Move ARDOUR::Change into PBD so that Stateful can be aware of

what Change a State reflects.  Hence allow Stateful to do some
of the work of set/get_state in Region.


git-svn-id: svn://localhost/ardour2/branches/3.0@6671 d708f5d6-7413-0410-9779-e7cbd77b26cf

30 files changed, 203 insertions, 171 deletions

diff --git a/gtk2_ardour/audio_region_editor.cc b/gtk2_ardour/audio_region_editor.cc
index 4ddf7ad0b7..3d29ed6b47 100644
--- a/gtk2_ardour/audio_region_editor.cc
+++ b/gtk2_ardour/audio_region_editor.cc
@@ -167,7 +167,7 @@ AudioRegionEditor::~AudioRegionEditor ()
 }
 
 void
-AudioRegionEditor::region_changed (Change what_changed)
+AudioRegionEditor::region_changed (PBD::Change what_changed)
 {
 	if (what_changed & NameChanged) {
 		name_changed ();
diff --git a/gtk2_ardour/audio_region_editor.h b/gtk2_ardour/audio_region_editor.h
index 0450d0c293..af9d1b057b 100644
--- a/gtk2_ardour/audio_region_editor.h
+++ b/gtk2_ardour/audio_region_editor.h
@@ -98,8 +98,8 @@ class AudioRegionEditor : public RegionEditor
 	PBD::ScopedConnection state_connection;
 	PBD::ScopedConnection audition_connection;
 
-	void region_changed (ARDOUR::Change);
-	void bounds_changed (ARDOUR::Change);
+	void region_changed (PBD::Change);
+	void bounds_changed (PBD::Change);
 	void name_changed ();
 	void gain_changed ();
 
diff --git a/gtk2_ardour/audio_region_view.h b/gtk2_ardour/audio_region_view.h
index 9fe658f877..87e5d23327 100644
--- a/gtk2_ardour/audio_region_view.h
+++ b/gtk2_ardour/audio_region_view.h
@@ -98,7 +98,7 @@ class AudioRegionView : public RegionView
 
 	AudioRegionGainLine* get_gain_line() const { return gain_line; }
 
-	void region_changed (ARDOUR::Change);
+	void region_changed (PBD::Change);
 	void envelope_active_changed ();
 
 	GhostRegion* add_ghost (TimeAxisView&);
@@ -150,7 +150,7 @@ class AudioRegionView : public RegionView
     void fade_in_active_changed ();
     void fade_out_active_changed ();
 
-    void region_resized (ARDOUR::Change);
+    void region_resized (PBD::Change);
     void region_muted ();
     void region_scale_amplitude_changed ();
 	void region_renamed ();
diff --git a/gtk2_ardour/automation_region_view.cc b/gtk2_ardour/automation_region_view.cc
index 5e13ee55fd..f1000d7159 100644
--- a/gtk2_ardour/automation_region_view.cc
+++ b/gtk2_ardour/automation_region_view.cc
@@ -158,7 +158,7 @@ AutomationRegionView::reset_width_dependent_items (double pixel_width)
 
 
 void
-AutomationRegionView::region_resized (ARDOUR::Change what_changed)
+AutomationRegionView::region_resized (PBD::Change what_changed)
 {
 	RegionView::region_resized(what_changed);
 
diff --git a/gtk2_ardour/automation_region_view.h b/gtk2_ardour/automation_region_view.h
index 5219fd7dc6..b4f53b5921 100644
--- a/gtk2_ardour/automation_region_view.h
+++ b/gtk2_ardour/automation_region_view.h
@@ -66,7 +66,7 @@ public:
 protected:
 	void create_line(boost::shared_ptr<ARDOUR::AutomationList> list);
 	bool set_position(nframes64_t pos, void* src, double* ignored);
-	void region_resized(ARDOUR::Change what_changed);
+	void region_resized (PBD::Change what_changed);
 	bool canvas_event(GdkEvent* ev);
 	void add_automation_event (GdkEvent* event, nframes_t when, double y);
 	void entered();
diff --git a/gtk2_ardour/crossfade_edit.h b/gtk2_ardour/crossfade_edit.h
index 29a66b3747..d92288e650 100644
--- a/gtk2_ardour/crossfade_edit.h
+++ b/gtk2_ardour/crossfade_edit.h
@@ -213,7 +213,7 @@ class CrossfadeEditor : public ArdourDialog
 	void audition_right_dry ();
 	void audition_right ();
 
-	void xfade_changed (ARDOUR::Change);
+	void xfade_changed (PBD::Change);
 
 	void dump ();
 };
diff --git a/gtk2_ardour/crossfade_view.h b/gtk2_ardour/crossfade_view.h
index 2376f81edc..e141a30cb1 100644
--- a/gtk2_ardour/crossfade_view.h
+++ b/gtk2_ardour/crossfade_view.h
@@ -75,7 +75,7 @@ struct CrossfadeView : public TimeAxisViewItem
     ArdourCanvas::Line *fade_out;
     ArdourCanvas::Item *active_button;
 
