From b121ee157e820b2b86fe3ec7244226d5e82fca0c Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 7 Aug 2024 01:15:50 +0200
Subject: [PATCH] Update Auto-Input meter policy

This replaces rule #17, 27, 43 and 59 on
https://manual.ardour.org/appendix/monitor-modes/

"Meter (What you see)" changes to 'Disk (Audio)'
aka "what you hear" in those cases.

This way "what you see" is always "what you hear".
Monitoring inputs is more conveniently done using
the Recorder Page.
---
 libs/ardour/ardour/track.h |  9 ++--
 libs/ardour/track.cc       | 85 ++++++++++++++++++++++++++++++--------
 2 files changed, 73 insertions(+), 21 deletions(-)

diff --git a/libs/ardour/ardour/track.h b/libs/ardour/ardour/track.h
index 6c9bc4db8a..8d84957d95 100644
--- a/libs/ardour/ardour/track.h
+++ b/libs/ardour/ardour/track.h
@@ -22,6 +22,7 @@
 #ifndef __ardour_track_h__
 #define __ardour_track_h__
 
+#include <boost/optional.hpp>
 #include <memory>
 
 #include "pbd/enum_convert.h"
@@ -193,10 +194,12 @@ public:
 protected:
 	XMLNode& state (bool save_template) const;
 
-	std::shared_ptr<Playlist>   _playlists[DataType::num_types];
+	void update_input_meter ();
 
-	MeterPoint    _saved_meter_point;
-	TrackMode     _mode;
+	std::shared_ptr<Playlist>   _playlists[DataType::num_types];
+	boost::optional<MeterPoint> _saved_meter_point;
+	bool                        _record_prepared;
+	TrackMode                   _mode;
 
 	//private: (FIXME)
 	struct FreezeRecordProcessorInfo {
diff --git a/libs/ardour/track.cc b/libs/ardour/track.cc
index 00f22e3956..d91c4b9a47 100644
--- a/libs/ardour/track.cc
+++ b/libs/ardour/track.cc
@@ -64,7 +64,7 @@ using namespace PBD;
 
 Track::Track (Session& sess, string name, PresentationInfo::Flag flag, TrackMode mode, DataType default_type)
 	: Route (sess, name, flag, default_type)
-	, _saved_meter_point (_meter_point)
+	, _record_prepared (false)
 	, _mode (mode)
 	, _alignment_choice (Automatic)
 	, _pending_name_change (false)
@@ -142,6 +142,8 @@ Track::init ()
 	}
 
 	_session.config.ParameterChanged.connect_same_thread (*this, boost::bind (&Track::parameter_changed, this, _1));
+	_session.RecordStateChanged.connect_same_thread (*this, boost::bind (&Track::update_input_meter, this));
+	_session.TransportStateChange.connect_same_thread (*this, boost::bind (&Track::update_input_meter, this));
 
 	_monitoring_control->Changed.connect_same_thread (*this, boost::bind (&Track::monitoring_changed, this, _1, _2));
 	_record_safe_control->Changed.connect_same_thread (*this, boost::bind (&Track::record_safe_changed, this, _1, _2));
@@ -202,7 +204,9 @@ Track::state (bool save_template) const
 	root.add_child_nocopy (_record_safe_control->get_state ());
 	root.add_child_nocopy (_record_enable_control->get_state ());
 
-	root.set_property (X_("saved-meter-point"), _saved_meter_point);
+	if (_saved_meter_point) {
+		root.set_property (X_("saved-meter-point"), _saved_meter_point.value ());
+	}
 	root.set_property (X_("alignment-choice"), _alignment_choice);
 
 	return root;
@@ -277,11 +281,11 @@ Track::set_state (const XMLNode& node, int version)
 		}
 	}
 
-	if (!node.get_property (X_("saved-meter-point"), _saved_meter_point)) {
-		_saved_meter_point = _meter_point;
+	MeterPoint mp;
+	if (node.get_property (X_("saved-meter-point"), mp)) {
+		_saved_meter_point = mp;
 	}
 
-
 	AlignChoice ac;
 
 	if (node.get_property (X_("alignment-choice"), ac)) {
@@ -334,11 +338,6 @@ Track::prep_record_enabled (bool yn)
 		return -1;
 	}
 
-	/* keep track of the meter point as it was before we rec-enabled */
-	if (!_disk_writer->record_enabled()) {
-		_saved_meter_point = _meter_point;
-	}
-
 	bool will_follow;
 
 	if (yn) {
@@ -347,17 +346,65 @@ Track::prep_record_enabled (bool yn)
 		will_follow = _disk_writer->prep_record_disable ();
 	}
 
-	if (will_follow) {
-		if (yn) {
-			if (_meter_point != MeterCustom) {
-				set_meter_point (MeterInput);
-			}
-		} else {
-			set_meter_point (_saved_meter_point);
+	if (!will_follow) {
+		return -1;
+	}
+
+	_record_prepared = yn;
+	update_input_meter ();
+
+	return 0;
+}
+
+void
+Track::update_input_meter ()
+{
+	if (_session.loading ()) {
+		return;
+	}
+	/* meter input if _record_prepared,
+	 * except if Rolling, but not recording (master-rec-enable is off) and auto-input is enabled
+	 */
+	bool monitor_input = false;
+
+	if (_record_prepared) {
+		/* actually rolling (no count-in, pre-roll) */
+		bool const rolling     = 0 != _session.transport_speed();
+		bool const recording   = _session.actively_recording ();
+		bool const auto_input  = _session.config.get_auto_input ();
+
+		if (!(rolling && !recording && auto_input)) {
+			monitor_input = true;
 		}
 	}
 
-	return 0;
+	if (monitor_input) {
+		if (_saved_meter_point) {
+			/* already monitoring input */
+			return;
+		}
+		MeterPoint mp = meter_point ();
+		if (mp == MeterInput) {
+			/* user explicitly monitors input, do nothing */
+			return;
+		}
+
+		/* keep track of the meter point as it was before we rec-enabled */
+		_saved_meter_point = mp;
+
+		if (mp != MeterCustom) {
+			set_meter_point (MeterInput);
+		}
+
+	} else {
+		if (!_saved_meter_point) {
+			return;
+		}
+		if (_saved_meter_point != MeterCustom) {
+			set_meter_point (_saved_meter_point.value ());
+		}
+		_saved_meter_point.reset ();
+	}
 }
 
 void
@@ -397,6 +444,8 @@ Track::parameter_changed (string const & p)
 		if (_session.config.get_track_name_take()) {
 			resync_take_name ();
 		}
+	} else if (p == "auto-input") {
+		update_input_meter ();
 	}
 }