Merge pull request #10079 from smoogipoo/collection-database

osu.Game.Tests/Collections/IO/ImportCollectionsTest.cs

@@ -0,0 +1,221 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.IO;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Platform;
+using osu.Game.Collections;
+using osu.Game.Tests.Resources;
+
+namespace osu.Game.Tests.Collections.IO
+{
+    [TestFixture]
+    public class ImportCollectionsTest
+    {
+        [Test]
+        public async Task TestImportEmptyDatabase()
+        {
+            using (HeadlessGameHost host = new CleanRunHeadlessGameHost())
+            {
+                try
+                {
+                    var osu = loadOsu(host);
+
+                    await osu.CollectionManager.Import(new MemoryStream());
+
+                    Assert.That(osu.CollectionManager.Collections.Count, Is.Zero);
+                }
+                finally
+                {
+                    host.Exit();
+                }
+            }
+        }
+
+        [Test]
+        public async Task TestImportWithNoBeatmaps()
+        {
+            using (HeadlessGameHost host = new CleanRunHeadlessGameHost())
+            {
+                try
+                {
+                    var osu = loadOsu(host);
+
+                    await osu.CollectionManager.Import(TestResources.OpenResource("Collections/collections.db"));
+
+                    Assert.That(osu.CollectionManager.Collections.Count, Is.EqualTo(2));
+
+                    Assert.That(osu.CollectionManager.Collections[0].Name.Value, Is.EqualTo("First"));
+                    Assert.That(osu.CollectionManager.Collections[0].Beatmaps.Count, Is.Zero);
+
+                    Assert.That(osu.CollectionManager.Collections[1].Name.Value, Is.EqualTo("Second"));
+                    Assert.That(osu.CollectionManager.Collections[1].Beatmaps.Count, Is.Zero);
+                }
+                finally
+                {
+                    host.Exit();
+                }
+            }
+        }
+
+        [Test]
+        public async Task TestImportWithBeatmaps()
+        {
+            using (HeadlessGameHost host = new CleanRunHeadlessGameHost())
+            {
+                try
+                {
+                    var osu = loadOsu(host, true);
+
+                    await osu.CollectionManager.Import(TestResources.OpenResource("Collections/collections.db"));
+
+                    Assert.That(osu.CollectionManager.Collections.Count, Is.EqualTo(2));
+
+                    Assert.That(osu.CollectionManager.Collections[0].Name.Value, Is.EqualTo("First"));
+                    Assert.That(osu.CollectionManager.Collections[0].Beatmaps.Count, Is.EqualTo(1));
+
+                    Assert.That(osu.CollectionManager.Collections[1].Name.Value, Is.EqualTo("Second"));
+                    Assert.That(osu.CollectionManager.Collections[1].Beatmaps.Count, Is.EqualTo(12));
+                }
+                finally
+                {
+                    host.Exit();
+                }
+            }
+        }
+
+        [Test]
+        public async Task TestImportMalformedDatabase()
+        {
+            bool exceptionThrown = false;
+            UnhandledExceptionEventHandler setException = (_, __) => exceptionThrown = true;
+
+            using (HeadlessGameHost host = new CleanRunHeadlessGameHost())
+            {
+                try
+                {
+                    AppDomain.CurrentDomain.UnhandledException += setException;
+
+                    var osu = loadOsu(host, true);
+
+                    using (var ms = new MemoryStream())
+                    {
+                        using (var bw = new BinaryWriter(ms, Encoding.UTF8, true))
+                        {
+                            for (int i = 0; i < 10000; i++)
+                                bw.Write((byte)i);
+                        }
+
+                        ms.Seek(0, SeekOrigin.Begin);
+
+                        await osu.CollectionManager.Import(ms);
+                    }
+
+                    Assert.That(host.UpdateThread.Running, Is.True);
+                    Assert.That(exceptionThrown, Is.False);
+                    Assert.That(osu.CollectionManager.Collections.Count, Is.EqualTo(0));
+                }
+                finally
+                {
+                    host.Exit();
+                    AppDomain.CurrentDomain.UnhandledException -= setException;
+                }
+            }
+        }
+
+        [Test]
+        public async Task TestSaveAndReload()
+        {
+            using (HeadlessGameHost host = new CleanRunHeadlessGameHost())
+            {
+                try
+                {
+                    var osu = loadOsu(host, true);
+
+                    await osu.CollectionManager.Import(TestResources.OpenResource("Collections/collections.db"));
+
+                    // Move first beatmap from second collection into the first.
