new RegionCommand object; remove unused string argument from Region::thaw(); add map<ID,Region> in RegionFactory so that we can look up regions by ID

git-svn-id: svn://localhost/ardour2/branches/3.0@6652 d708f5d6-7413-0410-9779-e7cbd77b26cf

15 files changed, 490 insertions, 9 deletions

diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index 4cae00c532..310bd582cd 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -162,7 +162,7 @@ class Region
 	void recompute_position_from_lock_style ();
 
 	void freeze ();
-	void thaw (const std::string& why);
+	void thaw ();
 
 	bool covers (nframes_t frame) const {
 		return first_frame() <= frame && frame <= last_frame();
diff --git a/libs/ardour/ardour/region_command.h b/libs/ardour/ardour/region_command.h
new file mode 100644
index 0000000000..07589b70c7
--- /dev/null
+++ b/libs/ardour/ardour/region_command.h
@@ -0,0 +1,104 @@
+#ifndef __libardour_region_command_h__
+#define __libardour_region_command_h__
+
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "pbd/command.h"
+
+namespace ARDOUR  {
+
+class Region;
+
+class RegionCommand : public Command {
+  public:
+	enum Property {
+		Name,
+		PositionLockStyle,
+		Length,
+		Start,
+		Position,
+		PositionOnTop,
+		Layer,
+		SyncPosition,
+		Hidden,
+		Muted,
+		Opaque,
+		Locked,
+		PositionLocked,
+
+		/* audio */
+		ScaleAmplitude,
+		FadeInActive,
+		FadeInShape,
+		FadeInLength,
+		FadeIn,
+		FadeOutActive,
+		FadeOutShape,
+		FadeOutLength,
+		FadeOut,
+		EnvelopActive,
+		DefaultEnvelope
+	};
+	
+	RegionCommand (boost::shared_ptr<Region>);
+	RegionCommand (boost::shared_ptr<Region>, const XMLNode&);
+	RegionCommand (boost::shared_ptr<Region>, Property, const std::string& target_value);
+
+	
+	/* this is mildly type-unsafe, in that we could pass in the wrong types for before&after
+	   given the value of `property'. however, its just as safe as a variant that accepts
+	   strings, and makes this whole class much easier to use.
+	*/
+
+	template<typename T> void add_property_change (Property property, const T& before, const T& after) {
+		std::stringstream sb, sa;
+
+		/* in case T is a floating point value ... 
+		 */
+
+		sb.precision (15);
+		sa.precision (15);
+
+		/* format */
+
+		sb << before;
+		sa << after;
+
+		/* and stash it away */
+
+		_add_property_change (property, sb.str(), sa.str());
+	}
+	
+	void set_name (const std::string& str) { _name = str; }
+	const std::string& name() const { return _name; }
+	
+	void operator() ();
+	void undo();
+	void redo() { (*this)(); }
+	
+	XMLNode &get_state();
+	int set_state (const XMLNode&, int /*version*/);
+
+  private:
+	struct PropertyTriple {
+	    Property property;
+	    std::string before;
+	    std::string after;
+
+	    PropertyTriple (Property p, const std::string& b, const std::string& a)
+	         : property (p), before (b), after (a) {}
+	};
+
+	boost::shared_ptr<Region> region;
+	typedef std::vector<PropertyTriple> PropertyTriples;
+	PropertyTriples property_changes;
+
+	void do_property_change (Property prop, const std::string& value);
+	void _add_property_change (Property, const std::string& before_value, const std::string& after_value);
+};
+
+}
+
+#endif /* __libardour_region_command_h__ */
diff --git a/libs/ardour/ardour/region_factory.h b/libs/ardour/ardour/region_factory.h
index b53e9490de..64d3417287 100644
--- a/libs/ardour/ardour/region_factory.h
+++ b/libs/ardour/ardour/region_factory.h
@@ -20,6 +20,10 @@
 #ifndef __ardour_region_factory_h__
 #define __ardour_region_factory_h__
 
+#include <map>
+
+#include "pbd/id.h"
+
 #include "ardour/types.h"
 #include "ardour/region.h"
 
@@ -33,6 +37,10 @@ class AudioRegion;
 class RegionFactory {
 
   public:
+
+	static boost::shared_ptr<Region> region_by_id (const PBD::ID&);
+	static void clear_map ();
+
 	/** This is emitted only when a new id is assigned. Therefore,
 	   in a pure Region copy, it will not be emitted.
 
