Revert internals of the last layering-related commit, and go back a slightly-cleaned-up version of how it was before. Remove all layering modes; only option now is add-is-higher. Move-add-higher could easily be re-added if anyone uses it.

git-svn-id: svn://localhost/ardour2/branches/3.0@11111 d708f5d6-7413-0410-9779-e7cbd77b26cf

19 files changed, 304 insertions, 1204 deletions

diff --git a/libs/ardour/ardour/playlist.h b/libs/ardour/ardour/playlist.h
index a8be02a0b9..a7ead83eef 100644
--- a/libs/ardour/ardour/playlist.h
+++ b/libs/ardour/ardour/playlist.h
@@ -44,9 +44,6 @@
 #include "ardour/session_object.h"
 #include "ardour/data_type.h"
 
-class PlaylistOverlapCacheTest;
-class PlaylistLayeringTest;
-
 namespace ARDOUR  {
 
 class Session;
@@ -225,10 +222,7 @@ public:
 	framepos_t find_next_top_layer_position (framepos_t) const;
 	uint32_t combine_ops() const { return _combine_ops; }
 
-	void relayer (boost::shared_ptr<Region>);
-	void relayer (boost::shared_ptr<Region>, double);
-	void suspend_relayer ();
-	void resume_relayer ();
+	uint64_t highest_layering_index () const;
 	
   protected:
 	friend class Session;
@@ -355,7 +349,7 @@ public:
 	boost::shared_ptr<Playlist> cut (framepos_t start, framecnt_t cnt, bool result_is_hidden);
 	boost::shared_ptr<Playlist> copy (framepos_t start, framecnt_t cnt, bool result_is_hidden);
 
-	void relayer (RegionList const &);
+	void relayer ();
 
 	void begin_undo ();
 	void end_undo ();
@@ -382,71 +376,6 @@ public:
 	   with its constituent regions
 	*/
 	virtual void pre_uncombine (std::vector<boost::shared_ptr<Region> >&, boost::shared_ptr<Region>) {}
-
-private:
-	friend class ::PlaylistOverlapCacheTest;
-	friend class ::PlaylistLayeringTest;
-	
-	/** A class which is used to store temporary (fractional)
-	 *  layer assignments for some regions.
-	 */
-	class TemporaryLayers
-	{
-	public:
-		void set (boost::shared_ptr<Region>, double);
-		double get (boost::shared_ptr<Region>) const;
-
-	private:		
-		typedef std::map<boost::shared_ptr<Region>, double> Map;
-		Map _map;
-	};
-
-	/** Class to sort by temporary layer, for use with std::list<>::sort() */
-	class SortByTemporaryLayer
-	{
-	public:
-		SortByTemporaryLayer (TemporaryLayers const & t)
-			: _temporary_layers (t) {}
-		
-		bool operator() (boost::shared_ptr<Region> a, boost::shared_ptr<Region> b) const {
-			return _temporary_layers.get (a) < _temporary_layers.get (b);
-		}
-
-	private:
-		Playlist::TemporaryLayers const & _temporary_layers;
-	};
-
-	/** A cache of what overlaps what, for a given playlist in a given state.
-	 *  Divides a playlist up into time periods and notes which regions cover those
-	 *  periods, so that get() is reasonably quick.
-	 */
-	class OverlapCache
-	{
-	public:
-		OverlapCache (Playlist *);
-
-		RegionList get (Evoral::Range<framepos_t>) const;
-
-	private:
-		std::pair<int, int> cache_indices (Evoral::Range<framepos_t>) const;
-		
-		double _division_size;
-		std::vector<RegionList> _cache;
-		Evoral::Range<framepos_t> _range;
-
-		static int const _divisions;
-	};
-	
-	TemporaryLayers compute_temporary_layers (RegionList const &);
-	void commit_temporary_layers (TemporaryLayers const &);
-
-	RegionList recursive_regions_touched (boost::shared_ptr<Region>, OverlapCache const &, boost::shared_ptr<Region>) const;
-	void recursive_regions_touched_sub (boost::shared_ptr<Region>, OverlapCache const &, boost::shared_ptr<Region>, RegionList &) const;
-
-	void timestamp_layer_op (LayerOp, boost::shared_ptr<Region>);
-	uint64_t layer_op_counter;
-
-	bool _relayer_suspended;
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index 4315ed7aa8..ab1559fc4a 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -65,6 +65,7 @@ namespace Properties {
 	extern PBD::PropertyDescriptor<float>             stretch;
 	extern PBD::PropertyDescriptor<float>             shift;
 	extern PBD::PropertyDescriptor<PositionLockStyle> position_lock_style;
+	extern PBD::PropertyDescriptor<uint64_t>          layering_index;
 };
 
 class Playlist;
@@ -112,7 +113,6 @@ class Region
 	framepos_t start ()     const { return _start; }
 	framecnt_t length ()    const { return _length; }
 	layer_t    layer ()     const { return _layer; }
-	Evoral::Range<framepos_t> bounds () const;
 
 	framecnt_t source_length(uint32_t n) const;
 	uint32_t   max_source_level () const;
@@ -202,7 +202,7 @@ class Region
 	void cut_front (framepos_t new_position);
 	void cut_end (framepos_t new_position);
 
-	void set_layer (layer_t l); /* ONLY Playlist should call this */
+	void set_layer (layer_t l); /* ONLY Playlist can call this */
 	void raise ();
 	void lower ();
 	void raise_to_top ();
@@ -252,8 +252,8 @@ class Region
 
 	virtual boost::shared_ptr<Region> get_parent() const;
 
-	uint64_t last_layer_op (LayerOp) const;
-	void set_last_layer_op (LayerOp, uint64_t);
+	uint64_t layering_index () const { return _layering_index; }
+	void set_layering_index (uint64_t when) { _layering_index = when; }
 
 	virtual bool is_dependent() const { return false; }
 	virtual bool depends_on (boost::shared_ptr<Region> /*other*/) const { return false; }
@@ -294,12 +294,11 @@ class Region
 
 	void invalidate_transients ();
 
-	void drop_sources ();
+	void set_pending_layer (double);
+	bool reset_pending_layer ();
+	boost::optional<double> pending_layer () const;
 
-	/** @return our bounds the last time our relayer() method was called */
-	Evoral::Range<framepos_t> last_relayer_bounds () const {
-		return Evoral::Range<framepos_t> (_last_relayer_bounds_from, _last_relayer_bounds_to);
-	}
+	void drop_sources ();
 
   protected:
 	friend class RegionFactory;
@@ -384,18 +383,15 @@ class Region
 	PBD::Property<float>       _stretch;
 	PBD::Property<float>       _shift;
 	PBD::EnumProperty<PositionLockStyle> _position_lock_style;
+	PBD::Property<uint64_t>    _layering_index;
 
-	/* XXX: could use a Evoral::Range<> but I'm too lazy to make PBD::Property serialize such a thing nicely */
-	PBD::Property<framepos_t> _last_relayer_bounds_from; ///< from of our bounds last time relayer() was called
-	PBD::Property<framepos_t> _last_relayer_bounds_to; ///< to of our bounds last time relayer() was called
-	PBD::Property<uint64_t> _last_layer_op_add;
-	PBD::Property<uint64_t> _last_layer_op_bounds_change;
-	
 	framecnt_t              _last_length;
 	framepos_t              _last_position;
 	mutable RegionEditState _first_edit;
 	Timecode::BBT_Time      _bbt_time;
 
+	boost::optional<double> _pending_layer;
+
 	void register_properties ();
 
 	void use_sources (SourceList const &);
diff --git a/libs/ardour/ardour/region_sorters.h b/libs/ardour/ardour/region_sorters.h
index 0e3203ef20..baa3a3417d 100644
--- a/libs/ardour/ardour/region_sorters.h
+++ b/libs/ardour/ardour/region_sorters.h
@@ -36,22 +36,6 @@ struct RegionSortByLayer {
 	}
 };
 
-struct RegionSortByAdd {
-	bool operator() (boost::shared_ptr<Region> a, boost::shared_ptr<Region> b) {
-		return (
-			(a->last_layer_op (LayerOpAdd) < b->last_layer_op (LayerOpAdd))
-			);
-	}
-};
-
-struct RegionSortByAddOrBounds {
-	bool operator() (boost::shared_ptr<Region> a, boost::shared_ptr<Region> b) {
-		uint64_t const p = std::max (a->last_layer_op (LayerOpAdd), a->last_layer_op (LayerOpBoundsChange));
-		uint64_t const q = std::max (b->last_layer_op (LayerOpAdd), b->last_layer_op (LayerOpBoundsChange));
-		return p < q;
-	}
-};
-
 } // namespace
 
 #endif /* __libardour_region_sorters_h__ */
diff --git a/libs/ardour/ardour/session_configuration_vars.h b/libs/ardour/ardour/session_configuration_vars.h
index 57f390f100..87b317d3e8 100644
--- a/libs/ardour/ardour/session_configuration_vars.h
+++ b/libs/ardour/ardour/session_configuration_vars.h
@@ -47,8 +47,6 @@ CONFIG_VARIABLE_SPECIAL(std::string, audio_search_path, "audio-search-path", "",
 CONFIG_VARIABLE_SPECIAL(std::string, midi_search_path, "midi-search-path", "", search_path_expand)
 CONFIG_VARIABLE (std::string, bwf_country_code, "bwf-country-code", "US")
 CONFIG_VARIABLE (std::string, bwf_organization_code, "bwf-organization-code", "US")
-CONFIG_VARIABLE (LayerModel, layer_model, "layer-model", AddOrBoundsChangeHigher)
-CONFIG_VARIABLE (bool, relayer_on_all_edits, "relayer-on-all-edits", true)
 CONFIG_VARIABLE (std::string, auditioner_output_left, "auditioner-output-left", "default")
 CONFIG_VARIABLE (std::string, auditioner_output_right, "auditioner-output-right", "default")
 CONFIG_VARIABLE (bool, timecode_source_is_synced, "timecode-source-is-synced", true)
diff --git a/libs/ardour/ardour/types.h b/libs/ardour/ardour/types.h
index b5e5d89cc1..c2c7289329 100644
--- a/libs/ardour/ardour/types.h
+++ b/libs/ardour/ardour/types.h
@@ -409,12 +409,6 @@ namespace ARDOUR {
 		ShortCrossfade
 	};
 
