(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

13 files changed, 174 insertions, 222 deletions

diff --git a/gtk2_ardour/audio_region_editor.cc b/gtk2_ardour/audio_region_editor.cc
index e246c04391..adbb1e04ea 100644
--- a/gtk2_ardour/audio_region_editor.cc
+++ b/gtk2_ardour/audio_region_editor.cc
@@ -18,6 +18,7 @@
 */
 
 #include "pbd/memento_command.h"
+#include "pbd/stateful_diff_command.h"
 
 #include "ardour/session.h"
 #include "ardour/audioregion.h"
@@ -256,10 +257,9 @@ AudioRegionEditor::position_clock_changed ()
 	boost::shared_ptr<Playlist> pl = _region->playlist();
 
 	if (pl) {
-		XMLNode &before = pl->get_state();
+		_region->clear_history ();
 		_region->set_position (position_clock.current_time(), this);
-		XMLNode &after = pl->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
+		_session->add_command(new StatefulDiffCommand (_region));
 	}
 
 	_session->commit_reversible_command ();
@@ -273,10 +273,9 @@ AudioRegionEditor::end_clock_changed ()
 	boost::shared_ptr<Playlist> pl = _region->playlist();
 
 	if (pl) {
-		XMLNode &before = pl->get_state();
+                _region->clear_history ();
 		_region->trim_end (end_clock.current_time(), this);
-		XMLNode &after = pl->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
+		_session->add_command(new StatefulDiffCommand (_region));
 	}
 
 	_session->commit_reversible_command ();
@@ -294,10 +293,9 @@ AudioRegionEditor::length_clock_changed ()
 	boost::shared_ptr<Playlist> pl = _region->playlist();
 
 	if (pl) {
-		XMLNode &before = pl->get_state();
+                _region->clear_history ();
 		_region->trim_end (_region->position() + frames - 1, this);
-		XMLNode &after = pl->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*pl, &before, &after));
+		_session->add_command(new StatefulDiffCommand (_region));
 	}
 
 	_session->commit_reversible_command ();
@@ -404,10 +402,9 @@ AudioRegionEditor::sync_offset_absolute_clock_changed ()
 {
 	_session->begin_reversible_command (_("change region sync point"));
 
-	XMLNode& before = _region->get_state ();
+        _region->clear_history ();
 	_region->set_sync_position (sync_offset_absolute_clock.current_time());
-	XMLNode& after = _region->get_state ();
-	_session->add_command (new MementoCommand<AudioRegion> (*_region.get(), &before, &after));
+	_session->add_command (new StatefulDiffCommand (_region));
 	
 	_session->commit_reversible_command ();
 }
@@ -417,10 +414,9 @@ AudioRegionEditor::sync_offset_relative_clock_changed ()
 {
 	_session->begin_reversible_command (_("change region sync point"));
 
-	XMLNode& before = _region->get_state ();
+        _region->clear_history ();
 	_region->set_sync_position (sync_offset_relative_clock.current_time() + _region->position ());
-	XMLNode& after = _region->get_state ();
-	_session->add_command (new MementoCommand<AudioRegion> (*_region.get(), &before, &after));
+	_session->add_command (new StatefulDiffCommand (_region));
 	
 	_session->commit_reversible_command ();
 }
diff --git a/gtk2_ardour/audio_region_view.cc b/gtk2_ardour/audio_region_view.cc
index 438867c9dc..7a0e76606e 100644
--- a/gtk2_ardour/audio_region_view.cc
+++ b/gtk2_ardour/audio_region_view.cc
@@ -267,8 +267,8 @@ AudioRegionView::audio_region() const
 void
 AudioRegionView::region_changed (const PropertyChange& what_changed)
 {
-	ENSURE_GUI_THREAD (*this, &AudioRegionView::region_changed, what_changed)
-	//cerr << "AudioRegionView::region_changed() called" << endl;
+	ENSURE_GUI_THREAD (*this, &AudioRegionView::region_changed, what_changed);
+        // cerr << "AudioRegionView::region_changed() called" << endl;
 
 	RegionView::region_changed (what_changed);
 
@@ -276,7 +276,7 @@ AudioRegionView::region_changed (const PropertyChange& what_changed)
 		region_scale_amplitude_changed ();
 	}
 	if (what_changed.contains (ARDOUR::Properties::fade_in)) {
-			fade_in_changed ();
+                fade_in_changed ();
 	}
 	if (what_changed.contains (ARDOUR::Properties::fade_out)) {
 		fade_out_changed ();
@@ -1022,6 +1022,10 @@ AudioRegionView::add_gain_point_event (ArdourCanvas::Item *item, GdkEvent *ev)
 
 	gain_line->view_to_model_coord (x, y);
 
+        /* XXX STATEFUL: can't convert to stateful diff until we 
+           can represent automation data with it.
+        */
+
 	trackview.session()->begin_reversible_command (_("add gain control point"));
 	XMLNode &before = audio_region()->envelope()->get_state();
 
diff --git a/gtk2_ardour/audio_streamview.cc b/gtk2_ardour/audio_streamview.cc
index 640120516c..ac95bf63c2 100644
--- a/gtk2_ardour/audio_streamview.cc
+++ b/gtk2_ardour/audio_streamview.cc
@@ -660,10 +660,10 @@ AudioStreamView::update_rec_regions ()
 
 					if (nlen != region->length()) {
 
-						region->freeze ();
+						region->suspend_property_changes ();
 						region->set_position (_trackview.get_diskstream()->get_capture_start_frame(n), this);
 						region->set_length (nlen, this);
-						region->thaw ();
+						region->resume_property_changes ();
 
 						if (origlen == 1) {
 							/* our special initial length */
@@ -685,10 +685,10 @@ AudioStreamView::update_rec_regions ()
 
 					if (region->source_length(0) >= region->start() + nlen) {
 
-						region->freeze ();
+						region->suspend_property_changes ();
 						region->set_position (_trackview.get_diskstream()->get_capture_start_frame(n), this);
 						region->set_length (nlen, this);
-						region->thaw ();
+						region->resume_property_changes ();
 
 						if (origlen == 1) {
 							/* our special initial length */
diff --git a/gtk2_ardour/editor_audio_import.cc b/gtk2_ardour/editor_audio_import.cc
index 05056f3829..201659d7b4 100644
--- a/gtk2_ardour/editor_audio_import.cc
+++ b/gtk2_ardour/editor_audio_import.cc
@@ -29,6 +29,7 @@
 #include "pbd/pthread_utils.h"
 #include "pbd/basename.h"
 #include "pbd/shortpath.h"
+#include "pbd/stateful_diff_command.h"
 
