Re: override stencil question

[Rama Gottfried]

Thanks David -- This is great, I can almost start with the score now.

I was (am still a bit) unclear about how the grob gets passed to the callback function.

interesting that the grob is still available within the callback without passing it -- I had thought that the stencil assignment was passing the grob to the callback function with the first argument.  But now if I understand correctly, I think the stencil callback function is called within the grob parent, and automatically has access to the grob?

Rama

On Mar 10, 2013, at 8:50 PM, David Nalesnik wrote:

Hi Rama,

On Sun, Mar 10, 2013 at 8:33 PM, Rama Gottfried <address@hidden> wrote:

Hi guys,

I'm making progress, but now am stuck and wondering if you have any advice or see anything I'm doing wrong here (code below).

What I would like to be able to do is specify the handle coordinates for the curve for each glissando.
The problem I'm having is that it seems that all glissandos are using the last value for the arc.

To try to fix the problem I added a call within the stencil callback function to get the current value of arc, but this isn't working.

Any ideas?

The problem here is the use of a top-level variable for the handle coordinates.  You could fix this by adding an argument to your stencil function.  I just took a quick look, but I think this will get you on the right track:

\version "2.17.13"

glissWidth = #0.2 %<< global variable for glissando width

#(define (path-gliss handle)

  (lambda (grob)

    (if (ly:stencil? (ly:line-spanner::print grob))

(let* ((stencil (ly:line-spanner::print grob))

      (X-ext (ly:stencil-extent stencil X))

      (Y-ext (ly:stencil-extent stencil Y))

      (width (interval-length X-ext))

      (height (interval-length Y-ext))

      (lefty (cdr (assoc 'Y (ly:grob-property grob 'left-bound-info))))

      (righty (cdr (assoc 'Y (ly:grob-property grob 'right-bound-info))))

      (deltay (- righty lefty))

      (dir (if (> deltay 0) 1 -1)))

  (ly:stencil-translate

    (grob-interpret-markup grob

      (markup

    ;(#: tiny (format "~a" (ly:grob-properties grob)))

    ;(format "~a" (cdr (assoc 'Y (ly:grob-property grob 'left-bound-info))))

    ;(#: tiny (format "~a" handle))

(#:path glissWidth

  (list (list 'moveto 0 0)

(list 'curveto 0 0 (first handle) (second handle) width (* height dir))))))

    (if (> dir 0)

   (cons (interval-start X-ext) (+ (interval-start Y-ext) 0.1))

   (cons (interval-start X-ext) (+ (interval-start Y-ext) height)))))

 #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 (quote GlissandoEvent)))))

                   m)

     (else #f)))

addGliss = #(define-music-function (parser location music)

                 (ly:music?)

           (map-some-music add-gliss music))

\new Staff \with {

        \remove "Time_signature_engraver"

        \remove "Clef_engraver"

        \omit Staff.BarLine

         \override SpacingSpanner

                #'base-shortest-duration = #(ly:make-moment 1 32)

        \override StaffSymbol #'line-count = #1

        \override Stem #'direction = #UP

        \override NoteHead #'transparent = ##t

        \override NoteHead #'no-ledgers = ##t

        \override NoteHead #'stem-attachment = #'(0 . 0)

        \override Glissando #'bound-details = #'((right (attach-dir . 0) (end-on-accidental . #f) (padding . 0.)) (left (attach-dir . 0) (padding . 0.)))

}

\relative b' {

        \addGliss {

                \once \override Glissando #'stencil = #(path-gliss '(2 4))

                c8

                \once \override Glissando #'stencil = #(path-gliss '(3 -4))

                d

               \once \override Glissando #'stencil = #(path-gliss '(2 4))

                a

                b }

                f

         \addGliss{

                d'16

                a

                c2 }

                b32

}

HTH,

David