Hi, In the attached snippet, the call to ly:set-default-scale has no effect on the midi result, both in the stable and development versions.
I believe that this is due to Pitches being constructed before
the new default_global_scale is set (see files lily/pitch.cc and
lily/scale.cc), so that they keep a pointer to the old Scale,
created in scm/lily.scm:387.
This looks bad, because as ly:set-default-scale is called, the
old object gets unprotected.
In fact, by applying the change described in the attached file
diff.txt, I obtained the results I expected (set-scale-test-mine.midi),
which only confirms my suspicions. (The last c is 6 tones higher,
because an octave is hard-coded as 6 tones, but that is another
issue).
This leads me to the following questions:
1. Is the current behaviour the desired one?
2. Is it a bug?
3. Do we really have a problem with garbage collection?
(I observe no consequences)
By the way, there is actually an alternative solution, which would be
to make Pitch objects use default_global_scale directly, instead of
storing its value as an internal field during initialisation. This leads
me to the related question:
4. What is the purpose of the non-static scale_ field in the Pitch class?
I look forward to and would very much appreciate any thoughts on
these from anybody acquainted with this code.
Kind regards,
Felipe
diff --git a/lily/scale.cc b/lily/scale.cc
index e3fe7ba..a14d8b3 100644
--- a/lily/scale.cc
+++ b/lily/scale.cc
@@ -89,9 +89,11 @@ LY_DEFINE (ly_set_default_scale, "ly:set-default-scale",
Scale *s = Scale::unsmob (scale);
if (default_global_scale)
- default_global_scale->unprotect ();
- default_global_scale = s;
- s->protect ();
+ *default_global_scale = *s;
+ else {
+ default_global_scale = s;
+ s->protect ();
+ }
return SCM_UNSPECIFIED;
}
\version "2.12.1"
#(ly:set-default-scale (ly:make-scale '#(0 0 0 0 0 0 0)))
m = \relative c' { c d e f g a b c}
\score {
\m
\midi { }
}
set-scale-test-mine.midi
Description: MIDI audio
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