+                    osu.CollectionManager.Collections[0].Beatmaps.Add(osu.CollectionManager.Collections[1].Beatmaps[0]);
+                    osu.CollectionManager.Collections[1].Beatmaps.RemoveAt(0);
+
+                    // Rename the second collecction.
+                    osu.CollectionManager.Collections[1].Name.Value = "Another";
+                }
+                finally
+                {
+                    host.Exit();
+                }
+            }
+
+            using (HeadlessGameHost host = new HeadlessGameHost("TestSaveAndReload"))
+            {
+                try
+                {
+                    var osu = loadOsu(host, true);
+
+                    Assert.That(osu.CollectionManager.Collections.Count, Is.EqualTo(2));
+
+                    Assert.That(osu.CollectionManager.Collections[0].Name.Value, Is.EqualTo("First"));
+                    Assert.That(osu.CollectionManager.Collections[0].Beatmaps.Count, Is.EqualTo(2));
+
+                    Assert.That(osu.CollectionManager.Collections[1].Name.Value, Is.EqualTo("Another"));
+                    Assert.That(osu.CollectionManager.Collections[1].Beatmaps.Count, Is.EqualTo(11));
+                }
+                finally
+                {
+                    host.Exit();
+                }
+            }
+        }
+
+        private TestOsuGameBase loadOsu(GameHost host, bool withBeatmap = false)
+        {
+            var osu = new TestOsuGameBase(withBeatmap);
+
+#pragma warning disable 4014
+            Task.Run(() => host.Run(osu));
+#pragma warning restore 4014
+
+            waitForOrAssert(() => osu.IsLoaded, @"osu! failed to start in a reasonable amount of time");
+
+            return osu;
+        }
+
+        private void waitForOrAssert(Func<bool> result, string failureMessage, int timeout = 60000)
+        {
+            Task task = Task.Run(() =>
+            {
+                while (!result()) Thread.Sleep(200);
+            });
+
+            Assert.IsTrue(task.Wait(timeout), failureMessage);
+        }
+
+        private class TestOsuGameBase : OsuGameBase
+        {
+            public CollectionManager CollectionManager { get; private set; }
+
+            private readonly bool withBeatmap;
+
+            public TestOsuGameBase(bool withBeatmap)
+            {
+                this.withBeatmap = withBeatmap;
+            }
+
+            [BackgroundDependencyLoader]
+            private void load()
+            {
+                // Beatmap must be imported before the collection manager is loaded.
