Merge branch 'master' into zero-spinner-slider

README.md

@@ -5,7 +5,7 @@
 # osu!
 
 [![Build status](https://ci.appveyor.com/api/projects/status/u2p01nx7l6og8buh?svg=true)](https://ci.appveyor.com/project/peppy/osu)
-[![GitHub release](https://img.shields.io/github/release/ppy/osu.svg)]()
+[![GitHub release](https://img.shields.io/github/release/ppy/osu.svg)](https://github.com/ppy/osu/releases/latest)
 [![CodeFactor](https://www.codefactor.io/repository/github/ppy/osu/badge)](https://www.codefactor.io/repository/github/ppy/osu)
 [![dev chat](https://discordapp.com/api/guilds/188630481301012481/widget.png?style=shield)](https://discord.gg/ppy)
 

osu.Android.props

@@ -52,6 +52,6 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="ppy.osu.Game.Resources" Version="2020.1202.0" />
-    <PackageReference Include="ppy.osu.Framework.Android" Version="2021.118.0" />
+    <PackageReference Include="ppy.osu.Framework.Android" Version="2021.128.0" />
   </ItemGroup>
 </Project>

osu.Desktop/osu.Desktop.csproj

@@ -24,16 +24,13 @@
     <ProjectReference Include="..\osu.Game.Rulesets.Taiko\osu.Game.Rulesets.Taiko.csproj" />
   </ItemGroup>
   <ItemGroup Label="Package References">
+    <PackageReference Include="Microsoft.NETCore.Targets" Version="5.0.0" />
     <PackageReference Include="System.IO.Packaging" Version="5.0.0" />
-    <PackageReference Include="ppy.squirrel.windows" Version="1.9.0.4" />
+    <PackageReference Include="ppy.squirrel.windows" Version="1.9.0.5" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="2.2.6" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="2.2.6" />
     <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" />
-    <PackageReference Include="DiscordRichPresence" Version="1.0.169" />
-    <!-- .NET 3.1 SDK seems to cause issues with a runtime specification. This will likely be resolved in .NET 5. -->
-    <PackageReference Include="System.IO.FileSystem.Primitives" Version="4.3.0" />
-    <PackageReference Include="System.Runtime.Handles" Version="4.3.0" />
-    <PackageReference Include="System.Runtime.InteropServices" Version="4.3.0" />
+    <PackageReference Include="DiscordRichPresence" Version="1.0.175" />
   </ItemGroup>
   <ItemGroup Label="Resources">
     <EmbeddedResource Include="lazer.ico" />

osu.Game.Rulesets.Catch/Replays/CatchAutoGenerator.cs

@@ -45,6 +45,11 @@ namespace osu.Game.Rulesets.Catch.Replays
                 float positionChange = Math.Abs(lastPosition - h.EffectiveX);
                 double timeAvailable = h.StartTime - lastTime;
 
+                if (timeAvailable < 0)
+                {
+                    return;
+                }
+
                 // So we can either make it there without a dash or not.
                 // If positionChange is 0, we don't need to move, so speedRequired should also be 0 (could be NaN if timeAvailable is 0 too)
                 // The case where positionChange > 0 and timeAvailable == 0 results in PositiveInfinity which provides expected beheaviour.

osu.Game.Rulesets.Catch/Skinning/Default/BorderPiece.cs

@@ -29,4 +29,3 @@ namespace osu.Game.Rulesets.Catch.Skinning.Default
         }
     }
 }
-

osu.Game.Rulesets.Catch/Skinning/Default/HyperBorderPiece.cs

@@ -19,4 +19,3 @@ namespace osu.Game.Rulesets.Catch.Skinning.Default
         }
     }
 }
-

osu.Game.Rulesets.Mania.Tests/Mods/TestSceneManiaModConstantSpeed.cs

@@ -0,0 +1,31 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Testing;
+using osu.Game.Rulesets.Mania.Mods;
+using osu.Game.Rulesets.Mania.Objects.Drawables;
+using osu.Game.Rulesets.UI.Scrolling;
+using osu.Game.Rulesets.UI.Scrolling.Algorithms;
+using osu.Game.Tests.Visual;
+
+namespace osu.Game.Rulesets.Mania.Tests.Mods
+{
+    public class TestSceneManiaModConstantSpeed : ModTestScene
+    {
+        protected override Ruleset CreatePlayerRuleset() => new ManiaRuleset();
+
+        [Test]
+        public void TestConstantScroll() => CreateModTest(new ModTestData
+        {
+            Mod = new ManiaModConstantSpeed(),
+            PassCondition = () =>
+            {
+                var hitObject = Player.ChildrenOfType<DrawableManiaHitObject>().FirstOrDefault();
+                return hitObject?.Dependencies.Get<IScrollingInfo>().Algorithm is ConstantScrollAlgorithm;
+            }
+        });
+    }
+}

osu.Game.Rulesets.Mania/ManiaRuleset.cs

@@ -238,6 +238,7 @@ namespace osu.Game.Rulesets.Mania
                         new ManiaModMirror(),
                         new ManiaModDifficultyAdjust(),
                         new ManiaModInvert(),
+                        new ManiaModConstantSpeed()
                     };
 
                 case ModType.Automation:

osu.Game.Rulesets.Mania/Mods/ManiaModConstantSpeed.cs

@@ -0,0 +1,35 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Configuration;
+using osu.Game.Rulesets.Mania.Objects;
+using osu.Game.Rulesets.Mania.UI;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.UI;
+
+namespace osu.Game.Rulesets.Mania.Mods
+{
+    public class ManiaModConstantSpeed : Mod, IApplicableToDrawableRuleset<ManiaHitObject>
+    {
+        public override string Name => "Constant Speed";
+
+        public override string Acronym => "CS";
+
+        public override double ScoreMultiplier => 1;
+
+        public override string Description => "No more tricky speed changes!";
+
+        public override IconUsage? Icon => FontAwesome.Solid.Equals;
+
+        public override ModType Type => ModType.Conversion;
+
+        public override bool Ranked => false;
+
+        public void ApplyToDrawableRuleset(DrawableRuleset<ManiaHitObject> drawableRuleset)
+        {
+            var maniaRuleset = (DrawableManiaRuleset)drawableRuleset;
+            maniaRuleset.ScrollMethod = ScrollVisualisationMethod.Constant;
+        }
+    }
+}

osu.Game.Rulesets.Mania/UI/DrawableManiaRuleset.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using osu.Framework.Allocation;
@@ -11,6 +12,7 @@ using osu.Framework.Graphics;
 using osu.Framework.Input;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.ControlPoints;
+using osu.Game.Configuration;
 using osu.Game.Input.Handlers;
 using osu.Game.Replays;
 using osu.Game.Rulesets.Mania.Beatmaps;
@@ -49,6 +51,22 @@ namespace osu.Game.Rulesets.Mania.UI
 
         protected new ManiaRulesetConfigManager Config => (ManiaRulesetConfigManager)base.Config;
 
+        public ScrollVisualisationMethod ScrollMethod
+        {
+            get => scrollMethod;
+            set
+            {
+                if (IsLoaded)
+                    throw new InvalidOperationException($"Can't alter {nameof(ScrollMethod)} after ruleset is already loaded");
+
+                scrollMethod = value;
+            }
+        }
+
+        private ScrollVisualisationMethod scrollMethod = ScrollVisualisationMethod.Sequential;
+
+        protected override ScrollVisualisationMethod VisualisationMethod => scrollMethod;
+
         private readonly Bindable<ManiaScrollingDirection> configDirection = new Bindable<ManiaScrollingDirection>();
         private readonly Bindable<double> configTimeRange = new BindableDouble();
 

osu.Game.Rulesets.Osu/Objects/Drawables/DrawableSpinner.cs

@@ -243,7 +243,14 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables
             base.Update();
 
             if (HandleUserInput)
-                RotationTracker.Tracking = !Result.HasResult && (OsuActionInputManager?.PressedActions.Any(x => x == OsuAction.LeftButton || x == OsuAction.RightButton) ?? false);
+            {
+                bool isValidSpinningTime = Time.Current >= HitObject.StartTime && Time.Current <= HitObject.EndTime;
+                bool correctButtonPressed = (OsuActionInputManager?.PressedActions.Any(x => x == OsuAction.LeftButton || x == OsuAction.RightButton) ?? false);
+
+                RotationTracker.Tracking = !Result.HasResult
+                                           && correctButtonPressed
+                                           && isValidSpinningTime;
+            }
 
             if (spinningSample != null && spinnerFrequencyModulate)
                 spinningSample.Frequency.Value = spinning_sample_modulated_base_frequency + Progress;
@@ -255,6 +262,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables
 
             if (!SpmCounter.IsPresent && RotationTracker.Tracking)
                 SpmCounter.FadeIn(HitObject.TimeFadeIn);
+
             SpmCounter.SetRotation(Result.RateAdjustedRotation);
 
             updateBonusScore();

osu.Game.Rulesets.Osu/Skinning/Default/SpinnerSpmCounter.cs

@@ -4,16 +4,21 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Utils;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Sprites;
+using osu.Game.Rulesets.Objects.Drawables;
 
 namespace osu.Game.Rulesets.Osu.Skinning.Default
 {
     public class SpinnerSpmCounter : Container
     {
+        [Resolved]
+        private DrawableHitObject drawableSpinner { get; set; }
+
         private readonly OsuSpriteText spmText;
 
         public SpinnerSpmCounter()
@@ -38,6 +43,12 @@ namespace osu.Game.Rulesets.Osu.Skinning.Default
             };
         }
 
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+            drawableSpinner.HitObjectApplied += resetState;
+        }
+
         private double spm;
 
         public double SpinsPerMinute
@@ -82,5 +93,19 @@ namespace osu.Game.Rulesets.Osu.Skinning.Default
 
             records.Enqueue(new RotationRecord { Rotation = currentRotation, Time = Time.Current });
         }
+
+        private void resetState(DrawableHitObject hitObject)
+        {
+            SpinsPerMinute = 0;
+            records.Clear();
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+
+            if (drawableSpinner != null)
+                drawableSpinner.HitObjectApplied -= resetState;
+        }
     }
 }

osu.Game.Rulesets.Taiko/Mods/TaikoModDifficultyAdjust.cs

@@ -1,11 +1,45 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Linq;
+using osu.Framework.Bindables;
+using osu.Game.Beatmaps;
+using osu.Game.Configuration;
 using osu.Game.Rulesets.Mods;
 
 namespace osu.Game.Rulesets.Taiko.Mods
 {
     public class TaikoModDifficultyAdjust : ModDifficultyAdjust
     {
+        [SettingSource("Scroll Speed", "Adjust a beatmap's set scroll speed", LAST_SETTING_ORDER + 1)]
+        public BindableNumber<float> ScrollSpeed { get; } = new BindableFloat
+        {
+            Precision = 0.05f,
+            MinValue = 0.25f,
+            MaxValue = 4,
+            Default = 1,
+            Value = 1,
+        };
+
+        public override string SettingDescription
+        {
+            get
+            {
+                string scrollSpeed = ScrollSpeed.IsDefault ? string.Empty : $"Scroll x{ScrollSpeed.Value:N1}";
+
+                return string.Join(", ", new[]
+                {
+                    base.SettingDescription,
+                    scrollSpeed
+                }.Where(s => !string.IsNullOrEmpty(s)));
+            }
+        }
+
+        protected override void ApplySettings(BeatmapDifficulty difficulty)
+        {
+            base.ApplySettings(difficulty);
+
+            ApplySetting(ScrollSpeed, scroll => difficulty.SliderMultiplier *= scroll);
+        }
     }
 }

osu.Game.Rulesets.Taiko/Mods/TaikoModEasy.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Mods;
 
 namespace osu.Game.Rulesets.Taiko.Mods
@@ -8,5 +9,16 @@ namespace osu.Game.Rulesets.Taiko.Mods
     public class TaikoModEasy : ModEasy
     {
         public override string Description => @"Beats move slower, and less accuracy required!";
+
+        /// <summary>
+        /// Multiplier factor added to the scrolling speed.
+        /// </summary>
+        private const double slider_multiplier = 0.8;
+
+        public override void ApplyToDifficulty(BeatmapDifficulty difficulty)
+        {
+            base.ApplyToDifficulty(difficulty);
+            difficulty.SliderMultiplier *= slider_multiplier;
+        }
     }
 }

osu.Game.Rulesets.Taiko/Mods/TaikoModHardRock.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Mods;
 
 namespace osu.Game.Rulesets.Taiko.Mods
@@ -9,5 +10,21 @@ namespace osu.Game.Rulesets.Taiko.Mods
     {
         public override double ScoreMultiplier => 1.06;
         public override bool Ranked => true;
+
+        /// <summary>
+        /// Multiplier factor added to the scrolling speed.
+        /// </summary>
+        /// <remarks>
+        /// This factor is made up of two parts: the base part (1.4) and the aspect ratio adjustment (4/3).
+        /// Stable applies the latter by dividing the width of the user's display by the width of a display with the same height, but 4:3 aspect ratio.
+        /// TODO: Revisit if taiko playfield ever changes away from a hard-coded 16:9 (see https://github.com/ppy/osu/issues/5685).
+        /// </remarks>
+        private const double slider_multiplier = 1.4 * 4 / 3;
+
+        public override void ApplyToDifficulty(BeatmapDifficulty difficulty)
+        {
+            base.ApplyToDifficulty(difficulty);
+            difficulty.SliderMultiplier *= slider_multiplier;
+        }
     }
 }

osu.Game.Tests.Android/osu.Game.Tests.Android.csproj

@@ -69,5 +69,9 @@
       <Name>osu.Game</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup Label="Package References">
+    <PackageReference Include="DeepEqual" Version="2.0.0" />
+    <PackageReference Include="Moq" Version="4.16.0" />
+  </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\Android\Xamarin.Android.CSharp.targets" />
 </Project>

osu.Game.Tests.iOS/osu.Game.Tests.iOS.csproj

@@ -45,6 +45,7 @@
   </ItemGroup>
   <ItemGroup Label="Package References">
     <PackageReference Include="DeepEqual" Version="2.0.0" />
+    <PackageReference Include="Moq" Version="4.16.0" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\iOS\Xamarin.iOS.CSharp.targets" />
 </Project>

osu.Game.Tests/Beatmaps/Formats/LegacyStoryboardDecoderTest.cs

@@ -129,5 +129,25 @@ namespace osu.Game.Tests.Beatmaps.Formats
                 Assert.AreEqual(3456, ((StoryboardSprite)background.Elements.Single()).InitialPosition.X);
             }
         }
+
+        [Test]
+        public void TestDecodeOutOfRangeLoopAnimationType()
+        {
+            var decoder = new LegacyStoryboardDecoder();
+
+            using (var resStream = TestResources.OpenResource("animation-types.osb"))
+            using (var stream = new LineBufferedReader(resStream))
+            {
+                var storyboard = decoder.Decode(stream);
+
+                StoryboardLayer foreground = storyboard.Layers.Single(l => l.Depth == 0);
+                Assert.AreEqual(AnimationLoopType.LoopForever, ((StoryboardAnimation)foreground.Elements[0]).LoopType);
+                Assert.AreEqual(AnimationLoopType.LoopOnce, ((StoryboardAnimation)foreground.Elements[1]).LoopType);
+                Assert.AreEqual(AnimationLoopType.LoopForever, ((StoryboardAnimation)foreground.Elements[2]).LoopType);
+                Assert.AreEqual(AnimationLoopType.LoopOnce, ((StoryboardAnimation)foreground.Elements[3]).LoopType);
+                Assert.AreEqual(AnimationLoopType.LoopForever, ((StoryboardAnimation)foreground.Elements[4]).LoopType);
+                Assert.AreEqual(AnimationLoopType.LoopForever, ((StoryboardAnimation)foreground.Elements[5]).LoopType);
+            }
+        }
     }
 }

osu.Game.Tests/Mods/ModUtilsTest.cs

@@ -0,0 +1,160 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Linq;
+using Moq;
+using NUnit.Framework;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Osu.Mods;
+using osu.Game.Utils;
+
+namespace osu.Game.Tests.Mods
+{
+    [TestFixture]
+    public class ModUtilsTest
+    {
+        [Test]
+        public void TestModIsCompatibleByItself()
+        {
+            var mod = new Mock<CustomMod1>();
+            Assert.That(ModUtils.CheckCompatibleSet(new[] { mod.Object }));
+        }
+
+        [Test]
+        public void TestIncompatibleThroughTopLevel()
+        {
+            var mod1 = new Mock<CustomMod1>();
+            var mod2 = new Mock<CustomMod2>();
+
+            mod1.Setup(m => m.IncompatibleMods).Returns(new[] { mod2.Object.GetType() });
+
+            // Test both orderings.
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod1.Object, mod2.Object }), Is.False);
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod2.Object, mod1.Object }), Is.False);
+        }
+
+        [Test]
+        public void TestMultiModIncompatibleWithTopLevel()
+        {
+            var mod1 = new Mock<CustomMod1>();
+
+            // The nested mod.
+            var mod2 = new Mock<CustomMod2>();
+            mod2.Setup(m => m.IncompatibleMods).Returns(new[] { mod1.Object.GetType() });
+
+            var multiMod = new MultiMod(new MultiMod(mod2.Object));
+
+            // Test both orderings.
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { multiMod, mod1.Object }), Is.False);
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod1.Object, multiMod }), Is.False);
+        }
+
+        [Test]
+        public void TestTopLevelIncompatibleWithMultiMod()
+        {
+            // The nested mod.
+            var mod1 = new Mock<CustomMod1>();
+            var multiMod = new MultiMod(new MultiMod(mod1.Object));
+
+            var mod2 = new Mock<CustomMod2>();
+            mod2.Setup(m => m.IncompatibleMods).Returns(new[] { typeof(CustomMod1) });
+
+            // Test both orderings.
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { multiMod, mod2.Object }), Is.False);
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod2.Object, multiMod }), Is.False);
+        }
+
+        [Test]
+        public void TestCompatibleMods()
+        {
+            var mod1 = new Mock<CustomMod1>();
+            var mod2 = new Mock<CustomMod2>();
+
+            // Test both orderings.
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod1.Object, mod2.Object }), Is.True);
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod2.Object, mod1.Object }), Is.True);
+        }
+
+        [Test]
+        public void TestIncompatibleThroughBaseType()
+        {
+            var mod1 = new Mock<CustomMod1>();
+            var mod2 = new Mock<CustomMod2>();
+            mod2.Setup(m => m.IncompatibleMods).Returns(new[] { typeof(Mod) });
+
+            // Test both orderings.
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod1.Object, mod2.Object }), Is.False);
+            Assert.That(ModUtils.CheckCompatibleSet(new Mod[] { mod2.Object, mod1.Object }), Is.False);
+        }
+
+        [Test]
+        public void TestAllowedThroughMostDerivedType()
+        {
+            var mod = new Mock<CustomMod1>();
+            Assert.That(ModUtils.CheckAllowed(new[] { mod.Object }, new[] { mod.Object.GetType() }));
+        }
+
+        [Test]
+        public void TestNotAllowedThroughBaseType()
+        {
+            var mod = new Mock<CustomMod1>();
+            Assert.That(ModUtils.CheckAllowed(new[] { mod.Object }, new[] { typeof(Mod) }), Is.False);
+        }
+
+        private static readonly object[] invalid_mod_test_scenarios =
+        {
+            // incompatible pair.
+            new object[]
+            {
+                new Mod[] { new OsuModDoubleTime(), new OsuModHalfTime() },
+                new[] { typeof(OsuModDoubleTime), typeof(OsuModHalfTime) }
+            },
+            // incompatible pair with derived class.
+            new object[]
+            {
+                new Mod[] { new OsuModNightcore(), new OsuModHalfTime() },
+                new[] { typeof(OsuModNightcore), typeof(OsuModHalfTime) }
+            },
+            // system mod.
+            new object[]
+            {
+                new Mod[] { new OsuModDoubleTime(), new OsuModTouchDevice() },
+                new[] { typeof(OsuModTouchDevice) }
+            },
+            // multi mod.
+            new object[]
+            {
+                new Mod[] { new MultiMod(new OsuModHalfTime()), new OsuModHalfTime() },
+                new[] { typeof(MultiMod) }
+            },
+            // valid pair.
+            new object[]
+            {
+                new Mod[] { new OsuModDoubleTime(), new OsuModHardRock() },
+                null
+            }
+        };
+
+        [TestCaseSource(nameof(invalid_mod_test_scenarios))]
+        public void TestInvalidModScenarios(Mod[] inputMods, Type[] expectedInvalid)
+        {
+            bool isValid = ModUtils.CheckValidForGameplay(inputMods, out var invalid);
+
+            Assert.That(isValid, Is.EqualTo(expectedInvalid == null));
+
+            if (isValid)
+                Assert.IsNull(invalid);
+            else
+                Assert.That(invalid?.Select(t => t.GetType()), Is.EquivalentTo(expectedInvalid));
+        }
+
+        public abstract class CustomMod1 : Mod
+        {
+        }
+
+        public abstract class CustomMod2 : Mod
+        {
+        }
+    }
+}

osu.Game.Tests/NonVisual/OngoingOperationTrackerTest.cs

@@ -0,0 +1,106 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Screens;
+using osu.Framework.Testing;
+using osu.Game.Screens;
+using osu.Game.Screens.OnlinePlay;
+using osu.Game.Tests.Visual;
+
+namespace osu.Game.Tests.NonVisual
+{
+    [HeadlessTest]
+    public class OngoingOperationTrackerTest : OsuTestScene
+    {
+        private OngoingOperationTracker tracker;
+        private IBindable<bool> operationInProgress;
+
+        [SetUpSteps]
+        public void SetUp()
+        {
+            AddStep("create tracker", () => Child = tracker = new OngoingOperationTracker());
+            AddStep("bind to operation status", () => operationInProgress = tracker.InProgress.GetBoundCopy());
+        }
+
+        [Test]
+        public void TestOperationTracking()
+        {
+            IDisposable firstOperation = null;
+            IDisposable secondOperation = null;
+
+            AddStep("begin first operation", () => firstOperation = tracker.BeginOperation());
+            AddAssert("first operation in progress", () => operationInProgress.Value);
+
+            AddStep("cannot start another operation",
+                () => Assert.Throws<InvalidOperationException>(() => tracker.BeginOperation()));
+
+            AddStep("end first operation", () => firstOperation.Dispose());
+            AddAssert("first operation is ended", () => !operationInProgress.Value);
+
+            AddStep("start second operation", () => secondOperation = tracker.BeginOperation());
+            AddAssert("second operation in progress", () => operationInProgress.Value);
+
+            AddStep("dispose first operation again", () => firstOperation.Dispose());
+            AddAssert("second operation still in progress", () => operationInProgress.Value);
+
+            AddStep("dispose second operation", () => secondOperation.Dispose());
+            AddAssert("second operation is ended", () => !operationInProgress.Value);
+        }
+
+        [Test]
+        public void TestOperationDisposalAfterTracker()
+        {
+            IDisposable operation = null;
+
+            AddStep("begin operation", () => operation = tracker.BeginOperation());
+            AddStep("dispose tracker", () => tracker.Expire());
+            AddStep("end operation", () => operation.Dispose());
+            AddAssert("operation is ended", () => !operationInProgress.Value);
+        }
+
+        [Test]
+        public void TestOperationDisposalAfterScreenExit()
+        {
+            TestScreenWithTracker screen = null;
+            OsuScreenStack stack;
+            IDisposable operation = null;
+
+            AddStep("create screen with tracker", () =>
+            {
+                Child = stack = new OsuScreenStack
+                {
+                    RelativeSizeAxes = Axes.Both
+                };
+
+                stack.Push(screen = new TestScreenWithTracker());
+            });
+            AddUntilStep("wait for loaded", () => screen.IsLoaded);
+
+            AddStep("begin operation", () => operation = screen.OngoingOperationTracker.BeginOperation());
+            AddAssert("operation in progress", () => screen.OngoingOperationTracker.InProgress.Value);
+
+            AddStep("dispose after screen exit", () =>
+            {
+                screen.Exit();
+                operation.Dispose();
+            });
+            AddAssert("operation ended", () => !screen.OngoingOperationTracker.InProgress.Value);
+        }
+
+        private class TestScreenWithTracker : OsuScreen
+        {
+            public OngoingOperationTracker OngoingOperationTracker { get; private set; }
+
+            [BackgroundDependencyLoader]
+            private void load()
+            {
+                InternalChild = OngoingOperationTracker = new OngoingOperationTracker();
+            }
+        }
+    }
+}

osu.Game.Tests/Online/TestAPIModJsonSerialization.cs

@@ -16,7 +16,7 @@ using osu.Game.Rulesets.UI;
 namespace osu.Game.Tests.Online
 {
     [TestFixture]
-    public class TestAPIModSerialization
+    public class TestAPIModJsonSerialization
     {
         [Test]
         public void TestAcronymIsPreserved()

