I use debug print statements when developing scheme music functions. I
have this evening noticed for the first time that my complete
perplexity regarding various properties may actually come from the
following problem. When I run a function several times in a row, the
print output comes out in backwards order to the score note order. [No
wonder I have been confused.] The MWE here shows this.
Have I fundamentally misunderstood the essence of lilypond? Is the
engraving laid out backwards? Is there something intrinsically
non-linear about the engraving engine that means that the way I debug
and develop is in principle disallowed? I ask in all seriousness.
Otherwise, how to explain the results of the MWE?
[The function is purposely cut down so as to be a MWE, and
consequently is only a toy that does nothing but print the property of
interest to me, by way of explanation.]
Andrew
== snip
\version "2.19.45"
slashDbg =
#(define-music-function (ang stem-fraction protrusion)
(number? number? number?)
#{
\once \override Stem #'stencil =
#(lambda (grob)
(let* (
(beam (ly:grob-object grob 'beam))
(beam-X-pos (ly:grob-property beam 'X-positions))
(beam-Y-pos (ly:grob-property beam 'positions))
(stil (ly:stem::print grob)))
(display beam-Y-pos) (newline)
stil))
#})
{
\voiceOne
\once \override Beam.positions = #'(6 . 9)
\slashDbg 50 0.8 0.7
b''8 [ b' b' c' c'] s8
\slashDbg 50 0.8 0.7
d''8[ b' b' c' c'''] s8
\once \override Beam.positions = #'(8 . 5)
\slashDbg 50 0.8 0.7
d''8[ b' b' c' c''] s8
}
== snip
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