Re: More about stencil

[Aaron Hill]

On 2022-02-13 11:43 am, Rip _Mus wrote:
> Hello everyone,
> thanks to your many suggestions, I was able to get a little into the
> perspective of modifying the stencils.
> I created a stencil modification that adds a small arrow (sort of a
> glissando) to the left of the note or accident.
> However, I cannot understand why the ascending arrows let the stem no
> longer attached to the notehead. Do you have any ideas?

Modifying the NoteHead stencil as you are doing changes its extents, 
thus affects the attachment point.  One option is to add the arrow to 
the final stencil but preserve the original extents:

%%%%
  (ly:stencil-outline
    (ly:stencil-combine-at-edge arr X RIGHT note 0)
    note)
%%%%

(The above approach might result in collisions.)

Another option would be to utilize Fingering as a host grob, as that 
already handles alignment with notes whether or not accidentals are 
present:

(Below also I show an alternate method for defining the arrows, so that 
a shared symbol is simply rotated.  Custom extents are specified so that 
the arrows align as desired.)

%%%%
double-right-arrow =
#(ly:stencil-add
  (make-line-stencil 0.1 -0.9 0.1 -0.1 0.1)
  (make-line-stencil 0.1 -0.9 -0.1 -0.1 -0.1)
  (make-line-stencil 0.15 -0.3 0.3 0 0)
  (make-line-stencil 0.15 -0.3 -0.3 0 0))

glis-su-arrow =
#(ly:make-stencil
  (ly:stencil-expr
   (ly:stencil-rotate double-right-arrow 45 RIGHT CENTER))
  '(-0.7 . -0.2) '(-0.3 . 0.7))

glis-giu-arrow =
#(ly:make-stencil
  (ly:stencil-expr
   (ly:stencil-rotate double-right-arrow -45 RIGHT CENTER))
  '(-0.7 . -0.2) '(-0.7 . 0.3))

glis-giu =
#(define-music-function
  (note) (ly:music?)
  (ly:music-set-property! note 'articulations
   (cons
    (make-music 'FingeringEvent 'digit 1
     'tweaks (list (cons (quote stencil) glis-giu-arrow)))
    (ly:music-property note 'articulations '())))
  #{ \once \set fingeringOrientations = #'(left)
     #(make-event-chord (list note)) #})

glis-su =
#(define-music-function
  (note) (ly:music?)
  (ly:music-set-property! note 'articulations
   (cons
    (make-music 'FingeringEvent 'digit 1
     'tweaks (list (cons (quote stencil) glis-su-arrow)))
    (ly:music-property note 'articulations '())))
  #{ \once \set fingeringOrientations = #'(left)
     #(make-event-chord (list note)) #})

\new Staff {
  \relative c' {
    \once \override Score.FootnoteItem.annotation-line = ##f
    \footnote "*" #'(-0.2 . -1) "* glissando at the end of previous 
note" NoteHead
    \stemDown \glis-giu f2 \glis-su b |
    \glis-giu fis4 \glis-su bes2.
    \glis-giu c32 \glis-su c c c c c c c
    \glis-giu c \stemUp \glis-giu c
  }
}
%%%%

Since Fingerings must be inside a chord (i.e. <>) construct in order to 
respect fingeringOrientations, the music functions above have to do some 
manipulation of the argument.  Depending on how you intend on using 
these arrows in context, it might be worth the time to invent a custom 
grob instead rather than cannibalize something built-in.


-- Aaron Hill