Documentation/snippets/centering-markup-on-note-heads-automatically.ly

   1 % Do not edit this file; it is automatically
   2 % generated from Documentation/snippets/new
   3 % This file is in the public domain.
   4 %% Note: this file works from version 2.13.15
   5 \version "2.13.29"
   6
   7 \header {
   8   lsrtags = "text, tweaks-and-overrides, contexts-and-engravers"
   9   texidoc = "
  10 For technical reasons, text scripts attached to note heads cannot
  11 easily be centered on a note head's width, unlike articulations.
  12
  13 Instead of using trial-and-error offset tweaks, this snippet uses a
  14 Scheme engraver to reset the horizontal parent of each markup to a
  15 @code{NoteColumn}.  This also allows text to follow note heads which have
  16 been shifted via @code{force-hshift}.
  17 "
  18   doctitle = "Centering markup on note heads automatically"
  19 } % begin verbatim
  20
  21
  22 #(define (Text_align_engraver ctx)
  23   (let ((scripts '())
  24         (note-column #f))
  25
  26     `((acknowledgers
  27        (note-column-interface
  28         . ,(lambda (trans grob source)
  29              ;; cache NoteColumn in this Voice context
  30              (set! note-column grob)))
  31
  32        (text-script-interface
  33         . ,(lambda (trans grob source)
  34              ;; whenever a TextScript is acknowledged,
  35              ;; add it to `scripts' list
  36              (set! scripts (cons grob scripts)))))
  37
  38       (stop-translation-timestep
  39        . ,(lambda (trans)
  40             ;; if any TextScript grobs exist,
  41             ;; set NoteColumn as X-parent
  42             (and (pair? scripts)
  43                  (for-each (lambda (script)
  44                              (set! (ly:grob-parent script X) note-column))
  45                            scripts))
  46             ;; clear scripts ready for next timestep
  47             (set! scripts '()))))))
  48
  49 \layout {
  50   \context {
  51     \Voice
  52     \consists #Text_align_engraver
  53     \override TextScript #'X-offset =
  54       #ly:self-alignment-interface::aligned-on-x-parent
  55     \override TextScript #'self-alignment-X = #CENTER
  56   }
  57 }
  58
  59 \new Staff <<
  60   \relative c'' {
  61     \override NoteColumn #'force-hshift = #3
  62     c1-\markup { \arrow-head #Y #DOWN ##t }
  63   }
  64   \\
  65   \relative c' {
  66     a4 a-\markup { \huge ^ } a a
  67   }
  68 >>