Re: RemoveEmptyStaffContext erases previous setting

[Mats Bengtsson]

Quoting Neil Thornock <address@hidden>:

> My understanding is that LilyPond can only take one \layout block -
> no?  So any subsequent layout block will override the previous one.

No! You can have several layout blocks and the accumulated result of
all settings is used.

> I don't think it's buggy at all.  You just need separate layout blocks
> for different components of your project.  I always have one for
> scores and a different one for parts.

Seems like a bad idea if large parts of the settings are the same for
both scores and parts.

The problem that Reinhold mentions is well-known and is documented in
http://lilypond.org/doc/v2.12/Documentation/user/lilypond/Changing-context-default-settings#Changing-context-default-settings

The simple solution is to change the order, so that you do \layout {
 \context { \RemoveEmptyStaffContext }
}

before any other

\layout {
 \context { \Staff
   ...
 }
}

To understand why this happens, you have to know that

\layout {
 \context { \Staff
  ...
means that the current settings for the Staff context are used as a
starting point and all following lines are additions to these settings.
When the closing } appears, the resulting list of settings is saved as
the new settings for the Staff context.

On the other hand, \RemoveEmptyStaffContext is a variable containing a
full list of settings, which replace the current list of settings for a
Staff context.

A pedagogical problem is that the syntax looks the same in both cases,
but what really happens is fundamentally different. Apart from the
warning in the manual, mentioned above, the only way to know if
\layout{
 \SomeName
 ...

will do one or the other, is to look in the file
.../ly/engraver-init.ly and see if \SomeName is defined as a variable
or if it's the name of a context.


Section 5.1 Interpretation Contexts, in the Notation Reference, will
hopefully provide enough details to understand what I just wrote.


If would be pedagogically simpler to realize this difference if the
syntax was separate if you define a context from scratch (as is the
case with \RemoveEmptyStaffContext) or if it's defined by adding onto
an existing context. For example, a syntax like

\context{
 % Copy the current settings of the Staff context:
 \use Staff
 % do whatever additional settings
}

could be used to distinguish from

\context{
 % Take settings from a variable:
 \Variable
 % do whatever additional settings
}

and

\context{
 % Start from scratch:
 \type ...
 \name ...
 \consists ...
 ...
}


 /Mats

> On Fri, Feb 5, 2010 at 8:14 AM, Reinhold Kainhofer
> <address@hidden> wrote:
> > I found out the hard way that apparently adding \RemoveEmptyStaffContext
> > globally to a score will erase some previous settings. In particular, if you
> > have:
> >
> > \layout {
> >  \context { \Staff
> >    ignoreFiguredBassRest = ##f
> >  }
> > }
> >
> > \layout {
> >  \context { \RemoveEmptyStaffContext }
> > }
> >
> > then the score will still use ignoreFiguredBassRest=##t (which is the
> > default). If you don't add the RemoveEmptyStaffContext, then ##f is used.
> >
> > Attached is an example file displaying this behavior.
> >
> > Is this a bug? In my eyes, it is quite severe, because it means you can't
> > trust  lilypond any more. If you check e.g. the individual parts
> > (which do not
> > add the RemoveEmptyStaffContext) for errors, you cannot be sure any
> > more that
> > the full score or e.g. the  choral score are correct, too!
> >
> > Cheers,
> > Reinhold
> >
> > PS: What is the reason anyway to have
> >  ignoreFiguredBassRest = ##t
> > for the Staff context? Bass figures on rests ARE used and have a
> > well-defined
> > meaning (namely that they take the next bass note as reference, but play the
> > harmony on the rest already). It seems that Han-Wen added this
> > feature a while
> > ago and set the default to ##t, but didn't really give any good reason to
> > silently discart bass figures on rests...
> > So, are there any reasons against making ##f the default (i.e. NOT silently
> > discarding vital bass figures)???
> >
> > --
> > ------------------------------------------------------------------
> > 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/
> >  * Edition Kainhofer Music Publishing, http://www.edition-kainhofer.com/
> >  * LilyPond music typesetting software, http://www.lilypond.org/
> >
> > _______________________________________________
> > lilypond-user mailing list
> > address@hidden
> > http://lists.gnu.org/mailman/listinfo/lilypond-user
>
>
>
> --
> Neil Thornock, D.M.
> Check out the newly designed website!
> http://neilthornock.net
> Assistant Professor of Music
> Composition/Theory
> Brigham Young University
>
>
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