Hi, all -- Attached is a function which started out as an attempt to get tempo indications to line up with the left edge of the time signature. It's been generalized so that you can left-align any grob responsive to 'extra-offset to the closest grob of a specified type in that system (as far as I can tell so far -- you could even left-align a notehead to a barline, if you were so inclined...)
It locates the closest grob by first searching all of the grobs in a system for every instance of the target type, then selecting the one that is closest horizontally. (For example, if you want to align something to a barline, the function would determine where all the barlines are, then choose the nearest one). I have several questions: (1) Is there a way to locate the nearest grob more efficiently, so the routine doesn't have to search the entire system? (2) Is there a way to exclude grobs that are in the same system, but on a different staff? I've looked at the 'staff-symbol property, but it's empty in some cases. (3) Does anybody have any suggestions how to improve the coding? I'm enjoying learning Scheme, but my approach is rather hit-and-miss! Best, David
\version "2.12.3"
leftAlignGrob =
#(define-music-function (parser location grob-to-align reference-grob) (string? symbol?)
#{
\overrideProperty $grob-to-align #'after-line-breaking #(lambda (grob)
(let* ((sys (ly:grob-system grob))
(array (ly:grob-object sys 'all-elements))
(len (ly:grob-array-length array))
(current-grob-in-search (lambda (q)
(assq-ref (ly:grob-property (ly:grob-array-ref array q) 'meta) 'name)))
(default-coord (ly:grob-relative-coordinate grob sys X))
(lst '()))
;; find all instances in a system of the grob we want to use for alignment
;; returns list of X-coordinates, minus duplicates
(let lp ((x len))
(if (positive? x)
(begin
(if (eq? $reference-grob (current-grob-in-search (1- x)))
(set! lst
(uniq-list (append lst
(list (ly:grob-relative-coordinate (ly:grob-array-ref array (1- x)) sys X))))))
(lp (1- x)))))
;; find the value in the list closest to the X-coordinate of object to be aligned
(let ((ref (car lst)))
(define closest (lambda (x)
(if (< (abs (- default-coord (car x))) (abs (- default-coord ref)))
(set! ref (car x)))
(if (not (null? (cdr x)))
(closest (cdr x)))))
(closest lst)
(ly:grob-set-property! grob 'extra-offset `(,(- ref default-coord) . 0)))))
#}
)
\relative c' {
%% bar 1
\time 3/4
\key d \major
\leftAlignGrob #"Score.MetronomeMark" #'TimeSignature
\tempo 4 = 120
\once \override TextScript #'padding = #2
\leftAlignGrob #"TextScript" #'Clef
d_"clef"
\leftAlignGrob #"TextScript" #'KeySignature
e_"key sig." fis
%% bar 2
e
\once \override Hairpin #'X-offset = #-1
\leftAlignGrob #"TextScript" #'Hairpin
d\<_"hairpin (offset)" e
%% bar 3
\leftAlignGrob #"TextScript" #'BarLine
\time 2/4
fis^"bar" d
%% bar 4
\time 4/4
\leftAlignGrob #"TextScript" #'TimeSignature
e^"meter" fis d
\once \override DynamicText #'X-offset = #0.5
\leftAlignGrob #"TextScript" #'DynamicText
fis\f_"dynamic (offset)"
%% bar 5
\leftAlignGrob #"TextScript" #'Stem
\time 3/4
e^"stem" fis d
%% bar 6
\leftAlignGrob #"Score.RehearsalMark" #'TimeSignature
\mark #1
\time 2/4
fis d
}
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