From 8b319023245efd2666cb8ae3ff006d99f64d35d7 Mon Sep 17 00:00:00 2001
From: Valentin Villenave <valentin@localhost.(none)>
Date: Sat, 18 Oct 2008 22:53:32 +0200
Subject: [PATCH] new showFirstLength feature

This commits implements a showFirstLength property, that does
the opposite of showLastLength (both properties may be set,
in this case the beginning and the end of the piece are printed,
with a double barline as separator).

When only showFirstLength is set, the 'length property is
overriden and therefore the compilation becomes much faster.

This new feature may be very convenient, e.g. to print the
index of a book containing only the beginning of each \score.
---
 .../skiptypesetting-show-last-or-first.ly          |   27 +++++
 input/regression/skiptypesetting-show-last.ly      |   18 ----
 scm/music-functions.scm                            |  101 ++++++++++++++------
 3 files changed, 98 insertions(+), 48 deletions(-)
 create mode 100644 input/regression/skiptypesetting-show-last-or-first.ly
 delete mode 100644 input/regression/skiptypesetting-show-last.ly

diff --git a/input/regression/skiptypesetting-show-last-or-first.ly b/input/regression/skiptypesetting-show-last-or-first.ly
new file mode 100644
index 0000000..432298b
--- /dev/null
+++ b/input/regression/skiptypesetting-show-last-or-first.ly
@@ -0,0 +1,27 @@
+\header {
+
+  texidoc = "@code{showLastLength} will only show the last bit of a score;
+@code{showFirstLength} will only show the beginning."
+
+  }
+
+\version "2.11.63"
+  
+  
+music = {
+  c1 d e f g a
+}
+
+showLastLength = R1*3
+
+\new Staff \music
+
+showLastLength = ""
+showFirstLength = R1*2
+
+\new Staff \music
+
+showLastLength = R1*2
+showFirstLength = R1
+
+\new Staff \music
diff --git a/input/regression/skiptypesetting-show-last.ly b/input/regression/skiptypesetting-show-last.ly
deleted file mode 100644
index def23fc..0000000
--- a/input/regression/skiptypesetting-show-last.ly
+++ /dev/null
@@ -1,18 +0,0 @@
-\header {
-
-  texidoc = "@code{showLastLength} will only show the last bit of a score"
-
-  }
-
-\version "2.11.51"
-
-showLastLength = R1*3
-\paper {
-  ragged-right = ##T
-}
-
-{
-  c1 c1
-  c1 c1
-  c1 c1
-}
diff --git a/scm/music-functions.scm b/scm/music-functions.scm
index 490cafe..cabb9cc 100644
--- a/scm/music-functions.scm
+++ b/scm/music-functions.scm
@@ -823,40 +823,81 @@ Syntax:
 	(ly:music-length music))
   music)
 
-(define (skip-to-last music parser)
-
-  "Replace MUSIC by
-
-<< { \\set skipTypesetting = ##t
-     LENGTHOF(\\showLastLength)
-     \\set skipTypesetting = ##t  }
+(define (skip-this m)
+          (make-sequential-music
+           (list
+            (context-spec-music (make-property-set 'skipTypesetting #t)
+              'Score)
+            (make-music 'SkipMusic 'duration
+            (ly:make-duration 0 0
+             (ly:moment-main-numerator m)
+             (ly:moment-main-denominator m)))
+            (context-spec-music (make-property-set 'skipTypesetting #f)
+              'Score))))
+
+(define (unskip-this m)
+          (make-sequential-music
+           (list
+            (context-spec-music (make-property-set 'skipTypesetting #f)
+              'Score)
+            (make-music 'SkipMusic 'duration
+            (ly:make-duration 0 0
+             (ly:moment-main-numerator m)
+             (ly:moment-main-denominator m)))
+            (context-spec-music (make-property-set 'skipTypesetting #t)
+              'Score))))
+
+(define (skip-as-needed music parser)
+    "Replace MUSIC by
+    << {  \\set skipTypesetting = ##f
+    LENGTHOF(\\showFirstLength)
+     \\set skipTypesetting = ##t
+    LENGTHOF(\\showLastLength) }
     MUSIC >>
-
-if appropriate.
- "
+    if appropriate.
+    
+    When only showFirstLength is set,
+    the 'length property of the music is
+    directly overridden to speed up compiling."
   (let*
-      ((show-last  (ly:parser-lookup parser 'showLastLength)))
+      ((show-last  (ly:parser-lookup parser 'showLastLength))
+       (show-first  (ly:parser-lookup parser 'showFirstLength)))
+   (cond
     
-    (if (ly:music? show-last)
-	(let*
+      ;; both properties may be set.
+    ((and (ly:music? show-first) (ly:music? show-last))
+       (let*
+        ((orig-length (ly:music-length music))
+	       (skip-length (ly:moment-sub orig-length (ly:music-length show-last)))
+         (begin-length (ly:music-length show-first)))
+         (make-simultaneous-music
+          (list
+           (make-sequential-music
+            (list
+             (skip-this skip-length)
+             ;; let's draw a double barline between the beginning and the end
+             (make-music 'PropertySet 'value "||"
+                         'symbol 'whichBar)))
+           (unskip-this begin-length)
+           music))))
+
+       ;; we may only want to print the last length
+    ((ly:music? show-last)
+     (let*
 	    ((orig-length (ly:music-length music))
 	     (skip-length (ly:moment-sub orig-length (ly:music-length show-last))))
-
-	  (make-simultaneous-music
-	   (list
-	    (make-sequential-music
-	     (list
-	      (context-spec-music (make-property-set 'skipTypesetting #t)
-				  'Score)
-	      (make-music 'SkipMusic 'duration
-			  (ly:make-duration
-			   0 0
-			   (ly:moment-main-numerator skip-length)
-			   (ly:moment-main-denominator skip-length)))
-	      (context-spec-music (make-property-set 'skipTypesetting #f)
-				  'Score)))
-	    music)))
-	music)))
+       (make-simultaneous-music
+        (list
+         (skip-this skip-length)
+         music))))
+
+       ;; we may only want to print the beginning; in this case
+       ;; only the first length will be processed (much faster).
+    ((ly:music? show-first)
+    	(set! (ly:music-property music 'length)
+       (ly:music-length show-first))
+      music)
+	  (else music))))
     
 
 (define-public toplevel-music-functions
@@ -872,7 +913,7 @@ if appropriate.
    (lambda (x parser) (music-map cue-substitute x))
  
    (lambda (x parser)
-     (skip-to-last x parser)
+     (skip-as-needed x parser)
    )))
 
 
-- 
1.6.0.2