release: 1.5.4

[lilypond.git] / lily / include / sequential-music-iterator.hh

diff --git a/lily/include/sequential-music-iterator.hh b/lily/include/sequential-music-iterator.hh
index 6f13f441411e78d526a613da6d28b12db3c1d628..fcedb517f77ddbdca36de33ed0c24d6ea11bc254 100644 (file)
--- a/lily/include/sequential-music-iterator.hh
+++ b/lily/include/sequential-music-iterator.hh
@@ -12,11 +12,35 @@
 #include "music-iterator.hh"
 
 
+/*
+
+  This is a lookahead list for grace notes.
+
+   {  ... X \grace Y  Z ... }
+
+   normally, the ending of X is the start of Z. In case of a grace
+   note, we take off a little at the end of X. What is stored: START
+   (start point of X), LENGTH (length of X), GRACE_START (start_music
+   of Y), and the next fixup element.
+
+  This is also done for nested musics, i.e.
+
+  voiceA = \notes { \grace b16 c'2 }
+  voiceB = \notes { c'2 \voiceA }
+
+  the iterator for voiceB will contain a fixup entry with (START=0/1,
+  LENGTH=2/1, GRACE_START=(0G-1/16) ) 
+   
+  Graces at the start of a sequential music iterator are handled
+  by initting here_mom_ with Music::start_music (); no fixups are needed.
+
+*/
 struct Grace_skip 
 {
   Moment start_;
   Rational length_;
-  Rational grace_length_;  
+
+  Rational grace_start_;  
   Grace_skip *next_;
 };