(1) remove most uses of MementoCommand for Playlist and Region (2) move frozen state from Region into Stateful, renamed "suspend property changes" (3) successive changes to a Property (scalar) after clear_history() do not keep resetting the old value (fixes region trim)

git-svn-id: svn://localhost/ardour2/branches/3.0@6720 d708f5d6-7413-0410-9779-e7cbd77b26cf

16 files changed, 71 insertions, 129 deletions

diff --git a/libs/ardour/ardour/audio_track.h b/libs/ardour/ardour/audio_track.h
index fc5b4255b3..be8d988a41 100644
--- a/libs/ardour/ardour/audio_track.h
+++ b/libs/ardour/ardour/audio_track.h
@@ -49,7 +49,7 @@ class AudioTrack : public Track
 
 	int export_stuff (BufferSet& bufs, sframes_t start_frame, nframes_t nframes, bool enable_processing = true);
 
-	void freeze (InterThreadInfo&);
+	void freeze_me (InterThreadInfo&);
 	void unfreeze ();
 
 	boost::shared_ptr<Region> bounce (InterThreadInfo&);
diff --git a/libs/ardour/ardour/automation_list.h b/libs/ardour/ardour/automation_list.h
index 1778771c5f..79acedebf3 100644
--- a/libs/ardour/ardour/automation_list.h
+++ b/libs/ardour/ardour/automation_list.h
@@ -50,7 +50,6 @@ class AutomationList : public PBD::StatefulDestructible, public Evoral::ControlL
 	AutomationList& operator= (const AutomationList&);
 	bool operator== (const AutomationList&);
 
-	void freeze();
 	void thaw ();
 	void mark_dirty () const;
 
diff --git a/libs/ardour/ardour/midi_track.h b/libs/ardour/ardour/midi_track.h
index bc636eea83..6f8fda78da 100644
--- a/libs/ardour/ardour/midi_track.h
+++ b/libs/ardour/ardour/midi_track.h
@@ -53,7 +53,7 @@ public:
 
 	int export_stuff (BufferSet& bufs, nframes_t nframes, sframes_t end_frame);
 
-	void freeze (InterThreadInfo&);
+	void freeze_me (InterThreadInfo&);
 	void unfreeze ();
 
 	boost::shared_ptr<Region> bounce (InterThreadInfo&);
diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index 1da185c6f2..09dd8f203c 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -93,9 +93,6 @@ class Region
 
         PBD::PropertyList* property_factory (const XMLNode&) const;
 
-	void unlock_property_changes () { _no_property_changes = false; }
-	void block_property_changes () { _no_property_changes = true; }
-	
 	virtual ~Region();
 	
 	/** Note: changing the name of a Region does not constitute an edit */
@@ -156,8 +153,7 @@ class Region
 	void set_position_lock_style (PositionLockStyle ps);
 	void recompute_position_from_lock_style ();
 
-	void freeze ();
-	void thaw ();
+	void suspend_property_changes ();
 
 	bool covers (framepos_t frame) const {
 		return first_frame() <= frame && frame <= last_frame();
@@ -288,6 +284,7 @@ class Region
 
   protected:
 	void send_change (const PBD::PropertyChange&);
+        void mid_thaw (const PBD::PropertyChange&);
 
 	void trim_to_internal (framepos_t position, framecnt_t length, void *src);
 	virtual void set_position_internal (framepos_t pos, bool allow_bbt_recompute);
@@ -304,7 +301,6 @@ class Region
 	virtual void recompute_at_end () = 0;
 	
 	DataType                _type;
-	bool                    _no_property_changes;
 
