Merge branch 'master' into JudgementCounter

osu.Game/Audio/PreviewTrack.cs

@@ -109,6 +109,8 @@ namespace osu.Game.Audio
         protected override void Dispose(bool isDisposing)
         {
             base.Dispose(isDisposing);
+
+            Stop();
             Track?.Dispose();
         }
     }

osu.Game/Audio/SampleInfo.cs

@@ -35,7 +35,7 @@ namespace osu.Game.Audio
         public bool Equals(SampleInfo? other)
             => other != null && sampleNames.SequenceEqual(other.sampleNames);
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
             => obj is SampleInfo other && Equals(other);
     }
 }

osu.Game/Beatmaps/Beatmap.cs

@@ -81,9 +81,14 @@ namespace osu.Game.Beatmaps
 
         public double GetMostCommonBeatLength()
         {
+            double lastTime;
+
             // The last playable time in the beatmap - the last timing point extends to this time.
             // Note: This is more accurate and may present different results because osu-stable didn't have the ability to calculate slider durations in this context.
-            double lastTime = HitObjects.LastOrDefault()?.GetEndTime() ?? ControlPointInfo.TimingPoints.LastOrDefault()?.Time ?? 0;
+            if (!HitObjects.Any())
+                lastTime = ControlPointInfo.TimingPoints.LastOrDefault()?.Time ?? 0;
+            else
+                lastTime = this.GetLastObjectTime();
 
             var mostCommon =
                 // Construct a set of (beatLength, duration) tuples for each individual timing point.

osu.Game/Beatmaps/BeatmapImporter.cs

@@ -44,7 +44,7 @@ namespace osu.Game.Beatmaps
 
         public override async Task<Live<BeatmapSetInfo>?> ImportAsUpdate(ProgressNotification notification, ImportTask importTask, BeatmapSetInfo original)
         {
-            var imported = await Import(notification, importTask);
+            var imported = await Import(notification, new[] { importTask }).ConfigureAwait(true);
 
             if (!imported.Any())
                 return null;
@@ -203,10 +203,10 @@ namespace osu.Game.Beatmaps
             }
         }
 
-        protected override void PostImport(BeatmapSetInfo model, Realm realm, bool batchImport)
+        protected override void PostImport(BeatmapSetInfo model, Realm realm, ImportParameters parameters)
         {
-            base.PostImport(model, realm, batchImport);
-            ProcessBeatmap?.Invoke((model, batchImport));
+            base.PostImport(model, realm, parameters);
+            ProcessBeatmap?.Invoke((model, parameters.Batch));
         }
 
         private void validateOnlineIds(BeatmapSetInfo beatmapSet, Realm realm)

osu.Game/Beatmaps/BeatmapManager.cs

@@ -44,6 +44,16 @@ namespace osu.Game.Beatmaps
 
         public Action<(BeatmapSetInfo beatmapSet, bool isBatch)>? ProcessBeatmap { private get; set; }
 
+        public override bool PauseImports
+        {
+            get => base.PauseImports;
+            set
+            {
+                base.PauseImports = value;
+                beatmapImporter.PauseImports = value;
+            }
+        }
+
         public BeatmapManager(Storage storage, RealmAccess realm, IAPIProvider? api, AudioManager audioManager, IResourceStore<byte[]> gameResources, GameHost? host = null,
                               WorkingBeatmap? defaultBeatmap = null, BeatmapDifficultyCache? difficultyCache = null, bool performOnlineLookups = false)
             : base(storage, realm)
@@ -456,15 +466,16 @@ namespace osu.Game.Beatmaps
 
         public Task Import(params string[] paths) => beatmapImporter.Import(paths);
 
-        public Task Import(params ImportTask[] tasks) => beatmapImporter.Import(tasks);
+        public Task Import(ImportTask[] tasks, ImportParameters parameters = default) => beatmapImporter.Import(tasks, parameters);
 
-        public Task<IEnumerable<Live<BeatmapSetInfo>>> Import(ProgressNotification notification, params ImportTask[] tasks) => beatmapImporter.Import(notification, tasks);
+        public Task<IEnumerable<Live<BeatmapSetInfo>>> Import(ProgressNotification notification, ImportTask[] tasks, ImportParameters parameters = default) =>
+            beatmapImporter.Import(notification, tasks, parameters);
 
-        public Task<Live<BeatmapSetInfo>?> Import(ImportTask task, bool batchImport = false, CancellationToken cancellationToken = default) =>
-            beatmapImporter.Import(task, batchImport, cancellationToken);
+        public Task<Live<BeatmapSetInfo>?> Import(ImportTask task, ImportParameters parameters = default, CancellationToken cancellationToken = default) =>
+            beatmapImporter.Import(task, parameters, cancellationToken);
 
         public Live<BeatmapSetInfo>? Import(BeatmapSetInfo item, ArchiveReader? archive = null, CancellationToken cancellationToken = default) =>
-            beatmapImporter.ImportModel(item, archive, false, cancellationToken);
+            beatmapImporter.ImportModel(item, archive, default, cancellationToken);
 
         public IEnumerable<string> HandledExtensions => beatmapImporter.HandledExtensions;
 

osu.Game/Beatmaps/BeatmapSetOnlineNomination.cs

@@ -0,0 +1,22 @@
+// 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 Newtonsoft.Json;
+
+namespace osu.Game.Beatmaps
+{
+    public struct BeatmapSetOnlineNomination
+    {
+        [JsonProperty(@"beatmapset_id")]
+        public int BeatmapsetId { get; set; }
+
+        [JsonProperty(@"reset")]
+        public bool Reset { get; set; }
+
+        [JsonProperty(@"rulesets")]
+        public string[]? Rulesets { get; set; }
+
+        [JsonProperty(@"user_id")]
+        public int UserId { get; set; }
+    }
+}

osu.Game/Beatmaps/BeatmapUpdaterMetadataLookup.cs

@@ -178,7 +178,7 @@ namespace osu.Game.Beatmaps
             {
                 try
                 {
-                    await cacheDownloadRequest.PerformAsync();
+                    await cacheDownloadRequest.PerformAsync().ConfigureAwait(false);
                 }
                 catch
                 {

osu.Game/Beatmaps/ControlPoints/ControlPoint.cs

@@ -16,7 +16,7 @@ namespace osu.Game.Beatmaps.ControlPoints
 
         public void AttachGroup(ControlPointGroup pointGroup) => Time = pointGroup.Time;
 
-        public int CompareTo(ControlPoint other) => Time.CompareTo(other.Time);
+        public int CompareTo(ControlPoint? other) => Time.CompareTo(other?.Time);
 
         public virtual Color4 GetRepresentingColour(OsuColour colours) => colours.Yellow;
 
@@ -32,7 +32,7 @@ namespace osu.Game.Beatmaps.ControlPoints
         /// </summary>
         public ControlPoint DeepClone()
         {
-            var copy = (ControlPoint)Activator.CreateInstance(GetType());
+            var copy = (ControlPoint)Activator.CreateInstance(GetType())!;
 
             copy.CopyFrom(this);
 

osu.Game/Beatmaps/ControlPoints/ControlPointGroup.cs

@@ -26,7 +26,7 @@ namespace osu.Game.Beatmaps.ControlPoints
             Time = time;
         }
 
-        public int CompareTo(ControlPointGroup other) => Time.CompareTo(other.Time);
+        public int CompareTo(ControlPointGroup? other) => Time.CompareTo(other?.Time);
 
         public void Add(ControlPoint point)
         {

osu.Game/Beatmaps/ControlPoints/ControlPointInfo.cs

@@ -70,14 +70,14 @@ namespace osu.Game.Beatmaps.ControlPoints
         /// </summary>
         [JsonIgnore]
         public double BPMMaximum =>
-            60000 / (TimingPoints.OrderBy(c => c.BeatLength).FirstOrDefault() ?? TimingControlPoint.DEFAULT).BeatLength;
+            60000 / (TimingPoints.MinBy(c => c.BeatLength) ?? TimingControlPoint.DEFAULT).BeatLength;
 
         /// <summary>
         /// Finds the minimum BPM represented by any timing control point.
         /// </summary>
         [JsonIgnore]
         public double BPMMinimum =>
-            60000 / (TimingPoints.OrderByDescending(c => c.BeatLength).FirstOrDefault() ?? TimingControlPoint.DEFAULT).BeatLength;
+            60000 / (TimingPoints.MaxBy(c => c.BeatLength) ?? TimingControlPoint.DEFAULT).BeatLength;
 
         /// <summary>
         /// Remove all <see cref="ControlPointGroup"/>s and return to a pristine state.
@@ -211,8 +211,7 @@ namespace osu.Game.Beatmaps.ControlPoints
         public static T BinarySearch<T>(IReadOnlyList<T> list, double time)
             where T : class, IControlPoint
         {
-            if (list == null)
-                throw new ArgumentNullException(nameof(list));
+            ArgumentNullException.ThrowIfNull(list);
 
             if (list.Count == 0)
                 return null;
@@ -300,7 +299,7 @@ namespace osu.Game.Beatmaps.ControlPoints
 
         public ControlPointInfo DeepClone()
         {
-            var controlPointInfo = (ControlPointInfo)Activator.CreateInstance(GetType());
+            var controlPointInfo = (ControlPointInfo)Activator.CreateInstance(GetType())!;
 
             foreach (var point in AllControlPoints)
                 controlPointInfo.Add(point.Time, point.DeepClone());

osu.Game/Beatmaps/DifficultyRecommender.cs

@@ -51,11 +51,11 @@ namespace osu.Game.Beatmaps
                 if (!recommendedDifficultyMapping.TryGetValue(r, out double recommendation))
                     continue;
 
-                BeatmapInfo beatmapInfo = beatmaps.Where(b => b.Ruleset.ShortName.Equals(r)).OrderBy(b =>
+                BeatmapInfo beatmapInfo = beatmaps.Where(b => b.Ruleset.ShortName.Equals(r, StringComparison.Ordinal)).MinBy(b =>
                 {
                     double difference = b.StarRating - recommendation;
                     return difference >= 0 ? difference * 2 : difference * -1; // prefer easier over harder
-                }).FirstOrDefault();
+                });
 
                 if (beatmapInfo != null)
                     return beatmapInfo;
@@ -90,7 +90,7 @@ namespace osu.Game.Beatmaps
                 return recommendedDifficultyMapping
                        .OrderByDescending(pair => pair.Value)
                        .Select(pair => pair.Key)
-                       .Where(r => !r.Equals(ruleset.Value.ShortName))
+                       .Where(r => !r.Equals(ruleset.Value.ShortName, StringComparison.Ordinal))
                        .Prepend(ruleset.Value.ShortName);
             }
         }

osu.Game/Beatmaps/Drawables/BeatmapBackgroundSprite.cs

@@ -15,8 +15,7 @@ namespace osu.Game.Beatmaps.Drawables
 
         public BeatmapBackgroundSprite(IWorkingBeatmap working)
         {
-            if (working == null)
-                throw new ArgumentNullException(nameof(working));
+            ArgumentNullException.ThrowIfNull(working);
 
             this.working = working;
         }

osu.Game/Beatmaps/Drawables/Cards/BeatmapCard.cs

@@ -5,16 +5,19 @@ using System;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Cursor;
+using osu.Framework.Graphics.UserInterface;
 using osu.Framework.Input.Events;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Online;
 using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Overlays;
+using osu.Game.Localisation;
 
 namespace osu.Game.Beatmaps.Drawables.Cards
 {
-    public abstract partial class BeatmapCard : OsuClickableContainer
+    public abstract partial class BeatmapCard : OsuClickableContainer, IHasContextMenu
     {
         public const float TRANSITION_DURATION = 400;
         public const float CORNER_RADIUS = 10;
@@ -96,5 +99,10 @@ namespace osu.Game.Beatmaps.Drawables.Cards
                     throw new ArgumentOutOfRangeException(nameof(size), size, @"Unsupported card size");
             }
         }
+
+        public MenuItem[] ContextMenuItems => new MenuItem[]
+        {
+            new OsuMenuItem(ContextMenuStrings.ViewBeatmap, MenuItemType.Highlighted, Action),
+        };
     }
 }

osu.Game/Beatmaps/Drawables/Cards/BeatmapCardContent.cs

@@ -138,9 +138,18 @@ namespace osu.Game.Beatmaps.Drawables.Cards
             // This avoids depth issues where a hovered (scaled) card to the right of another card would be beneath the card to the left.
             this.ScaleTo(Expanded.Value ? 1.03f : 1, 500, Easing.OutQuint);
 
-            background.FadeTo(Expanded.Value ? 1 : 0, BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
-            dropdownContent.FadeTo(Expanded.Value ? 1 : 0, BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
-            borderContainer.FadeTo(Expanded.Value ? 1 : 0, BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
+            if (Expanded.Value)
+            {
+                background.FadeIn(BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
+                dropdownContent.FadeIn(BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
+                borderContainer.FadeIn(BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
+            }
+            else
+            {
+                background.FadeOut(BeatmapCard.TRANSITION_DURATION / 3f, Easing.OutQuint);
+                dropdownContent.FadeOut(BeatmapCard.TRANSITION_DURATION / 3f, Easing.OutQuint);
+                borderContainer.FadeOut(BeatmapCard.TRANSITION_DURATION / 3f, Easing.OutQuint);
+            }
 
             content.TweenEdgeEffectTo(new EdgeEffectParameters
             {

osu.Game/Beatmaps/Drawables/Cards/BeatmapCardThumbnail.cs

@@ -11,7 +11,7 @@ using osu.Game.Beatmaps.Drawables.Cards.Buttons;
 using osu.Game.Graphics;
 using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Overlays;
-using osu.Game.Screens.Ranking.Expanded.Accuracy;
+using osu.Framework.Graphics.UserInterface;
 using osuTK;
 using osuTK.Graphics;
 
