Flaw in note-by-number, how to catch paper in \book ?

[Thomas Morley]

Hi,

here
https://sourceforge.net/p/testlilyissues/issues/5231/#9036
a flaw is reported with note-by-number-markup.
It's triggered, if layout-set-staff-size is set in \paper inside of an
explicit \book

Analysis:
Currently the stem-length is calculated looking at 'text-font-size
from current layout _and_ $defaultpaper, doing some calculations with
the found values (or the fallbacks).
But a \paper in \book is not searched.
I don't know how.

To illustrate, some nutshell-code:

\version "2.21.0"

#(define-markup-command (test layout props arg)(markup?)
  (pretty-print
    (list
      (ly:output-def-lookup $defaultpaper 'foo)
      ;; no difference for (not surprising ...):
      (ly:output-def-lookup (ly:parser-lookup '$defaultpaper) 'foo)
      (ly:output-def-lookup layout 'foo)))

  (interpret-markup layout props arg))

\paper { foo = "foo-default-paper" }
\book {
  \paper { foo = "foo-book-paper" }
  \score {
    { \tempo \markup \test "xy" R1 }
    \layout { foo = "foo-score-layout" }
  }
}

->
("foo-default-paper"
 "foo-default-paper"
 "foo-score-layout")


The "foo-book-paper"-value is not catched.
Any hints how to do so?

Or is the whole approach (looking at 'text-font-size) insufficient?


Thanks,
  Harm