Merge branch 'master' into Liswiera-FL-changes

osu.Game.Rulesets.Taiko/Skinning/Default/CirclePiece.cs

@@ -153,7 +153,7 @@ namespace osu.Game.Rulesets.Taiko.Skinning.Default
             if (!effectPoint.KiaiMode)
                 return;
 
-            if (beatIndex % (int)timingPoint.TimeSignature != 0)
+            if (beatIndex % timingPoint.TimeSignature.Numerator != 0)
                 return;
 
             double duration = timingPoint.BeatLength * 2;

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

@@ -178,17 +178,17 @@ namespace osu.Game.Tests.Beatmaps.Formats
                 var timingPoint = controlPoints.TimingPointAt(0);
                 Assert.AreEqual(956, timingPoint.Time);
                 Assert.AreEqual(329.67032967033, timingPoint.BeatLength);
-                Assert.AreEqual(TimeSignatures.SimpleQuadruple, timingPoint.TimeSignature);
+                Assert.AreEqual(TimeSignature.SimpleQuadruple, timingPoint.TimeSignature);
 
                 timingPoint = controlPoints.TimingPointAt(48428);
                 Assert.AreEqual(956, timingPoint.Time);
                 Assert.AreEqual(329.67032967033d, timingPoint.BeatLength);
-                Assert.AreEqual(TimeSignatures.SimpleQuadruple, timingPoint.TimeSignature);
+                Assert.AreEqual(TimeSignature.SimpleQuadruple, timingPoint.TimeSignature);
 
                 timingPoint = controlPoints.TimingPointAt(119637);
                 Assert.AreEqual(119637, timingPoint.Time);
                 Assert.AreEqual(659.340659340659, timingPoint.BeatLength);
-                Assert.AreEqual(TimeSignatures.SimpleQuadruple, timingPoint.TimeSignature);
+                Assert.AreEqual(TimeSignature.SimpleQuadruple, timingPoint.TimeSignature);
 
                 var difficultyPoint = controlPoints.DifficultyPointAt(0);
                 Assert.AreEqual(0, difficultyPoint.Time);

osu.Game.Tests/Database/GeneralUsageTests.cs

@@ -46,7 +46,7 @@ namespace osu.Game.Tests.Database
             {
                 bool callbackRan = false;
 
-                realmFactory.Run(realm =>
+                realmFactory.RegisterCustomSubscription(realm =>
                 {
                     var subscription = realm.All<BeatmapInfo>().QueryAsyncWithNotifications((sender, changes, error) =>
                     {
@@ -60,6 +60,7 @@ namespace osu.Game.Tests.Database
                     realmFactory.Run(r => r.Refresh());
 
                     subscription?.Dispose();
+                    return null;
                 });
 
                 Assert.IsTrue(callbackRan);

osu.Game.Tests/Database/RealmLiveTests.cs

@@ -239,7 +239,7 @@ namespace osu.Game.Tests.Database
             {
                 int changesTriggered = 0;
 
-                realmFactory.Run(outerRealm =>
+                realmFactory.RegisterCustomSubscription(outerRealm =>
                 {
                     outerRealm.All<BeatmapInfo>().QueryAsyncWithNotifications(gotChange);
                     ILive<BeatmapInfo>? liveBeatmap = null;
@@ -282,6 +282,8 @@ namespace osu.Game.Tests.Database
                             r.Remove(resolved);
                         });
                     });
+
+                    return null;
                 });
 
                 void gotChange(IRealmCollection<BeatmapInfo> sender, ChangeSet changes, Exception error)

osu.Game.Tests/Database/RealmSubscriptionRegistrationTests.cs

@@ -0,0 +1,138 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets;
+using osu.Game.Tests.Resources;
+using Realms;
+
+#nullable enable
+
+namespace osu.Game.Tests.Database
+{
+    [TestFixture]
+    public class RealmSubscriptionRegistrationTests : RealmTest
+    {
+        [Test]
+        public void TestSubscriptionWithContextLoss()
+        {
+            IEnumerable<BeatmapSetInfo>? resolvedItems = null;
+            ChangeSet? lastChanges = null;
+
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                var registration = realmFactory.RegisterForNotifications(realm => realm.All<BeatmapSetInfo>(), onChanged);
+
+                testEventsArriving(true);
+
+                // All normal until here.
+                // Now let's yank the main realm context.
+                resolvedItems = null;
+                lastChanges = null;
+
+                using (realmFactory.BlockAllOperations())
+                    Assert.That(resolvedItems, Is.Empty);
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                testEventsArriving(true);
+
+                // Now let's try unsubscribing.
+                resolvedItems = null;
+                lastChanges = null;
+
+                registration.Dispose();
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                testEventsArriving(false);
+
+                // And make sure even after another context loss we don't get firings.
+                using (realmFactory.BlockAllOperations())
+                    Assert.That(resolvedItems, Is.Null);
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                testEventsArriving(false);
+
+                void testEventsArriving(bool shouldArrive)
+                {
+                    realmFactory.Run(realm => realm.Refresh());
+
+                    if (shouldArrive)
+                        Assert.That(resolvedItems, Has.One.Items);
+                    else
+                        Assert.That(resolvedItems, Is.Null);
+
+                    realmFactory.Write(realm =>
+                    {
+                        realm.RemoveAll<BeatmapSetInfo>();
+                        realm.RemoveAll<RulesetInfo>();
+                    });
+
+                    realmFactory.Run(realm => realm.Refresh());
+
+                    if (shouldArrive)
+                        Assert.That(lastChanges?.DeletedIndices, Has.One.Items);
+                    else
+                        Assert.That(lastChanges, Is.Null);
+                }
+            });
+
+            void onChanged(IRealmCollection<BeatmapSetInfo> sender, ChangeSet? changes, Exception error)
+            {
+                if (changes == null)
+                    resolvedItems = sender;
+
+                lastChanges = changes;
+            }
+        }
+
+        [Test]
+        public void TestCustomRegisterWithContextLoss()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                BeatmapSetInfo? beatmapSetInfo = null;
+
+                realmFactory.Write(realm => realm.Add(TestResources.CreateTestBeatmapSetInfo()));
+
+                var subscription = realmFactory.RegisterCustomSubscription(realm =>
+                {
+                    beatmapSetInfo = realm.All<BeatmapSetInfo>().First();
+
+                    return new InvokeOnDisposal(() => beatmapSetInfo = null);
+                });
+
+                Assert.That(beatmapSetInfo, Is.Not.Null);
+
+                using (realmFactory.BlockAllOperations())
+                {
+                    // custom disposal action fired when context lost.
+                    Assert.That(beatmapSetInfo, Is.Null);
+                }
+
+                // re-registration after context restore.
+                realmFactory.Run(realm => realm.Refresh());
+                Assert.That(beatmapSetInfo, Is.Not.Null);
+
+                subscription.Dispose();
+
+                Assert.That(beatmapSetInfo, Is.Null);
+
+                using (realmFactory.BlockAllOperations())
+                    Assert.That(beatmapSetInfo, Is.Null);
+
+                realmFactory.Run(realm => realm.Refresh());
+                Assert.That(beatmapSetInfo, Is.Null);
+            });
+        }
+    }
+}

osu.Game.Tests/NonVisual/BarLineGeneratorTest.cs

@@ -26,7 +26,7 @@ namespace osu.Game.Tests.NonVisual
 
             const int beat_length_numerator = 2000;
             const int beat_length_denominator = 7;
-            const TimeSignatures signature = TimeSignatures.SimpleQuadruple;
+            TimeSignature signature = TimeSignature.SimpleQuadruple;
 
             var beatmap = new Beatmap
             {
@@ -49,7 +49,7 @@ namespace osu.Game.Tests.NonVisual
             for (int i = 0; i * beat_length_denominator < barLines.Count; i++)
             {
                 var barLine = barLines[i * beat_length_denominator];
-                int expectedTime = beat_length_numerator * (int)signature * i;
+                int expectedTime = beat_length_numerator * signature.Numerator * i;
 
                 // every seventh bar's start time should be at least greater than the whole number we expect.
                 // It cannot be less, as that can affect overlapping scroll algorithms
@@ -60,7 +60,7 @@ namespace osu.Game.Tests.NonVisual
                 Assert.IsTrue(Precision.AlmostEquals(barLine.StartTime, expectedTime));
 
                 // check major/minor lines for good measure too
-                Assert.AreEqual(i % (int)signature == 0, barLine.Major);
+                Assert.AreEqual(i % signature.Numerator == 0, barLine.Major);
             }
         }
 

osu.Game.Tests/Resources/TestResources.cs

@@ -80,7 +80,10 @@ namespace osu.Game.Tests.Resources
         public static BeatmapSetInfo CreateTestBeatmapSetInfo(int? difficultyCount = null, RulesetInfo[] rulesets = null)
         {
             int j = 0;
-            RulesetInfo getRuleset() => rulesets?[j++ % rulesets.Length] ?? new OsuRuleset().RulesetInfo;
+
+            rulesets ??= new[] { new OsuRuleset().RulesetInfo };
+
+            RulesetInfo getRuleset() => rulesets?[j++ % rulesets.Length];
 
             int setId = Interlocked.Increment(ref importId);
 

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

@@ -46,6 +46,7 @@ namespace osu.Game.Tests.Visual.Editing
                 editorBeatmap.BeatmapInfo.Metadata.Artist = "artist";
                 editorBeatmap.BeatmapInfo.Metadata.Title = "title";
             });
+            AddStep("Set author", () => editorBeatmap.BeatmapInfo.Metadata.Author.Username = "author");
             AddStep("Set difficulty name", () => editorBeatmap.BeatmapInfo.DifficultyName = "difficulty");
 
             AddStep("Add timing point", () => editorBeatmap.ControlPointInfo.Add(0, new TimingControlPoint()));
@@ -64,6 +65,7 @@ namespace osu.Game.Tests.Visual.Editing
             AddStep("Save", () => InputManager.Keys(PlatformAction.Save));
 
             checkMutations();
+            AddAssert("Beatmap has correct .osu file path", () => editorBeatmap.BeatmapInfo.Path == "artist - title (author) [difficulty].osu");
 
             AddStep("Exit", () => InputManager.Key(Key.Escape));
 
