Doc:NR Appendix - Clef Styles - added G2 and modernTab Clefs

[lilypond.git] / scm / define-event-classes.scm

diff --git a/scm/define-event-classes.scm b/scm/define-event-classes.scm
index fb790a591fd562d0fd4b85199a6daad9698f0fbe..40b1b7de40d41d0c3914dcc53ccb79c184347997 100644 (file)
--- a/scm/define-event-classes.scm
+++ b/scm/define-event-classes.scm
@@ -1,6 +1,6 @@
 ;;;; This file is part of LilyPond, the GNU music typesetter.
 ;;;;
-;;;; Copyright (C) 2005--2012 Erik Sandberg <mandolaerik@gmail.com>
+;;;; Copyright (C) 2005--2014 Erik Sandberg <mandolaerik@gmail.com>
 ;;;;
 ;;;; LilyPond is free software: you can redistribute it and/or modify
 ;;;; it under the terms of the GNU General Public License as published by
@@ -78,19 +78,49 @@
                 (acons elt lineage alist))
               classlist class))))
 
+(define all-event-classes
+  (fold (lambda (elt classlist)
+          (event-class-cons (cdr elt) (car elt) classlist))
+        '() event-classes))
+
+;; Maps event-class to a list of ancestors (inclusive)
+(define ancestor-lookup (make-hash-table (length all-event-classes)))
+
+(define (ancestor-lookup-initialize)
+  (hash-clear! ancestor-lookup)
+  (for-each (lambda (ent) (hashq-set! ancestor-lookup (car ent) ent))
+            all-event-classes))
+
+(ancestor-lookup-initialize)
+(call-after-session ancestor-lookup-initialize)
+
 ;; Each class will be defined as
 ;; (class parent grandparent .. )
 ;; so that (eq? (cdr class) parent) holds.
 
+(define-public (define-event-class class parent)
+  "Defines a new event @code{class} derived from @code{parent}, a
+previously defined event class."
+  (let ((parentclass (ly:make-event-class parent)))
+    (cond
+     ((ly:make-event-class class)
+      (ly:error (_ "Cannot redefine event class `~S'") class))
+     ((not parentclass)
+      (ly:error (_ "Undefined parent event class `~S'" parentclass)))
+     (else
+      (hashq-set! ancestor-lookup
+                  class
+                  (cons class parentclass))))
+    *unspecified*))
+
+;; TODO: Allow entering more complex classes, by taking unions.
+(define-public (ly:make-event-class leaf)
+  (hashq-ref ancestor-lookup leaf))
+
 (define-public (ly:in-event-class? ev cl)
   "Does event @var{ev} belong to event class @var{cl}?"
   (memq cl (ly:event-property ev 'class)))
 
-(define-public all-event-classes
-  (fold (lambda (elt classlist)
-          (event-class-cons (cdr elt) (car elt) classlist))
-        '() event-classes))
-
 ;; does this exist in guile already?
 (define (map-tree f t)
   (cond