-	enum LayerModel {
-		LaterHigher,
-		AddOrBoundsChangeHigher,
-		AddHigher
-	};
-
 	enum ListenPosition {
 		AfterFaderListen,
 		PreFaderListen
@@ -592,11 +586,6 @@ namespace ARDOUR {
 		FadeLogB
 	};
 
-	enum LayerOp {
-		LayerOpAdd,
-		LayerOpBoundsChange
-	};
-
 } // namespace ARDOUR
 
 
@@ -613,7 +602,6 @@ std::istream& operator>>(std::istream& o, ARDOUR::PFLPosition& sf);
 std::istream& operator>>(std::istream& o, ARDOUR::AFLPosition& sf);
 std::istream& operator>>(std::istream& o, ARDOUR::RemoteModel& sf);
 std::istream& operator>>(std::istream& o, ARDOUR::ListenPosition& sf);
-std::istream& operator>>(std::istream& o, ARDOUR::LayerModel& sf);
 std::istream& operator>>(std::istream& o, ARDOUR::InsertMergePolicy& sf);
 std::istream& operator>>(std::istream& o, ARDOUR::CrossfadeModel& sf);
 std::istream& operator>>(std::istream& o, ARDOUR::SyncSource& sf);
@@ -634,7 +622,6 @@ std::ostream& operator<<(std::ostream& o, const ARDOUR::PFLPosition& sf);
 std::ostream& operator<<(std::ostream& o, const ARDOUR::AFLPosition& sf);
 std::ostream& operator<<(std::ostream& o, const ARDOUR::RemoteModel& sf);
 std::ostream& operator<<(std::ostream& o, const ARDOUR::ListenPosition& sf);
-std::ostream& operator<<(std::ostream& o, const ARDOUR::LayerModel& sf);
 std::ostream& operator<<(std::ostream& o, const ARDOUR::InsertMergePolicy& sf);
 std::ostream& operator<<(std::ostream& o, const ARDOUR::CrossfadeModel& sf);
 std::ostream& operator<<(std::ostream& o, const ARDOUR::SyncSource& sf);
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index 83399d2962..9a227bf7a5 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -1510,6 +1510,8 @@ AudioDiskstream::transport_stopped_wallclock (struct tm& when, time_t twhen, boo
 			}
 
 			i_am_the_modifier++;
+
+			region->set_pending_layer (max_layer);
 			_playlist->add_region (region, (*ci)->start, 1, non_layered());
 			i_am_the_modifier--;
 
diff --git a/libs/ardour/enums.cc b/libs/ardour/enums.cc
index 12de366c79..fcf3b031ad 100644
--- a/libs/ardour/enums.cc
+++ b/libs/ardour/enums.cc
@@ -73,7 +73,6 @@ setup_enum_writer ()
 	RemoteModel _RemoteModel;
 	DenormalModel _DenormalModel;
 	CrossfadeModel _CrossfadeModel;
-	LayerModel _LayerModel;
 	InsertMergePolicy _InsertMergePolicy;
 	ListenPosition _ListenPosition;
 	SampleFormat _SampleFormat;
@@ -264,11 +263,6 @@ setup_enum_writer ()
 	REGISTER_ENUM (ShortCrossfade);
 	REGISTER (_CrossfadeModel);
 
-	REGISTER_ENUM (LaterHigher);
-	REGISTER_ENUM (AddOrBoundsChangeHigher);
-	REGISTER_ENUM (AddHigher);
-	REGISTER (_LayerModel);
-
         REGISTER_ENUM (InsertMergeReject);
         REGISTER_ENUM (InsertMergeRelax);
         REGISTER_ENUM (InsertMergeReplace);
@@ -711,19 +705,6 @@ std::ostream& operator<<(std::ostream& o, const ListenPosition& var)
 	std::string s = enum_2_string (var);
 	return o << s;
 }
-std::istream& operator>>(std::istream& o, LayerModel& var)
-{
-	std::string s;
-	o >> s;
-	var = (LayerModel) string_2_enum (s, var);
-	return o;
-}
-
-std::ostream& operator<<(std::ostream& o, const LayerModel& var)
-{
-	std::string s = enum_2_string (var);
-	return o << s;
-}
 
 std::istream& operator>>(std::istream& o, InsertMergePolicy& var)
 {
diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index a6925e444c..7ef59645d1 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -30,7 +30,6 @@
 
 #include "pbd/convert.h"
 #include "pbd/failed_constructor.h"
-#include "pbd/stacktrace.h"
 #include "pbd/stateful_diff_command.h"
 #include "pbd/xml++.h"
 
@@ -187,8 +186,6 @@ Playlist::Playlist (boost::shared_ptr<const Playlist> other, string namestr, boo
 	in_partition = false;
 	subcnt = 0;
 	_frozen = other->_frozen;
-
-	layer_op_counter = other->layer_op_counter;
 }
 
 Playlist::Playlist (boost::shared_ptr<const Playlist> other, framepos_t start, framecnt_t cnt, string str, bool hide)
@@ -256,6 +253,7 @@ Playlist::Playlist (boost::shared_ptr<const Playlist> other, framepos_t start, f
 		plist.add (Properties::length, len);
 		plist.add (Properties::name, new_name);
 		plist.add (Properties::layer, region->layer());
+		plist.add (Properties::layering_index, region->layering_index());
 
 		new_region = RegionFactory::RegionFactory::create (region, plist);
 
@@ -318,9 +316,7 @@ Playlist::init (bool hide)
 	in_partition = false;
 	subcnt = 0;
 	_frozen = false;
-	layer_op_counter = 0;
 	_combine_ops = 0;
-	_relayer_suspended = false;
 
 	_session.history().BeginUndoRedo.connect_same_thread (*this, boost::bind (&Playlist::begin_undo, this));
 	_session.history().EndUndoRedo.connect_same_thread (*this, boost::bind (&Playlist::end_undo, this));
@@ -485,8 +481,6 @@ Playlist::notify_region_moved (boost::shared_ptr<Region> r)
 {
 	Evoral::RangeMove<framepos_t> const move (r->last_position (), r->length (), r->position ());
 
-	/* We could timestamp the region's layer op here, but we're doing it in region_bounds_changed */
-
 	if (holding_state ()) {
 
 		pending_range_moves.push_back (move);
@@ -503,8 +497,6 @@ Playlist::notify_region_moved (boost::shared_ptr<Region> r)
 void
 Playlist::notify_region_start_trimmed (boost::shared_ptr<Region> r)
 {
-	timestamp_layer_op (LayerOpBoundsChange, r);
-
 	if (r->position() >= r->last_position()) {
 		/* trimmed shorter */
 		return;
@@ -528,8 +520,6 @@ Playlist::notify_region_start_trimmed (boost::shared_ptr<Region> r)
 void
 Playlist::notify_region_end_trimmed (boost::shared_ptr<Region> r)
 {
-	timestamp_layer_op (LayerOpBoundsChange, r);
-
 	if (r->length() < r->last_length()) {
 		/* trimmed shorter */
 	}
@@ -556,8 +546,6 @@ Playlist::notify_region_added (boost::shared_ptr<Region> r)
 	   as though it could be.
 	*/
 
-	timestamp_layer_op (LayerOpAdd, r);
-
 	if (holding_state()) {
 		pending_adds.insert (r);
 		pending_contents_change = true;
@@ -566,7 +554,6 @@ Playlist::notify_region_added (boost::shared_ptr<Region> r)
 		pending_contents_change = false;
 		RegionAdded (boost::weak_ptr<Region> (r)); /* EMIT SIGNAL */
 		ContentsChanged (); /* EMIT SIGNAL */
-		relayer (r);
 	}
 }
 
@@ -584,35 +571,31 @@ Playlist::flush_notifications (bool from_undo)
 
 	in_flush = true;
 
-	/* We have:
-
-	   pending_bounds:  regions whose bounds position and/or length changes
-	   pending_removes: regions which were removed
-	   pending_adds:    regions which were added
-	   pending_length:  true if the playlist length might have changed
-	   pending_contents_change: true if there was almost any change in the playlist
-	   pending_range_moves: details of periods of time that have been moved about (when regions have been moved)
-
-	*/
-
 	if (!pending_bounds.empty() || !pending_removes.empty() || !pending_adds.empty()) {
 		regions_changed = true;
 	}
 
-	/* Make a list of regions that need relayering */
-	RegionList regions_to_relayer;
+	/* we have no idea what order the regions ended up in pending
+	   bounds (it could be based on selection order, for example).
+	   so, to preserve layering in the "most recently moved is higher"
+	   model, sort them by existing layer, then timestamp them.
+	*/
+
+	// RegionSortByLayer cmp;
+	// pending_bounds.sort (cmp);
 
 	for (RegionList::iterator r = pending_bounds.begin(); r != pending_bounds.end(); ++r) {
-		regions_to_relayer.push_back (*r);
 		dependent_checks_needed.insert (*r);
 	}
 
 	for (s = pending_removes.begin(); s != pending_removes.end(); ++s) {
 		remove_dependents (*s);
+		// cerr << _name << " sends RegionRemoved\n";
 		RegionRemoved (boost::weak_ptr<Region> (*s)); /* EMIT SIGNAL */
 	}
 
 	for (s = pending_adds.begin(); s != pending_adds.end(); ++s) {
+		 // cerr << _name << " sends RegionAdded\n";
 		 /* don't emit RegionAdded signal until relayering is done,
 		    so that the region is fully setup by the time
 		    anyone hear's that its been added
@@ -621,14 +604,18 @@ Playlist::flush_notifications (bool from_undo)
 	 }
 
 	 if (regions_changed || pending_contents_change) {
+		 if (!in_set_state) {
+			 relayer ();
+		 }
 		 pending_contents_change = false;
+		 // cerr << _name << " sends 5 contents change @ " << get_microseconds() << endl;
 		 ContentsChanged (); /* EMIT SIGNAL */
+		 // cerr << _name << "done contents change @ " << get_microseconds() << endl;
 	 }
 
 	 for (s = pending_adds.begin(); s != pending_adds.end(); ++s) {
 		 (*s)->clear_changes ();
 		 RegionAdded (boost::weak_ptr<Region> (*s)); /* EMIT SIGNAL */
-		 regions_to_relayer.push_back (*s);
 	 }
 
 	 for (s = dependent_checks_needed.begin(); s != dependent_checks_needed.end(); ++s) {
@@ -643,14 +630,6 @@ Playlist::flush_notifications (bool from_undo)
 		 RegionsExtended (pending_region_extensions);
 	 }
 