@@ -88,6 +90,7 @@ namespace osu.Game.Tests.Visual.Editing
             AddAssert("Beatmap contains single hitcircle", () => editorBeatmap.HitObjects.Count == 1);
             AddAssert("Beatmap has correct overall difficulty", () => editorBeatmap.Difficulty.OverallDifficulty == 7);
             AddAssert("Beatmap has correct metadata", () => editorBeatmap.BeatmapInfo.Metadata.Artist == "artist" && editorBeatmap.BeatmapInfo.Metadata.Title == "title");
+            AddAssert("Beatmap has correct author", () => editorBeatmap.BeatmapInfo.Metadata.Author.Username == "author");
             AddAssert("Beatmap has correct difficulty name", () => editorBeatmap.BeatmapInfo.DifficultyName == "difficulty");
         }
     }

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

@@ -0,0 +1,88 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Graphics;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps.Timing;
+using osu.Game.Graphics.UserInterface;
+using osu.Game.Screens.Edit.Timing;
+
+namespace osu.Game.Tests.Visual.Editing
+{
+    public class TestSceneLabelledTimeSignature : OsuManualInputManagerTestScene
+    {
+        private LabelledTimeSignature timeSignature;
+
+        private void createLabelledTimeSignature(TimeSignature initial) => AddStep("create labelled time signature", () =>
+        {
+            Child = timeSignature = new LabelledTimeSignature
+            {
+                Label = "Time Signature",
+                RelativeSizeAxes = Axes.None,
+                Width = 400,
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                Current = { Value = initial }
+            };
+        });
+
+        private OsuTextBox numeratorTextBox => timeSignature.ChildrenOfType<OsuTextBox>().Single();
+
+        [Test]
+        public void TestInitialValue()
+        {
+            createLabelledTimeSignature(TimeSignature.SimpleTriple);
+            AddAssert("current is 3/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleTriple));
+        }
+
+        [Test]
+        public void TestChangeViaCurrent()
+        {
+            createLabelledTimeSignature(TimeSignature.SimpleQuadruple);
+            AddAssert("current is 4/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleQuadruple));
+
+            AddStep("set current to 5/4", () => timeSignature.Current.Value = new TimeSignature(5));
+
+            AddAssert("current is 5/4", () => timeSignature.Current.Value.Equals(new TimeSignature(5)));
+            AddAssert("numerator is 5", () => numeratorTextBox.Current.Value == "5");
+
+            AddStep("set current to 3/4", () => timeSignature.Current.Value = TimeSignature.SimpleTriple);
+
+            AddAssert("current is 3/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleTriple));
+            AddAssert("numerator is 3", () => numeratorTextBox.Current.Value == "3");
+        }
+
+        [Test]
+        public void TestChangeNumerator()
+        {
+            createLabelledTimeSignature(TimeSignature.SimpleQuadruple);
+            AddAssert("current is 4/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleQuadruple));
+
+            AddStep("focus text box", () => InputManager.ChangeFocus(numeratorTextBox));
+
+            AddStep("set numerator to 7", () => numeratorTextBox.Current.Value = "7");
+            AddAssert("current is 4/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleQuadruple));
+
+            AddStep("drop focus", () => InputManager.ChangeFocus(null));
+            AddAssert("current is 7/4", () => timeSignature.Current.Value.Equals(new TimeSignature(7)));
+        }
+
+        [Test]
+        public void TestInvalidChangeRollbackOnCommit()
+        {
+            createLabelledTimeSignature(TimeSignature.SimpleQuadruple);
+            AddAssert("current is 4/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleQuadruple));
+
+            AddStep("focus text box", () => InputManager.ChangeFocus(numeratorTextBox));
+
+            AddStep("set numerator to 0", () => numeratorTextBox.Current.Value = "0");
+            AddAssert("current is 4/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleQuadruple));
+
+            AddStep("drop focus", () => InputManager.ChangeFocus(null));
+            AddAssert("current is 4/4", () => timeSignature.Current.Value.Equals(TimeSignature.SimpleQuadruple));
+            AddAssert("numerator is 4", () => numeratorTextBox.Current.Value == "4");
+        }
+    }
+}

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

@@ -24,8 +24,8 @@ namespace osu.Game.Tests.Visual.Gameplay
 
             Add(new ModNightcore<HitObject>.NightcoreBeatContainer());
 
-            AddStep("change signature to quadruple", () => Beatmap.Value.Beatmap.ControlPointInfo.TimingPoints.ForEach(p => p.TimeSignature = TimeSignatures.SimpleQuadruple));
-            AddStep("change signature to triple", () => Beatmap.Value.Beatmap.ControlPointInfo.TimingPoints.ForEach(p => p.TimeSignature = TimeSignatures.SimpleTriple));
+            AddStep("change signature to quadruple", () => Beatmap.Value.Beatmap.ControlPointInfo.TimingPoints.ForEach(p => p.TimeSignature = TimeSignature.SimpleQuadruple));
+            AddStep("change signature to triple", () => Beatmap.Value.Beatmap.ControlPointInfo.TimingPoints.ForEach(p => p.TimeSignature = TimeSignature.SimpleTriple));
         }
     }
 }

osu.Game.Tests/Visual/Menus/TestSceneLoginPanel.cs

@@ -8,6 +8,8 @@ using osu.Framework.Testing;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Online.API;
 using osu.Game.Overlays.Login;
+using osu.Game.Users.Drawables;
+using osuTK.Input;
 
 namespace osu.Game.Tests.Visual.Menus
 {
@@ -15,6 +17,7 @@ namespace osu.Game.Tests.Visual.Menus
     public class TestSceneLoginPanel : OsuManualInputManagerTestScene
     {
         private LoginPanel loginPanel;
+        private int hideCount;
 
         [SetUpSteps]
         public void SetUpSteps()
@@ -26,6 +29,7 @@ namespace osu.Game.Tests.Visual.Menus
                     Anchor = Anchor.Centre,
                     Origin = Anchor.Centre,
                     Width = 0.5f,
+                    RequestHide = () => hideCount++,
                 });
             });
         }
@@ -51,5 +55,22 @@ namespace osu.Game.Tests.Visual.Menus
             AddStep("enter password", () => loginPanel.ChildrenOfType<OsuPasswordTextBox>().First().Text = "password");
             AddStep("submit", () => loginPanel.ChildrenOfType<OsuButton>().First(b => b.Text.ToString() == "Sign in").TriggerClick());
         }
+
+        [Test]
+        public void TestClickingOnFlagClosesPanel()
+        {
+            AddStep("reset hide count", () => hideCount = 0);
+
+            AddStep("logout", () => API.Logout());
+            AddStep("enter password", () => loginPanel.ChildrenOfType<OsuPasswordTextBox>().First().Text = "password");
+            AddStep("submit", () => loginPanel.ChildrenOfType<OsuButton>().First(b => b.Text.ToString() == "Sign in").TriggerClick());
+
+            AddStep("click on flag", () =>
+            {
+                InputManager.MoveMouseTo(loginPanel.ChildrenOfType<UpdateableFlag>().First());
+                InputManager.Click(MouseButton.Left);
+            });
+            AddAssert("hide requested", () => hideCount == 1);
+        }
     }
 }

osu.Game/Beatmaps/BeatmapModelManager.cs

@@ -88,7 +88,7 @@ namespace osu.Game.Beatmaps
         private static string getFilename(BeatmapInfo beatmapInfo)
         {
             var metadata = beatmapInfo.Metadata;
-            return $"{metadata.Artist} - {metadata.Title} ({metadata.Author}) [{beatmapInfo.DifficultyName}].osu".GetValidArchiveContentFilename();
+            return $"{metadata.Artist} - {metadata.Title} ({metadata.Author.Username}) [{beatmapInfo.DifficultyName}].osu".GetValidArchiveContentFilename();
         }
 
         /// <summary>

osu.Game/Beatmaps/ControlPoints/TimingControlPoint.cs

@@ -13,7 +13,7 @@ namespace osu.Game.Beatmaps.ControlPoints
         /// <summary>
         /// The time signature at this control point.
         /// </summary>
-        public readonly Bindable<TimeSignatures> TimeSignatureBindable = new Bindable<TimeSignatures>(TimeSignatures.SimpleQuadruple) { Default = TimeSignatures.SimpleQuadruple };
+        public readonly Bindable<TimeSignature> TimeSignatureBindable = new Bindable<TimeSignature>(TimeSignature.SimpleQuadruple);
 
         /// <summary>
         /// Default length of a beat in milliseconds. Used whenever there is no beatmap or track playing.
@@ -35,7 +35,7 @@ namespace osu.Game.Beatmaps.ControlPoints
         /// <summary>
         /// The time signature at this control point.
         /// </summary>
-        public TimeSignatures TimeSignature
+        public TimeSignature TimeSignature
         {
             get => TimeSignatureBindable.Value;
             set => TimeSignatureBindable.Value = value;

osu.Game/Beatmaps/Formats/LegacyBeatmapDecoder.cs

@@ -340,9 +340,9 @@ namespace osu.Game.Beatmaps.Formats
             double beatLength = Parsing.ParseDouble(split[1].Trim());
             double speedMultiplier = beatLength < 0 ? 100.0 / -beatLength : 1;
 
-            TimeSignatures timeSignature = TimeSignatures.SimpleQuadruple;
+            TimeSignature timeSignature = TimeSignature.SimpleQuadruple;
             if (split.Length >= 3)
-                timeSignature = split[2][0] == '0' ? TimeSignatures.SimpleQuadruple : (TimeSignatures)Parsing.ParseInt(split[2]);
+                timeSignature = split[2][0] == '0' ? TimeSignature.SimpleQuadruple : new TimeSignature(Parsing.ParseInt(split[2]));
 
             LegacySampleBank sampleSet = defaultSampleBank;
             if (split.Length >= 4)

osu.Game/Beatmaps/Formats/LegacyBeatmapEncoder.cs

@@ -227,7 +227,7 @@ namespace osu.Game.Beatmaps.Formats
                 if (effectPoint.OmitFirstBarLine)
                     effectFlags |= LegacyEffectFlags.OmitFirstBarLine;
 
