change return type of AutomationControl::actually_set_value() from void to bool, to indicate if value was changed.

Don't call Session::set_dirty() when no change occurs

26 files changed, 76 insertions, 59 deletions

diff --git a/libs/ardour/ardour/automation_control.h b/libs/ardour/ardour/automation_control.h
index 158996133c..fddb0685ab 100644
--- a/libs/ardour/ardour/automation_control.h
+++ b/libs/ardour/ardour/automation_control.h
@@ -105,7 +105,7 @@ class LIBARDOUR_API AutomationControl
 	 * this is only used by automation playback.
 	 */
 	void set_value_unchecked (double val) {
-		actually_set_value (val, PBD::Controllable::NoGroup);
+		(void) actually_set_value (val, PBD::Controllable::NoGroup);
 	}
 
 	double lower()   const { return _desc.lower; }
@@ -134,7 +134,7 @@ class LIBARDOUR_API AutomationControl
 	   Controllable::Changed signal is emitted when necessary.
 	*/
 
-	virtual void actually_set_value (double value, PBD::Controllable::GroupControlDisposition);
+	virtual bool actually_set_value (double value, PBD::Controllable::GroupControlDisposition);
 
 	/* Session needs to call this method before it queues up the real
 	   change for execution in a realtime context. C++ access control sucks.
diff --git a/libs/ardour/ardour/midi_track.h b/libs/ardour/ardour/midi_track.h
index f756812e71..8a0f8c9f95 100644
--- a/libs/ardour/ardour/midi_track.h
+++ b/libs/ardour/ardour/midi_track.h
@@ -95,7 +95,7 @@ public:
 		MidiTrack* _route;
 
 	private:
-		void actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override);
+		bool actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override);
 	};
 
 	virtual void set_parameter_automation_state (Evoral::Parameter param, AutoState);
diff --git a/libs/ardour/ardour/monitor_control.h b/libs/ardour/ardour/monitor_control.h
index b18517255e..362bcfbc30 100644
--- a/libs/ardour/ardour/monitor_control.h
+++ b/libs/ardour/ardour/monitor_control.h
@@ -46,7 +46,7 @@ class LIBARDOUR_API MonitorControl : public SlavableAutomationControl
 	XMLNode& get_state ();
 
   protected:
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 
   private:
 	Monitorable& _monitorable;
diff --git a/libs/ardour/ardour/mute_control.h b/libs/ardour/ardour/mute_control.h
index 909f0cbf02..b324e32908 100644
--- a/libs/ardour/ardour/mute_control.h
+++ b/libs/ardour/ardour/mute_control.h
@@ -71,7 +71,7 @@ class LIBARDOUR_API MuteControl : public SlavableAutomationControl
 
   protected:
 	void master_changed (bool, PBD::Controllable::GroupControlDisposition, boost::shared_ptr<AutomationControl>);
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 
 	void pre_remove_master (boost::shared_ptr<AutomationControl>);
 	void post_add_master (boost::shared_ptr<AutomationControl>);
diff --git a/libs/ardour/ardour/pan_controllable.h b/libs/ardour/ardour/pan_controllable.h
index 82aa60fe10..30130e35c8 100644
--- a/libs/ardour/ardour/pan_controllable.h
+++ b/libs/ardour/ardour/pan_controllable.h
@@ -51,7 +51,7 @@ class LIBARDOUR_API PanControllable : public AutomationControl
 
   private:
 	Pannable* owner;
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 };
 
 } // namespace
diff --git a/libs/ardour/ardour/phase_control.h b/libs/ardour/ardour/phase_control.h
index 0693c8ee50..489673db2d 100644
--- a/libs/ardour/ardour/phase_control.h
+++ b/libs/ardour/ardour/phase_control.h
@@ -60,7 +60,7 @@ class LIBARDOUR_API PhaseControl : public AutomationControl
 	XMLNode& get_state ();
 
   protected:
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 
   private:
 	boost::dynamic_bitset<> _phase_invert;
diff --git a/libs/ardour/ardour/plugin_insert.h b/libs/ardour/ardour/plugin_insert.h
index 474df73e41..d3936cc797 100644
--- a/libs/ardour/ardour/plugin_insert.h
+++ b/libs/ardour/ardour/plugin_insert.h
@@ -198,7 +198,7 @@ class LIBARDOUR_API PluginInsert : public Processor
 
 	private:
 		PluginInsert* _plugin;
-		void actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override);
+		bool actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override);
 	};
 