@@ -30,7 +30,7 @@ namespace osu.Game.Beatmaps.Drawables.Cards
         private readonly UpdateableOnlineBeatmapSetCover cover;
         private readonly Container foreground;
         private readonly PlayButton playButton;
-        private readonly SmoothCircularProgress progress;
+        private readonly CircularProgress progress;
         private readonly Container content;
 
         protected override Container<Drawable> Content => content;
@@ -53,7 +53,7 @@ namespace osu.Game.Beatmaps.Drawables.Cards
                         {
                             RelativeSizeAxes = Axes.Both
                         },
-                        progress = new SmoothCircularProgress
+                        progress = new CircularProgress
                         {
                             Anchor = Anchor.Centre,
                             Origin = Anchor.Centre,

osu.Game/Beatmaps/Drawables/OnlineBeatmapSetCover.cs

@@ -18,8 +18,7 @@ namespace osu.Game.Beatmaps.Drawables
 
         public OnlineBeatmapSetCover(IBeatmapSetOnlineInfo set, BeatmapSetCoverType type = BeatmapSetCoverType.Cover)
         {
-            if (set == null)
-                throw new ArgumentNullException(nameof(set));
+            ArgumentNullException.ThrowIfNull(set);
 
             this.set = set;
             this.type = type;

osu.Game/Beatmaps/Formats/Decoder.cs

@@ -57,8 +57,7 @@ namespace osu.Game.Beatmaps.Formats
         public static Decoder<T> GetDecoder<T>(LineBufferedReader stream)
             where T : new()
         {
-            if (stream == null)
-                throw new ArgumentNullException(nameof(stream));
+            ArgumentNullException.ThrowIfNull(stream);
 
             if (!decoders.TryGetValue(typeof(T), out var typedDecoders))
                 throw new IOException(@"Unknown decoder type");

osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs

@@ -160,7 +160,7 @@ namespace osu.Game.Beatmaps.Formats
                     break;
 
                 case @"SampleSet":
-                    defaultSampleBank = (LegacySampleBank)Enum.Parse(typeof(LegacySampleBank), pair.Value);
+                    defaultSampleBank = Enum.Parse<LegacySampleBank>(pair.Value);
                     break;
 
                 case @"SampleVolume":
@@ -218,7 +218,7 @@ namespace osu.Game.Beatmaps.Formats
                     break;
 
                 case @"Countdown":
-                    beatmap.BeatmapInfo.Countdown = (CountdownType)Enum.Parse(typeof(CountdownType), pair.Value);
+                    beatmap.BeatmapInfo.Countdown = Enum.Parse<CountdownType>(pair.Value);
                     break;
 
                 case @"CountdownOffset":

osu.Game/Beatmaps/Formats/LegacyBeatmapEncoder.cs

@@ -300,7 +300,7 @@ namespace osu.Game.Beatmaps.Formats
             {
                 var comboColour = colours[i];
 
-                writer.Write(FormattableString.Invariant($"Combo{i}: "));
+                writer.Write(FormattableString.Invariant($"Combo{1 + i}: "));
                 writer.Write(FormattableString.Invariant($"{(byte)(comboColour.R * byte.MaxValue)},"));
                 writer.Write(FormattableString.Invariant($"{(byte)(comboColour.G * byte.MaxValue)},"));
                 writer.Write(FormattableString.Invariant($"{(byte)(comboColour.B * byte.MaxValue)},"));

osu.Game/Beatmaps/Formats/LegacyDecoder.cs

@@ -132,13 +132,7 @@ namespace osu.Game.Beatmaps.Formats
 
         protected KeyValuePair<string, string> SplitKeyVal(string line, char separator = ':', bool shouldTrim = true)
         {
-            string[] split = line.Split(separator, 2);
-
-            if (shouldTrim)
-            {
-                for (int i = 0; i < split.Length; i++)
-                    split[i] = split[i].Trim();
-            }
+            string[] split = line.Split(separator, 2, shouldTrim ? StringSplitOptions.TrimEntries : StringSplitOptions.None);
 
             return new KeyValuePair<string, string>
             (

osu.Game/Beatmaps/Formats/LegacyStoryboardDecoder.cs

@@ -301,11 +301,11 @@ namespace osu.Game.Beatmaps.Formats
             }
         }
 
-        private string parseLayer(string value) => Enum.Parse(typeof(LegacyStoryLayer), value).ToString();
+        private string parseLayer(string value) => Enum.Parse<LegacyStoryLayer>(value).ToString();
 
         private Anchor parseOrigin(string value)
         {
-            var origin = (LegacyOrigins)Enum.Parse(typeof(LegacyOrigins), value);
+            var origin = Enum.Parse<LegacyOrigins>(value);
 
             switch (origin)
             {
@@ -343,8 +343,8 @@ 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;
+            var parsed = Enum.Parse<AnimationLoopType>(value);
+            return Enum.IsDefined(parsed) ? parsed : AnimationLoopType.LoopForever;
         }
 
         private void handleVariables(string line)

osu.Game/Beatmaps/IBeatmap.cs

@@ -4,6 +4,7 @@
 #nullable disable
 
 using System.Collections.Generic;
+using System.Linq;
 using osu.Game.Beatmaps.ControlPoints;
 using osu.Game.Beatmaps.Timing;
 using osu.Game.Rulesets.Objects;
@@ -102,5 +103,16 @@ namespace osu.Game.Beatmaps
                     addCombo(nested, ref combo);
             }
         }
+
+        /// <summary>
+        /// Find the absolute end time of the latest <see cref="HitObject"/> in a beatmap. Will throw if beatmap contains no objects.
+        /// </summary>
+        /// <remarks>
+        /// This correctly accounts for rulesets which have concurrent hitobjects which may have durations, causing the .Last() object
+        /// to not necessarily have the latest end time.
+        ///
+        /// It's not super efficient so calls should be kept to a minimum.
+        /// </remarks>
+        public static double GetLastObjectTime(this IBeatmap beatmap) => beatmap.HitObjects.Max(h => h.GetEndTime());
     }
 }

osu.Game/Beatmaps/WorkingBeatmap.cs

@@ -34,8 +34,6 @@ namespace osu.Game.Beatmaps
         // TODO: remove once the fallback lookup is not required (and access via `working.BeatmapInfo.Metadata` directly).
         public BeatmapMetadata Metadata => BeatmapInfo.Metadata;
 
-        public Waveform Waveform => waveform.Value;
-
         public Storyboard Storyboard => storyboard.Value;
 
         public Texture Background => GetBackground(); // Texture uses ref counting, so we want to return a new instance every usage.
@@ -48,10 +46,11 @@ namespace osu.Game.Beatmaps
 
         private readonly object beatmapFetchLock = new object();
 
-        private readonly Lazy<Waveform> waveform;
         private readonly Lazy<Storyboard> storyboard;
         private readonly Lazy<ISkin> skin;
+
         private Track track; // track is not Lazy as we allow transferring and loading multiple times.
+        private Waveform waveform; // waveform is also not Lazy as the track may change.
 
         protected WorkingBeatmap(BeatmapInfo beatmapInfo, AudioManager audioManager)
         {
@@ -60,7 +59,6 @@ namespace osu.Game.Beatmaps
             BeatmapInfo = beatmapInfo;
             BeatmapSetInfo = beatmapInfo.BeatmapSet ?? new BeatmapSetInfo();
 
-            waveform = new Lazy<Waveform>(GetWaveform);
             storyboard = new Lazy<Storyboard>(GetStoryboard);
             skin = new Lazy<ISkin>(GetSkin);
         }
@@ -108,7 +106,16 @@ namespace osu.Game.Beatmaps
 
         public virtual bool TrackLoaded => track != null;
 
-        public Track LoadTrack() => track = GetBeatmapTrack() ?? GetVirtualTrack(1000);
+        public Track LoadTrack()
+        {
+            track = GetBeatmapTrack() ?? GetVirtualTrack(1000);
+
+            // the track may have changed, recycle the current waveform.
+            waveform?.Dispose();
+            waveform = null;
+
+            return track;
+        }
 
         public void PrepareTrackForPreview(bool looping, double offsetFromPreviewPoint = 0)
         {
@@ -171,6 +178,12 @@ namespace osu.Game.Beatmaps
 
         #endregion
 
+        #region Waveform
+
+        public Waveform Waveform => waveform ??= GetWaveform();
+
+        #endregion
+
         #region Beatmap
 
         public virtual bool BeatmapLoaded => beatmapLoadTask?.IsCompleted ?? false;

osu.Game/Beatmaps/WorkingBeatmapCache.cs

@@ -141,6 +141,9 @@ namespace osu.Game.Beatmaps
                 try
                 {
                     string fileStorePath = BeatmapSetInfo.GetPathForFile(BeatmapInfo.Path);
+
+                    // TODO: check validity of file
+
                     var stream = GetStream(fileStorePath);
 
                     if (stream == null)

osu.Game/Configuration/SessionStatics.cs

@@ -19,6 +19,7 @@ namespace osu.Game.Configuration
             SetDefault(Static.LoginOverlayDisplayed, false);
             SetDefault(Static.MutedAudioNotificationShownOnce, false);
             SetDefault(Static.LowBatteryNotificationShownOnce, false);
+            SetDefault(Static.FeaturedArtistDisclaimerShownOnce, false);
             SetDefault(Static.LastHoverSoundPlaybackTime, (double?)null);
             SetDefault<APISeasonalBackgrounds>(Static.SeasonalBackgrounds, null);
         }
@@ -42,6 +43,7 @@ namespace osu.Game.Configuration
         LoginOverlayDisplayed,
         MutedAudioNotificationShownOnce,
         LowBatteryNotificationShownOnce,
+        FeaturedArtistDisclaimerShownOnce,
 
         /// <summary>
         /// Info about seasonal backgrounds available fetched from API - see <see cref="APISeasonalBackgrounds"/>.
@@ -53,6 +55,6 @@ namespace osu.Game.Configuration
         /// The last playback time in milliseconds of a hover sample (from <see cref="HoverSounds"/>).
         /// Used to debounce hover sounds game-wide to avoid volume saturation, especially in scrolling views with many UI controls like <see cref="SettingsOverlay"/>.
         /// </summary>
-        LastHoverSoundPlaybackTime
+        LastHoverSoundPlaybackTime,
     }
 }

osu.Game/Configuration/SettingSourceAttribute.cs

@@ -91,15 +91,15 @@ namespace osu.Game.Configuration
             OrderPosition = orderPosition;
         }
 
-        public int CompareTo(SettingSourceAttribute other)
+        public int CompareTo(SettingSourceAttribute? other)
         {
-            if (OrderPosition == other.OrderPosition)
+            if (OrderPosition == other?.OrderPosition)
                 return 0;
 
             // unordered items come last (are greater than any ordered items).
             if (OrderPosition == null)
                 return 1;
-            if (other.OrderPosition == null)
+            if (other?.OrderPosition == null)
                 return -1;
 
             // ordered items are sorted by the order value.
@@ -113,7 +113,7 @@ namespace osu.Game.Configuration
         {
             foreach (var (attr, property) in obj.GetOrderedSettingsSourceProperties())
             {
-                object value = property.GetValue(obj);
+                object value = property.GetValue(obj)!;
 
                 if (attr.SettingControlType != null)
                 {
@@ -121,7 +121,7 @@ namespace osu.Game.Configuration
                     if (controlType.EnumerateBaseTypes().All(t => !t.IsGenericType || t.GetGenericTypeDefinition() != typeof(SettingsItem<>)))
                         throw new InvalidOperationException($"{nameof(SettingSourceAttribute)} had an unsupported custom control type ({controlType.ReadableName()})");
 
-                    var control = (Drawable)Activator.CreateInstance(controlType);
+                    var control = (Drawable)Activator.CreateInstance(controlType)!;
                     controlType.GetProperty(nameof(SettingsItem<object>.SettingSourceObject))?.SetValue(control, obj);
                     controlType.GetProperty(nameof(SettingsItem<object>.LabelText))?.SetValue(control, attr.Label);
                     controlType.GetProperty(nameof(SettingsItem<object>.TooltipText))?.SetValue(control, attr.Description);
@@ -188,7 +188,7 @@ namespace osu.Game.Configuration
 
                     case IBindable bindable:
                         var dropdownType = typeof(ModSettingsEnumDropdown<>).MakeGenericType(bindable.GetType().GetGenericArguments()[0]);
-                        var dropdown = (Drawable)Activator.CreateInstance(dropdownType);
+                        var dropdown = (Drawable)Activator.CreateInstance(dropdownType)!;
 
                         dropdownType.GetProperty(nameof(SettingsDropdown<object>.LabelText))?.SetValue(dropdown, attr.Label);
                         dropdownType.GetProperty(nameof(SettingsDropdown<object>.TooltipText))?.SetValue(dropdown, attr.Description);
@@ -231,7 +231,7 @@ namespace osu.Game.Configuration
                     // An unknown (e.g. enum) generic type.
                     var valueMethod = u.GetType().GetProperty(nameof(IBindable<int>.Value));
                     Debug.Assert(valueMethod != null);
-                    return valueMethod.GetValue(u);
+                    return valueMethod.GetValue(u)!;
 
                 default:
                     // fall back for non-bindable cases.

osu.Game/Database/ICanAcceptFiles.cs

@@ -31,7 +31,8 @@ namespace osu.Game.Database
         /// This will post notifications tracking progress.
         /// </remarks>
         /// <param name="tasks">The import tasks from which the files should be imported.</param>
-        Task Import(params ImportTask[] tasks);
+        /// <param name="parameters">Parameters to further configure the import process.</param>
+        Task Import(ImportTask[] tasks, ImportParameters parameters = default);
 
         /// <summary>
         /// An array of accepted file extensions (in the standard format of ".abc").

osu.Game/Database/IModelImporter.cs

@@ -20,8 +20,9 @@ namespace osu.Game.Database
         /// </summary>
         /// <param name="notification">The notification to update.</param>
         /// <param name="tasks">The import tasks.</param>
+        /// <param name="parameters">Parameters to further configure the import process.</param>
         /// <returns>The imported models.</returns>
-        Task<IEnumerable<Live<TModel>>> Import(ProgressNotification notification, params ImportTask[] tasks);
+        Task<IEnumerable<Live<TModel>>> Import(ProgressNotification notification, ImportTask[] tasks, ImportParameters parameters = default);
 
         /// <summary>
         /// Process a single import as an update for an existing model.

osu.Game/Database/ImportParameters.cs

@@ -0,0 +1,25 @@
+// 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.
+
+namespace osu.Game.Database
+{
+    public struct ImportParameters
+    {
+        /// <summary>
+        /// Whether this import is part of a larger batch.
+        /// </summary>
+        /// <remarks>
+        /// May skip intensive pre-import checks in favour of faster processing.
+        ///
+        /// More specifically, imports will be skipped before they begin, given an existing model matches on hash and filenames. Should generally only be used for large batch imports, as it may defy user expectations when updating an existing model.
+        ///
+        /// Will also change scheduling behaviour to run at a lower priority.
+        /// </remarks>
+        public bool Batch { get; set; }
+
+        /// <summary>
+        /// Whether this import should use hard links rather than file copy operations if available.
+        /// </summary>
+        public bool PreferHardLinks { get; set; }
+    }
+}

osu.Game/Database/LegacyExporter.cs

@@ -3,9 +3,11 @@
 
 #nullable disable
 
+using System.Collections.Generic;
 using System.IO;
 using osu.Framework.Platform;
 using osu.Game.Extensions;
+using osu.Game.Utils;
 using SharpCompress.Archives.Zip;
 
 namespace osu.Game.Database
@@ -31,14 +33,19 @@ namespace osu.Game.Database
             UserFileStorage = storage.GetStorageForDirectory(@"files");
         }
 
+        protected virtual string GetFilename(TModel item) => item.GetDisplayString();
+
         /// <summary>
         /// Exports an item to a legacy (.zip based) package.
         /// </summary>
         /// <param name="item">The item to export.</param>
         public void Export(TModel item)
         {
-            string filename = $"{item.GetDisplayString().GetValidFilename()}{FileExtension}";
+            string itemFilename = GetFilename(item).GetValidFilename();
 
