+#include "event.hh"
+#include "item.hh"
+#include "group-interface.hh"
+
+
+
+/*
+ this engraver glues together stems, rests and note heads into a NoteColumn
+ grob.
+
+ It also generates spacing objects. Originally, we have tried to
+ have the spacing functionality at different levels.
+
+ - by simply using the sequence of Separation-item as
+ spacing-sequences (at staff level). Unfortunately, this fucks up if
+ there are different kinds of tuplets in different voices (8th and
+ 8ths triplets combined made the program believe there were 1/12 th
+ notes.).
+
+ Doing it in a separate engraver using timing info is generally
+ complicated (start/end time management), and fucks up if a voice
+ changes staff.
+
+ Now we do it from here again. This has the problem that voices can
+ appear and disappear at will, leaving lots of loose ends (the note
+ spacing engraver don't know where to connect the last note of the
+ voice on the right with), but we don't complain about those, and let
+ the default spacing do its work.
+
+ */