@@ -59,6 +67,10 @@ class RegionFactory {
 	static boost::shared_ptr<Region> create (const SourceList &, nframes_t start, nframes_t length, const std::string& name, layer_t = 0, Region::Flag flags = Region::DefaultFlags, bool announce = true);
 	static boost::shared_ptr<Region> create (Session&, XMLNode&, bool);
 	static boost::shared_ptr<Region> create (SourceList &, const XMLNode&);
+
+  private:
+	static std::map<PBD::ID,boost::weak_ptr<Region> > region_map;
+	static void map_add (boost::shared_ptr<Region>);
 };
 
 }
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 729398cf21..e904541ac4 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -767,7 +767,7 @@ AudioRegion::set_live_state (const XMLNode& node, int version, Change& what_chan
 	}
 
 	_envelope->thaw ();
-	thaw ("");
+	thaw ();
 
 	if (send) {
 		cerr << _name << ": audio final change: " << hex << what_changed << dec << endl;
diff --git a/libs/ardour/enums.cc b/libs/ardour/enums.cc
index 7d07a5a95f..9a512fe708 100644
--- a/libs/ardour/enums.cc
+++ b/libs/ardour/enums.cc
@@ -33,6 +33,7 @@
 #include "ardour/midi_track.h"
 #include "ardour/mute_master.h"
 #include "ardour/panner.h"
+#include "ardour/region_command.h"
 #include "ardour/route_group.h"
 #include "ardour/session.h"
 #include "ardour/track.h"
@@ -121,6 +122,7 @@ setup_enum_writer ()
 	Session::PostTransportWork _Session_PostTransportWork;
 	Session::SlaveState _Session_SlaveState;
 	MTC_Status _MIDI_MTC_Status;
+	RegionCommand::Property _RegionCommandProperty;
 
 #define REGISTER(e) enum_writer.register_distinct (typeid(e).name(), i, s); i.clear(); s.clear()
 #define REGISTER_BITS(e) enum_writer.register_bits (typeid(e).name(), i, s); i.clear(); s.clear()
@@ -583,6 +585,31 @@ setup_enum_writer ()
 	REGISTER_ENUM(Groove);
 	REGISTER(_QuantizeType);
 
+	REGISTER_CLASS_ENUM (RegionCommand, Name);
+	REGISTER_CLASS_ENUM (RegionCommand, PositionLockStyle);
+	REGISTER_CLASS_ENUM (RegionCommand, Length);
+	REGISTER_CLASS_ENUM (RegionCommand, Start);
+	REGISTER_CLASS_ENUM (RegionCommand, Position);
+	REGISTER_CLASS_ENUM (RegionCommand, PositionOnTop);
+	REGISTER_CLASS_ENUM (RegionCommand, Layer);
+	REGISTER_CLASS_ENUM (RegionCommand, SyncPosition);
+	REGISTER_CLASS_ENUM (RegionCommand, Hidden);
+	REGISTER_CLASS_ENUM (RegionCommand, Muted);
+	REGISTER_CLASS_ENUM (RegionCommand, Opaque);
+	REGISTER_CLASS_ENUM (RegionCommand, Locked);
+	REGISTER_CLASS_ENUM (RegionCommand, PositionLocked);
+	REGISTER_CLASS_ENUM (RegionCommand, ScaleAmplitude);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeInActive);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeInShape);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeInLength);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeIn);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeOutActive);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeOutShape);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeOutLength);
+	REGISTER_CLASS_ENUM (RegionCommand, FadeOut);
+	REGISTER_CLASS_ENUM (RegionCommand, EnvelopActive);
+	REGISTER_CLASS_ENUM (RegionCommand, DefaultEnvelope);
+	REGISTER(_RegionCommandProperty);
 }
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/export_graph_builder.cc b/libs/ardour/export_graph_builder.cc
index 3b1d1e3838..01c2934555 100644
--- a/libs/ardour/export_graph_builder.cc
+++ b/libs/ardour/export_graph_builder.cc
@@ -44,7 +44,7 @@ ExportGraphBuilder::~ExportGraphBuilder ()
 }
 
