Re: question about overrides within repeats

[David Nalesnik]

Hi,

On Sun, Nov 22, 2015 at 3:00 PM, David Kastrup <address@hidden> wrote:

Simon Albrecht <address@hidden> writes:

> On 22.11.2015 21:44, David Kastrup wrote:
>> Thomas Morley <address@hidden> writes:
>>
>>> Though, why it is that arbitrary?
>>>
>>> Look at this variation and the attached image:
>>>
>>> \version "2.19.29"
>>> #(define test-nmbrs
>>>    (let ((nmbrs (circular-list 1 2 3 4)))
>>>      (lambda (grob)
>>>        (let ((n (car nmbrs)))
>>>          (set! nmbrs (cdr nmbrs))
>>>          (grob-interpret-markup grob (number->string n))))))
>>>
>>> {
>>>    \repeat unfold 8 {
>>>      \once \override TextScript.stencil = #test-nmbrs
>>>      c''4^\markup "foo"
>>>    }
>>> }
>> Well, it is exactly 2 variants of 1, 2, 3, 4 each.  I suspect that the
>> order of grob evaluation at some point when a system is printed depends
>> on the order of memory addresses.
>>
>> Find that point and you'll likely also have the culprit for various
>> other stuff behaving non-deterministically, like what is drawn on top of
>> what and other things frequently turning up in "make check".
>>

I don't know if this has anything to do with it,  but the grob-array 'all-elements doesn't appear to be consistently sorted by moment.

The following function gives each TextScript grobs on a line a number based on its position within the 'all-elements array.  Each line should be numbered 1-20 in order, but that's clearly not the case.  There's a binding of texts which sorts grobs by moment.  Comment that back in and the problem disappears.

\version "2.19.30"

#(define (number-me grob)

   (let* ((sys (ly:grob-system grob))

          (all-grobs (ly:grob-array->list (ly:grob-object sys 'all-elements)))

          (texts (filter (lambda (elt) (grob::has-interface elt 'text-script-interface))

                         all-grobs))

          ;(texts (sort texts (lambda (x y) (ly:moment<? (grob::when x) (grob::when y)))))

          )

     (let loop ((t texts) (idx 1))

       (if (not (null? t))

           (begin

            (set! (ly:grob-property (car t) 'stencil)

                  (grob-interpret-markup (car t) (number->string idx)))

            (loop (cdr t) (1+ idx)))))))

{

  \repeat unfold 10 {

    \once\override NoteHead.after-line-breaking = #number-me

    \repeat unfold 20 c''4^"foo"

    \break

  }

}