osu.Game.Tests/Online/TestAPIModMessagePackSerialization.cs

@@ -0,0 +1,139 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using MessagePack;
+using NUnit.Framework;
+using osu.Framework.Bindables;
+using osu.Game.Beatmaps;
+using osu.Game.Configuration;
+using osu.Game.Online.API;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Difficulty;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.UI;
+
+namespace osu.Game.Tests.Online
+{
+    [TestFixture]
+    public class TestAPIModMessagePackSerialization
+    {
+        [Test]
+        public void TestAcronymIsPreserved()
+        {
+            var apiMod = new APIMod(new TestMod());
+
+            var deserialized = MessagePackSerializer.Deserialize<APIMod>(MessagePackSerializer.Serialize(apiMod));
+
+            Assert.That(deserialized.Acronym, Is.EqualTo(apiMod.Acronym));
+        }
+
+        [Test]
+        public void TestRawSettingIsPreserved()
+        {
+            var apiMod = new APIMod(new TestMod { TestSetting = { Value = 2 } });
+
+            var deserialized = MessagePackSerializer.Deserialize<APIMod>(MessagePackSerializer.Serialize(apiMod));
+
+            Assert.That(deserialized.Settings, Contains.Key("test_setting").With.ContainValue(2.0));
+        }
+
+        [Test]
+        public void TestConvertedModHasCorrectSetting()
+        {
+            var apiMod = new APIMod(new TestMod { TestSetting = { Value = 2 } });
+
+            var deserialized = MessagePackSerializer.Deserialize<APIMod>(MessagePackSerializer.Serialize(apiMod));
+            var converted = (TestMod)deserialized.ToMod(new TestRuleset());
+
+            Assert.That(converted.TestSetting.Value, Is.EqualTo(2));
+        }
+
+        [Test]
+        public void TestDeserialiseTimeRampMod()
+        {
+            // Create the mod with values different from default.
+            var apiMod = new APIMod(new TestModTimeRamp
+            {
+                AdjustPitch = { Value = false },
+                InitialRate = { Value = 1.25 },
+                FinalRate = { Value = 0.25 }
+            });
+
+            var deserialised = MessagePackSerializer.Deserialize<APIMod>(MessagePackSerializer.Serialize(apiMod));
+            var converted = (TestModTimeRamp)deserialised.ToMod(new TestRuleset());
+
+            Assert.That(converted.AdjustPitch.Value, Is.EqualTo(false));
+            Assert.That(converted.InitialRate.Value, Is.EqualTo(1.25));
+            Assert.That(converted.FinalRate.Value, Is.EqualTo(0.25));
+        }
+
+        private class TestRuleset : Ruleset
+        {
+            public override IEnumerable<Mod> GetModsFor(ModType type) => new Mod[]
+            {
+                new TestMod(),
+                new TestModTimeRamp(),
+            };
+
+            public override DrawableRuleset CreateDrawableRulesetWith(IBeatmap beatmap, IReadOnlyList<Mod> mods = null) => throw new System.NotImplementedException();
+
+            public override IBeatmapConverter CreateBeatmapConverter(IBeatmap beatmap) => throw new System.NotImplementedException();
+
+            public override DifficultyCalculator CreateDifficultyCalculator(WorkingBeatmap beatmap) => throw new System.NotImplementedException();
+
+            public override string Description { get; } = string.Empty;
+            public override string ShortName { get; } = string.Empty;
+        }
+
+        private class TestMod : Mod
+        {
+            public override string Name => "Test Mod";
+            public override string Acronym => "TM";
+            public override double ScoreMultiplier => 1;
+
+            [SettingSource("Test")]
+            public BindableNumber<double> TestSetting { get; } = new BindableDouble
+            {
+                MinValue = 0,
+                MaxValue = 10,
+                Default = 5,
+                Precision = 0.01,
+            };
+        }
+
+        private class TestModTimeRamp : ModTimeRamp
+        {
+            public override string Name => "Test Mod";
+            public override string Acronym => "TMTR";
+            public override double ScoreMultiplier => 1;
+
+            [SettingSource("Initial rate", "The starting speed of the track")]
+            public override BindableNumber<double> InitialRate { get; } = new BindableDouble
+            {
+                MinValue = 1,
+                MaxValue = 2,
+                Default = 1.5,
+                Value = 1.5,
+                Precision = 0.01,
+            };
+
+            [SettingSource("Final rate", "The speed increase to ramp towards")]
+            public override BindableNumber<double> FinalRate { get; } = new BindableDouble
+            {
+                MinValue = 0,
+                MaxValue = 1,
+                Default = 0.5,
+                Value = 0.5,
+                Precision = 0.01,
+            };
+
+            [SettingSource("Adjust pitch", "Should pitch be adjusted with speed")]
+            public override BindableBool AdjustPitch { get; } = new BindableBool
+            {
+                Default = true,
+                Value = true
+            };
+        }
+    }
+}

osu.Game.Tests/Online/TestSceneOnlinePlayBeatmapAvailabilityTracker.cs

@@ -0,0 +1,188 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using JetBrains.Annotations;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Audio;
+using osu.Framework.Bindables;
+using osu.Framework.Extensions;
+using osu.Framework.Platform;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps;
+using osu.Game.Beatmaps.Formats;
+using osu.Game.Database;
+using osu.Game.IO;
+using osu.Game.IO.Archives;
+using osu.Game.Online.API;
+using osu.Game.Online.Rooms;
+using osu.Game.Rulesets;
+using osu.Game.Tests.Resources;
+using osu.Game.Tests.Visual;
+
+namespace osu.Game.Tests.Online
+{
+    [HeadlessTest]
+    public class TestSceneOnlinePlayBeatmapAvailabilityTracker : OsuTestScene
+    {
+        private RulesetStore rulesets;
+        private TestBeatmapManager beatmaps;
+
+        private string testBeatmapFile;
+        private BeatmapInfo testBeatmapInfo;
+        private BeatmapSetInfo testBeatmapSet;
+
+        private readonly Bindable<PlaylistItem> selectedItem = new Bindable<PlaylistItem>();
+        private OnlinePlayBeatmapAvailablilityTracker availablilityTracker;
+
+        [BackgroundDependencyLoader]
+        private void load(AudioManager audio, GameHost host)
+        {
+            Dependencies.Cache(rulesets = new RulesetStore(ContextFactory));
+            Dependencies.CacheAs<BeatmapManager>(beatmaps = new TestBeatmapManager(LocalStorage, ContextFactory, rulesets, API, audio, host, Beatmap.Default));
+        }
+
+        [SetUp]
+        public void SetUp() => Schedule(() =>
+        {
+            beatmaps.AllowImport = new TaskCompletionSource<bool>();
+
+            testBeatmapFile = TestResources.GetTestBeatmapForImport();
+
+            testBeatmapInfo = getTestBeatmapInfo(testBeatmapFile);
+            testBeatmapSet = testBeatmapInfo.BeatmapSet;
+
+            var existing = beatmaps.QueryBeatmapSet(s => s.OnlineBeatmapSetID == testBeatmapSet.OnlineBeatmapSetID);
+            if (existing != null)
+                beatmaps.Delete(existing);
+
+            selectedItem.Value = new PlaylistItem
+            {
+                Beatmap = { Value = testBeatmapInfo },
+                Ruleset = { Value = testBeatmapInfo.Ruleset },
+            };
+
+            Child = availablilityTracker = new OnlinePlayBeatmapAvailablilityTracker
+            {
+                SelectedItem = { BindTarget = selectedItem, }
+            };
+        });
+
+        [Test]
+        public void TestBeatmapDownloadingFlow()
+        {
+            AddAssert("ensure beatmap unavailable", () => !beatmaps.IsAvailableLocally(testBeatmapSet));
+            addAvailabilityCheckStep("state not downloaded", BeatmapAvailability.NotDownloaded);
+
+            AddStep("start downloading", () => beatmaps.Download(testBeatmapSet));
+            addAvailabilityCheckStep("state downloading 0%", () => BeatmapAvailability.Downloading(0.0f));
+
+            AddStep("set progress 40%", () => ((TestDownloadRequest)beatmaps.GetExistingDownload(testBeatmapSet)).SetProgress(0.4f));
+            addAvailabilityCheckStep("state downloading 40%", () => BeatmapAvailability.Downloading(0.4f));
+
+            AddStep("finish download", () => ((TestDownloadRequest)beatmaps.GetExistingDownload(testBeatmapSet)).TriggerSuccess(testBeatmapFile));
+            addAvailabilityCheckStep("state importing", BeatmapAvailability.Importing);
+
+            AddStep("allow importing", () => beatmaps.AllowImport.SetResult(true));
+            AddUntilStep("wait for import", () => beatmaps.CurrentImportTask?.IsCompleted == true);
+            addAvailabilityCheckStep("state locally available", BeatmapAvailability.LocallyAvailable);
+        }
+
+        [Test]
+        public void TestTrackerRespectsSoftDeleting()
+        {
+            AddStep("allow importing", () => beatmaps.AllowImport.SetResult(true));
+            AddStep("import beatmap", () => beatmaps.Import(testBeatmapFile).Wait());
+            addAvailabilityCheckStep("state locally available", BeatmapAvailability.LocallyAvailable);
+
+            AddStep("delete beatmap", () => beatmaps.Delete(beatmaps.QueryBeatmapSet(b => b.OnlineBeatmapSetID == testBeatmapSet.OnlineBeatmapSetID)));
+            addAvailabilityCheckStep("state not downloaded", BeatmapAvailability.NotDownloaded);
+
+            AddStep("undelete beatmap", () => beatmaps.Undelete(beatmaps.QueryBeatmapSet(b => b.OnlineBeatmapSetID == testBeatmapSet.OnlineBeatmapSetID)));
+            addAvailabilityCheckStep("state locally available", BeatmapAvailability.LocallyAvailable);
+        }
+
+        [Test]
+        public void TestTrackerRespectsChecksum()
+        {
+            AddStep("allow importing", () => beatmaps.AllowImport.SetResult(true));
+
+            AddStep("import altered beatmap", () =>
+            {
+                beatmaps.Import(TestResources.GetTestBeatmapForImport(true)).Wait();
+            });
+            addAvailabilityCheckStep("state still not downloaded", BeatmapAvailability.NotDownloaded);
+
+            AddStep("recreate tracker", () => Child = availablilityTracker = new OnlinePlayBeatmapAvailablilityTracker
+            {
+                SelectedItem = { BindTarget = selectedItem }
+            });
+            addAvailabilityCheckStep("state not downloaded as well", BeatmapAvailability.NotDownloaded);
+        }
+
+        private void addAvailabilityCheckStep(string description, Func<BeatmapAvailability> expected)
+        {
+            AddAssert(description, () => availablilityTracker.Availability.Value.Equals(expected.Invoke()));
+        }
+
+        private static BeatmapInfo getTestBeatmapInfo(string archiveFile)
+        {
+            BeatmapInfo info;
+
+            using (var archive = new ZipArchiveReader(File.OpenRead(archiveFile)))
+            using (var stream = archive.GetStream("Soleily - Renatus (Gamu) [Insane].osu"))
+            using (var reader = new LineBufferedReader(stream))
+            {
+                var decoder = Decoder.GetDecoder<Beatmap>(reader);
+                var beatmap = decoder.Decode(reader);
+
+                info = beatmap.BeatmapInfo;
+                info.BeatmapSet.Beatmaps = new List<BeatmapInfo> { info };
+                info.BeatmapSet.Metadata = info.Metadata;
+                info.MD5Hash = stream.ComputeMD5Hash();
+                info.Hash = stream.ComputeSHA2Hash();
+            }
+
+            return info;
+        }
+
+        private class TestBeatmapManager : BeatmapManager
+        {
+            public TaskCompletionSource<bool> AllowImport = new TaskCompletionSource<bool>();
+
+            public Task<BeatmapSetInfo> CurrentImportTask { get; private set; }
+
+            protected override ArchiveDownloadRequest<BeatmapSetInfo> CreateDownloadRequest(BeatmapSetInfo set, bool minimiseDownloadSize)
+                => new TestDownloadRequest(set);
+
+            public TestBeatmapManager(Storage storage, IDatabaseContextFactory contextFactory, RulesetStore rulesets, IAPIProvider api, [NotNull] AudioManager audioManager, GameHost host = null, WorkingBeatmap defaultBeatmap = null, bool performOnlineLookups = false)
+                : base(storage, contextFactory, rulesets, api, audioManager, host, defaultBeatmap, performOnlineLookups)
+            {
+            }
+
+            public override async Task<BeatmapSetInfo> Import(BeatmapSetInfo item, ArchiveReader archive = null, CancellationToken cancellationToken = default)
+            {
+                await AllowImport.Task;
+                return await (CurrentImportTask = base.Import(item, archive, cancellationToken));
+            }
+        }
+
+        private class TestDownloadRequest : ArchiveDownloadRequest<BeatmapSetInfo>
+        {
+            public new void SetProgress(float progress) => base.SetProgress(progress);
+            public new void TriggerSuccess(string filename) => base.TriggerSuccess(filename);
+
+            public TestDownloadRequest(BeatmapSetInfo model)
+                : base(model)
+            {
+            }
+
+            protected override string Target => null;
+        }
+    }
+}

osu.Game.Tests/Resources/animation-types.osb

@@ -0,0 +1,9 @@
+osu file format v14
+
+[Events]
+Animation,Foreground,Centre,"forever-string.png",330,240,10,108,LoopForever
+Animation,Foreground,Centre,"once-string.png",330,240,10,108,LoopOnce
+Animation,Foreground,Centre,"forever-number.png",330,240,10,108,0
+Animation,Foreground,Centre,"once-number.png",330,240,10,108,1
+Animation,Foreground,Centre,"undefined-number.png",330,240,10,108,16
+Animation,Foreground,Centre,"omitted.png",330,240,10,108

osu.Game.Tests/Rulesets/Mods/ModTimeRampTest.cs

@@ -0,0 +1,113 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using NUnit.Framework;
+using osu.Framework.Audio.Track;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Osu.Objects;
+
+namespace osu.Game.Tests.Rulesets.Mods
+{
+    [TestFixture]
+    public class ModTimeRampTest
+    {
+        private const double start_time = 1000;
+        private const double duration = 9000;
+
+        private TrackVirtual track;
+
+        [SetUp]
+        public void SetUp()
+        {
+            track = new TrackVirtual(20_000);
+        }
+
+        [TestCase(0, 1)]
+        [TestCase(start_time, 1)]
+        [TestCase(start_time + duration * ModTimeRamp.FINAL_RATE_PROGRESS / 2, 1.25)]
+        [TestCase(start_time + duration * ModTimeRamp.FINAL_RATE_PROGRESS, 1.5)]
+        [TestCase(start_time + duration, 1.5)]
+        [TestCase(15000, 1.5)]
+        public void TestModWindUp(double time, double expectedRate)
+        {
+            var beatmap = createSingleSpinnerBeatmap();
+            var mod = new ModWindUp();
+            mod.ApplyToBeatmap(beatmap);
+            mod.ApplyToTrack(track);
+
+            seekTrackAndUpdateMod(mod, time);
+
+            Assert.That(mod.SpeedChange.Value, Is.EqualTo(expectedRate));
+        }
+
+        [TestCase(0, 1)]
+        [TestCase(start_time, 1)]
+        [TestCase(start_time + duration * ModTimeRamp.FINAL_RATE_PROGRESS / 2, 0.75)]
+        [TestCase(start_time + duration * ModTimeRamp.FINAL_RATE_PROGRESS, 0.5)]
+        [TestCase(start_time + duration, 0.5)]
+        [TestCase(15000, 0.5)]
+        public void TestModWindDown(double time, double expectedRate)
+        {
+            var beatmap = createSingleSpinnerBeatmap();
+            var mod = new ModWindDown
+            {
+                FinalRate = { Value = 0.5 }
+            };
+            mod.ApplyToBeatmap(beatmap);
+            mod.ApplyToTrack(track);
+
+            seekTrackAndUpdateMod(mod, time);
+
+            Assert.That(mod.SpeedChange.Value, Is.EqualTo(expectedRate));
+        }
+
+        [TestCase(0, 1)]
+        [TestCase(start_time, 1)]
+        [TestCase(2 * start_time, 1.5)]
+        public void TestZeroDurationMap(double time, double expectedRate)
+        {
+            var beatmap = createSingleObjectBeatmap();
+            var mod = new ModWindUp();
+            mod.ApplyToBeatmap(beatmap);
+            mod.ApplyToTrack(track);
+
+            seekTrackAndUpdateMod(mod, time);
+
+            Assert.That(mod.SpeedChange.Value, Is.EqualTo(expectedRate));
+        }
+
+        private void seekTrackAndUpdateMod(ModTimeRamp mod, double time)
+        {
+            track.Seek(time);
+            // update the mod via a fake playfield to re-calculate the current rate.
+            mod.Update(null);
+        }
+
+        private static Beatmap createSingleSpinnerBeatmap()
+        {
+            return new Beatmap
+            {
+                HitObjects =
+                {
+                    new Spinner
+                    {
+                        StartTime = start_time,
+                        Duration = duration
+                    }
+                }
+            };
+        }
+
+        private static Beatmap createSingleObjectBeatmap()
+        {
+            return new Beatmap
+            {
+                HitObjects =
+                {
+                    new HitCircle { StartTime = start_time }
+                }
+            };
+        }
+    }
+}

osu.Game.Tests/Visual/Editing/TestSceneEditorSummaryTimeline.cs

@@ -5,6 +5,8 @@ using NUnit.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Game.Rulesets.Osu;
+using osu.Game.Rulesets.Osu.Beatmaps;
+using osu.Game.Screens.Edit;
 using osu.Game.Screens.Edit.Components.Timelines.Summary;
 using osuTK;
 
@@ -13,6 +15,9 @@ namespace osu.Game.Tests.Visual.Editing
     [TestFixture]
     public class TestSceneEditorSummaryTimeline : EditorClockTestScene
     {
+        [Cached(typeof(EditorBeatmap))]
+        private readonly EditorBeatmap editorBeatmap = new EditorBeatmap(new OsuBeatmap());
+
         [BackgroundDependencyLoader]
         private void load()
         {

osu.Game.Tests/Visual/Gameplay/TestScenePoolingRuleset.cs

@@ -17,10 +17,12 @@ using osu.Framework.Utils;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets;
 using osu.Game.Rulesets.Difficulty;
+using osu.Game.Rulesets.Judgements;
 using osu.Game.Rulesets.Mods;
 using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Objects.Drawables;
 using osu.Game.Rulesets.Objects.Legacy;
+using osu.Game.Rulesets.Objects.Types;
 using osu.Game.Rulesets.UI;
 using osuTK;
 using osuTK.Graphics;
@@ -129,6 +131,31 @@ namespace osu.Game.Tests.Visual.Gameplay
             AddUntilStep("no DHOs shown", () => !this.ChildrenOfType<DrawableTestHitObject>().Any());
         }
 
+        [Test]
+        public void TestApplyHitResultOnKilled()
+        {
+            ManualClock clock = null;
+            bool anyJudged = false;
+
+            void onNewResult(JudgementResult _) => anyJudged = true;
+
+            var beatmap = new Beatmap();
+            beatmap.HitObjects.Add(new TestKilledHitObject { Duration = 20 });
+
+            createTest(beatmap, 10, () => new FramedClock(clock = new ManualClock()));
+
+            AddStep("subscribe to new result", () =>
+            {
+                anyJudged = false;
+                drawableRuleset.NewResult += onNewResult;
+            });
+            AddStep("skip past object", () => clock.CurrentTime = beatmap.HitObjects[0].GetEndTime() + 1000);
+
+            AddAssert("object judged", () => anyJudged);
+
+            AddStep("clean up", () => drawableRuleset.NewResult -= onNewResult);
+        }
+
         private void createTest(IBeatmap beatmap, int poolSize, Func<IFrameBasedClock> createClock = null) => AddStep("create test", () =>
         {
             var ruleset = new TestPoolingRuleset();
@@ -192,6 +219,7 @@ namespace osu.Game.Tests.Visual.Gameplay
             private void load()
             {
                 RegisterPool<TestHitObject, DrawableTestHitObject>(poolSize);
+                RegisterPool<TestKilledHitObject, DrawableTestKilledHitObject>(poolSize);
             }
 
             protected override HitObjectLifetimeEntry CreateLifetimeEntry(HitObject hitObject) => new TestHitObjectLifetimeEntry(hitObject);
@@ -220,19 +248,30 @@ namespace osu.Game.Tests.Visual.Gameplay
 
             protected override IEnumerable<TestHitObject> ConvertHitObject(HitObject original, IBeatmap beatmap, CancellationToken cancellationToken)
             {
-                yield return new TestHitObject
+                switch (original)
                 {
-                    StartTime = original.StartTime,
-                    Duration = 250
-                };
+                    case TestKilledHitObject h:
+                        yield return h;
+
+                        break;
+
+                    default:
+                        yield return new TestHitObject
+                        {
+                            StartTime = original.StartTime,
+                            Duration = 250
+                        };
+
+                        break;
+                }
             }
         }
 
         #endregion
 
-        #region HitObject
+        #region HitObjects
 
-        private class TestHitObject : ConvertHitObject
+        private class TestHitObject : ConvertHitObject, IHasDuration
         {
             public double EndTime => StartTime + Duration;
 
@@ -287,6 +326,30 @@ namespace osu.Game.Tests.Visual.Gameplay
             }
         }
 
+        private class TestKilledHitObject : TestHitObject
+        {
+        }
+
+        private class DrawableTestKilledHitObject : DrawableHitObject<TestKilledHitObject>
+        {
+            public DrawableTestKilledHitObject()
+                : base(null)
+            {
+            }
+
+            protected override void UpdateHitStateTransforms(ArmedState state)
+            {
+                base.UpdateHitStateTransforms(state);
+                Expire();
+            }
+
+            public override void OnKilled()
+            {
+                base.OnKilled();
+                ApplyResult(r => r.Type = r.Judgement.MinResult);
+            }
+        }
+
         #endregion
     }
 }

osu.Game.Tests/Visual/Gameplay/TestSceneStoryboardSamplePlayback.cs

@@ -0,0 +1,74 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps;
+using osu.Game.Configuration;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Osu;
+using osu.Game.Storyboards;
+using osu.Game.Storyboards.Drawables;
+
+namespace osu.Game.Tests.Visual.Gameplay
+{
+    public class TestSceneStoryboardSamplePlayback : PlayerTestScene
+    {
+        private Storyboard storyboard;
+
+        [BackgroundDependencyLoader]
+        private void load(OsuConfigManager config)
+        {
+            config.Set(OsuSetting.ShowStoryboard, true);
+
+            storyboard = new Storyboard();
+            var backgroundLayer = storyboard.GetLayer("Background");
+            backgroundLayer.Add(new StoryboardSampleInfo("Intro/welcome.mp3", time: -7000, volume: 20));
+            backgroundLayer.Add(new StoryboardSampleInfo("Intro/welcome.mp3", time: -5000, volume: 20));
+            backgroundLayer.Add(new StoryboardSampleInfo("Intro/welcome.mp3", time: 0, volume: 20));
+        }
+
+        [Test]
+        public void TestStoryboardSamplesStopDuringPause()
+        {
+            checkForFirstSamplePlayback();
+
+            AddStep("player paused", () => Player.Pause());
+            AddAssert("player is currently paused", () => Player.GameplayClockContainer.IsPaused.Value);
+            AddAssert("all storyboard samples stopped immediately", () => allStoryboardSamples.All(sound => !sound.IsPlaying));
+
+            AddStep("player resume", () => Player.Resume());
+            AddUntilStep("any storyboard samples playing after resume", () => allStoryboardSamples.Any(sound => sound.IsPlaying));
+        }
+
+        [Test]
+        public void TestStoryboardSamplesStopOnSkip()
+        {
+            checkForFirstSamplePlayback();
+
+            AddStep("skip intro", () => InputManager.Key(osuTK.Input.Key.Space));
+            AddAssert("all storyboard samples stopped immediately", () => allStoryboardSamples.All(sound => !sound.IsPlaying));
+
+            AddUntilStep("any storyboard samples playing after skip", () => allStoryboardSamples.Any(sound => sound.IsPlaying));
+        }
+
+        private void checkForFirstSamplePlayback()
+        {
+            AddUntilStep("storyboard loaded", () => Player.Beatmap.Value.StoryboardLoaded);
+            AddUntilStep("any storyboard samples playing", () => allStoryboardSamples.Any(sound => sound.IsPlaying));
+        }
+
+        private IEnumerable<DrawableStoryboardSample> allStoryboardSamples => Player.ChildrenOfType<DrawableStoryboardSample>();
+
+        protected override bool AllowFail => false;
+
+        protected override Ruleset CreatePlayerRuleset() => new OsuRuleset();
+        protected override TestPlayer CreatePlayer(Ruleset ruleset) => new TestPlayer(true, false);
+
+        protected override WorkingBeatmap CreateWorkingBeatmap(IBeatmap beatmap, Storyboard storyboard = null) =>
+            new ClockBackedTestWorkingBeatmap(beatmap, storyboard ?? this.storyboard, Clock, Audio);
+    }
+}

osu.Game.Tests/Visual/Multiplayer/TestSceneDrawableRoomPlaylist.cs

@@ -11,8 +11,8 @@ using osu.Framework.Graphics.Containers;
 using osu.Framework.Platform;
 using osu.Framework.Testing;
 using osu.Game.Beatmaps;
+using osu.Game.Beatmaps.Drawables;
 using osu.Game.Graphics.Containers;
-using osu.Game.Graphics.UserInterface;
 using osu.Game.Online.Rooms;
 using osu.Game.Overlays;
 using osu.Game.Rulesets;
@@ -20,6 +20,7 @@ using osu.Game.Rulesets.Osu;
 using osu.Game.Rulesets.Osu.Mods;
 using osu.Game.Screens.OnlinePlay;
 using osu.Game.Tests.Beatmaps;
+using osu.Game.Users;
 using osuTK;
 using osuTK.Input;
 
@@ -241,7 +242,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
         }
 
         private void moveToItem(int index, Vector2? offset = null)
-            => AddStep($"move mouse to item {index}", () => InputManager.MoveMouseTo(playlist.ChildrenOfType<OsuRearrangeableListItem<PlaylistItem>>().ElementAt(index), offset));
+            => AddStep($"move mouse to item {index}", () => InputManager.MoveMouseTo(playlist.ChildrenOfType<DifficultyIcon>().ElementAt(index), offset));
 
         private void moveToDragger(int index, Vector2? offset = null) => AddStep($"move mouse to dragger {index}", () =>
         {
@@ -252,7 +253,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
         private void moveToDeleteButton(int index, Vector2? offset = null) => AddStep($"move mouse to delete button {index}", () =>
         {
             var item = playlist.ChildrenOfType<OsuRearrangeableListItem<PlaylistItem>>().ElementAt(index);
-            InputManager.MoveMouseTo(item.ChildrenOfType<IconButton>().ElementAt(0), offset);
+            InputManager.MoveMouseTo(item.ChildrenOfType<DrawableRoomPlaylistItem.PlaylistRemoveButton>().ElementAt(0), offset);
         });
 
         private void assertHandleVisibility(int index, bool visible)
@@ -260,7 +261,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
                 () => (playlist.ChildrenOfType<OsuRearrangeableListItem<PlaylistItem>.PlaylistItemHandle>().ElementAt(index).Alpha > 0) == visible);
 
         private void assertDeleteButtonVisibility(int index, bool visible)
-            => AddAssert($"delete button {index} {(visible ? "is" : "is not")} visible", () => (playlist.ChildrenOfType<IconButton>().ElementAt(2 + index * 2).Alpha > 0) == visible);
+            => AddAssert($"delete button {index} {(visible ? "is" : "is not")} visible", () => (playlist.ChildrenOfType<DrawableRoomPlaylistItem.PlaylistRemoveButton>().ElementAt(2 + index * 2).Alpha > 0) == visible);
 
         private void createPlaylist(bool allowEdit, bool allowSelection)
         {
@@ -278,7 +279,21 @@ namespace osu.Game.Tests.Visual.Multiplayer
                     playlist.Items.Add(new PlaylistItem
                     {
                         ID = i,
-                        Beatmap = { Value = new TestBeatmap(new OsuRuleset().RulesetInfo).BeatmapInfo },
+                        Beatmap =
+                        {
+                            Value = i % 2 == 1
+                                ? new TestBeatmap(new OsuRuleset().RulesetInfo).BeatmapInfo
+                                : new BeatmapInfo
+                                {
+                                    Metadata = new BeatmapMetadata
+                                    {
+                                        Artist = "Artist",
+                                        Author = new User { Username = "Creator name here" },
+                                        Title = "Long title used to check background colour",
+                                    },
+                                    BeatmapSet = new BeatmapSetInfo()
+                                }
+                        },
                         Ruleset = { Value = new OsuRuleset().RulesetInfo },
                         RequiredMods =
                         {

osu.Game.Tests/Visual/Multiplayer/TestSceneFreeModSelectOverlay.cs

@@ -0,0 +1,21 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using NUnit.Framework;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Screens.OnlinePlay;
+
+namespace osu.Game.Tests.Visual.Multiplayer
+{
+    public class TestSceneFreeModSelectOverlay : MultiplayerTestScene
+    {
+        [SetUp]
+        public new void Setup() => Schedule(() =>
+        {
+            Child = new FreeModSelectOverlay
+            {
+                State = { Value = Visibility.Visible }
+            };
+        });
+    }
+}

osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerParticipantsList.cs

@@ -8,6 +8,8 @@ using osu.Framework.Graphics.Sprites;
 using osu.Framework.Testing;
 using osu.Framework.Utils;
 using osu.Game.Online.Multiplayer;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Osu.Mods;
 using osu.Game.Screens.OnlinePlay.Multiplayer.Participants;
 using osu.Game.Users;
 using osuTK;
@@ -123,5 +125,32 @@ namespace osu.Game.Tests.Visual.Multiplayer
                 }
             });
         }
+
+        [Test]
+        public void TestUserWithMods()
+        {
+            AddStep("add user", () =>
+            {
+                Client.AddUser(new User
+                {
+                    Id = 0,
+                    Username = "User 0",
+                    CurrentModeRank = RNG.Next(1, 100000),
+                    CoverUrl = @"https://osu.ppy.sh/images/headers/profile-covers/c3.jpg",
+                });
+
+                Client.ChangeUserMods(0, new Mod[]
+                {
+                    new OsuModHardRock(),
+                    new OsuModDifficultyAdjust { ApproachRate = { Value = 1 } }
+                });
+            });
+
+            for (var i = MultiplayerUserState.Idle; i < MultiplayerUserState.Results; i++)
+            {
+                var state = i;
+                AddStep($"set state: {state}", () => Client.ChangeUserState(0, state));
+            }
+        }
     }
 }

osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerReadyButton.cs

@@ -6,6 +6,7 @@ using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
+using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Platform;
 using osu.Framework.Testing;
@@ -26,8 +27,11 @@ namespace osu.Game.Tests.Visual.Multiplayer
     public class TestSceneMultiplayerReadyButton : MultiplayerTestScene
     {
         private MultiplayerReadyButton button;
+        private OnlinePlayBeatmapAvailablilityTracker beatmapTracker;
         private BeatmapSetInfo importedSet;
 