+                if (withBeatmap)
+                    BeatmapManager.Import(TestResources.GetTestBeatmapForImport()).Wait();
+
+                AddInternal(CollectionManager = new CollectionManager(Storage));
+            }
+        }
+    }
+}

osu.Game.Tests/Visual/Collections/TestSceneManageCollectionsDialog.cs

@@ -0,0 +1,244 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.UserInterface;
+using osu.Framework.Platform;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps;
+using osu.Game.Collections;
+using osu.Game.Overlays;
+using osu.Game.Overlays.Dialog;
+using osu.Game.Rulesets;
+using osu.Game.Tests.Resources;
+using osuTK;
+using osuTK.Input;
+
+namespace osu.Game.Tests.Visual.Collections
+{
+    public class TestSceneManageCollectionsDialog : OsuManualInputManagerTestScene
+    {
+        protected override Container<Drawable> Content => content;
+
+        private readonly Container content;
+        private readonly DialogOverlay dialogOverlay;
+        private readonly CollectionManager manager;
+
+        private RulesetStore rulesets;
+        private BeatmapManager beatmapManager;
+
+        private ManageCollectionsDialog dialog;
+
+        public TestSceneManageCollectionsDialog()
+        {
+            base.Content.AddRange(new Drawable[]
+            {
+                manager = new CollectionManager(LocalStorage),
+                content = new Container { RelativeSizeAxes = Axes.Both },
+                dialogOverlay = new DialogOverlay()
+            });
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(GameHost host)
+        {
+            Dependencies.Cache(rulesets = new RulesetStore(ContextFactory));
+            Dependencies.Cache(beatmapManager = new BeatmapManager(LocalStorage, ContextFactory, rulesets, null, Audio, host, Beatmap.Default));
+
+            beatmapManager.Import(TestResources.GetTestBeatmapForImport()).Wait();
+        }
+
+        protected override IReadOnlyDependencyContainer CreateChildDependencies(IReadOnlyDependencyContainer parent)
+        {
+            var dependencies = new DependencyContainer(base.CreateChildDependencies(parent));
+            dependencies.Cache(manager);
+            dependencies.Cache(dialogOverlay);
+            return dependencies;
+        }
+
+        [SetUp]
+        public void SetUp() => Schedule(() =>
+        {
+            manager.Collections.Clear();
+            Child = dialog = new ManageCollectionsDialog();
+        });
+
+        [SetUpSteps]
+        public void SetUpSteps()
+        {
+            AddStep("show dialog", () => dialog.Show());
+        }
+
+        [Test]
+        public void TestHideDialog()
+        {
+            AddWaitStep("wait for animation", 3);
+            AddStep("hide dialog", () => dialog.Hide());
+        }
+
+        [Test]
+        public void TestLastItemIsPlaceholder()
+        {
+            AddAssert("last item is placeholder", () => !manager.Collections.Contains(dialog.ChildrenOfType<DrawableCollectionListItem>().Last().Model));
+        }
+
+        [Test]
+        public void TestAddCollectionExternal()
+        {
+            AddStep("add collection", () => manager.Collections.Add(new BeatmapCollection { Name = { Value = "First collection" } }));
+            assertCollectionCount(1);
+            assertCollectionName(0, "First collection");
+
+            AddStep("add another collection", () => manager.Collections.Add(new BeatmapCollection { Name = { Value = "Second collection" } }));
+            assertCollectionCount(2);
+            assertCollectionName(1, "Second collection");
+        }
+
+        [Test]
+        public void TestFocusPlaceholderDoesNotCreateCollection()
+        {
+            AddStep("focus placeholder", () =>
+            {
+                InputManager.MoveMouseTo(dialog.ChildrenOfType<DrawableCollectionListItem>().Last());
+                InputManager.Click(MouseButton.Left);
+            });
+
+            assertCollectionCount(0);
+        }
+
+        [Test]
+        public void TestAddCollectionViaPlaceholder()
+        {
+            DrawableCollectionListItem placeholderItem = null;
+
+            AddStep("focus placeholder", () =>
+            {
+                InputManager.MoveMouseTo(placeholderItem = dialog.ChildrenOfType<DrawableCollectionListItem>().Last());
+                InputManager.Click(MouseButton.Left);
+            });
+
+            // Done directly via the collection since InputManager methods cannot add text to textbox...