 #include <gtkmm2ext/choice.h>
 
@@ -840,9 +841,9 @@ Editor::finish_bringing_in_material (boost::shared_ptr<Region> region, uint32_t
 		boost::shared_ptr<Playlist> playlist = existing_track->diskstream()->playlist();
 		boost::shared_ptr<Region> copy (RegionFactory::create (region, region->properties()));
 		begin_reversible_command (_("insert file"));
-		XMLNode &before = playlist->get_state();
+                playlist->clear_history ();
 		playlist->add_region (copy, pos);
-		_session->add_command (new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
+		_session->add_command (new StatefulDiffCommand (playlist));
 		commit_reversible_command ();
 		break;
 	}
diff --git a/gtk2_ardour/editor_drag.cc b/gtk2_ardour/editor_drag.cc
index 2922ad19bb..cd6e5148f6 100644
--- a/gtk2_ardour/editor_drag.cc
+++ b/gtk2_ardour/editor_drag.cc
@@ -1425,9 +1425,9 @@ RegionInsertDrag::finished (GdkEvent* /*event*/, bool /*movement_occurred*/)
 	boost::shared_ptr<Playlist> playlist = dest_rtv->playlist();
 
 	_editor->begin_reversible_command (_("insert region"));
-	XMLNode& before = playlist->get_state ();
+        playlist->clear_history ();
 	playlist->add_region (_primary->region (), _last_frame_position);
-	_editor->session()->add_command (new MementoCommand<Playlist> (*playlist, &before, &playlist->get_state()));
+	_editor->session()->add_command (new StatefulDiffCommand (playlist));
 	_editor->commit_reversible_command ();
 
 	delete _primary;
@@ -1772,7 +1772,8 @@ TrimDrag::motion (GdkEvent* event, bool first_move)
 
 		for (list<RegionView*>::const_iterator i = _views.begin(); i != _views.end(); ++i) {
 			(*i)->fake_set_opaque(false);
-			(*i)->region()->freeze ();
+                        (*i)->region()->clear_history ();
+			(*i)->region()->suspend_property_changes ();
 
 			AudioRegionView* const arv = dynamic_cast<AudioRegionView*>(*i);
 
@@ -1784,7 +1785,6 @@ TrimDrag::motion (GdkEvent* event, bool first_move)
 			insert_result = _editor->motion_frozen_playlists.insert (pl);
 
 			if (insert_result.second) {
-				_editor->session()->add_command(new MementoCommand<Playlist>(*pl, &pl->get_state(), 0));
 				pl->freeze();
 			}
 		}
@@ -1867,13 +1867,13 @@ TrimDrag::finished (GdkEvent* event, bool movement_occurred)
 			for (list<RegionView*>::const_iterator i = _views.begin(); i != _views.end(); ++i) {
 				_editor->thaw_region_after_trim (**i);
 				(*i)->fake_set_opaque (true);
+                                if (_have_transaction) {
+                                        _editor->session()->add_command (new StatefulDiffCommand ((*i)->region()));
+                                }
 			}
 		}
 		for (set<boost::shared_ptr<Playlist> >::iterator p = _editor->motion_frozen_playlists.begin(); p != _editor->motion_frozen_playlists.end(); ++p) {
 			(*p)->thaw ();
-			if (_have_transaction) {
-				_editor->session()->add_command (new MementoCommand<Playlist>(*(*p).get(), 0, &(*p)->get_state()));
-			}
 		}
 
 		_editor->motion_frozen_playlists.clear ();
diff --git a/gtk2_ardour/editor_keyboard.cc b/gtk2_ardour/editor_keyboard.cc
index ea40b43f50..e6936232cd 100644
--- a/gtk2_ardour/editor_keyboard.cc
+++ b/gtk2_ardour/editor_keyboard.cc
@@ -17,13 +17,14 @@
 
 */
 
+#include "pbd/memento_command.h"
+#include "pbd/stateful_diff_command.h"
+
 #include "ardour/audioregion.h"
 #include "ardour/playlist.h"
 #include "ardour/session.h"
 #include "ardour/location.h"
 
-#include "pbd/memento_command.h"
-
 #include "editor.h"
 #include "region_view.h"
 #include "selection.h"
@@ -33,6 +34,7 @@
 #include "i18n.h"
 
 using namespace ARDOUR;
+using namespace PBD;
 
 void
 Editor::kbd_driver (sigc::slot<void,GdkEvent*> theslot, bool use_track_canvas, bool use_time_canvas, bool can_select)
@@ -89,11 +91,9 @@ Editor::kbd_mute_unmute_region ()
 
 		for (RegionSelection::iterator i = selection->regions.begin(); i != selection->regions.end(); ++i) {
 
-			XMLNode &before = (*i)->region()->playlist()->get_state ();
+			(*i)->region()->playlist()->clear_history ();
 			(*i)->region()->set_muted (!(*i)->region()->muted ());
-			XMLNode &after = (*i)->region()->playlist()->get_state ();
-
-			_session->add_command (new MementoCommand<ARDOUR::Playlist>(*((*i)->region()->playlist()), &before, &after));
+			_session->add_command (new StatefulDiffCommand ((*i)->region()->playlist()));
 
 		}
 
@@ -102,12 +102,9 @@ Editor::kbd_mute_unmute_region ()
 	} else if (entered_regionview) {
 
 		begin_reversible_command (_("mute region"));
-		XMLNode &before = entered_regionview->region()->playlist()->get_state();
-
+                entered_regionview->region()->playlist()->clear_history ();
 		entered_regionview->region()->set_muted (!entered_regionview->region()->muted());
-
-		XMLNode &after = entered_regionview->region()->playlist()->get_state();
-		_session->add_command (new MementoCommand<ARDOUR::Playlist>(*(entered_regionview->region()->playlist()), &before, &after));
+		_session->add_command (new StatefulDiffCommand (entered_regionview->region()->playlist()));
 		commit_reversible_command();
 