 int
-ExportGraphBuilder::process (nframes_t frames, bool last_cycle)
+ExportGraphBuilder::process (nframes_t /* frames */, bool last_cycle)
 {
 	for (ChannelMap::iterator it = channels.begin(); it != channels.end(); ++it) {
 		it->first->read (process_buffer, process_buffer_frames);
diff --git a/libs/ardour/mute_master.cc b/libs/ardour/mute_master.cc
index 14411580fd..e7810b27fd 100644
--- a/libs/ardour/mute_master.cc
+++ b/libs/ardour/mute_master.cc
@@ -34,7 +34,7 @@ const MuteMaster::MutePoint MuteMaster::AllPoints = MutePoint (MuteMaster::PreFa
 							       MuteMaster::Listen|
 							       MuteMaster::Main);
 
-MuteMaster::MuteMaster (Session& s, const std::string& name)
+MuteMaster::MuteMaster (Session&, const std::string&)
 	: _mute_point (MutePoint (0))
 {
 }
diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index 689c1fe35b..39bd5695b4 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -762,7 +762,7 @@ Playlist::partition (nframes_t start, nframes_t end, bool cut)
 	partition_internal (start, end, cut, thawlist);
 
 	for (RegionList::iterator i = thawlist.begin(); i != thawlist.end(); ++i) {
-		(*i)->thaw ("separation");
+		(*i)->thaw ();
 	}
 }
 
@@ -1027,7 +1027,7 @@ Playlist::cut (nframes_t start, nframes_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 ("playlist cut");
+		(*i)->thaw ();
 	}
 
 	return the_copy;
@@ -1900,7 +1900,7 @@ Playlist::set_state (const XMLNode& node, int version)
 				region->freeze ();
 
 				if (region->set_live_state (*child, version, what_changed, false)) {
-					region->thaw ("");
+					region->thaw ();
 					continue;
 				}
 
@@ -1915,7 +1915,7 @@ 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->thaw ();
 		}
 	}
 
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 1f4d6f0f91..f1dd92abe5 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -1324,7 +1324,7 @@ Region::freeze ()
 }
 
 void
-Region::thaw (const string& /*why*/)
+Region::thaw ()
 {
 	Change what_changed = Change (0);
 
