Add MainOutVolume parameter type

This is similar to TrimAutomation, except intended to be available
on the master-bus' output, or a Route's _main_out delivery.

libs/ardour/ardour/types.h

@@ -163,6 +163,7 @@ enum AutomationType {
 	MonitoringAutomation,
 	BusSendLevel,
 	BusSendEnable,
+	MainOutVolume,
 
 	/* used only by Controllable Descriptor to access send parameters */
 

libs/ardour/ardour/value_as_string.h

@@ -53,7 +53,7 @@ value_as_string(const ARDOUR::ParameterDescriptor& desc,
 	// Value is not a scale point, print it normally
 	if (desc.unit == ARDOUR::ParameterDescriptor::MIDI_NOTE) {
 		snprintf(buf, sizeof(buf), "%s", ParameterDescriptor::midi_note_name (rint(v)).c_str());
-	} else if (desc.type == GainAutomation || desc.type == BusSendLevel || desc.type == TrimAutomation || desc.type == EnvelopeAutomation) {
+	} else if (desc.type == GainAutomation || desc.type == BusSendLevel || desc.type == TrimAutomation || desc.type == EnvelopeAutomation || desc.type == MainOutVolume) {
 		snprintf(buf, sizeof(buf), "%.1f dB", accurate_coefficient_to_dB (v));
 	} else if (desc.type == PanWidthAutomation) {
 		snprintf (buf, sizeof (buf), "%d%%", (int) floor (100.0 * v));

libs/ardour/automatable.cc

@@ -196,6 +196,8 @@ Automatable::describe_parameter (Evoral::Parameter param)
 		return _("Send");
 	} else if (param.type() == TrimAutomation) {
 		return _("Trim");
+	} else if (param.type() == MainOutVolume) {
+		return _("Master Volume");
 	} else if (param.type() == MuteAutomation) {
 		return _("Mute");
 	} else if (param.type() == PanAzimuthAutomation) {
@@ -554,6 +556,8 @@ Automatable::control_factory(const Evoral::Parameter& param)
 		control = new GainControl(_a_session, param);
 	} else if (param.type() == TrimAutomation) {
 		control = new GainControl(_a_session, param);
+	} else if (param.type() == MainOutVolume) {
+		control = new GainControl(_a_session, param);
 	} else if (param.type() == BusSendLevel) {
 		control = new GainControl(_a_session, param);
 	} else if (param.type() == PanAzimuthAutomation || param.type() == PanWidthAutomation || param.type() == PanElevationAutomation) {

libs/ardour/automation_list.cc

@@ -231,6 +231,7 @@ AutomationList::default_interpolation () const
 		case EnvelopeAutomation:
 			return ControlList::Exponential;
 			break;
+		case MainOutVolume:
 		case TrimAutomation:
 			return ControlList::Logarithmic;
 			break;

libs/ardour/enums.cc

@@ -200,6 +200,7 @@ setup_enum_writer ()
 	REGISTER_ENUM (MonitoringAutomation);
 	REGISTER_ENUM (BusSendLevel);
 	REGISTER_ENUM (BusSendEnable);
+	REGISTER_ENUM (MainOutVolume);
 	REGISTER (_AutomationType);
 
 	REGISTER_ENUM (Off);

libs/ardour/event_type_map.cc

@@ -139,6 +139,8 @@ EventTypeMap::from_symbol(const string& str) const
 		p_type = BusSendLevel;
 	} else if (str == "trim") {
 		p_type = TrimAutomation;
+	} else if (str == "main-out-volume") {
+		p_type = MainOutVolume;
 	} else if (str == "solo") {
 		p_type = SoloAutomation;
 	} else if (str == "solo-iso") {
@@ -241,6 +243,8 @@ EventTypeMap::to_symbol(const Evoral::Parameter& param) const
 		return "send";
 	} else if (t == TrimAutomation) {
 		return "trim";
+	} else if (t == MainOutVolume) {
+		return "main-out-volume";
 	} else if (t == PanAzimuthAutomation) {
 		return "pan-azimuth";
 	} else if (t == PanElevationAutomation) {

libs/ardour/parameter_descriptor.cc

@@ -71,6 +71,12 @@ ParameterDescriptor::ParameterDescriptor(const Evoral::Parameter& parameter)
 		normal = 1.0f;
 		logarithmic = true;
 		break;
+	case MainOutVolume:
+		upper  = 100; // +40dB
+		lower  = .01; // -40dB
+		normal = 1.0f;
+		logarithmic = true;
+		break;
 	case PanAzimuthAutomation:
 		normal = 0.5f; // there really is no _normal but this works for stereo, sort of
 		upper  = 1.0f;
@@ -198,7 +204,7 @@ ParameterDescriptor::update_steps()
 	if (unit == ParameterDescriptor::MIDI_NOTE) {
 		step      = smallstep = 1;  // semitone
 		largestep = 12;             // octave
-	} else if (type == GainAutomation || type == TrimAutomation || type == BusSendLevel) {
+	} else if (type == GainAutomation || type == TrimAutomation || type == BusSendLevel || type == MainOutVolume) {
 		/* dB_coeff_step gives a step normalized for [0, max_gain].  This is
 		   like "slider position", so we convert from "slider position" to gain
 		   to have the correct unit here. */
@@ -314,11 +320,15 @@ ParameterDescriptor::to_interface (float val, bool rotary) const
 	val = std::min (upper, std::max (lower, val));
 	switch(type) {
 		case GainAutomation:
+			/* fallthrough */
 		case BusSendLevel:
+			/* fallthrough */
 		case EnvelopeAutomation:
 			val = gain_to_slider_position_with_max (val, upper);
 			break;
 		case TrimAutomation:
+			/* fallthrough */
+		case MainOutVolume:
 			{
 				const float lower_db = accurate_coefficient_to_dB (lower);
 				const float range_db = accurate_coefficient_to_dB (upper) - lower_db;