+            IEnumerable<string> existingExports = exportStorage.GetFiles("", $"{itemFilename}*{FileExtension}");
+
+            string filename = NamingUtils.GetNextBestFilename(existingExports, $"{itemFilename}{FileExtension}");
             using (var stream = exportStorage.CreateFileSafely(filename))
                 ExportModelTo(item, stream);
 

osu.Game/Database/LegacyImportManager.cs

@@ -42,8 +42,8 @@ namespace osu.Game.Database
         [Resolved]
         private RealmAccess realmAccess { get; set; } = null!;
 
-        [Resolved(canBeNull: true)] // canBeNull required while we remain on mono for mobile platforms.
-        private DesktopGameHost? desktopGameHost { get; set; }
+        [Resolved]
+        private GameHost gameHost { get; set; } = null!;
 
         [Resolved]
         private INotificationOverlay? notifications { get; set; }
@@ -52,7 +52,20 @@ namespace osu.Game.Database
 
         public bool SupportsImportFromStable => RuntimeInfo.IsDesktop;
 
-        public void UpdateStorage(string stablePath) => cachedStorage = new StableStorage(stablePath, desktopGameHost);
+        public void UpdateStorage(string stablePath) => cachedStorage = new StableStorage(stablePath, gameHost as DesktopGameHost);
+
+        public bool CheckSongsFolderHardLinkAvailability()
+        {
+            var stableStorage = GetCurrentStableStorage();
+
+            if (stableStorage == null || gameHost is not DesktopGameHost desktopGameHost)
+                return false;
+
+            string testExistingPath = stableStorage.GetSongStorage().GetFullPath(string.Empty);
+            string testDestinationPath = desktopGameHost.Storage.GetFullPath(string.Empty);
+
+            return HardLinkHelper.CheckAvailability(testDestinationPath, testExistingPath);
+        }
 
         public virtual async Task<int> GetImportCount(StableContent content, CancellationToken cancellationToken)
         {
@@ -66,16 +79,16 @@ namespace osu.Game.Database
             switch (content)
             {
                 case StableContent.Beatmaps:
-                    return await new LegacyBeatmapImporter(beatmaps).GetAvailableCount(stableStorage);
+                    return await new LegacyBeatmapImporter(beatmaps).GetAvailableCount(stableStorage).ConfigureAwait(false);
 
                 case StableContent.Skins:
-                    return await new LegacySkinImporter(skins).GetAvailableCount(stableStorage);
+                    return await new LegacySkinImporter(skins).GetAvailableCount(stableStorage).ConfigureAwait(false);
 
                 case StableContent.Collections:
-                    return await new LegacyCollectionImporter(realmAccess).GetAvailableCount(stableStorage);
+                    return await new LegacyCollectionImporter(realmAccess).GetAvailableCount(stableStorage).ConfigureAwait(false);
 
                 case StableContent.Scores:
-                    return await new LegacyScoreImporter(scores).GetAvailableCount(stableStorage);
+                    return await new LegacyScoreImporter(scores).GetAvailableCount(stableStorage).ConfigureAwait(false);
 
                 default:
                     throw new ArgumentException($"Only one {nameof(StableContent)} flag should be specified.");

osu.Game/Database/LegacyModelImporter.cs

@@ -57,7 +57,12 @@ namespace osu.Game.Database
                 return Task.CompletedTask;
             }
 
-            return Task.Run(async () => await Importer.Import(GetStableImportPaths(storage).ToArray()).ConfigureAwait(false));
+            return Task.Run(async () =>
+            {
+                var tasks = GetStableImportPaths(storage).Select(p => new ImportTask(p)).ToArray();
+
+                await Importer.Import(tasks, new ImportParameters { Batch = true, PreferHardLinks = true }).ConfigureAwait(false);
+            });
         }
 
         /// <summary>

osu.Game/Database/LegacyScoreExporter.cs

@@ -20,6 +20,14 @@ namespace osu.Game.Database
         {
         }
 
+        protected override string GetFilename(ScoreInfo score)
+        {
+            string scoreString = score.GetDisplayString();
+            string filename = $"{scoreString} ({score.Date.LocalDateTime:yyyy-MM-dd_HH-mm})";
+
+            return filename;
+        }
+
         public override void ExportModelTo(ScoreInfo model, Stream outputStream)
         {
             var file = model.Files.SingleOrDefault();

osu.Game/Database/Live.cs

@@ -61,6 +61,6 @@ namespace osu.Game.Database
 
         public override int GetHashCode() => HashCode.Combine(ID);
 
-        public override string ToString() => PerformRead(i => i.ToString());
+        public override string? ToString() => PerformRead(i => i.ToString());
     }
 }

osu.Game/Database/ModelDownloader.cs

@@ -71,9 +71,9 @@ namespace osu.Game.Database
                     bool importSuccessful;
 
                     if (originalModel != null)
-                        importSuccessful = (await importer.ImportAsUpdate(notification, new ImportTask(filename), originalModel)) != null;
+                        importSuccessful = (await importer.ImportAsUpdate(notification, new ImportTask(filename), originalModel).ConfigureAwait(false)) != null;
                     else
-                        importSuccessful = (await importer.Import(notification, new ImportTask(filename))).Any();
+                        importSuccessful = (await importer.Import(notification, new[] { new ImportTask(filename) }).ConfigureAwait(false)).Any();
 
                     // for now a failed import will be marked as a failed download for simplicity.
                     if (!importSuccessful)

osu.Game/Database/ModelManager.cs

@@ -18,6 +18,11 @@ namespace osu.Game.Database
     public class ModelManager<TModel> : IModelManager<TModel>, IModelFileManager<TModel, RealmNamedFileUsage>
         where TModel : RealmObject, IHasRealmFiles, IHasGuidPrimaryKey, ISoftDelete
     {
+        /// <summary>
+        /// Temporarily pause imports to avoid performance overheads affecting gameplay scenarios.
+        /// </summary>
+        public virtual bool PauseImports { get; set; }
+
         protected RealmAccess Realm { get; }
 
         private readonly RealmFileStore realmFileStore;

osu.Game/Database/RealmAccess.cs

@@ -481,7 +481,7 @@ namespace osu.Game.Database
                 // server, which we don't use. May want to report upstream or revisit in the future.
                 using (var realm = getRealmInstance())
                     // ReSharper disable once AccessToDisposedClosure (WriteAsync should be marked as [InstantHandle]).
-                    await realm.WriteAsync(() => action(realm));
+                    await realm.WriteAsync(() => action(realm)).ConfigureAwait(false);
 
                 pendingAsyncWrites.Signal();
             });
@@ -558,7 +558,7 @@ namespace osu.Game.Database
 
                 return new InvokeOnDisposal(() => model.PropertyChanged -= onPropertyChanged);
 
-                void onPropertyChanged(object sender, PropertyChangedEventArgs args)
+                void onPropertyChanged(object? sender, PropertyChangedEventArgs args)
                 {
                     if (args.PropertyName == propertyName)
                         onChanged(propLookupCompiled(model));

osu.Game/Database/RealmArchiveModelImporter.cs

@@ -56,6 +56,11 @@ namespace osu.Game.Database
         /// </summary>
         private static readonly ThreadedTaskScheduler import_scheduler_batch = new ThreadedTaskScheduler(import_queue_request_concurrency, nameof(RealmArchiveModelImporter<TModel>));
 
+        /// <summary>
+        /// Temporarily pause imports to avoid performance overheads affecting gameplay scenarios.
+        /// </summary>
+        public bool PauseImports { get; set; }
+
         public abstract IEnumerable<string> HandledExtensions { get; }
 
         protected readonly RealmFileStore Files;
@@ -81,16 +86,16 @@ namespace osu.Game.Database
 
         public Task Import(params string[] paths) => Import(paths.Select(p => new ImportTask(p)).ToArray());
 
-        public Task Import(params ImportTask[] tasks)
+        public Task Import(ImportTask[] tasks, ImportParameters parameters = default)
         {
             var notification = new ProgressNotification { State = ProgressNotificationState.Active };
 
             PostNotification?.Invoke(notification);
 
-            return Import(notification, tasks);
+            return Import(notification, tasks, parameters);
         }
 
-        public async Task<IEnumerable<Live<TModel>>> Import(ProgressNotification notification, params ImportTask[] tasks)
+        public async Task<IEnumerable<Live<TModel>>> Import(ProgressNotification notification, ImportTask[] tasks, ImportParameters parameters = default)
         {
             if (tasks.Length == 0)
             {
@@ -106,7 +111,7 @@ namespace osu.Game.Database
 
             var imported = new List<Live<TModel>>();
 
-            bool isBatchImport = tasks.Length >= minimum_items_considered_batch_import;
+            parameters.Batch |= tasks.Length >= minimum_items_considered_batch_import;
 
             await Task.WhenAll(tasks.Select(async task =>
             {
@@ -115,7 +120,7 @@ namespace osu.Game.Database
 
                 try
                 {
-                    var model = await Import(task, isBatchImport, notification.CancellationToken).ConfigureAwait(false);
+                    var model = await Import(task, parameters, notification.CancellationToken).ConfigureAwait(false);
 
                     lock (imported)
                     {
@@ -149,9 +154,12 @@ namespace osu.Game.Database
             }
             else
             {
-                notification.CompletionText = imported.Count == 1
-                    ? $"Imported {imported.First().GetDisplayString()}!"
-                    : $"Imported {imported.Count} {HumanisedModelName}s!";
+                if (tasks.Length > imported.Count)
+                    notification.CompletionText = $"Imported {imported.Count} of {tasks.Length} {HumanisedModelName}s.";
+                else if (imported.Count > 1)
+                    notification.CompletionText = $"Imported {imported.Count} {HumanisedModelName}s!";
+                else
+                    notification.CompletionText = $"Imported {imported.First().GetDisplayString()}!";
 
                 if (imported.Count > 0 && PresentImport != null)
                 {
@@ -176,16 +184,16 @@ namespace osu.Game.Database
         /// Note that this bypasses the UI flow and should only be used for special cases or testing.
         /// </summary>
         /// <param name="task">The <see cref="ImportTask"/> containing data about the <typeparamref name="TModel"/> to import.</param>
-        /// <param name="batchImport">Whether this import is part of a larger batch.</param>
+        /// <param name="parameters">Parameters to further configure the import process.</param>
         /// <param name="cancellationToken">An optional cancellation token.</param>
         /// <returns>The imported model, if successful.</returns>
-        public async Task<Live<TModel>?> Import(ImportTask task, bool batchImport = false, CancellationToken cancellationToken = default)
+        public async Task<Live<TModel>?> Import(ImportTask task, ImportParameters parameters = default, CancellationToken cancellationToken = default)
         {
             cancellationToken.ThrowIfCancellationRequested();
 
             Live<TModel>? import;
             using (ArchiveReader reader = task.GetReader())
-                import = await importFromArchive(reader, batchImport, cancellationToken).ConfigureAwait(false);
+                import = await importFromArchive(reader, parameters, cancellationToken).ConfigureAwait(false);
 
             // We may or may not want to delete the file depending on where it is stored.
             //  e.g. reconstructing/repairing database with items from default storage.
@@ -211,9 +219,9 @@ namespace osu.Game.Database
         /// This method also handled queueing the import task on a relevant import thread pool.
         /// </remarks>
         /// <param name="archive">The archive to be imported.</param>
-        /// <param name="batchImport">Whether this import is part of a larger batch.</param>
+        /// <param name="parameters">Parameters to further configure the import process.</param>
         /// <param name="cancellationToken">An optional cancellation token.</param>
-        private async Task<Live<TModel>?> importFromArchive(ArchiveReader archive, bool batchImport = false, CancellationToken cancellationToken = default)
+        private async Task<Live<TModel>?> importFromArchive(ArchiveReader archive, ImportParameters parameters = default, CancellationToken cancellationToken = default)
         {
             cancellationToken.ThrowIfCancellationRequested();
 
@@ -236,10 +244,10 @@ namespace osu.Game.Database
                 return null;
             }
 
-            var scheduledImport = Task.Factory.StartNew(() => ImportModel(model, archive, batchImport, cancellationToken),
+            var scheduledImport = Task.Factory.StartNew(() => ImportModel(model, archive, parameters, cancellationToken),
                 cancellationToken,
                 TaskCreationOptions.HideScheduler,
-                batchImport ? import_scheduler_batch : import_scheduler);
+                parameters.Batch ? import_scheduler_batch : import_scheduler);
 
             return await scheduledImport.ConfigureAwait(false);
         }
@@ -249,15 +257,15 @@ namespace osu.Game.Database
         /// </summary>
         /// <param name="item">The model to be imported.</param>
         /// <param name="archive">An optional archive to use for model population.</param>
-        /// <param name="batchImport">If <c>true</c>, imports will be skipped before they begin, given an existing model matches on hash and filenames. Should generally only be used for large batch imports, as it may defy user expectations when updating an existing model.</param>
+        /// <param name="parameters">Parameters to further configure the import process.</param>
         /// <param name="cancellationToken">An optional cancellation token.</param>
-        public virtual Live<TModel>? ImportModel(TModel item, ArchiveReader? archive = null, bool batchImport = false, CancellationToken cancellationToken = default) => Realm.Run(realm =>
+        public virtual Live<TModel>? ImportModel(TModel item, ArchiveReader? archive = null, ImportParameters parameters = default, CancellationToken cancellationToken = default) => Realm.Run(realm =>
         {
-            cancellationToken.ThrowIfCancellationRequested();
+            pauseIfNecessary(cancellationToken);
 
             TModel? existing;
 
-            if (batchImport && archive != null)
+            if (parameters.Batch && archive != null)
             {
                 // this is a fast bail condition to improve large import performance.
                 item.Hash = computeHashFast(archive);
@@ -303,7 +311,7 @@ namespace osu.Game.Database
                     foreach (var filenames in getShortenedFilenames(archive))
                     {
                         using (Stream s = archive.GetStream(filenames.original))
-                            files.Add(new RealmNamedFileUsage(Files.Add(s, realm, false), filenames.shortened));
+                            files.Add(new RealmNamedFileUsage(Files.Add(s, realm, false, parameters.PreferHardLinks), filenames.shortened));
                     }
                 }
 
@@ -358,7 +366,7 @@ namespace osu.Game.Database
                     // import to store
                     realm.Add(item);
 
-                    PostImport(item, realm, batchImport);
+                    PostImport(item, realm, parameters);
 
                     transaction.Commit();
                 }
@@ -493,8 +501,8 @@ namespace osu.Game.Database
         /// </summary>
         /// <param name="model">The model prepared for import.</param>
         /// <param name="realm">The current realm context.</param>
-        /// <param name="batchImport">Whether the import was part of a batch.</param>
-        protected virtual void PostImport(TModel model, Realm realm, bool batchImport)
+        /// <param name="parameters">Parameters to further configure the import process.</param>
+        protected virtual void PostImport(TModel model, Realm realm, ImportParameters parameters)
         {
         }
 