-                writer.Write(FormattableString.Invariant($"{(int)legacyControlPoints.TimingPointAt(time).TimeSignature},"));
+                writer.Write(FormattableString.Invariant($"{legacyControlPoints.TimingPointAt(time).TimeSignature.Numerator},"));
                 writer.Write(FormattableString.Invariant($"{(int)toLegacySampleBank(tempHitSample.Bank)},"));
                 writer.Write(FormattableString.Invariant($"{toLegacyCustomSampleBank(tempHitSample)},"));
                 writer.Write(FormattableString.Invariant($"{tempHitSample.Volume},"));

osu.Game/Beatmaps/Timing/TimeSignature.cs

@@ -0,0 +1,45 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+
+namespace osu.Game.Beatmaps.Timing
+{
+    /// <summary>
+    /// Stores the time signature of a track.
+    /// For now, the lower numeral can only be 4; support for other denominators can be considered at a later date.
+    /// </summary>
+    public class TimeSignature : IEquatable<TimeSignature>
+    {
+        /// <summary>
+        /// The numerator of a signature.
+        /// </summary>
+        public int Numerator { get; }
+
+        // TODO: support time signatures with a denominator other than 4
+        // this in particular requires a new beatmap format.
+
+        public TimeSignature(int numerator)
+        {
+            if (numerator < 1)
+                throw new ArgumentOutOfRangeException(nameof(numerator), numerator, "The numerator of a time signature must be positive.");
+
+            Numerator = numerator;
+        }
+
+        public static TimeSignature SimpleTriple { get; } = new TimeSignature(3);
+        public static TimeSignature SimpleQuadruple { get; } = new TimeSignature(4);
+
+        public override string ToString() => $"{Numerator}/4";
+
+        public bool Equals(TimeSignature other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+
+            return Numerator == other.Numerator;
+        }
+
+        public override int GetHashCode() => Numerator;
+    }
+}

osu.Game/Beatmaps/Timing/TimeSignatures.cs

@@ -1,11 +1,13 @@
 // 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.ComponentModel;
 
 namespace osu.Game.Beatmaps.Timing
 {
-    public enum TimeSignatures
+    [Obsolete("Use osu.Game.Beatmaps.Timing.TimeSignature instead.")]
+    public enum TimeSignatures // can be removed 20220722
     {
         [Description("4/4")]
         SimpleQuadruple = 4,

osu.Game/Database/EFToRealmMigrator.cs

@@ -27,7 +27,9 @@ namespace osu.Game.Database
 {
     internal class EFToRealmMigrator : CompositeDrawable
     {
-        public bool FinishedMigrating { get; private set; }
+        public Task<bool> MigrationCompleted => migrationCompleted.Task;
+
+        private readonly TaskCompletionSource<bool> migrationCompleted = new TaskCompletionSource<bool>();
 
         [Resolved]
         private DatabaseContextFactory efContextFactory { get; set; } = null!;
@@ -99,6 +101,17 @@ namespace osu.Game.Database
             {
                 using (var ef = efContextFactory.Get())
                 {
+                    realmContextFactory.Write(realm =>
+                    {
+                        // Before beginning, ensure realm is in an empty state.
+                        // Migrations which are half-completed could lead to issues if the user tries a second time.
+                        // Note that we only do this for beatmaps and scores since the other migrations are yonks old.
+                        realm.RemoveAll<BeatmapSetInfo>();
+                        realm.RemoveAll<BeatmapInfo>();
+                        realm.RemoveAll<BeatmapMetadata>();
+                        realm.RemoveAll<ScoreInfo>();
+                    });
+
                     migrateSettings(ef);
                     migrateSkins(ef);
                     migrateBeatmaps(ef);
@@ -114,7 +127,7 @@ namespace osu.Game.Database
                     Logger.Log("Your development database has been fully migrated to realm. If you switch back to a pre-realm branch and need your previous database, rename the backup file back to \"client.db\".\n\nNote that doing this can potentially leave your file store in a bad state.", level: LogLevel.Important);
             }, TaskCreationOptions.LongRunning).ContinueWith(t =>
             {
-                FinishedMigrating = true;
+                migrationCompleted.SetResult(true);
             });
         }
 
@@ -149,87 +162,78 @@ namespace osu.Game.Database
             {
                 log($"Found {count} beatmaps in EF");
 
-                // only migrate data if the realm database is empty.
-                // note that this cannot be written as: `realm.All<BeatmapSetInfo>().All(s => s.Protected)`, because realm does not support `.All()`.
-                if (realm.All<BeatmapSetInfo>().Any(s => !s.Protected))
-                {
-                    log("Skipping migration as realm already has beatmaps loaded");
-                }
-                else
-                {
-                    var transaction = realm.BeginWrite();
-                    int written = 0;
+                var transaction = realm.BeginWrite();
+                int written = 0;
 
-                    try
+                try
+                {
+                    foreach (var beatmapSet in existingBeatmapSets)
                     {
-                        foreach (var beatmapSet in existingBeatmapSets)
+                        if (++written % 1000 == 0)
                         {
-                            if (++written % 1000 == 0)
-                            {
-                                transaction.Commit();
-                                transaction = realm.BeginWrite();
-                                log($"Migrated {written}/{count} beatmaps...");
-                            }
+                            transaction.Commit();
+                            transaction = realm.BeginWrite();
+                            log($"Migrated {written}/{count} beatmaps...");
+                        }
 
-                            var realmBeatmapSet = new BeatmapSetInfo
+                        var realmBeatmapSet = new BeatmapSetInfo
+                        {
+                            OnlineID = beatmapSet.OnlineID ?? -1,
+                            DateAdded = beatmapSet.DateAdded,
+                            Status = beatmapSet.Status,
+                            DeletePending = beatmapSet.DeletePending,
+                            Hash = beatmapSet.Hash,
+                            Protected = beatmapSet.Protected,
+                        };
+
+                        migrateFiles(beatmapSet, realm, realmBeatmapSet);
+
+                        foreach (var beatmap in beatmapSet.Beatmaps)
+                        {
+                            var ruleset = realm.Find<RulesetInfo>(beatmap.RulesetInfo.ShortName);
+                            var metadata = getBestMetadata(beatmap.Metadata, beatmapSet.Metadata);
+
+                            var realmBeatmap = new BeatmapInfo(ruleset, new BeatmapDifficulty(beatmap.BaseDifficulty), metadata)
                             {
-                                OnlineID = beatmapSet.OnlineID ?? -1,
-                                DateAdded = beatmapSet.DateAdded,
-                                Status = beatmapSet.Status,
-                                DeletePending = beatmapSet.DeletePending,
-                                Hash = beatmapSet.Hash,
-                                Protected = beatmapSet.Protected,
+                                DifficultyName = beatmap.DifficultyName,
+                                Status = beatmap.Status,
+                                OnlineID = beatmap.OnlineID ?? -1,
+                                Length = beatmap.Length,
+                                BPM = beatmap.BPM,
+                                Hash = beatmap.Hash,
+                                StarRating = beatmap.StarRating,
+                                MD5Hash = beatmap.MD5Hash,
+                                Hidden = beatmap.Hidden,
+                                AudioLeadIn = beatmap.AudioLeadIn,
+                                StackLeniency = beatmap.StackLeniency,
+                                SpecialStyle = beatmap.SpecialStyle,
+                                LetterboxInBreaks = beatmap.LetterboxInBreaks,
+                                WidescreenStoryboard = beatmap.WidescreenStoryboard,
+                                EpilepsyWarning = beatmap.EpilepsyWarning,
+                                SamplesMatchPlaybackRate = beatmap.SamplesMatchPlaybackRate,
+                                DistanceSpacing = beatmap.DistanceSpacing,
+                                BeatDivisor = beatmap.BeatDivisor,
+                                GridSize = beatmap.GridSize,
+                                TimelineZoom = beatmap.TimelineZoom,
+                                Countdown = beatmap.Countdown,
+                                CountdownOffset = beatmap.CountdownOffset,
+                                MaxCombo = beatmap.MaxCombo,
+                                Bookmarks = beatmap.Bookmarks,
+                                BeatmapSet = realmBeatmapSet,
                             };
 
-                            migrateFiles(beatmapSet, realm, realmBeatmapSet);
-
-                            foreach (var beatmap in beatmapSet.Beatmaps)
-                            {
-                                var ruleset = realm.Find<RulesetInfo>(beatmap.RulesetInfo.ShortName);
-                                var metadata = getBestMetadata(beatmap.Metadata, beatmapSet.Metadata);
-
-                                var realmBeatmap = new BeatmapInfo(ruleset, new BeatmapDifficulty(beatmap.BaseDifficulty), metadata)
-                                {
-                                    DifficultyName = beatmap.DifficultyName,
-                                    Status = beatmap.Status,
-                                    OnlineID = beatmap.OnlineID ?? -1,
-                                    Length = beatmap.Length,
-                                    BPM = beatmap.BPM,
-                                    Hash = beatmap.Hash,
-                                    StarRating = beatmap.StarRating,
-                                    MD5Hash = beatmap.MD5Hash,
-                                    Hidden = beatmap.Hidden,
-                                    AudioLeadIn = beatmap.AudioLeadIn,
-                                    StackLeniency = beatmap.StackLeniency,
-                                    SpecialStyle = beatmap.SpecialStyle,
-                                    LetterboxInBreaks = beatmap.LetterboxInBreaks,
-                                    WidescreenStoryboard = beatmap.WidescreenStoryboard,
-                                    EpilepsyWarning = beatmap.EpilepsyWarning,
-                                    SamplesMatchPlaybackRate = beatmap.SamplesMatchPlaybackRate,
-                                    DistanceSpacing = beatmap.DistanceSpacing,
-                                    BeatDivisor = beatmap.BeatDivisor,
-                                    GridSize = beatmap.GridSize,
-                                    TimelineZoom = beatmap.TimelineZoom,
-                                    Countdown = beatmap.Countdown,
-                                    CountdownOffset = beatmap.CountdownOffset,
-                                    MaxCombo = beatmap.MaxCombo,
-                                    Bookmarks = beatmap.Bookmarks,
-                                    BeatmapSet = realmBeatmapSet,
-                                };
-
-                                realmBeatmapSet.Beatmaps.Add(realmBeatmap);
-                            }
-
-                            realm.Add(realmBeatmapSet);
+                            realmBeatmapSet.Beatmaps.Add(realmBeatmap);
                         }
-                    }
-                    finally
-                    {
-                        transaction.Commit();
-                    }
 
-                    log($"Successfully migrated {count} beatmaps to realm");
+                        realm.Add(realmBeatmapSet);
+                    }
                 }
+                finally
+                {
+                    transaction.Commit();
+                }
+
+                log($"Successfully migrated {count} beatmaps to realm");
             });
         }
 
@@ -280,70 +284,62 @@ namespace osu.Game.Database
             {
                 log($"Found {count} scores in EF");
 
-                // only migrate data if the realm database is empty.
-                if (realm.All<ScoreInfo>().Any())
-                {
-                    log("Skipping migration as realm already has scores loaded");
-                }
-                else
-                {
-                    var transaction = realm.BeginWrite();
-                    int written = 0;
+                var transaction = realm.BeginWrite();
+                int written = 0;
 
