From 8abb84c2bf30e32702ecd274df7bfa114f0d851f Mon Sep 17 00:00:00 2001
From: Valentin Villenave <address@hidden>
Date: Thu, 31 Oct 2013 21:15:06 +0100
Subject: [PATCH] Make Dynamics into a Staff-like context.

This commit creates a DynamicsVoice context, and moves the former
Dynamics context to a higher (Staff-like) level.  This should
allow to assign variables that contain polyphonic sections without
unintended side effects (such as additional Voice and Staff
contexts being created whenever a VoiceSeparator \\ is entered).
---
 input/regression/dynamics-polyphony.ly | 42 ++++++++++++++++++++++++++++++++++
 ly/engraver-init.ly                    | 27 +++++++++++++++-------
 2 files changed, 61 insertions(+), 8 deletions(-)
 create mode 100644 input/regression/dynamics-polyphony.ly

diff --git a/input/regression/dynamics-polyphony.ly b/input/regression/dynamics-polyphony.ly
new file mode 100644
index 0000000..898913e
--- /dev/null
+++ b/input/regression/dynamics-polyphony.ly
@@ -0,0 +1,42 @@
+\version "2.17.30"
+
+\header {
+  texidoc = "The Dynamics context can handle multiple voices,
+even though it may lead to collisions."
+}
+
+music = \relative c' {
+  f2\mp c' |
+  << % Creating two temporary DynamicsVoice contexts.
+    { bes8\> c d bes a2\p }
+    \\
+    { g\sfz f } % collides with the spanner.
+  >>
+}
+
+% The actual staves will be printed without dynamics.
+#(define (dynamic? x)
+  (let ((name (ly:music-property x 'name)))
+    (or
+     (eq? name 'DynamicEvent)
+     (eq? name 'AbsoluteDynamicEvent)
+     (eq? name 'CrescendoEvent)
+     (eq? name 'DecrescendoEvent)
+     (eq? name 'SpanDynamicEvent))))
+
+removeDynamics =
+#(define-music-function (parser location music) (ly:music?)
+  (music-filter
+   (lambda (x)
+     (not (dynamic? x)))
+ music))
+  
+\score {
+  \new PianoStaff <<
+    \new Staff \removeDynamics \music
+    \new Dynamics \music
+    \new Staff \removeDynamics {
+      \clef bass \transpose c c, \music
+    }
+  >>
+}
diff --git a/ly/engraver-init.ly b/ly/engraver-init.ly
index 9c8547d..27381b3 100644
--- a/ly/engraver-init.ly
+++ b/ly/engraver-init.ly
@@ -16,7 +16,7 @@
 %%%% You should have received a copy of the GNU General Public License
 %%%% along with LilyPond.  If not, see <http://www.gnu.org/licenses/>.
 
-\version "2.17.29"
+\version "2.17.30"
 
 \context {
   \name "Global"
@@ -391,7 +391,7 @@ a collection of staves, with a bracket in front and spanning bar lines."
 
 \context {
   \type "Engraver_group"
-  \name Dynamics
+  \name DynamicsVoice
   \alias Voice
   \consists "Output_property_engraver"
   \consists "Bar_engraver"
@@ -402,14 +402,9 @@ a collection of staves, with a bracket in front and spanning bar lines."
   \consists "Text_engraver"
   \consists "Text_spanner_engraver"
   \consists "Font_size_engraver"
-  \consists "Axis_group_engraver"
 
   pedalSustainStrings = #'("Ped." "*Ped." "*")
   pedalUnaCordaStrings = #'("una corda" "" "tre corde")
-  \override VerticalAxisGroup.staff-affinity = #CENTER
-  \override VerticalAxisGroup.nonstaff-relatedstaff-spacing =
-    #'((basic-distance . 5)
-       (padding . 0.5))
   \override TextScript.font-shape = #'italic
   \override DynamicLineSpanner.Y-offset = #0
   \override DynamicLineSpanner.outside-staff-priority = ##f
@@ -423,11 +418,27 @@ a collection of staves, with a bracket in front and spanning bar lines."
       ,(ly:make-simple-closure
         (list ly:self-alignment-interface::x-aligned-on-self))))
 
+  \description "Corresponds to the dynamics of a single voice.
+Using the upper-level Dynamics context as a wrapper is preferred,
+since it can handle polyphonic variables as well."
+}
+
+\context {
+  \type "Engraver_group"
+  \name "Dynamics"
+  \alias "Staff"
+  \accepts "DynamicsVoice"
+  \defaultchild "DynamicsVoice"
+  \consists "Axis_group_engraver"
+  \override VerticalAxisGroup.staff-affinity = #CENTER
+  \override VerticalAxisGroup.nonstaff-relatedstaff-spacing =
+    #'((basic-distance . 5)
+       (padding . 0.5))
+
   \description "Holds a single line of dynamics, which will be
 centered between the staves surrounding this context."
 }
 
-
 \context{
   \type "Engraver_group"
 
-- 
1.8.3.1