 	}
diff --git a/gtk2_ardour/editor_mouse.cc b/gtk2_ardour/editor_mouse.cc
index 5820218a2a..ee28ff6804 100644
--- a/gtk2_ardour/editor_mouse.cc
+++ b/gtk2_ardour/editor_mouse.cc
@@ -31,6 +31,7 @@
 #include <gtkmm2ext/tearoff.h>
 #include "pbd/memento_command.h"
 #include "pbd/basename.h"
+#include "pbd/stateful_diff_command.h"
 
 #include "ardour_ui.h"
 #include "actions.h"
@@ -2287,23 +2288,17 @@ Editor::point_trim (GdkEvent* event, nframes64_t new_bound)
 				}
 
 				if (!(*i)->region()->locked()) {
-					boost::shared_ptr<Playlist> pl = (*i)->region()->playlist();
-					XMLNode &before = pl->get_state();
-
+					(*i)->region()->clear_history ();
 					(*i)->region()->trim_front (new_bound, this);
-
-					XMLNode &after = pl->get_state();
-					_session->add_command(new MementoCommand<Playlist>(*pl.get(), &before, &after));
+					_session->add_command(new StatefulDiffCommand ((*i)->region()));
 				}
 			}
 
 		} else {
 			if (!rv->region()->locked()) {
-				boost::shared_ptr<Playlist> pl = rv->region()->playlist();
-				XMLNode &before = pl->get_state();
+				rv->region()->clear_history ();
 				rv->region()->trim_front (new_bound, this);
-				XMLNode &after = pl->get_state();
-				_session->add_command(new MementoCommand<Playlist>(*pl.get(), &before, &after));
+				_session->add_command(new StatefulDiffCommand (rv->region()));
 			}
 		}
 
@@ -2318,22 +2313,18 @@ Editor::point_trim (GdkEvent* event, nframes64_t new_bound)
 			for (list<RegionView*>::const_iterator i = selection->regions.by_layer().begin(); i != selection->regions.by_layer().end(); ++i)
 			{
 				if (!(*i)->region()->locked()) {
-					boost::shared_ptr<Playlist> pl = (*i)->region()->playlist();
-					XMLNode &before = pl->get_state();
+					(*i)->region()->clear_history();
 					(*i)->region()->trim_end (new_bound, this);
-					XMLNode &after = pl->get_state();
-					_session->add_command(new MementoCommand<Playlist>(*pl.get(), &before, &after));
+					_session->add_command(new StatefulDiffCommand ((*i)->region()));
 				}
 			}
 
 		} else {
 
 			if (!rv->region()->locked()) {
-				boost::shared_ptr<Playlist> pl = rv->region()->playlist();
-				XMLNode &before = pl->get_state();
+				rv->region()->clear_history ();
 				rv->region()->trim_end (new_bound, this);
-				XMLNode &after = pl->get_state();
-				_session->add_command (new MementoCommand<Playlist>(*pl.get(), &before, &after));
+				_session->add_command (new StatefulDiffCommand (rv->region()));
 			}
 		}
 
@@ -2354,7 +2345,7 @@ Editor::thaw_region_after_trim (RegionView& rv)
 		return;
 	}
 
-	region->thaw ();
+	region->resume_property_changes ();
 
 	AudioRegionView* arv = dynamic_cast<AudioRegionView*>(&rv);
 
@@ -2453,11 +2444,10 @@ Editor::mouse_brush_insert_region (RegionView* rv, nframes64_t pos)
 	boost::shared_ptr<Playlist> playlist = rtv->playlist();
 	double speed = rtv->get_diskstream()->speed();
 
-	XMLNode &before = playlist->get_state();
+        playlist->clear_history ();
 	boost::shared_ptr<Region> new_region (RegionFactory::create (rv->region()));
-	playlist->add_region (new_region, (nframes64_t) (pos * speed));
-	XMLNode &after = playlist->get_state();
-	_session->add_command(new MementoCommand<Playlist>(*playlist.get(), &before, &after));
+        playlist->add_region (new_region, (nframes64_t) (pos * speed));
+	_session->add_command (new StatefulDiffCommand (playlist));
 
 	// playlist is frozen, so we have to update manually XXX this is disgusting
 
@@ -2560,10 +2550,9 @@ Editor::start_selection_grab (ArdourCanvas::Item* /*item*/, GdkEvent* event)
 
 	boost::shared_ptr<Playlist> playlist = clicked_axisview->playlist();
 
-	XMLNode *before = &(playlist->get_state());
+        playlist->clear_history ();
 	clicked_routeview->playlist()->add_region (region, selection->time[clicked_selection].start);
-	XMLNode *after = &(playlist->get_state());
-	_session->add_command(new MementoCommand<Playlist>(*playlist, before, after));
+	_session->add_command(new StatefulDiffCommand (playlist));
 
 	commit_reversible_command ();
 
diff --git a/gtk2_ardour/editor_ops.cc b/gtk2_ardour/editor_ops.cc
index c3800b21fb..6eaf1fb41a 100644
--- a/gtk2_ardour/editor_ops.cc
+++ b/gtk2_ardour/editor_ops.cc
@@ -323,10 +323,9 @@ Editor::nudge_forward (bool next, bool force_playhead)
 				distance = next_distance;
 			}
 
-                        XMLNode &before = r->playlist()->get_state();
+                        r->clear_history ();
 			r->set_position (r->position() + distance, this);
-                        XMLNode &after = r->playlist()->get_state();
-			_session->add_command (new MementoCommand<Playlist>(*(r->playlist()), &before, &after));
+			_session->add_command (new StatefulDiffCommand (r));
 		}
 
 		commit_reversible_command ();
@@ -403,16 +402,15 @@ Editor::nudge_backward (bool next, bool force_playhead)
 			if (next) {
 				distance = next_distance;
 			}
-
-                        XMLNode &before = r->playlist()->get_state();
+                        
+                        r->clear_history ();
 
 			if (r->position() > distance) {
 				r->set_position (r->position() - distance, this);
 			} else {
 				r->set_position (0, this);
 			}
-                        XMLNode &after = r->playlist()->get_state();
-			_session->add_command(new MementoCommand<Playlist>(*(r->playlist()), &before, &after));
+			_session->add_command (new StatefulDiffCommand (r));
 		}
 
 		commit_reversible_command ();
@@ -493,10 +491,9 @@ Editor::nudge_forward_capture_offset ()
 		for (RegionSelection::iterator i = rs.begin(); i != rs.end(); ++i) {
 			boost::shared_ptr<Region> r ((*i)->region());
 
