From 074d58fc6f97c225e804d32b5d2b8f09e4d512da Mon Sep 17 00:00:00 2001
From: Carl Hetherington <carl@carlh.net>
Date: Wed, 19 Jan 2011 17:38:46 +0000
Subject: [PATCH] Fix undo nesting.

git-svn-id: svn://localhost/ardour2/branches/3.0@8538 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/ardour/ardour/session.h | 11 +++++---
 libs/ardour/session.cc       |  2 ++
 libs/ardour/session_state.cc | 49 ++++++++++++++++++++++++------------
 libs/pbd/pbd/undo.h          |  4 +--
 4 files changed, 43 insertions(+), 23 deletions(-)

diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index e5032ad8c2..2dc2650be9 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -669,8 +669,8 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	void commit_reversible_command (Command* cmd = 0);
 
 	void add_command (Command *const cmd) {
-		assert(!_current_trans.empty ());
-		_current_trans.top()->add_command (cmd);
+		assert (_current_trans);
+		_current_trans->add_command (cmd);
 	}
 
 	void add_commands (std::vector<Command*> const & cmds);
@@ -1336,8 +1336,11 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 
 	void reverse_track_buffers ();
 
-	UndoHistory                  _history;
-	std::stack<UndoTransaction*> _current_trans;
+	UndoHistory      _history;
+	/** current undo transaction, or 0 */
+	UndoTransaction* _current_trans;
+	/** number of times that begin_reversible_command has been called without commit_reversible_command */
+	int              _current_trans_depth;
 
 	void jack_timebase_callback (jack_transport_state_t, pframes_t, jack_position_t*, int);
 	int  jack_sync_callback (jack_transport_state_t, jack_position_t*);
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 72163155a5..4d31c20456 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -151,6 +151,8 @@ Session::Session (AudioEngine &eng,
 	, _total_free_4k_blocks (0)
 	, _bundles (new BundleList)
 	, _bundle_xml_node (0)
+	, _current_trans (0)
+	, _current_trans_depth (0)
 	, _click_io ((IO*) 0)
 	, click_data (0)
 	, click_emphasis_data (0)
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 6fdaf749ab..e7ccb02c7b 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -2362,38 +2362,55 @@ Session::add_commands (vector<Command*> const & cmds)
 }
 
 void
-Session::begin_reversible_command(const string& name)
+Session::begin_reversible_command (const string& name)
 {
-	UndoTransaction* trans = new UndoTransaction();
-	trans->set_name(name);
-
-	if (!_current_trans.empty()) {
-		_current_trans.top()->add_command (trans);
+	/* If nested begin/commit pairs are used, we create just one UndoTransaction
+	   to hold all the commands that are committed.  This keeps the order of
+	   commands correct in the history.
+	*/
+	
+	if (_current_trans == 0) {
+		/* start a new transaction */
+		assert (_current_trans_depth == 0);
+		_current_trans = new UndoTransaction();
+		_current_trans->set_name (name);
 	} else {
-		_current_trans.push(trans);
+		/* use the existing transaction */
+		++_current_trans_depth;
 	}
 }
 
 void
-Session::commit_reversible_command(Command *cmd)
+Session::commit_reversible_command (Command *cmd)
 {
-	assert(!_current_trans.empty());
+	assert (_current_trans);
+	assert (_current_trans_depth > 0);
+	
 	struct timeval now;
 
 	if (cmd) {
-		_current_trans.top()->add_command(cmd);
+		_current_trans->add_command (cmd);
 	}
 
-	if (_current_trans.top()->empty()) {
-		_current_trans.pop();
+	--_current_trans_depth;
+
+	if (_current_trans_depth > 0) {
+		/* the transaction we're committing is not the top-level one */
 		return;
 	}
 
-	gettimeofday(&now, 0);
-	_current_trans.top()->set_timestamp(now);
+	if (_current_trans->empty()) {
+		/* no commands were added to the transaction, so just get rid of it */
+		delete _current_trans;
+		_current_trans = 0;
+		return;
+	}
 
-	_history.add(_current_trans.top());
-	_current_trans.pop();
+	gettimeofday (&now, 0);
+	_current_trans->set_timestamp (now);
+
+	_history.add (_current_trans);
+	_current_trans = 0;
 }
 
 static bool
diff --git a/libs/pbd/pbd/undo.h b/libs/pbd/pbd/undo.h
index fb5152c293..11ff2bf321 100644
--- a/libs/pbd/pbd/undo.h
+++ b/libs/pbd/pbd/undo.h
@@ -37,6 +37,7 @@ class UndoTransaction : public Command
 	UndoTransaction ();
 	UndoTransaction (const UndoTransaction&);
 	UndoTransaction& operator= (const UndoTransaction&);
+	~UndoTransaction ();
 
 	void clear ();
 	bool empty() const;
@@ -66,9 +67,6 @@ class UndoTransaction : public Command
 
 	friend void command_death (UndoTransaction*, Command *);
 	
-	friend class UndoHistory;
-
-	~UndoTransaction ();
 	void about_to_explicitly_delete ();
 };