diff --git a/libs/ardour/region_command.cc b/libs/ardour/region_command.cc
new file mode 100644
index 0000000000..02a542e6c7
--- /dev/null
+++ b/libs/ardour/region_command.cc
@@ -0,0 +1,274 @@
+#include "pbd/convert.h"
+#include "pbd/xml++.h"
+#include "pbd/locale_guard.h"
+#include "pbd/enumwriter.h"
+
+#include "ardour/region.h"
+#include "ardour/region_command.h"
+#include "ardour/utils.h"
+
+#include "i18n.h"
+
+using namespace ARDOUR;
+using namespace PBD;
+using namespace std;
+
+RegionCommand::RegionCommand (boost::shared_ptr<Region> r, const XMLNode& node)
+	: region (r)
+{
+	if (set_state (node, 0)) {
+		throw failed_constructor();
+	}
+}
+
+RegionCommand::RegionCommand (boost::shared_ptr<Region> r)
+	: region (r)
+{
+}
+
+RegionCommand::RegionCommand (boost::shared_ptr<Region> r, Property prop, const std::string& target_value)
+	: region (r)
+{
+	LocaleGuard lg ("POSIX");
+	string before;
+	char buf[128];
+
+	/* get current value as a string */
+	
+	switch (prop) {
+	case Name:
+		before = r->name();
+		break;
+	case PositionLockStyle:
+		before = enum_2_string (r->positional_lock_style());
+		break;
+	case Length:
+		snprintf (buf, sizeof (buf), "%" PRId32, r->length());
+		before = buf;
+		break;
+	case Start:
+		snprintf (buf, sizeof (buf), "%" PRId32, r->start());
+		before = buf;
+		break;
+	case Position:
+		snprintf (buf, sizeof (buf), "%" PRId32, r->position());
+		before = buf;
+		break;
+	case PositionOnTop:
+		snprintf (buf, sizeof (buf), "%" PRId32, r->position());
+		before = buf;
+		break;
+	case Layer:
+		snprintf (buf, sizeof (buf), "%" PRId32, r->layer());
+		before = buf;
+		break;
+	case SyncPosition:
+		snprintf (buf, sizeof (buf), "%" PRId32, r->sync_position());
+		before = buf;
+		break;
+	case Hidden:
+		before = (r->hidden() ? "yes" : "no");
+		break;
+	case Muted:
+		before = (r->muted() ? "yes" : "no");
+		break;
+	case Opaque:
+		before = (r->opaque() ? "yes" : "no");
+		break;
+	case Locked:
+		before = (r->locked() ? "yes" : "no");
+		break;
+	case PositionLocked:
+		before = (r->position_locked() ? "yes" : "no");
+		break;
+		
+        /* audio */
+
+	case ScaleAmplitude:
+		break;
+	case FadeInActive:
+		break;
+	case FadeInShape:
+		break;
+	case FadeInLength:
+		break;
+	case FadeIn:
+		break;
+	case FadeOutActive:
+		break;
+	case FadeOutShape:
+		break;
+	case FadeOutLength:
+		break;
+	case FadeOut:
+		break;
+	case EnvelopActive:
+		break;
+	case DefaultEnvelope:
+		break;
+		
+	}
+
+	add_property_change (prop, before, target_value);
+}
+
+void
+RegionCommand::_add_property_change (Property prop, const std::string& before, const std::string& after)
+{
+	property_changes.push_back (PropertyTriple (prop, before, after));
+}
+
+void
+RegionCommand::operator() ()
+{
+	region->freeze ();
+	for (PropertyTriples::iterator i= property_changes.begin(); i != property_changes.end(); ++i) {
+		do_property_change (i->property, i->after);
+	}
+	region->thaw ();
+}
+
+void
+RegionCommand::undo ()
+{
+	region->freeze ();
+	for (PropertyTriples::iterator i= property_changes.begin(); i != property_changes.end(); ++i) {
+		do_property_change (i->property, i->before);
+	}
+	region->thaw ();
+}
+
+void
+RegionCommand::do_property_change (Property prop, const std::string& value)
+{
+	Region::PositionLockStyle pls;
+
+	switch (prop) {
+	case Name:
+		region->set_name (value);
+		break;
+	case PositionLockStyle:
+		region->set_position_lock_style ((Region::PositionLockStyle) string_2_enum (value, pls));
+		break;
+	case Length:
+		region->set_length (atoll (value), this);
+		break;
+	case Start:
+		region->set_start (atoll (value), this);
+		break;
+	case Position:
+		region->set_position (atoll (value), this);
+		break;
+	case PositionOnTop:
+		region->set_position_on_top (atoll (value), this);
+		break;
+	case Layer:
+		region->set_layer (atoi (value));
+		break;
+	case SyncPosition:
+		region->set_sync_position (atoi (value));
+		break;
+	case Hidden:
+		region->set_hidden (string_is_affirmative (value));
+		break;
+	case Muted:
+		region->set_muted (string_is_affirmative (value));
+		break;
+	case Opaque:
+		region->set_opaque (string_is_affirmative (value));
+		break;
+	case Locked:
+		region->set_locked (string_is_affirmative (value));
+		break;
+	case PositionLocked:
+		region->set_position_locked (string_is_affirmative (value));
+		break;
+
+        /* audio */
+
+	case ScaleAmplitude:
+		break;
+	case FadeInActive:
+		break;
+	case FadeInShape:
+		break;
+	case FadeInLength:
+		break;
+	case FadeIn:
+		break;
+	case FadeOutActive:
+		break;
+	case FadeOutShape:
+		break;
+	case FadeOutLength:
+		break;
+	case FadeOut:
+		break;
+	case EnvelopActive:
+		break;
+	case DefaultEnvelope:
+		break;
+		
+	}
+}
+
+XMLNode&
+RegionCommand::get_state ()
+{
+	XMLNode* node = new XMLNode (X_("RegionCommand"));
+	XMLNode* child;
+	
+	node->add_property (X_("region"), region->id().to_s());
+	
+	for (PropertyTriples::iterator i = property_changes.begin(); i != property_changes.end(); ++i) {
+
+		child = new XMLNode (X_("Op"));
+
+		child->add_property (X_("property"), enum_2_string (i->property));
+		child->add_property (X_("before"), i->before);
+		child->add_property (X_("after"), i->after);
+
+		node->add_child_nocopy (*child);
+	}
+
+	return *node;
+}
+
+int
+RegionCommand::set_state (const XMLNode& node, int /* version */)
+{
+	const XMLNodeList& children (node.children());
+	Property property;
+	string before;
+	string after;
+	const XMLProperty* prop;
+	
+	for (XMLNodeList::const_iterator i = children.begin(); i != children.end(); ++i) {
+
+		if ((*i)->name() != X_("Op")) {
+			continue;
+		}
+
+		if ((prop = (*i)->property (X_("property"))) == 0) {
+			return -1;
+		}
+
+		property = (Property) string_2_enum (prop->value(), property);
+
+		if ((prop = (*i)->property (X_("before"))) == 0) {
+			return -1;
+		}
+
+		before = prop->value();
+
+		if ((prop = (*i)->property (X_("after"))) == 0) {
+			return -1;
+		}
+
+		after = prop->value();
+
+		add_property_change (property, before, after);
+	}
+
+	return 0;
+}
diff --git a/libs/ardour/region_factory.cc b/libs/ardour/region_factory.cc
index 70ea326230..273066855b 100644
--- a/libs/ardour/region_factory.cc
+++ b/libs/ardour/region_factory.cc
@@ -35,6 +35,7 @@ using namespace ARDOUR;
 using namespace PBD;
 