@@ -551,6 +559,23 @@ namespace osu.Game.Database
         /// <returns>Whether to perform deletion.</returns>
         protected virtual bool ShouldDeleteArchive(string path) => false;
 
+        private void pauseIfNecessary(CancellationToken cancellationToken)
+        {
+            if (!PauseImports)
+                return;
+
+            Logger.Log($@"{GetType().Name} is being paused.");
+
+            while (PauseImports)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+                Thread.Sleep(500);
+            }
+
+            cancellationToken.ThrowIfCancellationRequested();
+            Logger.Log($@"{GetType().Name} is being resumed.");
+        }
+
         private IEnumerable<string> getIDs(IEnumerable<INamedFile> files)
         {
             foreach (var f in files.OrderBy(f => f.Filename))

osu.Game/Database/RealmFileStore.cs

@@ -10,6 +10,7 @@ using osu.Framework.Logging;
 using osu.Framework.Platform;
 using osu.Framework.Testing;
 using osu.Game.Extensions;
+using osu.Game.IO;
 using osu.Game.Models;
 using Realms;
 
@@ -41,7 +42,8 @@ namespace osu.Game.Database
         /// <param name="data">The file data stream.</param>
         /// <param name="realm">The realm instance to add to. Should already be in a transaction.</param>
         /// <param name="addToRealm">Whether the <see cref="RealmFile"/> should immediately be added to the underlying realm. If <c>false</c> is provided here, the instance must be manually added.</param>
-        public RealmFile Add(Stream data, Realm realm, bool addToRealm = true)
+        /// <param name="preferHardLinks">Whether this import should use hard links rather than file copy operations if available.</param>
+        public RealmFile Add(Stream data, Realm realm, bool addToRealm = true, bool preferHardLinks = false)
         {
             string hash = data.ComputeSHA2Hash();
 
@@ -50,7 +52,7 @@ namespace osu.Game.Database
             var file = existing ?? new RealmFile { Hash = hash };
 
             if (!checkFileExistsAndMatchesHash(file))
-                copyToStore(file, data);
+                copyToStore(file, data, preferHardLinks);
 
             if (addToRealm && !file.IsManaged)
                 realm.Add(file);
@@ -58,8 +60,15 @@ namespace osu.Game.Database
             return file;
         }
 
-        private void copyToStore(RealmFile file, Stream data)
+        private void copyToStore(RealmFile file, Stream data, bool preferHardLinks)
         {
+            if (data is FileStream fs && preferHardLinks)
+            {
+                // attempt to do a fast hard link rather than copy.
+                if (HardLinkHelper.TryCreateHardLink(Storage.GetFullPath(file.GetStoragePath(), true), fs.Name))
+                    return;
+            }
+
             data.Seek(0, SeekOrigin.Begin);
 
             using (var output = Storage.CreateFileSafely(file.GetStoragePath()))

osu.Game/Extensions/DrawableExtensions.cs

@@ -66,10 +66,10 @@ namespace osu.Game.Extensions
 
                 foreach (var (_, property) in component.GetSettingsSourceProperties())
                 {
-                    if (!info.Settings.TryGetValue(property.Name.ToSnakeCase(), out object settingValue))
+                    if (!info.Settings.TryGetValue(property.Name.ToSnakeCase(), out object? settingValue))
                         continue;
 
-                    skinnable.CopyAdjustedSetting((IBindable)property.GetValue(component), settingValue);
+                    skinnable.CopyAdjustedSetting(((IBindable)property.GetValue(component)!), settingValue);
                 }
             }
 

osu.Game/Extensions/TaskExtensions.cs

@@ -37,7 +37,7 @@ namespace osu.Game.Extensions
 
                 if (cancellationToken.IsCancellationRequested)
                 {
-                    tcs.SetCanceled();
+                    tcs.SetCanceled(cancellationToken);
                 }
                 else
                 {

osu.Game/Graphics/Containers/LogoTrackingContainer.cs

@@ -36,8 +36,7 @@ namespace osu.Game.Graphics.Containers
         /// <param name="easing">The easing type of the initial transform.</param>
         public void StartTracking(OsuLogo logo, double duration = 0, Easing easing = Easing.None)
         {
-            if (logo == null)
-                throw new ArgumentNullException(nameof(logo));
+            ArgumentNullException.ThrowIfNull(logo);
 
             if (logo.IsTracking && Logo == null)
                 throw new InvalidOperationException($"Cannot track an instance of {typeof(OsuLogo)} to multiple {typeof(LogoTrackingContainer)}s");

osu.Game/Graphics/Containers/Markdown/Extensions/BlockAttributeExtension.cs

@@ -0,0 +1,34 @@
+// 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 Markdig;
+using Markdig.Extensions.GenericAttributes;
+using Markdig.Renderers;
+using Markdig.Syntax;
+
+namespace osu.Game.Graphics.Containers.Markdown.Extensions
+{
+    /// <summary>
+    /// A variant of <see cref="Markdig.Extensions.GenericAttributes.GenericAttributesExtension"/>
+    /// which only handles generic attributes in the current markdown <see cref="Block"/> and ignores inline generic attributes.
+    /// </summary>
+    /// <remarks>
+    /// For rationale, see implementation of <see cref="Setup(Markdig.MarkdownPipelineBuilder)"/>.
+    /// </remarks>
+    public class BlockAttributeExtension : IMarkdownExtension
+    {
+        private readonly GenericAttributesExtension genericAttributesExtension = new GenericAttributesExtension();
+
+        public void Setup(MarkdownPipelineBuilder pipeline)
+        {
+            genericAttributesExtension.Setup(pipeline);
+
+            // GenericAttributesExtension registers a GenericAttributesParser in pipeline.InlineParsers.
+            // this conflicts with the CustomContainerExtension, leading to some custom containers (e.g. flags) not displaying.
+            // as a workaround, remove the inline parser here before it can do damage.
+            pipeline.InlineParsers.RemoveAll(parser => parser is GenericAttributesParser);
+        }
+
+        public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer) => genericAttributesExtension.Setup(pipeline, renderer);
+    }
+}

osu.Game/Graphics/Containers/Markdown/Extensions/OsuMarkdownExtensions.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 Markdig;
+
+namespace osu.Game.Graphics.Containers.Markdown.Extensions
+{
+    public static class OsuMarkdownExtensions
+    {
+        /// <summary>
+        /// Uses the block attributes extension.
+        /// </summary>
+        /// <param name="pipeline">The pipeline.</param>
+        /// <returns>The modified pipeline.</returns>
+        public static MarkdownPipelineBuilder UseBlockAttributes(this MarkdownPipelineBuilder pipeline)
+        {
+            pipeline.Extensions.AddIfNotAlready<BlockAttributeExtension>();
+            return pipeline;
+        }
+    }
+}

osu.Game/Graphics/Containers/Markdown/Footnotes/OsuMarkdownFootnote.cs

@@ -0,0 +1,30 @@
+// 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 Markdig.Extensions.Footnotes;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers.Markdown;
+using osu.Framework.Graphics.Containers.Markdown.Footnotes;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Localisation;
+
+namespace osu.Game.Graphics.Containers.Markdown.Footnotes
+{
+    public partial class OsuMarkdownFootnote : MarkdownFootnote
+    {
+        public OsuMarkdownFootnote(Footnote footnote)
+            : base(footnote)
+        {
+        }
+
+        public override SpriteText CreateOrderMarker(int order) => CreateSpriteText().With(marker =>
+        {
+            marker.Text = LocalisableString.Format("{0}.", order);
+        });
+
+        public override MarkdownTextFlowContainer CreateTextFlow() => base.CreateTextFlow().With(textFlow =>
+        {
+            textFlow.Margin = new MarginPadding { Left = 30 };
+        });
+    }
+}

osu.Game/Graphics/Containers/Markdown/Footnotes/OsuMarkdownFootnoteBacklink.cs

@@ -0,0 +1,62 @@
+// 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 Markdig.Extensions.Footnotes;
+using osu.Framework.Allocation;
+using osu.Framework.Extensions.IEnumerableExtensions;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers.Markdown;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Testing;
+using osu.Game.Overlays;
+using osuTK;
+
+namespace osu.Game.Graphics.Containers.Markdown.Footnotes
+{
+    public partial class OsuMarkdownFootnoteBacklink : OsuHoverContainer
+    {
+        private readonly FootnoteLink backlink;
+
+        private SpriteIcon spriteIcon = null!;
+
+        [Resolved]
+        private IMarkdownTextComponent parentTextComponent { get; set; } = null!;
+
+        protected override IEnumerable<Drawable> EffectTargets => spriteIcon.Yield();
+
+        public OsuMarkdownFootnoteBacklink(FootnoteLink backlink)
+        {
+            this.backlink = backlink;
+        }
+
+        [BackgroundDependencyLoader(true)]
+        private void load(OverlayColourProvider colourProvider, OsuMarkdownContainer markdownContainer, OverlayScrollContainer? scrollContainer)
+        {
+            float fontSize = parentTextComponent.CreateSpriteText().Font.Size;
+            Size = new Vector2(fontSize);
+
+            IdleColour = colourProvider.Light2;
+            HoverColour = colourProvider.Light1;
+
+            Add(spriteIcon = new SpriteIcon
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                Margin = new MarginPadding { Left = 5 },
+                Size = new Vector2(fontSize / 2),
+                Icon = FontAwesome.Solid.ArrowUp,
+            });
+
+            if (scrollContainer != null)
+            {
+                Action = () =>
+                {
+                    var footnoteLink = markdownContainer.ChildrenOfType<OsuMarkdownFootnoteLink>().Single(footnoteLink => footnoteLink.FootnoteLink.Index == backlink.Index);
+                    scrollContainer.ScrollIntoView(footnoteLink);
+                };
+            }
+        }
+    }
+}

osu.Game/Graphics/Containers/Markdown/Footnotes/OsuMarkdownFootnoteLink.cs

@@ -0,0 +1,80 @@
+// 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 Markdig.Extensions.Footnotes;
+using osu.Framework.Allocation;
+using osu.Framework.Extensions.IEnumerableExtensions;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers.Markdown;
+using osu.Framework.Graphics.Cursor;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Localisation;
+using osu.Framework.Testing;
+using osu.Game.Overlays;
+
+namespace osu.Game.Graphics.Containers.Markdown.Footnotes
+{
+    public partial class OsuMarkdownFootnoteLink : OsuHoverContainer, IHasCustomTooltip
+    {
+        public readonly FootnoteLink FootnoteLink;
+
+        private SpriteText spriteText = null!;
+
+        [Resolved]
+        private IMarkdownTextComponent parentTextComponent { get; set; } = null!;
+
+        [Resolved]
+        private OverlayColourProvider colourProvider { get; set; } = null!;
+
+        [Resolved]
+        private OsuMarkdownContainer markdownContainer { get; set; } = null!;
+
+        protected override IEnumerable<Drawable> EffectTargets => spriteText.Yield();
+
+        public OsuMarkdownFootnoteLink(FootnoteLink footnoteLink)
+        {
+            FootnoteLink = footnoteLink;
+
+            AutoSizeAxes = Axes.Both;
+        }
+
+        [BackgroundDependencyLoader(true)]
+        private void load(OsuMarkdownContainer markdownContainer, OverlayScrollContainer? scrollContainer)
+        {
+            IdleColour = colourProvider.Light2;
+            HoverColour = colourProvider.Light1;
+
+            spriteText = parentTextComponent.CreateSpriteText();
+
+            Add(spriteText.With(t =>
+            {
+                float baseSize = t.Font.Size;
+                t.Font = t.Font.With(size: baseSize * 0.58f);
+                t.Margin = new MarginPadding { Bottom = 0.33f * baseSize };
+                t.Text = LocalisableString.Format("[{0}]", FootnoteLink.Index);
+            }));
+
+            if (scrollContainer != null)
+            {
+                Action = () =>
+                {
+                    var footnote = markdownContainer.ChildrenOfType<OsuMarkdownFootnote>().Single(footnote => footnote.Footnote.Label == FootnoteLink.Footnote.Label);
+                    scrollContainer.ScrollIntoView(footnote);
+                };
+            }
+        }
+
+        public object TooltipContent
+        {
+            get
+            {
+                var span = FootnoteLink.Footnote.LastChild.Span;
+                return markdownContainer.Text.Substring(span.Start, span.Length);
+            }
+        }
+
+        public ITooltip GetCustomTooltip() => new OsuMarkdownFootnoteTooltip(colourProvider);
+    }
+}

osu.Game/Graphics/Containers/Markdown/Footnotes/OsuMarkdownFootnoteTooltip.cs

@@ -0,0 +1,76 @@
+// 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 Markdig.Extensions.Footnotes;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Containers.Markdown;
+using osu.Framework.Graphics.Cursor;
+using osu.Framework.Graphics.Shapes;
+using osu.Game.Overlays;
+using osuTK;
+
+namespace osu.Game.Graphics.Containers.Markdown.Footnotes
+{
+    public partial class OsuMarkdownFootnoteTooltip : CompositeDrawable, ITooltip
+    {
+        private readonly FootnoteMarkdownContainer markdownContainer;
+
+        [Cached]
+        private OverlayColourProvider colourProvider;
+
+        public OsuMarkdownFootnoteTooltip(OverlayColourProvider colourProvider)
+        {
+            this.colourProvider = colourProvider;
+
+            Masking = true;
+            Width = 200;
+            AutoSizeAxes = Axes.Y;
+            CornerRadius = 4;
+
+            InternalChildren = new Drawable[]
+            {
+                new Box
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    Colour = colourProvider.Background6
+                },
+                markdownContainer = new FootnoteMarkdownContainer
+                {
+                    RelativeSizeAxes = Axes.X,
+                    AutoSizeAxes = Axes.Y,
+                    DocumentMargin = new MarginPadding(),
+                    DocumentPadding = new MarginPadding { Horizontal = 10, Vertical = 5 }
+                }
+            };
+        }
+
+        public void Move(Vector2 pos) => Position = pos;
+
+        public void SetContent(object content) => markdownContainer.SetContent((string)content);
+
+        private partial class FootnoteMarkdownContainer : OsuMarkdownContainer
+        {
+            private string? lastFootnote;
+
+            public void SetContent(string footnote)
+            {
+                if (footnote == lastFootnote)
+                    return;
+
+                lastFootnote = Text = footnote;
+            }
+
+            public override MarkdownTextFlowContainer CreateTextFlow() => new FootnoteMarkdownTextFlowContainer();
+        }
+
+        private partial class FootnoteMarkdownTextFlowContainer : OsuMarkdownTextFlowContainer
+        {
+            protected override void AddFootnoteBacklink(FootnoteLink footnoteBacklink)
+            {
+                // we don't want footnote backlinks to show up in tooltips.
+            }
+        }
+    }
+}

osu.Game/Graphics/Containers/Markdown/OsuMarkdownContainer.cs

@@ -4,41 +4,25 @@
 #nullable disable
 
 using Markdig;
-using Markdig.Extensions.AutoLinks;
-using Markdig.Extensions.CustomContainers;
-using Markdig.Extensions.EmphasisExtras;
 using Markdig.Extensions.Footnotes;
 using Markdig.Extensions.Tables;
 using Markdig.Extensions.Yaml;
 using Markdig.Syntax;
+using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Containers.Markdown;
+using osu.Framework.Graphics.Containers.Markdown.Footnotes;
 using osu.Framework.Graphics.Sprites;
+using osu.Game.Graphics.Containers.Markdown.Footnotes;
 using osu.Game.Graphics.Sprites;
+using osuTK;
 
 namespace osu.Game.Graphics.Containers.Markdown
 {
+    [Cached]
     public partial class OsuMarkdownContainer : MarkdownContainer
     {
-        /// <summary>
-        /// Allows this markdown container to parse and link footnotes.
-        /// </summary>
-        /// <seealso cref="FootnoteExtension"/>
-        protected virtual bool Footnotes => false;
-
-        /// <summary>
-        /// Allows this markdown container to make URL text clickable.
-        /// </summary>
-        /// <seealso cref="AutoLinkExtension"/>
-        protected virtual bool Autolinks => false;
-
-        /// <summary>
-        /// Allows this markdown container to parse custom containers (used for flags and infoboxes).
-        /// </summary>
-        /// <seealso cref="CustomContainerExtension"/>
-        protected virtual bool CustomContainers => false;
-
         public OsuMarkdownContainer()
         {
             LineSpacing = 21;
@@ -99,25 +83,17 @@ namespace osu.Game.Graphics.Containers.Markdown
             return new OsuMarkdownUnorderedListItem(level);
         }
 