 	PBD::Property<bool>        _muted;
 	PBD::Property<bool>        _opaque;
@@ -332,14 +328,11 @@ class Region
 	framepos_t              _last_position;
 	PositionLockStyle       _positional_lock_style;
 	mutable RegionEditState _first_edit;
-	int                     _frozen;
 	BBT_Time                _bbt_time;
 	AnalysisFeatureList     _transients;
 	bool                    _valid_transients;
 	mutable uint64_t        _read_data_count;  ///< modified in read()
-	PBD::PropertyChange     _pending_changed;
 	uint64_t                _last_layer_op;  ///< timestamp
-	Glib::Mutex             _lock;
 	SourceList              _sources;
 	/** Used when timefx are applied, so we can always use the original source */
 	SourceList              _master_sources;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index d26c84a795..cf88f2e6bd 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -603,7 +603,7 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	boost::shared_ptr<Region> write_one_track (AudioTrack&, nframes_t start, nframes_t end,
 			bool overwrite, std::vector<boost::shared_ptr<Source> >&, InterThreadInfo& wot,
 			bool enable_processing = true);
-	int freeze (InterThreadInfo&);
+	int freeze_all (InterThreadInfo&);
 
 	/* session-wide solo/mute/rec-enable */
 
diff --git a/libs/ardour/ardour/track.h b/libs/ardour/ardour/track.h
index 0ed4b8c70b..eee9f03fe5 100644
--- a/libs/ardour/ardour/track.h
+++ b/libs/ardour/ardour/track.h
@@ -74,7 +74,7 @@ class Track : public Route
 
 	FreezeState freeze_state() const;
 
-	virtual void freeze (InterThreadInfo&) = 0;
+	virtual void freeze_me (InterThreadInfo&) = 0;
 	virtual void unfreeze () = 0;
 
 	virtual boost::shared_ptr<Region> bounce (InterThreadInfo&) = 0;
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index f7a1240bdd..1f77964d0d 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -35,7 +35,7 @@
 #include "pbd/xml++.h"
 #include "pbd/memento_command.h"
 #include "pbd/enumwriter.h"
-#include "pbd/stacktrace.h"
+#include "pbd/stateful_diff_command.h"
 
 #include "ardour/analyser.h"
 #include "ardour/ardour.h"
@@ -1497,7 +1497,7 @@ AudioDiskstream::transport_stopped (struct tm& when, time_t twhen, bool abort_ca
 
 		// cerr << _name << ": there are " << capture_info.size() << " capture_info records\n";
 
-		XMLNode &before = _playlist->get_state();
+                _playlist->clear_history ();
 		_playlist->freeze ();
 
 		for (buffer_position = c->front()->write_source->last_capture_start_frame(), ci = capture_info.begin(); ci != capture_info.end(); ++ci) {
@@ -1537,8 +1537,7 @@ AudioDiskstream::transport_stopped (struct tm& when, time_t twhen, bool abort_ca
 		}
 
 		_playlist->thaw ();
-		XMLNode &after = _playlist->get_state();
-		_session.add_command (new MementoCommand<Playlist>(*_playlist, &before, &after));
+		_session.add_command (new StatefulDiffCommand (_playlist));
 	}
 
 	mark_write_completed = true;
diff --git a/libs/ardour/audio_track.cc b/libs/ardour/audio_track.cc
index ebc7a9be66..245b122c18 100644
--- a/libs/ardour/audio_track.cc
+++ b/libs/ardour/audio_track.cc
@@ -692,7 +692,7 @@ AudioTrack::bounce_range (nframes_t start, nframes_t end, InterThreadInfo& itt,
 }
 
 void
-AudioTrack::freeze (InterThreadInfo& itt)
+AudioTrack::freeze_me (InterThreadInfo& itt)
 {
 	vector<boost::shared_ptr<Source> > srcs;
 	string new_playlist_name;
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index e30a3a5994..abddffc12e 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -589,7 +589,7 @@ AudioRegion::_set_state (const XMLNode& node, int version, PropertyChange& what_
 	LocaleGuard lg (X_("POSIX"));
 	boost::shared_ptr<Playlist> the_playlist (_playlist.lock());	
 
-	freeze ();
+	suspend_property_changes ();
 
 	if (the_playlist) {
 		the_playlist->freeze ();
@@ -612,7 +612,7 @@ AudioRegion::_set_state (const XMLNode& node, int version, PropertyChange& what_
 
 	/* Now find envelope description and other related child items */
 
-	_envelope->freeze ();
+        _envelope->freeze ();
 
 	for (XMLNodeConstIterator niter = nlist.begin(); niter != nlist.end(); ++niter) {
 		XMLNode *child;
@@ -677,9 +677,9 @@ AudioRegion::_set_state (const XMLNode& node, int version, PropertyChange& what_
 		}
 	}
 
