From 1796ee60b249d2ef534826ae36a2b88f2788e40c Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sun, 12 Jul 2020 00:38:56 +0200
Subject: [PATCH] Clean up b5e479df and expose API to queue latency-updates

---
 libs/ardour/ardour/audioengine.h |  4 +--
 libs/ardour/audioengine.cc       | 52 +++++++++++++++++++-------------
 2 files changed, 33 insertions(+), 23 deletions(-)

diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index f99d9bafd1..c2aaafae65 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -210,8 +210,7 @@ class LIBARDOUR_API AudioEngine : public PortManager, public SessionHandlePtr
 	static void destroy();
 	void died ();
 
-	/* The backend will cause these at the appropriate time(s)
-	 */
+	/* The backend will cause these at the appropriate time(s) */
 	int  process_callback (pframes_t nframes);
 	int  buffer_size_change (pframes_t nframes);
 	int  sample_rate_change (pframes_t nframes);
@@ -259,6 +258,7 @@ class LIBARDOUR_API AudioEngine : public PortManager, public SessionHandlePtr
 	void reset_silence_countdown ();
 
 	void add_pending_port_deletion (Port*);
+	void queue_latency_update (bool);
 
   private:
 	AudioEngine ();
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index e7073d63ae..f48f4761cf 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -1416,27 +1416,37 @@ void
 AudioEngine::latency_callback (bool for_playback)
 {
 	DEBUG_TRACE (DEBUG::BackendCallbacks, string_compose (X_("latency callback playback ? %1\n"), for_playback));
-	if (_session) {
-		if (in_process_thread ()) {
-			/* internal backends emit the latency callback in the rt-callback,
-			 * async to connect/disconnect or port creation/deletion.
-			 * All is fine.
-			 *
-			 * However jack 1/2 emit the callback in sync with creating the port
-			 * (or while handling the connection change).
-			 * e.g. JACK2 jack_port_register() blocks and the jack_latency_callback
-			 * from a different thread: https://pastebin.com/mitGBwpq
-			 * but at this point in time Ardour still holds the process callback
-			 * because JACK2 can process in parallel to latency callbacks.
-			 *
-			 * see also Session::update_latency() and git-ref 1983f56592dfea5f7498
-			 */
-			_session->update_latency (for_playback);
-		} else if (for_playback) {
-			g_atomic_int_set (&_pending_playback_latency_callback, 1);
-		} else {
-			g_atomic_int_set (&_pending_capture_latency_callback, 1);
-		}
+	if (!_session) {
+		return;
+	}
+
+	if (in_process_thread ()) {
+		/* internal backends emit the latency callback in the rt-callback,
+		 * async to connect/disconnect or port creation/deletion.
+		 * All is fine.
+		 */
+		_session->update_latency (for_playback);
+	} else {
+		/* However jack 1/2 emit the callback in sync with creating the port
+		 * (or while handling the connection change).
+		 * e.g. JACK2 jack_port_register() blocks and the jack_latency_callback
+		 * from a different thread: https://pastebin.com/mitGBwpq
+		 * but at this point in time Ardour still holds the process callback
+		 * because JACK2 can process in parallel to latency callbacks.
+		 *
+		 * see also Session::update_latency() and git-ref 1983f56592dfea5f7498
+		 */
+		queue_latency_update (for_playback);
+	}
+}
+
+void
+AudioEngine::queue_latency_update (bool for_playback)
+{
+	if (for_playback) {
+		g_atomic_int_set (&_pending_playback_latency_callback, 1);
+	} else {
+		g_atomic_int_set (&_pending_capture_latency_callback, 1);
 	}
 }