-                    try
+                try
+                {
+                    foreach (var score in existingScores)
                     {
-                        foreach (var score in existingScores)
+                        if (++written % 1000 == 0)
                         {
-                            if (++written % 1000 == 0)
-                            {
-                                transaction.Commit();
-                                transaction = realm.BeginWrite();
-                                log($"Migrated {written}/{count} scores...");
-                            }
-
-                            var beatmap = realm.All<BeatmapInfo>().First(b => b.Hash == score.BeatmapInfo.Hash);
-                            var ruleset = realm.Find<RulesetInfo>(score.Ruleset.ShortName);
-                            var user = new RealmUser
-                            {
-                                OnlineID = score.User.OnlineID,
-                                Username = score.User.Username
-                            };
-
-                            var realmScore = new ScoreInfo(beatmap, ruleset, user)
-                            {
-                                Hash = score.Hash,
-                                DeletePending = score.DeletePending,
-                                OnlineID = score.OnlineID ?? -1,
-                                ModsJson = score.ModsJson,
-                                StatisticsJson = score.StatisticsJson,
-                                TotalScore = score.TotalScore,
-                                MaxCombo = score.MaxCombo,
-                                Accuracy = score.Accuracy,
-                                HasReplay = ((IScoreInfo)score).HasReplay,
-                                Date = score.Date,
-                                PP = score.PP,
-                                Rank = score.Rank,
-                                HitEvents = score.HitEvents,
-                                Passed = score.Passed,
-                                Combo = score.Combo,
-                                Position = score.Position,
-                                Statistics = score.Statistics,
-                                Mods = score.Mods,
-                                APIMods = score.APIMods,
-                            };
-
-                            migrateFiles(score, realm, realmScore);
-
-                            realm.Add(realmScore);
+                            transaction.Commit();
+                            transaction = realm.BeginWrite();
+                            log($"Migrated {written}/{count} scores...");
                         }
-                    }
-                    finally
-                    {
-                        transaction.Commit();
-                    }
 
-                    log($"Successfully migrated {count} scores to realm");
+                        var beatmap = realm.All<BeatmapInfo>().First(b => b.Hash == score.BeatmapInfo.Hash);
+                        var ruleset = realm.Find<RulesetInfo>(score.Ruleset.ShortName);
+                        var user = new RealmUser
+                        {
+                            OnlineID = score.User.OnlineID,
+                            Username = score.User.Username
+                        };
+
+                        var realmScore = new ScoreInfo(beatmap, ruleset, user)
+                        {
+                            Hash = score.Hash,
+                            DeletePending = score.DeletePending,
+                            OnlineID = score.OnlineID ?? -1,
+                            ModsJson = score.ModsJson,
+                            StatisticsJson = score.StatisticsJson,
+                            TotalScore = score.TotalScore,
+                            MaxCombo = score.MaxCombo,
+                            Accuracy = score.Accuracy,
+                            HasReplay = ((IScoreInfo)score).HasReplay,
+                            Date = score.Date,
+                            PP = score.PP,
+                            Rank = score.Rank,
+                            HitEvents = score.HitEvents,
+                            Passed = score.Passed,
+                            Combo = score.Combo,
+                            Position = score.Position,
+                            Statistics = score.Statistics,
+                            Mods = score.Mods,
+                            APIMods = score.APIMods,
+                        };
+
+                        migrateFiles(score, realm, realmScore);
+
+                        realm.Add(realmScore);
+                    }
                 }
+                finally
+                {
+                    transaction.Commit();
+                }
+
+                log($"Successfully migrated {count} scores to realm");
             });
         }
 

osu.Game/Database/EmptyRealmSet.cs

@@ -0,0 +1,46 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using Realms;
+using Realms.Schema;
+
+#nullable enable
+
+namespace osu.Game.Database
+{
+    public class EmptyRealmSet<T> : IRealmCollection<T>
+    {
+        private IList<T> emptySet => Array.Empty<T>();
+
+        public IEnumerator<T> GetEnumerator() => emptySet.GetEnumerator();
+        IEnumerator IEnumerable.GetEnumerator() => emptySet.GetEnumerator();
+        public int Count => emptySet.Count;
+        public T this[int index] => emptySet[index];
+        public int IndexOf(object item) => emptySet.IndexOf((T)item);
+        public bool Contains(object item) => emptySet.Contains((T)item);
+
+        public event NotifyCollectionChangedEventHandler? CollectionChanged
+        {
+            add => throw new NotImplementedException();
+            remove => throw new NotImplementedException();
+        }
+
+        public event PropertyChangedEventHandler? PropertyChanged
+        {
+            add => throw new NotImplementedException();
+            remove => throw new NotImplementedException();
+        }
+
+        public IRealmCollection<T> Freeze() => throw new NotImplementedException();
+        public IDisposable SubscribeForNotifications(NotificationCallbackDelegate<T> callback) => throw new NotImplementedException();
+        public bool IsValid => throw new NotImplementedException();
+        public Realm Realm => throw new NotImplementedException();
+        public ObjectSchema ObjectSchema => throw new NotImplementedException();
+        public bool IsFrozen => throw new NotImplementedException();
+    }
+}

osu.Game/Database/RealmContextFactory.cs

@@ -2,6 +2,8 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -61,33 +63,60 @@ namespace osu.Game.Database
 
         private readonly ThreadLocal<bool> currentThreadCanCreateContexts = new ThreadLocal<bool>();
 
+        /// <summary>
+        /// Holds a map of functions registered via <see cref="RegisterCustomSubscription"/> and <see cref="RegisterForNotifications{T}"/> and a coinciding action which when triggered,
+        /// will unregister the subscription from realm.
+        ///
+        /// Put another way, the key is an action which registers the subscription with realm. The returned <see cref="IDisposable"/> from the action is stored as the value and only
+        /// used internally.
+        ///
+        /// Entries in this dictionary are only removed when a consumer signals that the subscription should be permanently ceased (via their own <see cref="IDisposable"/>).
+        /// </summary>
+        private readonly Dictionary<Func<Realm, IDisposable?>, IDisposable?> customSubscriptionsResetMap = new Dictionary<Func<Realm, IDisposable?>, IDisposable?>();
+
+        /// <summary>
+        /// Holds a map of functions registered via <see cref="RegisterForNotifications{T}"/> and a coinciding action which when triggered,
+        /// fires a change set event with an empty collection. This is used to inform subscribers when a realm context goes away, and ensure they don't use invalidated
+        /// managed realm objects from a previous firing.
+        /// </summary>
+        private readonly Dictionary<Func<Realm, IDisposable?>, Action> notificationsResetMap = new Dictionary<Func<Realm, IDisposable?>, Action>();
+
         private static readonly GlobalStatistic<int> contexts_created = GlobalStatistics.Get<int>(@"Realm", @"Contexts (Created)");
 
         private readonly object contextLock = new object();
 
         private Realm? context;
 
-        public Realm Context
+        public Realm Context => ensureUpdateContext();
+
+        private Realm ensureUpdateContext()
         {
-            get
+            if (!ThreadSafety.IsUpdateThread)
+                throw new InvalidOperationException(@$"Use {nameof(createContext)} when performing realm operations from a non-update thread");
+
+            lock (contextLock)
             {
-                if (!ThreadSafety.IsUpdateThread)
-                    throw new InvalidOperationException(@$"Use {nameof(Run)}/{nameof(Write)} when performing realm operations from a non-update thread");
-
-                lock (contextLock)
+                if (context == null)
                 {
-                    if (context == null)
-                    {
-                        context = createContext();
-                        Logger.Log(@$"Opened realm ""{context.Config.DatabasePath}"" at version {context.Config.SchemaVersion}");
-                    }
+                    context = createContext();
+                    Logger.Log(@$"Opened realm ""{context.Config.DatabasePath}"" at version {context.Config.SchemaVersion}");
 
-                    // creating a context will ensure our schema is up-to-date and migrated.
-                    return context;
+                    // Resubscribe any subscriptions
+                    foreach (var action in customSubscriptionsResetMap.Keys)
+                        registerSubscription(action);
                 }
+
+                Debug.Assert(context != null);
+
+                // creating a context will ensure our schema is up-to-date and migrated.
+                return context;
             }
         }
 
+        internal static bool CurrentThreadSubscriptionsAllowed => current_thread_subscriptions_allowed.Value;
+
+        private static readonly ThreadLocal<bool> current_thread_subscriptions_allowed = new ThreadLocal<bool>();
+
         /// <summary>
         /// Construct a new instance of a realm context factory.
         /// </summary>
@@ -222,6 +251,117 @@ namespace osu.Game.Database
             }
         }
 
