Pedal cautionary continuations and other bracket decorations

[Andrew Bernard]

For the Scheme gurus.

 

For a long time I have needed to decorate or embellish pedal brackets to customise them. Two things I need are arrows on the right hand side, and text markers similar to cautionary pedal indications on the left hand side, so each new broken bracket shows “1/2 ped” at the start, for example. I am aware that there have been discussions of similar things on the list, but it seems the only solutions were workarounds using text spanners. I have found this to be unsatisfactory, for my purposes. So I have developed Scheme code to achieve this effect. I am pleased to say I nearly have it working, but I am bedevilled by the fact that in this example the second line does not get decorated. I confess I am stumped. I wonder if anyone here can see what must be some silly error in the logic? I am not saying this is a bug. I am sure it is my dullness at work.

 

I apologise for this being a fairly complex bit of code to digest, but I have a feeling many people want this type of pedal customisation judging from the archived discussions, and I feel it may end up being a useful contribution, hence worth debugging.

 

One aspect that has me puzzled is that if you add more treble notes so that two staves are alive for longer the problem shifts around. I would have thought that pedal on the bottom staff would not be affected by a staff above, and this behaviour may be a clue to the issue, but I am unable to hear what it is telling me.

 

My thinking on this to date is that I remain very ignorant of when things are laid out and what order, if any, various internal constructions are done, so I am think this may be to do with the possibility that treating the broken spanner as an ordered list that is there ready to be modified may be a fundamental error. For what it’s  worth, therefore, I tried implementing this as an after line breaking callback, but the same problem shows.

 

Any help most appreciated.

 

Andrew

 

== snip

 

\version "2.19.50"

 

#(use-modules (srfi srfi-1))

 

#(define (make-arrow-path arrow-length arrowhead-height arrowhead-width)

   "Arrow with triangular arrowhead."

   (list

    'moveto 0 0

    'lineto arrow-length 0

    'lineto arrow-length (/ arrowhead-width 2)

    'lineto (+ arrow-length arrowhead-height) 0

    'lineto arrow-length (- (/ arrowhead-width 2))

    'lineto arrow-length 0

    'closepath

    ))

 

pedalWithArrowsAndText =

\once \override Score.PianoPedalBracket.stencil =

#(lambda (grob)

 

   ;; function to modify the individual grob part

   (define add-decorations

     (lambda (g list-length)

       (let* (

               ;; unpack the argument

               (index (car g))

               (grobber (cadr g))

               (last (= index list-length))

 

               ;; Get the default-stencil and its x-dimension and x-length.

               (stil (ly:piano-pedal-bracket::print grobber))

               (stil-x-extent (ly:stencil-extent stil X))

               (stil-x-length (interval-length stil-x-extent))

 

 

               ;; make arrow for the rhs end

               (thickness 0.1)

               (arrowhead-height 1.0)

               (arrowhead-width 1.0)

               (arrow-length 1.0)

               (arrow (make-path-stencil (make-arrow-path arrow-length arrowhead-height arrowhead-width) thickness 1 1 #t))

               (new-stil (if (not last)

                             (ly:stencil-combine-at-edge stil X RIGHT arrow -0.105)

                             stil))

 

 

               ;; make text for the lhs end

               (text-stil

                (grob-interpret-markup grobber

                  (markup

                  #:line

                   (#:abs-fontsize

                    6

                    (#:sans

                     (#:upright

                      (#:whiteout (#:box (#:pad-markup 0.3 "½ ped")))))))))

 

               (new-stil (ly:stencil-stack new-stil X LEFT text-stil -6)))

 

         (ly:grob-set-property! grobber 'stencil new-stil))))

 

   (let* (

           (stil (ly:piano-pedal-bracket::print grob))

           (orig (ly:grob-original grob))

           (pieces (if (ly:grob? orig)

                       (ly:spanner-broken-into orig)

                       '()))

           (pieces-indexed-list (zip (iota (length pieces) 1) pieces))

           (pieces-length (length pieces)))

 

     ;; We want arrows on all segments but the last, and text on all segments, so

     ;; we have to pass some notion of list index to the function doing the

     ;; decorating. Hence the ziplist combining grob segment and index in pairs.

 

     (let loop ((x 1)

                (count 0))

       (if (< count 5)

           (begin

            (add-decorations (list-ref pieces-indexed-list count) pieces-length)

            (loop x (+ count 1))

            )))

 

     stil))

 

%===========================================================================================

 

treble = {

  \clef treble

  \time 4/4

  c'4 c' c' c'

  c' c' c' c'

}

 

bass = {

  \clef bass

  \time 4/4

 

  c4

  \pedalWithArrowsAndText

  c\sustainOn c c

  c c c c

  \break

  c c c c

  \break

  c c c c

  \break

  c c c c

  \break

  c c c c\sustainOff

 

}

 

\score {

 

  \new PianoStaff

  <<

    \new Staff = "treble"  { \treble }

    \new Staff = "bass" { \bass }

  >>

 

  \layout {

    \context {

      \Score

      pedalSustainStyle = #'bracket

    }

  }

}

 

== snip