extract meta data from lilypond compilation

private_includes/base/all.ily

@@ -39,6 +39,7 @@
 \include "title_with_category_images.ily"
 \include "chord_settings.ily"
 \include "chordpro.ily"
+\include "data_extractor.ily"
 \include "transposition.ily"
 \include "markup_tag_groups_hack.ily"
 \include "verses_with_chords.ily"

private_includes/base/data_extractor.ily

@@ -0,0 +1,82 @@
+%%% Extrahiert Informationen aus einem ly:music-Objekt und liefert eine alist
+%%% mit String-Werten zurueck (z.B. ((time . "4/4") (key . "d minor"))).
+%%% Benoetigt LilyPond >= 2.26.
+
+%% note-name->lily-string liegt im Modul (lily display-lily).
+#(use-modules (lily display-lily))
+
+#(begin
+
+   ;; --- Taktangabe --------------------------------------------------------
+
+   ;; Numerator einer Taktangabe kann eine Zahl oder eine Liste sein.
+   (define (numerator->string num)
+     (if (list? num)
+         (string-join (map number->string num) "+")
+         (number->string num)))
+
+   ;; Liefert die Taktangabe als String (z.B. "4/4" oder "7/8") oder #f.
+   ;; time-signature ist ein Paar (numerator . denominator).
+   (define (time-music->string m)
+     (let ((ts (ly:music-property m 'time-signature)))
+       (and (pair? ts)
+            (string-append (numerator->string (car ts)) "/"
+                           (number->string (cdr ts))))))
+
+   ;; --- Tonart ------------------------------------------------------------
+
+   ;; Liefert die Tonart als String (z.B. "d minor" oder "c major") oder #f.
+   ;; Vorgehen wie in LilyPonds eigenem \displayMusic (define-music-display-
+   ;; methods.scm): pitch-alist nach c zuruecktransponieren und mit den
+   ;; bekannten Modus-Definitionen vergleichen. note-name->lily-string liefert
+   ;; den Grundton in der aktuell eingestellten Notensprache.
+   (define (key-music->string m)
+     (let ((tonic (ly:music-property m 'tonic))
+           (alist (ly:music-property m 'pitch-alist)))
+       (and (ly:pitch? tonic) (pair? alist)
+            (let* ((c-alist (ly:transpose-key-alist alist (- tonic)))
+                   (mode (any (lambda (mode)
+                                (and (equal? (ly:parser-lookup mode) c-alist)
+                                     (symbol->string mode)))
+                              '(major minor))))
+              (and mode
+                   (string-append (symbol->string (note-name->lily-string tonic))
+                                  " " mode))))))
+
+   ;; --- Header-Metadaten ----------------------------------------------------
+
+   ;; Nimmt einen Bookpart entgegen (wie HEADER aus pool_bottom.ily) und
+   ;; liefert dessen Header-Felder als alist, z.B.
+   ;; ((title . "Ako umram") (authors . (("..." text melody))) ...).
+   ;; Die Werte bleiben unveraendert, wie sie im \header definiert wurden
+   ;; (Strings, Listen, Markups ...).
+   (define (bookpart->header-alist bookpart)
+     (let ((header (ly:book-header bookpart)))
+       (if (module? header)
+           (sort
+            (filter-map (lambda (entry)
+                          (and (variable-bound? (cdr entry))
+                               (cons (car entry) (variable-ref (cdr entry)))))
+                        (module-map cons header))
+            (lambda (a b)
+              (string<? (symbol->string (car a))
+                        (symbol->string (car b)))))
+           '())))
+
+   ;; --- Hauptfunktion -----------------------------------------------------
+
+   ;; Liefert das erste Music-Objekt mit gegebenem Namen (oder #f).
+   (define (first-named-music music music-name)
+     (let ((matches (extract-named-music music music-name)))
+       (and (pair? matches) (car matches))))
+
+   ;; Nimmt ly:music entgegen und liefert eine alist mit String-Werten.
+   (define (music->data-alist music)
+     (let* ((time-m (first-named-music
+                     music '(TimeSignatureMusic ReferenceTimeSignatureMusic)))
+            (key-m  (first-named-music music 'KeyChangeEvent))
+            (time-s (and time-m (time-music->string time-m)))
+            (key-s  (and key-m  (key-music->string key-m))))
+       (append
+        (if time-s (list (cons 'time time-s)) '())
+        (if key-s  (list (cons 'key key-s)) '())))))

public_includes/layout_bottom.ily

@@ -72,6 +72,8 @@ TEXT = \markuplist {
     (if paper (set! $defaultpaper paper))
   )
 
+  ;(ly:warning (format #f "~a" (bookpart->header-alist HEADER)))
+
   ;; ChordPro export: Store filename and extract metadata from basicSongInfo FIRST
   (when (and (defined? 'chordpro-export-enabled) chordpro-export-enabled)
     ;; Use ly:parser-output-name which returns the output basename