Fix volume controls handling mouse wheel at a higher level than anything else game-wide.

osu.Game/GameModes/Menu/ButtonSystem.cs

@@ -133,7 +133,7 @@ namespace osu.Game.GameModes.Menu
                     return true;
             }
 
-            return true;
+            return false;
         }
 
         private void onPlay()

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

@@ -1,53 +1,52 @@
-using osu.Framework;
+using System;
+using osu.Framework;
 using osu.Framework.Configuration;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Input;
+using osu.Framework.Threading;
 using OpenTK;
-using osu.Framework.Graphics.Primitives;
 
-namespace osu.Game
+namespace osu.Game.Graphics.UserInterface.Volume
 {
-    internal class VolumeControl : Container
+    internal class VolumeControl : OverlayContainer
     {
-        private FlowContainer volumeMetersContainer;
-        private VolumeMeter volumeMeterMaster;
         public BindableDouble VolumeGlobal { get; set; }
         public BindableDouble VolumeSample { get; set; }
         public BindableDouble VolumeTrack { get; set; }
 
+        private VolumeMeter volumeMeterMaster;
+
         public override bool Contains(Vector2 screenSpacePos) => true;
 
-        private void volumeChanged(object sender, System.EventArgs e)
+        private void volumeChanged(object sender, EventArgs e)
         {
-            appear();
+            Show();
-
+            schedulePopOut();
-            Anchor = Anchor.BottomRight;
-            Origin = Anchor.BottomRight;
         }
 
         public VolumeControl()
         {
             AutoSizeAxes = Axes.Both;
+            Anchor = Anchor.BottomRight;
+            Origin = Anchor.BottomRight;
         }
 
         public override void Load(BaseGame game)
         {
-            base.Load(game);
             VolumeGlobal.ValueChanged += volumeChanged;
             VolumeSample.ValueChanged += volumeChanged;
             VolumeTrack.ValueChanged += volumeChanged;
 
             Children = new Drawable[]
             {
-                volumeMetersContainer = new FlowContainer
+                new FlowContainer
                 {
                     AutoSizeAxes = Axes.Both,
                     Anchor = Anchor.BottomRight,
                     Origin = Anchor.BottomRight,
                     Position = new Vector2(10, 30),
                     Spacing = new Vector2(15,0),
-                    Alpha = 0,
                     Children = new Drawable[]
                     {
                         volumeMeterMaster = new VolumeMeter("Master", VolumeGlobal),
@@ -56,6 +55,8 @@ namespace osu.Game
                     }
                 }
             };
+
+            base.Load(game);
         }
 
         protected override void Dispose(bool isDisposing)
@@ -68,22 +69,42 @@ namespace osu.Game
 
         protected override bool OnWheelDown(InputState state)
         {
+            if (!IsVisible)
+                return false;
+
             volumeMeterMaster.TriggerWheelDown(state);
             return true;
         }
 
         protected override bool OnWheelUp(InputState state)
         {
+            if (!IsVisible)
+                return false;
+
             volumeMeterMaster.TriggerWheelUp(state);
             return true;
         }
 
-        private void appear()
+        ScheduledDelegate popOutDelegate;
+
+        protected override void PopIn()
         {
-            volumeMetersContainer.ClearTransformations();
+            ClearTransformations();
-            volumeMetersContainer.FadeIn(100);
+            FadeIn(100);
-            volumeMetersContainer.Delay(1000);
+
-            volumeMetersContainer.FadeOut(100);
+            schedulePopOut();
+        }
+
+        protected override void PopOut()
+        {
+            FadeOut(100);
+        }
+
+        private void schedulePopOut()
+        {
+            popOutDelegate?.Cancel();
+            Delay(1000);
+            popOutDelegate = Schedule(Hide);
         }
     }
 }