-	 if (!regions_to_relayer.empty () && !from_undo) {
-		 relayer (regions_to_relayer);
-	 }
-
-	 if (pending_layering) {
-		 LayeringChanged (); /* EMIT SIGNAL */
-	 }
-
 	 clear_pending ();
 
 	 in_flush = false;
@@ -686,6 +665,7 @@ Playlist::flush_notifications (bool from_undo)
 	 }
 
 	 if (itimes >= 1) {
+		 region->set_pending_layer (DBL_MAX);
 		 add_region_internal (region, pos);
 		 pos += region->length();
 		 --itimes;
@@ -698,6 +678,7 @@ Playlist::flush_notifications (bool from_undo)
 
 	 for (int i = 0; i < itimes; ++i) {
 		 boost::shared_ptr<Region> copy = RegionFactory::create (region, true);
+		 copy->set_pending_layer (DBL_MAX);
 		 add_region_internal (copy, pos);
 		 pos += region->length();
 	 }
@@ -718,6 +699,7 @@ Playlist::flush_notifications (bool from_undo)
 			 plist.add (Properties::layer, region->layer());
 
 			 boost::shared_ptr<Region> sub = RegionFactory::create (region, plist);
+			 sub->set_pending_layer (DBL_MAX);
 			 add_region_internal (sub, pos);
 		 }
 	 }
@@ -758,6 +740,11 @@ Playlist::flush_notifications (bool from_undo)
 
 	 possibly_splice_unlocked (position, region->length(), region);
 
+	 if (!holding_state ()) {
+		 /* layers get assigned from XML state, and are not reset during undo/redo */
+		 relayer ();
+	 }
+
 	 /* we need to notify the existence of new region before checking dependents. Ick. */
 
 	 notify_region_added (region);
@@ -780,6 +767,7 @@ Playlist::flush_notifications (bool from_undo)
 	 _splicing = true;
 
 	 remove_region_internal (old);
+	 newr->set_pending_layer (newr->layer ());
 	 add_region_internal (newr, pos);
 
 	 _splicing = old_sp;
@@ -817,6 +805,7 @@ Playlist::flush_notifications (bool from_undo)
 			 possibly_splice_unlocked (pos, -distance);
 
 			 if (!holding_state ()) {
+				 relayer ();
 				 remove_dependents (region);
 			 }
 
@@ -873,16 +862,12 @@ Playlist::flush_notifications (bool from_undo)
  *  start and end if cutting == true.  Regions that lie entirely within start and end are always
  *  removed.
  */
+
  void
  Playlist::partition_internal (framepos_t start, framepos_t end, bool cutting, RegionList& thawlist)
  {
 	 RegionList new_regions;
 
-	 /* Don't relayer regions that are created during this operation; leave them
-	    on the same region as the original.
-	 */
-	 suspend_relayer ();
-
 	 {
 		 RegionLock rlock (this);
 
@@ -961,7 +946,8 @@ Playlist::flush_notifications (bool from_undo)
 					 plist.add (Properties::start, current->start() + (pos2 - pos1));
 					 plist.add (Properties::length, pos3 - pos2);
 					 plist.add (Properties::name, new_name);
-					 plist.add (Properties::layer, current->layer());
+					 plist.add (Properties::layer, current->layer ());
+					 plist.add (Properties::layering_index, current->layering_index ());
 					 plist.add (Properties::automatic, true);
 					 plist.add (Properties::left_of_split, true);
 					 plist.add (Properties::right_of_split, true);
@@ -980,7 +966,8 @@ Playlist::flush_notifications (bool from_undo)
 				 plist.add (Properties::start, current->start() + (pos3 - pos1));
 				 plist.add (Properties::length, pos4 - pos3);
 				 plist.add (Properties::name, new_name);
-				 plist.add (Properties::layer, current->layer());
+				 plist.add (Properties::layer, current->layer ());
+				 plist.add (Properties::layering_index, current->layering_index ());
 				 plist.add (Properties::automatic, true);
 				 plist.add (Properties::right_of_split, true);
 
@@ -1018,7 +1005,8 @@ Playlist::flush_notifications (bool from_undo)
 					 plist.add (Properties::start, current->start() + (pos2 - pos1));
 					 plist.add (Properties::length, pos4 - pos2);
 					 plist.add (Properties::name, new_name);
-					 plist.add (Properties::layer, current->layer());
+					 plist.add (Properties::layer, current->layer ());
+					 plist.add (Properties::layering_index, current->layering_index ());
 					 plist.add (Properties::automatic, true);
 					 plist.add (Properties::left_of_split, true);
 
@@ -1061,7 +1049,8 @@ Playlist::flush_notifications (bool from_undo)
 					 plist.add (Properties::start, current->start());
 					 plist.add (Properties::length, pos3 - pos1);
 					 plist.add (Properties::name, new_name);
-					 plist.add (Properties::layer, current->layer());
+					 plist.add (Properties::layer, current->layer ());
+					 plist.add (Properties::layering_index, current->layering_index ());
 					 plist.add (Properties::automatic, true);
 					 plist.add (Properties::right_of_split, true);
 
@@ -1108,8 +1097,6 @@ Playlist::flush_notifications (bool from_undo)
 	 for (RegionList::iterator i = new_regions.begin(); i != new_regions.end(); ++i) {
 		 check_dependents (*i, false);
 	 }
-
-	 resume_relayer ();
  }
 
  boost::shared_ptr<Playlist>
@@ -1210,7 +1197,7 @@ Playlist::flush_notifications (bool from_undo)
 		 int itimes = (int) floor (times);
 		 framepos_t pos = position;
 		 framecnt_t const shift = other->_get_extent().second;
-		 layer_t top_layer = regions.size();
+		 layer_t top = top_layer ();
 
 		 while (itimes--) {
 			 for (RegionList::iterator i = other->regions.begin(); i != other->regions.end(); ++i) {
@@ -1220,7 +1207,7 @@ Playlist::flush_notifications (bool from_undo)
 				    the ordering they had in the original playlist.
 				 */
 
-				 copy_of_region->set_layer (copy_of_region->layer() + top_layer);
+				 copy_of_region->set_pending_layer (copy_of_region->layer() + top);
 				 add_region_internal (copy_of_region, (*i)->position() + pos);
 			 }
 			 pos += shift;
@@ -1242,6 +1229,7 @@ Playlist::flush_notifications (bool from_undo)
 
 	 while (itimes--) {
 		 boost::shared_ptr<Region> copy = RegionFactory::create (region, true);
+		 copy->set_pending_layer (DBL_MAX);
 		 add_region_internal (copy, pos);
 		 pos += region->length();
 	 }
@@ -1259,6 +1247,7 @@ Playlist::flush_notifications (bool from_undo)
 			 plist.add (Properties::name, name);
 
 			 boost::shared_ptr<Region> sub = RegionFactory::create (region, plist);
+			 sub->set_pending_layer (DBL_MAX);
 			 add_region_internal (sub, pos);
 		 }
 	 }
@@ -1360,6 +1349,8 @@ Playlist::flush_notifications (bool from_undo)
 		 plist.add (Properties::length, before);
 		 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
@@ -1377,6 +1368,8 @@ Playlist::flush_notifications (bool from_undo)
 		 plist.add (Properties::length, after);
 		 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);
@@ -1470,8 +1463,6 @@ Playlist::flush_notifications (bool from_undo)
 
 	 if (what_changed.contains (Properties::position)) {
 
-		 timestamp_layer_op (LayerOpBoundsChange, region);
-		 
 		 /* remove it from the list then add it back in
 		    the right place again.
 		 */
@@ -1512,7 +1503,7 @@ Playlist::flush_notifications (bool from_undo)
 			 pending_bounds.push_back (region);
 		 } else {
 			 notify_contents_changed ();
-			 relayer (region);
+			 relayer ();
 			 check_dependents (region, false);
 		 }
 	 }
@@ -1572,9 +1563,9 @@ Playlist::flush_notifications (bool from_undo)
 		 notify_region_start_trimmed (region);
 	 }
 
-	 if (what_changed.contains (Properties::layer)) {
-		 notify_layering_changed ();
-	 }
+	 /* don't notify about layer changes, since we are the only object that can initiate
+	    them, and we notify in ::relayer()
+	 */
 
 	 if (what_changed.contains (our_interests)) {
 		 save = true;
@@ -2134,7 +2125,6 @@ Playlist::flush_notifications (bool from_undo)
 		 return -1;
 	 }
 
-	 suspend_relayer ();
 	 freeze ();
 
 	 plist = node.properties();
@@ -2196,7 +2186,7 @@ Playlist::flush_notifications (bool from_undo)
 			}
 
 			add_region (region, region->position(), 1.0);
-
+			
 			region->resume_property_changes ();
 
 		}
@@ -2217,7 +2207,6 @@ Playlist::flush_notifications (bool from_undo)
 		
 	thaw ();
 	notify_contents_changed ();
-	resume_relayer ();
 
 	in_set_state--;
 	first_set_state = false;
@@ -2345,277 +2334,189 @@ Playlist::set_edit_mode (EditMode mode)
 	_edit_mode = mode;
 }
 
-/** Relayer a region.  See the other relayer() methods for commentary. */
+struct RelayerSort {
+	bool operator () (boost::shared_ptr<Region> a, boost::shared_ptr<Region> b) {
+		return a->layering_index() < b->layering_index();
+	}
+};
+
 void
-Playlist::relayer (boost::shared_ptr<Region> region)
+Playlist::relayer ()
 {
-	if (_relayer_suspended) {
+	/* never compute layers when changing state for undo/redo or setting from XML */
+
+	if (in_update || in_set_state) {
 		return;
 	}
-	
-	RegionList r;
-	r.push_back (region);
-	relayer (r);
-}
 
-Playlist::TemporaryLayers
-Playlist::compute_temporary_layers (RegionList const & relayer_regions)
-{
-	TemporaryLayers temporary_layers;
-	OverlapCache cache (this);
+	bool changed = false;
 
-	for (RegionList::const_iterator i = relayer_regions.begin(); i != relayer_regions.end(); ++i) {
+	/* Build up a new list of regions on each layer, stored in a set of lists
+	   each of which represent some period of time on some layer.  The idea
+	   is to avoid having to search the entire region list to establish whether
+	   each region overlaps another */
 