+        private readonly Bindable<PlaylistItem> selectedItem = new Bindable<PlaylistItem>();
+
         private BeatmapManager beatmaps;
         private RulesetStore rulesets;
 
@@ -39,6 +43,13 @@ namespace osu.Game.Tests.Visual.Multiplayer
             Dependencies.Cache(rulesets = new RulesetStore(ContextFactory));
             Dependencies.Cache(beatmaps = new BeatmapManager(LocalStorage, ContextFactory, rulesets, null, audio, host, Beatmap.Default));
             beatmaps.Import(TestResources.GetTestBeatmapForImport(true)).Wait();
+
+            Add(beatmapTracker = new OnlinePlayBeatmapAvailablilityTracker
+            {
+                SelectedItem = { BindTarget = selectedItem }
+            });
+
+            Dependencies.Cache(beatmapTracker);
         }
 
         [SetUp]
@@ -46,20 +57,20 @@ namespace osu.Game.Tests.Visual.Multiplayer
         {
             importedSet = beatmaps.GetAllUsableBeatmapSetsEnumerable(IncludedDetails.All).First();
             Beatmap.Value = beatmaps.GetWorkingBeatmap(importedSet.Beatmaps.First());
+            selectedItem.Value = new PlaylistItem
+            {
+                Beatmap = { Value = Beatmap.Value.BeatmapInfo },
+                Ruleset = { Value = Beatmap.Value.BeatmapInfo.Ruleset },
+            };
 
-            Child = button = new MultiplayerReadyButton
+            if (button != null)
+                Remove(button);
+
+            Add(button = new MultiplayerReadyButton
             {
                 Anchor = Anchor.Centre,
                 Origin = Anchor.Centre,
                 Size = new Vector2(200, 50),
-                SelectedItem =
-                {
-                    Value = new PlaylistItem
-                    {
-                        Beatmap = { Value = Beatmap.Value.BeatmapInfo },
-                        Ruleset = { Value = Beatmap.Value.BeatmapInfo.Ruleset }
-                    }
-                },
                 OnReadyClick = async () =>
                 {
                     readyClickOperation = OngoingOperationTracker.BeginOperation();
@@ -73,7 +84,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
                     await Client.ToggleReady();
                     readyClickOperation.Dispose();
                 }
-            };
+            });
         });
 
         [Test]

osu.Game.Tests/Visual/Multiplayer/TestScenePlaylistsSongSelect.cs

@@ -19,11 +19,11 @@ using osu.Game.Rulesets.Mods;
 using osu.Game.Rulesets.Osu;
 using osu.Game.Rulesets.Osu.Mods;
 using osu.Game.Screens.OnlinePlay.Components;
-using osu.Game.Screens.Select;
+using osu.Game.Screens.OnlinePlay.Playlists;
 
 namespace osu.Game.Tests.Visual.Multiplayer
 {
-    public class TestSceneMatchSongSelect : RoomTestScene
+    public class TestScenePlaylistsSongSelect : RoomTestScene
     {
         [Resolved]
         private BeatmapManager beatmapManager { get; set; }
@@ -32,7 +32,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
 
         private RulesetStore rulesets;
 
-        private TestMatchSongSelect songSelect;
+        private TestPlaylistsSongSelect songSelect;
 
         [BackgroundDependencyLoader]
         private void load(GameHost host, AudioManager audio)
@@ -89,7 +89,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
                 Beatmap.SetDefault();
             });
 
-            AddStep("create song select", () => LoadScreen(songSelect = new TestMatchSongSelect()));
+            AddStep("create song select", () => LoadScreen(songSelect = new TestPlaylistsSongSelect()));
             AddUntilStep("wait for present", () => songSelect.IsCurrentScreen());
         }
 
@@ -176,7 +176,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
             AddAssert("item has rate 1.5", () => Precision.AlmostEquals(1.5, ((OsuModDoubleTime)Room.Playlist.First().RequiredMods[0]).SpeedChange.Value));
         }
 
-        private class TestMatchSongSelect : MatchSongSelect
+        private class TestPlaylistsSongSelect : PlaylistsSongSelect
         {
             public new MatchBeatmapDetailArea BeatmapDetails => (MatchBeatmapDetailArea)base.BeatmapDetails;
         }

osu.Game.Tests/Visual/Online/TestSceneBeatmapListingOverlay.cs

@@ -1,32 +1,81 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using osu.Game.Overlays;
+using System.Collections.Generic;
+using System.Linq;
 using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps;
+using osu.Game.Online.API;
+using osu.Game.Online.API.Requests;
+using osu.Game.Online.API.Requests.Responses;
+using osu.Game.Overlays;
+using osu.Game.Overlays.BeatmapListing;
+using osu.Game.Rulesets;
 
 namespace osu.Game.Tests.Visual.Online
 {
     public class TestSceneBeatmapListingOverlay : OsuTestScene
     {
-        protected override bool UseOnlineAPI => true;
+        private readonly List<APIBeatmapSet> setsForResponse = new List<APIBeatmapSet>();
 
-        private readonly BeatmapListingOverlay overlay;
+        private BeatmapListingOverlay overlay;
 
-        public TestSceneBeatmapListingOverlay()
+        [BackgroundDependencyLoader]
+        private void load()
         {
-            Add(overlay = new BeatmapListingOverlay());
+            Child = overlay = new BeatmapListingOverlay { State = { Value = Visibility.Visible } };
+
+            ((DummyAPIAccess)API).HandleRequest = req =>
+            {
+                if (req is SearchBeatmapSetsRequest searchBeatmapSetsRequest)
+                {
+                    searchBeatmapSetsRequest.TriggerSuccess(new SearchBeatmapSetsResponse
+                    {
+                        BeatmapSets = setsForResponse,
+                    });
+                }
+            };
         }
 
         [Test]
-        public void TestShow()
+        public void TestNoBeatmapsPlaceholder()
         {
-            AddStep("Show", overlay.Show);
+            AddStep("fetch for 0 beatmaps", () => fetchFor());
+            AddUntilStep("placeholder shown", () => overlay.ChildrenOfType<BeatmapListingOverlay.NotFoundDrawable>().SingleOrDefault()?.IsPresent == true);
+
+            AddStep("fetch for 1 beatmap", () => fetchFor(CreateBeatmap(Ruleset.Value).BeatmapInfo.BeatmapSet));
+            AddUntilStep("placeholder hidden", () => !overlay.ChildrenOfType<BeatmapListingOverlay.NotFoundDrawable>().Any());
+
+            AddStep("fetch for 0 beatmaps", () => fetchFor());
+            AddUntilStep("placeholder shown", () => overlay.ChildrenOfType<BeatmapListingOverlay.NotFoundDrawable>().SingleOrDefault()?.IsPresent == true);
+
+            // fetch once more to ensure nothing happens in displaying placeholder again when it already is present.
+            AddStep("fetch for 0 beatmaps again", () => fetchFor());
+            AddUntilStep("placeholder shown", () => overlay.ChildrenOfType<BeatmapListingOverlay.NotFoundDrawable>().SingleOrDefault()?.IsPresent == true);
         }
 
-        [Test]
-        public void TestHide()
+        private void fetchFor(params BeatmapSetInfo[] beatmaps)
         {
-            AddStep("Hide", overlay.Hide);
+            setsForResponse.Clear();
+            setsForResponse.AddRange(beatmaps.Select(b => new TestAPIBeatmapSet(b)));
+
+            // trigger arbitrary change for fetching.
+            overlay.ChildrenOfType<BeatmapListingSearchControl>().Single().Query.TriggerChange();
+        }
+
+        private class TestAPIBeatmapSet : APIBeatmapSet
+        {
+            private readonly BeatmapSetInfo beatmapSet;
+
+            public TestAPIBeatmapSet(BeatmapSetInfo beatmapSet)
+            {
+                this.beatmapSet = beatmapSet;
+            }
+
+            public override BeatmapSetInfo ToBeatmapSet(RulesetStore rulesets) => beatmapSet;
         }
     }
 }

osu.Game.Tests/Visual/Online/TestSceneBeatmapSetOverlay.cs

@@ -231,8 +231,8 @@ namespace osu.Game.Tests.Visual.Online
                 });
             });
 
-            AddAssert("shown beatmaps of current ruleset", () => overlay.Header.Picker.Difficulties.All(b => b.Beatmap.Ruleset.Equals(overlay.Header.RulesetSelector.Current.Value)));
-            AddAssert("left-most beatmap selected", () => overlay.Header.Picker.Difficulties.First().State == BeatmapPicker.DifficultySelectorState.Selected);
+            AddAssert("shown beatmaps of current ruleset", () => overlay.Header.HeaderContent.Picker.Difficulties.All(b => b.Beatmap.Ruleset.Equals(overlay.Header.RulesetSelector.Current.Value)));
+            AddAssert("left-most beatmap selected", () => overlay.Header.HeaderContent.Picker.Difficulties.First().State == BeatmapPicker.DifficultySelectorState.Selected);
         }
 
         [Test]
@@ -310,12 +310,12 @@ namespace osu.Game.Tests.Visual.Online
 
         private void downloadAssert(bool shown)
         {
-            AddAssert($"is download button {(shown ? "shown" : "hidden")}", () => overlay.Header.DownloadButtonsVisible == shown);
+            AddAssert($"is download button {(shown ? "shown" : "hidden")}", () => overlay.Header.HeaderContent.DownloadButtonsVisible == shown);
         }
 
         private class TestBeatmapSetOverlay : BeatmapSetOverlay
         {
-            public new Header Header => base.Header;
+            public new BeatmapSetHeader Header => base.Header;
         }
     }
 }

osu.Game.Tests/Visual/Online/TestSceneOnlineBeatmapListingOverlay.cs

@@ -0,0 +1,33 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Game.Overlays;
+using NUnit.Framework;
+
+namespace osu.Game.Tests.Visual.Online
+{
+    [Description("uses online API")]
+    public class TestSceneOnlineBeatmapListingOverlay : OsuTestScene
+    {
+        protected override bool UseOnlineAPI => true;
+
+        private readonly BeatmapListingOverlay overlay;
+
+        public TestSceneOnlineBeatmapListingOverlay()
+        {
+            Add(overlay = new BeatmapListingOverlay());
+        }
+
+        [Test]
+        public void TestShow()
+        {
+            AddStep("Show", overlay.Show);
+        }
+
+        [Test]
+        public void TestHide()
+        {
+            AddStep("Hide", overlay.Hide);
+        }
+    }
+}

osu.Game.Tests/Visual/Online/TestSceneStandAloneChatDisplay.cs

@@ -8,16 +8,16 @@ using osu.Game.Users;
 using osuTK;
 using System;
 using System.Linq;
+using NUnit.Framework;
 using osu.Framework.Graphics.Containers;
 using osu.Game.Graphics.Containers;
 using osu.Game.Overlays.Chat;
+using osuTK.Input;
 
 namespace osu.Game.Tests.Visual.Online
 {
-    public class TestSceneStandAloneChatDisplay : OsuTestScene
+    public class TestSceneStandAloneChatDisplay : OsuManualInputManagerTestScene
     {
-        private readonly Channel testChannel = new Channel();
-
         private readonly User admin = new User
         {
             Username = "HappyStick",
@@ -46,92 +46,97 @@ namespace osu.Game.Tests.Visual.Online
         [Cached]
         private ChannelManager channelManager = new ChannelManager();
 
-        private readonly TestStandAloneChatDisplay chatDisplay;
-        private readonly TestStandAloneChatDisplay chatDisplay2;
+        private TestStandAloneChatDisplay chatDisplay;
+        private int messageIdSequence;
+
+        private Channel testChannel;
 
         public TestSceneStandAloneChatDisplay()
         {
             Add(channelManager);
-
-            Add(chatDisplay = new TestStandAloneChatDisplay
-            {
-                Anchor = Anchor.CentreLeft,
-                Origin = Anchor.CentreLeft,
-                Margin = new MarginPadding(20),
-                Size = new Vector2(400, 80)
-            });
-
-            Add(chatDisplay2 = new TestStandAloneChatDisplay(true)
-            {
-                Anchor = Anchor.CentreRight,
-                Origin = Anchor.CentreRight,
-                Margin = new MarginPadding(20),
-                Size = new Vector2(400, 150)
-            });
         }
 
-        protected override void LoadComplete()
+        [SetUp]
+        public void SetUp() => Schedule(() =>
         {
-            base.LoadComplete();
+            messageIdSequence = 0;
+            channelManager.CurrentChannel.Value = testChannel = new Channel();
 
-            channelManager.CurrentChannel.Value = testChannel;
+            Children = new[]
+            {
+                chatDisplay = new TestStandAloneChatDisplay
+                {
+                    Anchor = Anchor.CentreLeft,
+                    Origin = Anchor.CentreLeft,
+                    Margin = new MarginPadding(20),
+                    Size = new Vector2(400, 80),
+                    Channel = { Value = testChannel },
+                },
+                new TestStandAloneChatDisplay(true)
+                {
+                    Anchor = Anchor.CentreRight,
+                    Origin = Anchor.CentreRight,
+                    Margin = new MarginPadding(20),
+                    Size = new Vector2(400, 150),
+                    Channel = { Value = testChannel },
+                }
+            };
+        });
 
-            chatDisplay.Channel.Value = testChannel;
-            chatDisplay2.Channel.Value = testChannel;
-
-            int sequence = 0;
-
-            AddStep("message from admin", () => testChannel.AddNewMessages(new Message(sequence++)
+        [Test]
+        public void TestManyMessages()
+        {
+            AddStep("message from admin", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = admin,
                 Content = "I am a wang!"
             }));
 
-            AddStep("message from team red", () => testChannel.AddNewMessages(new Message(sequence++)
+            AddStep("message from team red", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = redUser,
                 Content = "I am team red."
             }));
 
-            AddStep("message from team red", () => testChannel.AddNewMessages(new Message(sequence++)
+            AddStep("message from team red", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = redUser,
                 Content = "I plan to win!"
             }));
 
-            AddStep("message from team blue", () => testChannel.AddNewMessages(new Message(sequence++)
+            AddStep("message from team blue", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = blueUser,
                 Content = "Not on my watch. Prepare to eat saaaaaaaaaand. Lots and lots of saaaaaaand."
             }));
 
-            AddStep("message from admin", () => testChannel.AddNewMessages(new Message(sequence++)
+            AddStep("message from admin", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = admin,
                 Content = "Okay okay, calm down guys. Let's do this!"
             }));
 
-            AddStep("message from long username", () => testChannel.AddNewMessages(new Message(sequence++)
+            AddStep("message from long username", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = longUsernameUser,
                 Content = "Hi guys, my new username is lit!"
             }));
 
-            AddStep("message with new date", () => testChannel.AddNewMessages(new Message(sequence++)
+            AddStep("message with new date", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
             {
                 Sender = longUsernameUser,
                 Content = "Message from the future!",
                 Timestamp = DateTimeOffset.Now
             }));
 
-            AddUntilStep("ensure still scrolled to bottom", () => chatDisplay.ScrolledToBottom);
+            checkScrolledToBottom();
 
             const int messages_per_call = 10;
             AddRepeatStep("add many messages", () =>
             {
                 for (int i = 0; i < messages_per_call; i++)
                 {
-                    testChannel.AddNewMessages(new Message(sequence++)
+                    testChannel.AddNewMessages(new Message(messageIdSequence++)
                     {
                         Sender = longUsernameUser,
                         Content = "Many messages! " + Guid.NewGuid(),
@@ -153,9 +158,133 @@ namespace osu.Game.Tests.Visual.Online
                 return true;
             });
 
-            AddUntilStep("ensure still scrolled to bottom", () => chatDisplay.ScrolledToBottom);
+            checkScrolledToBottom();
         }
 
+        /// <summary>
+        /// Tests that when a message gets wrapped by the chat display getting contracted while scrolled to bottom, the chat will still keep scrolling down.
+        /// </summary>
+        [Test]
+        public void TestMessageWrappingKeepsAutoScrolling()
+        {
+            fillChat();
+
+            // send message with short words for text wrapping to occur when contracting chat.
+            sendMessage();
+
+            AddStep("contract chat", () => chatDisplay.Width -= 100);
+            checkScrolledToBottom();
+
+            AddStep("send another message", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
+            {
+                Sender = admin,
+                Content = "As we were saying...",
+            }));
+
+            checkScrolledToBottom();
+        }
+
+        [Test]
+        public void TestUserScrollOverride()
+        {
+            fillChat();
+
+            sendMessage();
+            checkScrolledToBottom();
+
+            AddStep("User scroll up", () =>
+            {
+                InputManager.MoveMouseTo(chatDisplay.ScreenSpaceDrawQuad.Centre);
+                InputManager.PressButton(MouseButton.Left);
+                InputManager.MoveMouseTo(chatDisplay.ScreenSpaceDrawQuad.Centre + new Vector2(0, chatDisplay.ScreenSpaceDrawQuad.Height));
+                InputManager.ReleaseButton(MouseButton.Left);
+            });
+
+            checkNotScrolledToBottom();
+            sendMessage();
+            checkNotScrolledToBottom();
+
+            AddRepeatStep("User scroll to bottom", () =>
+            {
+                InputManager.MoveMouseTo(chatDisplay.ScreenSpaceDrawQuad.Centre);
+                InputManager.PressButton(MouseButton.Left);
+                InputManager.MoveMouseTo(chatDisplay.ScreenSpaceDrawQuad.Centre - new Vector2(0, chatDisplay.ScreenSpaceDrawQuad.Height));
+                InputManager.ReleaseButton(MouseButton.Left);
+            }, 5);
+
+            checkScrolledToBottom();
+            sendMessage();
+            checkScrolledToBottom();
+        }
+
+        [Test]
+        public void TestLocalEchoMessageResetsScroll()
+        {
+            fillChat();
+
+            sendMessage();
+            checkScrolledToBottom();
+
+            AddStep("User scroll up", () =>
+            {
+                InputManager.MoveMouseTo(chatDisplay.ScreenSpaceDrawQuad.Centre);
+                InputManager.PressButton(MouseButton.Left);
+                InputManager.MoveMouseTo(chatDisplay.ScreenSpaceDrawQuad.Centre + new Vector2(0, chatDisplay.ScreenSpaceDrawQuad.Height));
+                InputManager.ReleaseButton(MouseButton.Left);
+            });
+
+            checkNotScrolledToBottom();
+            sendMessage();
+            checkNotScrolledToBottom();
+
+            sendLocalMessage();
+            checkScrolledToBottom();
+
+            sendMessage();
+            checkScrolledToBottom();
+        }
+
+        private void fillChat()
+        {
+            AddStep("fill chat", () =>
+            {
+                for (int i = 0; i < 10; i++)
+                {
+                    testChannel.AddNewMessages(new Message(messageIdSequence++)
+                    {
+                        Sender = longUsernameUser,
+                        Content = $"some stuff {Guid.NewGuid()}",
+                    });
+                }
+            });
+
+            checkScrolledToBottom();
+        }
+
+        private void sendMessage()
+        {
+            AddStep("send lorem ipsum", () => testChannel.AddNewMessages(new Message(messageIdSequence++)
+            {
+                Sender = longUsernameUser,
+                Content = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce et bibendum velit.",
+            }));
+        }
+
+        private void sendLocalMessage()
+        {
+            AddStep("send local echo", () => testChannel.AddLocalEcho(new LocalEchoMessage
+            {
+                Sender = longUsernameUser,
+                Content = "This is a local echo message.",
+            }));
+        }
+
+        private void checkScrolledToBottom() =>
+            AddUntilStep("is scrolled to bottom", () => chatDisplay.ScrolledToBottom);
+
+        private void checkNotScrolledToBottom() =>
+            AddUntilStep("not scrolled to bottom", () => !chatDisplay.ScrolledToBottom);
+
         private class TestStandAloneChatDisplay : StandAloneChatDisplay
         {
             public TestStandAloneChatDisplay(bool textbox = false)
@@ -165,7 +294,7 @@ namespace osu.Game.Tests.Visual.Online
 
             protected DrawableChannel DrawableChannel => InternalChildren.OfType<DrawableChannel>().First();
 
-            protected OsuScrollContainer ScrollContainer => (OsuScrollContainer)((Container)DrawableChannel.Child).Child;
+            protected UserTrackingScrollContainer ScrollContainer => (UserTrackingScrollContainer)((Container)DrawableChannel.Child).Child;
 
             public FillFlowContainer FillFlow => (FillFlowContainer)ScrollContainer.Child;
 

osu.Game.Tests/Visual/Online/TestSceneVotePill.cs

@@ -7,6 +7,8 @@ using osu.Game.Overlays.Comments;
 using osu.Game.Online.API.Requests.Responses;
 using osu.Framework.Allocation;
 using osu.Game.Overlays;
+using osu.Framework.Graphics.Shapes;
+using osu.Framework.Graphics.Containers;
 
 namespace osu.Game.Tests.Visual.Online
 {
@@ -16,13 +18,33 @@ namespace osu.Game.Tests.Visual.Online
         [Cached]
         private readonly OverlayColourProvider colourProvider = new OverlayColourProvider(OverlayColourScheme.Blue);
 
-        private VotePill votePill;
+        [Cached]
+        private LoginOverlay login;
+
+        private TestPill votePill;
+        private readonly Container pillContainer;
+
+        public TestSceneVotePill()
+        {
+            AddRange(new Drawable[]
+            {
+                pillContainer = new Container
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                    AutoSizeAxes = Axes.Both
+                },
+                login = new LoginOverlay()
+            });
+        }
 
         [Test]
         public void TestUserCommentPill()
         {
+            AddStep("Hide login overlay", () => login.Hide());
             AddStep("Log in", logIn);
             AddStep("User comment", () => addVotePill(getUserComment()));
+            AddAssert("Background is transparent", () => votePill.Background.Alpha == 0);
             AddStep("Click", () => votePill.Click());
             AddAssert("Not loading", () => !votePill.IsLoading);
         }
@@ -30,8 +52,10 @@ namespace osu.Game.Tests.Visual.Online
         [Test]
         public void TestRandomCommentPill()
         {
+            AddStep("Hide login overlay", () => login.Hide());
             AddStep("Log in", logIn);
             AddStep("Random comment", () => addVotePill(getRandomComment()));
+            AddAssert("Background is visible", () => votePill.Background.Alpha == 1);
             AddStep("Click", () => votePill.Click());
             AddAssert("Loading", () => votePill.IsLoading);
         }
@@ -39,10 +63,11 @@ namespace osu.Game.Tests.Visual.Online
         [Test]
         public void TestOfflineRandomCommentPill()
         {
+            AddStep("Hide login overlay", () => login.Hide());
             AddStep("Log out", API.Logout);
             AddStep("Random comment", () => addVotePill(getRandomComment()));
             AddStep("Click", () => votePill.Click());
-            AddAssert("Not loading", () => !votePill.IsLoading);
+            AddAssert("Login overlay is visible", () => login.State.Value == Visibility.Visible);
         }
 
         private void logIn() => API.Login("localUser", "password");
@@ -63,12 +88,22 @@ namespace osu.Game.Tests.Visual.Online
 
         private void addVotePill(Comment comment)
         {
-            Clear();
-            Add(votePill = new VotePill(comment)
+            pillContainer.Clear();
+            pillContainer.Child = votePill = new TestPill(comment)
             {
                 Anchor = Anchor.Centre,
                 Origin = Anchor.Centre,
-            });
+            };
+        }
+
+        private class TestPill : VotePill
+        {
+            public new Box Background => base.Background;
+
+            public TestPill(Comment comment)
+                : base(comment)
+            {
+            }
         }
     }
 }

osu.Game.Tests/Visual/Playlists/TestScenePlaylistsLoungeSubScreen.cs

@@ -4,7 +4,6 @@
 using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Allocation;
-using osu.Framework.Graphics;
 using osu.Framework.Screens;
 using osu.Framework.Testing;
 using osu.Game.Graphics.Containers;
@@ -28,12 +27,7 @@ namespace osu.Game.Tests.Visual.Playlists
         {
             base.SetUpSteps();
 
-            AddStep("push screen", () => LoadScreen(loungeScreen = new PlaylistsLoungeSubScreen
-            {
-                Anchor = Anchor.Centre,
-                Origin = Anchor.Centre,
-                Width = 0.5f,
-            }));
+            AddStep("push screen", () => LoadScreen(loungeScreen = new PlaylistsLoungeSubScreen()));
 
             AddUntilStep("wait for present", () => loungeScreen.IsCurrentScreen());
         }

osu.Game.Tests/Visual/UserInterface/TestSceneModIcon.cs

@@ -0,0 +1,21 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using NUnit.Framework;
+using osu.Game.Rulesets.Osu.Mods;
+using osu.Game.Rulesets.UI;
+
+namespace osu.Game.Tests.Visual.UserInterface
+{
+    public class TestSceneModIcon : OsuTestScene
+    {
+        [Test]
+        public void TestChangeModType()
+        {
+            ModIcon icon = null;
+
+            AddStep("create mod icon", () => Child = icon = new ModIcon(new OsuModDoubleTime()));
+            AddStep("change mod", () => icon.Mod = new OsuModEasy());
+        }
+    }
+}

osu.Game.Tests/Visual/UserInterface/TestSceneModSelectOverlay.cs

@@ -8,6 +8,7 @@ using NUnit.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
 using osu.Framework.Testing;
 using osu.Game.Graphics.Sprites;
 using osu.Game.Graphics.UserInterface;
@@ -38,27 +39,7 @@ namespace osu.Game.Tests.Visual.UserInterface
         }
 
