From 71ac083429575ea21ffff97c07a2ec18c4852cc7 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Sun, 30 Nov 2008 23:16:57 +0000
Subject: [PATCH] fix up monumental botch job regarding undo
 history/object/command management

git-svn-id: svn://localhost/ardour2/branches/2.0-ongoing@4274 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/pbd/pbd/memento_command.h |  2 +-
 libs/pbd/pbd/shiva.h           | 21 +++++++++++----------
 libs/pbd/pbd/undo.h            |  9 ++++++++-
 libs/pbd/undo.cc               | 24 +++++++++++++++++++++---
 4 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/libs/pbd/pbd/memento_command.h b/libs/pbd/pbd/memento_command.h
index d913b2c0fe..d1d1bdefaa 100644
--- a/libs/pbd/pbd/memento_command.h
+++ b/libs/pbd/pbd/memento_command.h
@@ -47,7 +47,7 @@ class MementoCommand : public Command
                        ) 
             : obj(object), before(before), after(after) {
 		/* catch destruction of the object */
-		new PBD::Shiva<obj_T,MementoCommand<obj_T> > (object, *this);
+		new PBD::PairedShiva<obj_T,MementoCommand<obj_T> > (object, *this);
 	}
 
 	~MementoCommand () {
diff --git a/libs/pbd/pbd/shiva.h b/libs/pbd/pbd/shiva.h
index 2e53ff65f5..90adad6250 100644
--- a/libs/pbd/pbd/shiva.h
+++ b/libs/pbd/pbd/shiva.h
@@ -27,7 +27,8 @@ namespace PBD {
 /* named after the Hindu god Shiva, The Destroyer */
 
 template<typename ObjectWithGoingAway, typename ObjectToBeDestroyed>
-class Shiva {
+class Shiva : public sigc::trackable 
+{
   public:
 	Shiva (ObjectWithGoingAway& emitter, ObjectToBeDestroyed& receiver) {
 
@@ -58,15 +59,15 @@ class Shiva {
 };
 
 template<typename ObjectWithGoingAway, typename ObjectToBeDestroyed>
-class ProxyShiva {
+class ProxyShiva : public sigc::trackable 
+{
   public:
 	ProxyShiva (ObjectWithGoingAway& emitter, ObjectToBeDestroyed& receiver, void (*callback)(ObjectToBeDestroyed*, ObjectWithGoingAway*)) {
-
+		
 		/* if the emitter goes away, destroy the receiver */
 
 		_callback = callback;
-		_callback_argument1 = &receiver;
-		_callback_argument2 = &emitter;
+		_callback_argument = &emitter;
 
 		_connection = emitter.GoingAway.connect 
 			(sigc::bind (sigc::mem_fun 
@@ -74,19 +75,18 @@ class ProxyShiva {
 				     &receiver));
 	}
 
-	~ProxyShiva() { 
+	~ProxyShiva () {
 		forget ();
 	}
 
   private:
 	sigc::connection _connection;
 	void (*_callback) (ObjectToBeDestroyed*, ObjectWithGoingAway*);
-	ObjectToBeDestroyed* _callback_argument1;
-	ObjectWithGoingAway* _callback_argument2;
+	ObjectWithGoingAway* _callback_argument;
 
 	void destroy (ObjectToBeDestroyed* obj) {
 		/* callback must destroy obj if appropriate, not done here */
-		_callback (obj, _callback_argument2);
+		_callback (obj, _callback_argument);
 		forget ();
 	}
 
@@ -96,7 +96,8 @@ class ProxyShiva {
 };
 
 template<typename ObjectWithGoingAway, typename ObjectToBeDestroyed>
-class PairedShiva {
+class PairedShiva : public sigc::trackable 
+{
   public:
 	PairedShiva (ObjectWithGoingAway& emitter, ObjectToBeDestroyed& receiver) {
 
diff --git a/libs/pbd/pbd/undo.h b/libs/pbd/pbd/undo.h
index c5f60c51af..6ee69e75e4 100644
--- a/libs/pbd/pbd/undo.h
+++ b/libs/pbd/pbd/undo.h
@@ -27,6 +27,7 @@
 #include <sigc++/bind.h>
 #include <sys/time.h>
 #include <pbd/command.h>
+#include <pbd/shiva.h>
 
 typedef sigc::slot<void> UndoAction;
 
@@ -36,7 +37,6 @@ class UndoTransaction : public Command
 	UndoTransaction ();
 	UndoTransaction (const UndoTransaction&);
 	UndoTransaction& operator= (const UndoTransaction&);
-	~UndoTransaction ();
 
 	void clear ();
 	bool empty() const;
@@ -66,11 +66,18 @@ class UndoTransaction : public Command
 
   private:
 	std::list<Command*>    actions;
+	std::list<PBD::ProxyShiva<Command,UndoTransaction>*> shivas;
 	struct timeval        _timestamp;
 	std::string           _name;
 	bool                  _clearing;
 
 	friend void command_death (UndoTransaction*, Command *);
+	
+	friend class UndoHistory;
+
+	~UndoTransaction ();
+	void about_to_explicitly_delete ();
+	
 };
 
 class UndoHistory : public sigc::trackable
diff --git a/libs/pbd/undo.cc b/libs/pbd/undo.cc
index 43baad35d2..2e2686d558 100644
--- a/libs/pbd/undo.cc
+++ b/libs/pbd/undo.cc
@@ -24,7 +24,6 @@
 
 #include <pbd/undo.h>
 #include <pbd/xml++.h>
-#include <pbd/shiva.h>
 
 #include <sigc++/bind.h>
 
@@ -78,8 +77,10 @@ UndoTransaction::operator= (const UndoTransaction& rhs)
 void
 UndoTransaction::add_command (Command *const action)
 {
-	/* catch death */
-	new PBD::ProxyShiva<Command,UndoTransaction> (*action, *this, &command_death);
+	/* catch death of command (e.g. caused by death of object to
+	   which it refers.
+	 */
+	shivas.push_back (new PBD::ProxyShiva<Command,UndoTransaction> (*action, *this, &command_death));
 	actions.push_back (action);
 }
 
@@ -89,6 +90,21 @@ UndoTransaction::remove_command (Command* const action)
 	actions.remove (action);
 }
 
+void
+UndoTransaction::about_to_explicitly_delete ()
+{
+	/* someone is going to call our destructor and its not Shiva,
+	   the god of destruction and chaos. This happens when an UndoHistory
+	   is pruning itself. we must remove Shivas to avoid the god
+	   striking us down a second time, unnecessarily and illegally.
+	*/
+
+	for (list<PBD::ProxyShiva<Command,UndoTransaction>*>::iterator i = shivas.begin(); i != shivas.end(); ++i) {
+		delete *i;
+	}
+	shivas.clear ();
+}
+
 bool
 UndoTransaction::empty () const
 {
@@ -172,6 +188,7 @@ UndoHistory::set_depth (uint32_t d)
 		while (cnt--) {
 			ut = UndoList.front();
 			UndoList.pop_front ();
+			ut->about_to_explicitly_delete ();
 			delete ut;
 		}
 	}
@@ -197,6 +214,7 @@ UndoHistory::add (UndoTransaction* const ut)
 			UndoTransaction* ut;
 			ut = UndoList.front ();
 			UndoList.pop_front ();
+			ut->about_to_explicitly_delete ();
 			delete ut;
 		}
 	}