Re: How to catch the current height of a StaffGroup?

[Thomas Morley]

Next try to tackle the main problem, without engraver, but same idea:
Mark some grobs and read out their position.

After defining a 'marker-property and applying it with 'foo and 'bar
to some BarLines, I tried to color them from inside the
BreathingSign-after-line-breaking-override.
Works!

But every time I try to catch their coordinates in Y-axis-direction,
it results in a totally messed up output (but no problem with X-axis)
Regardless if I try:
ly:grob-relative-coordinate
ly:grob-robust-relative-extent
ly:grob-extent

%%%%%%%%%%%%%%%%%

\version "2.15.38"

#(define (define-grob-property symbol type? description)
  (if (not (equal? (object-property symbol 'backend-doc) #f))
      (ly:error (_ "symbol ~S redefined") symbol))

  (set-object-property! symbol 'backend-type? type?)
  (set-object-property! symbol 'backend-doc description)
  symbol)

#(for-each
  (lambda (x)
    (apply define-grob-property x))
    `(
      (marker ,symbol? "Marker(s) in grob for function-call")
    ))

#(define ((staff-group-height number) grob)
     (let* ((stil (ly:text-interface::print grob))
            (par1 (ly:grob-parent grob Y))      ;; #<Grob VerticalAxisGroup >
            (par2 (ly:grob-parent par1 Y))      ;; #<Grob VerticalAlignment >
            (sys (ly:grob-parent par2 Y))       ;; #<Grob System >
            (elements-lst (ly:grob-array->list (ly:grob-object sys
'all-elements)))
            (grob-name (lambda (x) (assq-ref (ly:grob-property x 'meta) 'name)))
            (lst-1 (filter
                      (lambda (x) (and (eq? 'BarLine (grob-name x))
(equal? (ly:grob-property x 'marker) 'foo)))
                         elements-lst))
            (lst-2 (filter
                      (lambda (x) (and (eq? 'BarLine (grob-name x))
(equal? (ly:grob-property x 'marker) 'bar)))
                         elements-lst))
            (top (ly:grob-relative-coordinate (car lst-1) sys Y))
            ;(top (ly:grob-extent (car lst-1) sys Y))
            ;(top (ly:grob-robust-relative-extent (car lst-1) sys Y))

            ;(bottom (ly:grob-relative-coordinate (car lst-2) sys Y))
            ;(bottom (ly:grob-robust-relative-extent (car lst-2) sys Y))
            ;(height (interval-length (cons (car bottom) (cdr top))))
            )

     ;(newline)(display "top    ")(display top)
     ;(newline)(display "bottom ")(display bottom )

     (ly:grob-set-property! (car lst-1) 'color green)
     (ly:grob-set-property! (car lst-2) 'color red)

     (ly:grob-set-property! grob 'stencil
       (grob-interpret-markup grob
           (make-line-markup
             (list
                 (make-with-dimensions-markup '(0 . 0) '(0 . 0)
                   (make-with-color-markup blue
                     (make-draw-line-markup (cons 0 number ))))))))))

%--------- Test

one = {
        \relative c' {
                
                a2 b
                \override Staff.BarLine #'marker = #'foo
                \override Score.BreathingSign #'after-line-breaking =
                        #(staff-group-height -13)
                
                c\breathe
                d \break
                a,, b''
                
                \override Score.BreathingSign #'after-line-breaking =
                        #(staff-group-height -22.5)
                
                c\breathe d
        }
}

two = {
        \relative c {
                \clef bass
                a2 b \override Staff.BarLine #'marker = #'bar
                c d a'' b,, c d
        }
}

\score {
        \new StaffGroup <<
           \new Staff \one
           \new Staff \one
           \new Staff \one
           \new Staff \two
           >>
}

%%%%%%%%%%%%%%%%%%%%%%%

What am I missing?

-Harm