-			XMLNode &before = r->playlist()->get_state();
+                        r->clear_history ();
 			r->set_position (r->position() + distance, this);
-			XMLNode &after = r->playlist()->get_state();
-			_session->add_command(new MementoCommand<Playlist>(*(r->playlist()), &before, &after));
+			_session->add_command(new StatefulDiffCommand (r));
 		}
 
 		commit_reversible_command ();
@@ -523,15 +520,14 @@ Editor::nudge_backward_capture_offset ()
 		for (RegionSelection::iterator i = rs.begin(); i != rs.end(); ++i) {
 			boost::shared_ptr<Region> r ((*i)->region());
 
-                        XMLNode &before = r->playlist()->get_state();
+                        r->clear_history ();
 
 			if (r->position() > distance) {
 				r->set_position (r->position() - distance, this);
 			} else {
 				r->set_position (0, this);
 			}
-                        XMLNode &after = r->playlist()->get_state();
-			_session->add_command(new MementoCommand<Playlist>(*(r->playlist()), &before, &after));
+			_session->add_command(new StatefulDiffCommand (r));
 		}
 
 		commit_reversible_command ();
@@ -2225,9 +2221,9 @@ Editor::insert_region_list_drag (boost::shared_ptr<Region> region, int x, int y)
 	snap_to (where);
 
 	begin_reversible_command (_("insert dragged region"));
-        XMLNode &before = playlist->get_state();
+        playlist->clear_history ();
 	playlist->add_region (RegionFactory::create (region), where, 1.0);
-	_session->add_command(new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
+	_session->add_command(new StatefulDiffCommand (playlist));
 	commit_reversible_command ();
 }
 
@@ -2303,9 +2299,9 @@ Editor::insert_region_list_selection (float times)
 	}
 
 	begin_reversible_command (_("insert region"));
-	XMLNode &before = playlist->get_state();
+        playlist->clear_history ();
 	playlist->add_region ((RegionFactory::create (region)), get_preferred_edit_position(), times);
-	_session->add_command(new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
+	_session->add_command(new StatefulDiffCommand (playlist));
 	commit_reversible_command ();
 }
 
@@ -2818,11 +2814,7 @@ Editor::separate_regions_between (const TimeSelection& ts)
 
 				if ((playlist = rtv->playlist()) != 0) {
 
-					XMLNode *before;
-					bool got_some;
-
-					before = &(playlist->get_state());
-					got_some = false;
+					playlist->clear_history ();
 
 					/* XXX need to consider musical time selections here at some point */
 
@@ -2842,25 +2834,18 @@ Editor::separate_regions_between (const TimeSelection& ts)
 
 						if (!latest_regionviews.empty()) {
 
-							got_some = true;
-
 							rtv->view()->foreach_regionview (sigc::bind (
 										sigc::ptr_fun (add_if_covered),
 										&(*t), &new_selection));
-
+                                                        
 							if (!in_command) {
 								begin_reversible_command (_("separate"));
 								in_command = true;
 							}
 
-							_session->add_command(new MementoCommand<Playlist>(
-									*playlist, before, &playlist->get_state()));
+							_session->add_command(new StatefulDiffCommand (playlist));
 						}
 					}
-
-					if (!got_some) {
-						delete before;
-					}
 				}
 			}
 		}
@@ -3022,10 +3007,9 @@ Editor::crop_region_to (nframes64_t start, nframes64_t end)
 		the_end = min (end, the_end);
 		cnt = the_end - the_start + 1;
 
-		XMLNode &before = (*i)->get_state();
+                region->clear_history ();
 		region->trim_to (the_start, cnt, this);
-		XMLNode &after = (*i)->get_state();
-		_session->add_command (new MementoCommand<Playlist>(*(*i), &before, &after));
+		_session->add_command (new StatefulDiffCommand (region));
 	}
 
 	commit_reversible_command ();
@@ -3063,9 +3047,9 @@ Editor::region_fill_track ()
 			return;
 		}
 
-		XMLNode &before = pl->get_state();
+                pl->clear_history ();
 		pl->add_region (RegionFactory::create (region), region->last_frame(), times);
-		_session->add_command (new MementoCommand<Playlist>(*pl, &before, &pl->get_state()));
+		_session->add_command (new StatefulDiffCommand (pl));
 	}
 
 	commit_reversible_command ();
@@ -3107,9 +3091,9 @@ Editor::region_fill_selection ()
 			continue;
 		}
 
-                XMLNode &before = playlist->get_state();
+                playlist->clear_history ();
 		playlist->add_region (RegionFactory::create (region), start, times);
-		_session->add_command (new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
+		_session->add_command (new StatefulDiffCommand (playlist));
 	}
 
 	commit_reversible_command ();
@@ -3142,10 +3126,9 @@ Editor::set_sync_point (nframes64_t where, const RegionSelection& rs)
 			in_command = true;
 		}
 
-		XMLNode &before = region->playlist()->get_state();
+                region->clear_history ();
 		region->set_sync_position (where);
-		XMLNode &after = region->playlist()->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*(region->playlist()), &before, &after));
+		_session->add_command(new StatefulDiffCommand (region));
 	}
 
 	if (in_command) {
@@ -3168,10 +3151,9 @@ Editor::remove_region_sync ()
 	begin_reversible_command (_("remove sync"));
 	for (RegionSelection::iterator i = rs.begin(); i != rs.end(); ++i) {
 
-                XMLNode &before = (*i)->region()->playlist()->get_state();
+                (*i)->region()->clear_history ();
 		(*i)->region()->clear_sync_position ();
-                XMLNode &after = (*i)->region()->playlist()->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*((*i)->region()->playlist()), &before, &after));
+		_session->add_command(new StatefulDiffCommand ((*i)->region()));
 	}
 	commit_reversible_command ();
 }
@@ -3290,10 +3272,9 @@ Editor::align_selection_relative (RegionPoint point, nframes64_t position, const
 
 	/* move first one specially */
 
-	XMLNode &before = r->playlist()->get_state();
+        r->clear_history ();
 	r->set_position (pos, this);
-	XMLNode &after = r->playlist()->get_state();
-	_session->add_command(new MementoCommand<Playlist>(*(r->playlist()), &before, &after));
+	_session->add_command(new StatefulDiffCommand (r));
 
