to move guide slightly left from finger number
                          (stil-ext-X (ly:stencil-extent stil X))
                          (stil-ext-Y (ly:stencil-extent stil Y))
                          ;; Alter X-extents of combined stencil so that it
                          ;; will be positioned with the number centered
                          ;; over the note.
                          (adj-stil
                            ;; leave fingerings oriented to side alone
                            (if (= 0 (ly:grob-property grob 'side-axis))
                                stil
                                (ly:make-stencil
                                  (ly:stencil-expr stil)
                                    (coord-translate
                                      stil-ext-X
                                      (* 0.5 (- (cdr stil-ext-X) (interval-length finger-stil-ext))))
                                    stil-ext-Y))))
                   adj-stil))
                 (ly:music-property music 'tweaks)))
    music))

% guide-neutral
%   <c-\gn-1>4  c4^\gn^2  c4-\gn-3  c4_\gn_4
gn = #(define-music-function (parser location fingering) (ly:music?)
           (gx 0 #x2013 fingering))
% guide-down
%   <c-\gd-1>4  c4^\gd^2  c4-\gd-3  c4_\gd_4
gd = #(define-music-function (parser location fingering) (ly:music?)
           (gx 20 #x2013 fingering))
% guide-up
%   <c-\gu-1>4  c4^\gu^2  c4-\gu-3  c4_\gu_4
gu = #(define-music-function (parser location fingering) (ly:music?)
           (gx -20 #x2013 fingering))
% guide slope
%   <c-\gsl #-15 -1>4  c4^\gsl #45 ^2  c4-\gsl #-15 -3  c4_\gsl# -14 _4
gsl = #(define-music-function (parser location slope fingering) (number? ly:music?)
           (gx slope #x2013 fingering))
% guide slope unicode
%   <c-\gsl #-15 ##x2011 -1>4  c4^\gsl #45 ##x2012 ^2  c4-\gsl #-15 ##x2013 -3  c4_\gsl #-14 ##x2014 _4
gsn = #(define-music-function (parser location slope unicode fingering) (number? number? ly:music?)
                (gx slope unicode fingering))
% guide slope character
%   <c-\gsl #-15 ##\+ -1>4  c4^\gsl #45 ##\+ ^2  c4-\gsl #-15 ##\! -3  c4_\gsl #-14 ##\! _4
gsc = #(define-music-function (parser location slope character fingering) (number? char? ly:music?)
                (gx slope (char->integer character) fingering))

\relative c'' {
  <fis^4 b, a dis,>2 <g-\gd^4 b, g e> |
  <fis^4 b, a dis,>2 <g-\gsn #10 ##x2014 ^4 b, g e> |
  \set fingeringOrientations = #'(left)
  <fis-\gsn #-20 ##x2014 -4 b, a-2 dis,>2 <g-\gd^4 b, g-\gu^2 e> |
}