+            AddStep("change collection name", () => placeholderItem.Model.Name.Value = "a");
+            assertCollectionCount(1);
+            AddAssert("collection now exists", () => manager.Collections.Contains(placeholderItem.Model));
+
+            AddAssert("last item is placeholder", () => !manager.Collections.Contains(dialog.ChildrenOfType<DrawableCollectionListItem>().Last().Model));
+        }
+
+        [Test]
+        public void TestRemoveCollectionExternal()
+        {
+            AddStep("add two collections", () => manager.Collections.AddRange(new[]
+            {
+                new BeatmapCollection { Name = { Value = "1" } },
+                new BeatmapCollection { Name = { Value = "2" } },
+            }));
+
+            AddStep("remove first collection", () => manager.Collections.RemoveAt(0));
+            assertCollectionCount(1);
+            assertCollectionName(0, "2");
+        }
+
+        [Test]
+        public void TestRemoveCollectionViaButton()
+        {
+            AddStep("add two collections", () => manager.Collections.AddRange(new[]
+            {
+                new BeatmapCollection { Name = { Value = "1" } },
+                new BeatmapCollection { Name = { Value = "2" }, Beatmaps = { beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps[0] } },
+            }));
+
+            assertCollectionCount(2);
+
+            AddStep("click first delete button", () =>
+            {
+                InputManager.MoveMouseTo(dialog.ChildrenOfType<DrawableCollectionListItem.DeleteButton>().First(), new Vector2(5, 0));
+                InputManager.Click(MouseButton.Left);
+            });
+
+            AddAssert("dialog not displayed", () => dialogOverlay.CurrentDialog == null);
+            assertCollectionCount(1);
+            assertCollectionName(0, "2");
+
+            AddStep("click first delete button", () =>
+            {
+                InputManager.MoveMouseTo(dialog.ChildrenOfType<DrawableCollectionListItem.DeleteButton>().First(), new Vector2(5, 0));
+                InputManager.Click(MouseButton.Left);
+            });
+
+            AddAssert("dialog displayed", () => dialogOverlay.CurrentDialog is DeleteCollectionDialog);
+            AddStep("click confirmation", () =>
+            {
+                InputManager.MoveMouseTo(dialogOverlay.CurrentDialog.ChildrenOfType<PopupDialogButton>().First());
+                InputManager.Click(MouseButton.Left);
+            });
+
+            assertCollectionCount(0);
+        }
+
+        [Test]
+        public void TestCollectionNotRemovedWhenDialogCancelled()
+        {
+            AddStep("add two collections", () => manager.Collections.AddRange(new[]
+            {
+                new BeatmapCollection { Name = { Value = "1" }, Beatmaps = { beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps[0] } },
+            }));
+
+            assertCollectionCount(1);
+
+            AddStep("click first delete button", () =>
+            {
+                InputManager.MoveMouseTo(dialog.ChildrenOfType<DrawableCollectionListItem.DeleteButton>().First(), new Vector2(5, 0));
+                InputManager.Click(MouseButton.Left);
+            });
+
+            AddAssert("dialog displayed", () => dialogOverlay.CurrentDialog is DeleteCollectionDialog);
+            AddStep("click cancellation", () =>
+            {
+                InputManager.MoveMouseTo(dialogOverlay.CurrentDialog.ChildrenOfType<PopupDialogButton>().Last());
+                InputManager.Click(MouseButton.Left);
+            });
+
+            assertCollectionCount(1);
+        }
+
+        [Test]
+        public void TestCollectionRenamedExternal()
+        {
+            AddStep("add two collections", () => manager.Collections.AddRange(new[]
+            {
+                new BeatmapCollection { Name = { Value = "1" } },
+                new BeatmapCollection { Name = { Value = "2" } },
+            }));
+
+            AddStep("change first collection name", () => manager.Collections[0].Name.Value = "First");
+
+            assertCollectionName(0, "First");
+        }
+
+        [Test]
+        public void TestCollectionRenamedOnTextChange()
+        {
+            AddStep("add two collections", () => manager.Collections.AddRange(new[]
+            {
+                new BeatmapCollection { Name = { Value = "1" } },