-		DEBUG_TRACE (DEBUG::Layering, string_compose ("Compute temporary layer for %1\n", (*i)->name()));
-	
-		/* current_overlaps: regions that overlap *i now */
-		RegionList current_overlaps = cache.get ((*i)->bounds ());
-		current_overlaps.remove (*i);
+	/* how many pieces to divide this playlist's time up into */
+	int const divisions = 512;
 
-		DEBUG_TRACE (DEBUG::Layering, "Current overlaps:\n");
-		for (RegionList::iterator j = current_overlaps.begin(); j != current_overlaps.end(); ++j) {
-			DEBUG_TRACE (DEBUG::Layering, string_compose ("\t%1\n", (*j)->name()));
-		}
-		
-		/* overlaps_to_preserve: regions that overlap *i now, but which aren't being
-		   worked on during this relayer: these will have their relationship with
-		   *i preserved.
-		*/
-		RegionList overlaps_to_preserve;
+	/* find the start and end positions of the regions on this playlist */
+	framepos_t start = INT64_MAX;
+	framepos_t end = 0;
+	for (RegionList::const_iterator i = regions.begin(); i != regions.end(); ++i) {
+		start = min (start, (*i)->position());
+		end = max (end, (*i)->position() + (*i)->length());
+	}
 
-		/* overlaps_to_check: regions that overlap *i now, and must be checked to
-		   see if *i is still on the correct layer with respect to them (according
-		   to current layering rules).
-		*/
-		RegionList overlaps_to_check;
+	/* hence the size of each time division */
+	double const division_size = (end - start) / double (divisions);
 
-		if (_session.config.get_relayer_on_all_edits () || (*i)->last_layer_op (LayerOpAdd) > (*i)->last_layer_op (LayerOpBoundsChange)) {
-			/* We're configured to relayer on all edits, or this region has had
-			   no edit since it was added to the playlist, so we're relayering
-			   the whole lot; in this case there are no `overlaps_to_preserve'.
-			*/
-			overlaps_to_check = current_overlaps;
-		} else {
-			/* We're only relayering new overlaps; find them */
-			RegionList last_overlaps = cache.get ((*i)->last_relayer_bounds ());
-			last_overlaps.remove (*i);
-			for (RegionList::const_iterator j = current_overlaps.begin(); j != current_overlaps.end(); ++j) {
-				if (find (last_overlaps.begin(), last_overlaps.end(), *j) == last_overlaps.end()) {
-					/* This is a new overlap, which must be checked */
-					overlaps_to_check.push_back (*j);
-				} else {
-					/* This is an existing overlap, which must be preserved */
-					overlaps_to_preserve.push_back (*j);
-				}
-			}
-		}
+	vector<vector<RegionList> > layers;
+	layers.push_back (vector<RegionList> (divisions));
 
-		if (overlaps_to_check.empty ()) {
-			/* There are no overlaps to check, so just leave everything as it is */
-			continue;
-		}
+	RegionList copy = regions.rlist();
+	RegionList pending;
 
-		DEBUG_TRACE (DEBUG::Layering, "Overlaps to check:\n");
-		for (RegionList::iterator j = overlaps_to_check.begin(); j != overlaps_to_check.end(); ++j) {
-			DEBUG_TRACE (DEBUG::Layering, string_compose ("\t%1\n", (*j)->name()));
-		}
-		
-		/* Put *i on our overlaps_to_check_list */
-		overlaps_to_check.push_back (*i);
+	/* Remove regions with pending relayers */
+	for (RegionList::iterator i = copy.begin(); i != copy.end(); ) {
 
-		/* And sort it according to the current layer model */
-		switch (_session.config.get_layer_model()) {
-		case LaterHigher:
-			overlaps_to_check.sort (RegionSortByPosition ());
-			break;
-		case AddOrBoundsChangeHigher:
-			overlaps_to_check.sort (RegionSortByAddOrBounds ());
-			break;
-		case AddHigher:
-			overlaps_to_check.sort (RegionSortByAdd ());
-			break;
+		RegionList::iterator j = i;
+		++j;
+		
+		if ((*i)->pending_layer()) {
+			pending.push_back (*i);
+			copy.erase (i);
 		}
 
-		/* Now find *i in our overlaps_to_check list; within this list it will be in the
-		   right place wrt the current layering rules, so we can work out the layers of the
-		   nearest regions below and above.
-		*/
-		double previous_layer = -DBL_MAX;
-		double next_layer = DBL_MAX;
-		RegionList::const_iterator j = overlaps_to_check.begin();
-		while (*j != *i) {
-			previous_layer = temporary_layers.get (*j);
+		i = j;
+	}
+
+	/* Sort the remainder */
+	copy.sort (RelayerSort ());
+
+	/* Re-insert the pending layers in the right places */
+	for (RegionList::iterator i = pending.begin(); i != pending.end(); ++i) {
+		RegionList::iterator j = copy.begin();
+		while (j != copy.end ()) {
+			if ((*j)->pending_layer().get_value_or ((*j)->layer ()) > (*i)->pending_layer().get ()) {
+				break;
+			}
 			++j;
 		}
+		copy.insert (j, *i);
+	}
 
-		/* we must have found *i */
-		assert (j != overlaps_to_check.end ());
+	bool had_pending = false;
 
-		++j;
-		if (j != overlaps_to_check.end ()) {
-			next_layer = temporary_layers.get (*j);
-		}
+	for (RegionList::iterator i = copy.begin(); i != copy.end(); ++i) {
 
-		if (next_layer < previous_layer) {
-			/* If this happens, it means that it's impossible to put *i between overlaps_to_check
-			   in a way that satisfies the current layering rule.  So we'll punt and put *i
-			   above previous_layer.
-			*/
-			next_layer = DBL_MAX;
+		/* reset the pending layer for every region now that we're relayering */
+		if ((*i)->reset_pending_layer ()) {
+			had_pending = true;
 		}
 
-		/* Now we know where *i and overlaps_to_preserve should go: between previous_layer and
-		   next_layer.
+		/* find the time divisions that this region covers; if there are no regions on the list,
+		   division_size will equal 0 and in this case we'll just say that
+		   start_division = end_division = 0.
 		*/
-
-		DEBUG_TRACE (DEBUG::Layering, string_compose ("%1 and deps need to go between %2 and %3\n", (*i)->name(), previous_layer, next_layer));
-
-		/* Recurse into overlaps_to_preserve to find dependents */
-		RegionList recursed_overlaps_to_preserve;
-		
-		for (RegionList::const_iterator k = overlaps_to_preserve.begin(); k != overlaps_to_preserve.end(); ++k) {
-			recursed_overlaps_to_preserve.push_back (*k);
-			RegionList touched = recursive_regions_touched (*k, cache, *i);
-			for (RegionList::iterator m = touched.begin(); m != touched.end(); ++m) {
-				if (find (recursed_overlaps_to_preserve.begin(), recursed_overlaps_to_preserve.end(), *m) == recursed_overlaps_to_preserve.end()) {
-					recursed_overlaps_to_preserve.push_back (*m);
-				}
+		int start_division = 0;
+		int end_division = 0;
+
+		if (division_size > 0) {
+			start_division = floor ( ((*i)->position() - start) / division_size);
+			end_division = floor ( ((*i)->position() + (*i)->length() - start) / division_size );
+			if (end_division == divisions) {
+				end_division--;
 			}
 		}
 
-		/* Put *i into the overlaps_to_preserve list */
-		recursed_overlaps_to_preserve.push_back (*i);
+		assert (divisions == 0 || end_division < divisions);
 
-		/* Sort it by layer, so that we preserve layering */
-		recursed_overlaps_to_preserve.sort (SortByTemporaryLayer (temporary_layers));
-
-		/* Divide available space up into chunks so that we can relayer everything in that space */
-		double const space = (next_layer - previous_layer) / (recursed_overlaps_to_preserve.size() + 1);
-
-		/* And relayer */
-		int m = 1;
-		for (RegionList::const_iterator k = recursed_overlaps_to_preserve.begin(); k != recursed_overlaps_to_preserve.end(); ++k) {
-			temporary_layers.set (*k, previous_layer + space * m);
-			++m;
-		}
-	}
+		/* find the lowest layer that this region can go on */
+		size_t j = layers.size();
+		while (j > 0) {
+			/* try layer j - 1; it can go on if it overlaps no other region
+			   that is already on that layer
+			*/
 
-	return temporary_layers;
-}
+			bool overlap = false;
+			for (int k = start_division; k <= end_division; ++k) {
+				RegionList::iterator l = layers[j-1][k].begin ();
+				while (l != layers[j-1][k].end()) {
+					if ((*l)->overlap_equivalent (*i)) {
+						overlap = true;
+						break;
+					}
+					l++;
+				}
 
-/** Take a list of temporary layer indices and set up the layers of all regions
- *  based on them.
- */
-void
-Playlist::commit_temporary_layers (TemporaryLayers const & temporary_layers)
-{
-	/* Sort all the playlist's regions by layer, ascending */
-	RegionList all_regions = regions.rlist ();
-	all_regions.sort (SortByTemporaryLayer (temporary_layers));
+				if (overlap) {
+					break;
+				}
+			}
 
-	DEBUG_TRACE (DEBUG::Layering, "Commit layering:\n");
+			if (overlap) {
+				/* overlap, so we must use layer j */
+				break;
+			}
 
-	for (RegionList::iterator i = all_regions.begin(); i != all_regions.end(); ++i) {
+			--j;
+		}
 
-		/* Go through the regions that we have already layered and hence work
-		   out the maximum layer index that is in used at some point during
-		   region *i.
-		*/
-		
-		layer_t max_layer_here = 0;
-		bool have_overlap = false;
-		for (RegionList::iterator j = all_regions.begin(); j != i; ++j) {
-			if ((*j)->overlap_equivalent (*i)) {
-				max_layer_here = max ((*j)->layer (), max_layer_here);
-				have_overlap = true;
-			}
+		if (j == layers.size()) {
+			/* we need a new layer for this region */
+			layers.push_back (vector<RegionList> (divisions));
 		}
 