-    void crossfade_changed (ARDOUR::Change);
+    void crossfade_changed (PBD::Change);
     void active_changed ();
 	void redraw_curves ();
 	void color_handler ();
diff --git a/gtk2_ardour/editor.h b/gtk2_ardour/editor.h
index 1faaa43bf6..49742c6f45 100644
--- a/gtk2_ardour/editor.h
+++ b/gtk2_ardour/editor.h
@@ -520,7 +520,7 @@ class Editor : public PublicEditor, public PBD::ScopedConnectionList, public ARD
 	void location_changed (ARDOUR::Location *);
 	void location_flags_changed (ARDOUR::Location *, void *);
 	void refresh_location_display ();
-	void refresh_location_display_s (ARDOUR::Change);
+	void refresh_location_display_s (PBD::Change);
 	void refresh_location_display_internal (ARDOUR::Locations::LocationList&);
 	void add_new_location (ARDOUR::Location *);
 	void location_gone (ARDOUR::Location *);
@@ -1475,7 +1475,7 @@ public:
 	void draw_metric_marks (const ARDOUR::Metrics& metrics);
 
 	void compute_current_bbt_points (nframes_t left, nframes_t right);
-	void tempo_map_changed (ARDOUR::Change);
+	void tempo_map_changed (PBD::Change);
 	void redisplay_tempo (bool immediate_redraw);
 
 	void snap_to (nframes64_t& first, int32_t direction = 0, bool for_mark = false);
diff --git a/gtk2_ardour/editor_regions.h b/gtk2_ardour/editor_regions.h
index 5a9c2aad5a..5a31eb2fd2 100644
--- a/gtk2_ardour/editor_regions.h
+++ b/gtk2_ardour/editor_regions.h
@@ -104,7 +104,7 @@ private:
 
 	Columns _columns;
 
-	void region_changed (ARDOUR::Change, boost::weak_ptr<ARDOUR::Region>);
+	void region_changed (PBD::Change, boost::weak_ptr<ARDOUR::Region>);
 	void selection_changed ();
 	sigc::connection _change_connection;
 	bool set_selected_in_subrow (boost::shared_ptr<ARDOUR::Region>, Gtk::TreeModel::Row const &, int);
diff --git a/gtk2_ardour/midi_region_view.h b/gtk2_ardour/midi_region_view.h
index 77e046d9cd..bc34416a03 100644
--- a/gtk2_ardour/midi_region_view.h
+++ b/gtk2_ardour/midi_region_view.h
@@ -305,7 +305,7 @@ class MidiRegionView : public RegionView
 	                Gdk::Color& basic_color,
 	                TimeAxisViewItem::Visibility);
 
-	void region_resized (ARDOUR::Change);
+	void region_resized (PBD::Change);
 
 	void set_flags (XMLNode *);
 	void store_flags ();
diff --git a/gtk2_ardour/region_view.h b/gtk2_ardour/region_view.h
index 9a663eac02..172405d132 100644
--- a/gtk2_ardour/region_view.h
+++ b/gtk2_ardour/region_view.h
@@ -75,7 +75,7 @@ class RegionView : public TimeAxisViewItem
 	virtual void show_region_editor () {}
 	virtual void hide_region_editor();
 
-	virtual void region_changed (ARDOUR::Change);
+	virtual void region_changed (PBD::Change);
 
 	virtual GhostRegion* add_ghost (TimeAxisView&) = 0;
 	void remove_ghost_in (TimeAxisView&);
@@ -104,7 +104,7 @@ class RegionView : public TimeAxisViewItem
 		bool recording,
 		TimeAxisViewItem::Visibility);
 
-    virtual void region_resized (ARDOUR::Change);
+    virtual void region_resized (PBD::Change);
     virtual void region_muted ();
     void         region_locked ();
     void         region_opacity ();
diff --git a/libs/ardour/ardour/ardour.h b/libs/ardour/ardour/ardour.h
index e98d85c433..a7b3bcafd0 100644
--- a/libs/ardour/ardour/ardour.h
+++ b/libs/ardour/ardour/ardour.h
@@ -31,6 +31,7 @@
 #include "pbd/error.h"
 #include "pbd/failed_constructor.h"
 #include "pbd/locale_guard.h"
+#include "pbd/stateful.h"
 
 #include "ardour/types.h"
 
@@ -64,13 +65,11 @@ namespace ARDOUR {
 		return (microseconds_t) jack_get_time();
 	}
 
-	Change new_change ();
-
-	extern Change StartChanged;
-	extern Change LengthChanged;
-	extern Change PositionChanged;
-	extern Change NameChanged;
-	extern Change BoundsChanged;
+	extern PBD::Change StartChanged;
+	extern PBD::Change LengthChanged;
+	extern PBD::Change PositionChanged;
+	extern PBD::Change NameChanged;
+	extern PBD::Change BoundsChanged;
 
 	static const double SHUTTLE_FRACT_SPEED1=0.48412291827; /* derived from A1,A2 */
 
diff --git a/libs/ardour/ardour/audioplaylist.h b/libs/ardour/ardour/audioplaylist.h
index 9dd133cbc0..ce7c8aa335 100644
--- a/libs/ardour/ardour/audioplaylist.h
+++ b/libs/ardour/ardour/audioplaylist.h
@@ -79,8 +79,8 @@ class AudioPlaylist : public ARDOUR::Playlist
        XMLNode& state (bool full_state);
        void dump () const;
 
