Re: missing glissando features (bugs?)

[Marc Hohl]

Neil Puttock schrieb:
> 2009/5/9 Marc Hohl <address@hidden>:
>
>   
> > I tried to receive the informations needed by overriding the Glissando
> > #'stencil with
> > a function which simply displays the values obtained by the ly:spanner-bound
> > call
> > before calling ly:line-spanner::print, but I get only  #<Grob NoteHead > on
> > the terminal.
> >
> > What am I doing wrong here?
> >     
>
> Nothing, though to be on the safe side, it's best to ensure you're
> dealing with the unbroken spanner by using ly:grob-original: if a user
> decides to have a glissando over a line break, it won't be possible to
> get noteheads for both bounds.
>
> Once you have the NoteHead grobs, you can retrieve their pitches from
> the events which created them:
Neil, thank you, I wasn't aware of this connection between grobs and events.
Now it seems rather logical (not surprising as we talk about computing 
languages :-)

> \relative c' {
>   \override NoteHead #'stencil = #(lambda (grob)
>      ;; event-cause is a convenient shorthand in this case for
> (ly:grob-property grob 'cause)
>      (display (event-cause grob))
>      (ly:note-head::print grob))
>      c4
> }
>
>   
>
> #<Prob: Stream_event C++: Stream_event((music-cause . #<Prob: Music
> C++: Music((length . #<Mom 1/4>) (elements) (duration . #<Duration 4
>   
> > ) (pitch . #<Pitch c' >) (origin . #<location
> >     
> /home/neil/Documents/test.ly:254:5>))((display-methods #<procedure #f
> (note parser)>) (name . NoteEvent) (types general-music event
> note-event rhythmic-event melodic-event)) >
> ) (length . #<Mom 1/4>) (elements) (duration . #<Duration 4 >) (pitch
> . #<Pitch c' >) (origin . #<location
> /home/neil/Documents/test.ly:254:5>))((class . note-event)) >
>
> >From the event, you can get the pitch using ly:event-property event 'pitch.
>
> Putting it all together:
>
> #(define (glissando::calc-extra-dy grob)
>    (let* ((original (ly:grob-original grob))
>           (left-bound (ly:spanner-bound original LEFT))
>           (right-bound (ly:spanner-bound original RIGHT))
>           (left-pitch (ly:event-property (event-cause left-bound) 'pitch))
>           (right-pitch (ly:event-property (event-cause right-bound) 'pitch)))
>
>      ;; work out return value based on pitches here
>
>   
I came up with the following definition:

#(define (glissando::calc-extra-dy grob)
  (let* ((original (ly:grob-original grob))
         (left-bound (ly:spanner-bound original LEFT))
         (right-bound (ly:spanner-bound original RIGHT))
         (left-pitch (ly:event-property (event-cause left-bound) 'pitch))
         (right-pitch (ly:event-property (event-cause right-bound) 'pitch))
         (extra-dy
             (if (and (= (ly:pitch-octave left-pitch) (ly:pitch-octave 
right-pitch))
                      (= (ly:pitch-notename left-pitch) 
(ly:pitch-notename right-pitch)))
                 (- (ly:pitch-alteration right-pitch) 
(ly:pitch-alteration left-pitch))
                 0 )))
         (set! (ly:grob-property grob 'extra-dy) extra-dy)
         (ly:line-spanner::print grob)))

noten = \relative c {
  c4 \glissando cis
  c4 \glissando cis
  c4 \glissando ces
  c4 \glissando ces
  c4 \glissando d \glissando e \glissando f
}


\score {
  <<
     \new Staff { \clef "G_8"
                  \noten \break
                  \override Glissando #'stencil = #glissando::calc-extra-dy
                  \noten}
  >>
}

and it works! Lilypond is just great; the deeper I get into it, the more 
impressed I am.
So I will try and solve the tablature problem, too.

Marc

>      0))
>
> Regards,
> Neil
>
>