-	_envelope->thaw ();
-	thaw ();
-
+        _envelope->thaw ();
+	resume_property_changes ();
+        
 	if (send) {
 		send_change (what_changed);
 	}
@@ -761,9 +761,9 @@ AudioRegion::set_fade_out_shape (FadeShape shape)
 void
 AudioRegion::set_fade_in (boost::shared_ptr<AutomationList> f)
 {
-	_fade_in->freeze ();
+        _fade_in->freeze ();
 	*_fade_in = *f;
-	_fade_in->thaw ();
+        _fade_in->thaw ();
 	
 	send_change (PropertyChange (Properties::fade_in));
 }
@@ -771,7 +771,7 @@ AudioRegion::set_fade_in (boost::shared_ptr<AutomationList> f)
 void
 AudioRegion::set_fade_in (FadeShape shape, framecnt_t len)
 {
-	_fade_in->freeze ();
+        _fade_in->freeze ();
 	_fade_in->clear ();
 
 	switch (shape) {
@@ -822,15 +822,15 @@ AudioRegion::set_fade_in (FadeShape shape, framecnt_t len)
 		break;
 	}
 
-	_fade_in->thaw ();
+        _fade_in->thaw ();
 }
 
 void
 AudioRegion::set_fade_out (boost::shared_ptr<AutomationList> f)
 {
-	_fade_out->freeze ();
+        _fade_out->freeze ();
 	*_fade_out = *f;
-	_fade_out->thaw ();
+        _fade_out->thaw ();
 
 	send_change (PropertyChange (Properties::fade_in));
 }
@@ -838,7 +838,7 @@ AudioRegion::set_fade_out (boost::shared_ptr<AutomationList> f)
 void
 AudioRegion::set_fade_out (FadeShape shape, framecnt_t len)
 {
-	_fade_out->freeze ();
+        _fade_out->freeze ();
 	_fade_out->clear ();
 
 	switch (shape) {
@@ -887,7 +887,7 @@ AudioRegion::set_fade_out (FadeShape shape, framecnt_t len)
 		break;
 	}
 
-	_fade_out->thaw ();
+        _fade_out->thaw ();
 }
 
 void
@@ -977,11 +977,11 @@ AudioRegion::set_default_fades ()
 void
 AudioRegion::set_default_envelope ()
 {
-	_envelope->freeze ();
+        _envelope->freeze ();
 	_envelope->clear ();
 	_envelope->fast_simple_add (0, 1.0f);
 	_envelope->fast_simple_add (_length, 1.0f);
-	_envelope->thaw ();
+        _envelope->thaw ();
 }
 
 void
@@ -991,10 +991,10 @@ AudioRegion::recompute_at_end ()
 	   based on the the existing curve.
 	*/
 
-	_envelope->freeze ();
+        _envelope->freeze ();
 	_envelope->truncate_end (_length);
 	_envelope->set_max_xval (_length);
-	_envelope->thaw ();
+        _envelope->thaw ();
 
 	if (_fade_in->back()->when > _length) {
 		_fade_in->extend_to (_length);
diff --git a/libs/ardour/automation_list.cc b/libs/ardour/automation_list.cc
index 479674aee6..92a3d167da 100644
--- a/libs/ardour/automation_list.cc
+++ b/libs/ardour/automation_list.cc
@@ -170,7 +170,7 @@ AutomationList::maybe_signal_changed ()
 {
 	ControlList::maybe_signal_changed ();
 
-	if (!_frozen) {
+	if (!ControlList::frozen()) {
 		StateChanged (); /* EMIT SIGNAL */
 	}
 }
@@ -208,12 +208,6 @@ AutomationList::stop_touch ()
 }
 
 void
-AutomationList::freeze ()
-{
-	_frozen++;
-}
-
-void
 AutomationList::thaw ()
 {
 	ControlList::thaw();
@@ -313,7 +307,7 @@ AutomationList::deserialize_events (const XMLNode& node)
 		return -1;
 	}
 
-	freeze ();
+        ControlList::freeze ();
 	clear ();
 
 	stringstream str (content_node->content());
@@ -344,8 +338,8 @@ AutomationList::deserialize_events (const XMLNode& node)
 		maybe_signal_changed ();
 	}
 