+                new BeatmapCollection { Name = { Value = "2" } },
+            }));
+
+            assertCollectionCount(2);
+
+            AddStep("change first collection name", () => dialog.ChildrenOfType<TextBox>().First().Text = "First");
+            AddAssert("collection has new name", () => manager.Collections[0].Name.Value == "First");
+        }
+
+        private void assertCollectionCount(int count)
+            => AddUntilStep($"{count} collections shown", () => dialog.ChildrenOfType<DrawableCollectionListItem>().Count(i => i.IsCreated.Value) == count);
+
+        private void assertCollectionName(int index, string name)
+            => AddUntilStep($"item {index + 1} has correct name", () => dialog.ChildrenOfType<DrawableCollectionListItem>().ElementAt(index).ChildrenOfType<TextBox>().First().Text == name);
+    }
+}

osu.Game.Tests/Visual/SongSelect/TestSceneFilterControl.cs

@@ -0,0 +1,237 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using System.Linq;
+using NUnit.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.UserInterface;
+using osu.Framework.Platform;
+using osu.Framework.Testing;
+using osu.Game.Beatmaps;
+using osu.Game.Collections;
+using osu.Game.Graphics.UserInterface;
+using osu.Game.Rulesets;
+using osu.Game.Screens.Select;
+using osu.Game.Tests.Resources;
+using osuTK.Input;
+
+namespace osu.Game.Tests.Visual.SongSelect
+{
+    public class TestSceneFilterControl : OsuManualInputManagerTestScene
+    {
+        protected override Container<Drawable> Content => content;
+        private readonly Container content;
+
+        private readonly CollectionManager collectionManager;
+
+        private RulesetStore rulesets;
+        private BeatmapManager beatmapManager;
+
+        private FilterControl control;
+
+        public TestSceneFilterControl()
+        {
+            base.Content.AddRange(new Drawable[]
+            {
+                collectionManager = new CollectionManager(LocalStorage),
+                content = new Container { RelativeSizeAxes = Axes.Both }
+            });
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(GameHost host)
+        {
+            Dependencies.Cache(rulesets = new RulesetStore(ContextFactory));
+            Dependencies.Cache(beatmapManager = new BeatmapManager(LocalStorage, ContextFactory, rulesets, null, Audio, host, Beatmap.Default));
+
+            beatmapManager.Import(TestResources.GetTestBeatmapForImport()).Wait();
+        }
+
+        protected override IReadOnlyDependencyContainer CreateChildDependencies(IReadOnlyDependencyContainer parent)
+        {
+            var dependencies = new DependencyContainer(base.CreateChildDependencies(parent));
+            dependencies.Cache(collectionManager);
+            return dependencies;
+        }
+
+        [SetUp]
+        public void SetUp() => Schedule(() =>
+        {
+            collectionManager.Collections.Clear();
+
+            Child = control = new FilterControl
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                RelativeSizeAxes = Axes.X,
+                Height = FilterControl.HEIGHT,
+            };
+        });
+
+        [Test]
+        public void TestEmptyCollectionFilterContainsAllBeatmaps()
+        {
+            assertCollectionDropdownContains("All beatmaps");
+            assertCollectionHeaderDisplays("All beatmaps");
+        }
+
+        [Test]
+        public void TestCollectionAddedToDropdown()
+        {
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "2" } }));
+            assertCollectionDropdownContains("1");
+            assertCollectionDropdownContains("2");
+        }
+
+        [Test]
+        public void TestCollectionRemovedFromDropdown()
+        {
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "2" } }));
+            AddStep("remove collection", () => collectionManager.Collections.RemoveAt(0));
+
+            assertCollectionDropdownContains("1", false);
+            assertCollectionDropdownContains("2");
+        }
+
+        [Test]
+        public void TestCollectionRenamed()
+        {
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddStep("select collection", () =>
+            {
+                var dropdown = control.ChildrenOfType<CollectionFilterDropdown>().Single();
+                dropdown.Current.Value = dropdown.ItemSource.ElementAt(1);
