+ (indent (ly:output-def-lookup layout
+ (if (moment<=? left-mom ZERO-MOMENT)
+ 'indent
+ 'short-indent)
+ 0.0))
+ (system (ly:grob-system grob))
+ (my-extent (ly:grob-extent grob system X))
+ (elements (ly:grob-object system 'elements))
+ (common (ly:grob-common-refpoint-of-array system elements X))
+ (total-ext empty-interval)
+ (align-x (ly:grob-property grob 'self-alignment-X 0))
+ (padding (min 0 (- (interval-length my-extent) indent)))
+ (right-padding (- padding
+ (/ (* padding (1+ align-x)) 2))))
+
+ ;; compensate for the variation in delimiter extents by
+ ;; calculating an X-offset correction based on united extents
+ ;; of all delimiters in this system
+ (let unite-delims ((l (ly:grob-array-length elements)))
+ (if (> l 0)
+ (let ((elt (ly:grob-array-ref elements (1- l))))
+
+ (if (grob::has-interface elt 'system-start-delimiter-interface)
+ (let ((dims (ly:grob-extent elt common X)))
+ (if (interval-sane? dims)
+ (set! total-ext (interval-union total-ext dims)))))
+ (unite-delims (1- l)))))
+
+ (+
+ (ly:side-position-interface::x-aligned-side grob)
+ right-padding
+ (- (interval-length total-ext)))))
+
+(define-public (system-start-text::calc-y-offset grob)
+
+ (define (live-elements-list me)
+ (let* ((elements (ly:grob-object me 'elements))
+ (elts-length (ly:grob-array-length elements))
+ (live-elements '()))
+
+ (let get-live ((len elts-length))
+ (if (> len 0)
+ (let ((elt (ly:grob-array-ref elements (1- len))))
+
+ (if (grob::is-live? elt)
+ (set! live-elements (cons elt live-elements)))
+ (get-live (1- len)))))
+ live-elements))
+
+ (let* ((left-bound (ly:spanner-bound grob LEFT))
+ (live-elts (live-elements-list grob))
+ (system (ly:grob-system grob))
+ (extent empty-interval))
+
+ (if (and (pair? live-elts)
+ (interval-sane? (ly:grob-extent grob system Y)))
+ (let get-extent ((lst live-elts))
+ (if (pair? lst)
+ (let ((axis-group (car lst)))
+
+ (if (and (ly:spanner? axis-group)
+ (equal? (ly:spanner-bound axis-group LEFT)
+ left-bound))
+ (set! extent (add-point extent
+ (ly:grob-relative-coordinate
+ axis-group system Y))))
+ (get-extent (cdr lst)))))
+ ;; no live axis group(s) for this instrument name -> remove from system
+ (ly:grob-suicide! grob))
+
+ (+
+ (ly:self-alignment-interface::y-aligned-on-self grob)
+ (interval-center extent))))