Doc: NR @knownissues for #'ignore-collision

Added @knownissue when using #'ignore-collision and \mergedifferently*
commands.

Updated @knownissue in 'simultaneous expressions' to x-ref this as well.

Added some more appropriate @cindex entries for collision.

diff --git a/Documentation/notation/simultaneous.itely b/Documentation/notation/simultaneous.itely
index d827fad597b2621a2934ac44fb4c8b7693ab7bd8..47dfcf364a561f00fa516b34656386cde0d82e20 100644 (file)
--- a/Documentation/notation/simultaneous.itely
+++ b/Documentation/notation/simultaneous.itely
@@ -209,6 +209,9 @@ generate multiple staves implicitly:
 
 Here different rhythms cause no problems.
 
+@cindex collisions, clashing note columns
+@cindex collisions, ignoring
+
 @knownissues
 If notes from two or more voices, with stems in the same direction, are
 placed at the same position on the staff and have no shift (or have the
@@ -224,8 +227,9 @@ will appear during compilation.  This message can be suppressed by:
 \override NoteColumn #'ignore-collision = ##t
 @end example
 
-However, this does not only suppress the warning but will prevent any
-collision resolution, so may have unintended results.
+However, this not only suppresses the warning but will prevent any
+collision resolution whatsover and may have other unintended effects
+(also see @emph{Known Issues} in @ref{Collision resolution}).
 
 
 @node Clusters
@@ -644,7 +648,6 @@ also be merged:
 >>
 @end lilypond
 
-
 The half note and eighth note at the start of the second measure
 are incorrectly merged because the automatic merge cannot
 successfully complete the merge when three or more notes line up in
@@ -727,7 +730,6 @@ Notes are only merged if they have opposing stem directions (as
 they have, for example, in voices one and two by default or when
 the stems are explicitly set in opposite directions).
 
-
 @predefined
 @code{\mergeDifferentlyDottedOn},
 @code{\mergeDifferentlyDottedOff},
@@ -740,16 +742,13 @@ the stems are explicitly set in opposite directions).
 @code{\shiftOff}.
 @endpredefined
 
-
 @snippets
-
 @lilypondfile[verbatim,quote,texidoc,doctitle]
 {additional-voices-to-avoid-collisions.ly}
 
 @lilypondfile[verbatim,quote,texidoc,doctitle]
 {forcing-horizontal-shift-of-notes.ly}
 
-
 @seealso
 Music Glossary:
 @rglos{polyphony}.
@@ -767,6 +766,18 @@ Internals Reference:
 @rinternals{NoteCollision},
 @rinternals{RestCollision}.
 
+@cindex collisions, ignoring
+
+@knownissues
+Using @code{\override NoteColumn #'ignore-collision = ##t} will cause
+differently headed notes in different voices to merge incorrectly.
+
+@lilypond[quote,relative=1,verbatim]
+\mergeDifferentlyHeadedOn
+<< { c16 a' b a } \\ { c,2 } >>
+\override NoteColumn #'ignore-collision = ##t
+<< { c16 a' b a } \\ { c,2 } >>
+@end lilypond
 
 @ignore
 @knownissues