+            });
+
+            addExpandHeaderStep();
+
+            AddStep("change name", () => collectionManager.Collections[0].Name.Value = "First");
+
+            assertCollectionDropdownContains("First");
+            assertCollectionHeaderDisplays("First");
+        }
+
+        [Test]
+        public void TestAllBeatmapFilterDoesNotHaveAddButton()
+        {
+            addExpandHeaderStep();
+            AddStep("hover all beatmaps", () => InputManager.MoveMouseTo(getAddOrRemoveButton(0)));
+            AddAssert("'All beatmaps' filter does not have add button", () => !getAddOrRemoveButton(0).IsPresent);
+        }
+
+        [Test]
+        public void TestCollectionFilterHasAddButton()
+        {
+            addExpandHeaderStep();
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddStep("hover collection", () => InputManager.MoveMouseTo(getAddOrRemoveButton(1)));
+            AddAssert("collection has add button", () => getAddOrRemoveButton(1).IsPresent);
+        }
+
+        [Test]
+        public void TestButtonDisabledAndEnabledWithBeatmapChanges()
+        {
+            addExpandHeaderStep();
+
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+
+            AddStep("select available beatmap", () => Beatmap.Value = beatmapManager.GetWorkingBeatmap(beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps[0]));
+            AddAssert("button enabled", () => getAddOrRemoveButton(1).Enabled.Value);
+
+            AddStep("set dummy beatmap", () => Beatmap.SetDefault());
+            AddAssert("button disabled", () => !getAddOrRemoveButton(1).Enabled.Value);
+        }
+
+        [Test]
+        public void TestButtonChangesWhenAddedAndRemovedFromCollection()
+        {
+            addExpandHeaderStep();
+
+            AddStep("select available beatmap", () => Beatmap.Value = beatmapManager.GetWorkingBeatmap(beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps[0]));
+
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddAssert("button is plus", () => getAddOrRemoveButton(1).Icon.Equals(FontAwesome.Solid.PlusSquare));
+
+            AddStep("add beatmap to collection", () => collectionManager.Collections[0].Beatmaps.Add(Beatmap.Value.BeatmapInfo));
+            AddAssert("button is minus", () => getAddOrRemoveButton(1).Icon.Equals(FontAwesome.Solid.MinusSquare));
+
+            AddStep("remove beatmap from collection", () => collectionManager.Collections[0].Beatmaps.Clear());
+            AddAssert("button is plus", () => getAddOrRemoveButton(1).Icon.Equals(FontAwesome.Solid.PlusSquare));
+        }
+
+        [Test]
+        public void TestButtonAddsAndRemovesBeatmap()
+        {
+            addExpandHeaderStep();
+
+            AddStep("select available beatmap", () => Beatmap.Value = beatmapManager.GetWorkingBeatmap(beatmapManager.GetAllUsableBeatmapSets().First().Beatmaps[0]));
+
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddAssert("button is plus", () => getAddOrRemoveButton(1).Icon.Equals(FontAwesome.Solid.PlusSquare));
+
+            addClickAddOrRemoveButtonStep(1);
+            AddAssert("collection contains beatmap", () => collectionManager.Collections[0].Beatmaps.Contains(Beatmap.Value.BeatmapInfo));
+            AddAssert("button is minus", () => getAddOrRemoveButton(1).Icon.Equals(FontAwesome.Solid.MinusSquare));
+
+            addClickAddOrRemoveButtonStep(1);
+            AddAssert("collection does not contain beatmap", () => !collectionManager.Collections[0].Beatmaps.Contains(Beatmap.Value.BeatmapInfo));
+            AddAssert("button is plus", () => getAddOrRemoveButton(1).Icon.Equals(FontAwesome.Solid.PlusSquare));
+        }
+
+        [Test]
+        public void TestManageCollectionsFilterIsNotSelected()
+        {
+            addExpandHeaderStep();
+
+            AddStep("add collection", () => collectionManager.Collections.Add(new BeatmapCollection { Name = { Value = "1" } }));
+            AddStep("select collection", () =>
+            {
+                InputManager.MoveMouseTo(getCollectionDropdownItems().ElementAt(1));
+                InputManager.Click(MouseButton.Left);
+            });
+
+            addExpandHeaderStep();
+
+            AddStep("click manage collections filter", () =>
+            {
+                InputManager.MoveMouseTo(getCollectionDropdownItems().Last());