 PBD::Signal1<void,boost::shared_ptr<Region> > RegionFactory::CheckNewRegion;
+map<PBD::ID,boost::weak_ptr<Region> > RegionFactory::region_map;
 
 boost::shared_ptr<Region>
 RegionFactory::create (boost::shared_ptr<Region> region, nframes_t start,
@@ -50,6 +51,7 @@ RegionFactory::create (boost::shared_ptr<Region> region, nframes_t start,
 		boost::shared_ptr<AudioRegion> arp (ar);
 		boost::shared_ptr<Region> ret (boost::static_pointer_cast<Region> (arp));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -59,6 +61,7 @@ RegionFactory::create (boost::shared_ptr<Region> region, nframes_t start,
 		boost::shared_ptr<MidiRegion> arp (ar);
 		boost::shared_ptr<Region> ret (boost::static_pointer_cast<Region> (arp));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -82,6 +85,7 @@ RegionFactory::create (boost::shared_ptr<const Region> region)
 		boost_debug_shared_ptr_mark_interesting (arn, "Region");
 		boost::shared_ptr<Region> ret (arn);
 		ret->unlock_property_changes ();
+		map_add (ret);
 		/* pure copy constructor - no CheckNewRegion emitted */
 		return ret;
 	} else if ((mr = boost::dynamic_pointer_cast<const MidiRegion>(region)) != 0) {
@@ -122,6 +126,7 @@ RegionFactory::create (boost::shared_ptr<Region> region, const SourceList& srcs,
 		boost::shared_ptr<AudioRegion> arp (ar);
 		boost::shared_ptr<Region> ret (boost::static_pointer_cast<Region> (arp));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -141,6 +146,7 @@ RegionFactory::create (Session& session, XMLNode& node, bool yn)
 
