Re: centerPaperColumn

On Mon, Aug 31, 2015 at 7:58 AM, David Nalesnik <address@hidden> wrote:

Victor,

On Sun, Aug 30, 2015 at 8:12 PM, Víctor <address@hidden> wrote:

Dear David and lilyponders:

I'm glad to see that you are around here again, so now I hope it will be not much of a trouble if ask you to take a look to the aforementioned problem with the ties and centered notes. For those who don't know what I'm talking about, David Nalesnik programed a very useful function that centers notes when they occupy the whole measure. The problem seems to be that tie's length is not recalculated after the note column has been moved; and since my scheme-fu is very basic, I just can't fix this myself.

I'm sorry, but I don't know how to fix this.

The problem lies in the code for determining whether the PaperColumn to center or ignore is alone in the measure. This requires access to other columns in the line, and these are located through the grob-array 'columns. Unfortunately, this array is empty until line breaking has occurred. By then, it's too late to do anything about the ties, as far as I know. If there were a way to get the previous and adjoining columns before line breaking, that could possibly fix your problem. I don't see a way in Scheme, but I'd welcome being wrong about that.

And you might think 'left-neighbor and 'right-neighbor (http://lilypond.org/doc/v2.19/Documentation/internals/spaceable_002dgrob_002dinterface) would be exactly what we want. Works for an override of PaperColumn.after-line-breaking but we come up empty for 'before-line-breaking:

\version "2.19.25"

{

\override Score.PaperColumn.before-line-breaking =

#(lambda (grob)

(let ((left (ly:grob-object grob 'left-neighbor))

(right (ly:grob-object grob 'right-neighbor)))

(format #t "left neighbor: ~a right neighbor: ~a~%" left right)))

c'1

}

From:	Víctor
Subject:	Re: centerPaperColumn
Date:	Thu, 3 Sep 2015 19:59:21 -0500
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