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

@@ -0,0 +1,42 @@
+//Copyright (c) 2007-2016 ppy Pty Ltd <contact@ppy.sh>.
+//Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Input;
+using OpenTK.Input;
+using OpenTK;
+
+namespace osu.Game.Graphics.UserInterface.Volume
+{
+    class VolumeControlReceptor : Container
+    {
+        public Action ActivateRequested;
+
+        protected override bool OnWheelDown(InputState state)
+        {
+            ActivateRequested?.Invoke();
+            return true;
+        }
+
+        protected override bool OnWheelUp(InputState state)
+        {
+            ActivateRequested?.Invoke();
+            return true;
+        }
+
+        protected override bool OnKeyDown(InputState state, KeyDownEventArgs args)
+        {
+            switch (args.Key)
+            {
+                case Key.Up:
+                case Key.Down:
+                    ActivateRequested?.Invoke();
+                    return true;
+            }
+
+            return base.OnKeyDown(state, args);
+        }
+    }
+}

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

@@ -1,4 +1,5 @@
-using osu.Framework.Configuration;
+using osu.Framework;
+using osu.Framework.Configuration;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Sprites;
@@ -6,9 +7,8 @@ using osu.Framework.Graphics.Transformations;
 using osu.Framework.Input;
 using OpenTK;
 using OpenTK.Graphics;
-using osu.Framework;
 
-namespace osu.Game
+namespace osu.Game.Graphics.UserInterface.Volume
 {
     internal class VolumeMeter : Container
     {

osu.Game/OsuGame.cs

@@ -23,6 +23,7 @@ using OpenTK.Input;
 using System.IO;
 using osu.Game.Beatmaps.IO;
 using osu.Framework.Logging;
+using osu.Game.Graphics.UserInterface.Volume;
 
 namespace osu.Game
 {
@@ -40,6 +41,8 @@ namespace osu.Game
         private string[] args;
         private IpcChannel<ImportBeatmap> BeatmapIPC;
 
+        private VolumeControl volume;
+
         public Bindable<PlayMode> PlayMode;
 
         public OsuGame(string[] args)
@@ -92,6 +95,11 @@ namespace osu.Game
             Audio.VolumeTrack.Weld(Config.GetBindable<double>(OsuConfig.VolumeMusic));
 
             Add(new Drawable[] {
+                new VolumeControlReceptor
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    ActivateRequested = delegate { volume.Show(); }
+                },
                 intro = new Intro(),
                 Toolbar = new Toolbar
                 {
@@ -100,7 +108,7 @@ namespace osu.Game
                     OnPlayModeChange = delegate (PlayMode m) { PlayMode.Value = m; },
                 },
                 Chat = new ChatConsole(API),
-                new VolumeControl
+                volume = new VolumeControl
                 {
                     VolumeGlobal = Audio.Volume,
                     VolumeSample = Audio.VolumeSample,

osu.Game/osu.Game.csproj

@@ -138,6 +138,7 @@
     <Compile Include="GameModes\Play\ComboResultCounter.cs" />
     <Compile Include="Graphics\UserInterface\RollingCounter.cs" />
     <Compile Include="GameModes\Play\Taiko\TaikoComboCounter.cs" />
+    <Compile Include="Graphics\UserInterface\Volume\VolumeControlReceptor.cs" />
     <Compile Include="Input\GlobalHotkeys.cs" />
     <Compile Include="Graphics\Background\Background.cs" />
     <Compile Include="Graphics\Containers\ParallaxContainer.cs" />
@@ -176,14 +177,14 @@
     <Compile Include="Overlays\ToolbarModeSelector.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Users\User.cs" />
-    <Compile Include="VolumeControl.cs" />
+    <Compile Include="Graphics\UserInterface\Volume\VolumeControl.cs" />
     <Compile Include="Database\BeatmapDatabase.cs" />
     <Compile Include="Beatmaps\IO\ArchiveReader.cs" />
     <Compile Include="Beatmaps\Formats\BeatmapDecoder.cs" />
     <Compile Include="Beatmaps\Formats\OsuLegacyDecoder.cs" />
     <Compile Include="Beatmaps\IO\OszArchiveReader.cs" />
     <Compile Include="Beatmaps\Events\EventType.cs" />
-    <Compile Include="VolumeMeter.cs" />
+    <Compile Include="Graphics\UserInterface\Volume\VolumeMeter.cs" />
     <Compile Include="Database\BeatmapSetInfo.cs" />
     <Compile Include="Database\BeatmapMetadata.cs" />
     <Compile Include="Database\BeatmapInfo.cs" />