-	thaw ();
-
+        ControlList::thaw ();
+        
 	return 0;
 }
 
@@ -377,7 +371,7 @@ AutomationList::set_state (const XMLNode& node, int version)
 		nframes_t x;
 		double y;
 
-		freeze ();
+                ControlList::freeze ();
 		clear ();
 
 		for (i = elist.begin(); i != elist.end(); ++i) {
@@ -397,7 +391,7 @@ AutomationList::set_state (const XMLNode& node, int version)
 			fast_simple_add (x, y);
 		}
 
-		thaw ();
+                ControlList::thaw ();
 
 		return 0;
 	}
diff --git a/libs/ardour/midi_diskstream.cc b/libs/ardour/midi_diskstream.cc
index ccfaeaa5cd..836fb05c8b 100644
--- a/libs/ardour/midi_diskstream.cc
+++ b/libs/ardour/midi_diskstream.cc
@@ -35,6 +35,7 @@
 #include "pbd/xml++.h"
 #include "pbd/memento_command.h"
 #include "pbd/enumwriter.h"
+#include "pbd/stateful_diff_command.h"
 
 #include "ardour/ardour.h"
 #include "ardour/audioengine.h"
@@ -1011,7 +1012,7 @@ MidiDiskstream::transport_stopped (struct tm& /*when*/, time_t /*twhen*/, bool a
 
 		// cerr << _name << ": there are " << capture_info.size() << " capture_info records\n";
 
-		XMLNode &before = _playlist->get_state();
+		_playlist->clear_history ();
 		_playlist->freeze ();
 
 		uint32_t buffer_position = 0;
@@ -1053,8 +1054,7 @@ MidiDiskstream::transport_stopped (struct tm& /*when*/, time_t /*twhen*/, bool a
 		}
 
 		_playlist->thaw ();
-		XMLNode &after = _playlist->get_state();
-		_session.add_command (new MementoCommand<Playlist>(*_playlist, &before, &after));
+		_session.add_command (new StatefulDiffCommand(_playlist));
 
 	}
 
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index af66f2f40c..9409e9f143 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -556,7 +556,7 @@ MidiTrack::bounce_range (nframes_t /*start*/, nframes_t /*end*/, InterThreadInfo
 }
 
 void
-MidiTrack::freeze (InterThreadInfo& /*itt*/)
+MidiTrack::freeze_me (InterThreadInfo& /*itt*/)
 {
 }
 
diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index 6169df8f03..eb21cdcde6 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -855,7 +855,7 @@ Playlist::partition (framepos_t start, framepos_t end, bool cut)
 	partition_internal (start, end, cut, thawlist);
 
 	for (RegionList::iterator i = thawlist.begin(); i != thawlist.end(); ++i) {
-		(*i)->thaw ();
+		(*i)->resume_property_changes ();
 	}
 }
 
@@ -972,7 +972,7 @@ Playlist::partition_internal (framepos_t start, framepos_t end, bool cutting, Re
 
 				/* "front" ***** */
 
-				current->freeze ();
+				current->suspend_property_changes ();
 				thawlist.push_back (current);
 				current->trim_end (pos2, this);
 
@@ -1011,7 +1011,7 @@ Playlist::partition_internal (framepos_t start, framepos_t end, bool cutting, Re
 
 				/* front ****** */
 
-				current->freeze ();
+				current->suspend_property_changes ();
 				thawlist.push_back (current);
 				current->trim_end (pos2, this);
 
@@ -1054,7 +1054,7 @@ Playlist::partition_internal (framepos_t start, framepos_t end, bool cutting, Re
 