-        // reference: https://github.com/ppy/osu-web/blob/05488a96b25b5a09f2d97c54c06dd2bae59d1dc8/app/Libraries/Markdown/OsuMarkdown.php#L301
-        protected override MarkdownPipeline CreateBuilder()
-        {
-            var pipeline = new MarkdownPipelineBuilder()
-                           .UseAutoIdentifiers()
-                           .UsePipeTables()
-                           .UseEmphasisExtras(EmphasisExtraOptions.Strikethrough)
-                           .UseYamlFrontMatter();
+        protected override MarkdownFootnoteGroup CreateFootnoteGroup(FootnoteGroup footnoteGroup) => base.CreateFootnoteGroup(footnoteGroup).With(g => g.Spacing = new Vector2(5));
 
-            if (Footnotes)
-                pipeline = pipeline.UseFootnotes();
+        protected override MarkdownFootnote CreateFootnote(Footnote footnote) => new OsuMarkdownFootnote(footnote);
 
-            if (Autolinks)
-                pipeline = pipeline.UseAutoLinks();
+        protected sealed override MarkdownPipeline CreateBuilder()
+            => Options.BuildPipeline();
 
-            if (CustomContainers)
-                pipeline.UseCustomContainers();
-
-            return pipeline.Build();
-        }
+        /// <summary>
+        /// Creates a <see cref="OsuMarkdownContainerOptions"/> instance which is used to determine
+        /// which CommonMark/Markdig extensions should be enabled for this <see cref="OsuMarkdownContainer"/>.
+        /// </summary>
+        protected virtual OsuMarkdownContainerOptions Options => new OsuMarkdownContainerOptions();
     }
 }

osu.Game/Graphics/Containers/Markdown/OsuMarkdownContainerOptions.cs

@@ -0,0 +1,71 @@
+// 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 Markdig;
+using Markdig.Extensions.AutoLinks;
+using Markdig.Extensions.CustomContainers;
+using Markdig.Extensions.EmphasisExtras;
+using Markdig.Extensions.Footnotes;
+using osu.Game.Graphics.Containers.Markdown.Extensions;
+
+namespace osu.Game.Graphics.Containers.Markdown
+{
+    /// <summary>
+    /// Groups options of customising the set of available extensions to <see cref="OsuMarkdownContainer"/> instances.
+    /// </summary>
+    public class OsuMarkdownContainerOptions
+    {
+        /// <summary>
+        /// Allows the <see cref="OsuMarkdownContainer"/> to parse and link footnotes.
+        /// </summary>
+        /// <seealso cref="FootnoteExtension"/>
+        public bool Footnotes { get; init; }
+
+        /// <summary>
+        /// Allows the <see cref="OsuMarkdownContainer"/> container to make URL text clickable.
+        /// </summary>
+        /// <seealso cref="AutoLinkExtension"/>
+        public bool Autolinks { get; init; }
+
+        /// <summary>
+        /// Allows the <see cref="OsuMarkdownContainer"/> to parse custom containers (used for flags and infoboxes).
+        /// </summary>
+        /// <seealso cref="CustomContainerExtension"/>
+        public bool CustomContainers { get; init; }
+
+        /// <summary>
+        /// Allows the <see cref="OsuMarkdownContainer"/> to parse custom attributes in block elements (used e.g. for custom anchor names in the wiki).
+        /// </summary>
+        /// <seealso cref="BlockAttributeExtension"/>
+        public bool BlockAttributes { get; init; }
+
+        /// <summary>
+        /// Returns a prepared <see cref="MarkdownPipeline"/> according to the options specified by the current <see cref="OsuMarkdownContainerOptions"/> instance.
+        /// </summary>
+        /// <remarks>
+        /// Compare: https://github.com/ppy/osu-web/blob/05488a96b25b5a09f2d97c54c06dd2bae59d1dc8/app/Libraries/Markdown/OsuMarkdown.php#L301
+        /// </remarks>
+        public MarkdownPipeline BuildPipeline()
+        {
+            var pipeline = new MarkdownPipelineBuilder()
+                           .UseAutoIdentifiers()
+                           .UsePipeTables()
+                           .UseEmphasisExtras(EmphasisExtraOptions.Strikethrough)
+                           .UseYamlFrontMatter();
+
+            if (Footnotes)
+                pipeline = pipeline.UseFootnotes();
+
+            if (Autolinks)
+                pipeline = pipeline.UseAutoLinks();
+
+            if (CustomContainers)
+                pipeline = pipeline.UseCustomContainers();
+
+            if (BlockAttributes)
+                pipeline = pipeline.UseBlockAttributes();
+
+            return pipeline.Build();
+        }
+    }
+}

osu.Game/Graphics/Containers/Markdown/OsuMarkdownTextFlowContainer.cs

@@ -6,6 +6,7 @@
 using System;
 using System.Linq;
 using Markdig.Extensions.CustomContainers;
+using Markdig.Extensions.Footnotes;
 using Markdig.Syntax.Inlines;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
@@ -13,6 +14,7 @@ using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Containers.Markdown;
 using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
+using osu.Game.Graphics.Containers.Markdown.Footnotes;
 using osu.Game.Overlays;
 using osu.Game.Users;
 using osu.Game.Users.Drawables;
@@ -36,6 +38,10 @@ namespace osu.Game.Graphics.Containers.Markdown
             Text = codeInline.Content
         });
 
+        protected override void AddFootnoteLink(FootnoteLink footnoteLink) => AddDrawable(new OsuMarkdownFootnoteLink(footnoteLink));
+
+        protected override void AddFootnoteBacklink(FootnoteLink footnoteBacklink) => AddDrawable(new OsuMarkdownFootnoteBacklink(footnoteBacklink));
+
         protected override SpriteText CreateEmphasisedSpriteText(bool bold, bool italic)
             => CreateSpriteText().With(t => t.Font = t.Font.With(weight: bold ? FontWeight.Bold : FontWeight.Regular, italics: italic));
 

osu.Game/Graphics/Containers/OsuClickableContainer.cs

@@ -1,14 +1,14 @@
 // 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 disable
-
+using System;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Cursor;
 using osu.Framework.Localisation;
 using osu.Game.Graphics.UserInterface;
+using osuTK;
 
 namespace osu.Game.Graphics.Containers
 {
@@ -18,6 +18,12 @@ namespace osu.Game.Graphics.Containers
 
         private readonly Container content = new Container { RelativeSizeAxes = Axes.Both };
 
+        public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) =>
+            // base call is checked for cases when `OsuClickableContainer` has masking applied to it directly (ie. externally in object initialisation).
+            base.ReceivePositionalInputAt(screenSpacePos)
+            // Implementations often apply masking / edge rounding at a content level, so it's imperative to check that as well.
+            && Content.ReceivePositionalInputAt(screenSpacePos);
+
         protected override Container<Drawable> Content => content;
 
         protected virtual HoverSounds CreateHoverSounds(HoverSampleSet sampleSet) => new HoverClickSounds(sampleSet) { Enabled = { BindTarget = Enabled } };
@@ -38,11 +44,11 @@ namespace osu.Game.Graphics.Containers
                 content.AutoSizeAxes = AutoSizeAxes;
             }
 
-            InternalChildren = new Drawable[]
-            {
-                content,
-                CreateHoverSounds(sampleSet)
-            };
+            AddInternal(content);
+            Add(CreateHoverSounds(sampleSet));
         }
+
+        protected override void ClearInternal(bool disposeChildren = true) =>
+            throw new InvalidOperationException($"Clearing {nameof(InternalChildren)} will cause critical failure. Use {nameof(Clear)} instead.");
     }
 }

osu.Game/Graphics/Containers/OsuFocusedOverlayContainer.cs

@@ -25,8 +25,6 @@ namespace osu.Game.Graphics.Containers
         protected virtual string PopInSampleName => "UI/overlay-pop-in";
         protected virtual string PopOutSampleName => "UI/overlay-pop-out";
 
-        protected override bool BlockScrollInput => false;
-
         protected override bool BlockNonPositionalInput => true;
 
         /// <summary>
@@ -90,6 +88,15 @@ namespace osu.Game.Graphics.Containers
             base.OnMouseUp(e);
         }
 
+        protected override bool OnScroll(ScrollEvent e)
+        {
+            // allow for controlling volume when alt is held.
+            // mostly for compatibility with osu-stable.
+            if (e.AltPressed) return false;
+
+            return true;
+        }
+
         public virtual bool OnPressed(KeyBindingPressEvent<GlobalAction> e)
         {
             if (e.Repeat)

osu.Game/Graphics/Containers/SectionsContainer.cs

@@ -240,7 +240,9 @@ namespace osu.Game.Graphics.Containers
                 headerBackgroundContainer.Height = expandableHeaderSize + fixedHeaderSize;
                 headerBackgroundContainer.Y = ExpandableHeader?.Y ?? 0;
 
-                float smallestSectionHeight = Children.Count > 0 ? Children.Min(d => d.Height) : 0;
+                var flowChildren = scrollContentContainer.FlowingChildren.OfType<T>();
+
+                float smallestSectionHeight = flowChildren.Any() ? flowChildren.Min(d => d.Height) : 0;
 
                 // 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
@@ -249,7 +251,7 @@ namespace osu.Game.Graphics.Containers
 
                 float scrollCentre = fixedHeaderSize + scrollContainer.DisplayableContent * scroll_y_centre + selectionLenienceAboveSection;
 
-                var presentChildren = Children.Where(c => c.IsPresent);
+                var presentChildren = flowChildren.Where(c => c.IsPresent);
 
                 if (lastClickedSection != null)
                     SelectedSection.Value = lastClickedSection;

osu.Game/Graphics/Cursor/MenuCursorContainer.cs

@@ -234,7 +234,7 @@ namespace osu.Game.Graphics.Cursor
             SampleChannel channel = tapSample.GetChannel();
 
             // Scale to [-0.75, 0.75] so that the sample isn't fully panned left or right (sounds weird)
-            channel.Balance.Value = ((activeCursor.X / DrawWidth) * 2 - 1) * 0.75;
+            channel.Balance.Value = ((activeCursor.X / DrawWidth) * 2 - 1) * OsuGameBase.SFX_STEREO_STRENGTH;
             channel.Frequency.Value = baseFrequency - (random_range / 2f) + RNG.NextDouble(random_range);
             channel.Volume.Value = baseFrequency;
 

osu.Game/Graphics/DateTooltip.cs

@@ -9,6 +9,7 @@ using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Cursor;
 using osu.Framework.Graphics.Shapes;
+using osu.Framework.Localisation;
 using osu.Game.Graphics.Sprites;
 using osuTK;
 
@@ -69,8 +70,8 @@ namespace osu.Game.Graphics
         {
             DateTimeOffset localDate = date.ToLocalTime();
 
-            dateText.Text = $"{localDate:d MMMM yyyy} ";
-            timeText.Text = $"{localDate:HH:mm:ss \"UTC\"z}";
+            dateText.Text = LocalisableString.Interpolate($"{localDate:d MMMM yyyy} ");
+            timeText.Text = LocalisableString.Interpolate($"{localDate:HH:mm:ss \"UTC\"z}");
         }
 
         public void Move(Vector2 pos) => Position = pos;

osu.Game/Graphics/OsuColour.cs

@@ -22,38 +22,8 @@ namespace osu.Game.Graphics
         public static Color4 Gray(byte amt) => new Color4(amt, amt, amt, 255);
 
         /// <summary>
-        /// Retrieves the colour for a <see cref="DifficultyRating"/>.
+        /// Retrieves the colour for a given point in the star range.
         /// </summary>
-        /// <remarks>
-        /// Sourced from the @diff-{rating} variables in https://github.com/ppy/osu-web/blob/71fbab8936d79a7929d13854f5e854b4f383b236/resources/assets/less/variables.less.
-        /// </remarks>
-        public Color4 ForDifficultyRating(DifficultyRating difficulty, bool useLighterColour = false)
-        {
-            switch (difficulty)
-            {
-                case DifficultyRating.Easy:
-                    return Color4Extensions.FromHex("4ebfff");
-
-                case DifficultyRating.Normal:
-                    return Color4Extensions.FromHex("66ff91");
-
-                case DifficultyRating.Hard:
-                    return Color4Extensions.FromHex("f7e85d");
-
-                case DifficultyRating.Insane:
-                    return Color4Extensions.FromHex("ff7e68");
-
-                case DifficultyRating.Expert:
-                    return Color4Extensions.FromHex("fe3c71");
-
-                case DifficultyRating.ExpertPlus:
-                    return Color4Extensions.FromHex("6662dd");
-
-                default:
-                    throw new ArgumentOutOfRangeException(nameof(difficulty));
-            }
-        }
-
         public Color4 ForStarDifficulty(double starDifficulty) => ColourUtils.SampleFromLinearGradient(new[]
         {
             (0.1f, Color4Extensions.FromHex("aaaaaa")),

osu.Game/Graphics/ScreenshotManager.cs

@@ -4,6 +4,7 @@
 #nullable disable
 
 using System;
+using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 using osu.Framework.Allocation;
@@ -117,11 +118,11 @@ namespace osu.Game.Graphics
 
                 host.GetClipboard()?.SetImage(image);
 
-                string filename = getFilename();
+                (string filename, var stream) = getWritableStream();
 
                 if (filename == null) return;
 