-       bool region_changed (Change, boost::shared_ptr<Region>);
-       void crossfade_changed (Change);
+       bool region_changed (PBD::Change, boost::shared_ptr<Region>);
+       void crossfade_changed (PBD::Change);
        void add_crossfade (boost::shared_ptr<Crossfade>);
 
        void source_offset_changed (boost::shared_ptr<AudioRegion> region);
diff --git a/libs/ardour/ardour/audioregion.h b/libs/ardour/ardour/audioregion.h
index 8b95881dc2..3f1e4cf9e3 100644
--- a/libs/ardour/ardour/audioregion.h
+++ b/libs/ardour/ardour/audioregion.h
@@ -45,13 +45,13 @@ class AudioSource;
 class AudioRegion : public Region
 {
   public:
-	static Change FadeInChanged;
-	static Change FadeOutChanged;
-	static Change FadeInActiveChanged;
-	static Change FadeOutActiveChanged;
-	static Change EnvelopeActiveChanged;
-	static Change ScaleAmplitudeChanged;
-	static Change EnvelopeChanged;
+	static PBD::Change FadeInChanged;
+	static PBD::Change FadeOutChanged;
+	static PBD::Change FadeInActiveChanged;
+	static PBD::Change FadeOutActiveChanged;
+	static PBD::Change EnvelopeActiveChanged;
+	static PBD::Change ScaleAmplitudeChanged;
+	static PBD::Change EnvelopeChanged;
 
 	~AudioRegion();
 
@@ -219,7 +219,7 @@ class AudioRegion : public Region
 
 	AudioRegion (Session& s, nframes_t, nframes_t, std::string name);
 
-	int set_live_state (const XMLNode&, int version, Change&, bool send);
+	int set_live_state (const XMLNode&, int version, PBD::Change&, bool send);
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/crossfade.h b/libs/ardour/ardour/crossfade.h
index 5e25bbe00d..148b501e51 100644
--- a/libs/ardour/ardour/crossfade.h
+++ b/libs/ardour/ardour/crossfade.h
@@ -106,7 +106,7 @@ class Crossfade : public ARDOUR::AudioRegion
 	nframes_t overlap_length() const;
 
 	PBD::Signal1<void,boost::shared_ptr<Region> > Invalidated;
-	PBD::Signal1<void,Change>     StateChanged;
+	PBD::Signal1<void,PBD::Change>     StateChanged;
 
 	bool covers (nframes_t frame) const {
 		return _position <= frame && frame < _position + _length;
@@ -136,8 +136,8 @@ class Crossfade : public ARDOUR::AudioRegion
 	static nframes_t short_xfade_length() { return _short_xfade_length; }
 	static void set_short_xfade_length (nframes_t n);
 
-	static Change ActiveChanged;
-	static Change FollowOverlapChanged;
+	static PBD::Change ActiveChanged;
+	static PBD::Change FollowOverlapChanged;
 
   private:
 	friend struct CrossfadeComparePtr;
diff --git a/libs/ardour/ardour/diskstream.h b/libs/ardour/ardour/diskstream.h
index 85e3071021..0c1bbd54d8 100644
--- a/libs/ardour/ardour/diskstream.h
+++ b/libs/ardour/ardour/diskstream.h
@@ -206,7 +206,7 @@ class Diskstream : public SessionObject
 
 	/* XXX fix this redundancy ... */
 
-	virtual void playlist_changed (Change);
+	virtual void playlist_changed (PBD::Change);
 	virtual void playlist_deleted (boost::weak_ptr<Playlist>);
 	virtual void playlist_ranges_moved (std::list< Evoral::RangeMove<nframes_t> > const &);
 
diff --git a/libs/ardour/ardour/location.h b/libs/ardour/ardour/location.h
index 1f2b80c831..6cec906d28 100644
--- a/libs/ardour/ardour/location.h
+++ b/libs/ardour/ardour/location.h
@@ -179,7 +179,7 @@ class Locations : public PBD::StatefulDestructible
 	PBD::Signal0<void>           changed;
 	PBD::Signal1<void,Location*> added;
 	PBD::Signal1<void,Location*> removed;
-	PBD::Signal1<void,Change>    StateChanged;
+	PBD::Signal1<void,PBD::Change>    StateChanged;
 
 	template<class T> void apply (T& obj, void (T::*method)(LocationList&)) {
 		Glib::Mutex::Lock lm (lock);
diff --git a/libs/ardour/ardour/midi_playlist.h b/libs/ardour/ardour/midi_playlist.h
index 16e66188fe..32196206e2 100644
--- a/libs/ardour/ardour/midi_playlist.h
+++ b/libs/ardour/ardour/midi_playlist.h
@@ -74,7 +74,7 @@ protected:
 private:
 	void dump () const;
 
-	bool region_changed (Change, boost::shared_ptr<Region>);
+	bool region_changed (PBD::Change, boost::shared_ptr<Region>);
 
 	NoteMode _note_mode;
 
diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index 1c83c838a7..7309058b8e 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -121,7 +121,7 @@ class MidiRegion : public Region
 
   protected:
 
