Re: measures per system

[Kieren MacMillan]

Hi David,

> Attached you'll find a engraver which seems to work.

Thanks!

> and...
> if you didn't account for all the bars in the score, LilyPond should
> revert to normal line-breaking and pagination for the remaining
> measures.

Excellent!

> Shortcut--well, maybe not, but more user-friendly:
> The above \consist line may be written like so:
> \consists #(bars-per-line-systems-per-page '((4*2) (4*3) (1)))

Nice.

> Anyway, let me know if you run into problems with this

I'll be testing it heavily in the next day or so, and will report back.
So far (with a couple quick tests on my current big score), it seems amazing!

> or have suggestions for improvements.

First, a [incomplete] list of possible use cases, and notes (or questions) 
about their possible solution using the current pair of engravers:

Use Case #0: Let Lily determine all breaks.
Solution: don't use either of your engravers.  ;)

Use Case #1: Fix bars-per-system, but let Lily determine systems-per-page.
Solutions: use b-p-l engraver, or use b-p-l-s-p-p with '((4 5 4 2) (3 4 5) 
(4*6)), both with line-break-permissions = ##f and page-break-permission unset.

Use Case #2: Fix bars-per-page, but let Lily determine bars-per-line and 
systems-per-page.
Solution: use b-p-l-s-p-p with '((50) (20) (42)) and page-break-permissions = 
##f and line-break-permission unset.
[This, by the way, is very cool!]

Use Case #3: Fix bars-per-line and systems-per-page.
Solution: Use b-p-l-s-p-p engraver "fully" with line- and 
page-break-permissions = ##f.

Use Case #4: Let Lily determine bars-per-line, but fix systems-per-page.
Solution: ??

Can this last use case -- which is subtly but critically different from Use 
Case #2 -- be done with the current engravers? If not, I think there should be 
a systems-per-page engraver that could work independently of the bars-per-line 
engraver, so that one could say

\layout {
  \context {
    \Score
    \consists #(systems-per-page-engraver
    '(5 4 6 5 3 4)
  }
}

and not have to fuss with the bars-per-line breakdown within the systems. Does 
that make sense?

Thanks!
Kieren.