 	/** A control that manipulates a plugin property (message). */
@@ -212,7 +212,7 @@ class LIBARDOUR_API PluginInsert : public Processor
 		double get_value (void) const;
 		XMLNode& get_state();
         protected:
-		void actually_set_value (double value, PBD::Controllable::GroupControlDisposition);
+		bool actually_set_value (double value, PBD::Controllable::GroupControlDisposition);
 
 	private:
 		PluginInsert* _plugin;
diff --git a/libs/ardour/ardour/record_enable_control.h b/libs/ardour/ardour/record_enable_control.h
index c5cb65c597..a9c4750eea 100644
--- a/libs/ardour/ardour/record_enable_control.h
+++ b/libs/ardour/ardour/record_enable_control.h
@@ -49,7 +49,7 @@ class LIBARDOUR_API RecordEnableControl : public SlavableAutomationControl
 	void set_value (double, PBD::Controllable::GroupControlDisposition);
 
   protected:
-	void actually_set_value (double val, Controllable::GroupControlDisposition gcd);
+	bool  actually_set_value (double val, Controllable::GroupControlDisposition gcd);
 	void do_pre_realtime_queue_stuff (double value);
 
   private:
diff --git a/libs/ardour/ardour/record_safe_control.h b/libs/ardour/ardour/record_safe_control.h
index ef062aa9f0..c7432cf3d4 100644
--- a/libs/ardour/ardour/record_safe_control.h
+++ b/libs/ardour/ardour/record_safe_control.h
@@ -39,7 +39,7 @@ class LIBARDOUR_API RecordSafeControl : public SlavableAutomationControl
 	~RecordSafeControl() {}
 
   protected:
-	void actually_set_value (double val, Controllable::GroupControlDisposition gcd);
+	bool actually_set_value (double val, Controllable::GroupControlDisposition gcd);
 
   private:
 	Recordable& _recordable;
diff --git a/libs/ardour/ardour/slavable_automation_control.h b/libs/ardour/ardour/slavable_automation_control.h
index 7e46dd5a74..c7133df89d 100644
--- a/libs/ardour/ardour/slavable_automation_control.h
+++ b/libs/ardour/ardour/slavable_automation_control.h
@@ -102,7 +102,7 @@ class LIBARDOUR_API SlavableAutomationControl : public AutomationControl
 
 	void   master_going_away (boost::weak_ptr<AutomationControl>);
 	double get_value_locked() const;
-	void   actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override);
+	bool   actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override);
 	void   update_boolean_masters_records (boost::shared_ptr<AutomationControl>);
 
 	virtual void   master_changed (bool from_self, GroupControlDisposition gcd, boost::shared_ptr<AutomationControl>);
diff --git a/libs/ardour/ardour/solo_control.h b/libs/ardour/ardour/solo_control.h
index 3f0f522fc3..4678ca6049 100644
--- a/libs/ardour/ardour/solo_control.h
+++ b/libs/ardour/ardour/solo_control.h
@@ -96,7 +96,7 @@ class LIBARDOUR_API SoloControl : public SlavableAutomationControl
 	XMLNode& get_state ();
 
   protected:
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 	void master_changed (bool from_self, GroupControlDisposition, boost::shared_ptr<AutomationControl> m);
 	void pre_remove_master (boost::shared_ptr<AutomationControl>);
 	void post_add_master (boost::shared_ptr<AutomationControl>);
diff --git a/libs/ardour/ardour/solo_isolate_control.h b/libs/ardour/ardour/solo_isolate_control.h
index 1e49469067..e77591e272 100644
--- a/libs/ardour/ardour/solo_isolate_control.h
+++ b/libs/ardour/ardour/solo_isolate_control.h
@@ -74,7 +74,7 @@ class LIBARDOUR_API SoloIsolateControl : public SlavableAutomationControl
 