 	/* move rest by the same amount */
 
@@ -3303,16 +3284,15 @@ Editor::align_selection_relative (RegionPoint point, nframes64_t position, const
 
 		boost::shared_ptr<Region> region ((*i)->region());
 
-                XMLNode &before = region->playlist()->get_state();
+                region->clear_history ();
 
 		if (dir > 0) {
 			region->set_position (region->position() + distance, this);
 		} else {
 			region->set_position (region->position() - distance, this);
 		}
-
-                XMLNode &after = region->playlist()->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*(region->playlist()), &before, &after));
+                
+		_session->add_command(new StatefulDiffCommand (region));
 
 	}
 
@@ -3346,7 +3326,7 @@ Editor::align_region (boost::shared_ptr<Region> region, RegionPoint point, nfram
 void
 Editor::align_region_internal (boost::shared_ptr<Region> region, RegionPoint point, nframes64_t position)
 {
-	XMLNode &before = region->playlist()->get_state();
+	region->clear_history ();
 
 	switch (point) {
 	case SyncPoint:
@@ -3364,8 +3344,7 @@ Editor::align_region_internal (boost::shared_ptr<Region> region, RegionPoint poi
 		break;
 	}
 
-	XMLNode &after = region->playlist()->get_state();
-	_session->add_command(new MementoCommand<Playlist>(*(region->playlist()), &before, &after));
+	_session->add_command(new StatefulDiffCommand (region));
 }
 
 void
@@ -3396,15 +3375,13 @@ Editor::trim_region (bool front)
 
 	for (list<RegionView*>::const_iterator i = rs.by_layer().begin(); i != rs.by_layer().end(); ++i) {
 		if (!(*i)->region()->locked()) {
-			boost::shared_ptr<Playlist> pl = (*i)->region()->playlist();
-			XMLNode &before = pl->get_state();
+                        (*i)->region()->clear_history ();
 			if (front) {
 				(*i)->region()->trim_front (where, this);
 			} else {
 				(*i)->region()->trim_end (where, this);
 			}
-			XMLNode &after = pl->get_state();
-			_session->add_command(new MementoCommand<Playlist>(*pl.get(), &before, &after));
+			_session->add_command (new StatefulDiffCommand ((*i)->region()));
 		}
 	}
 
@@ -3466,12 +3443,10 @@ Editor::trim_region_to_location (const Location& loc, const char* str)
 
 		start = session_frame_to_track_frame (loc.start(), speed);
 		end = session_frame_to_track_frame (loc.end(), speed);
-
-		XMLNode &before = rv->region()->playlist()->get_state();
+                
+		rv->region()->clear_history ();
 		rv->region()->trim_to (start, (end - start), this);
-		XMLNode &after = rv->region()->playlist()->get_state();
-		_session->add_command(new MementoCommand<Playlist>(
-				*(rv->region()->playlist()), &before, &after));
+		_session->add_command(new StatefulDiffCommand (rv->region()));
 	}
 
 	commit_reversible_command ();
@@ -3507,11 +3482,9 @@ Editor::trim_region_to_edit_point ()
 			speed = tav->get_diskstream()->speed();
 		}
 
-		XMLNode &before = rv->region()->playlist()->get_state();
+                rv->region()->clear_history ();
 		rv->region()->trim_end (session_frame_to_track_frame(where, speed), this);
-		XMLNode &after = rv->region()->playlist()->get_state();
-		_session->add_command(new MementoCommand<Playlist>(
-				*(rv->region()->playlist()), &before, &after));
+		_session->add_command(new StatefulDiffCommand (rv->region()));
 	}
 
 	commit_reversible_command ();
@@ -3547,11 +3520,9 @@ Editor::trim_region_from_edit_point ()
 			speed = tav->get_diskstream()->speed();
 		}
 
-		XMLNode &before = rv->region()->playlist()->get_state();
+                rv->region()->clear_history ();
 		rv->region()->trim_front (session_frame_to_track_frame(where, speed), this);
-		XMLNode &after = rv->region()->playlist()->get_state();
-		_session->add_command(new MementoCommand<Playlist>(
-				*(rv->region()->playlist()), &before, &after));
+		_session->add_command(new StatefulDiffCommand (rv->region()));
 	}
 
 	commit_reversible_command ();
@@ -3604,7 +3575,7 @@ Editor::trim_to_region(bool forward)
 		boost::shared_ptr<Region> region = arv->region();
 		boost::shared_ptr<Playlist> playlist (region->playlist());
 
-		XMLNode &before = playlist->get_state();
+                region->clear_history ();
 
 		if(forward){
 
@@ -3630,8 +3601,7 @@ Editor::trim_to_region(bool forward)
 		    arv->region_changed (ARDOUR::bounds_change);
 		}
 
-		XMLNode &after = playlist->get_state();
-		_session->add_command(new MementoCommand<Playlist>(*playlist, &before, &after));
+		_session->add_command(new StatefulDiffCommand (region));
 	}
 
 	commit_reversible_command ();
@@ -3658,7 +3628,7 @@ Editor::_freeze_thread (void* arg)
 void*
 Editor::freeze_thread ()
 {
-	clicked_routeview->audio_track()->freeze (*current_interthread_info);
+	clicked_routeview->audio_track()->freeze_me (*current_interthread_info);
 	current_interthread_info->done = true;
 	return 0;
 }
@@ -3747,7 +3717,7 @@ Editor::bounce_range_selection (bool replace, bool enable_processing)
 		itt.cancel = false;
 		itt.progress = false;
 
-                XMLNode &before = playlist->get_state();
+                playlist->clear_history ();
 		boost::shared_ptr<Region> r = rtv->track()->bounce_range (start, start+cnt, itt, enable_processing);
 
 		if (replace) {
@@ -3757,8 +3727,7 @@ Editor::bounce_range_selection (bool replace, bool enable_processing)
 			playlist->add_region (r, start);
 		}
 
