Re: "Collect" barnumbers for line and page breaks

[David Nalesnik]

Hi Urs,

On Sat, Jan 10, 2015 at 8:44 AM, Urs Liska <address@hidden> wrote:

Hi list,

is it possible to collect the measure/measure-position values of all breaks in a compilation and output that to a logfile?

Yes, it is possible.  As far as I can tell, though, an engraver only has access to explicit line- and page-breaks.  I could be wrong, and I hope I am!

The following engraver will write line- and page-break info to the file "output.txt" in the format (measure . measure-position).  Nothing will be output for files that don't contain \break or \pageBreak.

 \version "2.19.15"

writeBreaksEngraver =

#(lambda (context)

   (let ((out (open-output-file "output.txt")))

     (make-engraver

      (listeners

       ((line-break-event engraver event)

        (let* ((ccc (ly:context-property context 'currentCommandColumn))

               (m (ly:context-property context 'currentBarNumber))

               (mpos (ly:context-property context 'measurePosition))

               (loc (cons m mpos))) 

          (format out "Line break at ~a~%" loc))) 

       ((page-break-event engraver event)

        (let* ((ccc (ly:context-property context 'currentCommandColumn))

               (m (ly:context-property context 'currentBarNumber))

               (mpos (ly:context-property context 'measurePosition))

               (loc (cons m mpos)))

          (format out "Page break at ~a~%" loc))))

      ((finalize trans)

       (close-output-port out)))))

{

  c'1

  \break

  c'1

  \break

  c'1

  \pageBreak

  c'1

  \break

}

\layout {

  \context {

    \Score

    \consists \writeBreaksEngraver

  }

}

As mentioned yesterday I found a way to ask LilyPond to compile only a portion of a score by passing a range of measures.
And if I had a generated list of all current breaks I could ask LilyPond to recompile just the staff (or page) I'm currently working on.
Eventually this could be extended with the help of outputting single files for systems (à la lilypond-book-preamble). I think of having Frescobaldi display not a usual engraved PDF but concatenate these individual system images. Then the autocompile function could be used to only autocompile the "current" system - which would be a huge improvement in terms of responsiveness.

As mentioned in my post a few minutes ago I haven't understood yet how engravers, listeners and friends actually work so I'd need some starters to get me going.

TIA
Urs

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