-	int set_live_state (const XMLNode&, int version, Change&, bool send);
+	int set_live_state (const XMLNode&, int version, PBD::Change&, bool send);
 };
 
 } /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/playlist.h b/libs/ardour/ardour/playlist.h
index fb734458d5..404fc61d2d 100644
--- a/libs/ardour/ardour/playlist.h
+++ b/libs/ardour/ardour/playlist.h
@@ -249,15 +249,15 @@ class Playlist : public SessionObject
 	void notify_length_changed ();
 	void notify_layering_changed ();
 	void notify_contents_changed ();
-	void notify_state_changed (Change);
+	void notify_state_changed (PBD::Change);
 	void notify_region_moved (boost::shared_ptr<Region>);
 
 	void mark_session_dirty();
 
-	void region_changed_proxy (Change, boost::weak_ptr<Region>);
-	virtual bool region_changed (Change, boost::shared_ptr<Region>);
+	void region_changed_proxy (PBD::Change, boost::weak_ptr<Region>);
+	virtual bool region_changed (PBD::Change, boost::shared_ptr<Region>);
 
-	void region_bounds_changed (Change, boost::shared_ptr<Region>);
+	void region_bounds_changed (PBD::Change, boost::shared_ptr<Region>);
 	void region_deleted (boost::shared_ptr<Region>);
 
 	void sort_regions ();
diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index 7060607a8d..414a1723f9 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -87,15 +87,15 @@ class Region
 
 	static const Flag DefaultFlags = Flag (Opaque|DefaultFadeIn|DefaultFadeOut|FadeIn|FadeOut);
 
-	static Change FadeChanged;
-	static Change SyncOffsetChanged;
-	static Change MuteChanged;
-	static Change OpacityChanged;
-	static Change LockChanged;
-	static Change LayerChanged;
-	static Change HiddenChanged;
-
-	PBD::Signal1<void,Change> StateChanged;
+	static PBD::Change FadeChanged;
+	static PBD::Change SyncOffsetChanged;
+	static PBD::Change MuteChanged;
+	static PBD::Change OpacityChanged;
+	static PBD::Change LockChanged;
+	static PBD::Change LayerChanged;
+	static PBD::Change HiddenChanged;
+
+	PBD::Signal1<void,PBD::Change> StateChanged;
 	static PBD::Signal1<void,boost::shared_ptr<ARDOUR::Region> > RegionPropertyChanged;
 	void unlock_property_changes () { _flags = Flag (_flags & ~DoNotSendPropertyChanges); }
 	void block_property_changes () { _flags = Flag (_flags | DoNotSendPropertyChanges); }
@@ -242,7 +242,7 @@ class Region
 	XMLNode&         get_state ();
 	virtual XMLNode& state (bool);
 	virtual int      set_state (const XMLNode&, int version);
-	virtual int      set_live_state (const XMLNode&, int version, Change&, bool send);
+	virtual int      set_live_state (const XMLNode&, int version, PBD::Change&, bool send);
 
 	virtual boost::shared_ptr<Region> get_parent() const;
 
@@ -296,7 +296,7 @@ class Region
 
 	XMLNode& get_short_state (); /* used only by Session */
 
-	void send_change (Change);
+	void send_change (PBD::Change);
 
 	void trim_to_internal (nframes_t position, nframes_t length, void *src);
 	virtual void set_position_internal (nframes_t pos, bool allow_bbt_recompute);
@@ -333,7 +333,7 @@ class Region
 	AnalysisFeatureList     _transients;
 	bool                    _valid_transients;
 	mutable uint32_t        _read_data_count;  ///< modified in read()
-	Change                  _pending_changed;
+	PBD::Change             _pending_changed;
 	uint64_t                _last_layer_op;  ///< timestamp
 	Glib::Mutex             _lock;
 	SourceList              _sources;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index f0b71d8019..06d5337b86 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -1210,7 +1210,7 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	void xrun_recovery ();
 
 	TempoMap    *_tempo_map;
-	void          tempo_map_changed (Change);
+	void          tempo_map_changed (PBD::Change);
 
 	/* edit/mix groups */
 
@@ -1257,7 +1257,7 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	RegionList regions;
 
 	void add_region (boost::shared_ptr<Region>);
-	void region_changed (Change, boost::weak_ptr<Region>);
+	void region_changed (PBD::Change, boost::weak_ptr<Region>);
 	void remove_region (boost::weak_ptr<Region>);
 
 	int load_regions (const XMLNode& node);
diff --git a/libs/ardour/ardour/tempo.h b/libs/ardour/ardour/tempo.h
index 9fe6f1fee5..d85247bec4 100644
--- a/libs/ardour/ardour/tempo.h
+++ b/libs/ardour/ardour/tempo.h
@@ -258,7 +258,7 @@ class TempoMap : public PBD::StatefulDestructible
 
 	nframes_t frame_rate () const { return _frame_rate; }
 
-	PBD::Signal1<void,ARDOUR::Change> StateChanged;
+	PBD::Signal1<void,PBD::Change> StateChanged;
 
   private:
 	static Tempo    _default_tempo;
diff --git a/libs/ardour/ardour/types.h b/libs/ardour/ardour/types.h
index 92c26a9448..e8a8120591 100644
--- a/libs/ardour/ardour/types.h
+++ b/libs/ardour/ardour/types.h
@@ -261,11 +261,6 @@ namespace ARDOUR {
 		SyncPoint
 	};
 
