Modify Stateful to allow undo to be done using differences in state.

[ardour.git] / libs / pbd / stateful.cc

diff --git a/libs/pbd/stateful.cc b/libs/pbd/stateful.cc
index 596402576e6f133bf02513f2b35f347ba2afc53a..9f510b85d4972eb6a6d4e9755b44b358cc977928 100644 (file)
--- a/libs/pbd/stateful.cc
+++ b/libs/pbd/stateful.cc
@@ -47,6 +47,10 @@ Stateful::~Stateful ()
        // means it needs to live on indefinately.
 
        delete _instant_xml;
+
+       for (list<StateBase*>::iterator i = _states.begin(); i != _states.end(); ++i) {
+               delete *i;
+       }
 }
 
 void
@@ -149,4 +153,31 @@ Stateful::instant_xml (const string& str, const sys::path& directory_path)
        return 0;
 }
 
+/** Forget about any old state for this object */      
+void
+Stateful::clear_history ()
+{
+       for (list<StateBase*>::iterator i = _states.begin(); i != _states.end(); ++i) {
+               (*i)->clear_history ();
+       }
+}
+
+/** @return A pair of XMLNodes representing state that has changed since the last time clear_history
+ *  was called on this object; the first is the state before, the second the state after.
+ *
+ *  It is the caller's responsibility to delete the returned XMLNodes.
+ */
+pair<XMLNode *, XMLNode *>
+Stateful::diff ()
+{
+       XMLNode* old = new XMLNode (_xml_node_name);
+       XMLNode* current = new XMLNode (_xml_node_name);
+
+       for (list<StateBase*>::iterator i = _states.begin(); i != _states.end(); ++i) {
+               (*i)->diff (old, current);
+       }
+
+       return make_pair (old, current);
+}
+
 } // namespace PBD