-                using (var stream = storage.CreateFileSafely(filename))
+                using (stream)
                 {
                     switch (screenshotFormat.Value)
                     {
@@ -142,7 +143,7 @@ namespace osu.Game.Graphics
 
                 notificationOverlay.Post(new SimpleNotification
                 {
-                    Text = $"{filename} saved!",
+                    Text = $"Screenshot {filename} saved!",
                     Activated = () =>
                     {
                         storage.PresentFileExternally(filename);
@@ -152,23 +153,28 @@ namespace osu.Game.Graphics
             }
         });
 
-        private string getFilename()
+        private static readonly object filename_reservation_lock = new object();
+
+        private (string filename, Stream stream) getWritableStream()
         {
-            var dt = DateTime.Now;
-            string fileExt = screenshotFormat.ToString().ToLowerInvariant();
-
-            string withoutIndex = $"osu_{dt:yyyy-MM-dd_HH-mm-ss}.{fileExt}";
-            if (!storage.Exists(withoutIndex))
-                return withoutIndex;
-
-            for (ulong i = 1; i < ulong.MaxValue; i++)
+            lock (filename_reservation_lock)
             {
-                string indexedName = $"osu_{dt:yyyy-MM-dd_HH-mm-ss}-{i}.{fileExt}";
-                if (!storage.Exists(indexedName))
-                    return indexedName;
-            }
+                var dt = DateTime.Now;
+                string fileExt = screenshotFormat.ToString().ToLowerInvariant();
 
-            return null;
+                string withoutIndex = $"osu_{dt:yyyy-MM-dd_HH-mm-ss}.{fileExt}";
+                if (!storage.Exists(withoutIndex))
+                    return (withoutIndex, storage.GetStream(withoutIndex, FileAccess.Write, FileMode.Create));
+
+                for (ulong i = 1; i < ulong.MaxValue; i++)
+                {
+                    string indexedName = $"osu_{dt:yyyy-MM-dd_HH-mm-ss}-{i}.{fileExt}";
+                    if (!storage.Exists(indexedName))
+                        return (indexedName, storage.GetStream(indexedName, FileAccess.Write, FileMode.Create));
+                }
+
+                return (null, null);
+            }
         }
     }
 }

osu.Game/Graphics/UserInterface/BreadcrumbControl.cs

@@ -52,8 +52,8 @@ namespace osu.Game.Graphics.UserInterface
 
             public readonly SpriteIcon Chevron;
 
-            //don't allow clicking between transitions and don't make the chevron clickable
-            public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => Alpha == 1f && Text.ReceivePositionalInputAt(screenSpacePos);
+            //don't allow clicking between transitions
+            public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => Alpha == 1f && base.ReceivePositionalInputAt(screenSpacePos);
 
             public override bool HandleNonPositionalInput => State == Visibility.Visible;
             public override bool HandlePositionalInput => State == Visibility.Visible;
@@ -95,7 +95,7 @@ namespace osu.Game.Graphics.UserInterface
             {
                 Text.Font = Text.Font.With(size: 18);
                 Text.Margin = new MarginPadding { Vertical = 8 };
-                Padding = new MarginPadding { Right = padding + ChevronSize };
+                Margin = new MarginPadding { Right = padding + ChevronSize };
                 Add(Chevron = new SpriteIcon
                 {
                     Anchor = Anchor.CentreRight,

osu.Game/Graphics/UserInterface/ExternalLinkButton.cs

@@ -82,7 +82,7 @@ namespace osu.Game.Graphics.UserInterface
 
                 if (Link != null)
                 {
-                    items.Add(new OsuMenuItem("Open", MenuItemType.Standard, () => host.OpenUrlExternally(Link)));
+                    items.Add(new OsuMenuItem("Open", MenuItemType.Highlighted, () => host.OpenUrlExternally(Link)));
                     items.Add(new OsuMenuItem("Copy URL", MenuItemType.Standard, copyUrl));
                 }
 

osu.Game/Graphics/UserInterface/HistoryTextBox.cs

@@ -45,6 +45,9 @@ namespace osu.Game.Graphics.UserInterface
 
         protected override bool OnKeyDown(KeyDownEvent e)
         {
+            if (e.ControlPressed || e.AltPressed || e.SuperPressed || e.ShiftPressed)
+                return false;
+
             switch (e.Key)
             {
                 case Key.Up:

osu.Game/Graphics/UserInterface/Nub.cs

@@ -114,8 +114,7 @@ namespace osu.Game.Graphics.UserInterface
             get => current;
             set
             {
-                if (value == null)
-                    throw new ArgumentNullException(nameof(value));
+                ArgumentNullException.ThrowIfNull(value);
 
                 current.UnbindBindings();
                 current.BindTo(value);

osu.Game/Graphics/UserInterface/OsuButton.cs

@@ -1,8 +1,6 @@
 // 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 disable
-
 using osu.Framework.Allocation;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
@@ -13,6 +11,7 @@ using osu.Framework.Graphics.UserInterface;
 using osu.Framework.Input.Events;
 using osu.Framework.Localisation;
 using osu.Game.Graphics.Sprites;
+using osuTK;
 using osuTK.Graphics;
 
 namespace osu.Game.Graphics.UserInterface
@@ -20,16 +19,12 @@ namespace osu.Game.Graphics.UserInterface
     /// <summary>
     /// A button with added default sound effects.
     /// </summary>
-    public partial class OsuButton : Button
+    public abstract partial class OsuButton : Button
     {
         public LocalisableString Text
         {
-            get => SpriteText?.Text ?? default;
-            set
-            {
-                if (SpriteText != null)
-                    SpriteText.Text = value;
-            }
+            get => SpriteText.Text;
+            set => SpriteText.Text = value;
         }
 
         private Color4? backgroundColour;
@@ -66,13 +61,19 @@ namespace osu.Game.Graphics.UserInterface
 
         protected override Container<Drawable> Content { get; }
 
+        public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) =>
+            // base call is checked for cases when `OsuClickableContainer` has masking applied to it directly (ie. externally in object initialisation).
+            base.ReceivePositionalInputAt(screenSpacePos)
+            // Implementations often apply masking / edge rounding at a content level, so it's imperative to check that as well.
+            && Content.ReceivePositionalInputAt(screenSpacePos);
+
         protected Box Hover;
         protected Box Background;
         protected SpriteText SpriteText;
 
         private readonly Box flashLayer;
 
-        public OsuButton(HoverSampleSet? hoverSounds = HoverSampleSet.Button)
+        protected OsuButton(HoverSampleSet? hoverSounds = HoverSampleSet.Button)
         {
             Height = 40;
 
@@ -115,7 +116,7 @@ namespace osu.Game.Graphics.UserInterface
             });
 
             if (hoverSounds.HasValue)
-                AddInternal(new HoverClickSounds(hoverSounds.Value) { Enabled = { BindTarget = Enabled } });
+                Add(new HoverClickSounds(hoverSounds.Value) { Enabled = { BindTarget = Enabled } });
         }
 
         [BackgroundDependencyLoader]

osu.Game/Graphics/UserInterface/OsuEnumDropdown.cs

@@ -12,7 +12,7 @@ namespace osu.Game.Graphics.UserInterface
     {
         public OsuEnumDropdown()
         {
-            Items = (T[])Enum.GetValues(typeof(T));
+            Items = Enum.GetValues<T>();
         }
     }
 }

osu.Game/Graphics/UserInterface/OsuTextBox.cs

@@ -277,7 +277,7 @@ namespace osu.Game.Graphics.UserInterface
         {
             var samples = sampleMap[feedbackSampleType];
 
-            if (samples == null || samples.Length == 0)
+            if (samples.Length == 0)
                 return null;
 
             return samples[RNG.Next(0, samples.Length)]?.GetChannel();

osu.Game/Graphics/UserInterface/RangeSlider.cs

@@ -197,7 +197,7 @@ namespace osu.Game.Graphics.UserInterface
                 }, true);
             }
 
-            [BackgroundDependencyLoader]
+            [BackgroundDependencyLoader(true)]
             private void load(OverlayColourProvider? colourProvider)
             {
                 if (colourProvider == null) return;

osu.Game/IO/FileAbstraction/StreamFileAbstraction.cs

@@ -23,8 +23,7 @@ namespace osu.Game.IO.FileAbstraction
 
         public void CloseStream(Stream stream)
         {
-            if (stream == null)
-                throw new ArgumentNullException(nameof(stream));
+            ArgumentNullException.ThrowIfNull(stream);
 
             stream.Close();
         }

osu.Game/IO/HardLinkHelper.cs

@@ -0,0 +1,190 @@
+// 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 System.Runtime.InteropServices;
+using System.Runtime.InteropServices.ComTypes;
+using Microsoft.Win32.SafeHandles;
+using osu.Framework;
+
+namespace osu.Game.IO
+{
+    internal static class HardLinkHelper
+    {
+        public static bool CheckAvailability(string testDestinationPath, string testSourcePath)
+        {
+            // For simplicity, only support desktop operating systems for now.
+            if (!RuntimeInfo.IsDesktop)
+                return false;
+
+            const string test_filename = "_hard_link_test";
+
+            testDestinationPath = Path.Combine(testDestinationPath, test_filename);
+            testSourcePath = Path.Combine(testSourcePath, test_filename);
+
+            cleanupFiles();
+
+            try
+            {
+                File.WriteAllText(testSourcePath, string.Empty);
+
+                // Test availability by creating an arbitrary hard link between the source and destination paths.
+                return TryCreateHardLink(testDestinationPath, testSourcePath);
+            }
+            catch
+            {
+                return false;
+            }
+            finally
+            {
+                cleanupFiles();
+            }
+
+            void cleanupFiles()
+            {
+                try
+                {
+                    File.Delete(testDestinationPath);
+                    File.Delete(testSourcePath);
+                }
+                catch
+                {
+                }
+            }
+        }
+
+        /// <summary>
+        /// Attempts to create a hard link from <paramref name="sourcePath"/> to <paramref name="destinationPath"/>,
+        /// using platform-specific native methods.
+        /// </summary>
+        /// <remarks>
+        /// Hard links are only available on desktop platforms.
+        /// </remarks>
+        /// <returns>Whether the hard link was successfully created.</returns>
+        public static bool TryCreateHardLink(string destinationPath, string sourcePath)
+        {
+            switch (RuntimeInfo.OS)
+            {
+                case RuntimeInfo.Platform.Windows:
+                    return CreateHardLink(destinationPath, sourcePath, IntPtr.Zero);
+
+                case RuntimeInfo.Platform.Linux:
+                case RuntimeInfo.Platform.macOS:
+                    return link(sourcePath, destinationPath) == 0;
+
+                default:
+                    return false;
+            }
+        }
+
+        // For future use (to detect if a file is a hard link with other references existing on disk).
+        public static int GetFileLinkCount(string filePath)
+        {
+            int result = 0;
+
+            switch (RuntimeInfo.OS)
+            {
+                case RuntimeInfo.Platform.Windows:
+                    SafeFileHandle handle = CreateFile(filePath, FileAccess.Read, FileShare.Read, IntPtr.Zero, FileMode.Open, FileAttributes.Archive, IntPtr.Zero);
+
+                    ByHandleFileInformation fileInfo;
+
+                    if (GetFileInformationByHandle(handle, out fileInfo))
+                        result = (int)fileInfo.NumberOfLinks;
+                    CloseHandle(handle);
+                    break;
+
+                case RuntimeInfo.Platform.Linux:
+                case RuntimeInfo.Platform.macOS:
+                    if (stat(filePath, out var statbuf) == 0)
+                        result = (int)statbuf.st_nlink;
+
+                    break;
+            }
+
+            return result;
+        }
+
+        #region Windows native methods
+
+        [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+        public static extern bool CreateHardLink(string lpFileName, string lpExistingFileName, IntPtr lpSecurityAttributes);
+
+        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
+        private static extern SafeFileHandle CreateFile(
+            string lpFileName,
+            [MarshalAs(UnmanagedType.U4)] FileAccess dwDesiredAccess,
+            [MarshalAs(UnmanagedType.U4)] FileShare dwShareMode,
+            IntPtr lpSecurityAttributes,
+            [MarshalAs(UnmanagedType.U4)] FileMode dwCreationDisposition,
+            [MarshalAs(UnmanagedType.U4)] FileAttributes dwFlagsAndAttributes,
+            IntPtr hTemplateFile);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        private static extern bool GetFileInformationByHandle(SafeFileHandle handle, out ByHandleFileInformation lpFileInformation);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static extern bool CloseHandle(SafeHandle hObject);
+
+        [StructLayout(LayoutKind.Sequential)]
+        private struct ByHandleFileInformation
+        {
+            public readonly uint FileAttributes;
+            public readonly FILETIME CreationTime;
+            public readonly FILETIME LastAccessTime;
+            public readonly FILETIME LastWriteTime;
+            public readonly uint VolumeSerialNumber;
+            public readonly uint FileSizeHigh;
+            public readonly uint FileSizeLow;
+            public readonly uint NumberOfLinks;
+            public readonly uint FileIndexHigh;
+            public readonly uint FileIndexLow;
+        }
+
+        #endregion
+
+        #region Linux native methods
+
+#pragma warning disable IDE1006 // Naming rule violation
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int link(string oldpath, string newpath);
+
+        [DllImport("libc", SetLastError = true)]
+        private static extern int stat(string pathname, out struct_stat statbuf);
+
+        // ReSharper disable once InconsistentNaming
+        // Struct layout is likely non-portable across unices. Tread with caution.
+        [StructLayout(LayoutKind.Sequential)]
+        private struct struct_stat
+        {
+            public readonly long st_dev;
+            public readonly long st_ino;
+            public readonly long st_nlink;
+            public readonly int st_mode;
+            public readonly int st_uid;
+            public readonly int st_gid;
+            public readonly long st_rdev;
+            public readonly long st_size;
+            public readonly long st_blksize;
+            public readonly long st_blocks;
+            public readonly timespec st_atim;
+            public readonly timespec st_mtim;
+            public readonly timespec st_ctim;
+        }
+
+        // ReSharper disable once InconsistentNaming
+        [StructLayout(LayoutKind.Sequential)]
+        private struct timespec
+        {
+            public readonly long tv_sec;
+            public readonly long tv_nsec;
+        }
+
+#pragma warning restore IDE1006
+
+        #endregion
+    }
+}

osu.Game/IO/Serialization/Converters/TypedListConverter.cs

@@ -63,7 +63,7 @@ namespace osu.Game.IO.Serialization.Converters
                     throw new JsonException("Expected $type token.");
 
                 string typeName = lookupTable[(int)tok["$type"]];
-                var instance = (T)Activator.CreateInstance(Type.GetType(typeName).AsNonNull());
+                var instance = (T)Activator.CreateInstance(Type.GetType(typeName).AsNonNull())!;
                 serializer.Populate(itemReader, instance);
 
                 list.Add(instance);

