Re: Anybody has a good explanation for _this_ use of grob-transformer?

[Thomas Morley]

2018-01-28 18:07 GMT+01:00 David Kastrup <address@hidden>:
>
> The result is that all the beams are smashed up in the left border and
> the tuplet numbers appear over the respective first notes.  All of which
> seems like a seriously messed up X offset rather than the Y offset that
> should not even have been changed.

Hi David,

I never got to grips with that unpure-pure stuff.
>From IR:
Function: ly:make-unpure-pure-container unpure pure
Make an unpure-pure container. unpure should be an unpure expression,
and pure should be a pure expression. If pure is omitted, the value of
unpure will be used twice, except that a callback is given two extra
arguments that are ignored for the sake of pure calculations.

I mean, really?
In german I'd say: Verarschen kann ich mich alleine...

Granted, we have more verbose explanations in the docs (NR and CG),
though I never really figured what's it all about ...

That said, I played around a little.
No clue if it helps you in any way but eliminated grob-tranformer and
tried three different codings.
The last succeeds, though I've no clue why and no clue why the others fail.
I also made the TupletBracket always visible, messed up as well for
the failing codings.

\version "2.21.0"

\relative c' {
  \voiceOne
  \override TupletBracket.bracket-visibility = ##t

  %% fail
  \override TupletNumber.Y-offset =
   #(ly:make-unpure-pure-container
      (lambda (grob) (+ (ly:tuplet-number::calc-y-offset grob) 1))
      (lambda (grob start end) (ly:tuplet-number::calc-y-offset grob)))

  \tuplet 3/2 4 {
    c8 d e f g a b c d e f g
    c,,8^> d e f^> g a b^> c d e^> f g }

  \break

  %% fail
  \override TupletNumber.Y-offset =
   #(ly:make-unpure-pure-container
      (lambda (grob) (+ (ly:tuplet-number::calc-y-offset grob) 1)))
  \tuplet 3/2 4 {
    c,,8 d e f g a b c d e f g
    c,,8^> d e f^> g a b^> c d e^> f g }

  \break

  %% no fail
  \override TupletNumber.Y-offset =
   #(ly:make-unpure-pure-container
      (lambda (grob) (+ (ly:tuplet-number::calc-y-offset grob) 1))
      (lambda (grob start end) 1))
  \tuplet 3/2 4 {
    c,,8 d e f g a b c d e f g
    c,,8^> d e f^> g a b^> c d e^> f g }
}

Cheers,
  Harm