-		if (have_overlap) {
-			/* *i overlaps something, so put it on the next available layer */
-			(*i)->set_layer (max_layer_here + 1);
-		} else {
-			/* no overlap, so put on the bottom layer */
-			(*i)->set_layer (0);
+		/* put a reference to this region in each of the divisions that it exists in */
+		for (int k = start_division; k <= end_division; ++k) {
+			layers[j][k].push_back (*i);
 		}
-		
-		DEBUG_TRACE (DEBUG::Layering, string_compose ("\t%1 temporary %2 committed %3\n", (*i)->name(), temporary_layers.get (*i), (*i)->layer()));
-	}
-}
 
-/** Relayer a list of regions.
- *
- *  Taking each region R in turn, this method examines the regions O that overlap R in time.
- *  If the session configuration option "relayer-on-all-moves" is false, we reduce O so that
- *  it contains only those regions with which new overlaps have been formed since the last
- *  relayer.
- *
- *  We then change the layer of R and its indirect overlaps so that R meets the current
- *  Session layer model with respect to O.  See doc/layering.
- */
+		if ((*i)->layer() != j) {
+			changed = true;
+		}
 
-void
-Playlist::relayer (RegionList const & relayer_regions)
-{
-	if (_relayer_suspended) {
-		return;
+		(*i)->set_layer (j);
 	}
 
-	/* We do this in two parts: first; compute `temporary layer' indices for
-	   regions on the playlist.  These are (possibly) fractional indices, which
-	   are a convenient means of working with things when you want to insert layers
-	   between others.
-	*/
-
-	TemporaryLayers temporary_layers = compute_temporary_layers (relayer_regions);
-
-	/* Second, we fix up these temporary layers and `commit' them by writing
-	   them to the regions involved.
-	*/
-	
-	commit_temporary_layers (temporary_layers);
-}
-
-/** Put a region on some fractional layer and sort everything else out around it.
- *  This can be used to force a region into some layering; for example, calling
- *  this method with temporary_layer == -0.5 will put the region at the bottom of
- *  the stack.
- */
-
-void
-Playlist::relayer (boost::shared_ptr<Region> region, double temporary_layer)
-{
-	if (_relayer_suspended) {
-		return;
+	if (changed) {
+		notify_layering_changed ();
 	}
 
-	TemporaryLayers t;
-	t.set (region, temporary_layer);
-	commit_temporary_layers (t);
+	if (had_pending) {
+		uint64_t i = 0;
+		for (RegionList::iterator j = copy.begin(); j != copy.end(); ++j) {
+			(*j)->set_layering_index (i++);
+		}
+	}
 }
 
 void
 Playlist::raise_region (boost::shared_ptr<Region> region)
 {
-	relayer (region, region->layer() + 1.5);
+	region->set_pending_layer (region->layer() + 1.5);
+	relayer ();
 }
 
 void
 Playlist::lower_region (boost::shared_ptr<Region> region)
 {
-	relayer (region, region->layer() - 1.5);
+	region->set_pending_layer (region->layer() - 1.5);
+	relayer ();
 }
 
 void
 Playlist::raise_region_to_top (boost::shared_ptr<Region> region)
 {
-	relayer (region, max_layer);
+	region->set_pending_layer (DBL_MAX);
+	relayer ();
 }
 
 void
 Playlist::lower_region_to_bottom (boost::shared_ptr<Region> region)
 {
-	relayer (region, -0.5);
+	region->set_pending_layer (-0.5);
+	relayer ();
 }
 
 void
@@ -2751,23 +2652,8 @@ Playlist::set_frozen (bool yn)
 }
 
 void
-Playlist::timestamp_layer_op (LayerOp op, boost::shared_ptr<Region> region)
-{
-	region->set_last_layer_op (op, ++layer_op_counter);
-}
-
-
-/** Find the next or previous region after `region' (next if dir > 0, previous otherwise)
- *  and swap its position with `region'.
- */
-void
 Playlist::shuffle (boost::shared_ptr<Region> region, int dir)
 {
-	/* As regards layering, the calls we make to set_position() will
-	   perform layering as if the regions had been moved, which I think
-	   is about right.
-	*/
-	
 	bool moved = false;
 
 	if (region->locked()) {
@@ -2872,9 +2758,13 @@ Playlist::shuffle (boost::shared_ptr<Region> region, int dir)
 	_shuffling = false;
 
 	if (moved) {
+
+		relayer ();
 		check_dependents (region, false);
+
 		notify_contents_changed();
 	}
+
 }
 
 bool
@@ -3293,145 +3183,16 @@ Playlist::set_orig_track_id (const PBD::ID& id)
 	_orig_track_id = id;
 }
 
-/** Set the temporary layer for a region */
-void
-Playlist::TemporaryLayers::set (boost::shared_ptr<Region> r, double l)
-{
-	_map[r] = l;
-}
-
-/** Return the temporary layer for a region, if one has been specified
- *  to this TemporaryLayers object; if not return the region's current
- *  layer.
- */
-double
-Playlist::TemporaryLayers::get (boost::shared_ptr<Region> r) const
+uint64_t
+Playlist::highest_layering_index () const
 {
-	Map::const_iterator i = _map.find (r);
-	if (i != _map.end ()) {
-		return i->second;
-	}
-
-	return double (r->layer ());
-}
-
-int const Playlist::OverlapCache::_divisions = 512;
-
-/** Set up an OverlapCache for a playlist; the cache will only be valid until
- *  the Playlist is changed.
- */
-Playlist::OverlapCache::OverlapCache (Playlist* playlist)
-	: _range (0, 0)
-{
-	/* Find the start and end positions of the regions on this playlist */
-	_range = Evoral::Range<framepos_t> (max_framepos, 0);
-	RegionList const & rl = playlist->region_list().rlist ();
-	for (RegionList::const_iterator i = rl.begin(); i != rl.end(); ++i) {
-		Evoral::Range<framepos_t> const b = (*i)->bounds ();
-		_range.from = min (_range.from, b.from);
-		_range.to = max (_range.to, b.to);
-	}
-
-	/* Hence the size of each time divison */
-	_division_size = (_range.to - _range.from) / double (_divisions);
-
-	_cache.resize (_divisions);
-
-	/* Build the cache */
-	for (RegionList::const_iterator i = rl.begin(); i != rl.end(); ++i) {
-		pair<int, int> ind = cache_indices ((*i)->bounds ());
-		for (int j = ind.first; j < ind.second; ++j) {
-			_cache[j].push_back (*i);
-		}
-	}
-}
-
-/** @param range Range, in frames.
- *  @return From and to cache indices for  (to is exclusive).
- */
-pair<int, int>
-Playlist::OverlapCache::cache_indices (Evoral::Range<framepos_t> range) const
-{
-	range.from = max (range.from, _range.from);
-	range.to = min (range.to, _range.to);
-	
-	pair<int, int> const p = make_pair (
-		floor ((range.from - _range.from) / _division_size),
-		ceil ((range.to - _range.from) / _division_size)
-		);
-
-	assert (p.first >= 0);
-	assert (p.second <= _divisions);
-
-	return p;
-}
-
-/** Return the regions that overlap a given range.  The returned list
- *  is not guaranteed to be in the same order as the Playlist that it was
- *  generated from.
- */
-Playlist::RegionList
-Playlist::OverlapCache::get (Evoral::Range<framepos_t> range) const
-{
-	if (_range.from == max_framepos) {
-		return RegionList ();
-	}
-	
-	RegionList r;
+	RegionLock rlock (const_cast<Playlist *> (this));
 
-	pair<int, int> ind = cache_indices (range);
-	for (int i = ind.first; i < ind.second; ++i) {
-		for (RegionList::const_iterator j = _cache[i].begin(); j != _cache[i].end(); ++j) {
-			if ((*j)->coverage (range.from, range.to) != OverlapNone) {
-				r.push_back (*j);
-			}
-		}
+	uint64_t h = 0;
+	for (RegionList::const_iterator i = regions.begin(); i != regions.end(); ++i) {
+		h = max (h, (*i)->layering_index ());
 	}
 
-	r.sort ();
-	r.unique ();
-
-	return r;
-}
-
-void
-Playlist::suspend_relayer ()
-{
-	_relayer_suspended = true;
-}
-
-void
-Playlist::resume_relayer ()
-{
-	_relayer_suspended = false;
-}
-
-/** Examine a region and return regions which overlap it, and also those which overlap those which overlap etc.
- *  @param ignore Optional region which should be treated as if it doesn't exist (ie not returned in the list,
- *  and not recursed into).
- */
-Playlist::RegionList
-Playlist::recursive_regions_touched (boost::shared_ptr<Region> region, OverlapCache const & cache, boost::shared_ptr<Region> ignore) const
-{
-	RegionList touched;
-	recursive_regions_touched_sub (region, cache, ignore, touched);
-
-	touched.remove (region);
-	return touched;
-}
-
-/** Recursive sub-routine of recursive_regions_touched */
-void
-Playlist::recursive_regions_touched_sub (
-	boost::shared_ptr<Region> region, OverlapCache const & cache, boost::shared_ptr<Region> ignore, RegionList & touched
-	) const
-{
-	RegionList r = cache.get (region->bounds ());
-	for (RegionList::iterator i = r.begin(); i != r.end(); ++i) {
-		if (find (touched.begin(), touched.end(), *i) == touched.end() && *i != ignore) {
-			touched.push_back (*i);
-			recursive_regions_touched_sub (*i, cache, ignore, touched);
-		}
-	}
+	return h;
 }
 
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 89abdbd230..0ec8ee001b 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -73,10 +73,7 @@ namespace ARDOUR {
 		PBD::PropertyDescriptor<float> stretch;
 		PBD::PropertyDescriptor<float> shift;
 		PBD::PropertyDescriptor<PositionLockStyle> position_lock_style;
-		PBD::PropertyDescriptor<framepos_t> last_relayer_bounds_from;
-		PBD::PropertyDescriptor<framepos_t> last_relayer_bounds_to;
-		PBD::PropertyDescriptor<uint64_t> last_layer_op_add;
-		PBD::PropertyDescriptor<uint64_t> last_layer_op_bounds_change;
+		PBD::PropertyDescriptor<uint64_t> layering_index;
 	}
 }
 
