Fix crossfade undo using the stateful diff system. Fixes #3257.

git-svn-id: svn://localhost/ardour2/branches/3.0@7694 d708f5d6-7413-0410-9779-e7cbd77b26cf

5 files changed, 30 insertions, 11 deletions

diff --git a/libs/pbd/pbd/command.h b/libs/pbd/pbd/command.h
index c6c3c8d3fd..db4d2bbd81 100644
--- a/libs/pbd/pbd/command.h
+++ b/libs/pbd/pbd/command.h
@@ -43,6 +43,10 @@ public:
 	virtual XMLNode &get_state();
 	virtual int set_state(const XMLNode&, int /*version*/) { /* noop */ return 0; }
 
+	virtual bool empty () const {
+		return false;
+	}
+
 protected:
 	Command() {}
 	Command(const std::string& name) : _name(name) {}
diff --git a/libs/pbd/pbd/property_basics.h b/libs/pbd/pbd/property_basics.h
index cfae36df20..145e84abfc 100644
--- a/libs/pbd/pbd/property_basics.h
+++ b/libs/pbd/pbd/property_basics.h
@@ -103,7 +103,7 @@ public:
 	virtual void get_changes_as_properties (PropertyList& changes, Command *) const = 0;
 
 	/** Collect StatefulDiffCommands for changes to anything that we own */
-	virtual void rdiff (std::vector<StatefulDiffCommand*> &) const {}
+	virtual void rdiff (std::vector<Command*> &) const {}
 
 	/** Look in an XML node written by get_changes_as_xml and, if XML from this property
 	 *  is found, create a property with the changes from the XML.
diff --git a/libs/pbd/pbd/sequence_property.h b/libs/pbd/pbd/sequence_property.h
index 5b37d7a0fc..4b494d4a8d 100644
--- a/libs/pbd/pbd/sequence_property.h
+++ b/libs/pbd/pbd/sequence_property.h
@@ -31,6 +31,7 @@
 #include "pbd/id.h"
 #include "pbd/property_basics.h"
 #include "pbd/property_list.h"
+#include "pbd/stateful_diff_command.h"
 
 namespace PBD {
 
@@ -80,8 +81,6 @@ class SequenceProperty : public PropertyBase
 	SequenceProperty (PropertyID id, const boost::function<void(const ChangeRecord&)>& update)
                 : PropertyBase (id), _update_callback (update) {}
 
-	virtual typename Container::value_type lookup_id (const PBD::ID&) const = 0;
-
         void invert () {
 		_changes.removed.swap (_changes.added);
         }
@@ -97,18 +96,25 @@ class SequenceProperty : public PropertyBase
 			for (typename ChangeContainer::iterator i = _changes.added.begin(); i != _changes.added.end(); ++i) {
                                 XMLNode* add_node = new XMLNode ("Add");
                                 child->add_child_nocopy (*add_node);
-                                add_node->add_property ("id", (*i)->id().to_s());
+				get_content_as_xml (*i, *add_node);
 			}
 		}
 		if (!_changes.removed.empty()) {
 			for (typename ChangeContainer::iterator i = _changes.removed.begin(); i != _changes.removed.end(); ++i) {
                                 XMLNode* remove_node = new XMLNode ("Remove");
                                 child->add_child_nocopy (*remove_node);
-                                remove_node->add_property ("id", (*i)->id().to_s());
+				get_content_as_xml (*i, *remove_node);
 			}
 		}
 	}
 
+	/** Get a representation of one of our items as XML.  The representation must be sufficient to
+	 *  restore the item's state later; an ID is ok if someone else is storing the item state,
+	 *  otherwise it needs to be the full state.  The supplied node is an <Add> or <Remove>
+	 *  which this method can either add properties or children to.
+	 */
+	virtual void get_content_as_xml (typename ChangeContainer::value_type, XMLNode &) const = 0;
+
 	bool set_value (XMLNode const &) {
 		/* XXX: not used, but probably should be */
 		assert (false);
@@ -191,11 +197,10 @@ class SequenceProperty : public PropertyBase
 
 		XMLNodeList const & grandchildren = (*i)->children ();
 		for (XMLNodeList::const_iterator j = grandchildren.begin(); j != grandchildren.end(); ++j) {
-			XMLProperty const * prop = (*j)->property ("id");
-			assert (prop);
-			PBD::ID id (prop->value ());
-			typename Container::value_type v = lookup_id (id);
+
+			typename Container::value_type v = get_content_from_xml (**j);
 			assert (v);
+			
 			if ((*j)->name() == "Add") {
 				p->_changes.added.insert (v);
 			} else if ((*j)->name() == "Remove") {
@@ -206,13 +211,16 @@ class SequenceProperty : public PropertyBase
 		return p;
         }
 
+	/** Given an <Add> or <Remove> node as passed into get_content_to_xml, obtain an item */
+	virtual typename Container::value_type get_content_from_xml (XMLNode const & node) const = 0;
+
 	void clear_owned_changes () {
 		for (typename Container::iterator i = begin(); i != end(); ++i) {
 			(*i)->clear_changes ();
 		}
 	}
 
-	void rdiff (std::vector<StatefulDiffCommand*>& cmds) const {
+	void rdiff (std::vector<Command*>& cmds) const {
 		for (typename Container::const_iterator i = begin(); i != end(); ++i) {
 			if ((*i)->changed ()) {
 				StatefulDiffCommand* sdc = new StatefulDiffCommand (*i);
@@ -255,6 +263,11 @@ class SequenceProperty : public PropertyBase
 		return _val.erase (f, l);
 	}
 
+	void remove (const typename Container::value_type& v) {
+		_changes.remove (v);
+		_val.remove (v);
+	}
+
 	void push_back (const typename Container::value_type& v) {
 		_changes.add (v);
 		_val.push_back (v);
diff --git a/libs/pbd/pbd/stateful.h b/libs/pbd/pbd/stateful.h
index 5c1f079bc6..735ffbdc4a 100644
--- a/libs/pbd/pbd/stateful.h
+++ b/libs/pbd/pbd/stateful.h
@@ -70,7 +70,7 @@ class Stateful {
 	void clear_changes ();
 	virtual void clear_owned_changes ();
         PropertyList* get_changes_as_properties (Command *) const;
-	virtual void rdiff (std::vector<StatefulDiffCommand*> &) const;
+	virtual void rdiff (std::vector<Command*> &) const;
         bool changed() const;
 
         /* create a property list from an XMLNode
diff --git a/libs/pbd/pbd/stateful_diff_command.h b/libs/pbd/pbd/stateful_diff_command.h
index 2d5c234d76..2a213d7a17 100644
--- a/libs/pbd/pbd/stateful_diff_command.h
+++ b/libs/pbd/pbd/stateful_diff_command.h
@@ -45,6 +45,8 @@ public:
         
 	XMLNode& get_state ();
 
+	bool empty () const;
+
 private:
 	boost::weak_ptr<Stateful> _object; ///< the object in question
         PBD::PropertyList* _changes; ///< property changes to execute this command