Re: strange appoggiatura behaviour

[Reinhold Kainhofer]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Am Mittwoch, 27. August 2008 schrieb Daniel Hulme:
> On Wed, Aug 27, 2008 at 10:32:31PM +0200, Reinhold Kainhofer wrote:
> > Am Mittwoch, 27. August 2008 schrieb James E. Bailey:
> > > Oddly, in the attached code, if the appoggiatura is commented out,
> > > then the stems follow how they're supposed to. Is this a bug or a
> > > super-special feature of graceMusic that I just didn't know about?
> >
> > It seems that the grace note commands are yet another example of a
> > command that messes up ooiceOne/voiceTwo settings (by simply reverting
> > the stem direction instead of restoring the previous value). Other
> > examples I'm aware of are the cue commands.
>
> I'm glad someone has pointed this out, as it explains some previously
> mysterious behaviour. As I use Lilypond mostly for typesetting drum
> parts, pretty much every piece has grace notes and multiple voices.
>
> If someone who knows could point me towards the appropriate bit of code,
> it would give me great pleasure to cook up a patch and send to -devel.

Unfortunately it's not that simple to even understand where the problem 
happens. I looked at the internal music expression with and without the 
\voiceOne and there is no explicit stem direction change after the grace 
note. So it is not a problem of e.g. make-voice-props-revert, but rather a 
by-product of the processing!

I noticed that my initial assumption was wrong that the grace command reverts 
the stem direction. If you add any note or rest between the \voiceOne and the 
\appoggiatura, everything will work just fine. Apparently the stem change by 
\voiceOne is never recorded, because that seems to happen only on notes/rests 
and the first note after the \voiceOne is the grace note, which has its stem 
explicitly set to #UP. 
Thus, lilypond never realizes that the stem direction should be set to #UP for 
all notes.

Please note that other settings of \voiceOne are correctly applied (like the 
rest position)

I suppose this is a bug in Lilypond, which can be summarized as:
     "\voiceOne immediately before a grace command does not properly set 
      the stem direction". 

A minimal example is attached for the bug tracker. Can this be added as a bug 
if it's not already known?

Cheers,
Reinhold

- -- 
- ------------------------------------------------------------------
Reinhold Kainhofer, Vienna University of Technology, Austria
email: address@hidden, http://reinhold.kainhofer.com/
 * Financial and Actuarial Mathematics, TU Wien, http://www.fam.tuwien.ac.at/
 * K Desktop Environment, http://www.kde.org, KOrganizer maintainer
 * Chorvereinigung "Jung-Wien", http://www.jung-wien.at/
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQFIteWPTqjEwhXvPN0RAvwjAKCDFpPi3LuARhfPir+6PXrUIAzgCgCfXoMf
atEI+1xl91KwOmcpXiKYP9o=
=W1KV
-----END PGP SIGNATURE-----

grace_voiceOne_stemdirection.ly
Description: Text Data

grace_voiceOne_stemdirection.pdf
Description: Adobe PDF document