   protected:
 	void master_changed (bool from_self, PBD::Controllable::GroupControlDisposition gcd, boost::shared_ptr<AutomationControl>);
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 
   private:
 	Soloable&      _soloable;
diff --git a/libs/ardour/ardour/solo_safe_control.h b/libs/ardour/ardour/solo_safe_control.h
index e969959e94..ba31692589 100644
--- a/libs/ardour/ardour/solo_safe_control.h
+++ b/libs/ardour/ardour/solo_safe_control.h
@@ -44,7 +44,7 @@ class LIBARDOUR_API SoloSafeControl : public SlavableAutomationControl
 	XMLNode& get_state ();
 
   protected:
-	void actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
+	bool actually_set_value (double, PBD::Controllable::GroupControlDisposition group_override);
 
   private:
 	bool _solo_safe;
diff --git a/libs/ardour/automation_control.cc b/libs/ardour/automation_control.cc
index 9a6590ebe8..03871cf07c 100644
--- a/libs/ardour/automation_control.cc
+++ b/libs/ardour/automation_control.cc
@@ -116,11 +116,11 @@ AutomationControl::set_value (double val, PBD::Controllable::GroupControlDisposi
  *  (e.g. record if necessary, etc.)
  *  @param value `user' value
  */
-void
+bool
 AutomationControl::actually_set_value (double value, PBD::Controllable::GroupControlDisposition gcd)
 {
 	bool to_list = _list && boost::dynamic_pointer_cast<AutomationList>(_list)->automation_write();
-	//const double old_value = Control::user_double ();
+	const double old_value = get_value ();
 
 	Control::set_double (value, _session.transport_frame(), to_list);
 
@@ -128,7 +128,12 @@ AutomationControl::actually_set_value (double value, PBD::Controllable::GroupCon
 	//std::cerr << "++++ Changed (" << enum_2_string (at) << ", " << enum_2_string (gcd) << ") = " << value
 	//<< " (was " << old_value << ") @ " << this << std::endl;
 
-	Changed (true, gcd);
+	if (old_value != value) {
+		Changed (true, gcd);
+		return true;
+	}
+
+	return false;
 }
 
 void
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index f1344e7697..ac5cfc098a 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -712,7 +712,7 @@ MidiTrack::set_parameter_automation_state (Evoral::Parameter param, AutoState st
 	}
 }
 
-void
+bool
 MidiTrack::MidiControl::actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override)
 {
 	const Evoral::Parameter &parameter = _list ? _list->parameter() : Control::parameter();
@@ -732,7 +732,7 @@ MidiTrack::MidiControl::actually_set_value (double val, PBD::Controllable::Group
 	}
 
 	if (!valid) {
-		return;
+		return false;
 	}
 
 	assert(val <= desc.upper);
@@ -776,7 +776,7 @@ MidiTrack::MidiControl::actually_set_value (double val, PBD::Controllable::Group
 		_route->write_immediate_event(size,  ev);
 	}
 
-	AutomationControl::actually_set_value(val, group_override);
+	return AutomationControl::actually_set_value(val, group_override);
 }
 
 void
diff --git a/libs/ardour/monitor_control.cc b/libs/ardour/monitor_control.cc
index 907a7473d7..a5907f769f 100644
--- a/libs/ardour/monitor_control.cc
+++ b/libs/ardour/monitor_control.cc
@@ -36,7 +36,7 @@ MonitorControl::MonitorControl (Session& session, std::string const & name, Moni
 	set_flags (Controllable::Flag (flags() | Controllable::RealTime));
 }
 
-void
+bool
 MonitorControl::actually_set_value (double val, Controllable::GroupControlDisposition gcd)
 {
 	int v = (int) val;
@@ -48,11 +48,11 @@ MonitorControl::actually_set_value (double val, Controllable::GroupControlDispos
 		break;
 	default:
 		/* illegal value */
-		return;
+		return false;
 	}
 
 	_monitoring = MonitorChoice (v);
-	AutomationControl::actually_set_value (val, gcd);
+	return AutomationControl::actually_set_value (val, gcd);
 }
 