+        /// <summary>
+        /// Subscribe to a realm collection and begin watching for asynchronous changes.
+        /// </summary>
+        /// <remarks>
+        /// This adds osu! specific thread and managed state safety checks on top of <see cref="IRealmCollection{T}.SubscribeForNotifications"/>.
+        ///
+        /// In addition to the documented realm behaviour, we have the additional requirement of handling subscriptions over potential context loss.
+        /// When this happens, callback events will be automatically fired:
+        /// - On context loss, a callback with an empty collection and <c>null</c> <see cref="ChangeSet"/> will be invoked.
+        /// - On context revival, a standard initial realm callback will arrive, with <c>null</c> <see cref="ChangeSet"/> and an up-to-date collection.
+        /// </remarks>
+        /// <param name="query">The <see cref="IQueryable{T}"/> to observe for changes.</param>
+        /// <typeparam name="T">Type of the elements in the list.</typeparam>
+        /// <param name="callback">The callback to be invoked with the updated <see cref="IRealmCollection{T}"/>.</param>
+        /// <returns>
+        /// A subscription token. It must be kept alive for as long as you want to receive change notifications.
+        /// To stop receiving notifications, call <see cref="IDisposable.Dispose"/>.
+        /// </returns>
+        /// <seealso cref="IRealmCollection{T}.SubscribeForNotifications"/>
+        public IDisposable RegisterForNotifications<T>(Func<Realm, IQueryable<T>> query, NotificationCallbackDelegate<T> callback)
+            where T : RealmObjectBase
+        {
+            if (!ThreadSafety.IsUpdateThread)
+                throw new InvalidOperationException(@$"{nameof(RegisterForNotifications)} must be called from the update thread.");
+
+            lock (contextLock)
+            {
+                Func<Realm, IDisposable?> action = realm => query(realm).QueryAsyncWithNotifications(callback);
+
+                // Store an action which is used when blocking to ensure consumers don't use results of a stale changeset firing.
+                notificationsResetMap.Add(action, () => callback(new EmptyRealmSet<T>(), null, null));
+                return RegisterCustomSubscription(action);
+            }
+        }
+
+        /// <summary>
+        /// Run work on realm that will be run every time the update thread realm context gets recycled.
+        /// </summary>
+        /// <param name="action">The work to run. Return value should be an <see cref="IDisposable"/> from QueryAsyncWithNotifications, or an <see cref="InvokeOnDisposal"/> to clean up any bindings.</param>
+        /// <returns>An <see cref="IDisposable"/> which should be disposed to unsubscribe any inner subscription.</returns>
+        public IDisposable RegisterCustomSubscription(Func<Realm, IDisposable?> action)
+        {
+            if (!ThreadSafety.IsUpdateThread)
+                throw new InvalidOperationException(@$"{nameof(RegisterForNotifications)} must be called from the update thread.");
+
+            var syncContext = SynchronizationContext.Current;
+
+            registerSubscription(action);
+
+            // This token is returned to the consumer.
+            // When disposed, it will cause the registration to be permanently ceased (unsubscribed with realm and unregistered by this class).
+            return new InvokeOnDisposal(() =>
+            {
+                if (ThreadSafety.IsUpdateThread)
+                    unsubscribe();
+                else
+                    syncContext.Post(_ => unsubscribe(), null);
+
+                void unsubscribe()
+                {
+                    lock (contextLock)
+                    {
+                        if (customSubscriptionsResetMap.TryGetValue(action, out var unsubscriptionAction))
+                        {
+                            unsubscriptionAction?.Dispose();
+                            customSubscriptionsResetMap.Remove(action);
+                            notificationsResetMap.Remove(action);
+                        }
+                    }
+                }
+            });
+        }
+
+        private void registerSubscription(Func<Realm, IDisposable?> action)
+        {
+            Debug.Assert(ThreadSafety.IsUpdateThread);
+
+            lock (contextLock)
+            {
+                // Retrieve context outside of flag update to ensure that the context is constructed,
+                // as attempting to access it inside the subscription if it's not constructed would lead to
+                // cyclic invocations of the subscription callback.
+                var realm = Context;
+
+                Debug.Assert(!customSubscriptionsResetMap.TryGetValue(action, out var found) || found == null);
+
+                current_thread_subscriptions_allowed.Value = true;
+                customSubscriptionsResetMap[action] = action(realm);
+                current_thread_subscriptions_allowed.Value = false;
+            }
+        }
+
+        /// <summary>
+        /// Unregister all subscriptions when the realm context is to be recycled.
+        /// Subscriptions will still remain and will be re-subscribed when the realm context returns.
+        /// </summary>
+        private void unregisterAllSubscriptions()
+        {
+            lock (contextLock)
+            {
+                foreach (var action in notificationsResetMap.Values)
+                    action();
+
+                foreach (var action in customSubscriptionsResetMap)
+                {
+                    action.Value?.Dispose();
+                    customSubscriptionsResetMap[action.Key] = null;
+                }
+            }
+        }
+
         private Realm createContext()
         {
             if (isDisposed)
@@ -454,14 +594,29 @@ namespace osu.Game.Database
             if (isDisposed)
                 throw new ObjectDisposedException(nameof(RealmContextFactory));
 
+            SynchronizationContext? syncContext = null;
+
             try
             {
                 contextCreationLock.Wait();
 
                 lock (contextLock)
                 {
-                    if (!ThreadSafety.IsUpdateThread && context != null)
-                        throw new InvalidOperationException(@$"{nameof(BlockAllOperations)} must be called from the update thread.");
+                    if (context == null)
+                    {
+                        // null context means the update thread has not yet retrieved its context.
+                        // we don't need to worry about reviving the update context in this case, so don't bother with the SynchronizationContext.
+                        Debug.Assert(!ThreadSafety.IsUpdateThread);
+                    }
+                    else
+                    {
+                        if (!ThreadSafety.IsUpdateThread)
+                            throw new InvalidOperationException(@$"{nameof(BlockAllOperations)} must be called from the update thread.");
+
+                        syncContext = SynchronizationContext.Current;
+                    }
+
+                    unregisterAllSubscriptions();
 
                     Logger.Log(@"Blocking realm operations.", LoggingTarget.Database);
 
@@ -501,6 +656,9 @@ namespace osu.Game.Database
             {
                 factory.contextCreationLock.Release();
                 Logger.Log(@"Restoring realm operations.", LoggingTarget.Database);
+
+                // Post back to the update thread to revive any subscriptions.
+                syncContext?.Post(_ => ensureUpdateContext(), null);
             });
         }
 

osu.Game/Database/RealmObjectExtensions.cs

@@ -7,7 +7,6 @@ using System.Linq;
 using System.Runtime.Serialization;
 using AutoMapper;
 using AutoMapper.Internal;
-using osu.Framework.Development;
 using osu.Game.Beatmaps;
 using osu.Game.Input.Bindings;
 using osu.Game.Models;
@@ -272,9 +271,8 @@ namespace osu.Game.Database
         public static IDisposable? QueryAsyncWithNotifications<T>(this IRealmCollection<T> collection, NotificationCallbackDelegate<T> callback)
             where T : RealmObjectBase
         {
-            // Subscriptions can only work on the main thread.
-            if (!ThreadSafety.IsUpdateThread)
-                throw new InvalidOperationException("Cannot subscribe for realm notifications from a non-update thread.");
+            if (!RealmContextFactory.CurrentThreadSubscriptionsAllowed)
+                throw new InvalidOperationException($"Make sure to call {nameof(RealmContextFactory)}.{nameof(RealmContextFactory.RegisterForNotifications)}");
 
             return collection.SubscribeForNotifications(callback);
         }

osu.Game/Input/Bindings/DatabasedKeyBindingContainer.cs

@@ -23,7 +23,6 @@ namespace osu.Game.Input.Bindings
         private readonly int? variant;
 
         private IDisposable realmSubscription;
-        private IQueryable<RealmKeyBinding> realmKeyBindings;
 
         [Resolved]
         private RealmContextFactory realmFactory { get; set; }
@@ -47,22 +46,21 @@ namespace osu.Game.Input.Bindings
                 throw new InvalidOperationException($"{nameof(variant)} can not be null when a non-null {nameof(ruleset)} is provided.");
         }
 
-        protected override void LoadComplete()
+        private IQueryable<RealmKeyBinding> queryRealmKeyBindings()
         {
             string rulesetName = ruleset?.ShortName;
+            return realmFactory.Context.All<RealmKeyBinding>()
+                               .Where(b => b.RulesetName == rulesetName && b.Variant == variant);
+        }
 
-            realmKeyBindings = realmFactory.Context.All<RealmKeyBinding>()
-                                           .Where(b => b.RulesetName == rulesetName && b.Variant == variant);
-
-            realmSubscription = realmKeyBindings
-                .QueryAsyncWithNotifications((sender, changes, error) =>
-                {
-                    // first subscription ignored as we are handling this in LoadComplete.
-                    if (changes == null)
-                        return;
-
-                    ReloadMappings();
-                });
+        protected override void LoadComplete()
+        {
+            realmSubscription = realmFactory.RegisterForNotifications(realm => queryRealmKeyBindings(), (sender, changes, error) =>
+            {
+                // The first fire of this is a bit redundant as this is being called in base.LoadComplete,
+                // but this is safest in case the subscription is restored after a context recycle.
+                ReloadMappings();
+            });
 
             base.LoadComplete();
         }
@@ -78,11 +76,11 @@ namespace osu.Game.Input.Bindings
         {
             var defaults = DefaultKeyBindings.ToList();
 
-            List<RealmKeyBinding> newBindings = realmKeyBindings.Detach()
-                                                                // this ordering is important to ensure that we read entries from the database in the order
-                                                                // enforced by DefaultKeyBindings. allow for song select to handle actions that may otherwise
-                                                                // have been eaten by the music controller due to query order.
-                                                                .OrderBy(b => defaults.FindIndex(d => (int)d.Action == b.ActionInt)).ToList();
+            List<RealmKeyBinding> newBindings = queryRealmKeyBindings().Detach()
+                                                                       // this ordering is important to ensure that we read entries from the database in the order
+                                                                       // enforced by DefaultKeyBindings. allow for song select to handle actions that may otherwise
+                                                                       // have been eaten by the music controller due to query order.
+                                                                       .OrderBy(b => defaults.FindIndex(d => (int)d.Action == b.ActionInt)).ToList();
 
             // In the case no bindings were found in the database, presume this usage is for a non-databased ruleset.
             // This actually should never be required and can be removed if it is ever deemed to cause a problem.

osu.Game/Online/BeatmapDownloadTracker.cs

@@ -42,7 +42,7 @@ namespace osu.Game.Online
             // Used to interact with manager classes that don't support interface types. Will eventually be replaced.
             var beatmapSetInfo = new BeatmapSetInfo { OnlineID = TrackedItem.OnlineID };
 
-            realmSubscription = realmContextFactory.Context.All<BeatmapSetInfo>().Where(s => s.OnlineID == TrackedItem.OnlineID && !s.DeletePending).QueryAsyncWithNotifications((items, changes, ___) =>
+            realmSubscription = realmContextFactory.RegisterForNotifications(realm => realm.All<BeatmapSetInfo>().Where(s => s.OnlineID == TrackedItem.OnlineID && !s.DeletePending), (items, changes, ___) =>
             {
                 if (items.Any())
                     Schedule(() => UpdateState(DownloadState.LocallyAvailable));

osu.Game/Online/Rooms/OnlinePlayBeatmapAvailabilityTracker.cs

@@ -78,7 +78,7 @@ namespace osu.Game.Online.Rooms
 
                 // handles changes to hash that didn't occur from the import process (ie. a user editing the beatmap in the editor, somehow).
                 realmSubscription?.Dispose();
-                realmSubscription = filteredBeatmaps().QueryAsyncWithNotifications((items, changes, ___) =>
+                realmSubscription = realmContextFactory.RegisterForNotifications(realm => filteredBeatmaps(), (items, changes, ___) =>
                 {
                     if (changes == null)
                         return;

osu.Game/Online/ScoreDownloadTracker.cs

@@ -47,7 +47,7 @@ namespace osu.Game.Online
             Downloader.DownloadBegan += downloadBegan;
             Downloader.DownloadFailed += downloadFailed;
 