-	enum Change {
-		range_guarantee = ~0
-	};
-
-
 	enum Placement {
 		PreFader,
 		PostFader
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index e1aeffb4b3..7485ac6913 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -54,13 +54,13 @@ using namespace PBD;
 
 /* a Session will reset these to its chosen defaults by calling AudioRegion::set_default_fade() */
 
-Change AudioRegion::FadeInChanged         = ARDOUR::new_change();
-Change AudioRegion::FadeOutChanged        = ARDOUR::new_change();
-Change AudioRegion::FadeInActiveChanged   = ARDOUR::new_change();
-Change AudioRegion::FadeOutActiveChanged  = ARDOUR::new_change();
-Change AudioRegion::EnvelopeActiveChanged = ARDOUR::new_change();
-Change AudioRegion::ScaleAmplitudeChanged = ARDOUR::new_change();
-Change AudioRegion::EnvelopeChanged       = ARDOUR::new_change();
+Change AudioRegion::FadeInChanged         = PBD::new_change();
+Change AudioRegion::FadeOutChanged        = PBD::new_change();
+Change AudioRegion::FadeInActiveChanged   = PBD::new_change();
+Change AudioRegion::FadeOutActiveChanged  = PBD::new_change();
+Change AudioRegion::EnvelopeActiveChanged = PBD::new_change();
+Change AudioRegion::ScaleAmplitudeChanged = PBD::new_change();
+Change AudioRegion::EnvelopeChanged       = PBD::new_change();
 
 void
 AudioRegion::init ()
diff --git a/libs/ardour/globals.cc b/libs/ardour/globals.cc
index 125c0a8322..7536ee5932 100644
--- a/libs/ardour/globals.cc
+++ b/libs/ardour/globals.cc
@@ -99,11 +99,11 @@ MIDI::Port *ARDOUR::default_mtc_port = 0;
 MIDI::Port *ARDOUR::default_midi_port = 0;
 MIDI::Port *ARDOUR::default_midi_clock_port = 0;
 
-Change ARDOUR::StartChanged = ARDOUR::new_change ();
-Change ARDOUR::LengthChanged = ARDOUR::new_change ();
-Change ARDOUR::PositionChanged = ARDOUR::new_change ();
-Change ARDOUR::NameChanged = ARDOUR::new_change ();
-Change ARDOUR::BoundsChanged = Change (0); // see init(), below
+PBD::Change ARDOUR::StartChanged = PBD::new_change ();
+PBD::Change ARDOUR::LengthChanged = PBD::new_change ();
+PBD::Change ARDOUR::PositionChanged = PBD::new_change ();
+PBD::Change ARDOUR::NameChanged = PBD::new_change ();
+PBD::Change ARDOUR::BoundsChanged = Change (0); // see init(), below
 
 compute_peak_t          ARDOUR::compute_peak = 0;
 find_peaks_t            ARDOUR::find_peaks = 0;
@@ -388,27 +388,6 @@ ARDOUR::cleanup ()
 	return 0;
 }
 
-ARDOUR::Change
-ARDOUR::new_change ()
-{
-	Change c;
-	static uint32_t change_bit = 1;
-
-	/* catch out-of-range */
-	if (!change_bit)
-	{
-		fatal << _("programming error: ")
-			<< "change_bit out of range in ARDOUR::new_change()"
-			<< endmsg;
-		/*NOTREACHED*/
-	}
-
-	c = Change (change_bit);
-	change_bit <<= 1;	// if it shifts too far, change_bit == 0
-
-	return c;
-}
-
 string
 ARDOUR::get_ardour_revision ()
 {
diff --git a/libs/ardour/midi_playlist.cc b/libs/ardour/midi_playlist.cc
index 1721647c7c..e5c2e996f8 100644
--- a/libs/ardour/midi_playlist.cc
+++ b/libs/ardour/midi_playlist.cc
@@ -415,7 +415,7 @@ MidiPlaylist::contained_automation()
 
 
 bool
-MidiPlaylist::region_changed (Change what_changed, boost::shared_ptr<Region> region)
+MidiPlaylist::region_changed (PBD::Change what_changed, boost::shared_ptr<Region> region)
 {
 	if (in_flush || in_set_state) {
 		return false;
@@ -423,7 +423,7 @@ MidiPlaylist::region_changed (Change what_changed, boost::shared_ptr<Region> reg
 
 	// Feeling rather uninterested today, but thanks for the heads up anyway!
 