         [SetUp]
-        public void SetUp() => Schedule(() =>
-        {
-            Children = new Drawable[]
-            {
-                modSelect = new TestModSelectOverlay
-                {
-                    Origin = Anchor.BottomCentre,
-                    Anchor = Anchor.BottomCentre,
-                    SelectedMods = { BindTarget = SelectedMods }
-                },
-
-                modDisplay = new ModDisplay
-                {
-                    Anchor = Anchor.TopRight,
-                    Origin = Anchor.TopRight,
-                    AutoSizeAxes = Axes.Both,
-                    Position = new Vector2(-5, 25),
-                    Current = { BindTarget = modSelect.SelectedMods }
-                }
-            };
-        });
+        public void SetUp() => Schedule(() => createDisplay(() => new TestModSelectOverlay()));
 
         [SetUpSteps]
         public void SetUpSteps()
@@ -66,6 +47,32 @@ namespace osu.Game.Tests.Visual.UserInterface
             AddStep("show", () => modSelect.Show());
         }
 
+        [Test]
+        public void TestAnimationFlushOnClose()
+        {
+            changeRuleset(0);
+
+            AddStep("Select all fun mods", () =>
+            {
+                modSelect.ModSectionsContainer
+                         .Single(c => c.ModType == ModType.DifficultyIncrease)
+                         .SelectAll();
+            });
+
+            AddUntilStep("many mods selected", () => modDisplay.Current.Value.Count >= 5);
+
+            AddStep("trigger deselect and close overlay", () =>
+            {
+                modSelect.ModSectionsContainer
+                         .Single(c => c.ModType == ModType.DifficultyIncrease)
+                         .DeselectAll();
+
+                modSelect.Hide();
+            });
+
+            AddAssert("all mods deselected", () => modDisplay.Current.Value.Count == 0);
+        }
+
         [Test]
         public void TestOsuMods()
         {
@@ -134,6 +141,8 @@ namespace osu.Game.Tests.Visual.UserInterface
         [Test]
         public void TestExternallySetCustomizedMod()
         {
+            changeRuleset(0);
+
             AddStep("set customized mod externally", () => SelectedMods.Value = new[] { new OsuModDoubleTime { SpeedChange = { Value = 1.01 } } });
 
             AddAssert("ensure button is selected and customized accordingly", () =>
@@ -143,6 +152,46 @@ namespace osu.Game.Tests.Visual.UserInterface
             });
         }
 
+        [Test]
+        public void TestNonStacked()
+        {
+            changeRuleset(0);
+
+            AddStep("create overlay", () => createDisplay(() => new TestNonStackedModSelectOverlay()));
+
+            AddStep("show", () => modSelect.Show());
+
+            AddAssert("ensure all buttons are spread out", () => modSelect.ChildrenOfType<ModButton>().All(m => m.Mods.Length <= 1));
+        }
+
+        [Test]
+        public void TestChangeIsValidChangesButtonVisibility()
+        {
+            changeRuleset(0);
+
+            AddAssert("double time visible", () => modSelect.ChildrenOfType<ModButton>().Any(b => b.Mods.Any(m => m is OsuModDoubleTime)));
+
+            AddStep("make double time invalid", () => modSelect.IsValidMod = m => !(m is OsuModDoubleTime));
+            AddUntilStep("double time not visible", () => modSelect.ChildrenOfType<ModButton>().All(b => !b.Mods.Any(m => m is OsuModDoubleTime)));
+            AddAssert("nightcore still visible", () => modSelect.ChildrenOfType<ModButton>().Any(b => b.Mods.Any(m => m is OsuModNightcore)));
+
+            AddStep("make double time valid again", () => modSelect.IsValidMod = m => true);
+            AddUntilStep("double time visible", () => modSelect.ChildrenOfType<ModButton>().Any(b => b.Mods.Any(m => m is OsuModDoubleTime)));
+            AddAssert("nightcore still visible", () => modSelect.ChildrenOfType<ModButton>().Any(b => b.Mods.Any(m => m is OsuModNightcore)));
+        }
+
+        [Test]
+        public void TestChangeIsValidPreservesSelection()
+        {
+            changeRuleset(0);
+
+            AddStep("select DT + HD", () => SelectedMods.Value = new Mod[] { new OsuModDoubleTime(), new OsuModHidden() });
+            AddAssert("DT + HD selected", () => modSelect.ChildrenOfType<ModButton>().Count(b => b.Selected) == 2);
+
+            AddStep("make NF invalid", () => modSelect.IsValidMod = m => !(m is ModNoFail));
+            AddAssert("DT + HD still selected", () => modSelect.ChildrenOfType<ModButton>().Count(b => b.Selected) == 2);
+        }
+
         private void testSingleMod(Mod mod)
         {
             selectNext(mod);
@@ -262,12 +311,37 @@ namespace osu.Game.Tests.Visual.UserInterface
 
         private void checkLabelColor(Func<Color4> getColour) => AddAssert("check label has expected colour", () => modSelect.MultiplierLabel.Colour.AverageColour == getColour());
 
-        private class TestModSelectOverlay : ModSelectOverlay
+        private void createDisplay(Func<TestModSelectOverlay> createOverlayFunc)
+        {
+            SelectedMods.Value = Array.Empty<Mod>();
+            Children = new Drawable[]
+            {
+                modSelect = createOverlayFunc().With(d =>
+                {
+                    d.Origin = Anchor.BottomCentre;
+                    d.Anchor = Anchor.BottomCentre;
+                    d.SelectedMods.BindTarget = SelectedMods;
+                }),
+                modDisplay = new ModDisplay
+                {
+                    Anchor = Anchor.TopRight,
+                    Origin = Anchor.TopRight,
+                    AutoSizeAxes = Axes.Both,
+                    Position = new Vector2(-5, 25),
+                    Current = { BindTarget = modSelect.SelectedMods }
+                }
+            };
+        }
+
+        private class TestModSelectOverlay : LocalPlayerModSelectOverlay
         {
             public new Bindable<IReadOnlyList<Mod>> SelectedMods => base.SelectedMods;
 
             public bool AllLoaded => ModSectionsContainer.Children.All(c => c.ModIconsLoaded);
 
+            public new FillFlowContainer<ModSection> ModSectionsContainer =>
+                base.ModSectionsContainer;
+
             public ModButton GetModButton(Mod mod)
             {
                 var section = ModSectionsContainer.Children.Single(s => s.ModType == mod.Type);
@@ -280,5 +354,10 @@ namespace osu.Game.Tests.Visual.UserInterface
             public new Color4 LowMultiplierColour => base.LowMultiplierColour;
             public new Color4 HighMultiplierColour => base.HighMultiplierColour;
         }
+
+        private class TestNonStackedModSelectOverlay : TestModSelectOverlay
+        {
+            protected override bool Stacked => false;
+        }
     }
 }

osu.Game.Tests/Visual/UserInterface/TestSceneModSettings.cs

@@ -151,7 +151,7 @@ namespace osu.Game.Tests.Visual.UserInterface
             AddUntilStep("wait for ready", () => modSelect.State.Value == Visibility.Visible && modSelect.ButtonsLoaded);
         }
 
-        private class TestModSelectOverlay : ModSelectOverlay
+        private class TestModSelectOverlay : LocalPlayerModSelectOverlay
         {
             public new VisibilityContainer ModSettingsContainer => base.ModSettingsContainer;
             public new TriangleButton CustomiseButton => base.CustomiseButton;

osu.Game.Tests/Visual/UserInterface/TestSceneSectionsContainer.cs

@@ -0,0 +1,122 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Colour;
+using osu.Framework.Graphics.Shapes;
+using osu.Game.Graphics.Containers;
+using osuTK.Graphics;
+
+namespace osu.Game.Tests.Visual.UserInterface
+{
+    public class TestSceneSectionsContainer : OsuManualInputManagerTestScene
+    {
+        private readonly SectionsContainer<TestSection> container;
+        private float custom;
+        private const float header_height = 100;
+
+        public TestSceneSectionsContainer()
+        {
+            container = new SectionsContainer<TestSection>
+            {
+                RelativeSizeAxes = Axes.Y,
+                Width = 300,
+                Origin = Anchor.Centre,
+                Anchor = Anchor.Centre,
+                FixedHeader = new Box
+                {
+                    Alpha = 0.5f,
+                    Width = 300,
+                    Height = header_height,
+                    Colour = Color4.Red
+                }
+            };
+            container.SelectedSection.ValueChanged += section =>
+            {
+                if (section.OldValue != null)
+                    section.OldValue.Selected = false;
+                if (section.NewValue != null)
+                    section.NewValue.Selected = true;
+            };
+            Add(container);
+        }
+
+        [Test]
+        public void TestSelection()
+        {
+            AddStep("clear", () => container.Clear());
+            AddStep("add 1/8th", () => append(1 / 8.0f));
+            AddStep("add third", () => append(1 / 3.0f));
+            AddStep("add half", () => append(1 / 2.0f));
+            AddStep("add full", () => append(1));
+            AddSliderStep("set custom", 0.1f, 1.1f, 0.5f, i => custom = i);
+            AddStep("add custom", () => append(custom));
+            AddStep("scroll to previous", () => container.ScrollTo(
+                container.Children.Reverse().SkipWhile(s => s != container.SelectedSection.Value).Skip(1).FirstOrDefault() ?? container.Children.First()
+            ));
+            AddStep("scroll to next", () => container.ScrollTo(
+                container.Children.SkipWhile(s => s != container.SelectedSection.Value).Skip(1).FirstOrDefault() ?? container.Children.Last()
+            ));
+            AddStep("scroll up", () => triggerUserScroll(1));
+            AddStep("scroll down", () => triggerUserScroll(-1));
+        }
+
+        [Test]
+        public void TestCorrectSectionSelected()
+        {
+            const int sections_count = 11;
+            float[] alternating = { 0.07f, 0.33f, 0.16f, 0.33f };
+            AddStep("clear", () => container.Clear());
+            AddStep("fill with sections", () =>
+            {
+                for (int i = 0; i < sections_count; i++)
+                    append(alternating[i % alternating.Length]);
+            });
+
+            void step(int scrollIndex)
+            {
+                AddStep($"scroll to section {scrollIndex + 1}", () => container.ScrollTo(container.Children[scrollIndex]));
+                AddUntilStep("correct section selected", () => container.SelectedSection.Value == container.Children[scrollIndex]);
+            }
+
+            for (int i = 1; i < sections_count; i++)
+                step(i);
+            for (int i = sections_count - 2; i >= 0; i--)
+                step(i);
+
+            AddStep("scroll almost to end", () => container.ScrollTo(container.Children[sections_count - 2]));
+            AddUntilStep("correct section selected", () => container.SelectedSection.Value == container.Children[sections_count - 2]);
+            AddStep("scroll down", () => triggerUserScroll(-1));
+            AddUntilStep("correct section selected", () => container.SelectedSection.Value == container.Children[sections_count - 1]);
+        }
+
+        private static readonly ColourInfo selected_colour = ColourInfo.GradientVertical(Color4.Yellow, Color4.Gold);
+        private static readonly ColourInfo default_colour = ColourInfo.GradientVertical(Color4.White, Color4.DarkGray);
+
+        private void append(float multiplier)
+        {
+            container.Add(new TestSection
+            {
+                Width = 300,
+                Height = (container.ChildSize.Y - header_height) * multiplier,
+                Colour = default_colour
+            });
+        }
+
+        private void triggerUserScroll(float direction)
+        {
+            InputManager.MoveMouseTo(container);
+            InputManager.ScrollVerticalBy(direction);
+        }
+
+        private class TestSection : Box
+        {
+            public bool Selected
+            {
+                set => Colour = value ? selected_colour : default_colour;
+            }
+        }
+    }
+}

osu.Game.Tests/osu.Game.Tests.csproj

@@ -7,6 +7,7 @@
     <PackageReference Include="NUnit" Version="3.12.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="3.17.0" />
     <PackageReference Update="Microsoft.EntityFrameworkCore.Sqlite" Version="2.1.4" />
+    <PackageReference Include="Moq" Version="4.16.0" />
   </ItemGroup>
   <PropertyGroup Label="Project">
     <OutputType>WinExe</OutputType>

osu.Game.Tournament.Tests/Components/TestSceneTournamentModDisplay.cs

@@ -0,0 +1,60 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Beatmaps;
+using osu.Game.Online.API;
+using osu.Game.Online.API.Requests;
+using osu.Game.Online.API.Requests.Responses;
+using osu.Game.Rulesets;
+using osu.Game.Tournament.Components;
+
+namespace osu.Game.Tournament.Tests.Components
+{
+    public class TestSceneTournamentModDisplay : TournamentTestScene
+    {
+        [Resolved]
+        private IAPIProvider api { get; set; }
+
+        [Resolved]
+        private RulesetStore rulesets { get; set; }
+
+        private FillFlowContainer<TournamentBeatmapPanel> fillFlow;
+
+        private BeatmapInfo beatmap;
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            var req = new GetBeatmapRequest(new BeatmapInfo { OnlineBeatmapID = 490154 });
+            req.Success += success;
+            api.Queue(req);
+
+            Add(fillFlow = new FillFlowContainer<TournamentBeatmapPanel>
+            {
+                RelativeSizeAxes = Axes.Both,
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                Direction = FillDirection.Full,
+                Spacing = new osuTK.Vector2(10)
+            });
+        }
+
+        private void success(APIBeatmap apiBeatmap)
+        {
+            beatmap = apiBeatmap.ToBeatmap(rulesets);
+            var mods = rulesets.GetRuleset(Ladder.Ruleset.Value.ID ?? 0).CreateInstance().GetAllMods();
+
+            foreach (var mod in mods)
+            {
+                fillFlow.Add(new TournamentBeatmapPanel(beatmap, mod.Acronym)
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre
+                });
+            }
+        }
+    }
+}

osu.Game.Tournament.Tests/Screens/TestSceneScheduleScreen.cs

@@ -1,6 +1,8 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
+using NUnit.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Game.Tournament.Components;
@@ -16,5 +18,23 @@ namespace osu.Game.Tournament.Tests.Screens
             Add(new TourneyVideo("main") { RelativeSizeAxes = Axes.Both });
             Add(new ScheduleScreen());
         }
+
+        [Test]
+        public void TestCurrentMatchTime()
+        {
+            setMatchDate(TimeSpan.FromDays(-1));
+            setMatchDate(TimeSpan.FromSeconds(5));
+            setMatchDate(TimeSpan.FromMinutes(4));
+            setMatchDate(TimeSpan.FromHours(3));
+        }
+
+        private void setMatchDate(TimeSpan relativeTime)
+            // Humanizer cannot handle negative timespans.
+            => AddStep($"start time is {relativeTime}", () =>
+            {
+                var match = CreateSampleMatch();
+                match.Date.Value = DateTimeOffset.Now + relativeTime;
+                Ladder.CurrentMatch.Value = match;
+            });
     }
 }

osu.Game.Tournament/Components/TournamentBeatmapPanel.cs

@@ -9,7 +9,6 @@ using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
-using osu.Framework.Graphics.Sprites;
 using osu.Framework.Graphics.Textures;
 using osu.Framework.Localisation;
 using osu.Game.Beatmaps;
@@ -23,7 +22,7 @@ namespace osu.Game.Tournament.Components
     public class TournamentBeatmapPanel : CompositeDrawable
     {
         public readonly BeatmapInfo Beatmap;
-        private readonly string mods;
+        private readonly string mod;
 
         private const float horizontal_padding = 10;
         private const float vertical_padding = 10;
@@ -33,12 +32,12 @@ namespace osu.Game.Tournament.Components
         private readonly Bindable<TournamentMatch> currentMatch = new Bindable<TournamentMatch>();
         private Box flash;
 
-        public TournamentBeatmapPanel(BeatmapInfo beatmap, string mods = null)
+        public TournamentBeatmapPanel(BeatmapInfo beatmap, string mod = null)
         {
             if (beatmap == null) throw new ArgumentNullException(nameof(beatmap));
 
             Beatmap = beatmap;
-            this.mods = mods;
+            this.mod = mod;
             Width = 400;
             Height = HEIGHT;
         }
@@ -122,23 +121,15 @@ namespace osu.Game.Tournament.Components
                 },
             });
 
-            if (!string.IsNullOrEmpty(mods))
+            if (!string.IsNullOrEmpty(mod))
             {
-                AddInternal(new Container
+                AddInternal(new TournamentModIcon(mod)
                 {
-                    RelativeSizeAxes = Axes.Y,
-                    Width = 60,
                     Anchor = Anchor.CentreRight,
                     Origin = Anchor.CentreRight,
                     Margin = new MarginPadding(10),
-                    Child = new Sprite
-                    {
-                        FillMode = FillMode.Fit,
-                        RelativeSizeAxes = Axes.Both,
-                        Anchor = Anchor.CentreRight,
-                        Origin = Anchor.CentreRight,
-                        Texture = textures.Get($"mods/{mods}"),
-                    }
+                    Width = 60,
+                    RelativeSizeAxes = Axes.Y,
                 });
             }
         }

osu.Game.Tournament/Components/TournamentModIcon.cs

@@ -0,0 +1,65 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.Textures;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.UI;
+using osu.Game.Tournament.Models;
+using osuTK;
+
+namespace osu.Game.Tournament.Components
+{
+    /// <summary>
+    /// Mod icon displayed in tournament usages, allowing user overridden graphics.
+    /// </summary>
+    public class TournamentModIcon : CompositeDrawable
+    {
+        private readonly string modAcronym;
+
+        [Resolved]
+        private RulesetStore rulesets { get; set; }
+
+        public TournamentModIcon(string modAcronym)
+        {
+            this.modAcronym = modAcronym;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(TextureStore textures, LadderInfo ladderInfo)
+        {
+            var customTexture = textures.Get($"mods/{modAcronym}");
+
+            if (customTexture != null)
+            {
+                AddInternal(new Sprite
+                {
+                    FillMode = FillMode.Fit,
+                    RelativeSizeAxes = Axes.Both,
+                    Anchor = Anchor.CentreRight,
+                    Origin = Anchor.CentreRight,
+                    Texture = customTexture
+                });
+
+                return;
+            }
+
+            var ruleset = rulesets.GetRuleset(ladderInfo.Ruleset.Value?.ID ?? 0);
+            var modIcon = ruleset?.CreateInstance().GetAllMods().FirstOrDefault(mod => mod.Acronym == modAcronym);
+
+            if (modIcon == null)
+                return;
+
+            AddInternal(new ModIcon(modIcon, false)
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                Scale = new Vector2(0.5f)
+            });
+        }
+    }
+}

osu.Game.Tournament/Screens/Schedule/ScheduleScreen.cs

@@ -192,12 +192,7 @@ namespace osu.Game.Tournament.Screens.Schedule
                                         Origin = Anchor.CentreLeft,
                                         Children = new Drawable[]
                                         {
-                                            new TournamentSpriteText
-                                            {
-                                                Text = "Starting ",
-                                                Font = OsuFont.Torus.With(size: 24, weight: FontWeight.Regular)
-                                            },
-                                            new DrawableDate(match.NewValue.Date.Value)
+                                            new ScheduleMatchDate(match.NewValue.Date.Value)
                                             {
                                                 Font = OsuFont.Torus.With(size: 24, weight: FontWeight.Regular)
                                             }
@@ -251,6 +246,18 @@ namespace osu.Game.Tournament.Screens.Schedule
             }
         }
 
+        public class ScheduleMatchDate : DrawableDate
+        {
+            public ScheduleMatchDate(DateTimeOffset date, float textSize = OsuFont.DEFAULT_FONT_SIZE, bool italic = true)
+                : base(date, textSize, italic)
+            {
+            }
+
+            protected override string Format() => Date < DateTimeOffset.Now
+                ? $"Started {base.Format()}"
+                : $"Starting {base.Format()}";
+        }
+
         public class ScheduleContainer : Container
         {
             protected override Container<Drawable> Content => content;

osu.Game/Beatmaps/Beatmap.cs

@@ -50,15 +50,7 @@ namespace osu.Game.Beatmaps
 
         IBeatmap IBeatmap.Clone() => Clone();
 
-        public Beatmap<T> Clone()
-        {
-            var clone = (Beatmap<T>)MemberwiseClone();
-
-            clone.ControlPointInfo = ControlPointInfo.CreateCopy();
-            // todo: deep clone other elements as required.
-
-            return clone;
-        }
+        public Beatmap<T> Clone() => (Beatmap<T>)MemberwiseClone();
     }
 
     public class Beatmap : Beatmap<HitObject>

osu.Game/Beatmaps/BeatmapManager_BeatmapOnlineLookupQueue.cs

@@ -7,7 +7,6 @@ using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
-using Dapper;
 using Microsoft.Data.Sqlite;
 using osu.Framework.Development;
 using osu.Framework.IO.Network;
@@ -154,20 +153,31 @@ namespace osu.Game.Beatmaps
                 {
                     using (var db = new SqliteConnection(storage.GetDatabaseConnectionString("online")))
                     {
-                        var found = db.QuerySingleOrDefault<CachedOnlineBeatmapLookup>(
-                            "SELECT * FROM osu_beatmaps WHERE checksum = @MD5Hash OR beatmap_id = @OnlineBeatmapID OR filename = @Path", beatmap);
+                        db.Open();
 
-                        if (found != null)
+                        using (var cmd = db.CreateCommand())
                         {
-                            var status = (BeatmapSetOnlineStatus)found.approved;
+                            cmd.CommandText = "SELECT beatmapset_id, beatmap_id, approved FROM osu_beatmaps WHERE checksum = @MD5Hash OR beatmap_id = @OnlineBeatmapID OR filename = @Path";
 
-                            beatmap.Status = status;
-                            beatmap.BeatmapSet.Status = status;
-                            beatmap.BeatmapSet.OnlineBeatmapSetID = found.beatmapset_id;
-                            beatmap.OnlineBeatmapID = found.beatmap_id;
+                            cmd.Parameters.Add(new SqliteParameter("@MD5Hash", beatmap.MD5Hash));
+                            cmd.Parameters.Add(new SqliteParameter("@OnlineBeatmapID", beatmap.OnlineBeatmapID ?? (object)DBNull.Value));
+                            cmd.Parameters.Add(new SqliteParameter("@Path", beatmap.Path));
 
-                            LogForModel(set, $"Cached local retrieval for {beatmap}.");
-                            return true;
+                            using (var reader = cmd.ExecuteReader())
+                            {
+                                if (reader.Read())
+                                {
+                                    var status = (BeatmapSetOnlineStatus)reader.GetByte(2);
+
+                                    beatmap.Status = status;
+                                    beatmap.BeatmapSet.Status = status;
+                                    beatmap.BeatmapSet.OnlineBeatmapSetID = reader.GetInt32(0);
+                                    beatmap.OnlineBeatmapID = reader.GetInt32(1);
+
+                                    LogForModel(set, $"Cached local retrieval for {beatmap}.");
+                                    return true;
+                                }
+                            }
                         }
                     }
                 }

osu.Game/Beatmaps/Formats/LegacyStoryboardDecoder.cs

@@ -139,7 +139,7 @@ namespace osu.Game.Beatmaps.Formats
                             // this is random as hell but taken straight from osu-stable.
                             frameDelay = Math.Round(0.015 * frameDelay) * 1.186 * (1000 / 60f);
 
-                        var loopType = split.Length > 8 ? (AnimationLoopType)Enum.Parse(typeof(AnimationLoopType), split[8]) : AnimationLoopType.LoopForever;
+                        var loopType = split.Length > 8 ? parseAnimationLoopType(split[8]) : AnimationLoopType.LoopForever;
                         storyboardSprite = new StoryboardAnimation(path, origin, new Vector2(x, y), frameCount, frameDelay, loopType);
                         storyboard.GetLayer(layer).Add(storyboardSprite);
                         break;
@@ -341,6 +341,12 @@ namespace osu.Game.Beatmaps.Formats
             }
         }
 
+        private AnimationLoopType parseAnimationLoopType(string value)
+        {
+            var parsed = (AnimationLoopType)Enum.Parse(typeof(AnimationLoopType), value);
+            return Enum.IsDefined(typeof(AnimationLoopType), parsed) ? parsed : AnimationLoopType.LoopForever;
+        }
+
         private void handleVariables(string line)
         {
             var pair = SplitKeyVal(line, '=');

osu.Game/Beatmaps/IBeatmap.cs

@@ -24,7 +24,7 @@ namespace osu.Game.Beatmaps
         /// <summary>
         /// The control points in this beatmap.
         /// </summary>
-        ControlPointInfo ControlPointInfo { get; }
+        ControlPointInfo ControlPointInfo { get; set; }
 
         /// <summary>
         /// The breaks in this beatmap.

osu.Game/Database/ArchiveModelManager.cs

@@ -308,7 +308,7 @@ namespace osu.Game.Database
         /// <param name="item">The model to be imported.</param>
         /// <param name="archive">An optional archive to use for model population.</param>
         /// <param name="cancellationToken">An optional cancellation token.</param>
-        public async Task<TModel> Import(TModel item, ArchiveReader archive = null, CancellationToken cancellationToken = default) => await Task.Factory.StartNew(async () =>
+        public virtual async Task<TModel> Import(TModel item, ArchiveReader archive = null, CancellationToken cancellationToken = default) => await Task.Factory.StartNew(async () =>
         {
             cancellationToken.ThrowIfCancellationRequested();
 

osu.Game/Extensions/TaskExtensions.cs

@@ -1,36 +0,0 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
-// See the LICENCE file in the repository root for full licence text.
-
-#nullable enable
-
-using System;
-using System.Threading.Tasks;
-using osu.Framework.Extensions.ExceptionExtensions;
-using osu.Framework.Logging;
-
-namespace osu.Game.Extensions
-{
-    public static class TaskExtensions
-    {
-        /// <summary>
-        /// Denote a task which is to be run without local error handling logic, where failure is not catastrophic.
-        /// Avoids unobserved exceptions from being fired.
-        /// </summary>
-        /// <param name="task">The task.</param>
-        /// <param name="logAsError">
-        /// Whether errors should be logged as errors visible to users, or as debug messages.
-        /// Logging as debug will essentially silence the errors on non-release builds.
-        /// </param>
-        public static void CatchUnobservedExceptions(this Task task, bool logAsError = false)
-        {
-            task.ContinueWith(t =>
-            {
-                Exception? exception = t.Exception?.AsSingular();
-                if (logAsError)
-                    Logger.Error(exception, $"Error running task: {exception?.Message ?? "(unknown)"}", LoggingTarget.Runtime, true);
-                else
-                    Logger.Log($"Error running task: {exception}", LoggingTarget.Runtime, LogLevel.Debug);
-            }, TaskContinuationOptions.NotOnRanToCompletion);
-        }
-    }
-}

osu.Game/Graphics/Containers/ParallaxContainer.cs

@@ -24,6 +24,10 @@ namespace osu.Game.Graphics.Containers
 
         private Bindable<bool> parallaxEnabled;
 
