From 0786be859d8ad716f5b0eed53c3a82b4665c0efb Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sun, 3 Dec 2023 20:38:31 +0100
Subject: [PATCH] Retain TransportMaster Ports across sessions

Unloading a session should only remove session-ports.
This fixes Timecode master sync when switching snapshots
or sessions.
---
 libs/ardour/ardour/port_manager.h |  2 +-
 libs/ardour/audioengine.cc        |  2 +-
 libs/ardour/port_manager.cc       | 19 +++++++++++++------
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/libs/ardour/ardour/port_manager.h b/libs/ardour/ardour/port_manager.h
index dd9d53ae21..ed9605e808 100644
--- a/libs/ardour/ardour/port_manager.h
+++ b/libs/ardour/ardour/port_manager.h
@@ -186,7 +186,7 @@ public:
 
 	void set_port_pretty_name (std::string const&, std::string const&);
 
-	void remove_all_ports ();
+	void remove_session_ports ();
 
 	/** reset port-buffers. e.g. after freewheeling */
 	void reinit (bool with_ratio = false);
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index 18154151e5..fc052ef749 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -834,7 +834,7 @@ AudioEngine::remove_session ()
 		SessionHandlePtr::set_session (0);
 	}
 
-	remove_all_ports ();
+	remove_session_ports ();
 }
 
 void
diff --git a/libs/ardour/port_manager.cc b/libs/ardour/port_manager.cc
index f5aada8472..0b6681fefb 100644
--- a/libs/ardour/port_manager.cc
+++ b/libs/ardour/port_manager.cc
@@ -274,7 +274,7 @@ PortManager::clear_pending_port_deletions ()
 }
 
 void
-PortManager::remove_all_ports ()
+PortManager::remove_session_ports ()
 {
 	/* make sure that JACK callbacks that will be invoked as we cleanup
 	 * ports know that they have nothing to do.
@@ -282,13 +282,20 @@ PortManager::remove_all_ports ()
 
 	PBD::Unwinder<bool> uw (_port_remove_in_progress, true);
 
-	/* process lock MUST be held by caller
-	*/
+	/* process lock MUST be held by caller */
 
 	{
-		RCUWriter<Ports>         writer (_ports);
+		RCUWriter<Ports>            writer (_ports);
 		std::shared_ptr<Ports> ps = writer.get_copy ();
-		ps->clear ();
+
+		for (auto i = ps->begin (); i != ps->end (); ) {
+			std::shared_ptr<Port> port = i->second;
+			if (i->second->flags () & TransportMasterPort) {
+				++i;
+			} else {
+				i = ps->erase (i);
+			}
+		}
 	}
 
 	/* clear dead wood list in RCU */
@@ -857,7 +864,7 @@ PortManager::reestablish_ports ()
 
 	if (i != p->end ()) {
 		/* failed */
-		remove_all_ports ();
+		remove_session_ports ();
 		return -1;
 	}