 XMLNode&
diff --git a/libs/ardour/mute_control.cc b/libs/ardour/mute_control.cc
index 5b38547366..1b7f0f08f8 100644
--- a/libs/ardour/mute_control.cc
+++ b/libs/ardour/mute_control.cc
@@ -74,7 +74,7 @@ MuteControl::pre_remove_master (boost::shared_ptr<AutomationControl> m)
 	}
 }
 
-void
+bool
 MuteControl::actually_set_value (double val, Controllable::GroupControlDisposition gcd)
 {
 	if (muted_by_self() != bool (val)) {
@@ -86,7 +86,7 @@ MuteControl::actually_set_value (double val, Controllable::GroupControlDispositi
 		_muteable.act_on_mute ();
 	}
 
-	SlavableAutomationControl::actually_set_value (val, gcd);
+	return SlavableAutomationControl::actually_set_value (val, gcd);
 }
 
 void
diff --git a/libs/ardour/pan_controllable.cc b/libs/ardour/pan_controllable.cc
index 89842b124b..e4ad360910 100644
--- a/libs/ardour/pan_controllable.cc
+++ b/libs/ardour/pan_controllable.cc
@@ -34,15 +34,14 @@ PanControllable::lower () const
         }
 }
 
-void
+bool
 PanControllable::actually_set_value (double v, Controllable::GroupControlDisposition group_override)
 {
 	boost::shared_ptr<Panner> p = owner->panner();
 
         if (!p) {
                 /* no panner: just do it */
-	        AutomationControl::actually_set_value (v, group_override);
-                return;
+	        return AutomationControl::actually_set_value (v, group_override);
         }
 
         bool can_set = false;
@@ -62,8 +61,10 @@ PanControllable::actually_set_value (double v, Controllable::GroupControlDisposi
         }
 
         if (can_set) {
-	        AutomationControl::actually_set_value (v, group_override);
+	        return AutomationControl::actually_set_value (v, group_override);
         }
+
+        return false;
 }
 
 std::string
diff --git a/libs/ardour/phase_control.cc b/libs/ardour/phase_control.cc
index 9757c104b9..96d0d375b6 100644
--- a/libs/ardour/phase_control.cc
+++ b/libs/ardour/phase_control.cc
@@ -32,12 +32,12 @@ PhaseControl::PhaseControl (Session& session, std::string const & name)
 {
 }
 
-void
+bool
 PhaseControl::actually_set_value (double val, Controllable::GroupControlDisposition gcd)
 {
 	_phase_invert = boost::dynamic_bitset<> (std::numeric_limits<double>::digits, (unsigned long) val);
 
-	AutomationControl::actually_set_value (val, gcd);
+	return AutomationControl::actually_set_value (val, gcd);
 }
 
 /** @param c Audio channel index.
@@ -48,7 +48,7 @@ PhaseControl::set_phase_invert (uint32_t c, bool yn)
 {
 	if (_phase_invert[c] != yn) {
 		_phase_invert[c] = yn;
-		AutomationControl::actually_set_value (_phase_invert.to_ulong(), Controllable::NoGroup);
+		(void) AutomationControl::actually_set_value (_phase_invert.to_ulong(), Controllable::NoGroup);
 		_session.set_dirty ();
 	}
 }
@@ -58,7 +58,7 @@ PhaseControl::set_phase_invert (boost::dynamic_bitset<> p)
 {
 	if (_phase_invert != p) {
 		_phase_invert = p;
-		AutomationControl::actually_set_value (_phase_invert.to_ulong(), Controllable::NoGroup);
+		(void) AutomationControl::actually_set_value (_phase_invert.to_ulong(), Controllable::NoGroup);
 		Changed (true, Controllable::NoGroup); /* EMIT SIGNAL */
 		_session.set_dirty ();
 	}
diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index 2283f99e4b..a8348c1df3 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -2767,7 +2767,7 @@ PluginInsert::PluginControl::PluginControl (PluginInsert*                     p,
 
