Merge branch 'master' of git://git.savannah.gnu.org/lilypond.git

[lilypond.git] / Documentation / snippets / centering-markup-on-note-heads-automatically.ly

diff --git a/Documentation/snippets/centering-markup-on-note-heads-automatically.ly b/Documentation/snippets/centering-markup-on-note-heads-automatically.ly
index 9f98cd04532631a0b0422bf92ee680be593af4ab..ce227d016e6e8db91ea27efda9f4283d922dfb65 100644 (file)
--- a/Documentation/snippets/centering-markup-on-note-heads-automatically.ly
+++ b/Documentation/snippets/centering-markup-on-note-heads-automatically.ly
@@ -1,52 +1,71 @@
-%% Do not edit this file; it is automatically
-%% generated from LSR http://lsr.dsi.unimi.it
-%% This file is in the public domain.
-\version "2.13.4"
+% DO NOT EDIT this file manually; it is automatically
+% generated from Documentation/snippets/new
+% Make any changes in Documentation/snippets/new/
+% and then run scripts/auxiliar/makelsr.py
+%
+% This file is in the public domain.
+%% Note: this file works from version 2.14.0
+\version "2.14.0"
 
 \header {
-  lsrtags = "text, tweaks-and-overrides"
-
+  lsrtags = "text, tweaks-and-overrides, contexts-and-engravers"
   texidoc = "
 For technical reasons, text scripts attached to note heads cannot
 easily be centered on a note head's width, unlike articulations.
 
-Instead of using trial-and-error offset tweaks, this snippet accesses a
-note head (or rest) from the @code{TextScript} object's horizontal
-parent (a paper column), using its extent to correct the positioning.
-
-
-
+Instead of using trial-and-error offset tweaks, this snippet uses a
+Scheme engraver to reset the horizontal parent of each markup to a
+@code{NoteColumn}.  This also allows text to follow note heads which have
+been shifted via @code{force-hshift}.
 "
   doctitle = "Centering markup on note heads automatically"
 } % begin verbatim
 
-textScriptCenterOnNote = \override TextScript #'X-offset =
-#(lambda (grob)
-   (let* ((paper-col (ly:grob-parent grob X))
-          (elts (ly:grob-object paper-col 'elements))
-          (rhythmic-head
-           (if (ly:grob-array? elts)
-               (let loop ((array-idx 0))
-                 (call/cc
-                  (lambda (return)
-                    (let ((array-len (ly:grob-array-length elts)))
-                      (if (< array-idx (1- array-len))
-                          (let ((elt (ly:grob-array-ref elts array-idx)))
-                            (if (grob::has-interface elt
-                                                     'rhythmic-head-interface)
-                                (return elt)
-                                (loop (1+ array-idx)))))
-                      grob))))
-               grob)))
-
-     (+
-      (ly:self-alignment-interface::x-aligned-on-self grob)
-      (interval-center
-       (ly:grob-robust-relative-extent rhythmic-head rhythmic-head X)))))
-
-\relative c' {
-  \override TextScript #'self-alignment-X = #CENTER
-  \textScriptCenterOnNote
-  c1-\markup \arrow-head #Y #UP ##t
+
+#(define (Text_align_engraver ctx)
+  (let ((scripts '())
+        (note-column #f))
+
+    `((acknowledgers
+       (note-column-interface
+        . ,(lambda (trans grob source)
+             ;; cache NoteColumn in this Voice context
+             (set! note-column grob)))
+
+       (text-script-interface
+        . ,(lambda (trans grob source)
+             ;; whenever a TextScript is acknowledged,
+             ;; add it to `scripts' list
+             (set! scripts (cons grob scripts)))))
+
+      (stop-translation-timestep
+       . ,(lambda (trans)
+            ;; if any TextScript grobs exist,
+            ;; set NoteColumn as X-parent
+            (and (pair? scripts)
+                 (for-each (lambda (script)
+                             (set! (ly:grob-parent script X) note-column))
+                           scripts))
+            ;; clear scripts ready for next timestep
+            (set! scripts '()))))))
+
+\layout {
+  \context {
+    \Voice
+    \consists #Text_align_engraver
+    \override TextScript #'X-offset =
+      #ly:self-alignment-interface::aligned-on-x-parent
+    \override TextScript #'self-alignment-X = #CENTER
+  }
 }
 
+\new Staff <<
+  \relative c'' {
+    \override NoteColumn #'force-hshift = #3
+    c1-\markup { \arrow-head #Y #DOWN ##t }
+  }
+  \\
+  \relative c' {
+    a4 a-\markup { \huge ^ } a a
+  }
+>>