+        private const float parallax_duration = 100;
+
+        private bool firstUpdate = true;
+
         public ParallaxContainer()
         {
             RelativeSizeAxes = Axes.Both;
@@ -60,17 +64,27 @@ namespace osu.Game.Graphics.Containers
             input = GetContainingInputManager();
         }
 
-        private bool firstUpdate = true;
-
         protected override void Update()
         {
             base.Update();
 
             if (parallaxEnabled.Value)
             {
-                Vector2 offset = (input.CurrentState.Mouse == null ? Vector2.Zero : ToLocalSpace(input.CurrentState.Mouse.Position) - DrawSize / 2) * ParallaxAmount;
+                Vector2 offset = Vector2.Zero;
 
-                const float parallax_duration = 100;
+                if (input.CurrentState.Mouse != null)
+                {
+                    var sizeDiv2 = DrawSize / 2;
+
+                    Vector2 relativeAmount = ToLocalSpace(input.CurrentState.Mouse.Position) - sizeDiv2;
+
+                    const float base_factor = 0.999f;
+
+                    relativeAmount.X = (float)(Math.Sign(relativeAmount.X) * Interpolation.Damp(0, 1, base_factor, Math.Abs(relativeAmount.X)));
+                    relativeAmount.Y = (float)(Math.Sign(relativeAmount.Y) * Interpolation.Damp(0, 1, base_factor, Math.Abs(relativeAmount.Y)));
+
+                    offset = relativeAmount * sizeDiv2 * ParallaxAmount;
+                }
 
                 double elapsed = Math.Clamp(Clock.ElapsedFrameTime, 0, parallax_duration);
 

osu.Game/Graphics/Containers/SectionsContainer.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Diagnostics;
 using System.Linq;
 using JetBrains.Annotations;
 using osu.Framework.Allocation;
@@ -9,6 +10,7 @@ using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Layout;
+using osu.Framework.Utils;
 
 namespace osu.Game.Graphics.Containers
 {
@@ -20,6 +22,7 @@ namespace osu.Game.Graphics.Containers
         where T : Drawable
     {
         public Bindable<T> SelectedSection { get; } = new Bindable<T>();
+        private Drawable lastClickedSection;
 
         public Drawable ExpandableHeader
         {
@@ -36,7 +39,7 @@ namespace osu.Game.Graphics.Containers
                 if (value == null) return;
 
                 AddInternal(expandableHeader);
-                lastKnownScroll = float.NaN;
+                lastKnownScroll = null;
             }
         }
 
@@ -52,7 +55,7 @@ namespace osu.Game.Graphics.Containers
                 if (value == null) return;
 
                 AddInternal(fixedHeader);
-                lastKnownScroll = float.NaN;
+                lastKnownScroll = null;
             }
         }
 
@@ -71,7 +74,7 @@ namespace osu.Game.Graphics.Containers
                 footer.Anchor |= Anchor.y2;
                 footer.Origin |= Anchor.y2;
                 scrollContainer.Add(footer);
-                lastKnownScroll = float.NaN;
+                lastKnownScroll = null;
             }
         }
 
@@ -89,21 +92,26 @@ namespace osu.Game.Graphics.Containers
 
                 headerBackgroundContainer.Add(headerBackground);
 
-                lastKnownScroll = float.NaN;
+                lastKnownScroll = null;
             }
         }
 
         protected override Container<T> Content => scrollContentContainer;
 
-        private readonly OsuScrollContainer scrollContainer;
+        private readonly UserTrackingScrollContainer scrollContainer;
         private readonly Container headerBackgroundContainer;
         private readonly MarginPadding originalSectionsMargin;
         private Drawable expandableHeader, fixedHeader, footer, headerBackground;
         private FlowContainer<T> scrollContentContainer;
 
-        private float headerHeight, footerHeight;
+        private float? headerHeight, footerHeight;
 
-        private float lastKnownScroll;
+        private float? lastKnownScroll;
+
+        /// <summary>
+        /// The percentage of the container to consider the centre-point for deciding the active section (and scrolling to a requested section).
+        /// </summary>
+        private const float scroll_y_centre = 0.1f;
 
         public SectionsContainer()
         {
@@ -128,18 +136,24 @@ namespace osu.Game.Graphics.Containers
         public override void Add(T drawable)
         {
             base.Add(drawable);
-            lastKnownScroll = float.NaN;
-            headerHeight = float.NaN;
-            footerHeight = float.NaN;
+
+            Debug.Assert(drawable != null);
+
+            lastKnownScroll = null;
+            headerHeight = null;
+            footerHeight = null;
         }
 
-        public void ScrollTo(Drawable section) =>
-            scrollContainer.ScrollTo(scrollContainer.GetChildPosInContent(section) - (FixedHeader?.BoundingBox.Height ?? 0));
+        public void ScrollTo(Drawable section)
+        {
+            lastClickedSection = section;
+            scrollContainer.ScrollTo(scrollContainer.GetChildPosInContent(section) - scrollContainer.DisplayableContent * scroll_y_centre - (FixedHeader?.BoundingBox.Height ?? 0));
+        }
 
         public void ScrollToTop() => scrollContainer.ScrollTo(0);
 
         [NotNull]
-        protected virtual OsuScrollContainer CreateScrollContainer() => new OsuScrollContainer();
+        protected virtual UserTrackingScrollContainer CreateScrollContainer() => new UserTrackingScrollContainer();
 
         [NotNull]
         protected virtual FlowContainer<T> CreateScrollContentContainer() =>
@@ -156,7 +170,7 @@ namespace osu.Game.Graphics.Containers
 
             if (source == InvalidationSource.Child && (invalidation & Invalidation.DrawSize) != 0)
             {
-                lastKnownScroll = -1;
+                lastKnownScroll = null;
                 result = true;
             }
 
@@ -167,7 +181,10 @@ namespace osu.Game.Graphics.Containers
         {
             base.UpdateAfterChildren();
 
-            float headerH = (ExpandableHeader?.LayoutSize.Y ?? 0) + (FixedHeader?.LayoutSize.Y ?? 0);
+            float fixedHeaderSize = FixedHeader?.LayoutSize.Y ?? 0;
+            float expandableHeaderSize = ExpandableHeader?.LayoutSize.Y ?? 0;
+
+            float headerH = expandableHeaderSize + fixedHeaderSize;
             float footerH = Footer?.LayoutSize.Y ?? 0;
 
             if (headerH != headerHeight || footerH != footerHeight)
@@ -183,28 +200,39 @@ namespace osu.Game.Graphics.Containers
             {
                 lastKnownScroll = currentScroll;
 
+                // reset last clicked section because user started scrolling themselves
+                if (scrollContainer.UserScrolling)
+                    lastClickedSection = null;
+
                 if (ExpandableHeader != null && FixedHeader != null)
                 {
-                    float offset = Math.Min(ExpandableHeader.LayoutSize.Y, currentScroll);
+                    float offset = Math.Min(expandableHeaderSize, currentScroll);
 
                     ExpandableHeader.Y = -offset;
-                    FixedHeader.Y = -offset + ExpandableHeader.LayoutSize.Y;
+                    FixedHeader.Y = -offset + expandableHeaderSize;
                 }
 
-                headerBackgroundContainer.Height = (ExpandableHeader?.LayoutSize.Y ?? 0) + (FixedHeader?.LayoutSize.Y ?? 0);
+                headerBackgroundContainer.Height = expandableHeaderSize + fixedHeaderSize;
                 headerBackgroundContainer.Y = ExpandableHeader?.Y ?? 0;
 
-                float scrollOffset = FixedHeader?.LayoutSize.Y ?? 0;
-                Func<T, float> diff = section => scrollContainer.GetChildPosInContent(section) - currentScroll - scrollOffset;
+                var smallestSectionHeight = Children.Count > 0 ? Children.Min(d => d.Height) : 0;
 
-                if (scrollContainer.IsScrolledToEnd())
-                {
-                    SelectedSection.Value = Children.LastOrDefault();
-                }
+                // scroll offset is our fixed header height if we have it plus 10% of content height
+                // plus 5% to fix floating point errors and to not have a section instantly unselect when scrolling upwards
+                // but the 5% can't be bigger than our smallest section height, otherwise it won't get selected correctly
+                float selectionLenienceAboveSection = Math.Min(smallestSectionHeight / 2.0f, scrollContainer.DisplayableContent * 0.05f);
+
+                float scrollCentre = fixedHeaderSize + scrollContainer.DisplayableContent * scroll_y_centre + selectionLenienceAboveSection;
+
+                if (Precision.AlmostBigger(0, scrollContainer.Current))
+                    SelectedSection.Value = lastClickedSection as T ?? Children.FirstOrDefault();
+                else if (Precision.AlmostBigger(scrollContainer.Current, scrollContainer.ScrollableExtent))
+                    SelectedSection.Value = lastClickedSection as T ?? Children.LastOrDefault();
                 else
                 {
-                    SelectedSection.Value = Children.TakeWhile(section => diff(section) <= 0).LastOrDefault()
-                                            ?? Children.FirstOrDefault();
+                    SelectedSection.Value = Children
+                                            .TakeWhile(section => scrollContainer.GetChildPosInContent(section) - currentScroll - scrollCentre <= 0)
+                                            .LastOrDefault() ?? Children.FirstOrDefault();
                 }
             }
         }
@@ -214,8 +242,9 @@ namespace osu.Game.Graphics.Containers
             if (!Children.Any()) return;
 
             var newMargin = originalSectionsMargin;
-            newMargin.Top += headerHeight;
-            newMargin.Bottom += footerHeight;
+
+            newMargin.Top += (headerHeight ?? 0);
+            newMargin.Bottom += (footerHeight ?? 0);
 
             scrollContentContainer.Margin = newMargin;
         }

osu.Game/Graphics/Containers/UserTrackingScrollContainer.cs

@@ -0,0 +1,57 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics;
+
+namespace osu.Game.Graphics.Containers
+{
+    public class UserTrackingScrollContainer : UserTrackingScrollContainer<Drawable>
+    {
+        public UserTrackingScrollContainer()
+        {
+        }
+
+        public UserTrackingScrollContainer(Direction direction)
+            : base(direction)
+        {
+        }
+    }
+
+    public class UserTrackingScrollContainer<T> : OsuScrollContainer<T>
+        where T : Drawable
+    {
+        /// <summary>
+        /// Whether the last scroll event was user triggered, directly on the scroll container.
+        /// </summary>
+        public bool UserScrolling { get; private set; }
+
+        public void CancelUserScroll() => UserScrolling = false;
+
+        public UserTrackingScrollContainer()
+        {
+        }
+
+        public UserTrackingScrollContainer(Direction direction)
+            : base(direction)
+        {
+        }
+
+        protected override void OnUserScroll(float value, bool animated = true, double? distanceDecay = default)
+        {
+            UserScrolling = true;
+            base.OnUserScroll(value, animated, distanceDecay);
+        }
+
+        public new void ScrollTo(float value, bool animated = true, double? distanceDecay = null)
+        {
+            UserScrolling = false;
+            base.ScrollTo(value, animated, distanceDecay);
+        }
+
+        public new void ScrollToEnd(bool animated = true, bool allowDuringDrag = false)
+        {
+            UserScrolling = false;
+            base.ScrollToEnd(animated, allowDuringDrag);
+        }
+    }
+}

osu.Game/Graphics/UserInterface/DownloadButton.cs

@@ -4,54 +4,38 @@
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
-using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Game.Online;
 using osuTK;
 
 namespace osu.Game.Graphics.UserInterface
 {
-    public class DownloadButton : OsuAnimatedButton
+    public class DownloadButton : GrayButton
     {
-        public readonly Bindable<DownloadState> State = new Bindable<DownloadState>();
-
-        private readonly SpriteIcon icon;
-        private readonly SpriteIcon checkmark;
-        private readonly Box background;
-
         [Resolved]
         private OsuColour colours { get; set; }
 
+        public readonly Bindable<DownloadState> State = new Bindable<DownloadState>();
+
+        private SpriteIcon checkmark;
+
         public DownloadButton()
+            : base(FontAwesome.Solid.Download)
         {
-            Children = new Drawable[]
-            {
-                background = new Box
-                {
-                    RelativeSizeAxes = Axes.Both,
-                    Depth = float.MaxValue
-                },
-                icon = new SpriteIcon
-                {
-                    Anchor = Anchor.Centre,
-                    Origin = Anchor.Centre,
-                    Size = new Vector2(13),
-                    Icon = FontAwesome.Solid.Download,
-                },
-                checkmark = new SpriteIcon
-                {
-                    Anchor = Anchor.Centre,
-                    Origin = Anchor.Centre,
-                    X = 8,
-                    Size = Vector2.Zero,
-                    Icon = FontAwesome.Solid.Check,
-                }
-            };
         }
 
         [BackgroundDependencyLoader]
         private void load()
         {
+            AddInternal(checkmark = new SpriteIcon
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                X = 8,
+                Size = Vector2.Zero,
+                Icon = FontAwesome.Solid.Check,
+            });
+
             State.BindValueChanged(updateState, true);
         }
 
@@ -60,27 +44,27 @@ namespace osu.Game.Graphics.UserInterface
             switch (state.NewValue)
             {
                 case DownloadState.NotDownloaded:
-                    background.FadeColour(colours.Gray4, 500, Easing.InOutExpo);
-                    icon.MoveToX(0, 500, Easing.InOutExpo);
+                    Background.FadeColour(colours.Gray4, 500, Easing.InOutExpo);
+                    Icon.MoveToX(0, 500, Easing.InOutExpo);
                     checkmark.ScaleTo(Vector2.Zero, 500, Easing.InOutExpo);
                     TooltipText = "Download";
                     break;
 
                 case DownloadState.Downloading:
-                    background.FadeColour(colours.Blue, 500, Easing.InOutExpo);
-                    icon.MoveToX(0, 500, Easing.InOutExpo);
+                    Background.FadeColour(colours.Blue, 500, Easing.InOutExpo);
+                    Icon.MoveToX(0, 500, Easing.InOutExpo);
                     checkmark.ScaleTo(Vector2.Zero, 500, Easing.InOutExpo);
                     TooltipText = "Downloading...";
                     break;
 
                 case DownloadState.Importing:
-                    background.FadeColour(colours.Yellow, 500, Easing.InOutExpo);
+                    Background.FadeColour(colours.Yellow, 500, Easing.InOutExpo);
                     TooltipText = "Importing";
                     break;
 
                 case DownloadState.LocallyAvailable:
-                    background.FadeColour(colours.Green, 500, Easing.InOutExpo);
-                    icon.MoveToX(-8, 500, Easing.InOutExpo);
+                    Background.FadeColour(colours.Green, 500, Easing.InOutExpo);
+                    Icon.MoveToX(-8, 500, Easing.InOutExpo);
                     checkmark.ScaleTo(new Vector2(13), 500, Easing.InOutExpo);
                     break;
             }

osu.Game/Graphics/UserInterface/GrayButton.cs

@@ -0,0 +1,48 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Shapes;
+using osu.Framework.Graphics.Sprites;
+using osuTK;
+
+namespace osu.Game.Graphics.UserInterface
+{
+    public class GrayButton : OsuAnimatedButton
+    {
+        protected SpriteIcon Icon { get; private set; }
+        protected Box Background { get; private set; }
+
+        private readonly IconUsage icon;
+
+        [Resolved]
+        private OsuColour colours { get; set; }
+
+        public GrayButton(IconUsage icon)
+        {
+            this.icon = icon;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            Children = new Drawable[]
+            {
+                Background = new Box
+                {
+                    Colour = colours.Gray4,
+                    RelativeSizeAxes = Axes.Both,
+                    Depth = float.MaxValue
+                },
+                Icon = new SpriteIcon
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                    Size = new Vector2(13),
+                    Icon = icon,
+                },
+            };
+        }
+    }
+}

osu.Game/Graphics/UserInterface/Nub.cs

@@ -42,13 +42,7 @@ namespace osu.Game.Graphics.UserInterface
                 },
             };
 
-            Current.ValueChanged += filled =>
-            {
-                if (filled.NewValue)
-                    fill.FadeIn(200, Easing.OutQuint);
-                else
-                    fill.FadeTo(0.01f, 200, Easing.OutQuint); //todo: remove once we figure why containers aren't drawing at all times
-            };
+            Current.ValueChanged += filled => fill.FadeTo(filled.NewValue ? 1 : 0, 200, Easing.OutQuint);
         }
 
         [BackgroundDependencyLoader]

osu.Game/Graphics/UserInterface/OsuCheckbox.cs

@@ -5,6 +5,7 @@ using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Audio.Sample;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
 using osu.Framework.Graphics.UserInterface;
 using osu.Framework.Input.Events;
 using osu.Game.Graphics.Containers;
@@ -18,6 +19,11 @@ namespace osu.Game.Graphics.UserInterface
         public Color4 UncheckedColor { get; set; } = Color4.White;
         public int FadeDuration { get; set; }
 
+        /// <summary>
+        /// Whether to play sounds when the state changes as a result of user interaction.
+        /// </summary>
+        protected virtual bool PlaySoundsOnUserChange => true;
+
         public string LabelText
         {
             set
@@ -43,7 +49,7 @@ namespace osu.Game.Graphics.UserInterface
         private SampleChannel sampleChecked;
         private SampleChannel sampleUnchecked;
 
-        public OsuCheckbox()
+        public OsuCheckbox(bool nubOnRight = true)
         {
             AutoSizeAxes = Axes.Y;
             RelativeSizeAxes = Axes.X;
@@ -52,26 +58,42 @@ namespace osu.Game.Graphics.UserInterface
 
             Children = new Drawable[]
             {
-                labelText = new OsuTextFlowContainer
+                labelText = new OsuTextFlowContainer(ApplyLabelParameters)
                 {
                     AutoSizeAxes = Axes.Y,
                     RelativeSizeAxes = Axes.X,
-                    Padding = new MarginPadding { Right = Nub.EXPANDED_SIZE + nub_padding }
-                },
-                Nub = new Nub
-                {
-                    Anchor = Anchor.CentreRight,
-                    Origin = Anchor.CentreRight,
-                    Margin = new MarginPadding { Right = nub_padding },
                 },
+                Nub = new Nub(),
                 new HoverClickSounds()
             };
 
+            if (nubOnRight)
+            {
+                Nub.Anchor = Anchor.CentreRight;
+                Nub.Origin = Anchor.CentreRight;
+                Nub.Margin = new MarginPadding { Right = nub_padding };
+                labelText.Padding = new MarginPadding { Right = Nub.EXPANDED_SIZE + nub_padding * 2 };
+            }
+            else
+            {
+                Nub.Anchor = Anchor.CentreLeft;
+                Nub.Origin = Anchor.CentreLeft;
+                Nub.Margin = new MarginPadding { Left = nub_padding };
+                labelText.Padding = new MarginPadding { Left = Nub.EXPANDED_SIZE + nub_padding * 2 };
+            }
+
             Nub.Current.BindTo(Current);
 
             Current.DisabledChanged += disabled => labelText.Alpha = Nub.Alpha = disabled ? 0.3f : 1;
         }
 
+        /// <summary>
+        /// A function which can be overridden to change the parameters of the label's text.
+        /// </summary>
+        protected virtual void ApplyLabelParameters(SpriteText text)
+        {
+        }
+
         [BackgroundDependencyLoader]
         private void load(AudioManager audio)
         {
@@ -96,10 +118,14 @@ namespace osu.Game.Graphics.UserInterface
         protected override void OnUserChange(bool value)
         {
             base.OnUserChange(value);
-            if (value)
-                sampleChecked?.Play();
-            else
-                sampleUnchecked?.Play();
+
+            if (PlaySoundsOnUserChange)
+            {
+                if (value)
+                    sampleChecked?.Play();
+                else
+                    sampleUnchecked?.Play();
+            }
         }
     }
 }

osu.Game/Online/API/APIDownloadRequest.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using System.IO;
 using osu.Framework.IO.Network;
 
@@ -28,13 +29,19 @@ namespace osu.Game.Online.API
 
         private void request_Progress(long current, long total) => API.Schedule(() => Progressed?.Invoke(current, total));
 
-        protected APIDownloadRequest()
+        protected void TriggerSuccess(string filename)
         {
-            base.Success += onSuccess;
+            if (this.filename != null)
+                throw new InvalidOperationException("Attempted to trigger success more than once");
+
+            this.filename = filename;
+
+            TriggerSuccess();
         }
 
-        private void onSuccess()
+        internal override void TriggerSuccess()
         {
+            base.TriggerSuccess();
             Success?.Invoke(filename);
         }
 

osu.Game/Online/API/APIMod.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using Humanizer;
+using MessagePack;
 using Newtonsoft.Json;
 using osu.Framework.Bindables;
 using osu.Game.Configuration;
@@ -13,16 +14,21 @@ using osu.Game.Rulesets.Mods;
 
 namespace osu.Game.Online.API
 {
+    [MessagePackObject]
     public class APIMod : IMod
     {
         [JsonProperty("acronym")]
+        [Key(0)]
         public string Acronym { get; set; }
 
         [JsonProperty("settings")]
+        [Key(1)]
+        [MessagePackFormatter(typeof(ModSettingsDictionaryFormatter))]
         public Dictionary<string, object> Settings { get; set; } = new Dictionary<string, object>();
 
         [JsonConstructor]
-        private APIMod()
+        [SerializationConstructor]
+        public APIMod()
         {
         }
 

osu.Game/Online/API/ArchiveDownloadRequest.cs

@@ -10,7 +10,7 @@ namespace osu.Game.Online.API
     {
         public readonly TModel Model;
 
-        public float Progress;
+        public float Progress { get; private set; }
 
         public event Action<float> DownloadProgressed;
 
@@ -18,7 +18,13 @@ namespace osu.Game.Online.API
         {
             Model = model;
 
-            Progressed += (current, total) => DownloadProgressed?.Invoke(Progress = (float)current / total);
+            Progressed += (current, total) => SetProgress((float)current / total);
+        }
+
+        protected void SetProgress(float progress)
+        {
+            Progress = progress;
+            DownloadProgressed?.Invoke(progress);
         }
     }
 }

osu.Game/Online/API/ModSettingsDictionaryFormatter.cs

@@ -0,0 +1,67 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Buffers;
+using System.Collections.Generic;
+using System.Text;
+using MessagePack;
+using MessagePack.Formatters;
+using osu.Framework.Bindables;
+
+namespace osu.Game.Online.API
+{
+    public class ModSettingsDictionaryFormatter : IMessagePackFormatter<Dictionary<string, object>>
+    {
+        public void Serialize(ref MessagePackWriter writer, Dictionary<string, object> value, MessagePackSerializerOptions options)
+        {
+            var primitiveFormatter = PrimitiveObjectFormatter.Instance;
+
+            writer.WriteArrayHeader(value.Count);
+
+            foreach (var kvp in value)
+            {
+                var stringBytes = new ReadOnlySequence<byte>(Encoding.UTF8.GetBytes(kvp.Key));
+                writer.WriteString(in stringBytes);
+
+                switch (kvp.Value)
+                {
+                    case Bindable<double> d:
+                        primitiveFormatter.Serialize(ref writer, d.Value, options);
+                        break;
+
+                    case Bindable<int> i:
+                        primitiveFormatter.Serialize(ref writer, i.Value, options);
+                        break;
+
+                    case Bindable<float> f:
+                        primitiveFormatter.Serialize(ref writer, f.Value, options);
+                        break;
+
+                    case Bindable<bool> b:
+                        primitiveFormatter.Serialize(ref writer, b.Value, options);
+                        break;
+
+                    default:
+                        // fall back for non-bindable cases.
+                        primitiveFormatter.Serialize(ref writer, kvp.Value, options);
+                        break;
+                }
+            }
+        }
+
+        public Dictionary<string, object> Deserialize(ref MessagePackReader reader, MessagePackSerializerOptions options)
+        {
+            var output = new Dictionary<string, object>();
+
+            int itemCount = reader.ReadArrayHeader();
+
+            for (int i = 0; i < itemCount; i++)
+            {
+                output[reader.ReadString()] =
+                    PrimitiveObjectFormatter.Instance.Deserialize(ref reader, options);
+            }
+
+            return output;
+        }
+    }
+}

osu.Game/Online/API/Requests/Responses/APIBeatmapSet.cs

@@ -81,7 +81,7 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty(@"beatmaps")]
         private IEnumerable<APIBeatmap> beatmaps { get; set; }
 
-        public BeatmapSetInfo ToBeatmapSet(RulesetStore rulesets)
+        public virtual BeatmapSetInfo ToBeatmapSet(RulesetStore rulesets)
         {
             var beatmapSet = new BeatmapSetInfo
             {

osu.Game/Online/Chat/ChannelManager.cs

@@ -339,7 +339,7 @@ namespace osu.Game.Online.Chat
         }
 
         /// <summary>
-        /// Joins a channel if it has not already been joined.
+        /// Joins a channel if it has not already been joined. Must be called from the update thread.
         /// </summary>
         /// <param name="channel">The channel to join.</param>
         /// <returns>The joined channel. Note that this may not match the parameter channel as it is a backed object.</returns>
@@ -399,7 +399,11 @@ namespace osu.Game.Online.Chat
             return channel;
         }
 
-        public void LeaveChannel(Channel channel)
+        /// <summary>
+        /// Leave the specified channel. Can be called from any thread.
+        /// </summary>
+        /// <param name="channel">The channel to leave.</param>
+        public void LeaveChannel(Channel channel) => Schedule(() =>
         {
             if (channel == null) return;
 
@@ -413,7 +417,7 @@ namespace osu.Game.Online.Chat
                 api.Queue(new LeaveChannelRequest(channel));
                 channel.Joined.Value = false;
             }
-        }
+        });
 
         private long lastMessageId;
 

osu.Game/Online/DownloadTrackingComposite.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics.Containers;
@@ -20,7 +21,7 @@ namespace osu.Game.Online
         protected readonly Bindable<TModel> Model = new Bindable<TModel>();
 
         [Resolved(CanBeNull = true)]
-        private TModelManager manager { get; set; }
+        protected TModelManager Manager { get; private set; }
 
         /// <summary>
         /// Holds the current download state of the <typeparamref name="TModel"/>, whether is has already been downloaded, is in progress, or is not downloaded.
@@ -46,25 +47,41 @@ namespace osu.Game.Online
             {
                 if (modelInfo.NewValue == null)
                     attachDownload(null);
-                else if (manager?.IsAvailableLocally(modelInfo.NewValue) == true)
+                else if (IsModelAvailableLocally())
                     State.Value = DownloadState.LocallyAvailable;
                 else
-                    attachDownload(manager?.GetExistingDownload(modelInfo.NewValue));
+                    attachDownload(Manager?.GetExistingDownload(modelInfo.NewValue));
             }, true);
 
