Option in settings to toggle mute/unmute when losing/gaining window focus

osu.Game/Configuration/OsuConfigManager.cs

@@ -39,6 +39,8 @@ namespace osu.Game.Configuration
             };
 
             // Audio
+            Set(OsuSetting.MuteWhenInactive, false);
+
             Set(OsuSetting.MenuVoice, true);
             Set(OsuSetting.MenuMusic, true);
 
@@ -101,6 +103,7 @@ namespace osu.Game.Configuration
         MouseDisableButtons,
         MouseDisableWheel,
         AudioOffset,
+        MuteWhenInactive,
         MenuMusic,
         MenuVoice,
         CursorRotation,

osu.Game/Graphics/UserInterface/Volume/VolumeControl.cs

@@ -91,6 +91,24 @@ namespace osu.Game.Graphics.UserInterface.Volume
             schedulePopOut();
         }
 
+        public bool IsMuted => volumeMeterMaster.IsMuted;
+
+        public void Mute()
+        {
+            if (!IsMuted)
+            {
+                volumeMeterMaster.ToogleMute();
+            }
+        }
+
+        public void Unmute()
+        {
+            if (IsMuted)
+            {
+                volumeMeterMaster.ToogleMute();
+            }
+        }
+
         [BackgroundDependencyLoader]
         private void load(AudioManager audio)
         {

osu.Game/OsuGame.cs

@@ -115,6 +115,8 @@ namespace osu.Game
             configRuleset = LocalConfig.GetBindable<int>(OsuSetting.Ruleset);
             Ruleset.Value = RulesetStore.GetRuleset(configRuleset.Value) ?? RulesetStore.AvailableRulesets.First();
             Ruleset.ValueChanged += r => configRuleset.Value = r.ID ?? 0;
+
+            muteWhenInactive = LocalConfig.GetBindable<bool>(OsuSetting.MuteWhenInactive);
         }
 
         private ScheduledDelegate scoreLoad;
@@ -386,6 +388,28 @@ namespace osu.Game
             return false;
         }
 
+        private Bindable<bool> muteWhenInactive = new Bindable<bool>();
+        private bool wasMuted;
+
+        protected override void OnDeactivated()
+        {
+            base.OnDeactivated();
+            if (muteWhenInactive)
+            {
+                wasMuted = volume.IsMuted;
+                volume.Mute();
+            }
+        }
+
+        protected override void OnActivated()
+        {
+            base.OnActivated();
+            if (IsLoaded && muteWhenInactive && !wasMuted)
+            {
+                volume.Unmute();
+            }
+        }
+
         public bool OnReleased(GlobalAction action) => false;
 
         private Container mainContent;

osu.Game/Overlays/Settings/Sections/Audio/VolumeSettings.cs

@@ -4,6 +4,7 @@
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Graphics;
+using osu.Game.Configuration;
 
 namespace osu.Game.Overlays.Settings.Sections.Audio
 {
@@ -12,13 +13,14 @@ namespace osu.Game.Overlays.Settings.Sections.Audio
         protected override string Header => "Volume";
 
         [BackgroundDependencyLoader]
-        private void load(AudioManager audio)
+        private void load(AudioManager audio, OsuConfigManager config)
         {
             Children = new Drawable[]
             {
                 new SettingsSlider<double> { LabelText = "Master", Bindable = audio.Volume, KeyboardStep = 0.1f },
                 new SettingsSlider<double> { LabelText = "Effect", Bindable = audio.VolumeSample, KeyboardStep = 0.1f },
                 new SettingsSlider<double> { LabelText = "Music", Bindable = audio.VolumeTrack, KeyboardStep = 0.1f },
+                new SettingsCheckbox { LabelText = "Mute osu! when inactive", Bindable = config.GetBindable<bool>(OsuSetting.MuteWhenInactive) }
             };
         }
     }