rework snap

snap now fills in a struct (MusicFrame) which contins a snapped frame
along with a music divisor.
this gives useful information wrt magnetic snap which may or may not
have rounded to an exact musical position.

region position may now be set musically (using quarter notes for now).

this patch fixes several problems in the current code:

	- dragging a list of music-locked regions now maintains correct
	  musical offsets within the list.

	- splitting regions using magnetic snap works correctly (#7192)

	- cut drag should now work correctly with magnetic snap.

	- musical length of split midi regions is no longer frame based.

1 files changed, 76 insertions, 0 deletions

diff --git a/libs/ardour/midi_playlist.cc b/libs/ardour/midi_playlist.cc
index 67764d66ae..20c1c77111 100644
--- a/libs/ardour/midi_playlist.cc
+++ b/libs/ardour/midi_playlist.cc
@@ -33,7 +33,9 @@
 #include "ardour/midi_region.h"
 #include "ardour/midi_source.h"
 #include "ardour/midi_state_tracker.h"
+#include "ardour/region_factory.h"
 #include "ardour/session.h"
+#include "ardour/tempo.h"
 #include "ardour/types.h"
 
 #include "pbd/i18n.h"
@@ -381,6 +383,80 @@ MidiPlaylist::destroy_region (boost::shared_ptr<Region> region)
 
 	return changed;
 }
+void
+MidiPlaylist::_split_region (boost::shared_ptr<Region> region, MusicFrame playlist_position)
+{
+	if (!region->covers (playlist_position.frame)) {
+		return;
+	}
+
+	if (region->position() == playlist_position.frame ||
+	    region->last_frame() == playlist_position.frame) {
+		return;
+	}
+
+	boost::shared_ptr<const MidiRegion> mr = boost::dynamic_pointer_cast<MidiRegion>(region);
+
+	if (mr == 0) {
+		return;
+	}
+
+	boost::shared_ptr<Region> left;
+	boost::shared_ptr<Region> right;
+
+	string before_name;
+	string after_name;
+	const double before_qn = _session.tempo_map().exact_qn_at_frame (playlist_position.frame, playlist_position.division) - region->quarter_note();
+	const double after_qn = mr->length_beats() - before_qn;
+	MusicFrame before (playlist_position.frame - region->position(), playlist_position.division);
+	MusicFrame after (region->length() - before.frame, playlist_position.division);
+
+	/* split doesn't change anything about length, so don't try to splice */
+	bool old_sp = _splicing;
+	_splicing = true;
+
+	RegionFactory::region_name (before_name, region->name(), false);
+
+	{
+		PropertyList plist;
+
+		plist.add (Properties::length, before.frame);
+		plist.add (Properties::length_beats, before_qn);
+		plist.add (Properties::name, before_name);
+		plist.add (Properties::left_of_split, true);
+		plist.add (Properties::layering_index, region->layering_index ());
+		plist.add (Properties::layer, region->layer ());
+
+		/* note: we must use the version of ::create with an offset here,
+		   since it supplies that offset to the Region constructor, which
+		   is necessary to get audio region gain envelopes right.
+		*/
+		left = RegionFactory::create (region, MusicFrame (0, 0), plist, true);
+	}
+
+	RegionFactory::region_name (after_name, region->name(), false);
+
+	{
+		PropertyList plist;
+
+		plist.add (Properties::length, after.frame);
+		plist.add (Properties::length_beats, after_qn);
+		plist.add (Properties::name, after_name);
+		plist.add (Properties::right_of_split, true);
+		plist.add (Properties::layering_index, region->layering_index ());
+		plist.add (Properties::layer, region->layer ());
+
+		/* same note as above */
+		right = RegionFactory::create (region, before, plist, true);
+	}
+
+	add_region_internal (left, region->position(), 0, region->quarter_note(), true);
+	add_region_internal (right, region->position() + before.frame, before.division, region->quarter_note() + before_qn, true);
+
+	remove_region_internal (region);
+
+	_splicing = old_sp;
+}
 
 set<Evoral::Parameter>
 MidiPlaylist::contained_automation()