 				/* end */
 
-				current->freeze ();
+				current->suspend_property_changes ();
 				thawlist.push_back (current);
 				current->trim_front (pos3, this);
 			} else if (overlap == OverlapExternal) {
@@ -1157,7 +1157,7 @@ Playlist::cut (framepos_t start, framecnt_t cnt, bool result_is_hidden)
 	partition_internal (start, start+cnt-1, true, thawlist);
 
 	for (RegionList::iterator i = thawlist.begin(); i != thawlist.end(); ++i) {
-		(*i)->thaw ();
+		(*i)->resume_property_changes();
 	}
 
 	return the_copy;
@@ -2123,15 +2123,15 @@ Playlist::set_state (const XMLNode& node, int version)
 
 			if ((region = region_by_id (id))) {
 
-				region->freeze ();
+				region->suspend_property_changes ();
 
 				if (region->set_state (*child, version)) {
-					region->thaw ();
+					region->resume_property_changes ();
 					continue;
 				}
 				
 			} else if ((region = RegionFactory::create (_session, *child, true)) != 0) {
-				region->freeze ();
+				region->suspend_property_changes ();
 			} else {
 				error << _("Playlist: cannot create region from XML") << endmsg;
 				continue;
@@ -2141,7 +2141,7 @@ Playlist::set_state (const XMLNode& node, int version)
 
 			// So that layer_op ordering doesn't get screwed up
 			region->set_last_layer_op( region->layer());
-			region->thaw ();
+			region->resume_property_changes ();
 		}
 	}
 
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index f59d076c59..b89ad2854b 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -199,13 +199,11 @@ Region::register_properties ()
 Region::Region (Session& s, framepos_t start, framecnt_t length, const string& name, DataType type)
 	: SessionObject(s, name)
 	, _type(type)
-	, _no_property_changes (true)
 	, REGION_DEFAULT_STATE(start,length)
 	, _last_length (length)
 	, _last_position (0)
 	, _positional_lock_style(AudioTime)
 	, _first_edit (EditChangesNothing)
-	, _frozen(0)
 	, _read_data_count(0)
 	, _last_layer_op(0)
 	, _pending_explicit_relayer (false)
@@ -219,13 +217,11 @@ Region::Region (Session& s, framepos_t start, framecnt_t length, const string& n
 Region::Region (const SourceList& srcs)
 	: SessionObject(srcs.front()->session(), "toBeRenamed")
 	, _type (srcs.front()->type())
-	, _no_property_changes (true)
 	, REGION_DEFAULT_STATE(0,0)
 	, _last_length (0)
 	, _last_position (0)
         , _positional_lock_style (_type == DataType::AUDIO ? AudioTime : MusicTime)
 	, _first_edit (EditChangesNothing)
-	, _frozen (0)
 	, _valid_transients(false)
 	, _read_data_count(0)
 	, _last_layer_op (0)
@@ -251,13 +247,11 @@ Region::Region (const SourceList& srcs)
 Region::Region (boost::shared_ptr<const Region> other, frameoffset_t offset, bool offset_relative)
 	: SessionObject(other->session(), other->name())
 	, _type (other->data_type())
-	, _no_property_changes (true)
 	, REGION_COPY_STATE (other)
 	, _last_length (other->_last_length)
 	, _last_position(other->_last_position) \
 	, _positional_lock_style(other->_positional_lock_style) \
 	, _first_edit (EditChangesNothing)
-	, _frozen (0)
 	, _valid_transients(false)
 	, _read_data_count(0)
 	, _last_layer_op (0)
@@ -360,13 +354,11 @@ Region::Region (boost::shared_ptr<const Region> other, frameoffset_t offset, boo
 Region::Region (boost::shared_ptr<const Region> other, const SourceList& srcs)
 	: SessionObject (other->session(), other->name())
 	, _type (srcs.front()->type())
-	, _no_property_changes (true)
 	, REGION_COPY_STATE (other)
 	, _last_length (other->_last_length)
 	, _last_position (other->_last_position)
         , _positional_lock_style (other->_positional_lock_style)
 	, _first_edit (EditChangesID)
-	, _frozen (0)
 	, _valid_transients (false)
 	, _read_data_count (0)
 	, _last_layer_op (other->_last_layer_op)
@@ -393,13 +385,11 @@ Region::Region (boost::shared_ptr<const Region> other, const SourceList& srcs)
 Region::Region (boost::shared_ptr<const Region> other)
 	: SessionObject(other->session(), other->name())
 	, _type(other->data_type())
-	, _no_property_changes (true)
 	, REGION_COPY_STATE (other)
 	, _last_length (other->_last_length)
 	, _last_position (other->_last_position)
         , _positional_lock_style (other->_positional_lock_style)
 	, _first_edit (EditChangesID)
-	, _frozen(0)
 	, _valid_transients(false)
 	, _read_data_count(0)
 	, _last_layer_op(other->_last_layer_op)
@@ -475,7 +465,7 @@ Region::set_length (framecnt_t len, void */*src*/)
 		maybe_uncopy ();
 		invalidate_transients ();
 