 /** @param val `user' value */
 
-void
+bool
 PluginInsert::PluginControl::actually_set_value (double user_val, PBD::Controllable::GroupControlDisposition group_override)
 {
 	/* FIXME: probably should be taking out some lock here.. */
@@ -2781,13 +2781,13 @@ PluginInsert::PluginControl::actually_set_value (double user_val, PBD::Controlla
 		iasp->set_parameter (_list->parameter().id(), user_val);
 	}
 
-	AutomationControl::actually_set_value (user_val, group_override);
+	return AutomationControl::actually_set_value (user_val, group_override);
 }
 
 void
 PluginInsert::PluginControl::catch_up_with_external_value (double user_val)
 {
-	AutomationControl::actually_set_value (user_val, Controllable::NoGroup);
+	(void) AutomationControl::actually_set_value (user_val, Controllable::NoGroup);
 }
 
 XMLNode&
@@ -2834,7 +2834,7 @@ PluginInsert::PluginPropertyControl::PluginPropertyControl (PluginInsert*
 	}
 }
 
-void
+bool
 PluginInsert::PluginPropertyControl::actually_set_value (double user_val, Controllable::GroupControlDisposition gcd)
 {
 	/* Old numeric set_value(), coerce to appropriate datatype if possible.
@@ -2843,7 +2843,7 @@ PluginInsert::PluginPropertyControl::actually_set_value (double user_val, Contro
 	const Variant value(_desc.datatype, user_val);
 	if (value.type() == Variant::NOTHING) {
 		error << "set_value(double) called for non-numeric property" << endmsg;
-		return;
+		return false;
 	}
 
 	for (Plugins::iterator i = _plugin->_plugins.begin(); i != _plugin->_plugins.end(); ++i) {
@@ -2852,7 +2852,7 @@ PluginInsert::PluginPropertyControl::actually_set_value (double user_val, Contro
 
 	_value = value;
 
-	AutomationControl::actually_set_value (user_val, gcd);
+	return AutomationControl::actually_set_value (user_val, gcd);
 }
 
 XMLNode&
diff --git a/libs/ardour/record_enable_control.cc b/libs/ardour/record_enable_control.cc
index f3512c3204..c83c0d186d 100644
--- a/libs/ardour/record_enable_control.cc
+++ b/libs/ardour/record_enable_control.cc
@@ -45,15 +45,15 @@ RecordEnableControl::set_value (double val, Controllable::GroupControlDispositio
 	SlavableAutomationControl::set_value (val, gcd);
 }
 
-void
+bool
 RecordEnableControl::actually_set_value (double val, Controllable::GroupControlDisposition gcd)
 {
 	if (val && !_recordable.can_be_record_enabled()) {
 		std::cerr << "rec-enable not allowed\n";
-		return;
+		return false;
 	}
 
-	SlavableAutomationControl::actually_set_value (val, gcd);
+	return SlavableAutomationControl::actually_set_value (val, gcd);
 }
 
 void
diff --git a/libs/ardour/record_safe_control.cc b/libs/ardour/record_safe_control.cc
index f3036e04ea..d9c698cbdb 100644
--- a/libs/ardour/record_safe_control.cc
+++ b/libs/ardour/record_safe_control.cc
@@ -36,14 +36,14 @@ RecordSafeControl::RecordSafeControl (Session& session, std::string const & name
 	set_flags (Controllable::Flag (flags() | Controllable::RealTime));
 }
 
-void
+bool
 RecordSafeControl::actually_set_value (double val, Controllable::GroupControlDisposition gcd)
 {
 	if (val && !_recordable.can_be_record_safe()) {
 		std::cerr << "rec-enable not allowed\n";
-		return;
+		return false;
 	}
 
-	SlavableAutomationControl::actually_set_value (val, gcd);
+	return SlavableAutomationControl::actually_set_value (val, gcd);
 }
 
diff --git a/libs/ardour/slavable_automation_control.cc b/libs/ardour/slavable_automation_control.cc
index a80598439d..2f67946705 100644
--- a/libs/ardour/slavable_automation_control.cc
+++ b/libs/ardour/slavable_automation_control.cc
@@ -96,7 +96,7 @@ SlavableAutomationControl::get_value() const
 	}
 }
 
