From 4d81e3ec07cf3d08b7688c62e5fddd0170132fb8 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Fri, 25 Nov 2016 18:07:43 +0100
Subject: [PATCH] RAII to postpone processor changes/graph recalculation

---
 libs/ardour/ardour/session.h     | 48 +++++++++++++++++++++++---------
 libs/ardour/session.cc           | 21 ++++++--------
 libs/ardour/session_transport.cc |  2 +-
 3 files changed, 45 insertions(+), 26 deletions(-)

diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 7ae2fb4bd8..b2409e3da6 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -581,20 +581,40 @@ class LIBARDOUR_API Session : public PBD::StatefulDestructible, public PBD::Scop
 	StateOfTheState state_of_the_state() const { return _state_of_the_state; }
 
 	class StateProtector {
-	                                        public:
-		StateProtector (Session* s) : _session (s) {
-			g_atomic_int_inc (&s->_suspend_save);
-		}
-		~StateProtector () {
-			if (g_atomic_int_dec_and_test (&_session->_suspend_save)) {
-				while (_session->_save_queued) {
-					_session->_save_queued = false;
-					_session->save_state ("");
+		public:
+			StateProtector (Session* s) : _session (s) {
+				g_atomic_int_inc (&s->_suspend_save);
+			}
+			~StateProtector () {
+				if (g_atomic_int_dec_and_test (&_session->_suspend_save)) {
+					while (_session->_save_queued) {
+						_session->_save_queued = false;
+						_session->save_state ("");
+					}
 				}
 			}
-		}
-            private:
-		Session * _session;
+		private:
+			Session * _session;
+	};
+
+	class ProcessorChangeBlocker {
+		public:
+			ProcessorChangeBlocker (Session* s, bool rc = true)
+				: _session (s)
+				, _reconfigure_on_delete (rc)
+			{
+				g_atomic_int_inc (&s->_ignore_route_processor_changes);
+			}
+			~ProcessorChangeBlocker () {
+				if (g_atomic_int_dec_and_test (&_session->_ignore_route_processor_changes)) {
+					if (_reconfigure_on_delete) {
+						_session->route_processors_changed (RouteProcessorChange ());
+					}
+				}
+			}
+		private:
+			Session* _session;
+			bool _reconfigure_on_delete;
 	};
 
 	void add_route_group (RouteGroup *);
@@ -2005,7 +2025,9 @@ class LIBARDOUR_API Session : public PBD::StatefulDestructible, public PBD::Scop
 	GraphEdges _current_route_graph;
 
 	void ensure_route_presentation_info_gap (PresentationInfo::order_t, uint32_t gap_size);
-	bool ignore_route_processor_changes;
+
+	friend class    ProcessorChangeBlocker;
+	gint            _ignore_route_processor_changes; /* atomic */
 
 	MidiClockTicker* midi_clock;
 
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index c0041ef555..723960749e 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -312,7 +312,7 @@ Session::Session (AudioEngine &eng,
 	, _step_editors (0)
 	, _suspend_timecode_transmission (0)
 	,  _speakers (new Speakers)
-	, ignore_route_processor_changes (false)
+	, _ignore_route_processor_changes (0)
 	, midi_clock (0)
 	, _scene_changer (0)
 	, _midi_ports (0)
@@ -1129,7 +1129,7 @@ Session::remove_monitor_section ()
 
 
 		boost::shared_ptr<RouteList> r = routes.reader ();
-		PBD::Unwinder<bool> uw (ignore_route_processor_changes, true);
+		ProcessorChangeBlocker  pcb (this, false);
 
 		for (RouteList::iterator x = r->begin(); x != r->end(); ++x) {
 
@@ -1289,7 +1289,7 @@ Session::add_monitor_section ()
 
 	boost::shared_ptr<RouteList> rls = routes.reader ();
 
-	PBD::Unwinder<bool> uw (ignore_route_processor_changes, true);
+	ProcessorChangeBlocker  pcb (this, false /* XXX */);
 
 	for (RouteList::iterator x = rls->begin(); x != rls->end(); ++x) {
 
@@ -1413,7 +1413,7 @@ Session::reset_monitor_section ()
 
 	boost::shared_ptr<RouteList> rls = routes.reader ();
 
-	PBD::Unwinder<bool> uw (ignore_route_processor_changes, true);
+	ProcessorChangeBlocker pcb (this, false);
 
 	for (RouteList::iterator x = rls->begin(); x != rls->end(); ++x) {
 
@@ -3662,7 +3662,7 @@ Session::remove_routes (boost::shared_ptr<RouteList> routes_to_remove)
 			/* if the monitoring section had a pointer to this route, remove it */
 			if (_monitor_out && !(*iter)->is_master() && !(*iter)->is_monitor()) {
 				Glib::Threads::Mutex::Lock lm (AudioEngine::instance()->process_lock ());
-				PBD::Unwinder<bool> uw (ignore_route_processor_changes, true);
+				ProcessorChangeBlocker pcb (this, false);
 				(*iter)->remove_aux_or_listen (_monitor_out);
 			}
 
@@ -6216,14 +6216,11 @@ Session::update_route_record_state ()
 void
 Session::listen_position_changed ()
 {
-	{
-		boost::shared_ptr<RouteList> r = routes.reader ();
-		PBD::Unwinder<bool> uw (ignore_route_processor_changes, true);
-		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
-			(*i)->listen_position_changed ();
-		}
+	ProcessorChangeBlocker pcb (this);
+	boost::shared_ptr<RouteList> r = routes.reader ();
+	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+		(*i)->listen_position_changed ();
 	}
-	route_processors_changed (RouteProcessorChange ());
 }
 
 void
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index 8771af46aa..68e6f49342 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -1992,7 +1992,7 @@ Session::xrun_recovery ()
 void
 Session::route_processors_changed (RouteProcessorChange c)
 {
-	if (ignore_route_processor_changes) {
+	if (g_atomic_int_get (&_ignore_route_processor_changes) > 0) {
 		return;
 	}
 
-- 
2.30.2