osu.Game/Localisation/BeatmapOverlayStrings.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.Framework.Localisation;
+
+namespace osu.Game.Localisation
+{
+    public static class BeatmapOverlayStrings
+    {
+        private const string prefix = @"osu.Game.Resources.Localisation.BeatmapOverlayStrings";
+
+        /// <summary>
+        /// "User content disclaimer"
+        /// </summary>
+        public static LocalisableString UserContentDisclaimerHeader => new TranslatableString(getKey(@"user_content_disclaimer"), @"User content disclaimer");
+
+        /// <summary>
+        /// "By turning off the &quot;Featured Artist&quot; filter, all user-uploaded content will be displayed.
+        ///
+        /// This includes content that may not be correctly licensed for osu! usage. Browse at your own risk."
+        /// </summary>
+        public static LocalisableString UserContentDisclaimerDescription => new TranslatableString(getKey(@"by_turning_off_the_featured"), @"By turning off the ""Featured Artist"" filter, all user-uploaded content will be displayed.
+
+This includes content that may not be correctly licensed for osu! usage. Browse at your own risk.");
+
+        /// <summary>
+        /// "I understand"
+        /// </summary>
+        public static LocalisableString UserContentConfirmButtonText => new TranslatableString(getKey(@"understood"), @"I understand");
+
+        private static string getKey(string key) => $@"{prefix}:{key}";
+    }
+}

osu.Game/Localisation/ContextMenuStrings.cs

@@ -0,0 +1,24 @@
+// 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.Localisation;
+
+namespace osu.Game.Localisation
+{
+    public static class ContextMenuStrings
+    {
+        private const string prefix = @"osu.Game.Resources.Localisation.ContextMenu";
+
+        /// <summary>
+        /// "View profile"
+        /// </summary>
+        public static LocalisableString ViewProfile => new TranslatableString(getKey(@"view_profile"), @"View profile");
+
+        /// <summary>
+        /// "View beatmap"
+        /// </summary>
+        public static LocalisableString ViewBeatmap => new TranslatableString(getKey(@"view_beatmap"), @"View beatmap");
+
+        private static string getKey(string key) => $@"{prefix}:{key}";
+    }
+}

osu.Game/Localisation/FirstRunOverlayImportFromStableScreenStrings.cs

@@ -15,10 +15,10 @@ namespace osu.Game.Localisation
         public static LocalisableString Header => new TranslatableString(getKey(@"header"), @"Import");
 
         /// <summary>
-        /// "If you have an installation of a previous osu! version, you can choose to migrate your existing content. Note that this will create a copy, and not affect your existing installation."
+        /// "If you have an installation of a previous osu! version, you can choose to migrate your existing content. Note that this will not affect your existing installation's files in any way."
         /// </summary>
         public static LocalisableString Description => new TranslatableString(getKey(@"description"),
-            @"If you have an installation of a previous osu! version, you can choose to migrate your existing content. Note that this will create a copy, and not affect your existing installation.");
+            @"If you have an installation of a previous osu! version, you can choose to migrate your existing content. Note that this will not affect your existing installation's files in any way.");
 
         /// <summary>
         /// "previous osu! install"

osu.Game/Localisation/GeneralSettingsStrings.cs

@@ -64,6 +64,16 @@ namespace osu.Game.Localisation
         /// </summary>
         public static LocalisableString RunSetupWizard => new TranslatableString(getKey(@"run_setup_wizard"), @"Run setup wizard");
 
+        /// <summary>
+        /// "Learn more about lazer"
+        /// </summary>
+        public static LocalisableString LearnMoreAboutLazer => new TranslatableString(getKey(@"learn_more_about_lazer"), @"Learn more about lazer");
+
+        /// <summary>
+        /// "Check out the feature comparison and FAQ"
+        /// </summary>
+        public static LocalisableString LearnMoreAboutLazerTooltip => new TranslatableString(getKey(@"check_out_the_feature_comparison"), @"Check out the feature comparison and FAQ");
+
         /// <summary>
         /// "You are running the latest release ({0})"
         /// </summary>

osu.Game/Localisation/MaintenanceSettingsStrings.cs

@@ -54,11 +54,6 @@ namespace osu.Game.Localisation
         /// </summary>
         public static LocalisableString RestartAndReOpenRequiredForCompletion => new TranslatableString(getKey(@"restart_and_re_open_required_for_completion"), @"To complete this operation, osu! will close. Please open it again to use the new data location.");
 
-        /// <summary>
-        /// "Import beatmaps from stable"
-        /// </summary>
-        public static LocalisableString ImportBeatmapsFromStable => new TranslatableString(getKey(@"import_beatmaps_from_stable"), @"Import beatmaps from stable");
-
         /// <summary>
         /// "Delete ALL beatmaps"
         /// </summary>
@@ -69,31 +64,16 @@ namespace osu.Game.Localisation
         /// </summary>
         public static LocalisableString DeleteAllBeatmapVideos => new TranslatableString(getKey(@"delete_all_beatmap_videos"), @"Delete ALL beatmap videos");
 
-        /// <summary>
-        /// "Import scores from stable"
-        /// </summary>
-        public static LocalisableString ImportScoresFromStable => new TranslatableString(getKey(@"import_scores_from_stable"), @"Import scores from stable");
-
         /// <summary>
         /// "Delete ALL scores"
         /// </summary>
         public static LocalisableString DeleteAllScores => new TranslatableString(getKey(@"delete_all_scores"), @"Delete ALL scores");
 
-        /// <summary>
-        /// "Import skins from stable"
-        /// </summary>
-        public static LocalisableString ImportSkinsFromStable => new TranslatableString(getKey(@"import_skins_from_stable"), @"Import skins from stable");
-
         /// <summary>
         /// "Delete ALL skins"
         /// </summary>
         public static LocalisableString DeleteAllSkins => new TranslatableString(getKey(@"delete_all_skins"), @"Delete ALL skins");
 
-        /// <summary>
-        /// "Import collections from stable"
-        /// </summary>
-        public static LocalisableString ImportCollectionsFromStable => new TranslatableString(getKey(@"import_collections_from_stable"), @"Import collections from stable");
-
         /// <summary>
         /// "Delete ALL collections"
         /// </summary>

osu.Game/Models/RealmUser.cs

@@ -27,7 +27,7 @@ namespace osu.Game.Models
 
         public bool IsBot => false;
 
-        public bool Equals(RealmUser other)
+        public bool Equals(RealmUser? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;

osu.Game/Online/API/APIAccess.cs

@@ -259,7 +259,11 @@ namespace osu.Game.Online.API
 
             var friendsReq = new GetFriendsRequest();
             friendsReq.Failure += _ => state.Value = APIState.Failing;
-            friendsReq.Success += res => friends.AddRange(res);
+            friendsReq.Success += res =>
+            {
+                friends.Clear();
+                friends.AddRange(res);
+            };
 
             if (!handleRequest(friendsReq))
             {

osu.Game/Online/API/APIMod.cs

@@ -39,7 +39,7 @@ namespace osu.Game.Online.API
 
             foreach (var (_, property) in mod.GetSettingsSourceProperties())
             {
-                var bindable = (IBindable)property.GetValue(mod);
+                var bindable = (IBindable)property.GetValue(mod)!;
 
                 if (!bindable.IsDefault)
                     Settings.Add(property.Name.ToSnakeCase(), bindable.GetUnderlyingSettingValue());
@@ -60,16 +60,16 @@ namespace osu.Game.Online.API
             {
                 foreach (var (_, property) in resultMod.GetSettingsSourceProperties())
                 {
-                    if (!Settings.TryGetValue(property.Name.ToSnakeCase(), out object settingValue))
+                    if (!Settings.TryGetValue(property.Name.ToSnakeCase(), out object? settingValue))
                         continue;
 
                     try
                     {
-                        resultMod.CopyAdjustedSetting((IBindable)property.GetValue(resultMod), settingValue);
+                        resultMod.CopyAdjustedSetting((IBindable)property.GetValue(resultMod)!, settingValue);
                     }
                     catch (Exception ex)
                     {
-                        Logger.Log($"Failed to copy mod setting value '{settingValue ?? "null"}' to \"{property.Name}\": {ex.Message}");
+                        Logger.Log($"Failed to copy mod setting value '{settingValue}' to \"{property.Name}\": {ex.Message}");
                     }
                 }
             }
@@ -79,7 +79,7 @@ namespace osu.Game.Online.API
 
         public bool ShouldSerializeSettings() => Settings.Count > 0;
 
-        public bool Equals(APIMod other)
+        public bool Equals(APIMod? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;

osu.Game/Online/API/Requests/GetScoresRequest.cs

@@ -1,8 +1,6 @@
 // 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 disable
-
 using System;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets;
@@ -11,10 +9,11 @@ using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Rulesets.Mods;
 using System.Text;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace osu.Game.Online.API.Requests
 {
-    public class GetScoresRequest : APIRequest<APIScoresCollection>
+    public class GetScoresRequest : APIRequest<APIScoresCollection>, IEquatable<GetScoresRequest>
     {
         public const int MAX_SCORES_PER_REQUEST = 50;
 
@@ -23,7 +22,7 @@ namespace osu.Game.Online.API.Requests
         private readonly IRulesetInfo ruleset;
         private readonly IEnumerable<IMod> mods;
 
-        public GetScoresRequest(IBeatmapInfo beatmapInfo, IRulesetInfo ruleset, BeatmapLeaderboardScope scope = BeatmapLeaderboardScope.Global, IEnumerable<IMod> mods = null)
+        public GetScoresRequest(IBeatmapInfo beatmapInfo, IRulesetInfo ruleset, BeatmapLeaderboardScope scope = BeatmapLeaderboardScope.Global, IEnumerable<IMod>? mods = null)
         {
             if (beatmapInfo.OnlineID <= 0)
                 throw new InvalidOperationException($"Cannot lookup a beatmap's scores without having a populated {nameof(IBeatmapInfo.OnlineID)}.");
@@ -51,5 +50,16 @@ namespace osu.Game.Online.API.Requests
 
             return query.ToString();
         }
+
+        public bool Equals(GetScoresRequest? other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+
+            return beatmapInfo.Equals(other.beatmapInfo)
+                   && scope == other.scope
+                   && ruleset.Equals(other.ruleset)
+                   && mods.SequenceEqual(other.mods);
+        }
     }
 }

osu.Game/Online/API/Requests/GetUserBeatmapsRequest.cs

@@ -32,6 +32,7 @@ namespace osu.Game.Online.API.Requests
         Loved,
         Pending,
         Guest,
-        Graveyard
+        Graveyard,
+        Nominated,
     }
 }

osu.Game/Online/API/Requests/GetUsersRequest.cs

@@ -9,7 +9,7 @@ namespace osu.Game.Online.API.Requests
 {
     public class GetUsersRequest : APIRequest<GetUsersResponse>
     {
-        private readonly int[] userIds;
+        public readonly int[] UserIds;
 
         private const int max_ids_per_request = 50;
 
@@ -18,9 +18,9 @@ namespace osu.Game.Online.API.Requests
             if (userIds.Length > max_ids_per_request)
                 throw new ArgumentException($"{nameof(GetUsersRequest)} calls only support up to {max_ids_per_request} IDs at once");
 
-            this.userIds = userIds;
+            UserIds = userIds;
         }
 
-        protected override string Target => "users/?ids[]=" + string.Join("&ids[]=", userIds);
+        protected override string Target => "users/?ids[]=" + string.Join("&ids[]=", UserIds);
     }
 }

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

@@ -143,7 +143,7 @@ namespace osu.Game.Online.API.Requests.Responses
 
             public bool Equals(IRulesetInfo? other) => other is APIRuleset r && this.MatchesOnlineID(r);
 
-            public int CompareTo(IRulesetInfo other)
+            public int CompareTo(IRulesetInfo? other)
             {
                 if (!(other is APIRuleset ruleset))
                     throw new ArgumentException($@"Object is not of type {nameof(APIRuleset)}.", nameof(other));

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

@@ -111,6 +111,12 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty(@"language")]
         public BeatmapSetOnlineLanguage Language { get; set; }
 
+        [JsonProperty(@"current_nominations")]
+        public BeatmapSetOnlineNomination[]? CurrentNominations { get; set; }
+
+        [JsonProperty(@"related_users")]
+        public APIUser[]? RelatedUsers { get; set; }
+
         public string Source { get; set; } = string.Empty;
 
         [JsonProperty(@"tags")]

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

@@ -21,7 +21,7 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty]
         private string type
         {
-            set => Type = (RecentActivityType)Enum.Parse(typeof(RecentActivityType), value.ToPascalCase());
+            set => Type = Enum.Parse<RecentActivityType>(value.ToPascalCase());
         }
 
         public RecentActivityType Type;
@@ -29,7 +29,7 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty]
         private string scoreRank
         {
-            set => ScoreRank = (ScoreRank)Enum.Parse(typeof(ScoreRank), value);
+            set => ScoreRank = Enum.Parse<ScoreRank>(value);
         }
 
         public ScoreRank ScoreRank;

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

@@ -164,6 +164,9 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty(@"guest_beatmapset_count")]
         public int GuestBeatmapsetCount;
 
+        [JsonProperty(@"nominated_beatmapset_count")]
+        public int NominatedBeatmapsetCount;
+
         [JsonProperty(@"scores_best_count")]
         public int ScoresBestCount;
 
@@ -182,7 +185,7 @@ namespace osu.Game.Online.API.Requests.Responses
         [JsonProperty(@"playstyle")]
         private string[] playStyle
         {
-            set => PlayStyles = value?.Select(str => Enum.Parse(typeof(APIPlayStyle), str, true)).Cast<APIPlayStyle>().ToArray();
+            set => PlayStyles = value?.Select(str => Enum.Parse<APIPlayStyle>(str, true)).ToArray();
         }
 
         public APIPlayStyle[] PlayStyles;
@@ -252,6 +255,9 @@ namespace osu.Game.Online.API.Requests.Responses
         [CanBeNull]
         public Dictionary<string, UserStatistics> RulesetsStatistics { get; set; }
 
+        [JsonProperty("groups")]
+        public APIUserGroup[] Groups;
+
         public override string ToString() => Username;
 
         /// <summary>

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

@@ -0,0 +1,37 @@
+// 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 Newtonsoft.Json;
+
+namespace osu.Game.Online.API.Requests.Responses
+{
+    public class APIUserGroup
+    {
+        [JsonProperty(@"colour")]
+        public string Colour { get; set; } = null!;
+
+        [JsonProperty(@"has_listing")]
+        public bool HasListings { get; set; }
+
+        [JsonProperty(@"has_playmodes")]
+        public bool HasPlaymodes { get; set; }
+
+        [JsonProperty(@"id")]
+        public int Id { get; set; }
+
+        [JsonProperty(@"identifier")]
+        public string Identifier { get; set; } = null!;
+
+        [JsonProperty(@"is_probationary")]
+        public bool IsProbationary { get; set; }
+
+        [JsonProperty(@"name")]
+        public string Name { get; set; } = null!;
+
+        [JsonProperty(@"short_name")]
+        public string ShortName { get; set; } = null!;
+
+        [JsonProperty(@"playmodes")]
+        public string[]? Playmodes { get; set; }
+    }
+}

osu.Game/Online/Chat/Channel.cs

@@ -98,6 +98,11 @@ namespace osu.Game.Online.Chat
         /// </summary>
         public Bindable<Message> HighlightedMessage = new Bindable<Message>();
 
