Re: Bar number moves down inexplicably

[David Wright]

On Mon 01 Feb 2016 at 08:04:17 (+0100), Michael Gerdau wrote:
> Hi David,
> 
> > > It also seems to move the bar number down. Does anybody know why?
> > 
> > I also have a bar number which moves down for some reason.
> > 
> > The attached snippet shows the problem. Commenting out the \layout
> > with % {  →  %{ fixes the bar number but I lose my fermatas (both
> > cases attached).
> 
> the following layout block works for me with LP 2.19.35:
> 
> %====================
> \layout {
>   \context {
>     \Score
>     \remove Mark_engraver
>     %\remove Staff_collecting_engraver
>   }
>   \context {
>     \Staff
>     \consists Mark_engraver
>     \consists Staff_collecting_engraver
>   }
> }
> %====================

As easy as that! Thanks. (I'm glad it _wasn't_ to do with
outside_002dstaff-objects.)

I copied the layout stanza from p221 of the Notation Manual (2.18.2)
without, as I said, really understanding it. The same stanza appears
in 2.19.34 (p234) and is the only mention of Staff_collecting_engraver
in the entire manual.

Seaching the Internals Manual (2.19.34) merely mystifies me. Its main
section (2.2.111 on p348) says the purpose of the
Staff_collecting_engraver is to "Maintain the stavesFound variable."

The only clue to using it is (quoting 2.2.67 Mark_engraver, but
repeated at various points in IM) "If moving this [Mark_]engraver to a
different context, Section 2.2.111 [Staff collecting engraver],
page 348 must move along, otherwise all marks end up on the same
Y location."

I parsed "move along" as meaning "move to that different context", not
"add another Staff_collecting_engraver at that different context".
The former seems to be what the NM author did, without realising
its side effect.

And sorry to confuse anyone who doesn't understand block comments.
I attached the snippet and wanted people to be able to duplicate
both the images with a minimum of editing (one space character).
See NM 3.1 Input structure.

Cheers,
David.