-            realmSubscription = realmContextFactory.Context.All<ScoreInfo>().Where(s => ((s.OnlineID > 0 && s.OnlineID == TrackedItem.OnlineID) || s.Hash == TrackedItem.Hash) && !s.DeletePending).QueryAsyncWithNotifications((items, changes, ___) =>
+            realmSubscription = realmContextFactory.RegisterForNotifications(realm => realm.All<ScoreInfo>().Where(s => ((s.OnlineID > 0 && s.OnlineID == TrackedItem.OnlineID) || s.Hash == TrackedItem.Hash) && !s.DeletePending), (items, changes, ___) =>
             {
                 if (items.Any())
                     Schedule(() => UpdateState(DownloadState.LocallyAvailable));

osu.Game/Overlays/MusicController.cs

@@ -30,16 +30,7 @@ namespace osu.Game.Overlays
         [Resolved]
         private BeatmapManager beatmaps { get; set; }
 
-        public IBindableList<BeatmapSetInfo> BeatmapSets
-        {
-            get
-            {
-                if (LoadState < LoadState.Ready)
-                    throw new InvalidOperationException($"{nameof(BeatmapSets)} should not be accessed before the music controller is loaded.");
-
-                return beatmapSets;
-            }
-        }
+        public IBindableList<BeatmapSetInfo> BeatmapSets => beatmapSets;
 
         /// <summary>
         /// Point in time after which the current track will be restarted on triggering a "previous track" action.
@@ -80,26 +71,26 @@ namespace osu.Game.Overlays
             mods.BindValueChanged(_ => ResetTrackAdjustments(), true);
         }
 
+        private IQueryable<BeatmapSetInfo> queryRealmBeatmapSets() =>
+            realmFactory.Context
+                        .All<BeatmapSetInfo>()
+                        .Where(s => !s.DeletePending);
+
         protected override void LoadComplete()
         {
             base.LoadComplete();
-
-            var availableBeatmaps = realmFactory.Context
-                                                .All<BeatmapSetInfo>()
-                                                .Where(s => !s.DeletePending);
-
-            // ensure we're ready before completing async load.
-            // probably not a good way of handling this (as there is a period we aren't watching for changes until the realm subscription finishes up.
-            foreach (var s in availableBeatmaps)
-                beatmapSets.Add(s);
-
-            beatmapSubscription = availableBeatmaps.QueryAsyncWithNotifications(beatmapsChanged);
+            beatmapSubscription = realmFactory.RegisterForNotifications(realm => queryRealmBeatmapSets(), beatmapsChanged);
         }
 
         private void beatmapsChanged(IRealmCollection<BeatmapSetInfo> sender, ChangeSet changes, Exception error)
         {
             if (changes == null)
+            {
+                beatmapSets.Clear();
+                foreach (var s in sender)
+                    beatmapSets.Add(s.Detach());
                 return;
+            }
 
             foreach (int i in changes.InsertedIndices)
                 beatmapSets.Insert(i, sender[i].Detach());

osu.Game/Overlays/Settings/Sections/DebugSettings/MemorySettings.cs

@@ -1,9 +1,13 @@
 // 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.Threading;
+using System.Threading.Tasks;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Localisation;
+using osu.Framework.Logging;
 using osu.Framework.Platform;
 using osu.Game.Database;
 using osu.Game.Localisation;
@@ -17,6 +21,9 @@ namespace osu.Game.Overlays.Settings.Sections.DebugSettings
         [BackgroundDependencyLoader]
         private void load(GameHost host, RealmContextFactory realmFactory)
         {
+            SettingsButton blockAction;
+            SettingsButton unblockAction;
+
             Children = new Drawable[]
             {
                 new SettingsButton
@@ -35,6 +42,51 @@ namespace osu.Game.Overlays.Settings.Sections.DebugSettings
                         }
                     }
                 },
+                blockAction = new SettingsButton
+                {
+                    Text = "Block realm",
+                },
+                unblockAction = new SettingsButton
+                {
+                    Text = "Unblock realm",
+                },
+            };
+
+            blockAction.Action = () =>
+            {
+                try
+                {
+                    var token = realmFactory.BlockAllOperations();
+
+                    blockAction.Enabled.Value = false;
+
+                    // As a safety measure, unblock after 10 seconds.
+                    // This is to handle the case where a dev may block, but then something on the update thread
+                    // accesses realm and blocks for eternity.
+                    Task.Factory.StartNew(() =>
+                    {
+                        Thread.Sleep(10000);
+                        unblock();
+                    });
+
+                    unblockAction.Action = unblock;
+
+                    void unblock()
+                    {
+                        token?.Dispose();
+                        token = null;
+
+                        Scheduler.Add(() =>
+                        {
+                            blockAction.Enabled.Value = true;
+                            unblockAction.Action = null;
+                        });
+                    }
+                }
+                catch (Exception e)
+                {
+                    Logger.Error(e, "Blocking realm failed");
+                }
             };
         }
     }

osu.Game/Overlays/Settings/Sections/SkinSection.cs

@@ -50,7 +50,12 @@ namespace osu.Game.Overlays.Settings.Sections
         private RealmContextFactory realmFactory { get; set; }
 
         private IDisposable realmSubscription;
-        private IQueryable<SkinInfo> realmSkins;
+
+        private IQueryable<SkinInfo> queryRealmSkins() =>
+            realmFactory.Context.All<SkinInfo>()
+                        .Where(s => !s.DeletePending)
+                        .OrderByDescending(s => s.Protected) // protected skins should be at the top.
+                        .ThenBy(s => s.Name, StringComparer.OrdinalIgnoreCase);
 
         [BackgroundDependencyLoader(permitNulls: true)]
         private void load(OsuConfigManager config, [CanBeNull] SkinEditorOverlay skinEditor)
@@ -78,20 +83,12 @@ namespace osu.Game.Overlays.Settings.Sections
 
             skinDropdown.Current = dropdownBindable;
 
-            realmSkins = realmFactory.Context.All<SkinInfo>()
-                                     .Where(s => !s.DeletePending)
-                                     .OrderByDescending(s => s.Protected) // protected skins should be at the top.
-                                     .ThenBy(s => s.Name, StringComparer.OrdinalIgnoreCase);
-
-            realmSubscription = realmSkins
-                .QueryAsyncWithNotifications((sender, changes, error) =>
-                {
-                    if (changes == null)
-                        return;
-
-                    // Eventually this should be handling the individual changes rather than refreshing the whole dropdown.
-                    updateItems();
-                });
+            realmSubscription = realmFactory.RegisterForNotifications(realm => queryRealmSkins(), (sender, changes, error) =>
+            {
+                // The first fire of this is a bit redundant due to the call below,
+                // but this is safest in case the subscription is restored after a context recycle.
+                updateItems();
+            });
 
             updateItems();
 
@@ -131,9 +128,9 @@ namespace osu.Game.Overlays.Settings.Sections
 
         private void updateItems()
         {
-            int protectedCount = realmSkins.Count(s => s.Protected);
+            int protectedCount = queryRealmSkins().Count(s => s.Protected);
 
-            skinItems = realmSkins.ToLive(realmFactory);
+            skinItems = queryRealmSkins().ToLive(realmFactory);
 
             skinItems.Insert(protectedCount, random_skin_info);
 

osu.Game/Rulesets/Mods/Metronome.cs

@@ -33,7 +33,7 @@ namespace osu.Game.Rulesets.Mods
 
             if (!IsBeatSyncedWithTrack) return;
 
-            int timeSignature = (int)timingPoint.TimeSignature;
+            int timeSignature = timingPoint.TimeSignature.Numerator;
 
             // play metronome from one measure before the first object.
             if (BeatSyncClock.CurrentTime < firstHitTime - timingPoint.BeatLength * timeSignature)

osu.Game/Rulesets/Mods/ModNightcore.cs

@@ -85,7 +85,7 @@ namespace osu.Game.Rulesets.Mods
             {
                 base.OnNewBeat(beatIndex, timingPoint, effectPoint, amplitudes);
 
-                int beatsPerBar = (int)timingPoint.TimeSignature;
+                int beatsPerBar = timingPoint.TimeSignature.Numerator;
                 int segmentLength = beatsPerBar * Divisor * bars_per_segment;
 
                 if (!IsBeatSyncedWithTrack)
@@ -102,14 +102,14 @@ namespace osu.Game.Rulesets.Mods
                     playBeatFor(beatIndex % segmentLength, timingPoint.TimeSignature);
             }
 
-            private void playBeatFor(int beatIndex, TimeSignatures signature)
+            private void playBeatFor(int beatIndex, TimeSignature signature)
             {
                 if (beatIndex == 0)
                     finishSample?.Play();
 
-                switch (signature)
+                switch (signature.Numerator)
                 {
-                    case TimeSignatures.SimpleTriple:
+                    case 3:
                         switch (beatIndex % 6)
                         {
                             case 0:
@@ -127,7 +127,7 @@ namespace osu.Game.Rulesets.Mods
 
                         break;
 
-                    case TimeSignatures.SimpleQuadruple:
+                    case 4:
                         switch (beatIndex % 4)
                         {
                             case 0:

osu.Game/Rulesets/Objects/BarLineGenerator.cs

@@ -41,9 +41,9 @@ namespace osu.Game.Rulesets.Objects
                 int currentBeat = 0;
 
                 // Stop on the beat before the next timing point, or if there is no next timing point stop slightly past the last object
-                double endTime = i < timingPoints.Count - 1 ? timingPoints[i + 1].Time - currentTimingPoint.BeatLength : lastHitTime + currentTimingPoint.BeatLength * (int)currentTimingPoint.TimeSignature;
+                double endTime = i < timingPoints.Count - 1 ? timingPoints[i + 1].Time - currentTimingPoint.BeatLength : lastHitTime + currentTimingPoint.BeatLength * currentTimingPoint.TimeSignature.Numerator;
 
-                double barLength = currentTimingPoint.BeatLength * (int)currentTimingPoint.TimeSignature;
+                double barLength = currentTimingPoint.BeatLength * currentTimingPoint.TimeSignature.Numerator;
 
                 for (double t = currentTimingPoint.Time; Precision.DefinitelyBigger(endTime, t); t += barLength, currentBeat++)
                 {
@@ -60,7 +60,7 @@ namespace osu.Game.Rulesets.Objects
                     BarLines.Add(new TBarLine
                     {
                         StartTime = t,
-                        Major = currentBeat % (int)currentTimingPoint.TimeSignature == 0
+                        Major = currentBeat % currentTimingPoint.TimeSignature.Numerator == 0
                     });
                 }
             }

osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineTickDisplay.cs

@@ -125,7 +125,7 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
                         if (beat == 0 && i == 0)
                             nextMinTick = float.MinValue;
 
-                        int indexInBar = beat % ((int)point.TimeSignature * beatDivisor.Value);
+                        int indexInBar = beat % (point.TimeSignature.Numerator * beatDivisor.Value);
 
