Keep a staff alive with multiple layers

This allows the `VerticalAxisGroup.remove-layer'
property to accept a list of values. The layer
will stay alive with any other member of the
Keep_alive_together_engrave group with a
remove-layer value in that list.

The principal reason for this patch was to
allow the use of MarkLine contexts in a Frenched
score, where the context should stay alive with
any single staff in a StaffGroup.

This implementation should also allow additional
flexibility with ossia and divisi staves.

1 files changed, 65 insertions, 0 deletions

diff --git a/input/regression/remove-layer-symbol.ly b/input/regression/remove-layer-symbol.ly
new file mode 100644
index 0000000000..d6fa93dcdd
--- /dev/null
+++ b/input/regression/remove-layer-symbol.ly
@@ -0,0 +1,65 @@
+\version "2.19.48"
+
+\header {
+  texidoc = "The @code{VerticalAxisGroup.remove-layer} property
+  can be used to keep staves alive with reference to other staves
+  in the @code{Keep_alive_together_engraver} group."
+}
+
+\layout {
+  indent = 40\mm
+  short-indent = 15\mm
+}
+
+\score {
+  <<
+    \new Staff \with {
+      instrumentName = "Continuous"
+      shortInstrumentName = "cont"
+    } { \repeat unfold 104 g'4 \bar "|." }
+    \new StaffGroup \with {
+      \consists Keep_alive_together_engraver
+    } <<
+      \new Staff \with {
+        keepAliveInterfaces = #'()
+        instrumentName = \markup \center-column { "Alive with A or B" }
+        shortInstrumentName = "with A or B"
+        \override VerticalAxisGroup.remove-empty = ##t
+        \override VerticalAxisGroup.remove-first = ##t
+        \override VerticalAxisGroup.remove-layer = #'any
+      } { \repeat unfold 104 c''4 }
+      \new Staff \with {
+        instrumentName = "A"
+        shortInstrumentName = "A"
+        \override VerticalAxisGroup.remove-empty = ##t
+        \override VerticalAxisGroup.remove-first = ##t
+        \override VerticalAxisGroup.remove-layer = ##f
+      } {
+        \repeat unfold 16 c'4
+        R1*4
+        \repeat unfold 16 c'4
+        R1*14
+      }
+      \new Staff \with {
+        keepAliveInterfaces = #'()
+        instrumentName = \markup \center-column { "Alive with A" }
+        shortInstrumentName = "with A"
+        \override VerticalAxisGroup.remove-empty = ##t
+        \override VerticalAxisGroup.remove-first = ##t
+        \override VerticalAxisGroup.remove-layer = #'above
+      } { \repeat unfold 104 c''4 }
+      \new Staff \with {
+        instrumentName = "B"
+        shortInstrumentName = "B"
+        \override VerticalAxisGroup.remove-empty = ##t
+        \override VerticalAxisGroup.remove-first = ##t
+        \override VerticalAxisGroup.remove-layer = ##f
+      } {
+        R1*8
+        \repeat unfold 16 c'4
+        R1*13
+        c'1
+      }
+    >>
+  >>
+}