From 42fef352992f83bfd135f17726a269056a4684fc Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 17 Jul 2019 17:04:25 +0200
Subject: [PATCH] Update Latency GUI behavior

This allows to set the current nominal latency as custom latency.
Previously it was not possible to use the "initial_value" as custom
parameter.
---
 gtk2_ardour/latency_gui.cc | 28 ++++++++++++++++------------
 gtk2_ardour/latency_gui.h  |  8 +++++---
 2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/gtk2_ardour/latency_gui.cc b/gtk2_ardour/latency_gui.cc
index 61e9d15eea..a323b4fbc2 100644
--- a/gtk2_ardour/latency_gui.cc
+++ b/gtk2_ardour/latency_gui.cc
@@ -65,12 +65,12 @@ LatencyBarController::get_label (double&)
 	return s.str ();
 }
 
-LatencyGUI::LatencyGUI (Latent& l, samplepos_t sr, samplepos_t psz, bool apply)
+LatencyGUI::LatencyGUI (Latent& l, samplepos_t sr, samplepos_t psz)
 	: _latent (l)
-	, initial_value (_latent.effective_latency ())
 	, sample_rate (sr)
 	, period_size (psz)
 	, ignored (new PBD::IgnorableControllable())
+	, _ignore_change (false)
 	, adjustment (0, 0.0, sample_rate, 1.0, sample_rate / 1000.0f) /* max 1 second, step by samples, page by msecs */
 	, bc (adjustment, this)
 	, reset_button (_("Reset"))
@@ -104,6 +104,12 @@ LatencyGUI::LatencyGUI (Latent& l, samplepos_t sr, samplepos_t psz, bool apply)
 	plus_button.signal_clicked().connect (sigc::bind (sigc::mem_fun (*this, &LatencyGUI::change_latency_from_button), 1));
 	reset_button.signal_clicked().connect (sigc::mem_fun (*this, &LatencyGUI::reset));
 
+	/* Limit value to adjustment range (max = sample_rate).
+	 * Otherwise if the signal_latency() is larger than the adjustment's max,
+	 * LatencyGUI::finish() would set the adjustment's max value as custom-latency.
+	 */
+	adjustment.set_value (std::min (sample_rate, _latent.signal_latency ()));
+
 	adjustment.signal_value_changed().connect (sigc::mem_fun (*this, &LatencyGUI::finish));
 
 	bc.set_size_request (-1, 25);
@@ -117,28 +123,26 @@ LatencyGUI::LatencyGUI (Latent& l, samplepos_t sr, samplepos_t psz, bool apply)
 void
 LatencyGUI::finish ()
 {
-	samplepos_t new_value = (samplepos_t) adjustment.get_value();
-	if (new_value != initial_value) {
-		_latent.set_user_latency (new_value);
+	if (_ignore_change) {
+		return;
 	}
+	samplepos_t new_value = (samplepos_t) adjustment.get_value();
+	_latent.set_user_latency (new_value);
 }
 
 void
 LatencyGUI::reset ()
 {
 	_latent.unset_user_latency ();
-	initial_value = std::min (sample_rate, _latent.signal_latency ());
-	adjustment.set_value (initial_value);
+	PBD::Unwinder<bool> uw (_ignore_change, true);
+	adjustment.set_value (std::min (sample_rate, _latent.signal_latency ()));
 }
 
 void
 LatencyGUI::refresh ()
 {
-	/* limit to adjustment range, otherwise LatencyGUI::finish() would
-	 * set the adjustment's value as custom-latency
-	 */
-	initial_value = std::min (sample_rate, _latent.effective_latency ());
-	adjustment.set_value (initial_value);
+	PBD::Unwinder<bool> uw (_ignore_change, true);
+	adjustment.set_value (std::min (sample_rate, _latent.effective_latency ()));
 }
 
 void
diff --git a/gtk2_ardour/latency_gui.h b/gtk2_ardour/latency_gui.h
index 943944571e..25e469abfc 100644
--- a/gtk2_ardour/latency_gui.h
+++ b/gtk2_ardour/latency_gui.h
@@ -60,17 +60,19 @@ public:
 	LatencyGUI (ARDOUR::Latent&, samplepos_t sample_rate, samplepos_t period_size);
 	~LatencyGUI() { }
 
-	void finish ();
-	void reset ();
 	void refresh ();
 
 private:
+	void reset ();
+	void finish ();
+
 	ARDOUR::Latent& _latent;
-	samplepos_t initial_value;
 	samplepos_t sample_rate;
 	samplepos_t period_size;
+
 	boost::shared_ptr<PBD::IgnorableControllable> ignored;
 
+	bool _ignore_change;
 	Gtk::Adjustment adjustment;
 	LatencyBarController bc;
 	Gtk::HBox hbox1;