-            if (manager == null)
+            if (Manager == null)
                 return;
 
-            managerDownloadBegan = manager.DownloadBegan.GetBoundCopy();
+            managerDownloadBegan = Manager.DownloadBegan.GetBoundCopy();
             managerDownloadBegan.BindValueChanged(downloadBegan);
-            managerDownloadFailed = manager.DownloadFailed.GetBoundCopy();
+            managerDownloadFailed = Manager.DownloadFailed.GetBoundCopy();
             managerDownloadFailed.BindValueChanged(downloadFailed);
-            managedUpdated = manager.ItemUpdated.GetBoundCopy();
+            managedUpdated = Manager.ItemUpdated.GetBoundCopy();
             managedUpdated.BindValueChanged(itemUpdated);
-            managerRemoved = manager.ItemRemoved.GetBoundCopy();
+            managerRemoved = Manager.ItemRemoved.GetBoundCopy();
             managerRemoved.BindValueChanged(itemRemoved);
         }
 
+        /// <summary>
+        /// Checks that a database model matches the one expected to be downloaded.
+        /// </summary>
+        /// <example>
+        /// For online play, this could be used to check that the databased model matches the online beatmap.
+        /// </example>
+        /// <param name="databasedModel">The model in database.</param>
+        protected virtual bool VerifyDatabasedModel([NotNull] TModel databasedModel) => true;
+
+        /// <summary>
+        /// Whether the given model is available in the database.
+        /// By default, this calls <see cref="IModelDownloader{TModel}.IsAvailableLocally"/>,
+        /// but can be overriden to add additional checks for verifying the model in database.
+        /// </summary>
+        protected virtual bool IsModelAvailableLocally() => Manager?.IsAvailableLocally(Model.Value) == true;
+
         private void downloadBegan(ValueChangedEvent<WeakReference<ArchiveDownloadRequest<TModel>>> weakRequest)
         {
             if (weakRequest.NewValue.TryGetTarget(out var request))
@@ -134,23 +151,35 @@ namespace osu.Game.Online
         private void itemUpdated(ValueChangedEvent<WeakReference<TModel>> weakItem)
         {
             if (weakItem.NewValue.TryGetTarget(out var item))
-                setDownloadStateFromManager(item, DownloadState.LocallyAvailable);
+            {
+                Schedule(() =>
+                {
+                    if (!item.Equals(Model.Value))
+                        return;
+
+                    if (!VerifyDatabasedModel(item))
+                    {
+                        State.Value = DownloadState.NotDownloaded;
+                        return;
+                    }
+
+                    State.Value = DownloadState.LocallyAvailable;
+                });
+            }
         }
 
         private void itemRemoved(ValueChangedEvent<WeakReference<TModel>> weakItem)
         {
             if (weakItem.NewValue.TryGetTarget(out var item))
-                setDownloadStateFromManager(item, DownloadState.NotDownloaded);
+            {
+                Schedule(() =>
+                {
+                    if (item.Equals(Model.Value))
+                        State.Value = DownloadState.NotDownloaded;
+                });
+            }
         }
 
-        private void setDownloadStateFromManager(TModel s, DownloadState state) => Schedule(() =>
-        {
-            if (!s.Equals(Model.Value))
-                return;
-
-            State.Value = state;
-        });
-
         #region Disposal
 
         protected override void Dispose(bool isDisposing)

osu.Game/Online/Multiplayer/IMultiplayerClient.cs

@@ -1,7 +1,9 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Collections.Generic;
 using System.Threading.Tasks;
+using osu.Game.Online.API;
 using osu.Game.Online.Rooms;
 
 namespace osu.Game.Online.Multiplayer
@@ -55,6 +57,13 @@ namespace osu.Game.Online.Multiplayer
         /// <param name="beatmapAvailability">The new beatmap availability state of the user.</param>
         Task UserBeatmapAvailabilityChanged(int userId, BeatmapAvailability beatmapAvailability);
 
+        /// <summary>
+        /// Signals that a user in this room changed their local mods.
+        /// </summary>
+        /// <param name="userId">The ID of the user whose mods have changed.</param>
+        /// <param name="mods">The user's new local mods.</param>
+        Task UserModsChanged(int userId, IEnumerable<APIMod> mods);
+
         /// <summary>
         /// Signals that a match is to be started. This will *only* be sent to clients which are to begin loading at this point.
         /// </summary>

osu.Game/Online/Multiplayer/IMultiplayerRoomServer.cs

@@ -1,7 +1,9 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Collections.Generic;
 using System.Threading.Tasks;
+using osu.Game.Online.API;
 using osu.Game.Online.Rooms;
 
 namespace osu.Game.Online.Multiplayer
@@ -47,6 +49,12 @@ namespace osu.Game.Online.Multiplayer
         /// <param name="newBeatmapAvailability">The proposed new beatmap availability state.</param>
         Task ChangeBeatmapAvailability(BeatmapAvailability newBeatmapAvailability);
 
+        /// <summary>
+        /// Change the local user's mods in the currently joined room.
+        /// </summary>
+        /// <param name="newMods">The proposed new mods, excluding any required by the room itself.</param>
+        Task ChangeUserMods(IEnumerable<APIMod> newMods);
+
         /// <summary>
         /// As the host of a room, start the match.
         /// </summary>

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -4,12 +4,14 @@
 #nullable enable
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.SignalR.Client;
 using Microsoft.Extensions.DependencyInjection;
 using Newtonsoft.Json;
+using osu.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Logging;
@@ -65,13 +67,19 @@ namespace osu.Game.Online.Multiplayer
             if (connection != null)
                 return;
 
-            connection = new HubConnectionBuilder()
-                         .WithUrl(endpoint, options =>
-                         {
-                             options.Headers.Add("Authorization", $"Bearer {api.AccessToken}");
-                         })
-                         .AddNewtonsoftJsonProtocol(options => { options.PayloadSerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore; })
-                         .Build();
+            var builder = new HubConnectionBuilder()
+                .WithUrl(endpoint, options => { options.Headers.Add("Authorization", $"Bearer {api.AccessToken}"); });
+
+            if (RuntimeInfo.SupportsJIT)
+                builder.AddMessagePackProtocol();
+            else
+            {
+                // eventually we will precompile resolvers for messagepack, but this isn't working currently
+                // see https://github.com/neuecc/MessagePack-CSharp/issues/780#issuecomment-768794308.
+                builder.AddNewtonsoftJsonProtocol(options => { options.PayloadSerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore; });
+            }
+
+            connection = builder.Build();
 
             // this is kind of SILLY
             // https://github.com/dotnet/aspnetcore/issues/15198
@@ -84,6 +92,7 @@ namespace osu.Game.Online.Multiplayer
             connection.On(nameof(IMultiplayerClient.LoadRequested), ((IMultiplayerClient)this).LoadRequested);
             connection.On(nameof(IMultiplayerClient.MatchStarted), ((IMultiplayerClient)this).MatchStarted);
             connection.On(nameof(IMultiplayerClient.ResultsReady), ((IMultiplayerClient)this).ResultsReady);
+            connection.On<int, IEnumerable<APIMod>>(nameof(IMultiplayerClient.UserModsChanged), ((IMultiplayerClient)this).UserModsChanged);
 
             connection.Closed += async ex =>
             {
@@ -182,6 +191,14 @@ namespace osu.Game.Online.Multiplayer
             return connection.InvokeAsync(nameof(IMultiplayerServer.ChangeBeatmapAvailability), newBeatmapAvailability);
         }
 
+        public override Task ChangeUserMods(IEnumerable<APIMod> newMods)
+        {
+            if (!isConnected.Value)
+                return Task.CompletedTask;
+
+            return connection.InvokeAsync(nameof(IMultiplayerServer.ChangeUserMods), newMods);
+        }
+
         public override Task StartMatch()
         {
             if (!isConnected.Value)

osu.Game/Online/Multiplayer/MultiplayerRoom.cs

@@ -5,6 +5,7 @@
 
 using System;
 using System.Collections.Generic;
+using MessagePack;
 using Newtonsoft.Json;
 
 namespace osu.Game.Online.Multiplayer
@@ -13,35 +14,42 @@ namespace osu.Game.Online.Multiplayer
     /// A multiplayer room.
     /// </summary>
     [Serializable]
+    [MessagePackObject]
     public class MultiplayerRoom
     {
         /// <summary>
         /// The ID of the room, used for database persistence.
         /// </summary>
+        [Key(0)]
         public readonly long RoomID;
 
         /// <summary>
         /// The current state of the room (ie. whether it is in progress or otherwise).
         /// </summary>
+        [Key(1)]
         public MultiplayerRoomState State { get; set; }
 
         /// <summary>
         /// All currently enforced game settings for this room.
         /// </summary>
+        [Key(2)]
         public MultiplayerRoomSettings Settings { get; set; } = new MultiplayerRoomSettings();
 
         /// <summary>
         /// All users currently in this room.
         /// </summary>
+        [Key(3)]
         public List<MultiplayerRoomUser> Users { get; set; } = new List<MultiplayerRoomUser>();
 
         /// <summary>
         /// The host of this room, in control of changing room settings.
         /// </summary>
+        [Key(4)]
         public MultiplayerRoomUser? Host { get; set; }
 
         [JsonConstructor]
-        public MultiplayerRoom(in long roomId)
+        [SerializationConstructor]
+        public MultiplayerRoom(long roomId)
         {
             RoomID = roomId;
         }

osu.Game/Online/Multiplayer/MultiplayerRoomSettings.cs

@@ -7,31 +7,47 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using JetBrains.Annotations;
+using MessagePack;
 using osu.Game.Online.API;
 
 namespace osu.Game.Online.Multiplayer
 {
     [Serializable]
+    [MessagePackObject]
     public class MultiplayerRoomSettings : IEquatable<MultiplayerRoomSettings>
     {
+        [Key(0)]
         public int BeatmapID { get; set; }
 
+        [Key(1)]
         public int RulesetID { get; set; }
 
+        [Key(2)]
         public string BeatmapChecksum { get; set; } = string.Empty;
 
+        [Key(3)]
         public string Name { get; set; } = "Unnamed room";
 
         [NotNull]
-        public IEnumerable<APIMod> Mods { get; set; } = Enumerable.Empty<APIMod>();
+        [Key(4)]
+        public IEnumerable<APIMod> RequiredMods { get; set; } = Enumerable.Empty<APIMod>();
+
+        [NotNull]
+        [Key(5)]
+        public IEnumerable<APIMod> AllowedMods { get; set; } = Enumerable.Empty<APIMod>();
 
         public bool Equals(MultiplayerRoomSettings other)
             => BeatmapID == other.BeatmapID
                && BeatmapChecksum == other.BeatmapChecksum
-               && Mods.SequenceEqual(other.Mods)
+               && RequiredMods.SequenceEqual(other.RequiredMods)
+               && AllowedMods.SequenceEqual(other.AllowedMods)
                && RulesetID == other.RulesetID
                && Name.Equals(other.Name, StringComparison.Ordinal);
 
-        public override string ToString() => $"Name:{Name} Beatmap:{BeatmapID} ({BeatmapChecksum}) Mods:{string.Join(',', Mods)} Ruleset:{RulesetID}";
+        public override string ToString() => $"Name:{Name}"
+                                             + $" Beatmap:{BeatmapID} ({BeatmapChecksum})"
+                                             + $" RequiredMods:{string.Join(',', RequiredMods)}"
+                                             + $" AllowedMods:{string.Join(',', AllowedMods)}"
+                                             + $" Ruleset:{RulesetID}";
     }
 }

osu.Game/Online/Multiplayer/MultiplayerRoomUser.cs

@@ -4,28 +4,45 @@
 #nullable enable
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
+using JetBrains.Annotations;
+using MessagePack;
 using Newtonsoft.Json;
+using osu.Game.Online.API;
 using osu.Game.Online.Rooms;
 using osu.Game.Users;
 
 namespace osu.Game.Online.Multiplayer
 {
     [Serializable]
+    [MessagePackObject]
     public class MultiplayerRoomUser : IEquatable<MultiplayerRoomUser>
     {
+        [Key(0)]
         public readonly int UserID;
 
+        [Key(1)]
         public MultiplayerUserState State { get; set; } = MultiplayerUserState.Idle;
 
         /// <summary>
         /// The availability state of the current beatmap.
         /// </summary>
+        [Key(2)]
         public BeatmapAvailability BeatmapAvailability { get; set; } = BeatmapAvailability.LocallyAvailable();
 
+        /// <summary>
+        /// Any mods applicable only to the local user.
+        /// </summary>
+        [Key(3)]
+        [NotNull]
+        public IEnumerable<APIMod> Mods { get; set; } = Enumerable.Empty<APIMod>();
+
+        [IgnoreMember]
         public User? User { get; set; }
 
         [JsonConstructor]
-        public MultiplayerRoomUser(in int userId)
+        public MultiplayerRoomUser(int userId)
         {
             UserID = userId;
         }

osu.Game/Online/Multiplayer/StatefulMultiplayerClient.cs

@@ -15,13 +15,13 @@ using osu.Framework.Graphics;
 using osu.Framework.Logging;
 using osu.Game.Beatmaps;
 using osu.Game.Database;
-using osu.Game.Extensions;
 using osu.Game.Online.API;
 using osu.Game.Online.API.Requests;
 using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Online.Rooms;
 using osu.Game.Online.Rooms.RoomStatuses;
 using osu.Game.Rulesets;
+using osu.Game.Rulesets.Mods;
 using osu.Game.Users;
 using osu.Game.Utils;
 
@@ -104,7 +104,7 @@ namespace osu.Game.Online.Multiplayer
                 if (!connected.NewValue && Room != null)
                 {
                     Logger.Log("Connection to multiplayer server was lost.", LoggingTarget.Runtime, LogLevel.Important);
-                    LeaveRoom().CatchUnobservedExceptions();
+                    LeaveRoom();
                 }
             });
         }
@@ -192,7 +192,8 @@ namespace osu.Game.Online.Multiplayer
                 BeatmapID = item.GetOr(existingPlaylistItem).BeatmapID,
                 BeatmapChecksum = item.GetOr(existingPlaylistItem).Beatmap.Value.MD5Hash,
                 RulesetID = item.GetOr(existingPlaylistItem).RulesetID,
-                Mods = item.HasValue ? item.Value.AsNonNull().RequiredMods.Select(m => new APIMod(m)).ToList() : Room.Settings.Mods
+                RequiredMods = item.HasValue ? item.Value.AsNonNull().RequiredMods.Select(m => new APIMod(m)).ToList() : Room.Settings.RequiredMods,
+                AllowedMods = item.HasValue ? item.Value.AsNonNull().AllowedMods.Select(m => new APIMod(m)).ToList() : Room.Settings.AllowedMods
             });
         }
 
@@ -230,6 +231,14 @@ namespace osu.Game.Online.Multiplayer
 
         public abstract Task ChangeBeatmapAvailability(BeatmapAvailability newBeatmapAvailability);
 
+        /// <summary>
+        /// Change the local user's mods in the currently joined room.
+        /// </summary>
+        /// <param name="newMods">The proposed new mods, excluding any required by the room itself.</param>
+        public Task ChangeUserMods(IEnumerable<Mod> newMods) => ChangeUserMods(newMods.Select(m => new APIMod(m)).ToList());
+
+        public abstract Task ChangeUserMods(IEnumerable<APIMod> newMods);
+
         public abstract Task StartMatch();
 
         Task IMultiplayerClient.RoomStateChanged(MultiplayerRoomState state)
@@ -378,6 +387,27 @@ namespace osu.Game.Online.Multiplayer
             return Task.CompletedTask;
         }
 
+        public Task UserModsChanged(int userId, IEnumerable<APIMod> mods)
+        {
+            if (Room == null)
+                return Task.CompletedTask;
+
+            Scheduler.Add(() =>
+            {
+                var user = Room?.Users.SingleOrDefault(u => u.UserID == userId);
+
+                // errors here are not critical - user mods are mostly for display.
+                if (user == null)
+                    return;
+
+                user.Mods = mods;
+
+                RoomUpdated?.Invoke();
+            }, false);
+
+            return Task.CompletedTask;
+        }
+
         Task IMultiplayerClient.LoadRequested()
         {
             if (Room == null)
@@ -501,7 +531,8 @@ namespace osu.Game.Online.Multiplayer
             beatmap.MD5Hash = settings.BeatmapChecksum;
 
             var ruleset = rulesets.GetRuleset(settings.RulesetID).CreateInstance();
-            var mods = settings.Mods.Select(m => m.ToMod(ruleset));
+            var mods = settings.RequiredMods.Select(m => m.ToMod(ruleset));
+            var allowedMods = settings.AllowedMods.Select(m => m.ToMod(ruleset));
 
             PlaylistItem playlistItem = new PlaylistItem
             {
@@ -511,6 +542,7 @@ namespace osu.Game.Online.Multiplayer
             };
 
             playlistItem.RequiredMods.AddRange(mods);
+            playlistItem.AllowedMods.AddRange(allowedMods);
 
             apiRoom.Playlist.Clear(); // Clearing should be unnecessary, but here for sanity.
             apiRoom.Playlist.Add(playlistItem);

osu.Game/Online/Rooms/BeatmapAvailability.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using MessagePack;
 using Newtonsoft.Json;
 
 namespace osu.Game.Online.Rooms
@@ -9,27 +10,30 @@ namespace osu.Game.Online.Rooms
     /// <summary>
     /// The local availability information about a certain beatmap for the client.
     /// </summary>
+    [MessagePackObject]
     public class BeatmapAvailability : IEquatable<BeatmapAvailability>
     {
         /// <summary>
         /// The beatmap's availability state.
         /// </summary>
+        [Key(0)]
         public readonly DownloadState State;
 
         /// <summary>
         /// The beatmap's downloading progress, null when not in <see cref="DownloadState.Downloading"/> state.
         /// </summary>
-        public readonly double? DownloadProgress;
+        [Key(1)]
+        public readonly float? DownloadProgress;
 
         [JsonConstructor]
-        private BeatmapAvailability(DownloadState state, double? downloadProgress = null)
+        public BeatmapAvailability(DownloadState state, float? downloadProgress = null)
         {
             State = state;
             DownloadProgress = downloadProgress;
         }
 
         public static BeatmapAvailability NotDownloaded() => new BeatmapAvailability(DownloadState.NotDownloaded);
-        public static BeatmapAvailability Downloading(double progress) => new BeatmapAvailability(DownloadState.Downloading, progress);
+        public static BeatmapAvailability Downloading(float progress) => new BeatmapAvailability(DownloadState.Downloading, progress);
         public static BeatmapAvailability Importing() => new BeatmapAvailability(DownloadState.Importing);
         public static BeatmapAvailability LocallyAvailable() => new BeatmapAvailability(DownloadState.LocallyAvailable);
 

osu.Game/Online/Rooms/OnlinePlayBeatmapAvailablilityTracker.cs

@@ -0,0 +1,92 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Linq;
+using osu.Framework.Bindables;
+using osu.Framework.Logging;
+using osu.Game.Beatmaps;
+
+namespace osu.Game.Online.Rooms
+{
+    /// <summary>
+    /// Represent a checksum-verifying beatmap availability tracker usable for online play screens.
+    ///
+    /// This differs from a regular download tracking composite as this accounts for the
+    /// databased beatmap set's checksum, to disallow from playing with an altered version of the beatmap.
+    /// </summary>
+    public class OnlinePlayBeatmapAvailablilityTracker : DownloadTrackingComposite<BeatmapSetInfo, BeatmapManager>
+    {
+        public readonly IBindable<PlaylistItem> SelectedItem = new Bindable<PlaylistItem>();
+
+        /// <summary>
+        /// The availability state of the currently selected playlist item.
+        /// </summary>
+        public IBindable<BeatmapAvailability> Availability => availability;
+
+        private readonly Bindable<BeatmapAvailability> availability = new Bindable<BeatmapAvailability>();
+
+        public OnlinePlayBeatmapAvailablilityTracker()
+        {
+            State.BindValueChanged(_ => updateAvailability());
+            Progress.BindValueChanged(_ => updateAvailability(), true);
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            SelectedItem.BindValueChanged(item => Model.Value = item.NewValue?.Beatmap.Value.BeatmapSet, true);
+        }
+
+        protected override bool VerifyDatabasedModel(BeatmapSetInfo databasedSet)
+        {
+            int? beatmapId = SelectedItem.Value.Beatmap.Value.OnlineBeatmapID;
+            string checksum = SelectedItem.Value.Beatmap.Value.MD5Hash;
+
+            var matchingBeatmap = databasedSet.Beatmaps.FirstOrDefault(b => b.OnlineBeatmapID == beatmapId && b.MD5Hash == checksum);
+
+            if (matchingBeatmap == null)
+            {
+                Logger.Log("The imported beatmap set does not match the online version.", LoggingTarget.Runtime, LogLevel.Important);
+                return false;
+            }
+
+            return true;
+        }
+
+        protected override bool IsModelAvailableLocally()
+        {
+            int? beatmapId = SelectedItem.Value.Beatmap.Value.OnlineBeatmapID;
+            string checksum = SelectedItem.Value.Beatmap.Value.MD5Hash;
+
+            var beatmap = Manager.QueryBeatmap(b => b.OnlineBeatmapID == beatmapId && b.MD5Hash == checksum);
+            return beatmap?.BeatmapSet.DeletePending == false;
+        }
+
+        private void updateAvailability()
+        {
+            switch (State.Value)
+            {
+                case DownloadState.NotDownloaded:
+                    availability.Value = BeatmapAvailability.NotDownloaded();
+                    break;
+
+                case DownloadState.Downloading:
+                    availability.Value = BeatmapAvailability.Downloading((float)Progress.Value);
+                    break;
+
+                case DownloadState.Importing:
+                    availability.Value = BeatmapAvailability.Importing();
+                    break;
+
+                case DownloadState.LocallyAvailable:
+                    availability.Value = BeatmapAvailability.LocallyAvailable();
+                    break;
+
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(State));
+            }
+        }
+    }
+}

osu.Game/Online/Spectator/FrameDataBundle.cs

@@ -5,6 +5,7 @@
 
 using System;
 using System.Collections.Generic;
+using MessagePack;
 using Newtonsoft.Json;
 using osu.Game.Replays.Legacy;
 using osu.Game.Scoring;
@@ -12,10 +13,13 @@ using osu.Game.Scoring;
 namespace osu.Game.Online.Spectator
 {
     [Serializable]
+    [MessagePackObject]
     public class FrameDataBundle
     {
+        [Key(0)]
         public FrameHeader Header { get; set; }
 
+        [Key(1)]
         public IEnumerable<LegacyReplayFrame> Frames { get; set; }
 
         public FrameDataBundle(ScoreInfo score, IEnumerable<LegacyReplayFrame> frames)

osu.Game/Online/Spectator/FrameHeader.cs

@@ -5,6 +5,7 @@
 
 using System;
 using System.Collections.Generic;
+using MessagePack;
 using Newtonsoft.Json;
 using osu.Game.Rulesets.Scoring;
 using osu.Game.Scoring;
@@ -12,31 +13,37 @@ using osu.Game.Scoring;
 namespace osu.Game.Online.Spectator
 {
     [Serializable]
+    [MessagePackObject]
     public class FrameHeader
     {
         /// <summary>
         /// The current accuracy of the score.
         /// </summary>
+        [Key(0)]
         public double Accuracy { get; set; }
 
         /// <summary>
         /// The current combo of the score.
         /// </summary>
+        [Key(1)]
         public int Combo { get; set; }
 
         /// <summary>
         /// The maximum combo achieved up to the current point in time.
         /// </summary>
+        [Key(2)]
         public int MaxCombo { get; set; }
 
         /// <summary>
         /// Cumulative hit statistics.
         /// </summary>
+        [Key(3)]
         public Dictionary<HitResult, int> Statistics { get; set; }
 
         /// <summary>
         /// The time at which this frame was received by the server.
         /// </summary>
+        [Key(4)]
         public DateTimeOffset ReceivedTime { get; set; }
 
         /// <summary>
@@ -54,7 +61,8 @@ namespace osu.Game.Online.Spectator
         }
 
         [JsonConstructor]
-        public FrameHeader(int combo, int maxCombo, double accuracy, Dictionary<HitResult, int> statistics, DateTimeOffset receivedTime)
+        [SerializationConstructor]
+        public FrameHeader(double accuracy, int combo, int maxCombo, Dictionary<HitResult, int> statistics, DateTimeOffset receivedTime)
         {
             Combo = combo;
             MaxCombo = maxCombo;

osu.Game/Online/Spectator/SpectatorState.cs

@@ -5,18 +5,23 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using MessagePack;
 using osu.Game.Online.API;
 
 namespace osu.Game.Online.Spectator
 {
     [Serializable]
+    [MessagePackObject]
     public class SpectatorState : IEquatable<SpectatorState>
     {
+        [Key(0)]
         public int? BeatmapID { get; set; }
 
+        [Key(1)]
         public int? RulesetID { get; set; }
 
         [NotNull]
+        [Key(2)]
         public IEnumerable<APIMod> Mods { get; set; } = Enumerable.Empty<APIMod>();
 
         public bool Equals(SpectatorState other) => BeatmapID == other?.BeatmapID && Mods.SequenceEqual(other?.Mods) && RulesetID == other?.RulesetID;

osu.Game/Online/Spectator/SpectatorStreamingClient.cs

@@ -10,6 +10,7 @@ using JetBrains.Annotations;
 using Microsoft.AspNetCore.SignalR.Client;
 using Microsoft.Extensions.DependencyInjection;
 using Newtonsoft.Json;
+using osu.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
@@ -116,14 +117,19 @@ namespace osu.Game.Online.Spectator
             if (connection != null)
                 return;
 
-            connection = new HubConnectionBuilder()
-                         .WithUrl(endpoint, options =>
-                         {
-                             options.Headers.Add("Authorization", $"Bearer {api.AccessToken}");
-                         })
-                         .AddNewtonsoftJsonProtocol(options => { options.PayloadSerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore; })
-                         .Build();
+            var builder = new HubConnectionBuilder()
+                .WithUrl(endpoint, options => { options.Headers.Add("Authorization", $"Bearer {api.AccessToken}"); });
 