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			recompute_at_end ();
 		}
 
@@ -803,7 +793,7 @@ Region::trim_front (framepos_t new_position, void *src)
 		}
 
 		trim_to_internal (new_position, newlen, src);
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			recompute_at_start ();
 		}
 	}
@@ -822,7 +812,7 @@ Region::trim_end (framepos_t new_endpoint, void */*src*/)
 
 	if (new_endpoint > _position) {
 		trim_to_internal (_position, new_endpoint - _position + 1, this);
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			recompute_at_end ();
 		}
 	}
@@ -837,7 +827,7 @@ Region::trim_to (framepos_t position, framecnt_t length, void *src)
 
 	trim_to_internal (position, length, src);
 
-	if (!_frozen) {
+	if (!property_changes_suspended()) {
 		recompute_at_start ();
 		recompute_at_end ();
 	}
@@ -890,14 +880,14 @@ Region::trim_to_internal (framepos_t position, framecnt_t length, void */*src*/)
 		what_changed.add (Properties::start);
 	}
 	if (_length != length) {
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			_last_length = _length;
 		}
 		_length = length;
 		what_changed.add (Properties::length);
 	}
 	if (_position != position) {
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			_last_position = _position;
 		}
 		_position = position;
@@ -987,7 +977,7 @@ Region::set_sync_position (framepos_t absolute_pos)
 	if (file_pos != _sync_position) {
 		_sync_marked = true;
 		_sync_position = file_pos;
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			maybe_uncopy ();
 		}
 		send_change (Properties::sync_position);
@@ -999,7 +989,7 @@ Region::clear_sync_position ()
 {
 	if (sync_marked()) {
 		_sync_marked = false;
-		if (!_frozen) {
+		if (!property_changes_suspended()) {
 			maybe_uncopy ();
 		}
 		send_change (Properties::sync_position);
@@ -1229,43 +1219,22 @@ Region::_set_state (const XMLNode& node, int version, PropertyChange& what_chang
 }
 
 void
-Region::freeze ()
+Region::suspend_property_changes ()
 {
-	_frozen++;
+        Stateful::suspend_property_changes ();
 	_last_length = _length;
 	_last_position = _position;
 }
 
 void
-Region::thaw ()
+Region::mid_thaw (const PropertyChange& what_changed)
 {
-	PropertyChange what_changed;
-
-	{
-		Glib::Mutex::Lock lm (_lock);
-
-		if (_frozen && --_frozen > 0) {
-			return;
-		}
-
-		if (!_pending_changed.empty()) {
-			what_changed = _pending_changed;
-			_pending_changed.clear ();
-		}
-	}
-
-	if (what_changed.empty()) {
-		return;
-	}
-
 	if (what_changed.contains (Properties::length)) {
 		if (what_changed.contains (Properties::position)) {
 			recompute_at_start ();
 		}
 		recompute_at_end ();
 	}
-
-	send_change (what_changed);
 }
 
 void
@@ -1275,15 +1244,7 @@ Region::send_change (const PropertyChange& what_changed)
 		return;
 	}
 
-	{
-		Glib::Mutex::Lock lm (_lock);
-		if (_frozen) {
-			_pending_changed.add (what_changed);
-			return;
-		}
-	}
-
-	PropertyChanged (what_changed);
+        Stateful::send_change (what_changed);
 
 	if (!_no_property_changes) {
 		
@@ -1294,12 +1255,10 @@ Region::send_change (const PropertyChange& what_changed)
 		try {
 			boost::shared_ptr<Region> rptr = shared_from_this();
 			RegionPropertyChanged (rptr, what_changed);
-
 		} catch (...) {
 			/* no shared_ptr available, relax; */
 		}
 	}
-
 }
 