                         int divisor = BindableBeatDivisor.GetDivisorForBeatIndex(beat, beatDivisor.Value);
                         var colour = BindableBeatDivisor.GetColourFor(divisor, colours);

osu.Game/Screens/Edit/Timing/LabelledTimeSignature.cs

@@ -0,0 +1,97 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.UserInterface;
+using osu.Game.Beatmaps.Timing;
+using osu.Game.Graphics;
+using osu.Game.Graphics.Sprites;
+using osu.Game.Graphics.UserInterface;
+using osu.Game.Graphics.UserInterfaceV2;
+
+namespace osu.Game.Screens.Edit.Timing
+{
+    public class LabelledTimeSignature : LabelledComponent<LabelledTimeSignature.TimeSignatureBox, TimeSignature>
+    {
+        public LabelledTimeSignature()
+            : base(false)
+        {
+        }
+
+        protected override TimeSignatureBox CreateComponent() => new TimeSignatureBox();
+
+        public class TimeSignatureBox : CompositeDrawable, IHasCurrentValue<TimeSignature>
+        {
+            private readonly BindableWithCurrent<TimeSignature> current = new BindableWithCurrent<TimeSignature>(TimeSignature.SimpleQuadruple);
+
+            public Bindable<TimeSignature> Current
+            {
+                get => current.Current;
+                set => current.Current = value;
+            }
+
+            private OsuNumberBox numeratorBox;
+
+            [BackgroundDependencyLoader]
+            private void load()
+            {
+                AutoSizeAxes = Axes.Both;
+                InternalChild = new FillFlowContainer
+                {
+                    AutoSizeAxes = Axes.Both,
+                    Direction = FillDirection.Horizontal,
+                    Children = new Drawable[]
+                    {
+                        numeratorBox = new OsuNumberBox
+                        {
+                            Width = 40,
+                            Anchor = Anchor.CentreLeft,
+                            Origin = Anchor.CentreLeft,
+                            CornerRadius = CORNER_RADIUS,
+                            CommitOnFocusLost = true
+                        },
+                        new OsuSpriteText
+                        {
+                            Anchor = Anchor.CentreLeft,
+                            Origin = Anchor.CentreLeft,
+                            Margin = new MarginPadding
+                            {
+                                Left = 5,
+                                Right = CONTENT_PADDING_HORIZONTAL
+                            },
+                            Text = "/ 4",
+                            Font = OsuFont.Default.With(size: 20)
+                        }
+                    }
+                };
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                Current.BindValueChanged(_ => updateFromCurrent(), true);
+                numeratorBox.OnCommit += (_, __) => updateFromNumeratorBox();
+            }
+
+            private void updateFromCurrent()
+            {
+                numeratorBox.Current.Value = Current.Value.Numerator.ToString();
+            }
+
+            private void updateFromNumeratorBox()
+            {
+                if (int.TryParse(numeratorBox.Current.Value, out int numerator) && numerator > 0)
+                    Current.Value = new TimeSignature(numerator);
+                else
+                {
+                    // trigger `Current` change to restore the numerator box's text to a valid value.
+                    Current.TriggerChange();
+                }
+            }
+        }
+    }
+}

osu.Game/Screens/Edit/Timing/RowAttributes/TimingRowAttribute.cs

@@ -13,7 +13,7 @@ namespace osu.Game.Screens.Edit.Timing.RowAttributes
     public class TimingRowAttribute : RowAttribute
     {
         private readonly BindableNumber<double> beatLength;
-        private readonly Bindable<TimeSignatures> timeSignature;
+        private readonly Bindable<TimeSignature> timeSignature;
         private OsuSpriteText text;
 
         public TimingRowAttribute(TimingControlPoint timing)

osu.Game/Screens/Edit/Timing/TimingSection.cs

@@ -6,7 +6,6 @@ using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Game.Beatmaps.ControlPoints;
-using osu.Game.Beatmaps.Timing;
 using osu.Game.Graphics.UserInterfaceV2;
 using osu.Game.Overlays.Settings;
 
@@ -15,7 +14,7 @@ namespace osu.Game.Screens.Edit.Timing
     internal class TimingSection : Section<TimingControlPoint>
     {
         private SettingsSlider<double> bpmSlider;
-        private SettingsEnumDropdown<TimeSignatures> timeSignature;
+        private LabelledTimeSignature timeSignature;
         private BPMTextBox bpmTextEntry;
 
         [BackgroundDependencyLoader]
@@ -25,10 +24,10 @@ namespace osu.Game.Screens.Edit.Timing
             {
                 bpmTextEntry = new BPMTextBox(),
                 bpmSlider = new BPMSlider(),
-                timeSignature = new SettingsEnumDropdown<TimeSignatures>
+                timeSignature = new LabelledTimeSignature
                 {
-                    LabelText = "Time Signature"
-                },
+                    Label = "Time Signature"
+                }
             });
         }
 

osu.Game/Screens/Loader.cs

@@ -74,11 +74,22 @@ namespace osu.Game.Screens
             base.OnEntering(last);
 
             LoadComponentAsync(precompiler = CreateShaderPrecompiler(), AddInternal);
-            LoadComponentAsync(loadableScreen = CreateLoadableScreen());
 
             // A non-null context factory means there's still content to migrate.
             if (efContextFactory != null)
+            {
                 LoadComponentAsync(realmMigrator = new EFToRealmMigrator(), AddInternal);
+                realmMigrator.MigrationCompleted.ContinueWith(_ => Schedule(() =>
+                {
+                    // Delay initial screen loading to ensure that the migration is in a complete and sane state
+                    // before the intro screen may import the game intro beatmap.
+                    LoadComponentAsync(loadableScreen = CreateLoadableScreen());
+                }));
+            }
+            else
+            {
+                LoadComponentAsync(loadableScreen = CreateLoadableScreen());
+            }
 
             LoadComponentAsync(spinner = new LoadingSpinner(true, true)
             {
@@ -96,7 +107,7 @@ namespace osu.Game.Screens
 
         private void checkIfLoaded()
         {
-            if (loadableScreen.LoadState != LoadState.Ready || !precompiler.FinishedCompiling || realmMigrator?.FinishedMigrating == false)
+            if (loadableScreen?.LoadState != LoadState.Ready || !precompiler.FinishedCompiling)
             {
                 Schedule(checkIfLoaded);
                 return;

osu.Game/Screens/Menu/IntroScreen.cs

@@ -21,6 +21,7 @@ using osu.Game.Overlays;
 using osu.Game.Screens.Backgrounds;
 using osuTK;
 using osuTK.Graphics;
+using Realms;
 
 namespace osu.Game.Screens.Menu
 {
@@ -93,28 +94,27 @@ namespace osu.Game.Screens.Menu
             MenuMusic = config.GetBindable<bool>(OsuSetting.MenuMusic);
             seeya = audio.Samples.Get(SeeyaSampleName);
 
-            ILive<BeatmapSetInfo> setInfo = null;
-
             // if the user has requested not to play theme music, we should attempt to find a random beatmap from their collection.
             if (!MenuMusic.Value)
             {
-                var sets = beatmaps.GetAllUsableBeatmapSets();
-
-                if (sets.Count > 0)
+                realmContextFactory.Run(realm =>
                 {
-                    setInfo = beatmaps.QueryBeatmapSet(s => s.ID == sets[RNG.Next(0, sets.Count - 1)].ID);
-                    setInfo?.PerformRead(s =>
-                    {
-                        if (s.Beatmaps.Count == 0)
-                            return;
+                    var usableBeatmapSets = realm.All<BeatmapSetInfo>().Where(s => !s.DeletePending && !s.Protected).AsRealmCollection();
 
-                        initialBeatmap = beatmaps.GetWorkingBeatmap(s.Beatmaps[0]);
-                    });
-                }
+                    int setCount = usableBeatmapSets.Count;
+
+                    if (setCount > 0)
+                    {
+                        var found = usableBeatmapSets[RNG.Next(0, setCount - 1)].Beatmaps.FirstOrDefault();
+
+                        if (found != null)
+                            initialBeatmap = beatmaps.GetWorkingBeatmap(found);
+                    }
+                });
             }
 
             // we generally want a song to be playing on startup, so use the intro music even if a user has specified not to if no other track is available.
-            if (setInfo == null)
+            if (initialBeatmap == null)
             {
                 if (!loadThemedIntro())
                 {
@@ -130,7 +130,7 @@ namespace osu.Game.Screens.Menu
 
             bool loadThemedIntro()
             {
-                setInfo = beatmaps.QueryBeatmapSet(b => b.Hash == BeatmapHash);
+                var setInfo = beatmaps.QueryBeatmapSet(b => b.Hash == BeatmapHash);
 
                 if (setInfo == null)
                     return false;

osu.Game/Screens/Menu/MenuSideFlashes.cs

@@ -94,9 +94,9 @@ namespace osu.Game.Screens.Menu
             if (beatIndex < 0)
                 return;
 
-            if (effectPoint.KiaiMode ? beatIndex % 2 == 0 : beatIndex % (int)timingPoint.TimeSignature == 0)
+            if (effectPoint.KiaiMode ? beatIndex % 2 == 0 : beatIndex % timingPoint.TimeSignature.Numerator == 0)
                 flash(leftBox, timingPoint.BeatLength, effectPoint.KiaiMode, amplitudes);
-            if (effectPoint.KiaiMode ? beatIndex % 2 == 1 : beatIndex % (int)timingPoint.TimeSignature == 0)
+            if (effectPoint.KiaiMode ? beatIndex % 2 == 1 : beatIndex % timingPoint.TimeSignature.Numerator == 0)
                 flash(rightBox, timingPoint.BeatLength, effectPoint.KiaiMode, amplitudes);
         }
 

osu.Game/Screens/Menu/OsuLogo.cs

@@ -282,7 +282,7 @@ namespace osu.Game.Screens.Menu
             {
                 this.Delay(early_activation).Schedule(() =>
                 {
-                    if (beatIndex % (int)timingPoint.TimeSignature == 0)
+                    if (beatIndex % timingPoint.TimeSignature.Numerator == 0)
                         sampleDownbeat.Play();
                     else
                         sampleBeat.Play();

osu.Game/Screens/Select/BeatmapCarousel.cs

@@ -190,13 +190,13 @@ namespace osu.Game.Screens.Select
         {
             base.LoadComplete();
 