+            if (RuntimeInfo.SupportsJIT)
+                builder.AddMessagePackProtocol();
+            else
+            {
+                // eventually we will precompile resolvers for messagepack, but this isn't working currently
+                // see https://github.com/neuecc/MessagePack-CSharp/issues/780#issuecomment-768794308.
+                builder.AddNewtonsoftJsonProtocol(options => { options.PayloadSerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore; });
+            }
+
+            connection = builder.Build();
             // until strong typed client support is added, each method must be manually bound (see https://github.com/dotnet/aspnetcore/issues/15198)
             connection.On<int, SpectatorState>(nameof(ISpectatorClient.UserBeganPlaying), ((ISpectatorClient)this).UserBeganPlaying);
             connection.On<int, FrameDataBundle>(nameof(ISpectatorClient.UserSentFrames), ((ISpectatorClient)this).UserSentFrames);

osu.Game/OsuGame.cs

@@ -468,6 +468,16 @@ namespace osu.Game
         private void modsChanged(ValueChangedEvent<IReadOnlyList<Mod>> mods)
         {
             updateModDefaults();
+
+            // a lease may be taken on the mods bindable, at which point we can't really ensure valid mods.
+            if (SelectedMods.Disabled)
+                return;
+
+            if (!ModUtils.CheckValidForGameplay(mods.NewValue, out var invalid))
+            {
+                // ensure we always have a valid set of mods.
+                SelectedMods.Value = mods.NewValue.Except(invalid).ToArray();
+            }
         }
 
         private void updateModDefaults()

osu.Game/Overlays/BeatmapListing/BeatmapSearchFilterRow.cs

@@ -12,7 +12,7 @@ using osu.Game.Graphics.Sprites;
 using osu.Game.Graphics.UserInterface;
 using osuTK;
 using Humanizer;
-using osu.Game.Utils;
+using osu.Framework.Extensions.EnumExtensions;
 
 namespace osu.Game.Overlays.BeatmapListing
 {
@@ -80,7 +80,7 @@ namespace osu.Game.Overlays.BeatmapListing
 
                 if (typeof(T).IsEnum)
                 {
-                    foreach (var val in OrderAttributeUtils.GetValuesInOrder<T>())
+                    foreach (var val in EnumExtensions.GetValuesInOrder<T>())
                         AddItem(val);
                 }
             }

osu.Game/Overlays/BeatmapListing/SearchLanguage.cs

@@ -1,7 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using osu.Game.Utils;
+using osu.Framework.Utils;
 
 namespace osu.Game.Overlays.BeatmapListing
 {

osu.Game/Overlays/BeatmapListingOverlay.cs

@@ -176,23 +176,34 @@ namespace osu.Game.Overlays
             loadingLayer.Hide();
             lastFetchDisplayedTime = Time.Current;
 
+            if (content == currentContent)
+                return;
+
             var lastContent = currentContent;
 
             if (lastContent != null)
             {
-                lastContent.FadeOut(100, Easing.OutQuint).Expire();
+                var transform = lastContent.FadeOut(100, Easing.OutQuint);
 
-                // Consider the case when the new content is smaller than the last content.
-                // If the auto-size computation is delayed until fade out completes, the background remain high for too long making the resulting transition to the smaller height look weird.
-                // At the same time, if the last content's height is bypassed immediately, there is a period where the new content is at Alpha = 0 when the auto-sized height will be 0.
-                // To resolve both of these issues, the bypass is delayed until a point when the content transitions (fade-in and fade-out) overlap and it looks good to do so.
-                lastContent.Delay(25).Schedule(() => lastContent.BypassAutoSizeAxes = Axes.Y).Then().Schedule(() => panelTarget.Remove(lastContent));
+                if (lastContent == notFoundContent)
+                {
+                    // not found display may be used multiple times, so don't expire/dispose it.
+                    transform.Schedule(() => panelTarget.Remove(lastContent));
+                }
+                else
+                {
+                    // Consider the case when the new content is smaller than the last content.
+                    // If the auto-size computation is delayed until fade out completes, the background remain high for too long making the resulting transition to the smaller height look weird.
+                    // At the same time, if the last content's height is bypassed immediately, there is a period where the new content is at Alpha = 0 when the auto-sized height will be 0.
+                    // To resolve both of these issues, the bypass is delayed until a point when the content transitions (fade-in and fade-out) overlap and it looks good to do so.
+                    lastContent.Delay(25).Schedule(() => lastContent.BypassAutoSizeAxes = Axes.Y).Then().Schedule(() => lastContent.Expire());
+                }
             }
 
             if (!content.IsAlive)
                 panelTarget.Add(content);
-            content.FadeIn(200, Easing.OutQuint);
 
+            content.FadeInFromZero(200, Easing.OutQuint);
             currentContent = content;
         }
 
@@ -202,7 +213,7 @@ namespace osu.Game.Overlays
             base.Dispose(isDisposing);
         }
 
-        private class NotFoundDrawable : CompositeDrawable
+        public class NotFoundDrawable : CompositeDrawable
         {
             public NotFoundDrawable()
             {

osu.Game/Overlays/BeatmapSet/BeatmapSetHeader.cs

@@ -1,25 +1,55 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using osu.Framework.Allocation;
 using osu.Framework.Bindables;
+using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Effects;
+using osu.Game.Beatmaps;
 using osu.Game.Rulesets;
+using osuTK;
+using osuTK.Graphics;
 
 namespace osu.Game.Overlays.BeatmapSet
 {
     public class BeatmapSetHeader : OverlayHeader
     {
-        public readonly Bindable<RulesetInfo> Ruleset = new Bindable<RulesetInfo>();
+        public readonly Bindable<BeatmapSetInfo> BeatmapSet = new Bindable<BeatmapSetInfo>();
 
+        public BeatmapSetHeaderContent HeaderContent { get; private set; }
+
+        [Cached]
         public BeatmapRulesetSelector RulesetSelector { get; private set; }
 
-        protected override OverlayTitle CreateTitle() => new BeatmapHeaderTitle();
+        [Cached(typeof(IBindable<RulesetInfo>))]
+        private readonly Bindable<RulesetInfo> ruleset = new Bindable<RulesetInfo>();
+
+        public BeatmapSetHeader()
+        {
+            Masking = true;
+
+            EdgeEffect = new EdgeEffectParameters
+            {
+                Colour = Color4.Black.Opacity(0.25f),
+                Type = EdgeEffectType.Shadow,
+                Radius = 3,
+                Offset = new Vector2(0f, 1f),
+            };
+        }
+
+        protected override Drawable CreateContent() => HeaderContent = new BeatmapSetHeaderContent
+        {
+            BeatmapSet = { BindTarget = BeatmapSet }
+        };
 
         protected override Drawable CreateTitleContent() => RulesetSelector = new BeatmapRulesetSelector
         {
-            Current = Ruleset
+            Current = ruleset
         };
 
+        protected override OverlayTitle CreateTitle() => new BeatmapHeaderTitle();
+
         private class BeatmapHeaderTitle : OverlayTitle
         {
             public BeatmapHeaderTitle()

osu.Game/Overlays/BeatmapSet/BeatmapSetHeaderContent.cs

@@ -3,12 +3,10 @@
 
 using System.Linq;
 using osu.Framework.Allocation;
-using osu.Framework.Bindables;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Colour;
 using osu.Framework.Graphics.Containers;
-using osu.Framework.Graphics.Effects;
 using osu.Framework.Graphics.Shapes;
 using osu.Game.Beatmaps.Drawables;
 using osu.Game.Graphics;
@@ -18,18 +16,21 @@ using osu.Game.Online;
 using osu.Game.Online.API;
 using osu.Game.Overlays.BeatmapListing.Panels;
 using osu.Game.Overlays.BeatmapSet.Buttons;
-using osu.Game.Rulesets;
 using osuTK;
-using osuTK.Graphics;
 
 namespace osu.Game.Overlays.BeatmapSet
 {
-    public class Header : BeatmapDownloadTrackingComposite
+    public class BeatmapSetHeaderContent : BeatmapDownloadTrackingComposite
     {
         private const float transition_duration = 200;
         private const float buttons_height = 45;
         private const float buttons_spacing = 5;
 
+        public bool DownloadButtonsVisible => downloadButtonsContainer.Any();
+
+        public readonly Details Details;
+        public readonly BeatmapPicker Picker;
+
         private readonly UpdateableBeatmapSetCover cover;
         private readonly Box coverGradient;
         private readonly OsuSpriteText title, artist;
@@ -38,185 +39,154 @@ namespace osu.Game.Overlays.BeatmapSet
         private readonly FillFlowContainer downloadButtonsContainer;
         private readonly BeatmapAvailability beatmapAvailability;
         private readonly BeatmapSetOnlineStatusPill onlineStatusPill;
-        public Details Details;
-
-        public bool DownloadButtonsVisible => downloadButtonsContainer.Any();
+        private readonly FavouriteButton favouriteButton;
+        private readonly FillFlowContainer fadeContent;
+        private readonly LoadingSpinner loading;
 
         [Resolved]
         private IAPIProvider api { get; set; }
 
-        public BeatmapRulesetSelector RulesetSelector => beatmapSetHeader.RulesetSelector;
-        public readonly BeatmapPicker Picker;
+        [Resolved]
+        private BeatmapRulesetSelector rulesetSelector { get; set; }
 
-        private readonly FavouriteButton favouriteButton;
-        private readonly FillFlowContainer fadeContent;
-        private readonly LoadingSpinner loading;
-        private readonly BeatmapSetHeader beatmapSetHeader;
-
-        [Cached(typeof(IBindable<RulesetInfo>))]
-        private readonly Bindable<RulesetInfo> ruleset = new Bindable<RulesetInfo>();
-
-        public Header()
+        public BeatmapSetHeaderContent()
         {
             ExternalLinkButton externalLink;
 
             RelativeSizeAxes = Axes.X;
             AutoSizeAxes = Axes.Y;
-            Masking = true;
-
-            EdgeEffect = new EdgeEffectParameters
-            {
-                Colour = Color4.Black.Opacity(0.25f),
-                Type = EdgeEffectType.Shadow,
-                Radius = 3,
-                Offset = new Vector2(0f, 1f),
-            };
-
-            InternalChild = new FillFlowContainer
+            InternalChild = new Container
             {
                 RelativeSizeAxes = Axes.X,
                 AutoSizeAxes = Axes.Y,
-                Direction = FillDirection.Vertical,
                 Children = new Drawable[]
                 {
-                    beatmapSetHeader = new BeatmapSetHeader
+                    new Container
                     {
-                        Ruleset = { BindTarget = ruleset },
+                        RelativeSizeAxes = Axes.Both,
+                        Children = new Drawable[]
+                        {
+                            cover = new UpdateableBeatmapSetCover
+                            {
+                                RelativeSizeAxes = Axes.Both,
+                                Masking = true,
+                            },
+                            coverGradient = new Box
+                            {
+                                RelativeSizeAxes = Axes.Both
+                            },
+                        },
                     },
                     new Container
                     {
                         RelativeSizeAxes = Axes.X,
                         AutoSizeAxes = Axes.Y,
+                        Padding = new MarginPadding
+                        {
+                            Vertical = BeatmapSetOverlay.Y_PADDING,
+                            Left = BeatmapSetOverlay.X_PADDING,
+                            Right = BeatmapSetOverlay.X_PADDING + BeatmapSetOverlay.RIGHT_WIDTH,
+                        },
                         Children = new Drawable[]
                         {
-                            new Container
-                            {
-                                RelativeSizeAxes = Axes.Both,
-                                Children = new Drawable[]
-                                {
-                                    cover = new UpdateableBeatmapSetCover
-                                    {
-                                        RelativeSizeAxes = Axes.Both,
-                                        Masking = true,
-                                    },
-                                    coverGradient = new Box
-                                    {
-                                        RelativeSizeAxes = Axes.Both
-                                    },
-                                },
-                            },
-                            new Container
+                            fadeContent = new FillFlowContainer
                             {
                                 RelativeSizeAxes = Axes.X,
                                 AutoSizeAxes = Axes.Y,
-                                Padding = new MarginPadding
-                                {
-                                    Vertical = BeatmapSetOverlay.Y_PADDING,
-                                    Left = BeatmapSetOverlay.X_PADDING,
-                                    Right = BeatmapSetOverlay.X_PADDING + BeatmapSetOverlay.RIGHT_WIDTH,
-                                },
+                                Direction = FillDirection.Vertical,
                                 Children = new Drawable[]
                                 {
-                                    fadeContent = new FillFlowContainer
+                                    new Container
                                     {
                                         RelativeSizeAxes = Axes.X,
                                         AutoSizeAxes = Axes.Y,
-                                        Direction = FillDirection.Vertical,
+                                        Child = Picker = new BeatmapPicker(),
+                                    },
+                                    new FillFlowContainer
+                                    {
+                                        Direction = FillDirection.Horizontal,
+                                        AutoSizeAxes = Axes.Both,
+                                        Margin = new MarginPadding { Top = 15 },
                                         Children = new Drawable[]
                                         {
-                                            new Container
+                                            title = new OsuSpriteText
                                             {
-                                                RelativeSizeAxes = Axes.X,
-                                                AutoSizeAxes = Axes.Y,
-                                                Child = Picker = new BeatmapPicker(),
+                                                Font = OsuFont.GetFont(size: 30, weight: FontWeight.SemiBold, italics: true)
                                             },
-                                            new FillFlowContainer
+                                            externalLink = new ExternalLinkButton
                                             {
-                                                Direction = FillDirection.Horizontal,
-                                                AutoSizeAxes = Axes.Both,
-                                                Margin = new MarginPadding { Top = 15 },
-                                                Children = new Drawable[]
-                                                {
-                                                    title = new OsuSpriteText
-                                                    {
-                                                        Font = OsuFont.GetFont(size: 30, weight: FontWeight.SemiBold, italics: true)
-                                                    },
-                                                    externalLink = new ExternalLinkButton
-                                                    {
-                                                        Anchor = Anchor.BottomLeft,
-                                                        Origin = Anchor.BottomLeft,
-                                                        Margin = new MarginPadding { Left = 5, Bottom = 4 }, // To better lineup with the font
-                                                    },
-                                                    explicitContentPill = new ExplicitContentBeatmapPill
-                                                    {
-                                                        Alpha = 0f,
-                                                        Anchor = Anchor.BottomLeft,
-                                                        Origin = Anchor.BottomLeft,
-                                                        Margin = new MarginPadding { Left = 10, Bottom = 4 },
-                                                    }
-                                                }
+                                                Anchor = Anchor.BottomLeft,
+                                                Origin = Anchor.BottomLeft,
+                                                Margin = new MarginPadding { Left = 5, Bottom = 4 }, // To better lineup with the font
                                             },
-                                            artist = new OsuSpriteText
+                                            explicitContentPill = new ExplicitContentBeatmapPill
                                             {
-                                                Font = OsuFont.GetFont(size: 20, weight: FontWeight.Medium, italics: true),
-                                                Margin = new MarginPadding { Bottom = 20 }
+                                                Alpha = 0f,
+                                                Anchor = Anchor.BottomLeft,
+                                                Origin = Anchor.BottomLeft,
+                                                Margin = new MarginPadding { Left = 10, Bottom = 4 },
+                                            }
+                                        }
+                                    },
+                                    artist = new OsuSpriteText
+                                    {
+                                        Font = OsuFont.GetFont(size: 20, weight: FontWeight.Medium, italics: true),
+                                        Margin = new MarginPadding { Bottom = 20 }
+                                    },
+                                    new Container
+                                    {
+                                        RelativeSizeAxes = Axes.X,
+                                        AutoSizeAxes = Axes.Y,
+                                        Child = author = new AuthorInfo(),
+                                    },
+                                    beatmapAvailability = new BeatmapAvailability(),
+                                    new Container
+                                    {
+                                        RelativeSizeAxes = Axes.X,
+                                        Height = buttons_height,
+                                        Margin = new MarginPadding { Top = 10 },
+                                        Children = new Drawable[]
+                                        {
+                                            favouriteButton = new FavouriteButton
+                                            {
+                                                BeatmapSet = { BindTarget = BeatmapSet }
                                             },
-                                            new Container
+                                            downloadButtonsContainer = new FillFlowContainer
                                             {
-                                                RelativeSizeAxes = Axes.X,
-                                                AutoSizeAxes = Axes.Y,
-                                                Child = author = new AuthorInfo(),
-                                            },
-                                            beatmapAvailability = new BeatmapAvailability(),
-                                            new Container
-                                            {
-                                                RelativeSizeAxes = Axes.X,
-                                                Height = buttons_height,
-                                                Margin = new MarginPadding { Top = 10 },
-                                                Children = new Drawable[]
-                                                {
-                                                    favouriteButton = new FavouriteButton
-                                                    {
-                                                        BeatmapSet = { BindTarget = BeatmapSet }
-                                                    },
-                                                    downloadButtonsContainer = new FillFlowContainer
-                                                    {
-                                                        RelativeSizeAxes = Axes.Both,
-                                                        Padding = new MarginPadding { Left = buttons_height + buttons_spacing },
-                                                        Spacing = new Vector2(buttons_spacing),
-                                                    },
-                                                },
+                                                RelativeSizeAxes = Axes.Both,
+                                                Padding = new MarginPadding { Left = buttons_height + buttons_spacing },
+                                                Spacing = new Vector2(buttons_spacing),
                                             },
                                         },
                                     },
-                                }
-                            },
-                            loading = new LoadingSpinner
-                            {
-                                Anchor = Anchor.Centre,
-                                Origin = Anchor.Centre,
-                                Scale = new Vector2(1.5f),
-                            },
-                            new FillFlowContainer
-                            {
-                                Anchor = Anchor.BottomRight,
-                                Origin = Anchor.BottomRight,
-                                AutoSizeAxes = Axes.Both,
-                                Margin = new MarginPadding { Top = BeatmapSetOverlay.Y_PADDING, Right = BeatmapSetOverlay.X_PADDING },
-                                Direction = FillDirection.Vertical,
-                                Spacing = new Vector2(10),
-                                Children = new Drawable[]
-                                {
-                                    onlineStatusPill = new BeatmapSetOnlineStatusPill
-                                    {
-                                        Anchor = Anchor.TopRight,
-                                        Origin = Anchor.TopRight,
-                                        TextSize = 14,
-                                        TextPadding = new MarginPadding { Horizontal = 35, Vertical = 10 }
-                                    },
-                                    Details = new Details(),
                                 },
                             },
+                        }
+                    },
+                    loading = new LoadingSpinner
+                    {
+                        Anchor = Anchor.Centre,
+                        Origin = Anchor.Centre,
+                        Scale = new Vector2(1.5f),
+                    },
+                    new FillFlowContainer
+                    {
+                        Anchor = Anchor.BottomRight,
+                        Origin = Anchor.BottomRight,
+                        AutoSizeAxes = Axes.Both,
+                        Margin = new MarginPadding { Top = BeatmapSetOverlay.Y_PADDING, Right = BeatmapSetOverlay.X_PADDING },
+                        Direction = FillDirection.Vertical,
+                        Spacing = new Vector2(10),
+                        Children = new Drawable[]
+                        {
+                            onlineStatusPill = new BeatmapSetOnlineStatusPill
+                            {
+                                Anchor = Anchor.TopRight,
+                                Origin = Anchor.TopRight,
+                                TextSize = 14,
+                                TextPadding = new MarginPadding { Horizontal = 35, Vertical = 10 }
+                            },
+                            Details = new Details(),
                         },
                     },
                 }
@@ -239,7 +209,7 @@ namespace osu.Game.Overlays.BeatmapSet
 
             BeatmapSet.BindValueChanged(setInfo =>
             {
-                Picker.BeatmapSet = RulesetSelector.BeatmapSet = author.BeatmapSet = beatmapAvailability.BeatmapSet = Details.BeatmapSet = setInfo.NewValue;
+                Picker.BeatmapSet = rulesetSelector.BeatmapSet = author.BeatmapSet = beatmapAvailability.BeatmapSet = Details.BeatmapSet = setInfo.NewValue;
                 cover.BeatmapSet = setInfo.NewValue;
 
                 if (setInfo.NewValue == null)

osu.Game/Overlays/BeatmapSet/Scores/ScoreTable.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Extensions;
+using osu.Framework.Extensions.EnumExtensions;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.Sprites;
@@ -15,7 +16,6 @@ using osu.Game.Rulesets.Scoring;
 using osu.Game.Rulesets.UI;
 using osu.Game.Scoring;
 using osu.Game.Users.Drawables;
-using osu.Game.Utils;
 using osuTK;
 using osuTK.Graphics;
 
@@ -105,7 +105,7 @@ namespace osu.Game.Overlays.BeatmapSet.Scores
 
             var ruleset = scores.First().Ruleset.CreateInstance();
 
-            foreach (var result in OrderAttributeUtils.GetValuesInOrder<HitResult>())
+            foreach (var result in EnumExtensions.GetValuesInOrder<HitResult>())
             {
                 if (!allScoreStatistics.Contains(result))
                     continue;

osu.Game/Overlays/BeatmapSetOverlay.cs

@@ -19,15 +19,12 @@ using osuTK;
 
 namespace osu.Game.Overlays
 {
-    public class BeatmapSetOverlay : FullscreenOverlay<OverlayHeader> // we don't provide a standard header for now.
+    public class BeatmapSetOverlay : FullscreenOverlay<BeatmapSetHeader>
     {
         public const float X_PADDING = 40;
         public const float Y_PADDING = 25;
         public const float RIGHT_WIDTH = 275;
 
-        //todo: should be an OverlayHeader? or maybe not?
-        protected new readonly Header Header;
-
         [Resolved]
         private RulesetStore rulesets { get; set; }
 
@@ -39,7 +36,7 @@ namespace osu.Game.Overlays
         private readonly Box background;
 
         public BeatmapSetOverlay()
-            : base(OverlayColourScheme.Blue, null)
+            : base(OverlayColourScheme.Blue, new BeatmapSetHeader())
         {
             OverlayScrollContainer scroll;
             Info info;
@@ -72,14 +69,14 @@ namespace osu.Game.Overlays
                                     Direction = FillDirection.Vertical,
                                     Children = new Drawable[]
                                     {
-                                        Header = new Header(),
+                                        Header,
                                         info = new Info()
                                     }
                                 },
                             },
                             new ScoresContainer
                             {
-                                Beatmap = { BindTarget = Header.Picker.Beatmap }
+                                Beatmap = { BindTarget = Header.HeaderContent.Picker.Beatmap }
                             },
                             comments = new CommentsSection()
                         },
@@ -91,7 +88,7 @@ namespace osu.Game.Overlays
             info.BeatmapSet.BindTo(beatmapSet);
             comments.BeatmapSet.BindTo(beatmapSet);
 
-            Header.Picker.Beatmap.ValueChanged += b =>
+            Header.HeaderContent.Picker.Beatmap.ValueChanged += b =>
             {
                 info.Beatmap = b.NewValue;
 
@@ -125,7 +122,7 @@ namespace osu.Game.Overlays
             req.Success += res =>
             {
                 beatmapSet.Value = res.ToBeatmapSet(rulesets);
-                Header.Picker.Beatmap.Value = Header.BeatmapSet.Value.Beatmaps.First(b => b.OnlineBeatmapID == beatmapId);
+                Header.HeaderContent.Picker.Beatmap.Value = Header.BeatmapSet.Value.Beatmaps.First(b => b.OnlineBeatmapID == beatmapId);
             };
             API.Queue(req);
 

osu.Game/Overlays/Chat/ChatLine.cs

@@ -190,13 +190,13 @@ namespace osu.Game.Overlays.Chat
                     }
                 }
             };
-
-            updateMessageContent();
         }
 
         protected override void LoadComplete()
         {
             base.LoadComplete();
+
+            updateMessageContent();
             FinishTransforms(true);
         }
 

osu.Game/Overlays/Chat/DrawableChannel.cs

@@ -16,6 +16,7 @@ using osu.Framework.Graphics.Shapes;
 using osu.Game.Graphics;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics.Sprites;
+using osu.Framework.Utils;
 using osu.Game.Graphics.Sprites;
 
 namespace osu.Game.Overlays.Chat
@@ -24,7 +25,7 @@ namespace osu.Game.Overlays.Chat
     {
         public readonly Channel Channel;
         protected FillFlowContainer ChatLineFlow;
-        private OsuScrollContainer scroll;
+        private ChannelScrollContainer scroll;
 
         private bool scrollbarVisible = true;
 
@@ -56,7 +57,7 @@ namespace osu.Game.Overlays.Chat
             {
                 RelativeSizeAxes = Axes.Both,
                 Masking = true,
-                Child = scroll = new OsuScrollContainer
+                Child = scroll = new ChannelScrollContainer
                 {
                     ScrollbarVisible = scrollbarVisible,
                     RelativeSizeAxes = Axes.Both,
@@ -80,12 +81,6 @@ namespace osu.Game.Overlays.Chat
             Channel.PendingMessageResolved += pendingMessageResolved;
         }
 
-        protected override void LoadComplete()
-        {
-            base.LoadComplete();
-            scrollToEnd();
-        }
-
         protected override void Dispose(bool isDisposing)
         {
             base.Dispose(isDisposing);
@@ -113,8 +108,6 @@ namespace osu.Game.Overlays.Chat
                 ChatLineFlow.Clear();
             }
 
-            bool shouldScrollToEnd = scroll.IsScrolledToEnd(10) || !chatLines.Any() || newMessages.Any(m => m is LocalMessage);
-
             // Add up to last Channel.MAX_HISTORY messages
             var displayMessages = newMessages.Skip(Math.Max(0, newMessages.Count() - Channel.MAX_HISTORY));
 
@@ -153,8 +146,10 @@ namespace osu.Game.Overlays.Chat
                 }
             }
 
-            if (shouldScrollToEnd)
-                scrollToEnd();
+            // due to the scroll adjusts from old messages removal above, a scroll-to-end must be enforced,
+            // to avoid making the container think the user has scrolled back up and unwantedly disable auto-scrolling.
+            if (newMessages.Any(m => m is LocalMessage))
+                scroll.ScrollToEnd();
         });
 
         private void pendingMessageResolved(Message existing, Message updated) => Schedule(() =>
@@ -178,8 +173,6 @@ namespace osu.Game.Overlays.Chat
 
         private IEnumerable<ChatLine> chatLines => ChatLineFlow.Children.OfType<ChatLine>();
 
-        private void scrollToEnd() => ScheduleAfterChildren(() => scroll.ScrollToEnd());
-
         public class DaySeparator : Container
         {
             public float TextSize
@@ -243,5 +236,51 @@ namespace osu.Game.Overlays.Chat
                 };
             }
         }
+
+        /// <summary>
+        /// An <see cref="OsuScrollContainer"/> with functionality to automatically scroll whenever the maximum scrollable distance increases.
+        /// </summary>
+        private class ChannelScrollContainer : UserTrackingScrollContainer
+        {
+            /// <summary>
+            /// The chat will be automatically scrolled to end if and only if
+            /// the distance between the current scroll position and the end of the scroll
+            /// is less than this value.
+            /// </summary>
+            private const float auto_scroll_leniency = 10f;
+
+            private float? lastExtent;
+
+            protected override void OnUserScroll(float value, bool animated = true, double? distanceDecay = default)
+            {
+                base.OnUserScroll(value, animated, distanceDecay);
+                lastExtent = null;
+            }
+
+            protected override void Update()
+            {
+                base.Update();
+
+                // If the user has scrolled to the bottom of the container, we should resume tracking new content.
+                if (UserScrolling && IsScrolledToEnd(auto_scroll_leniency))
+                    CancelUserScroll();
+
+                // If the user hasn't overridden our behaviour and there has been new content added to the container, we should update our scroll position to track it.
+                bool requiresScrollUpdate = !UserScrolling && (lastExtent == null || Precision.AlmostBigger(ScrollableExtent, lastExtent.Value));
+
+                if (requiresScrollUpdate)
+                {
+                    // Schedule required to allow FillFlow to be the correct size.
+                    Schedule(() =>
+                    {
+                        if (!UserScrolling)
+                        {
+                            ScrollToEnd();
+                            lastExtent = ScrollableExtent;
+                        }
+                    });
+                }
+            }
+        }
     }
 }

osu.Game/Overlays/Comments/VotePill.cs

@@ -33,11 +33,16 @@ namespace osu.Game.Overlays.Comments
         [Resolved]
         private IAPIProvider api { get; set; }
 
