Re: "natural width" of a measure

[David Nalesnik]

On Tue, Apr 11, 2017 at 1:52 PM, Urs Liska <address@hidden> wrote:
>
>
> Am 11.04.2017 um 20:46 schrieb Malte Meyn:
>>
>> Am 11.04.2017 um 20:36 schrieb Urs Liska:
>>> So, is there any moment in the compilation process where the natural,
>>> unstretched length of a measure can be calculated? It doesn't have to be
>>> an easily-read property and can involve calculation, but actually the x
>>> position of the barlines would be an easy target - *if* there's this
>>> magic moment in the compilation pipeline ;-)
>> Maybe you could experiment with the ly:one-line-breaking?
>
> I don't think so (only, of course, to investigate how much can be done
> on the internal level).
> Basically what I'm after is a ly:cheap-line-breaking mode that doesn't
> care at all about overall appearance or good page turns but instead
> simply places as many measures in a line as fit naturally. If then a
> line break changes and I know the natural width of the measures I can
> determine before compilation how many measures will fit on the *next*
> system.
>

But spacing depends on the sorts of durations present -- the most
common duration, the shortest duration.

Do you mean to typeset each measure as if it's in isolation, without
stretching based on surrounding measures?

For example,

\version "2.19.59"

\layout { ragged-right = ##t }

{
  \repeat unfold 16 { c''16 }
  \repeat unfold 4 { c''4 }
  c''1
  c''2 c''2
  \repeat unfold 64 { c''64 }
}

\layout {
  \context {
    \Score
    \override SpacingSpanner.common-shortest-duration = #'()
  }
}

%%

Alternately, you could create a \newSpacingSection every measure,
though this gives different values.  Don't know why.

%%%%%%%%%%%%%%%%%%%%%%%%

Here's how you can determine the widths of measures.  Note that I've
put everything on one line, so that the \once \override of the
NoteHead gives access to every column in the score.  You can adjust
what alignment objects are used to gauge width by changing the symbol
in ly:paper-column::break-align-width (available as of 2.19.59).
Right now, it's BreakAlignment objects to give you an extent
considering all prefatory materials.  staff-bar would give extents of
the bar lines.

\version "2.19.59"

\paper {
  page-breaking = #ly:one-line-breaking
}

#(define (display-measure-widths grob)
   (let* ((sys (ly:grob-system grob))
          (cols (ly:grob-array->list (ly:grob-object sys 'columns)))
          (nmpcs
           (filter
            (lambda (elt)
              (and (grob::has-interface elt 'paper-column-interface)
                   (eq? #t (ly:grob-property elt 'non-musical))))
            cols))
          (widths
           (map
            (lambda (c) (ly:paper-column::break-align-width c
'(break-alignment)))
            nmpcs))
          (widths (sort widths (lambda (x y) (< (car x) (car y)))))
          )
     (pretty-print widths)))
{

  \once \override NoteHead.after-line-breaking = #display-measure-widths
  \repeat unfold 4 { c''8. c''16}
  \repeat unfold 4 { c''4 }
  c''1
  c''2 c''2
  \repeat unfold 64 { c''64 }
}

\layout {
  \context {
    \Score
    \override SpacingSpanner.common-shortest-duration = #'()
  }
}

Hope this helps with something!

David