-                XMLNode &after = playlist->get_state();
-		_session->add_command (new MementoCommand<Playlist> (*playlist, &before, &after));
+		_session->add_command (new StatefulDiffCommand (playlist));
 	}
 
 	commit_reversible_command ();
@@ -3994,10 +3963,9 @@ Editor::remove_clicked_region ()
 	boost::shared_ptr<Playlist> playlist = clicked_routeview->playlist();
 
 	begin_reversible_command (_("remove region"));
-        XMLNode &before = playlist->get_state();
+        playlist->clear_history ();
 	playlist->remove_region (clicked_regionview->region());
-        XMLNode &after = playlist->get_state();
-	_session->add_command(new MementoCommand<Playlist>(*playlist, &before, &after));
+	_session->add_command(new StatefulDiffCommand (playlist));
 	commit_reversible_command ();
 }
 
@@ -4034,7 +4002,7 @@ Editor::remove_selected_regions ()
 		regions_to_remove.push_back ((*i)->region());
 	}
 
-	vector<PlaylistState> playlists;
+        vector<boost::shared_ptr<Playlist> > playlists;
 
 	for (list<boost::shared_ptr<Region> >::iterator rl = regions_to_remove.begin(); rl != regions_to_remove.end(); ++rl) {
 
@@ -4045,33 +4013,31 @@ Editor::remove_selected_regions ()
 	        	continue;
 	        }
 
-		vector<PlaylistState>::iterator i;
+		vector<boost::shared_ptr<Playlist> >::iterator i;
 
-		//only take state if this is a new playlist.
+		//only prep history if this is a new playlist.
 		for (i = playlists.begin(); i != playlists.end(); ++i) {
-			if ((*i).playlist == playlist) {
+			if ((*i) == playlist) {
 				break;
 			}
 		}
 
 		if (i == playlists.end()) {
 
-			PlaylistState before;
-			before.playlist = playlist;
-			before.before = &playlist->get_state();
-
+                        playlist->clear_history ();
 			playlist->freeze ();
-			playlists.push_back(before);
+
+			playlists.push_back (playlist);
 		}
 
 		playlist->remove_region (*rl);
 	}
 
-	vector<PlaylistState>::iterator pl;
+	vector<boost::shared_ptr<Playlist> >::iterator pl;
 
 	for (pl = playlists.begin(); pl != playlists.end(); ++pl) {
-		(*pl).playlist->thaw ();
-		_session->add_command(new MementoCommand<Playlist>(*(*pl).playlist, (*pl).before, &(*pl).playlist->get_state()));
+		(*pl)->thaw ();
+		_session->add_command(new StatefulDiffCommand (*pl));
 	}
 
 	commit_reversible_command ();
@@ -4351,9 +4317,9 @@ Editor::duplicate_some_regions (RegionSelection& regions, float times)
 		sigc::connection c = rtv->view()->RegionViewAdded.connect (sigc::mem_fun(*this, &Editor::collect_new_region_view));
 
  		playlist = (*i)->region()->playlist();
-                XMLNode &before = playlist->get_state();
+                playlist->clear_history ();
 		playlist->duplicate (r, end_frame + (r->first_frame() - start_frame) + 1, times);
-		_session->add_command(new MementoCommand<Playlist>(*playlist, &before, &playlist->get_state()));
+		_session->add_command(new StatefulDiffCommand (playlist));
 
 		c.disconnect ();
 
@@ -4392,10 +4358,9 @@ Editor::duplicate_selection (float times)
 		if ((playlist = (*i)->playlist()) == 0) {
 			continue;
 		}
-		XMLNode &before = playlist->get_state();
+                playlist->clear_history ();
 		playlist->duplicate (*ri, selection->time[clicked_selection].end, times);
-		XMLNode &after = playlist->get_state();
-		_session->add_command (new MementoCommand<Playlist>(*playlist, &before, &after));
+		_session->add_command (new StatefulDiffCommand (playlist));
 
 		++ri;
 		if (ri == new_regions.end()) {
@@ -4439,10 +4404,9 @@ void
 Editor::clear_playlist (boost::shared_ptr<Playlist> playlist)
 {
 	begin_reversible_command (_("clear playlist"));
-        XMLNode &before = playlist->get_state();
+        playlist->clear_history ();
 	playlist->clear ();
-        XMLNode &after = playlist->get_state();
-	_session->add_command (new MementoCommand<Playlist>(*playlist.get(), &before, &after));
+	_session->add_command (new StatefulDiffCommand (playlist));
 	commit_reversible_command ();
 }
 
@@ -4476,6 +4440,9 @@ Editor::nudge_track (bool use_edit, bool forwards)
 			continue;
 		}
 
+                /* XXX STATEFUL this won't capture region moves if don't as a stateful diff
+                 */
+
                 XMLNode &before = playlist->get_state();
 		playlist->nudge_after (start, distance, forwards);
                 XMLNode &after = playlist->get_state();
@@ -4555,9 +4522,10 @@ Editor::normalize_region ()
 		AudioRegionView* const arv = dynamic_cast<AudioRegionView*>(*r);
 		if (!arv)
 			continue;
- 		XMLNode &before = arv->region()->get_state();
+                arv->region()->clear_history ();
 		arv->audio_region()->normalize_to (spin.get_value());
-		_session->add_command (new MementoCommand<Region>(*(arv->region().get()), &before, &arv->region()->get_state()));
+		_session->add_command (new StatefulDiffCommand (arv->region()));
+                                       
 	}
 
 	commit_reversible_command ();
@@ -4588,9 +4556,9 @@ Editor::reset_region_scale_amplitude ()
 		AudioRegionView* const arv = dynamic_cast<AudioRegionView*>(*r);
 		if (!arv)
 			continue;
-		XMLNode &before = arv->region()->get_state();
+                arv->region()->clear_history ();
 		arv->audio_region()->set_scale_amplitude (1.0f);
-		_session->add_command (new MementoCommand<Region>(*(arv->region().get()), &before, &arv->region()->get_state()));
+		_session->add_command (new StatefulDiffCommand (arv->region()));
 	}
 
 	commit_reversible_command ();
@@ -4615,10 +4583,12 @@ Editor::adjust_region_scale_amplitude (bool up)
 
 	for (RegionSelection::iterator r = rs.begin(); r != rs.end(); ++r) {
 		AudioRegionView* const arv = dynamic_cast<AudioRegionView*>(*r);
-		if (!arv)
+		if (!arv) {
 			continue;
-		XMLNode &before = arv->region()->get_state();
+                }
 
