Re: test spanner with controlled gradient / dynamic volume curve indicated by grey level

[Michael Winter]

Another option for the line breading is to give the target final note 
for a system, hide it (basically the last note in your example). then in 
the next system. do the same with the starting note on the left side and 
hide it. Kind of a hack, but could actually look nice because you would 
see the full extent of the gradient on both the end of one system and 
the beginning of the next. See below a quick mockup.

I am now curious what you are thinking about the line breaking. Maybe I 
am out to lunch here and you have a much better idea. I will wait to 
hear from you before I do any heavy lifting.

Best,

Michael

--------------------------

\version "2.18"

\paper { ragged-right = ##f }

\layout {
  \context {
      \Staff
      \override StaffSymbol.line-count = #1
      \remove "Clef_engraver"
      \remove "Time_signature_engraver"
  }
  \context {
      \Voice
      \override Glissando.minimum-length = #0
      %% n.b. line-breaks are TODO
      \override Glissando.breakable = ##t
      \override Glissando.after-line-breaking = ##t
      \override Glissando.bound-details =
        #'((right
             (attach-dir . 0)
             (end-on-accidental . #f)
             (padding . 0.))
           (left
             (attach-dir . 0)
             (padding . 0.)))
    }
}

#(define (make-grey-filled-box-stencil-list x-coords color-steps 
half-thick rl)
  (if (null? (cdr x-coords))
      rl
      (make-grey-filled-box-stencil-list
        (cdr x-coords)
        (cdr color-steps)
        half-thick
        (cons
          (stencil-with-color
            (make-filled-box-stencil
              (interval-widen (cons (car x-coords) (cadr x-coords)) 0.1)
              (cons (- half-thick) half-thick))
            (x11-color
              (string->symbol (format #f "grey~a" (car color-steps)))))
          rl))))

#(define my-gliss
  (lambda (grob)
    (if (ly:stencil? (ly:line-spanner::print grob))
        (let* ((stencil (ly:line-spanner::print grob))
               (X-ext (ly:stencil-extent stencil X))
               (left-bound-info (ly:grob-property grob 'left-bound-info))
               (left-Y (assoc-get 'Y left-bound-info))
               (left-X (interval-start X-ext))
               (right-bound-info (ly:grob-property grob 'right-bound-info))
               (right-X (interval-length X-ext))
               (thick (ly:grob-property grob 'thickness 0.5))
               (delta-X (- right-X left-X))
               (steps
                 (assoc-get 'color-steps (ly:grob-property grob 
'details) 100))
               (raw-color-steps
                 (iota (abs steps) 0 (round (/ 100 (min 100 (abs 
steps))))))
               (color-steps
                 (if (negative? steps)
                     (reverse raw-color-steps)
                     raw-color-steps))
               (x-coords (iota (1+ (abs steps)) 0 (/ delta-X (abs 
steps)))))

          ;; create a flat glissando
          (ly:grob-set-nested-property! grob '(right-bound-info Y) left-Y)

          ;; return the stencil of added boxes
          (ly:stencil-translate-axis
            (apply
              ly:stencil-add
              (make-grey-filled-box-stencil-list
                x-coords
                color-steps
                thick
                '()))
            ;; the actual offset is TODO, hardcoded here
            -8
            Y))
         #f)))

#(define (add-gliss m)
   (case (ly:music-property m 'name)
     ((NoteEvent)
      (set! (ly:music-property m 'articulations)
            (append
              (ly:music-property m 'articulations)
              (list (make-music 'GlissandoEvent))))
      m)
     (else #f)))

addGliss =
#(define-music-function (parser location music)
  (ly:music?)
  (map-some-music add-gliss music))

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

mus =
  {
    \addGliss {
      \override Glissando.stencil = #my-gliss
      b'16 b'16 b'8 b'4
      \override Staff.Beam.color = #(x11-color 'grey60)
      b'8 b'16 b'16 ~
    }
    %% n.b. If glissando-skip is #t \addGliss needs to be interrupted
    %% otherwise a programming error occurs
    \once \override NoteColumn.glissando-skip = ##t
    b'16
    \addGliss {
      b'16 b'8
    }
    %% a final target for the last glissando needs to be present, otherwise
    %% lily complains about unterminated glissando
    \time 1/8  \stopStaff \hide Stem \hide b'8 \break

    \addGliss {
      \override Glissando.stencil = #my-gliss
      \hide Stem \hide b'8 \startStaff \time 4/4
      b'16 b'16 b'8 b'4
      \override Staff.Beam.color = #(x11-color 'grey60)
      b'8 b'16 b'16 ~
    }
    %% n.b. If glissando-skip is #t \addGliss needs to be interrupted
    %% otherwise a programming error occurs
    \once \override NoteColumn.glissando-skip = ##t
    b'16
    \addGliss {
      b'16 b'8
    }
    %% a final target for the last glissando needs to be present, otherwise
    %% lily complains about unterminated glissando
    \time 1/8  \stopStaff \hide Stem \hide b'8 \break

    \addGliss {
      \override Glissando.stencil = #my-gliss
      \hide Stem \hide b'8 \startStaff \time 4/4
      b'16 b'16 b'8 b'4
      \override Staff.Beam.color = #(x11-color 'grey60)
      b'8 b'16 b'16 ~
    }
    %% n.b. If glissando-skip is #t \addGliss needs to be interrupted
    %% otherwise a programming error occurs
    \once \override NoteColumn.glissando-skip = ##t
    b'16
    \addGliss {
      b'16 b'8
    }
    %% a final target for the last glissando needs to be present, otherwise
    %% lily complains about unterminated glissando
    \time 1/8 \stopStaff \hide Stem \hide b'8 \break
  }

\new Staff \mus






On 01/31/2018 11:37 AM, Michael Winter wrote:
> Hmmm... I made the change to use the stencil extent and that seems to 
> be fine. I am not sure what you are saying about the visibility of the 
> final stencil.
>
> As for linebreaking. That is indeed a showstopper at the moment. Is 
> that because you are using filled box stencil? When I was using a path 
> directive with a line, the breaking seemed to work / break fine. I 
> will see if I can make the switch unless you have another idea.
>
> Best,
>
> Michael
>
>
> On 01/31/2018 03:41 AM, Thomas Morley wrote:
> > 2018-01-31 3:46 GMT+01:00 Michael Winter <address@hidden>:
> > > On first glance. This looks ideal. THANK YOU
> > >
> > > I am a bit brain dead at the moment, so will dig in tomorrow and let 
> > > you
> > > know if I have any further questions / thoughts / ideas.
> >
> > Glad you like it.
> > I've found a weakness, though: the stencils overlap. Visible, if you
> > apply box-stencil to the final stencil.
> > Probably one should go for stencil-extent to get the extension in
> > X-axis and not for 'X from left/right-bound-info.
> > Will have a look in the evening.
> > Also, linebreaks are not yet working.
> >
> > Cheers,
> >    Harm