 	if (r) {
 		r->unlock_property_changes ();
+		map_add (r);
 		CheckNewRegion (r);
 	}
 
@@ -161,6 +167,7 @@ RegionFactory::create (const SourceList& srcs, nframes_t start, nframes_t length
 		boost::shared_ptr<AudioRegion> arp (ar);
 		boost::shared_ptr<Region> ret (boost::static_pointer_cast<Region> (arp));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -172,6 +179,7 @@ RegionFactory::create (const SourceList& srcs, nframes_t start, nframes_t length
 		boost::shared_ptr<MidiRegion> mrp (ar);
 		boost::shared_ptr<Region> ret (boost::static_pointer_cast<Region> (mrp));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -194,11 +202,13 @@ RegionFactory::create (SourceList& srcs, const XMLNode& node)
 		boost_debug_shared_ptr_mark_interesting (ar, "Region");
 		boost::shared_ptr<Region> ret (ar);
 		ret->unlock_property_changes ();
+		map_add (ret);
 		CheckNewRegion (ret);
 		return ret;
 	} else if (srcs[0]->type() == DataType::MIDI) {
 		boost::shared_ptr<Region> ret (new MidiRegion (srcs, node));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		CheckNewRegion (ret);
 		return ret;
 	}
@@ -217,6 +227,7 @@ RegionFactory::create (boost::shared_ptr<Source> src, nframes_t start, nframes_t
 		boost_debug_shared_ptr_mark_interesting (ar, "Region");
 		boost::shared_ptr<Region> ret (ar);
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -224,6 +235,7 @@ RegionFactory::create (boost::shared_ptr<Source> src, nframes_t start, nframes_t
 	} else if ((ms = boost::dynamic_pointer_cast<MidiSource>(src)) != 0) {
 		boost::shared_ptr<Region> ret (new MidiRegion (ms, start, length, name, layer, flags));
 		ret->unlock_property_changes ();
+		map_add (ret);
 		if (announce) {
 			CheckNewRegion (ret);
 		}
@@ -232,3 +244,31 @@ RegionFactory::create (boost::shared_ptr<Source> src, nframes_t start, nframes_t
 
 	return boost::shared_ptr<Region>();
 }
+
+void
+RegionFactory::map_add (boost::shared_ptr<Region> r)
+{
+	pair<ID,boost::weak_ptr<Region> > p;
+	p.first = r->id();
+	p.second = r;
+
+	region_map.insert (p);
+}
+
+boost::shared_ptr<Region>
+RegionFactory::region_by_id (const PBD::ID& id)
+{
+	map<ID,boost::weak_ptr<Region> >::iterator i = region_map.find (id);
+
+	if (i == region_map.end()) {
+		return boost::shared_ptr<Region>();
+	}
+
+	return i->second.lock();
+}
+	
+void
+RegionFactory::clear_map ()
+{
+	region_map.clear ();
+}
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 31693daff3..7b12478092 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -352,6 +352,10 @@ Session::destroy ()
 
 	_engine.remove_session ();
 
+	/* clear region map. it doesn't hold references, but lets just be sensible here */
+
+	RegionFactory::clear_map ();
+
 	/* clear history so that no references to objects are held any more */
 