+                arv->region()->clear_history ();
+                
 		double fraction = gain_to_slider_position (arv->audio_region()->scale_amplitude ());
 
 		if (up) {
@@ -4640,7 +4610,7 @@ Editor::adjust_region_scale_amplitude (bool up)
 		}
 
 		arv->audio_region()->set_scale_amplitude (fraction);
-		_session->add_command (new MementoCommand<Region>(*(arv->region().get()), &before, &arv->region()->get_state()));
+		_session->add_command (new StatefulDiffCommand (arv->region()));
 	}
 
 	commit_reversible_command ();
@@ -4786,8 +4756,8 @@ Editor::apply_filter (Filter& filter, string command)
 
 			if (arv->audio_region()->apply (filter) == 0) {
 
-				XMLNode &before = playlist->get_state();
-
+				playlist->clear_history ();
+                                
 				if (filter.results.empty ()) {
 
 					/* no regions returned; remove the old one */
@@ -4809,8 +4779,7 @@ Editor::apply_filter (Filter& filter, string command)
 
 				}
 
-				XMLNode &after = playlist->get_state();
-				_session->add_command(new MementoCommand<Playlist>(*playlist, &before, &after));
+				_session->add_command(new StatefulDiffCommand (playlist));
 			} else {
 				goto out;
 			}
@@ -4918,10 +4887,9 @@ Editor::toggle_gain_envelope_visibility ()
 	for (RegionSelection::iterator i = rs.begin(); i != rs.end(); ++i) {
 		AudioRegionView* const arv = dynamic_cast<AudioRegionView*>(*i);
 		if (arv) {
-			XMLNode &before = arv->region()->get_state ();
+                        arv->region()->clear_history ();
 			arv->set_envelope_visible (!arv->envelope_visible());
-			XMLNode &after = arv->region()->get_state ();
-			_session->add_command (new MementoCommand<Region> (*(arv->region().get()), &before, &after));
+			_session->add_command (new StatefulDiffCommand (arv->region()));
 		}
 	}
 
@@ -4983,10 +4951,9 @@ Editor::set_region_lock_style (Region::PositionLockStyle ps)
 	_session->begin_reversible_command (_("region lock style"));
 
 	for (RegionSelection::iterator i = rs.begin(); i != rs.end(); ++i) {
-		XMLNode &before = (*i)->region()->get_state ();
+                (*i)->region()->clear_history ();
 		(*i)->region()->set_position_lock_style (ps);
-		XMLNode &after = (*i)->region()->get_state ();
-		_session->add_command (new MementoCommand<Region> (*((*i)->region().get()), &before, &after));
+		_session->add_command (new StatefulDiffCommand ((*i)->region()));
 	}
 
 	_session->commit_reversible_command ();
@@ -5165,14 +5132,15 @@ Editor::toggle_fade_active (bool in)
 			have_switch = true;
 		}
 
-		XMLNode &before = region->get_state();
+		region->clear_history ();
+
 		if (in) {
 			region->set_fade_in_active (!yn);
 		} else {
 			region->set_fade_out_active (!yn);
 		}
-		XMLNode &after = region->get_state();
-		_session->add_command(new MementoCommand<AudioRegion>(*region.get(), &before, &after));
+		
+		_session->add_command(new StatefulDiffCommand (region));
 	}
 
 	commit_reversible_command ();
@@ -5265,13 +5233,10 @@ Editor::set_fade_in_active (bool yn)
 
 
 		boost::shared_ptr<AudioRegion> ar (tmp->audio_region());
-
-		XMLNode &before = ar->get_state();
-
+		
+                ar->clear_history ();
 		ar->set_fade_in_active (yn);
-
-		XMLNode &after = ar->get_state();
-		_session->add_command(new MementoCommand<AudioRegion>(*ar, &before, &after));
+		_session->add_command (new StatefulDiffCommand (ar));
 	}
 
 	commit_reversible_command ();
@@ -5299,12 +5264,9 @@ Editor::set_fade_out_active (bool yn)
 
 		boost::shared_ptr<AudioRegion> ar (tmp->audio_region());
 
-		XMLNode &before = ar->get_state();
-
+                ar->clear_history ();
 		ar->set_fade_out_active (yn);
-
-		XMLNode &after = ar->get_state();
-		_session->add_command(new MementoCommand<AudioRegion>(*ar, &before, &after));
+		_session->add_command(new StatefulDiffCommand (ar));
 	}
 
 	commit_reversible_command ();
@@ -5925,7 +5887,7 @@ Editor::split_region_at_points (boost::shared_ptr<Region> r, AnalysisFeatureList
 
 	nframes64_t pos = r->position();
 
-	XMLNode& before (pl->get_state());
+        pl->clear_history ();
 
 	x = positions.begin();
 
@@ -6007,9 +5969,7 @@ Editor::split_region_at_points (boost::shared_ptr<Region> r, AnalysisFeatureList
 
 	pl->thaw ();
 
-	XMLNode& after (pl->get_state());
-
-	_session->add_command (new MementoCommand<Playlist>(*pl, &before, &after));
+	_session->add_command (new StatefulDiffCommand (pl));
 }
 
 void
@@ -6330,6 +6290,9 @@ Editor::insert_time (nframes64_t pos, nframes64_t frames, InsertTimeOption opt,
 
 		if (pl) {
 
+                        /* XXX STATEFUL this won't capture region motion if done as stateful diff 
+                         */
+
 			XMLNode &before = pl->get_state();
 
 			if (opt == SplitIntersected) {
diff --git a/gtk2_ardour/editor_timefx.cc b/gtk2_ardour/editor_timefx.cc
index aab6b67658..fcd7e9baf4 100644
--- a/gtk2_ardour/editor_timefx.cc
+++ b/gtk2_ardour/editor_timefx.cc
@@ -26,6 +26,7 @@
 #include "pbd/error.h"
 #include "pbd/pthread_utils.h"
 #include "pbd/memento_command.h"
+#include "pbd/stateful_diff_command.h"
 
 #include <gtkmm2ext/utils.h>
 
@@ -80,11 +81,10 @@ Editor::time_stretch (RegionSelection& regions, float fraction)
 		MidiStretch stretch(*_session, request);
 		begin_reversible_command ("midi stretch");
 		stretch.run(regions.front()->region());
-		XMLNode &before = playlist->get_state();
+                playlist->clear_history ();
 		playlist->replace_region (regions.front()->region(), stretch.results[0],
 				regions.front()->region()->position());
-		XMLNode &after = playlist->get_state();
-		_session->add_command (new MementoCommand<Playlist>(*playlist, &before, &after));
+		_session->add_command (new StatefulDiffCommand (playlist));
 		commit_reversible_command ();
 	}
 