 void
@@ -1584,16 +1543,26 @@ Region::set_property (const PropertyBase& prop)
 	} else if (prop == Properties::position_locked.property_id) {
 		_position_locked = dynamic_cast<const PropertyTemplate<bool>*>(&prop)->val();
 	} else if (prop == Properties::start.property_id) {
-		_start = dynamic_cast<const PropertyTemplate<framepos_t>*>(&prop)->val();
+		framepos_t val = dynamic_cast<const PropertyTemplate<framepos_t>*>(&prop)->val();
+                if (val != _start) {
+                        DEBUG_TRACE (DEBUG::Properties, string_compose ("region %1 start changed from %2 to %3",
+									_name.val(), _start, val));
+                        _start = val;
+                        return true;
+                }
 	} else if (prop == Properties::length.property_id) {
 		framecnt_t val = dynamic_cast<const PropertyTemplate<framecnt_t>* > (&prop)->val();
 		if (val != _length) {
+			DEBUG_TRACE (DEBUG::Properties, string_compose ("region %1 length changed from %2 to %3",
+									_name.val(), _length, val));
 			_length = val;
 			return true;
 		}
 	} else if (prop == Properties::position.property_id) {
 		framepos_t val = dynamic_cast<const PropertyTemplate<framepos_t>*>(&prop)->val();
 		if (val != _position) {
+			DEBUG_TRACE (DEBUG::Properties, string_compose ("region %1 position changed from %2 to %3",
+									_name.val(), _position, val));
 			_position = val;
 			return true;
 		}
diff --git a/libs/ardour/region_factory.cc b/libs/ardour/region_factory.cc
index d2c5fa1b22..3f4af2462c 100644
--- a/libs/ardour/region_factory.cc
+++ b/libs/ardour/region_factory.cc
@@ -67,7 +67,6 @@ RegionFactory::create (boost::shared_ptr<const Region> region)
 	}
 
 	if (ret) {
-		ret->unlock_property_changes ();
 		map_add (ret);
 
 		/* pure copy constructor - no property list */
@@ -106,10 +105,7 @@ RegionFactory::create (boost::shared_ptr<Region> region, frameoffset_t offset, c
 	}
 
 	if (ret) {
-
 		ret->set_properties (plist);
-		ret->unlock_property_changes ();
-
 		map_add (ret);
 
 		if (announce) {
@@ -149,10 +145,7 @@ RegionFactory::create (boost::shared_ptr<Region> region, const PropertyList& pli
 	}
 
 	if (ret) {
-
 		ret->set_properties (plist);
-		ret->unlock_property_changes ();
-
 		map_add (ret);
 
 		if (announce) {
@@ -195,8 +188,6 @@ RegionFactory::create (boost::shared_ptr<Region> region, const SourceList& srcs,
 	if (ret) {
 
 		ret->set_properties (plist);
-		ret->unlock_property_changes ();
-
 		map_add (ret);
 
 		if (announce) {
@@ -242,8 +233,6 @@ RegionFactory::create (const SourceList& srcs, const PropertyList& plist, bool a
 	if (ret) {
 
 		ret->set_properties (plist);
-		ret->unlock_property_changes ();
-
 		map_add (ret);
 
 		if (announce) {
@@ -290,7 +279,6 @@ RegionFactory::create (SourceList& srcs, const XMLNode& node)
 		if (ret->set_state (node, Stateful::loading_state_version)) {
 			ret.reset ();
 		} else {
-			ret->unlock_property_changes ();
 			map_add (ret);
 			CheckNewRegion (ret);
 		}
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 0c2f12d91d..53c8ea2350 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -3847,7 +3847,7 @@ Session::allocate_pan_automation_buffers (nframes_t nframes, uint32_t howmany, b
 }
 
 int
-Session::freeze (InterThreadInfo& itt)
+Session::freeze_all (InterThreadInfo& itt)
 {
 	shared_ptr<RouteList> r = routes.reader ();
 
@@ -3859,7 +3859,7 @@ Session::freeze (InterThreadInfo& itt)
 			/* XXX this is wrong because itt.progress will keep returning to zero at the start
 			   of every track.
 			*/
-			t->freeze (itt);
+			t->freeze_me (itt);
 		}
 	}