From bebca374473032e2cec1c68d55dfd17345e5ff29 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 22 Sep 2020 21:42:52 +0200
Subject: [PATCH] Cache the latency of the metronome's port

---
 libs/ardour/ardour/session.h |  3 +++
 libs/ardour/session.cc       |  3 +++
 libs/ardour/session_click.cc | 14 ++++++++++++--
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 2e03c5af04..956a50eaf4 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -2023,6 +2023,8 @@ private:
 	samplecnt_t                   click_length;
 	samplecnt_t                   click_emphasis_length;
 	mutable Glib::Threads::RWLock click_lock;
+	samplecnt_t                  _click_io_latency;
+	PBD::ScopedConnection        _click_io_connection;
 
 	static const Sample     default_click[];
 	static const samplecnt_t default_click_length;
@@ -2038,6 +2040,7 @@ private:
 	void click (samplepos_t start, samplecnt_t nframes);
 	void run_click (samplepos_t start, samplecnt_t nframes);
 	void add_click (samplepos_t pos, bool emphasis);
+	void click_io_resync_latency (bool);
 
 	/* range playback */
 
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index dc14cb4259..25ec932a87 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -599,6 +599,7 @@ Session::destroy ()
 
 	/* remove I/O objects that we (the session) own */
 	_click_io.reset ();
+	_click_io_connection.disconnect ();
 
 	{
 		Glib::Threads::Mutex::Lock lm (controllables_lock);
@@ -828,6 +829,8 @@ Session::setup_click ()
 	} else {
 		setup_click_state (0);
 	}
+	click_io_resync_latency (true);
+	LatencyUpdated.connect_same_thread (_click_io_connection, boost::bind (&Session::click_io_resync_latency, this, _1));
 }
 
 void
diff --git a/libs/ardour/session_click.cc b/libs/ardour/session_click.cc
index 3a0d50ff65..4b890979a0 100644
--- a/libs/ardour/session_click.cc
+++ b/libs/ardour/session_click.cc
@@ -76,7 +76,7 @@ Session::click (samplepos_t cycle_start, samplecnt_t nframes)
 	 * we need to prepare frames that the user will hear
 	 * in "output latency's" worth of time.
 	 */
-	samplecnt_t offset = _click_io->connected_latency (true);
+	samplecnt_t offset = _click_io_latency;
 
 	Glib::Threads::RWLock::WriterLock clickm (click_lock, Glib::Threads::TRY_LOCK);
 
@@ -159,7 +159,7 @@ Session::run_click (samplepos_t start, samplepos_t nframes)
 	Glib::Threads::RWLock::ReaderLock clickm (click_lock, Glib::Threads::TRY_LOCK);
 
 	/* align to output */
-	start += _click_io->connected_latency (true);
+	start += _click_io_latency;
 
 	if (!clickm.locked() || click_data == 0) {
 		_click_io->silence (nframes);
@@ -349,3 +349,13 @@ Session::clear_clicks ()
 	clicks.clear ();
 	_clicks_cleared = _transport_sample;
 }
+
+void
+Session::click_io_resync_latency (bool playback)
+{
+	if (deletion_in_progress() || !playback) {
+		return;
+	}
+
+	_click_io_latency = _click_io->connected_latency (true);
+}