@@ -315,10 +315,9 @@ Editor::do_timefx (TimeFXDialog& dialog)
 				in_command = true;
 			}
 
-			XMLNode &before = playlist->get_state();
+                        playlist->clear_history ();
 			playlist->replace_region (region, new_region, region->position());
-			XMLNode &after = playlist->get_state();
-			_session->add_command (new MementoCommand<Playlist>(*playlist, &before, &after));
+			_session->add_command (new StatefulDiffCommand (playlist));
 		}
 
 		i = tmp;
diff --git a/gtk2_ardour/midi_region_view.cc b/gtk2_ardour/midi_region_view.cc
index 4ea7aba4fa..aec77df8c0 100644
--- a/gtk2_ardour/midi_region_view.cc
+++ b/gtk2_ardour/midi_region_view.cc
@@ -29,6 +29,7 @@
 #include <sigc++/signal.h>
 
 #include "pbd/memento_command.h"
+#include "pbd/stateful_diff_command.h"
 
 #include "ardour/playlist.h"
 #include "ardour/tempo.h"
@@ -2530,9 +2531,9 @@ MidiRegionView::paste (nframes64_t pos, float times, const MidiCutBuffer& mcb)
 
 		trackview.session()->begin_reversible_command (_("paste"));
 
-		XMLNode& before (_region->get_state());
+                _region->clear_history ();
 		_region->set_length (end_frame, this);
-		trackview.session()->add_command (new MementoCommand<Region>(*_region, &before, &_region->get_state()));
+		trackview.session()->add_command (new StatefulDiffCommand (_region));
 	}
 
 	apply_delta ();
diff --git a/gtk2_ardour/midi_streamview.cc b/gtk2_ardour/midi_streamview.cc
index 19c1a53b39..1ca63d0f53 100644
--- a/gtk2_ardour/midi_streamview.cc
+++ b/gtk2_ardour/midi_streamview.cc
@@ -558,10 +558,10 @@ MidiStreamView::update_rec_regions (boost::shared_ptr<MidiModel> data, nframes_t
 
 					if (nlen != region->length()) {
 
-						region->freeze ();
+						region->suspend_property_changes ();
 						region->set_position (_trackview.get_diskstream()->get_capture_start_frame(n), this);
 						region->set_length (start + dur - region->position(), this);
-						region->thaw ();
+						region->resume_property_changes ();
 
 						if (origlen == 1) {
 							/* our special initial length */
@@ -622,10 +622,10 @@ MidiStreamView::update_rec_regions (boost::shared_ptr<MidiModel> data, nframes_t
 
 					if (region->source_length(0) >= region->position() + nlen) {
 
-						region->freeze ();
+						region->suspend_property_changes ();
 						region->set_position (_trackview.get_diskstream()->get_capture_start_frame(n), this);
 						region->set_length (nlen, this);
-						region->thaw ();
+						region->resume_property_changes ();
 
 						if (origlen == 1) {
 							/* our special initial length */
diff --git a/gtk2_ardour/midi_time_axis.cc b/gtk2_ardour/midi_time_axis.cc
index b1adb7c67e..5949541e56 100644
--- a/gtk2_ardour/midi_time_axis.cc
+++ b/gtk2_ardour/midi_time_axis.cc
@@ -31,6 +31,7 @@
 #include "pbd/basename.h"
 #include "pbd/enumwriter.h"
 #include "pbd/memento_command.h"
+#include "pbd/stateful_diff_command.h"
 
 #include <gtkmm2ext/gtk_ui.h>
 #include <gtkmm2ext/selector.h>
@@ -966,7 +967,7 @@ MidiTimeAxisView::add_region (nframes64_t pos)
 	Editor* real_editor = dynamic_cast<Editor*> (&_editor);
 
 	real_editor->begin_reversible_command (_("create region"));
-	XMLNode &before = playlist()->get_state();
+        playlist()->clear_history ();
 
 	framepos_t start = pos;
 	real_editor->snap_to (start, -1);
@@ -988,8 +989,7 @@ MidiTimeAxisView::add_region (nframes64_t pos)
 	boost::shared_ptr<Region> region = (RegionFactory::create (src, plist));
 
 	playlist()->add_region (region, start);
-	XMLNode &after = playlist()->get_state();
-	_session->add_command (new MementoCommand<Playlist> (*playlist().get(), &before, &after));
+	_session->add_command (new StatefulDiffCommand (playlist()));
 
 	real_editor->commit_reversible_command();
 
diff --git a/gtk2_ardour/region_gain_line.cc b/gtk2_ardour/region_gain_line.cc
index 827562524e..30e19ec24a 100644
--- a/gtk2_ardour/region_gain_line.cc
+++ b/gtk2_ardour/region_gain_line.cc
@@ -19,6 +19,7 @@
 
 #include "evoral/Curve.hpp"
 #include "pbd/memento_command.h"
+#include "pbd/stateful_diff_command.h"
 
 #include "ardour/audioregion.h"
 #include "ardour/session.h"
@@ -53,6 +54,8 @@ void
 AudioRegionGainLine::start_drag_single (ControlPoint* cp, double x, float fraction)
 {
 	AutomationLine::start_drag_single (cp, x, fraction);
+
+        // XXX Stateful need to capture automation curve data
 	
 	if (!rv.audio_region()->envelope_active()) {
 		trackview.session()->add_command(new MementoCommand<AudioRegion>(*(rv.audio_region().get()), &rv.audio_region()->get_state(), 0));
@@ -72,10 +75,9 @@ AudioRegionGainLine::remove_point (ControlPoint& cp)
 	XMLNode &before = alist->get_state();
 
 	if (!rv.audio_region()->envelope_active()) {
-		XMLNode &region_before = rv.audio_region()->get_state();
+                rv.audio_region()->clear_history ();
 		rv.audio_region()->set_envelope_active(true);
-		XMLNode &region_after = rv.audio_region()->get_state();
-		trackview.session()->add_command(new MementoCommand<AudioRegion>(*(rv.audio_region().get()), &region_before, &region_after));
+		trackview.session()->add_command(new StatefulDiffCommand (rv.audio_region()));
 	}
 
 	alist->erase (mr.start, mr.end);