-            subscriptionSets = getBeatmapSets(realmFactory.Context).QueryAsyncWithNotifications(beatmapSetsChanged);
-            subscriptionBeatmaps = realmFactory.Context.All<BeatmapInfo>().Where(b => !b.Hidden).QueryAsyncWithNotifications(beatmapsChanged);
+            subscriptionSets = realmFactory.RegisterForNotifications(getBeatmapSets, beatmapSetsChanged);
+            subscriptionBeatmaps = realmFactory.RegisterForNotifications(realm => realm.All<BeatmapInfo>().Where(b => !b.Hidden), beatmapsChanged);
 
             // Can't use main subscriptions because we can't lookup deleted indices.
             // https://github.com/realm/realm-dotnet/discussions/2634#discussioncomment-1605595.
-            subscriptionDeletedSets = realmFactory.Context.All<BeatmapSetInfo>().Where(s => s.DeletePending && !s.Protected).QueryAsyncWithNotifications(deletedBeatmapSetsChanged);
-            subscriptionHiddenBeatmaps = realmFactory.Context.All<BeatmapInfo>().Where(b => b.Hidden).QueryAsyncWithNotifications(beatmapsChanged);
+            subscriptionDeletedSets = realmFactory.RegisterForNotifications(realm => realm.All<BeatmapSetInfo>().Where(s => s.DeletePending && !s.Protected), deletedBeatmapSetsChanged);
+            subscriptionHiddenBeatmaps = realmFactory.RegisterForNotifications(realm => realm.All<BeatmapInfo>().Where(b => b.Hidden), beatmapsChanged);
         }
 
         private void deletedBeatmapSetsChanged(IRealmCollection<BeatmapSetInfo> sender, ChangeSet changes, Exception error)
@@ -274,7 +274,7 @@ namespace osu.Game.Screens.Select
             }
         }
 
-        private IRealmCollection<BeatmapSetInfo> getBeatmapSets(Realm realm) => realm.All<BeatmapSetInfo>().Where(s => !s.DeletePending && !s.Protected).AsRealmCollection();
+        private IQueryable<BeatmapSetInfo> getBeatmapSets(Realm realm) => realm.All<BeatmapSetInfo>().Where(s => !s.DeletePending && !s.Protected);
 
         public void RemoveBeatmapSet(BeatmapSetInfo beatmapSet) =>
             removeBeatmapSet(beatmapSet.ID);
@@ -552,10 +552,11 @@ namespace osu.Game.Screens.Select
 
         private void signalBeatmapsLoaded()
         {
-            Debug.Assert(BeatmapSetsLoaded == false);
-
-            BeatmapSetsChanged?.Invoke();
-            BeatmapSetsLoaded = true;
+            if (!BeatmapSetsLoaded)
+            {
+                BeatmapSetsChanged?.Invoke();
+                BeatmapSetsLoaded = true;
+            }
 
             itemsCache.Invalidate();
         }

osu.Game/Screens/Select/Carousel/TopLocalRank.cs

@@ -48,18 +48,19 @@ namespace osu.Game.Screens.Select.Carousel
             ruleset.BindValueChanged(_ =>
             {
                 scoreSubscription?.Dispose();
-                scoreSubscription = realmFactory.Context.All<ScoreInfo>()
-                                                .Filter($"{nameof(ScoreInfo.User)}.{nameof(RealmUser.OnlineID)} == $0"
-                                                        + $" && {nameof(ScoreInfo.BeatmapInfo)}.{nameof(BeatmapInfo.ID)} == $1"
-                                                        + $" && {nameof(ScoreInfo.Ruleset)}.{nameof(RulesetInfo.ShortName)} == $2"
-                                                        + $" && {nameof(ScoreInfo.DeletePending)} == false", api.LocalUser.Value.Id, beatmapInfo.ID, ruleset.Value.ShortName)
-                                                .OrderByDescending(s => s.TotalScore)
-                                                .QueryAsyncWithNotifications((items, changes, ___) =>
-                                                {
-                                                    Rank = items.FirstOrDefault()?.Rank;
-                                                    // Required since presence is changed via IsPresent override
-                                                    Invalidate(Invalidation.Presence);
-                                                });
+                scoreSubscription = realmFactory.RegisterForNotifications(realm =>
+                        realm.All<ScoreInfo>()
+                             .Filter($"{nameof(ScoreInfo.User)}.{nameof(RealmUser.OnlineID)} == $0"
+                                     + $" && {nameof(ScoreInfo.BeatmapInfo)}.{nameof(BeatmapInfo.ID)} == $1"
+                                     + $" && {nameof(ScoreInfo.Ruleset)}.{nameof(RulesetInfo.ShortName)} == $2"
+                                     + $" && {nameof(ScoreInfo.DeletePending)} == false", api.LocalUser.Value.Id, beatmapInfo.ID, ruleset.Value.ShortName)
+                             .OrderByDescending(s => s.TotalScore),
+                    (items, changes, ___) =>
+                    {
+                        Rank = items.FirstOrDefault()?.Rank;
+                        // Required since presence is changed via IsPresent override
+                        Invalidate(Invalidation.Presence);
+                    });
             }, true);
         }
 

osu.Game/Screens/Select/Leaderboards/BeatmapLeaderboard.cs

@@ -44,9 +44,13 @@ namespace osu.Game.Screens.Select.Leaderboards
                 beatmapInfo = value;
                 Scores = null;
 
-                UpdateScores();
-                if (IsLoaded)
-                    refreshRealmSubscription();
+                if (IsOnlineScope)
+                    UpdateScores();
+                else
+                {
+                    if (IsLoaded)
+                        refreshRealmSubscription();
+                }
             }
         }
 
@@ -109,15 +113,14 @@ namespace osu.Game.Screens.Select.Leaderboards
             if (beatmapInfo == null)
                 return;
 
-            scoreSubscription = realmFactory.Context.All<ScoreInfo>()
-                                            .Filter($"{nameof(ScoreInfo.BeatmapInfo)}.{nameof(BeatmapInfo.ID)} = $0", beatmapInfo.ID)
-                                            .QueryAsyncWithNotifications((_, changes, ___) =>
-                                            {
-                                                if (changes == null)
-                                                    return;
-
-                                                RefreshScores();
-                                            });
+            scoreSubscription = realmFactory.RegisterForNotifications(realm =>
+                    realm.All<ScoreInfo>()
+                         .Filter($"{nameof(ScoreInfo.BeatmapInfo)}.{nameof(BeatmapInfo.ID)} = $0", beatmapInfo.ID),
+                (_, changes, ___) =>
+                {
+                    if (!IsOnlineScope)
+                        RefreshScores();
+                });
         }
 
         protected override void Reset()

osu.Game/Screens/Spectate/SpectatorScreen.cs

@@ -17,6 +17,7 @@ using osu.Game.Online.Spectator;
 using osu.Game.Replays;
 using osu.Game.Rulesets;
 using osu.Game.Scoring;
+using Realms;
 
 namespace osu.Game.Screens.Spectate
 {
@@ -79,23 +80,21 @@ namespace osu.Game.Screens.Spectate
                 playingUserStates.BindTo(spectatorClient.PlayingUserStates);
                 playingUserStates.BindCollectionChanged(onPlayingUserStatesChanged, true);
 
-                realmSubscription = realmContextFactory.Context
-                                                       .All<BeatmapSetInfo>()
-                                                       .Where(s => !s.DeletePending)
-                                                       .QueryAsyncWithNotifications((items, changes, ___) =>
-                                                       {
-                                                           if (changes?.InsertedIndices == null)
-                                                               return;
-
-                                                           foreach (int c in changes.InsertedIndices)
-                                                               beatmapUpdated(items[c]);
-                                                       });
+                realmSubscription = realmContextFactory.RegisterForNotifications(
+                    realm => realm.All<BeatmapSetInfo>().Where(s => !s.DeletePending), beatmapsChanged);
 
                 foreach ((int id, var _) in userMap)
                     spectatorClient.WatchUser(id);
             }));
         }
 
+        private void beatmapsChanged(IRealmCollection<BeatmapSetInfo> items, ChangeSet changes, Exception ___)
+        {
+            if (changes?.InsertedIndices == null) return;
+
+            foreach (int c in changes.InsertedIndices) beatmapUpdated(items[c]);
+        }
+
         private void beatmapUpdated(BeatmapSetInfo beatmapSet)
         {
             foreach ((int userId, _) in userMap)

osu.Game/Tests/Visual/OsuGameTestScene.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
+using osu.Framework.Development;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
@@ -72,8 +73,11 @@ namespace osu.Game.Tests.Visual
         [TearDownSteps]
         public void TearDownSteps()
         {
-            AddStep("exit game", () => Game.Exit());
-            AddUntilStep("wait for game exit", () => Game.Parent == null);
+            if (DebugUtils.IsNUnitRunning)
+            {
+                AddStep("exit game", () => Game.Exit());
+                AddUntilStep("wait for game exit", () => Game.Parent == null);
+            }
         }
 
         protected void CreateGame()

osu.Game/Tests/Visual/ScreenTestScene.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Allocation;
+using osu.Framework.Development;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Logging;
@@ -48,7 +49,11 @@ namespace osu.Game.Tests.Visual
         public virtual void SetUpSteps() => addExitAllScreensStep();
 
         [TearDownSteps]
-        public virtual void TearDownSteps() => addExitAllScreensStep();
+        public virtual void TearDownSteps()
+        {
+            if (DebugUtils.IsNUnitRunning)
+                addExitAllScreensStep();
+        }
 
         private void addExitAllScreensStep()
         {

osu.Game/Users/Drawables/UpdateableFlag.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
@@ -23,6 +24,12 @@ namespace osu.Game.Users.Drawables
         /// </summary>
         public bool ShowPlaceholderOnNull = true;
 
+        /// <summary>
+        /// Perform an action in addition to showing the country ranking.
+        /// This should be used to perform auxiliary tasks and not as a primary action for clicking a flag (to maintain a consistent UX).
+        /// </summary>
+        public Action Action;
+
         public UpdateableFlag(Country country = null)
         {
             Country = country;
@@ -52,6 +59,7 @@ namespace osu.Game.Users.Drawables
 
         protected override bool OnClick(ClickEvent e)
         {
+            Action?.Invoke();
             rankingsOverlay?.ShowCountry(Country);
             return true;
         }

osu.Game/Users/ExtendedUserPanel.cs

@@ -53,7 +53,8 @@ namespace osu.Game.Users
 
         protected UpdateableFlag CreateFlag() => new UpdateableFlag(User.Country)
         {
-            Size = new Vector2(39, 26)
+            Size = new Vector2(39, 26),
+            Action = Action,
         };
 
         protected SpriteIcon CreateStatusIcon() => statusIcon = new SpriteIcon