 	_history.clear ();
diff --git a/libs/ardour/session_command.cc b/libs/ardour/session_command.cc
index 828af69901..19253cc725 100644
--- a/libs/ardour/session_command.cc
+++ b/libs/ardour/session_command.cc
@@ -83,32 +83,40 @@ Session::memento_command_factory(XMLNode *n)
 
     /* create command */
     string obj_T = n->property ("type-name")->value();
+
     if (obj_T == typeid (AudioRegion).name() || obj_T == typeid (MidiRegion).name() || obj_T == typeid (Region).name()) {
 	    if (regions.count(id)) {
 		    return new MementoCommand<Region>(*regions[id], before, after);
 	    }
+
     } else if (obj_T == typeid (AudioSource).name() || obj_T == typeid (MidiSource).name()) {
 	    if (sources.count(id))
 		    return new MementoCommand<Source>(*sources[id], before, after);
+
     } else if (obj_T == typeid (Location).name()) {
 	    Location* loc = _locations.get_location_by_id(id);
 	    if (loc) {
 		    return new MementoCommand<Location>(*loc, before, after);
 	    }
+
     } else if (obj_T == typeid (Locations).name()) {
 	    return new MementoCommand<Locations>(_locations, before, after);
+
     } else if (obj_T == typeid (TempoMap).name()) {
 	    return new MementoCommand<TempoMap>(*_tempo_map, before, after);
+
     } else if (obj_T == typeid (Playlist).name() || obj_T == typeid (AudioPlaylist).name() || obj_T == typeid (MidiPlaylist).name()) {
 	    if (boost::shared_ptr<Playlist> pl = playlists->by_name(child->property("name")->value())) {
 		    return new MementoCommand<Playlist>(*(pl.get()), before, after);
 	    }
+
     } else if (obj_T == typeid (Route).name() || obj_T == typeid (AudioTrack).name() || obj_T == typeid(MidiTrack).name()) {
 		if (boost::shared_ptr<Route> r = route_by_id(id)) {
 			return new MementoCommand<Route>(*r, before, after);
 		} else {
 			error << string_compose (X_("Route %1 not found in session"), id) << endmsg;
 		}
+
     } else if (obj_T == typeid (Evoral::Curve).name() || obj_T == typeid (AutomationList).name()) {
 		std::map<PBD::ID, AutomationList*>::iterator i = automation_lists.find(id);
 		if (i != automation_lists.end()) {
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 483c9a0899..fd14094f7f 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -91,6 +91,7 @@
 #include "ardour/midi_track.h"
 #include "ardour/named_selection.h"
 #include "ardour/processor.h"
+#include "ardour/region_command.h"
 #include "ardour/region_factory.h"
 #include "ardour/route_group.h"
 #include "ardour/send.h"
@@ -2944,6 +2945,16 @@ Session::restore_history (string snapshot_name)
 					error << _("Failed to downcast MidiSource for DeltaCommand") << endmsg;
 				}
 
+			} else if (n->name() == "RegionCommand") {
+				PBD::ID id (n->property ("region")->value());
+				boost::shared_ptr<Region> region = RegionFactory::region_by_id (id);
+
+				if (region) {
+					ut->add_command (new RegionCommand (region, *n));
+				} else {
+					error << string_compose (_("Region command references an unknown region ID=%1"), id.to_s()) << endmsg;
+				}
+
 			} else {
 				error << string_compose(_("Couldn't figure out how to make a Command out of a %1 XMLNode."), n->name()) << endmsg;
 			}
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index 33de254b36..ee9aa14850 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -144,6 +144,7 @@ libardour_sources = [
 	'rc_configuration.cc',
 	'recent_sessions.cc',
 	'region.cc',
+	'region_command.cc',
 	'region_factory.cc',
 	'resampled_source.cc',
 	'return.cc',