-	Change our_interests = Change (/*MidiRegion::FadeInChanged|
+	PBD::Change our_interests = PBD::Change (/*MidiRegion::FadeInChanged|
 	                               MidiRegion::FadeOutChanged|
 	                               MidiRegion::FadeInActiveChanged|
 	                               MidiRegion::FadeOutActiveChanged|
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index e9b896f26e..52137f9af2 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -46,13 +46,13 @@ using namespace std;
 using namespace ARDOUR;
 using namespace PBD;
 
-Change Region::FadeChanged       = ARDOUR::new_change ();
-Change Region::SyncOffsetChanged = ARDOUR::new_change ();
-Change Region::MuteChanged       = ARDOUR::new_change ();
-Change Region::OpacityChanged    = ARDOUR::new_change ();
-Change Region::LockChanged       = ARDOUR::new_change ();
-Change Region::LayerChanged      = ARDOUR::new_change ();
-Change Region::HiddenChanged     = ARDOUR::new_change ();
+Change Region::FadeChanged       = PBD::new_change ();
+Change Region::SyncOffsetChanged = PBD::new_change ();
+Change Region::MuteChanged       = PBD::new_change ();
+Change Region::OpacityChanged    = PBD::new_change ();
+Change Region::LockChanged       = PBD::new_change ();
+Change Region::LayerChanged      = PBD::new_change ();
+Change Region::HiddenChanged     = PBD::new_change ();
 
 PBD::Signal1<void,boost::shared_ptr<ARDOUR::Region> > Region::RegionPropertyChanged;
 
@@ -70,13 +70,13 @@ Region::Region (Session& s, nframes_t start, nframes_t length, const string& nam
 	: SessionObject(s, name)
 	, _type(type)
 	, _flags(Flag (flags|DoNotSendPropertyChanges))
-	, _start (X_("start"), start)
+	, _start (X_("start"), StartChanged, start)
 	, _length(length)
-	, _position (X_("position"), 0)
+	, _position (X_("position"), PositionChanged, 0)
 	, _last_position(0)
 	, _positional_lock_style(AudioTime)
 	, _sync_position(_start)
-	, _layer (X_("layer"), layer)
+	, _layer (X_("layer"), LayerChanged, layer)
 	, _first_edit(EditChangesNothing)
 	, _frozen(0)
 	, _ancestral_start (0)
@@ -98,13 +98,13 @@ Region::Region (boost::shared_ptr<Source> src, nframes_t start, nframes_t length
 	: SessionObject(src->session(), name)
 	, _type(type)
 	, _flags(Flag (flags|DoNotSendPropertyChanges))
-	, _start (X_("start"), start)
+	, _start (X_("start"), StartChanged, start)
 	, _length(length)
-	, _position (X_("position"), 0)
+	, _position (X_("position"), PositionChanged, 0)
 	, _last_position(0)
 	, _positional_lock_style(AudioTime)
 	, _sync_position(_start)
-	, _layer (X_("layer"), layer)
+	, _layer (X_("layer"), LayerChanged, layer)
 	, _first_edit(EditChangesNothing)
 	, _frozen(0)
 	, _ancestral_start (0)
@@ -133,13 +133,13 @@ Region::Region (const SourceList& srcs, nframes_t start, nframes_t length, const
 	: SessionObject(srcs.front()->session(), name)
 	, _type(type)
 	, _flags(Flag (flags|DoNotSendPropertyChanges))
-	, _start (X_("start"), start)
+	, _start (X_("start"), StartChanged, start)
 	, _length(length)
-	, _position (X_("position"), 0)
+	, _position (X_("position"), PositionChanged, 0)
 	, _last_position(0)
 	, _positional_lock_style(AudioTime)
 	, _sync_position(_start)
-	, _layer (X_("layer"), layer)
+	, _layer (X_("layer"), LayerChanged, layer)
 	, _first_edit(EditChangesNothing)
 	, _frozen(0)
 	, _ancestral_start (0)
@@ -161,9 +161,9 @@ Region::Region (const SourceList& srcs, nframes_t start, nframes_t length, const
 Region::Region (boost::shared_ptr<const Region> other, nframes_t offset, nframes_t length, const string& name, layer_t layer, Flag flags)
 	: SessionObject(other->session(), name)
 	, _type (other->data_type())
-	, _start (X_("start"), 0)
-	, _position (X_("position"), 0)
-	, _layer (X_("layer"), 0)
+	, _start (X_("start"), StartChanged, 0)
+	, _position (X_("position"), PositionChanged, 0)
+	, _layer (X_("layer"), LayerChanged, 0)
 	, _pending_explicit_relayer (false)
 