-void
+bool
 SlavableAutomationControl::actually_set_value (double val, Controllable::GroupControlDisposition group_override)
 {
 	val = std::max (std::min (val, (double)_desc.upper), (double)_desc.lower);
@@ -112,9 +112,12 @@ SlavableAutomationControl::actually_set_value (double val, Controllable::GroupCo
 	/* this sets the Evoral::Control::_user_value for us, which will
 	   be retrieved by AutomationControl::get_value ()
 	*/
-	AutomationControl::actually_set_value (val, group_override);
+	if (AutomationControl::actually_set_value (val, group_override)) {
+		_session.set_dirty ();
+		return true;
+	}
 
-	_session.set_dirty ();
+	return false;
 }
 
 void
diff --git a/libs/ardour/solo_control.cc b/libs/ardour/solo_control.cc
index 087e5d04ab..ca41ee7aac 100644
--- a/libs/ardour/solo_control.cc
+++ b/libs/ardour/solo_control.cc
@@ -157,11 +157,11 @@ SoloControl::mod_solo_by_others_upstream (int32_t delta)
 	Changed (false, Controllable::NoGroup); /* EMIT SIGNAL */
 }
 
-void
+bool
 SoloControl::actually_set_value (double val, PBD::Controllable::GroupControlDisposition group_override)
 {
 	if (_soloable.is_safe() || !_soloable.can_solo()) {
-		return;
+		return false;
 	}
 
 	set_self_solo (val == 1.0);
@@ -170,7 +170,7 @@ SoloControl::actually_set_value (double val, PBD::Controllable::GroupControlDisp
 	   be retrieved by AutomationControl::get_value (), and emits Changed
 	*/
 
-	SlavableAutomationControl::actually_set_value (val, group_override);
+	return SlavableAutomationControl::actually_set_value (val, group_override);
 }
 
 double
diff --git a/libs/ardour/solo_isolate_control.cc b/libs/ardour/solo_isolate_control.cc
index 7964f7eb66..ebd046fba6 100644
--- a/libs/ardour/solo_isolate_control.cc
+++ b/libs/ardour/solo_isolate_control.cc
@@ -88,11 +88,11 @@ SoloIsolateControl::mod_solo_isolated_by_upstream (int32_t delta)
 	}
 }
 
-void
+bool
 SoloIsolateControl::actually_set_value (double val, PBD::Controllable::GroupControlDisposition gcd)
 {
 	if (!_soloable.can_solo()) {
-		return;
+		return false;
 	}
 
 	set_solo_isolated (val, gcd);
@@ -101,8 +101,12 @@ SoloIsolateControl::actually_set_value (double val, PBD::Controllable::GroupCont
 	   be retrieved by AutomationControl::get_value (), and emits Changed
 	*/
 
-	AutomationControl::actually_set_value (val, gcd);
-	_session.set_dirty ();
+	if (AutomationControl::actually_set_value (val, gcd)) {
+		_session.set_dirty ();
+		return true;
+	}
+
+	return false;
 }
 
 void
diff --git a/libs/ardour/solo_safe_control.cc b/libs/ardour/solo_safe_control.cc
index 01d56ddf58..7e8de603a7 100644
--- a/libs/ardour/solo_safe_control.cc
+++ b/libs/ardour/solo_safe_control.cc
@@ -36,7 +36,7 @@ SoloSafeControl::SoloSafeControl (Session& session, std::string const & name)
 	_list->set_interpolation(Evoral::ControlList::Discrete);
 }
 
-void
+bool
 SoloSafeControl::actually_set_value (double val, PBD::Controllable::GroupControlDisposition gcd)
 {
 	_solo_safe = (val ? true : false);
@@ -45,8 +45,12 @@ SoloSafeControl::actually_set_value (double val, PBD::Controllable::GroupControl
 	   be retrieved by AutomationControl::get_value (), and emits Changed
 	*/
 
-	AutomationControl::actually_set_value (val, gcd);
-	_session.set_dirty ();
+	if (AutomationControl::actually_set_value (val, gcd)) {
+	    _session.set_dirty ();
+	    return true;
+	}
+
+	return false;
 }
 
 double