Re: override stencil question

[Rama Gottfried]

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?

Thanks for your help,
Rama



Here is the current working version:


\version "2.17.13"

arc = #(list 0 0) %<< global variable to bezier curve handle
glissWidth = #0.2 %<< global variable for glissando width

#(define (set-arc x y)
        (set! arc (list x y)))

#(define (get-arc)
        arc)

#(define (path-gliss 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))
                        (handle (get-arc))) ;<<------------- getting the handle 
value here              
                                
       (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.)))
        \override Glissando #'stencil = #path-gliss
} 
\relative b' {
        \addGliss { 
                #(set-arc 2 4)
                c8 
                #(set-arc 3 -4)
                d 
                %only the final value of arc is used for the stencil callback
                #(set-arc 2 4)
                a 
                b }     
                f 
         \addGliss{ 
                d'16 
                a 
                c2 } 
                b32
}