 {
@@ -206,9 +206,9 @@ Region::Region (boost::shared_ptr<const Region> other, nframes_t offset, nframes
 Region::Region (boost::shared_ptr<const Region> other, nframes_t length, const string& name, layer_t layer, Flag flags)
 	: SessionObject(other->session(), name)
 	, _type (other->data_type())
-	, _start (X_("start"), 0)
-	, _position (X_("position"), 0)
-	, _layer (X_("layer"), 0)
+	, _start (X_("start"), StartChanged, 0)
+	, _position (X_("position"), PositionChanged, 0)
+	, _layer (X_("layer"), LayerChanged, 0)
 	, _pending_explicit_relayer (false)
 {
 	register_states ();
@@ -306,13 +306,13 @@ Region::Region (const SourceList& srcs, const XMLNode& node)
 	: SessionObject(srcs.front()->session(), X_("error: XML did not reset this"))
 	, _type(DataType::NIL) // to be loaded from XML
 	, _flags(DoNotSendPropertyChanges)
-	, _start (X_("start"), 0)
+	, _start (X_("start"), StartChanged, 0)
 	, _length(0)
-	, _position (X_("position"), 0)
+	, _position (X_("position"), PositionChanged, 0)
 	, _last_position(0)
 	, _positional_lock_style(AudioTime)
 	, _sync_position(_start)
-	, _layer (X_("layer"), 0)
+	, _layer (X_("layer"), LayerChanged, 0)
 	, _first_edit(EditChangesNothing)
 	, _frozen(0)
 	, _stretch(1.0)
@@ -338,13 +338,13 @@ Region::Region (boost::shared_ptr<Source> src, const XMLNode& node)
 	: SessionObject(src->session(), X_("error: XML did not reset this"))
 	, _type(DataType::NIL)
 	, _flags(DoNotSendPropertyChanges)
-	, _start (X_("start"), 0)
+	, _start (X_("start"), StartChanged, 0)
 	, _length(0)
-	, _position (X_("position"), 0)
+	, _position (X_("position"), PositionChanged, 0)
 	, _last_position(0)
 	, _positional_lock_style(AudioTime)
 	, _sync_position(_start)
-	, _layer (X_("layer"), 0)
+	, _layer (X_("layer"), LayerChanged, 0)
 	, _first_edit(EditChangesNothing)
 	, _frozen(0)
 	, _stretch(1.0)
@@ -1092,16 +1092,14 @@ Region::state (bool /*full_state*/)
 	char buf[64];
 	const char* fe = NULL;
 
+	add_states (*node);
+
 	_id.print (buf, sizeof (buf));
 	node->add_property ("id", buf);
 	node->add_property ("name", _name);
 	node->add_property ("type", _type.to_string());
-	snprintf (buf, sizeof (buf), "%u", _start.get ());
-	node->add_property ("start", buf);
 	snprintf (buf, sizeof (buf), "%u", _length);
 	node->add_property ("length", buf);
-	snprintf (buf, sizeof (buf), "%u", _position.get ());
-	node->add_property ("position", buf);
 	snprintf (buf, sizeof (buf), "%" PRIi64, _ancestral_start);
 	node->add_property ("ancestral-start", buf);
 	snprintf (buf, sizeof (buf), "%" PRIi64, _ancestral_length);
@@ -1130,8 +1128,6 @@ Region::state (bool /*full_state*/)
 
 	/* note: flags are stored by derived classes */
 
-	snprintf (buf, sizeof (buf), "%d", (int) _layer.get());
-	node->add_property ("layer", buf);
 	snprintf (buf, sizeof (buf), "%" PRIu32, _sync_position);
 	node->add_property ("sync-position", buf);
 
@@ -1172,15 +1168,6 @@ Region::set_live_state (const XMLNode& node, int /*version*/, Change& what_chang
 		_type = DataType(prop->value());
 	}
 
-	if ((prop = node.property ("start")) != 0) {
-		sscanf (prop->value().c_str(), "%" PRIu32, &val);
-		if (val != _start) {
-			what_changed = Change (what_changed|StartChanged);
-			cerr << _name << " start changed\n";
-			_start = val;
-		}
-	}
-
 	if ((prop = node.property ("length")) != 0) {
 		sscanf (prop->value().c_str(), "%" PRIu32, &val);
 		if (val != _length) {
@@ -1191,26 +1178,6 @@ Region::set_live_state (const XMLNode& node, int /*version*/, Change& what_chang
 		}
 	}
 
-	if ((prop = node.property ("position")) != 0) {
-		sscanf (prop->value().c_str(), "%" PRIu32, &val);
-		if (val != _position) {
-			what_changed = Change (what_changed|PositionChanged);
-			cerr << _name << " position changed\n";
-			_last_position = _position;
-			_position = val;
-		}
-	}
-
-	if ((prop = node.property ("layer")) != 0) {
-		layer_t x;
-		x = (layer_t) atoi (prop->value().c_str());
-		if (x != _layer) {
-			what_changed = Change (what_changed|LayerChanged);
-			cerr << _name << " layer changed\n";
-			_layer = x;
-		}
-	}
-
 	if ((prop = node.property ("sync-position")) != 0) {
 		sscanf (prop->value().c_str(), "%" PRIu32, &val);
 		if (val != _sync_position) {
@@ -1309,7 +1276,6 @@ int
 Region::set_state (const XMLNode& node, int version)
 {
 	const XMLProperty *prop;
-	Change what_changed = Change (0);
 
 	/* ID is not allowed to change, ever */
 
@@ -1319,6 +1285,8 @@ Region::set_state (const XMLNode& node, int version)
 
 	_first_edit = EditChangesNothing;
 
+	Change what_changed = set_state_using_states (node);
+
 	set_live_state (node, version, what_changed, true);
 
 	return 0;
diff --git a/libs/pbd/pbd/stateful.h b/libs/pbd/pbd/stateful.h
index 60c1c6b23c..80d7aa796a 100644
--- a/libs/pbd/pbd/stateful.h
+++ b/libs/pbd/pbd/stateful.h
@@ -33,13 +33,20 @@ namespace sys {
 	class path;
 }
 