@@ -131,14 +128,8 @@ Region::make_property_quarks ()
 	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for shift = %1\n", 	Properties::shift.property_id));
 	Properties::position_lock_style.property_id = g_quark_from_static_string (X_("positional-lock-style"));
 	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for position_lock_style = %1\n", 	Properties::position_lock_style.property_id));
-	Properties::last_relayer_bounds_from.property_id = g_quark_from_static_string (X_("last-relayer-bounds-from"));
-	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for last_relayer_bounds_from = %1\n", 	Properties::last_relayer_bounds_from.property_id));
-	Properties::last_relayer_bounds_to.property_id = g_quark_from_static_string (X_("last-relayer-bounds-to"));
-	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for last_relayer_bounds_to = %1\n", 	Properties::last_relayer_bounds_to.property_id));
-	Properties::last_layer_op_add.property_id = g_quark_from_static_string (X_("last-layer-op-add"));
-	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for last_layer_op_add = %1\n", Properties::last_layer_op_add.property_id));
-	Properties::last_layer_op_bounds_change.property_id = g_quark_from_static_string (X_("last-layer-op-bounds-change"));
-	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for last_layer_op_bounds_change = %1\n", Properties::last_layer_op_bounds_change.property_id));
+	Properties::layering_index.property_id = g_quark_from_static_string (X_("layering-index"));
+	DEBUG_TRACE (DEBUG::Properties, string_compose ("quark for layering_index = %1\n", 	Properties::layering_index.property_id));
 }
 
 void
@@ -169,10 +160,7 @@ Region::register_properties ()
 	add_property (_stretch);
 	add_property (_shift);
 	add_property (_position_lock_style);
-	add_property (_last_relayer_bounds_from);
-	add_property (_last_relayer_bounds_to);
-	add_property (_last_layer_op_add);
-	add_property (_last_layer_op_bounds_change);
+	add_property (_layering_index);
 }
 
 #define REGION_DEFAULT_STATE(s,l) \
@@ -199,10 +187,7 @@ Region::register_properties ()
 	, _stretch (Properties::stretch, 1.0) \
 	, _shift (Properties::shift, 1.0) \
 	, _position_lock_style (Properties::position_lock_style, _type == DataType::AUDIO ? AudioTime : MusicTime) \
-	, _last_relayer_bounds_from (Properties::last_relayer_bounds_from, 0) \
-	, _last_relayer_bounds_to (Properties::last_relayer_bounds_to, 0)	\
-	, _last_layer_op_add (Properties::last_layer_op_add, 0)	\
-	, _last_layer_op_bounds_change (Properties::last_layer_op_bounds_change, 0)
+	, _layering_index (Properties::layering_index, 0)
 
 #define REGION_COPY_STATE(other) \
 	  _sync_marked (Properties::sync_marked, other->_sync_marked) \
@@ -228,10 +213,7 @@ Region::register_properties ()
 	, _stretch (Properties::stretch, other->_stretch)	\
 	, _shift (Properties::shift, other->_shift)		\
 	, _position_lock_style (Properties::position_lock_style, other->_position_lock_style) \
-        , _last_relayer_bounds_from (Properties::last_relayer_bounds_from, other->_last_relayer_bounds_from) \
-        , _last_relayer_bounds_to (Properties::last_relayer_bounds_to, other->_last_relayer_bounds_to) \
-        , _last_layer_op_add (Properties::last_layer_op_add, other->_last_layer_op_add) \
-        , _last_layer_op_bounds_change (Properties::last_layer_op_bounds_change, other->_last_layer_op_bounds_change)
+	, _layering_index (Properties::layering_index, other->_layering_index)
 
 /* derived-from-derived constructor (no sources in constructor) */
 Region::Region (Session& s, framepos_t start, framecnt_t length, const string& name, DataType type)
@@ -243,6 +225,7 @@ Region::Region (Session& s, framepos_t start, framecnt_t length, const string& n
 	, _first_edit (EditChangesNothing)
 {
 	register_properties ();
+
 	/* no sources at this point */
 }
 
@@ -1134,12 +1117,9 @@ Region::set_layer (layer_t l)
 {
 	if (_layer != l) {
 		_layer = l;
+
 		send_change (Properties::layer);
 	}
-
-	Evoral::Range<framepos_t> const b = bounds ();
-	_last_relayer_bounds_from = b.from;
-	_last_relayer_bounds_to = b.to;
 }
 
 XMLNode&
@@ -1330,19 +1310,6 @@ Region::send_change (const PropertyChange& what_changed)
 	}
 }
 
-void
-Region::set_last_layer_op (LayerOp op, uint64_t when)
-{
-	switch (op) {
-	case LayerOpAdd:
-		_last_layer_op_add = when;
-		break;
-	case LayerOpBoundsChange:
-		_last_layer_op_bounds_change = when;
-		break;
-	}
-}
-
 bool
 Region::overlap_equivalent (boost::shared_ptr<const Region> other) const
 {
@@ -1683,24 +1650,22 @@ Region::post_set (const PropertyChange& pc)
 	}
 }
 
-uint64_t
-Region::last_layer_op (LayerOp op) const
+void
+Region::set_pending_layer (double l)
 {
-	switch (op) {
-	case LayerOpAdd:
-		return _last_layer_op_add;
-	case LayerOpBoundsChange:
-		return _last_layer_op_bounds_change;
-	}
-
-	/* NOTREACHED */
-	return 0;
+	_pending_layer = l;
 }
 
-Evoral::Range<framepos_t>
-Region::bounds () const
+bool
+Region::reset_pending_layer ()
 {
-	return Evoral::Range<framepos_t> (_position, _position + _length);
+	bool const had = _pending_layer;
+	_pending_layer = boost::optional<double> ();
+	return had;
 }
 
-       
+boost::optional<double>
+Region::pending_layer () const
+{
+	return _pending_layer;
+}
diff --git a/libs/ardour/run-tests.sh b/libs/ardour/run-tests.sh
index 76fc4f8aea..379678c968 100755
--- a/libs/ardour/run-tests.sh
+++ b/libs/ardour/run-tests.sh
@@ -19,8 +19,6 @@ export ARDOUR_PANNER_PATH=$libs/panners/2in2out:$libs/panners/1in2out:$libs/pann
 
 if [ "$1" == "--debug" ]; then
         gdb ./libs/ardour/run-tests
-elif [ "$1" == "--valgrind" ]; then
-        valgrind --tool="memcheck" ./libs/ardour/run-tests
 else
         ./libs/ardour/run-tests
 fi
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 532d010680..7d6f44b786 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -974,27 +974,7 @@ int
 Session::load_options (const XMLNode& node)
 {
 	LocaleGuard lg (X_("POSIX"));
-
-	/* Copy the node */
-	XMLNode node_copy = node;
-	
-	/* XXX: evil hack: fix up sessions from before the layering alterations
-	   (during A3 beta)
-	*/
-	
-	XMLNodeList children = node_copy.children ();
-	for (XMLNodeIterator i = children.begin(); i != children.end(); ++i) {
-		XMLProperty* p = (*i)->property (X_("name"));
-		if (p && p->name() == X_("name") && p->value() == X_("layer-model") ) {
-			p = (*i)->property (X_("value"));
-			if (p && p->value() == X_("MoveAddHigher")) {
-				(*i)->add_property (X_("value"), X_("AddOrBoundsChangeHigher"));
-			}
-		}
-	}
-	
-	config.set_variables (node_copy);
-	
+	config.set_variables (node);
 	return 0;
 }
 
diff --git a/libs/ardour/test/playlist_layering_test.cc b/libs/ardour/test/playlist_layering_test.cc
index 23b22f9d90..fd0b6bc09c 100644
--- a/libs/ardour/test/playlist_layering_test.cc
+++ b/libs/ardour/test/playlist_layering_test.cc
@@ -1,14 +1,13 @@
-#include "pbd/compose.h"
 #include "midi++/manager.h"
+#include "pbd/textreceiver.h"
+#include "pbd/compose.h"
+#include "ardour/session.h"
+#include "ardour/audioengine.h"
 #include "ardour/playlist_factory.h"
 #include "ardour/source_factory.h"
 #include "ardour/region.h"
 #include "ardour/region_factory.h"
-#include "ardour/session.h"
-#include "ardour/audiosource.h"
-#include "ardour/audioengine.h"
 #include "playlist_layering_test.h"
-#include "test_receiver.h"
 
 CPPUNIT_TEST_SUITE_REGISTRATION (PlaylistLayeringTest);
 
@@ -16,28 +15,68 @@ using namespace std;
 using namespace ARDOUR;
 using namespace PBD;
 
-int const PlaylistLayeringTest::num_regions = 6;
+class TestReceiver : public Receiver 
+{
+protected:
+	void receive (Transmitter::Channel chn, const char * str) {
+		const char *prefix = "";
+		
+		switch (chn) {
+		case Transmitter::Error:
+			prefix = ": [ERROR]: ";
+			break;
+		case Transmitter::Info:
+			/* ignore */
+			return;
+		case Transmitter::Warning:
+			prefix = ": [WARNING]: ";
+			break;
+		case Transmitter::Fatal:
+			prefix = ": [FATAL]: ";
+			break;
+		case Transmitter::Throw:
+			/* this isn't supposed to happen */
+			abort ();
+		}
+		
+		/* note: iostreams are already thread-safe: no external
+		   lock required.
+		*/
+		
+		cout << prefix << str << endl;
+		
+		if (chn == Transmitter::Fatal) {
+			exit (9);
+		}
+	}
+};
+
+TestReceiver test_receiver;
 
 void
 PlaylistLayeringTest::setUp ()
 {
-	TestNeedingSession::setUp ();
-	string const test_wav_path = "libs/ardour/test/test.wav";
+	string const test_session_path = "libs/ardour/test/playlist_layering_test";
+	string const test_wav_path = "libs/ardour/test/playlist_layering_test/playlist_layering_test.wav";
+	system (string_compose ("rm -rf %1", test_session_path).c_str());
 	
-	_playlist = PlaylistFactory::create (DataType::AUDIO, *_session, "test");
-	_source = SourceFactory::createWritable (DataType::AUDIO, *_session, test_wav_path, "", false, 44100);
+	init (false, true);
+	SessionEvent::create_per_thread_pool ("test", 512);
 
-	system ("pwd");
-	
-	/* Must write some data to our source, otherwise regions which use it will
-	   be limited in whether they can be trimmed or not.
-	*/
-	boost::shared_ptr<AudioSource> a = boost::dynamic_pointer_cast<AudioSource> (_source);
-	Sample silence[512];
-	memset (silence, 0, 512 * sizeof (Sample));
-	a->write (silence, 512);
+	test_receiver.listen_to (error);
+	test_receiver.listen_to (info);
+	test_receiver.listen_to (fatal);
+	test_receiver.listen_to (warning);
+
+	AudioEngine* engine = new AudioEngine ("test", "");
+	MIDI::Manager::create (engine->jack ());
+	CPPUNIT_ASSERT (engine->start () == 0);
 