+        [Resolved(canBeNull: true)]
+        private LoginOverlay login { get; set; }
+
         [Resolved]
         private OverlayColourProvider colourProvider { get; set; }
 
+        protected Box Background { get; private set; }
+
         private readonly Comment comment;
-        private Box background;
+
         private Box hoverLayer;
         private CircularContainer borderContainer;
         private SpriteText sideNumber;
@@ -62,8 +67,12 @@ namespace osu.Game.Overlays.Comments
             AccentColour = borderContainer.BorderColour = sideNumber.Colour = colours.GreenLight;
             hoverLayer.Colour = Color4.Black.Opacity(0.5f);
 
-            if (api.IsLoggedIn && api.LocalUser.Value.Id != comment.UserId)
+            var ownComment = api.LocalUser.Value.Id == comment.UserId;
+
+            if (!ownComment)
                 Action = onAction;
+
+            Background.Alpha = ownComment ? 0 : 1;
         }
 
         protected override void LoadComplete()
@@ -71,12 +80,18 @@ namespace osu.Game.Overlays.Comments
             base.LoadComplete();
             isVoted.Value = comment.IsVoted;
             votesCount.Value = comment.VotesCount;
-            isVoted.BindValueChanged(voted => background.Colour = voted.NewValue ? AccentColour : colourProvider.Background6, true);
+            isVoted.BindValueChanged(voted => Background.Colour = voted.NewValue ? AccentColour : colourProvider.Background6, true);
             votesCount.BindValueChanged(count => votesCounter.Text = $"+{count.NewValue}", true);
         }
 
         private void onAction()
         {
+            if (!api.IsLoggedIn)
+            {
+                login?.Show();
+                return;
+            }
+
             request = new CommentVoteRequest(comment.Id, isVoted.Value ? CommentVoteAction.UnVote : CommentVoteAction.Vote);
             request.Success += onSuccess;
             api.Queue(request);
@@ -102,7 +117,7 @@ namespace osu.Game.Overlays.Comments
                     Masking = true,
                     Children = new Drawable[]
                     {
-                        background = new Box
+                        Background = new Box
                         {
                             RelativeSizeAxes = Axes.Both
                         },

osu.Game/Overlays/Mods/LocalPlayerModSelectOverlay.cs

@@ -0,0 +1,18 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Game.Rulesets.Mods;
+
+namespace osu.Game.Overlays.Mods
+{
+    public class LocalPlayerModSelectOverlay : ModSelectOverlay
+    {
+        protected override void OnModSelected(Mod mod)
+        {
+            base.OnModSelected(mod);
+
+            foreach (var section in ModSectionsContainer.Children)
+                section.DeselectTypes(mod.IncompatibleMods, true);
+        }
+    }
+}

osu.Game/Overlays/Mods/ModButton.cs

@@ -236,13 +236,13 @@ namespace osu.Game.Overlays.Mods
             {
                 iconsContainer.AddRange(new[]
                 {
-                    backgroundIcon = new PassThroughTooltipModIcon(Mods[1])
+                    backgroundIcon = new ModIcon(Mods[1], false)
                     {
                         Origin = Anchor.BottomRight,
                         Anchor = Anchor.BottomRight,
                         Position = new Vector2(1.5f),
                     },
-                    foregroundIcon = new PassThroughTooltipModIcon(Mods[0])
+                    foregroundIcon = new ModIcon(Mods[0], false)
                     {
                         Origin = Anchor.BottomRight,
                         Anchor = Anchor.BottomRight,
@@ -252,7 +252,7 @@ namespace osu.Game.Overlays.Mods
             }
             else
             {
-                iconsContainer.Add(foregroundIcon = new PassThroughTooltipModIcon(Mod)
+                iconsContainer.Add(foregroundIcon = new ModIcon(Mod, false)
                 {
                     Origin = Anchor.Centre,
                     Anchor = Anchor.Centre,
@@ -297,15 +297,5 @@ namespace osu.Game.Overlays.Mods
 
             Mod = mod;
         }
-
-        private class PassThroughTooltipModIcon : ModIcon
-        {
-            public override string TooltipText => null;
-
-            public PassThroughTooltipModIcon(Mod mod)
-                : base(mod)
-            {
-            }
-        }
     }
 }

osu.Game/Overlays/Mods/ModSection.cs

@@ -11,31 +11,30 @@ using System;
 using System.Linq;
 using System.Collections.Generic;
 using System.Threading;
+using Humanizer;
 using osu.Framework.Input.Events;
 using osu.Game.Graphics;
 
 namespace osu.Game.Overlays.Mods
 {
-    public abstract class ModSection : Container
+    public class ModSection : CompositeDrawable
     {
-        private readonly OsuSpriteText headerLabel;
+        private readonly Drawable header;
 
         public FillFlowContainer<ModButtonEmpty> ButtonsContainer { get; }
 
         public Action<Mod> Action;
-        protected abstract Key[] ToggleKeys { get; }
-        public abstract ModType ModType { get; }
 
-        public string Header
-        {
-            get => headerLabel.Text;
-            set => headerLabel.Text = value;
-        }
+        public Key[] ToggleKeys;
+
+        public readonly ModType ModType;
 
         public IEnumerable<Mod> SelectedMods => buttons.Select(b => b.SelectedMod).Where(m => m != null);
 
         private CancellationTokenSource modsLoadCts;
 
+        protected bool SelectionAnimationRunning => pendingSelectionOperations.Count > 0;
+
         /// <summary>
         /// True when all mod icons have completed loading.
         /// </summary>
@@ -52,7 +51,11 @@ namespace osu.Game.Overlays.Mods
 
                     return new ModButton(m)
                     {
-                        SelectionChanged = Action,
+                        SelectionChanged = mod =>
+                        {
+                            ModButtonStateChanged(mod);
+                            Action?.Invoke(mod);
+                        },
                     };
                 }).ToArray();
 
@@ -61,7 +64,7 @@ namespace osu.Game.Overlays.Mods
                 if (modContainers.Length == 0)
                 {
                     ModIconsLoaded = true;
-                    headerLabel.Hide();
+                    header.Hide();
                     Hide();
                     return;
                 }
@@ -76,11 +79,15 @@ namespace osu.Game.Overlays.Mods
 
                 buttons = modContainers.OfType<ModButton>().ToArray();
 
-                headerLabel.FadeIn(200);
+                header.FadeIn(200);
                 this.FadeIn(200);
             }
         }
 
+        protected virtual void ModButtonStateChanged(Mod mod)
+        {
+        }
+
         private ModButton[] buttons = Array.Empty<ModButton>();
 
         protected override bool OnKeyDown(KeyDownEvent e)
@@ -97,30 +104,75 @@ namespace osu.Game.Overlays.Mods
             return base.OnKeyDown(e);
         }
 
-        public void DeselectAll() => DeselectTypes(buttons.Select(b => b.SelectedMod?.GetType()).Where(t => t != null));
+        private const double initial_multiple_selection_delay = 120;
+
+        private double selectionDelay = initial_multiple_selection_delay;
+        private double lastSelection;
+
+        private readonly Queue<Action> pendingSelectionOperations = new Queue<Action>();
+
+        protected override void Update()
+        {
+            base.Update();
+
+            if (selectionDelay == initial_multiple_selection_delay || Time.Current - lastSelection >= selectionDelay)
+            {
+                if (pendingSelectionOperations.TryDequeue(out var dequeuedAction))
+                {
+                    dequeuedAction();
+
+                    // each time we play an animation, we decrease the time until the next animation (to ramp the visual and audible elements).
+                    selectionDelay = Math.Max(30, selectionDelay * 0.8f);
+                    lastSelection = Time.Current;
+                }
+                else
+                {
+                    // reset the selection delay after all animations have been completed.
+                    // this will cause the next action to be immediately performed.
+                    selectionDelay = initial_multiple_selection_delay;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Selects all mods.
+        /// </summary>
+        public void SelectAll()
+        {
+            pendingSelectionOperations.Clear();
+
+            foreach (var button in buttons.Where(b => !b.Selected))
+                pendingSelectionOperations.Enqueue(() => button.SelectAt(0));
+        }
+
+        /// <summary>
+        /// Deselects all mods.
+        /// </summary>
+        public void DeselectAll()
+        {
+            pendingSelectionOperations.Clear();
+            DeselectTypes(buttons.Select(b => b.SelectedMod?.GetType()).Where(t => t != null));
+        }
 
         /// <summary>
         /// Deselect one or more mods in this section.
         /// </summary>
         /// <param name="modTypes">The types of <see cref="Mod"/>s which should be deselected.</param>
-        /// <param name="immediate">Set to true to bypass animations and update selections immediately.</param>
+        /// <param name="immediate">Whether the deselection should happen immediately. Should only be used when required to ensure correct selection flow.</param>
         public void DeselectTypes(IEnumerable<Type> modTypes, bool immediate = false)
         {
-            int delay = 0;
-
             foreach (var button in buttons)
             {
-                Mod selected = button.SelectedMod;
-                if (selected == null) continue;
+                if (button.SelectedMod == null) continue;
 
                 foreach (var type in modTypes)
                 {
-                    if (type.IsInstanceOfType(selected))
+                    if (type.IsInstanceOfType(button.SelectedMod))
                     {
                         if (immediate)
                             button.Deselect();
                         else
-                            Scheduler.AddDelayed(button.Deselect, delay += 50);
+                            pendingSelectionOperations.Enqueue(button.Deselect);
                     }
                 }
             }
@@ -130,13 +182,13 @@ namespace osu.Game.Overlays.Mods
         /// Updates all buttons with the given list of selected mods.
         /// </summary>
         /// <param name="newSelectedMods">The new list of selected mods to select.</param>
-        public void UpdateSelectedMods(IReadOnlyList<Mod> newSelectedMods)
+        public void UpdateSelectedButtons(IReadOnlyList<Mod> newSelectedMods)
         {
             foreach (var button in buttons)
-                updateButtonMods(button, newSelectedMods);
+                updateButtonSelection(button, newSelectedMods);
         }
 
-        private void updateButtonMods(ModButton button, IReadOnlyList<Mod> newSelectedMods)
+        private void updateButtonSelection(ModButton button, IReadOnlyList<Mod> newSelectedMods)
         {
             foreach (var mod in newSelectedMods)
             {
@@ -153,23 +205,19 @@ namespace osu.Game.Overlays.Mods
             button.Deselect();
         }
 
-        protected ModSection()
+        public ModSection(ModType type)
         {
+            ModType = type;
+
             AutoSizeAxes = Axes.Y;
             RelativeSizeAxes = Axes.X;
 
             Origin = Anchor.TopCentre;
             Anchor = Anchor.TopCentre;
 
-            Children = new Drawable[]
+            InternalChildren = new[]
             {
-                headerLabel = new OsuSpriteText
-                {
-                    Origin = Anchor.TopLeft,
-                    Anchor = Anchor.TopLeft,
-                    Position = new Vector2(0f, 0f),
-                    Font = OsuFont.GetFont(weight: FontWeight.Bold)
-                },
+                header = CreateHeader(type.Humanize(LetterCasing.Title)),
                 ButtonsContainer = new FillFlowContainer<ModButtonEmpty>
                 {
                     AutoSizeAxes = Axes.Y,
@@ -185,5 +233,20 @@ namespace osu.Game.Overlays.Mods
                 },
             };
         }
+
+        protected virtual Drawable CreateHeader(string text) => new OsuSpriteText
+        {
+            Font = OsuFont.GetFont(weight: FontWeight.Bold),
+            Text = text
+        };
+
+        /// <summary>
+        /// Play out all remaining animations immediately to leave mods in a good (final) state.
+        /// </summary>
+        public void FlushAnimation()
+        {
+            while (pendingSelectionOperations.TryDequeue(out var dequeuedAction))
+                dequeuedAction();
+        }
     }
 }

osu.Game/Overlays/Mods/ModSelectOverlay.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Audio.Sample;
@@ -19,30 +20,54 @@ using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.Sprites;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Input.Bindings;
-using osu.Game.Overlays.Mods.Sections;
 using osu.Game.Rulesets.Mods;
 using osu.Game.Screens;
+using osu.Game.Utils;
 using osuTK;
 using osuTK.Graphics;
 using osuTK.Input;
 
 namespace osu.Game.Overlays.Mods
 {
-    public class ModSelectOverlay : WaveOverlayContainer
+    public abstract class ModSelectOverlay : WaveOverlayContainer
     {
-        private readonly Func<Mod, bool> isValidMod;
         public const float HEIGHT = 510;
 
         protected readonly TriangleButton DeselectAllButton;
         protected readonly TriangleButton CustomiseButton;
         protected readonly TriangleButton CloseButton;
 
+        protected readonly Drawable MultiplierSection;
         protected readonly OsuSpriteText MultiplierLabel;
 
+        protected readonly FillFlowContainer FooterContainer;
+
         protected override bool BlockNonPositionalInput => false;
 
         protected override bool DimMainContent => false;
 
+        /// <summary>
+        /// Whether <see cref="Mod"/>s underneath the same <see cref="MultiMod"/> instance should appear as stacked buttons.
+        /// </summary>
+        protected virtual bool Stacked => true;
+
+        [NotNull]
+        private Func<Mod, bool> isValidMod = m => true;
+
+        /// <summary>
+        /// A function that checks whether a given mod is selectable.
+        /// </summary>
+        [NotNull]
+        public Func<Mod, bool> IsValidMod
+        {
+            get => isValidMod;
+            set
+            {
+                isValidMod = value ?? throw new ArgumentNullException(nameof(value));
+                updateAvailableMods();
+            }
+        }
+
         protected readonly FillFlowContainer<ModSection> ModSectionsContainer;
 
         protected readonly ModSettingsContainer ModSettingsContainer;
@@ -57,14 +82,10 @@ namespace osu.Game.Overlays.Mods
         private const float content_width = 0.8f;
         private const float footer_button_spacing = 20;
 
-        private readonly FillFlowContainer footerContainer;
-
         private SampleChannel sampleOn, sampleOff;
 
-        public ModSelectOverlay(Func<Mod, bool> isValidMod = null)
+        protected ModSelectOverlay()
         {
-            this.isValidMod = isValidMod ?? (m => true);
-
             Waves.FirstWaveColour = Color4Extensions.FromHex(@"19b0e2");
             Waves.SecondWaveColour = Color4Extensions.FromHex(@"2280a2");
             Waves.ThirdWaveColour = Color4Extensions.FromHex(@"005774");
@@ -190,13 +211,31 @@ namespace osu.Game.Overlays.Mods
                                                 Width = content_width,
                                                 LayoutDuration = 200,
                                                 LayoutEasing = Easing.OutQuint,
-                                                Children = new ModSection[]
+                                                Children = new[]
                                                 {
-                                                    new DifficultyReductionSection { Action = modButtonPressed },
-                                                    new DifficultyIncreaseSection { Action = modButtonPressed },
-                                                    new AutomationSection { Action = modButtonPressed },
-                                                    new ConversionSection { Action = modButtonPressed },
-                                                    new FunSection { Action = modButtonPressed },
+                                                    CreateModSection(ModType.DifficultyReduction).With(s =>
+                                                    {
+                                                        s.ToggleKeys = new[] { Key.Q, Key.W, Key.E, Key.R, Key.T, Key.Y, Key.U, Key.I, Key.O, Key.P };
+                                                        s.Action = modButtonPressed;
+                                                    }),
+                                                    CreateModSection(ModType.DifficultyIncrease).With(s =>
+                                                    {
+                                                        s.ToggleKeys = new[] { Key.A, Key.S, Key.D, Key.F, Key.G, Key.H, Key.J, Key.K, Key.L };
+                                                        s.Action = modButtonPressed;
+                                                    }),
+                                                    CreateModSection(ModType.Automation).With(s =>
+                                                    {
+                                                        s.ToggleKeys = new[] { Key.Z, Key.X, Key.C, Key.V, Key.B, Key.N, Key.M };
+                                                        s.Action = modButtonPressed;
+                                                    }),
+                                                    CreateModSection(ModType.Conversion).With(s =>
+                                                    {
+                                                        s.Action = modButtonPressed;
+                                                    }),
+                                                    CreateModSection(ModType.Fun).With(s =>
+                                                    {
+                                                        s.Action = modButtonPressed;
+                                                    }),
                                                 }
                                             },
                                         }
@@ -216,9 +255,9 @@ namespace osu.Game.Overlays.Mods
                         },
                         new Drawable[]
                         {
-                            // Footer
                             new Container
                             {
+                                Name = "Footer content",
                                 RelativeSizeAxes = Axes.X,
                                 AutoSizeAxes = Axes.Y,
                                 Origin = Anchor.TopCentre,
@@ -231,22 +270,21 @@ namespace osu.Game.Overlays.Mods
                                         Colour = new Color4(172, 20, 116, 255),
                                         Alpha = 0.5f,
                                     },
-                                    footerContainer = new FillFlowContainer
+                                    FooterContainer = new FillFlowContainer
                                     {
                                         Origin = Anchor.BottomCentre,
                                         Anchor = Anchor.BottomCentre,
                                         AutoSizeAxes = Axes.Y,
                                         RelativeSizeAxes = Axes.X,
+                                        RelativePositionAxes = Axes.X,
                                         Width = content_width,
                                         Spacing = new Vector2(footer_button_spacing, footer_button_spacing / 2),
-                                        LayoutDuration = 100,
-                                        LayoutEasing = Easing.OutQuint,
                                         Padding = new MarginPadding
                                         {
                                             Vertical = 15,
                                             Horizontal = OsuScreen.HORIZONTAL_OVERFLOW_PADDING
                                         },
-                                        Children = new Drawable[]
+                                        Children = new[]
                                         {
                                             DeselectAllButton = new TriangleButton
                                             {
@@ -273,7 +311,7 @@ namespace osu.Game.Overlays.Mods
                                                 Origin = Anchor.CentreLeft,
                                                 Anchor = Anchor.CentreLeft,
                                             },
-                                            new FillFlowContainer
+                                            MultiplierSection = new FillFlowContainer
                                             {
                                                 AutoSizeAxes = Axes.Both,
                                                 Spacing = new Vector2(footer_button_spacing / 2, 0),
@@ -329,33 +367,25 @@ namespace osu.Game.Overlays.Mods
             refreshSelectedMods();
         }
 
-        /// <summary>
-        /// Deselect one or more mods.
-        /// </summary>
-        /// <param name="modTypes">The types of <see cref="Mod"/>s which should be deselected.</param>
-        /// <param name="immediate">Set to true to bypass animations and update selections immediately.</param>
-        private void deselectTypes(Type[] modTypes, bool immediate = false)
-        {
-            if (modTypes.Length == 0) return;
-
-            foreach (var section in ModSectionsContainer.Children)
-                section.DeselectTypes(modTypes, immediate);
-        }
-
         protected override void LoadComplete()
         {
             base.LoadComplete();
 
-            availableMods.BindValueChanged(availableModsChanged, true);
-            SelectedMods.BindValueChanged(selectedModsChanged, true);
+            availableMods.BindValueChanged(_ => updateAvailableMods(), true);
+            SelectedMods.BindValueChanged(_ => updateSelectedButtons(), true);
         }
 
         protected override void PopOut()
         {
             base.PopOut();
 
-            footerContainer.MoveToX(footerContainer.DrawSize.X, WaveContainer.DISAPPEAR_DURATION, Easing.InSine);
-            footerContainer.FadeOut(WaveContainer.DISAPPEAR_DURATION, Easing.InSine);
+            foreach (var section in ModSectionsContainer)
+            {
+                section.FlushAnimation();
+            }
+
+            FooterContainer.MoveToX(content_width, WaveContainer.DISAPPEAR_DURATION, Easing.InSine);
+            FooterContainer.FadeOut(WaveContainer.DISAPPEAR_DURATION, Easing.InSine);
 
             foreach (var section in ModSectionsContainer.Children)
             {
@@ -369,8 +399,8 @@ namespace osu.Game.Overlays.Mods
         {
             base.PopIn();
 
-            footerContainer.MoveToX(0, WaveContainer.APPEAR_DURATION, Easing.OutQuint);
-            footerContainer.FadeIn(WaveContainer.APPEAR_DURATION, Easing.OutQuint);
+            FooterContainer.MoveToX(0, WaveContainer.APPEAR_DURATION, Easing.OutQuint);
+            FooterContainer.FadeIn(WaveContainer.APPEAR_DURATION, Easing.OutQuint);
 
             foreach (var section in ModSectionsContainer.Children)
             {
@@ -401,18 +431,53 @@ namespace osu.Game.Overlays.Mods
 
         public override bool OnPressed(GlobalAction action) => false; // handled by back button
 
-        private void availableModsChanged(ValueChangedEvent<Dictionary<ModType, IReadOnlyList<Mod>>> mods)
+        private void updateAvailableMods()
         {
-            if (mods.NewValue == null) return;
+            if (availableMods?.Value == null)
+                return;
 
             foreach (var section in ModSectionsContainer.Children)
-                section.Mods = mods.NewValue[section.ModType].Where(isValidMod);
+            {
+                IEnumerable<Mod> modEnumeration = availableMods.Value[section.ModType];
+
+                if (!Stacked)
+                    modEnumeration = ModUtils.FlattenMods(modEnumeration);
+
+                section.Mods = modEnumeration.Select(getValidModOrNull).Where(m => m != null);
+            }
+
+            updateSelectedButtons();
         }
 
-        private void selectedModsChanged(ValueChangedEvent<IReadOnlyList<Mod>> mods)
+        /// <summary>
+        /// Returns a valid form of a given <see cref="Mod"/> if possible, or null otherwise.
+        /// </summary>
+        /// <remarks>
+        /// This is a recursive process during which any invalid mods are culled while preserving <see cref="MultiMod"/> structures where possible.
+        /// </remarks>
+        /// <param name="mod">The <see cref="Mod"/> to check.</param>
+        /// <returns>A valid form of <paramref name="mod"/> if exists, or null otherwise.</returns>
+        [CanBeNull]
+        private Mod getValidModOrNull([NotNull] Mod mod)
         {
+            if (!(mod is MultiMod multi))
+                return IsValidMod(mod) ? mod : null;
+
+            var validSubset = multi.Mods.Select(getValidModOrNull).Where(m => m != null).ToArray();
+
+            if (validSubset.Length == 0)
+                return null;
+
+            return validSubset.Length == 1 ? validSubset[0] : new MultiMod(validSubset);
+        }
+
+        private void updateSelectedButtons()
+        {
+            // Enumeration below may update the bindable list.
+            var selectedMods = SelectedMods.Value.ToList();
+
             foreach (var section in ModSectionsContainer.Children)
-                section.UpdateSelectedMods(mods.NewValue);
+                section.UpdateSelectedButtons(selectedMods);
 
             updateMods();
         }
@@ -439,22 +504,42 @@ namespace osu.Game.Overlays.Mods
         {
             if (selectedMod != null)
             {
-                if (State.Value == Visibility.Visible) sampleOn?.Play();
+                if (State.Value == Visibility.Visible)
+                    Scheduler.AddOnce(playSelectedSound);
 
-                deselectTypes(selectedMod.IncompatibleMods, true);
+                OnModSelected(selectedMod);
 
                 if (selectedMod.RequiresConfiguration) ModSettingsContainer.Show();
             }
             else
             {
-                if (State.Value == Visibility.Visible) sampleOff?.Play();
+                if (State.Value == Visibility.Visible)
+                    Scheduler.AddOnce(playDeselectedSound);
             }
 
             refreshSelectedMods();
         }
 
+        private void playSelectedSound() => sampleOn?.Play();
+        private void playDeselectedSound() => sampleOff?.Play();
+
+        /// <summary>
+        /// Invoked when a new <see cref="Mod"/> has been selected.
+        /// </summary>
+        /// <param name="mod">The <see cref="Mod"/> that has been selected.</param>
+        protected virtual void OnModSelected(Mod mod)
+        {
+        }
+
         private void refreshSelectedMods() => SelectedMods.Value = ModSectionsContainer.Children.SelectMany(s => s.SelectedMods).ToArray();
 
+        /// <summary>
+        /// Creates a <see cref="ModSection"/> that groups <see cref="Mod"/>s with the same <see cref="ModType"/>.
+        /// </summary>
+        /// <param name="type">The <see cref="ModType"/> of <see cref="Mod"/>s in the section.</param>
+        /// <returns>The <see cref="ModSection"/>.</returns>
+        protected virtual ModSection CreateModSection(ModType type) => new ModSection(type);
+
         #region Disposal
 
         protected override void Dispose(bool isDisposing)

osu.Game/Overlays/Mods/Sections/AutomationSection.cs

@@ -1,19 +0,0 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
-// See the LICENCE file in the repository root for full licence text.
-
-using osu.Game.Rulesets.Mods;
-using osuTK.Input;
-
-namespace osu.Game.Overlays.Mods.Sections
-{
-    public class AutomationSection : ModSection
-    {
-        protected override Key[] ToggleKeys => new[] { Key.Z, Key.X, Key.C, Key.V, Key.B, Key.N, Key.M };
-        public override ModType ModType => ModType.Automation;
-
-        public AutomationSection()
-        {
-            Header = @"Automation";
-        }
-    }
-}

osu.Game/Overlays/Mods/Sections/ConversionSection.cs

@@ -1,19 +0,0 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
-// See the LICENCE file in the repository root for full licence text.
-
-using osu.Game.Rulesets.Mods;
-using osuTK.Input;
-
-namespace osu.Game.Overlays.Mods.Sections
-{
-    public class ConversionSection : ModSection
-    {
-        protected override Key[] ToggleKeys => null;
-        public override ModType ModType => ModType.Conversion;
-
-        public ConversionSection()
-        {
-            Header = @"Conversion";
-        }
-    }
-}

osu.Game/Overlays/Mods/Sections/DifficultyIncreaseSection.cs

@@ -1,19 +0,0 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
-// See the LICENCE file in the repository root for full licence text.
-
-using osu.Game.Rulesets.Mods;
-using osuTK.Input;
-
-namespace osu.Game.Overlays.Mods.Sections
-{
-    public class DifficultyIncreaseSection : ModSection
-    {
-        protected override Key[] ToggleKeys => new[] { Key.A, Key.S, Key.D, Key.F, Key.G, Key.H, Key.J, Key.K, Key.L };
-        public override ModType ModType => ModType.DifficultyIncrease;
-
-        public DifficultyIncreaseSection()
-        {
-            Header = @"Difficulty Increase";
-        }
-    }
-}