(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

libs/pbd/pbd/properties.h

@@ -122,8 +122,10 @@ protected:
 	{}
 
 	void set (T const& v) {
-		_old      = _current;
-		_have_old = true;
+                if (!_have_old) {
+                        _old      = _current;
+                        _have_old = true;
+                }
 		_current  = v;
 	}
 

libs/pbd/pbd/stateful.h

@@ -82,6 +82,12 @@ class Stateful {
 	static int current_state_version;
 	static int loading_state_version;
 
+	virtual void suspend_property_changes ();
+	virtual void resume_property_changes ();
+
+	void unlock_property_changes () { _no_property_changes = false; }
+	void block_property_changes () { _no_property_changes = true; }
+	
   protected:
 
 	void add_instant_xml (XMLNode&, const sys::path& directory_path);
@@ -100,10 +106,21 @@ class Stateful {
 
 	XMLNode *_extra_xml;
 	XMLNode *_instant_xml;
-	PBD::ID _id;
+	PBD::ID  _id;
+        int32_t  _frozen;
+        bool     _no_property_changes;
+	PBD::PropertyChange     _pending_changed;
+        Glib::Mutex _lock;
 
 	std::string _xml_node_name; ///< name of node to use for this object in XML
 	OwnedPropertyList* _properties;
+
+        virtual void send_change (const PropertyChange&);
+        /** derived classes can implement this in order to process a property change
+            within thaw() just before send_change() is called.
+        */
+        virtual void mid_thaw (const PropertyChange&) { }
+        bool property_changes_suspended() const { return g_atomic_int_get (&_frozen) > 0; }
 };
 
 } // namespace PBD

libs/pbd/stateful.cc

@@ -39,7 +39,9 @@ int Stateful::current_state_version = 0;
 int Stateful::loading_state_version = 0;
 
 Stateful::Stateful ()
-        : _properties (new OwnedPropertyList)
+        : _frozen (0)
+        , _no_property_changes (false)
+        , _properties (new OwnedPropertyList)
 {
 	_extra_xml = 0;
 	_instant_xml = 0;
@@ -238,4 +240,52 @@ Stateful::add_property (PropertyBase& s)
         _properties->add (s);
 }
 
+void
+Stateful::send_change (const PropertyChange& what_changed)
+{
+	if (what_changed.empty()) {
+		return;
+	}
+
+	{
+		Glib::Mutex::Lock lm (_lock);
+		if (_frozen) {
+			_pending_changed.add (what_changed);
+			return;
+		}
+	}
+
+	PropertyChanged (what_changed);
+}
+
+void
+Stateful::suspend_property_changes ()
+{
+        _frozen++;
+}
+
+void
+Stateful::resume_property_changes ()
+{
+	PropertyChange what_changed;
+
+	{
+		Glib::Mutex::Lock lm (_lock);
+
+		if (_frozen && --_frozen > 0) {
+			return;
+		}
+
+		if (!_pending_changed.empty()) {
+			what_changed = _pending_changed;
+			_pending_changed.clear ();
+		}
+	}
+
+        mid_thaw (what_changed);
+
+        send_change (what_changed);
+}
+
+
 } // namespace PBD