-	_region = new boost::shared_ptr<Region>[num_regions];
+	_session = new Session (*engine, test_session_path, "playlist_layering_test");
+	engine->set_session (_session);
+
+	_playlist = PlaylistFactory::create (DataType::AUDIO, *_session, "test");
+	_source = SourceFactory::createWritable (DataType::AUDIO, *_session, test_wav_path, "", false, 44100);
 }
 
 void
@@ -45,303 +84,45 @@ PlaylistLayeringTest::tearDown ()
 {
 	_playlist.reset ();
 	_source.reset ();
-	for (int i = 0; i < num_regions; ++i) {
+	for (int i = 0; i < 16; ++i) {
 		_region[i].reset ();
 	}
 	
-	delete[] _region;
-	
-	TestNeedingSession::tearDown ();
+	AudioEngine::instance()->remove_session ();
+	delete _session;
+	EnumWriter::destroy ();
+	MIDI::Manager::destroy ();
+	AudioEngine::destroy ();
 }
 
 void
-PlaylistLayeringTest::create_short_regions ()
+PlaylistLayeringTest::create_three_short_regions ()
 {
 	PropertyList plist;
 	plist.add (Properties::start, 0);
 	plist.add (Properties::length, 100);
-	for (int i = 0; i < num_regions; ++i) {
+	for (int i = 0; i < 3; ++i) {
 		_region[i] = RegionFactory::create (_source, plist);
-		_region[i]->set_name (string_compose ("%1", char (int ('A') + i)));
 	}
 }
 
 void
-PlaylistLayeringTest::laterHigher_relayerOnAll_Test ()
-{
-	_session->config.set_layer_model (LaterHigher);
-	_session->config.set_relayer_on_all_edits (true);
-	
-	create_short_regions ();
-
-	/* three overlapping regions */
-	_playlist->add_region (_region[A], 0);
-	_playlist->add_region (_region[B], 10);
-	_playlist->add_region (_region[C], 20);
-	/* and another non-overlapping one */
-	_playlist->add_region (_region[D], 200);
-
-	/* LaterHigher means that they should be arranged thus */
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	_region[A]->set_position (5);
-
-	/* Region move should have no effect in LaterHigher mode */
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> bottom should give C A B, not touching D */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> top should go back to A B C, not touching D */
-	_region[C]->raise_to_top ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-}
-
-void
-PlaylistLayeringTest::addHigher_relayerOnAll_Test ()
-{
-	_session->config.set_layer_model (AddHigher);
-	_session->config.set_relayer_on_all_edits (true);
-	
-	create_short_regions ();
-
-	/* three overlapping regions */
-	_playlist->add_region (_region[A], 0);
-	_playlist->add_region (_region[B], 10);
-	_playlist->add_region (_region[C], 20);
-	/* and another non-overlapping one */
-	_playlist->add_region (_region[D], 200);
-
-	/* AddHigher means that they should be arranged thus */
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	_region[A]->set_position (5);
-
-	/* region move should have no effect in AddHigher mode */
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> bottom should give C A B, not touching D */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> top should go back to A B C, not touching D */
-	_region[C]->raise_to_top ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-}
-
-void
-PlaylistLayeringTest::addOrBoundsHigher_relayerOnAll_Test ()
+PlaylistLayeringTest::basicsTest ()
 {
-	_session->config.set_layer_model (AddOrBoundsChangeHigher);
-	_session->config.set_relayer_on_all_edits (true);
-	
-	create_short_regions ();
-
-	/* three overlapping regions */
-	_playlist->add_region (_region[A], 0);
-	_playlist->add_region (_region[B], 10);
-	_playlist->add_region (_region[C], 20);
-	/* and another non-overlapping one */
-	_playlist->add_region (_region[D], 200);
-
-	/* AddOrBoundsHigher means that they should be arranged thus */
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* region move should put A on top for B C A, not touching D */
-	_region[A]->set_position (5);
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> bottom should give C B A, not touching D */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> top should go back to B A C, not touching D */
-	_region[C]->raise_to_top ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* Put C on the bottom */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* Now move it slightly, and it should go back to the top again */
-	_region[C]->set_position (21);
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* Put C back on the bottom */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* Trim it slightly, and it should go back to the top again */
-	_region[C]->trim_front (23);
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* Same with the end */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	_region[C]->trim_end (118);
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-}
-
-void
-PlaylistLayeringTest::addOrBoundsHigher_relayerWhenNecessary_Test ()
-{
-	_session->config.set_layer_model (AddOrBoundsChangeHigher);
-	_session->config.set_relayer_on_all_edits (false);
-	
-	create_short_regions ();
-
-	/* three overlapping regions */
-	_playlist->add_region (_region[A], 0);
-	_playlist->add_region (_region[B], 10);
-	_playlist->add_region (_region[C], 20);
-	/* and another non-overlapping one */
-	_playlist->add_region (_region[D], 200);
-
-	/* AddOrBoundsHigher means that they should be arranged thus */
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	_region[A]->set_position (5);
-
-	/* region move should not have changed anything, since in
-	   this mode we only relayer when there is a new overlap
-	*/
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> bottom should give C A B, not touching D */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* C -> top should go back to A B C, not touching D */
-	_region[C]->raise_to_top ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-
-	/* Put C on the bottom */
-	_region[C]->lower_to_bottom ();
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-	
-	/* Now move it slightly, and it should stay where it is */
-	_region[C]->set_position (21);
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-}
-
-void
-PlaylistLayeringTest::lastLayerOpTest ()
-{
-	create_short_regions ();
-
-	_playlist->add_region (_region[A], 0);
-	CPPUNIT_ASSERT_EQUAL (_playlist->layer_op_counter, _region[A]->last_layer_op (LayerOpAdd));
-	uint64_t const last_add = _region[A]->last_layer_op (LayerOpAdd);
-	
-	_region[A]->set_position (42);
-	CPPUNIT_ASSERT_EQUAL (_playlist->layer_op_counter, _region[A]->last_layer_op (LayerOpBoundsChange));
-	CPPUNIT_ASSERT_EQUAL (last_add, _region[A]->last_layer_op (LayerOpAdd));
-
-	_region[A]->trim_front (46);
-	CPPUNIT_ASSERT_EQUAL (_playlist->layer_op_counter, _region[A]->last_layer_op (LayerOpBoundsChange));
-	CPPUNIT_ASSERT_EQUAL (last_add, _region[A]->last_layer_op (LayerOpAdd));
-
-	_region[A]->trim_end (102);
-	CPPUNIT_ASSERT_EQUAL (_playlist->layer_op_counter, _region[A]->last_layer_op (LayerOpBoundsChange));
-	CPPUNIT_ASSERT_EQUAL (last_add, _region[A]->last_layer_op (LayerOpAdd));
-}
-
-void
-PlaylistLayeringTest::recursiveRelayerTest ()
-{
-	_session->config.set_layer_model (AddOrBoundsChangeHigher);
-	_session->config.set_relayer_on_all_edits (false);
-	
-	create_short_regions ();
+	create_three_short_regions ();
 
-	_playlist->add_region (_region[A], 100);
-	_playlist->add_region (_region[B], 125);
-	_playlist->add_region (_region[C], 50);
-	_playlist->add_region (_region[D], 250);
+	_playlist->add_region (_region[0], 0);
+	_playlist->add_region (_region[1], 10);
+	_playlist->add_region (_region[2], 20);
 
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[C]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
+	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[0]->layer ());
+	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[1]->layer ());
+	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[2]->layer ());
 
-	_region[A]->set_position (200);
+	_region[0]->set_position (5);
 
-	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[D]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[A]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[B]->layer ());
-	CPPUNIT_ASSERT_EQUAL (layer_t (3), _region[C]->layer ());
+	/* region move should have no effect */
+	CPPUNIT_ASSERT_EQUAL (layer_t (0), _region[0]->layer ());
+	CPPUNIT_ASSERT_EQUAL (layer_t (1), _region[1]->layer ());
+	CPPUNIT_ASSERT_EQUAL (layer_t (2), _region[2]->layer ());
 }
diff --git a/libs/ardour/test/playlist_layering_test.h b/libs/ardour/test/playlist_layering_test.h
index ab5fe701b1..46285459ca 100644
--- a/libs/ardour/test/playlist_layering_test.h
+++ b/libs/ardour/test/playlist_layering_test.h
@@ -1,6 +1,5 @@
 #include <cppunit/TestFixture.h>
 #include <cppunit/extensions/HelperMacros.h>
-#include "test_needing_session.h"
 
 namespace ARDOUR {
 	class Session;
@@ -8,42 +7,23 @@ namespace ARDOUR {
 	class Source;
 }
 
-class PlaylistLayeringTest : public TestNeedingSession
+class PlaylistLayeringTest : public CppUnit::TestFixture
 {
 	CPPUNIT_TEST_SUITE (PlaylistLayeringTest);
-	CPPUNIT_TEST (lastLayerOpTest);
-	CPPUNIT_TEST (addHigher_relayerOnAll_Test);
-	CPPUNIT_TEST (addOrBoundsHigher_relayerOnAll_Test);
-	CPPUNIT_TEST (laterHigher_relayerOnAll_Test);
-	CPPUNIT_TEST (addOrBoundsHigher_relayerWhenNecessary_Test);
-	CPPUNIT_TEST (recursiveRelayerTest);
+	CPPUNIT_TEST (basicsTest);
 	CPPUNIT_TEST_SUITE_END ();
 
 public:
 	void setUp ();
 	void tearDown ();
 
-	void lastLayerOpTest ();
-	void addHigher_relayerOnAll_Test ();
-	void addOrBoundsHigher_relayerOnAll_Test ();
-	void laterHigher_relayerOnAll_Test ();
-	void addOrBoundsHigher_relayerWhenNecessary_Test ();
-	void recursiveRelayerTest ();
+	void basicsTest ();
 
 private:
-	void create_short_regions ();
-	
-	static int const num_regions;
-	enum {
-		A = 0,
-		B,
-		C,
-		D,
-		E,
-		F
-	};
+	void create_three_short_regions ();
 	