+enum Change {
+	range_guarantee = ~0
+};
+
+Change new_change ();
+
 /** Base (non template) part of State */	
 class StateBase
 {
 public:
-	StateBase (std::string const & p)
+	StateBase (std::string const & p, Change c)
 		: _have_old (false)
 		, _xml_property_name (p)
+		, _change (c)
 	{
 
 	}
@@ -47,6 +54,7 @@ public:
 	StateBase (StateBase const & s)
 		: _have_old (s._have_old)
 		, _xml_property_name (s._xml_property_name)
+		, _change (s._change)
 	{
 
 	}
@@ -57,10 +65,13 @@ public:
 	}
 
 	virtual void diff (XMLNode *, XMLNode *) const = 0;
+	virtual Change set_state (XMLNode const &) = 0;
+	virtual void add_state (XMLNode &) const = 0;
 
 protected:
 	bool _have_old;
 	std::string _xml_property_name;
+	Change _change;
 };
 
 /** Class to represent a single piece of state in a Stateful object */
@@ -68,8 +79,8 @@ template <class T>
 class State : public StateBase
 {
 public:
-	State (std::string const & p, T const & v)
-		: StateBase (p)
+	State (std::string const & p, Change c, T const & v)
+		: StateBase (p, c)
 		, _current (v)
 	{
 
@@ -86,6 +97,7 @@ public:
 		/* XXX: isn't there a nicer place to do this? */
 		_have_old = s._have_old;
 		_xml_property_name = s._xml_property_name;
+		_change = s._change;
 		
 		_current = s._current;
 		_old = s._old;
@@ -112,13 +124,36 @@ public:
 
 	void diff (XMLNode* old, XMLNode* current) const {
 		if (_have_old) {
-			std::stringstream o;
-			o << _old;
-			old->add_property (_xml_property_name.c_str(), o.str().c_str());
-			std::stringstream c;
-			c << _current;
-			current->add_property (_xml_property_name.c_str(), c.str().c_str());
+			old->add_property (_xml_property_name.c_str(), to_string (_old));
+			current->add_property (_xml_property_name.c_str(), to_string (_current));
+		}
+	}
+
+	/** Try to set state from the property of an XML node.
+	 *  @param node XML node.
+	 *  @return Change effected, or 0.
+	 */
+	Change set_state (XMLNode const & node) {
+		XMLProperty const * p = node.property (_xml_property_name.c_str());
+
+		if (p) {
+			std::stringstream s (p->value ());
+			T v;
+			s >> v;
+
+			if (v == _current) {
+				return Change (0);
+			}
+
+			set (v);
+			return _change;
 		}
+
+		return Change (0);
+	}
+
+	void add_state (XMLNode & node) const {
+		node.add_property (_xml_property_name.c_str(), to_string (_current));
 	}
 
 private:
@@ -127,6 +162,12 @@ private:
 		_have_old = true;
 		_current = v;
 	}
+
+	std::string to_string (T const & v) const {
+		std::stringstream s;
+		s << v;
+		return s.str ();
+	}
 		
 	T _current;
 	T _old;
@@ -163,6 +204,8 @@ class Stateful {
 
 	void add_instant_xml (XMLNode&, const sys::path& directory_path);
 	XMLNode *instant_xml (const std::string& str, const sys::path& directory_path);
+	Change set_state_using_states (XMLNode const &);
+	void add_states (XMLNode &);
 
 	XMLNode *_extra_xml;
 	XMLNode *_instant_xml;
diff --git a/libs/pbd/stateful.cc b/libs/pbd/stateful.cc
index 52b80c95ae..a50c54d7f5 100644
--- a/libs/pbd/stateful.cc
+++ b/libs/pbd/stateful.cc
@@ -35,6 +35,27 @@ namespace PBD {
 int Stateful::current_state_version = 0;
 int Stateful::loading_state_version = 0;
 
+PBD::Change
+new_change ()
+{
+	Change c;
+	static uint32_t change_bit = 1;
+
+	/* catch out-of-range */
+	if (!change_bit)
+	{
+		fatal << _("programming error: ")
+			<< "change_bit out of range in ARDOUR::new_change()"
+			<< endmsg;
+		/*NOTREACHED*/
+	}
+
+	c = Change (change_bit);
+	change_bit <<= 1;	// if it shifts too far, change_bit == 0
+
+	return c;
+}
+
 Stateful::Stateful ()
 {
 	_extra_xml = 0;
@@ -175,5 +196,32 @@ Stateful::diff ()
 
 	return make_pair (old, current);
 }
+	
+/** Set state of _states from an XML node.
+ *  @param node Node.
+ *  @return Changes made.
+ */
+Change
+Stateful::set_state_using_states (XMLNode const & node)
+{
+	Change c = Change (0);
+	
+	for (list<StateBase*>::iterator i = _states.begin(); i != _states.end(); ++i) {
+		c = Change (c | (*i)->set_state (node));
+	}
+
+	return c;
+}
+
+/** Add state of _states to an XML node.
+ *  @param node Node.
+ */
+void
+Stateful::add_states (XMLNode & node)
+{
+	for (list<StateBase*>::iterator i = _states.begin(); i != _states.end(); ++i) {
+		(*i)->add_state (node);
+	}
+}
 
 } // namespace PBD