Re: Equal ends of glissandi

[Thomas Morley]

2017-09-30 11:46 GMT+02:00 Thomas Morley <address@hidden>:
> Hi all,
>
> consider the code below
>
> \score {
>   \relative c' {
>     <c e g b>4\glissando
>     <d' fis g bes>\glissando
>     <c, e g ais>
>   }
>   %% for better viewing:
>   \layout {
>     ragged-right = ##f
>     \override Glissando.color = #red
>     \override Glissando.thickness = 2.5
>   }
> }
>
> I want to create an override which should end all glissandi (starting
> at the NoteHeads of a certain NoteColumn) at the same X-coordinate
> left from all target-NoteHeads.
>
> I tried:
>
> #(define same-gliss-end
>   (lambda (grob)
>     (let* ((vertical-axis-group-elts
>              (ly:grob-object (ly:grob-parent grob Y) 'elements))
>            (all-gliss
>              (if (ly:grob-array? vertical-axis-group-elts)
>                  (filter
>                    (lambda (elt)
>                      (grob::has-interface elt 'glissando-interface))
>                    (ly:grob-array->list vertical-axis-group-elts))
>                  '()))
>            (gliss-X
>              (map
>                (lambda (gliss)
>                  (assoc-get 'X (ly:line-spanner::calc-right-bound-info 
> gliss)))
>                all-gliss))
>            (min-x (apply min gliss-X)))
>
>         (ly:grob-set-nested-property! grob '(right-bound-info X) min-x))))
>
> tst = \override Glissando.after-line-breaking = #same-gliss-end
>
> \score {
>   \relative c' {
>       \tst
>     <c e g b>4\glissando
>     <d' fis g bes>\glissando
>     <c, e g ais>
>   }
>   %% for better viewing:
>   \layout {
>     ragged-right = ##f
>     \override Glissando.color = #red
>     \override Glissando.thickness = 2.5
>   }
> }
>
> Which indeed does the job for the first group of glissandi.
> But all other vanish, because I take the glissandi from
> VertivalAxisGroup. Meaning the last call of the override points
> _every_ glissando to the same X-value, which is the minimum-X of _all_
> glissandi of the current system.
>
> Do I overlook something simple?
> If not, how to do it different?
>
> Any hint appreciated!
>
>
> Thanks,
>   Harm

Eventually I've found a method to limit the affected glissandi to
those of the same NoteColumn.
Though, do we really have no direct method to get all glissandi from
every note of an event-chord? As far as I understand 'glissando-index
and glissandoMap are of no help with this.

Anyway, here what I did:

\version "2.19.65"

#(define same-gliss-start-end
  ;; All glissandi between chords should start at the same X-coordinate, same
  ;; for glissando-endings.
  (lambda (grob)
    (let* ((left-bound (ly:spanner-bound grob LEFT))
           (parent-nc (ly:grob-parent left-bound X))
           (vertical-axis-group-elts
             (ly:grob-object (ly:grob-parent grob Y) 'elements))
           ;; Filter VerticalAxisGroup-elements for Glissandi, restricted to
           ;; those starting at the NoteHeads from same NoteColumn.
           ;; Return their 'X-value for start/end
           (relevant-gliss-Xs
             (if (ly:grob-array? vertical-axis-group-elts)
                 (filter-map
                   (lambda (elt)
                     (and
                       (grob::has-interface elt 'glissando-interface)
                       (equal?
                         (ly:grob-parent (ly:spanner-bound elt LEFT) X)
                         parent-nc)
                       (cons
                         (assoc-get 'X
                                    (ly:grob-property elt 'left-bound-info))
                         (assoc-get 'X
                                    (ly:grob-property elt 'right-bound-info)))))
                   (ly:grob-array->list vertical-axis-group-elts))
                 '()))
           ;; Get the most left 'X for the final 'X-value of the end.
           ;; Get the most right 'X for the final 'X-value of the start.
           ;; Override left/right-bound-info with those values.
           (min-x-right (apply min (map cdr relevant-gliss-Xs)))
           (max-x-left (apply max (map car relevant-gliss-Xs))))
      (ly:grob-set-nested-property! grob '(left-bound-info X) max-x-left)
      (ly:grob-set-nested-property! grob '(right-bound-info X) min-x-right))))

\score {
  \relative c' {
      \override Glissando.after-line-breaking = #same-gliss-start-end
    <c e g b>1\glissando
    <d' fis g bes>\glissando
    \break
    %% \grace is used only to show behaviour of broken glissandi
    \grace s16
    <c, e g ais>1
  }
  %% for better viewing:
  \layout {
    ragged-right = ##f
    \override Glissando.color = #red
    \override Glissando.thickness = 2.5
    \override Glissando.breakable = ##t
    %% further customizing possible with tweaks/overrides like:
    %\override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
    %\override Glissando.minimum-length = 8
    \override Glissando.bound-details.left.padding = #1
    %\override Glissando.bound-details.right.padding = #3
  }
}

@David N
Attached you'll find the full coded feature. I.e. a method to indicate
equal notes in the same chord-voice of a chord-progression.
It's meant for educational purpose.
Maybe a usefull addition to your partwriter, although I didn't test
whether both codings are compatible.

Cheers,
  Harm

glissando-indicates-equals-01.pdf
Description: Adobe PDF document

glissando-indicates-equals.ly
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