+	ARDOUR::Session* _session;
 	boost::shared_ptr<ARDOUR::Playlist> _playlist;
 	boost::shared_ptr<ARDOUR::Source> _source;
-	boost::shared_ptr<ARDOUR::Region>* _region;
+	boost::shared_ptr<ARDOUR::Region> _region[16];
 };
diff --git a/libs/ardour/test/playlist_overlap_cache_test.cc b/libs/ardour/test/playlist_overlap_cache_test.cc
deleted file mode 100644
index 9263d80d3b..0000000000
--- a/libs/ardour/test/playlist_overlap_cache_test.cc
+++ /dev/null
@@ -1,119 +0,0 @@
-#include "pbd/compose.h"
-#include "ardour/playlist.h"
-#include "ardour/playlist_factory.h"
-#include "ardour/source_factory.h"
-#include "ardour/region.h"
-#include "ardour/region_sorters.h"
-#include "ardour/region_factory.h"
-#include "playlist_overlap_cache_test.h"
-
-using namespace std;
-using namespace PBD;
-using namespace ARDOUR;
-
-CPPUNIT_TEST_SUITE_REGISTRATION (PlaylistOverlapCacheTest);
-
-void
-PlaylistOverlapCacheTest::tearDown ()
-{
-	_playlist.reset ();
-	_source.reset ();
-
-	TestNeedingSession::tearDown ();
-}
-
-void
-PlaylistOverlapCacheTest::basicTest ()
-{
-	string const test_wav_path = "libs/ardour/test/test.wav";
-	
-	_playlist = PlaylistFactory::create (DataType::AUDIO, *_session, "test");
-	_source = SourceFactory::createWritable (DataType::AUDIO, *_session, test_wav_path, "", false, 44100);
-
-	PropertyList plist;
-	plist.add (Properties::length, 256);
-	
-	boost::shared_ptr<Region> regionA = RegionFactory::create (_source, plist);
-	regionA->set_name ("A");
-	_playlist->add_region (regionA, 0);
-	
-
-	{
-		Playlist::OverlapCache cache (_playlist.get ());
-		Playlist::RegionList rl = cache.get (Evoral::Range<framepos_t> (0, 256));
-		CPPUNIT_ASSERT_EQUAL (size_t (1), rl.size ());
-		CPPUNIT_ASSERT_EQUAL (regionA, rl.front ());
-		
-		rl = cache.get (Evoral::Range<framepos_t> (-1000, 1000));
-		CPPUNIT_ASSERT_EQUAL (size_t (1), rl.size ());
-		CPPUNIT_ASSERT_EQUAL (regionA, rl.front ());
-	}
-
-	boost::shared_ptr<Region> regionB = RegionFactory::create (_source, plist);
-	regionA->set_name ("B");
-	_playlist->add_region (regionB, 53);
-
-	{
-		Playlist::OverlapCache cache (_playlist.get ());
-		Playlist::RegionList rl = cache.get (Evoral::Range<framepos_t> (0, 256));
-		CPPUNIT_ASSERT_EQUAL (size_t (2), rl.size ());
-		rl.sort (RegionSortByPosition ());
-		CPPUNIT_ASSERT_EQUAL (regionA, rl.front ());
-		CPPUNIT_ASSERT_EQUAL (regionB, rl.back ());
-
-		rl = cache.get (Evoral::Range<framepos_t> (260, 274));
-		CPPUNIT_ASSERT_EQUAL (size_t (1), rl.size ());
-		CPPUNIT_ASSERT_EQUAL (regionB, rl.front ());
-	}
-}
-
-void
-PlaylistOverlapCacheTest::stressTest ()
-{
-	string const test_wav_path = "libs/ardour/test/test.wav";
-
-	_playlist = PlaylistFactory::create (DataType::AUDIO, *_session, "test");
-	_source = SourceFactory::createWritable (DataType::AUDIO, *_session, test_wav_path, "", false, 44100);
-
-	srand (42);
-
-	int const num_regions = rand () % 256;
-
-	for (int i = 0; i < num_regions; ++i) {
-		PropertyList plist;
-		plist.add (Properties::length, rand () % 32768);
-		boost::shared_ptr<Region> r = RegionFactory::create (_source, plist);
-		r->set_name (string_compose ("%1", i));
-		_playlist->add_region (r, rand() % 32768);
-	}
-
-	Playlist::OverlapCache cache (_playlist.get ());
-
-	int const tests = rand () % 256;
-
-	for (int i = 0; i < tests; ++i) {
-		framepos_t const start = rand () % 32768;
-		framepos_t const length = rand () % 32768;
-		framepos_t const end = start + length;
-
-		Playlist::RegionList cached = cache.get (Evoral::Range<framepos_t> (start, end));
-
-		Playlist::RegionList actual;
-		Playlist::RegionList regions = _playlist->region_list().rlist();
-		for (Playlist::RegionList::iterator j = regions.begin(); j != regions.end(); ++j) {
-			if ((*j)->coverage (start, end) != OverlapNone) {
-				actual.push_back (*j);
-			}
-		}
-
-		cached.sort (RegionSortByPosition ());
-		actual.sort (RegionSortByPosition ());
-
-		CPPUNIT_ASSERT_EQUAL (actual.size (), cached.size ());
-		Playlist::RegionList::iterator j = actual.begin ();
-		Playlist::RegionList::iterator k = cached.begin ();
-		for (; j != actual.end(); ++j, ++k) {
-			CPPUNIT_ASSERT_EQUAL (*j, *k);
-		}
-	}
-}
diff --git a/libs/ardour/test/playlist_overlap_cache_test.h b/libs/ardour/test/playlist_overlap_cache_test.h
deleted file mode 100644
index c75d1691d9..0000000000
--- a/libs/ardour/test/playlist_overlap_cache_test.h
+++ /dev/null
@@ -1,20 +0,0 @@
-#include "test_needing_session.h"
-
-class PlaylistOverlapCacheTest : public TestNeedingSession
-{
-public:
-	CPPUNIT_TEST_SUITE (PlaylistOverlapCacheTest);
-	CPPUNIT_TEST (basicTest);
-	CPPUNIT_TEST (stressTest);
-	CPPUNIT_TEST_SUITE_END ();
-
-public:
-	void tearDown ();
-	
-	void basicTest ();
-	void stressTest ();
-
-private:
-	boost::shared_ptr<ARDOUR::Playlist> _playlist;
-	boost::shared_ptr<ARDOUR::Source> _source;
-};
diff --git a/libs/ardour/test/test_needing_session.cc b/libs/ardour/test/test_needing_session.cc
deleted file mode 100644
index 5981553601..0000000000
--- a/libs/ardour/test/test_needing_session.cc
+++ /dev/null
@@ -1,48 +0,0 @@
-#include "midi++/manager.h"
-#include "pbd/textreceiver.h"
-#include "pbd/compose.h"
-#include "pbd/enumwriter.h"
-#include "ardour/session.h"
-#include "ardour/audioengine.h"
-#include "test_needing_session.h"
-#include "test_receiver.h"
-
-using namespace std;
-using namespace ARDOUR;
-using namespace PBD;
-
-TestReceiver test_receiver;
-
-void
-TestNeedingSession::setUp ()
-{
-	string const test_session_path = "libs/ardour/test/test_session";
-	system (string_compose ("rm -rf %1", test_session_path).c_str());
-	
-	init (false, true);
-	SessionEvent::create_per_thread_pool ("test", 512);
-
-	test_receiver.listen_to (error);
-	test_receiver.listen_to (info);
-	test_receiver.listen_to (fatal);
-	test_receiver.listen_to (warning);
-
-	AudioEngine* engine = new AudioEngine ("test", "");
-	MIDI::Manager::create (engine->jack ());
-	CPPUNIT_ASSERT (engine->start () == 0);
-
-	_session = new Session (*engine, test_session_path, "test_session");
-	engine->set_session (_session);
-}
-
-void
-TestNeedingSession::tearDown ()
-{
-	AudioEngine::instance()->remove_session ();
-	
-	delete _session;
-
-	EnumWriter::destroy ();
-	MIDI::Manager::destroy ();
-	AudioEngine::destroy ();
-}
diff --git a/libs/ardour/test/test_needing_session.h b/libs/ardour/test/test_needing_session.h
deleted file mode 100644
index 3839855179..0000000000
--- a/libs/ardour/test/test_needing_session.h
+++ /dev/null
@@ -1,16 +0,0 @@
-#include <cppunit/TestFixture.h>
-#include <cppunit/extensions/HelperMacros.h>
-
-namespace ARDOUR {
-	class Session;
-}
-
-class TestNeedingSession : public CppUnit::TestFixture
-{
-public:
-	void setUp ();
-	void tearDown ();
-
-protected:
-	ARDOUR::Session* _session;
-};
diff --git a/libs/ardour/test/test_receiver.h b/libs/ardour/test/test_receiver.h
deleted file mode 100644
index 537bac3cff..0000000000
--- a/libs/ardour/test/test_receiver.h
+++ /dev/null
@@ -1,37 +0,0 @@
-#include "pbd/receiver.h"
-
-class TestReceiver : public Receiver 
-{
-protected:
-	void receive (Transmitter::Channel chn, const char * str) {
-		const char *prefix = "";
-		
-		switch (chn) {
-		case Transmitter::Error:
-			prefix = ": [ERROR]: ";
-			break;
-		case Transmitter::Info:
-			/* ignore */
-			return;
-		case Transmitter::Warning:
-			prefix = ": [WARNING]: ";
-			break;
-		case Transmitter::Fatal:
-			prefix = ": [FATAL]: ";
-			break;
-		case Transmitter::Throw:
-			/* this isn't supposed to happen */
-			abort ();
-		}
-		
-		/* note: iostreams are already thread-safe: no external
-		   lock required.
-		*/
-		
-		std::cout << prefix << str << std::endl;
-		
-		if (chn == Transmitter::Fatal) {
-			exit (9);
-		}
-	}
-};
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index e49be33b8c..42c72784f9 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -431,8 +431,6 @@ def build(bld):
                 test/framepos_plus_beats_test.cc
                 test/framepos_minus_beats_test.cc
                 test/playlist_layering_test.cc
-                test/playlist_overlap_cache_test.cc
-                test/test_needing_session.cc
                 test/testrunner.cc
         '''.split()