+        /// <summary>
+        /// The current text box message while in this <see cref="Channel"/>.
+        /// </summary>
+        public Bindable<string> TextBoxMessage = new Bindable<string>(string.Empty);
+
         [JsonConstructor]
         public Channel()
         {

osu.Game/Online/Chat/ChannelManager.cs

@@ -71,7 +71,6 @@ namespace osu.Game.Online.Chat
         private UserLookupCache users { get; set; }
 
         private readonly IBindable<APIState> apiState = new Bindable<APIState>();
-        private bool channelsInitialised;
         private ScheduledDelegate scheduledAck;
 
         private long? lastSilenceMessageId;
@@ -95,15 +94,7 @@ namespace osu.Game.Online.Chat
 
             connector.NewMessages += msgs => Schedule(() => addMessages(msgs));
 
-            connector.PresenceReceived += () => Schedule(() =>
-            {
-                if (!channelsInitialised)
-                {
-                    channelsInitialised = true;
-                    // we want this to run after the first presence so we can see if the user is in any channels already.
-                    initializeChannels();
-                }
-            });
+            connector.PresenceReceived += () => Schedule(initializeChannels);
 
             connector.Start();
 
@@ -118,8 +109,7 @@ namespace osu.Game.Online.Chat
         /// <param name="name"></param>
         public void OpenChannel(string name)
         {
-            if (name == null)
-                throw new ArgumentNullException(nameof(name));
+            ArgumentNullException.ThrowIfNull(name);
 
             CurrentChannel.Value = AvailableChannels.FirstOrDefault(c => c.Name == name) ?? throw new ChannelNotFoundException(name);
         }
@@ -130,8 +120,7 @@ namespace osu.Game.Online.Chat
         /// <param name="user">The user the private channel is opened with.</param>
         public void OpenPrivateChannel(APIUser user)
         {
-            if (user == null)
-                throw new ArgumentNullException(nameof(user));
+            ArgumentNullException.ThrowIfNull(user);
 
             if (user.Id == api.LocalUser.Value.Id)
                 return;
@@ -337,6 +326,11 @@ namespace osu.Game.Online.Chat
 
         private void initializeChannels()
         {
+            // This request is self-retrying until it succeeds.
+            // To avoid requests piling up when not logged in (ie. API is unavailable) exit early.
+            if (!api.IsLoggedIn)
+                return;
+
             var req = new ListChannelsRequest();
 
             bool joinDefaults = JoinedChannels.Count == 0;
@@ -352,10 +346,11 @@ namespace osu.Game.Online.Chat
                         joinChannel(ch);
                 }
             };
+
             req.Failure += error =>
             {
                 Logger.Error(error, "Fetching channel list failed");
-                initializeChannels();
+                Scheduler.AddDelayed(initializeChannels, 60000);
             };
 
             api.Queue(req);
@@ -529,6 +524,10 @@ namespace osu.Game.Online.Chat
                         {
                             Logger.Log($"Joined public channel {channel}");
                             joinChannel(channel, fetchInitialMessages);
+
+                            // Required after joining public channels to mark the user as online in them.
+                            // Todo: Temporary workaround for https://github.com/ppy/osu-web/issues/9602
+                            SendAck();
                         };
                         req.Failure += e =>
                         {

osu.Game/Online/Chat/InfoMessage.cs

@@ -1,9 +1,6 @@
 // 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 disable
-
-using System;
 using osu.Game.Online.API.Requests.Responses;
 
 namespace osu.Game.Online.Chat
@@ -13,7 +10,6 @@ namespace osu.Game.Online.Chat
         public InfoMessage(string message)
             : base(null)
         {
-            Timestamp = DateTimeOffset.Now;
             Content = message;
 
             Sender = APIUser.SYSTEM_USER;

osu.Game/Online/Chat/LocalEchoMessage.cs

@@ -1,8 +1,6 @@
 // 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 disable
-
 namespace osu.Game.Online.Chat
 {
     public class LocalEchoMessage : LocalMessage

osu.Game/Online/Chat/LocalMessage.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.
 
-#nullable disable
+using System;
 
 namespace osu.Game.Online.Chat
 {
@@ -13,6 +13,7 @@ namespace osu.Game.Online.Chat
         protected LocalMessage(long? id)
             : base(id)
         {
+            Timestamp = DateTimeOffset.Now;
         }
     }
 }

osu.Game/Online/Chat/Message.cs

@@ -5,6 +5,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Threading;
 using Newtonsoft.Json;
 using osu.Game.Online.API.Requests.Responses;
 
@@ -59,19 +60,28 @@ namespace osu.Game.Online.Chat
         /// <remarks>The <see cref="Link"/>s' <see cref="Link.Index"/> and <see cref="Link.Length"/>s are according to <see cref="DisplayContent"/></remarks>
         public List<Link> Links;
 
+        private static long constructionOrderStatic;
+        private readonly long constructionOrder;
+
         public Message(long? id)
         {
             Id = id;
+
+            constructionOrder = Interlocked.Increment(ref constructionOrderStatic);
         }
 
         public int CompareTo(Message other)
         {
-            if (!Id.HasValue)
-                return other.Id.HasValue ? 1 : Timestamp.CompareTo(other.Timestamp);
-            if (!other.Id.HasValue)
-                return -1;
+            if (Id.HasValue && other.Id.HasValue)
+                return Id.Value.CompareTo(other.Id.Value);
 
-            return Id.Value.CompareTo(other.Id.Value);
+            int timestampComparison = Timestamp.CompareTo(other.Timestamp);
+
+            if (timestampComparison != 0)
+                return timestampComparison;
+
+            // Timestamp might not be accurate enough to make a stable sorting decision.
+            return constructionOrder.CompareTo(other.constructionOrder);
         }
 
         public virtual bool Equals(Message other)
@@ -85,6 +95,6 @@ namespace osu.Game.Online.Chat
         // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         public override int GetHashCode() => Id.GetHashCode();
 
-        public override string ToString() => $"[{ChannelId}] ({Id}) {Sender}: {Content}";
+        public override string ToString() => $"({(Id?.ToString() ?? "null")}) {Timestamp} {Sender}: {Content}";
     }
 }

osu.Game/Online/Chat/MessageFormatter.cs

@@ -71,7 +71,7 @@ namespace osu.Game.Online.Chat
             {
                 int index = m.Index - captureOffset;
 
-                string? displayText = string.Format(display,
+                string displayText = string.Format(display,
                     m.Groups[0],
                     m.Groups["text"].Value,
                     m.Groups["url"].Value).Trim();
@@ -109,7 +109,7 @@ namespace osu.Game.Online.Chat
             foreach (Match m in regex.Matches(result.Text, startIndex))
             {
                 int index = m.Index;
-                string? linkText = m.Groups["link"].Value;
+                string linkText = m.Groups["link"].Value;
                 int indexLength = linkText.Length;
 
                 var details = GetLinkDetails(linkText);
@@ -125,7 +125,7 @@ namespace osu.Game.Online.Chat
 
         public static LinkDetails GetLinkDetails(string url)
         {
-            string[]? args = url.Split('/', StringSplitOptions.RemoveEmptyEntries);
+            string[] args = url.Split('/', StringSplitOptions.RemoveEmptyEntries);
             args[0] = args[0].TrimEnd(':');
 
             switch (args[0])
@@ -341,6 +341,8 @@ namespace osu.Game.Online.Chat
         OpenWiki,
         Custom,
         OpenChangelog,
+        FilterBeatmapSetGenre,
+        FilterBeatmapSetLanguage,
     }
 
     public class Link : IComparable<Link>
@@ -362,6 +364,6 @@ namespace osu.Game.Online.Chat
 
         public bool Overlaps(Link otherLink) => Index < otherLink.Index + otherLink.Length && otherLink.Index < Index + Length;
 
-        public int CompareTo(Link otherLink) => Index > otherLink.Index ? 1 : -1;
+        public int CompareTo(Link? otherLink) => Index > otherLink?.Index ? 1 : -1;
     }
 }

osu.Game/Online/Chat/MessageNotifier.cs

@@ -5,6 +5,7 @@
 
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics;
 using System.Linq;
 using System.Text.RegularExpressions;
 using osu.Framework.Allocation;
@@ -61,12 +62,16 @@ namespace osu.Game.Online.Chat
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
+                    Debug.Assert(e.NewItems != null);
+
                     foreach (var channel in e.NewItems.Cast<Channel>())
                         channel.NewMessagesArrived += checkNewMessages;
 
                     break;
 
                 case NotifyCollectionChangedAction.Remove:
+                    Debug.Assert(e.OldItems != null);
+
                     foreach (var channel in e.OldItems.Cast<Channel>())
                         channel.NewMessagesArrived -= checkNewMessages;
 

osu.Game/Online/Chat/StandAloneChatDisplay.cs

@@ -111,8 +111,13 @@ namespace osu.Game.Online.Chat
         {
             drawableChannel?.Expire();
 
+            if (e.OldValue != null)
+                TextBox?.Current.UnbindFrom(e.OldValue.TextBoxMessage);
+
             if (e.NewValue == null) return;
 
+            TextBox?.Current.BindTo(e.NewValue.TextBoxMessage);
+
             drawableChannel = CreateDrawableChannel(e.NewValue);
             drawableChannel.CreateChatLineAction = CreateMessage;
             drawableChannel.Padding = new MarginPadding { Bottom = postingTextBox ? text_box_height : 0 };

osu.Game/Online/HubClientConnector.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Net;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.SignalR.Client;
@@ -59,17 +60,21 @@ namespace osu.Game.Online
             var builder = new HubConnectionBuilder()
                 .WithUrl(endpoint, options =>
                 {
-                    // Use HttpClient.DefaultProxy once on net6 everywhere.
-                    // The credential setter can also be removed at this point.
-                    options.Proxy = WebRequest.DefaultWebProxy;
-                    if (options.Proxy != null)
-                        options.Proxy.Credentials = CredentialCache.DefaultCredentials;
+                    // Configuring proxies is not supported on iOS, see https://github.com/xamarin/xamarin-macios/issues/14632.
+                    if (RuntimeInfo.OS != RuntimeInfo.Platform.iOS)
+                    {
+                        // Use HttpClient.DefaultProxy once on net6 everywhere.
+                        // The credential setter can also be removed at this point.
+                        options.Proxy = WebRequest.DefaultWebProxy;
+                        if (options.Proxy != null)
+                            options.Proxy.Credentials = CredentialCache.DefaultCredentials;
+                    }
 
                     options.Headers.Add("Authorization", $"Bearer {api.AccessToken}");
                     options.Headers.Add("OsuVersionHash", versionHash);
                 });
 
-            if (RuntimeInfo.SupportsJIT && preferMessagePack)
+            if (RuntimeFeature.IsDynamicCodeCompiled && preferMessagePack)
             {
                 builder.AddMessagePackProtocol(options =>
                 {

osu.Game/Online/Leaderboards/LeaderboardScoreTooltip.cs

@@ -136,9 +136,8 @@ namespace osu.Game.Online.Leaderboards
         {
             if (displayedScore != null)
             {
-                timestampLabel.Text = prefer24HourTime.Value
-                    ? $"Played on {displayedScore.Date.ToLocalTime():d MMMM yyyy HH:mm}"
-                    : $"Played on {displayedScore.Date.ToLocalTime():d MMMM yyyy h:mm tt}";
+                timestampLabel.Text = LocalisableString.Format("Played on {0}",
+                    displayedScore.Date.ToLocalTime().ToLocalisableString(prefer24HourTime.Value ? @"d MMMM yyyy HH:mm" : @"d MMMM yyyy h:mm tt"));
             }
         }
 

osu.Game/Online/Metadata/OnlineMetadataClient.cs

@@ -68,7 +68,7 @@ namespace osu.Game.Online.Metadata
                         while (true)
                         {
                             Logger.Log($"Requesting catch-up from {lastQueueId.Value}");
-                            var catchUpChanges = await GetChangesSince(lastQueueId.Value);
+                            var catchUpChanges = await GetChangesSince(lastQueueId.Value).ConfigureAwait(true);
 
                             lastQueueId.Value = catchUpChanges.LastProcessedQueueID;
 
@@ -78,7 +78,7 @@ namespace osu.Game.Online.Metadata
                                 break;
                             }
 
-                            await ProcessChanges(catchUpChanges.BeatmapSetIDs);
+                            await ProcessChanges(catchUpChanges.BeatmapSetIDs).ConfigureAwait(true);
                         }
                     }
                     catch (Exception e)
@@ -101,7 +101,7 @@ namespace osu.Game.Online.Metadata
             if (!catchingUp)
                 lastQueueId.Value = updates.LastProcessedQueueID;
 
-            await ProcessChanges(updates.BeatmapSetIDs);
+            await ProcessChanges(updates.BeatmapSetIDs).ConfigureAwait(false);
         }
 
         public override Task<BeatmapUpdates> GetChangesSince(int queueId)

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -822,7 +822,7 @@ namespace osu.Game.Online.Multiplayer
             {
                 if (cancellationToken.IsCancellationRequested)
                 {
-                    tcs.SetCanceled();
+                    tcs.SetCanceled(cancellationToken);
                     return;
                 }
 

osu.Game/Online/Multiplayer/MultiplayerRoomUser.cs

@@ -54,10 +54,10 @@ namespace osu.Game.Online.Multiplayer
             return UserID == other.UserID;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(this, obj)) return true;
-            if (obj.GetType() != GetType()) return false;
+            if (obj?.GetType() != GetType()) return false;
 
             return Equals((MultiplayerRoomUser)obj);
         }

osu.Game/Online/Multiplayer/OnlineMultiplayerClient.cs

@@ -80,7 +80,7 @@ namespace osu.Game.Online.Multiplayer
 
             try
             {
-                return await connection.InvokeAsync<MultiplayerRoom>(nameof(IMultiplayerServer.JoinRoomWithPassword), roomId, password ?? string.Empty);
+                return await connection.InvokeAsync<MultiplayerRoom>(nameof(IMultiplayerServer.JoinRoomWithPassword), roomId, password ?? string.Empty).ConfigureAwait(false);
             }
             catch (HubException exception)
             {
@@ -88,8 +88,8 @@ namespace osu.Game.Online.Multiplayer
                 {
                     Debug.Assert(connector != null);
 
-                    await connector.Reconnect();
-                    return await JoinRoom(roomId, password);
+                    await connector.Reconnect().ConfigureAwait(false);
+                    return await JoinRoom(roomId, password).ConfigureAwait(false);
                 }
 
                 throw;