+                InputManager.Click(MouseButton.Left);
+            });
+
+            AddAssert("collection filter still selected", () => control.CreateCriteria().Collection?.Name.Value == "1");
+        }
+
+        private void assertCollectionHeaderDisplays(string collectionName, bool shouldDisplay = true)
+            => AddAssert($"collection dropdown header displays '{collectionName}'",
+                () => shouldDisplay == (control.ChildrenOfType<CollectionFilterDropdown.CollectionDropdownHeader>().Single().ChildrenOfType<SpriteText>().First().Text == collectionName));
+
+        private void assertCollectionDropdownContains(string collectionName, bool shouldContain = true) =>
+            AddAssert($"collection dropdown {(shouldContain ? "contains" : "does not contain")} '{collectionName}'",
+                // A bit of a roundabout way of going about this, see: https://github.com/ppy/osu-framework/issues/3871 + https://github.com/ppy/osu-framework/issues/3872
+                () => shouldContain == (getCollectionDropdownItems().Any(i => i.ChildrenOfType<FillFlowContainer>().OfType<IHasText>().First().Text == collectionName)));
+
+        private IconButton getAddOrRemoveButton(int index)
+            => getCollectionDropdownItems().ElementAt(index).ChildrenOfType<IconButton>().Single();
+
+        private void addExpandHeaderStep() => AddStep("expand header", () =>
+        {
+            InputManager.MoveMouseTo(control.ChildrenOfType<CollectionFilterDropdown.CollectionDropdownHeader>().Single());
+            InputManager.Click(MouseButton.Left);
+        });
+
+        private void addClickAddOrRemoveButtonStep(int index) => AddStep("click add or remove button", () =>
+        {
+            InputManager.MoveMouseTo(getAddOrRemoveButton(index));
+            InputManager.Click(MouseButton.Left);
+        });
+
+        private IEnumerable<Dropdown<CollectionMenuItem>.DropdownMenu.DrawableDropdownMenuItem> getCollectionDropdownItems()
+            => control.ChildrenOfType<CollectionFilterDropdown>().Single().ChildrenOfType<Dropdown<CollectionMenuItem>.DropdownMenu.DrawableDropdownMenuItem>();
+    }
+}

osu.Game/Collections/BeatmapCollection.cs

@@ -0,0 +1,47 @@
+// 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.Bindables;
+using osu.Game.Beatmaps;
+
+namespace osu.Game.Collections
+{
+    /// <summary>
+    /// A collection of beatmaps grouped by a name.
+    /// </summary>
+    public class BeatmapCollection
+    {
+        /// <summary>
+        /// Invoked whenever any change occurs on this <see cref="BeatmapCollection"/>.
+        /// </summary>
+        public event Action Changed;
+
+        /// <summary>
+        /// The collection's name.
+        /// </summary>
+        public readonly Bindable<string> Name = new Bindable<string>();
+
+        /// <summary>
+        /// The beatmaps contained by the collection.
+        /// </summary>
+        public readonly BindableList<BeatmapInfo> Beatmaps = new BindableList<BeatmapInfo>();
+
+        /// <summary>
+        /// The date when this collection was last modified.
+        /// </summary>
+        public DateTimeOffset LastModifyDate { get; private set; } = DateTimeOffset.UtcNow;
+
+        public BeatmapCollection()
+        {
+            Beatmaps.CollectionChanged += (_, __) => onChange();
+            Name.ValueChanged += _ => onChange();
+        }
+
+        private void onChange()
+        {
+            LastModifyDate = DateTimeOffset.Now;
+            Changed?.Invoke();
+        }
+    }
+}

osu.Game/Collections/CollectionManager.cs

@@ -0,0 +1,303 @@
+// 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.Collections.Specialized;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using osu.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Logging;
+using osu.Framework.Platform;
+using osu.Game.Beatmaps;
+using osu.Game.IO.Legacy;
+using osu.Game.Overlays.Notifications;
+
+namespace osu.Game.Collections
+{
+    /// <summary>
+    /// Handles user-defined collections of beatmaps.
+    /// </summary>
+    /// <remarks>
+    /// This is currently reading and writing from the osu-stable file format. This is a temporary arrangement until we refactor the
+    /// database backing the game. Going forward writing should be done in a similar way to other model stores.
+    /// </remarks>
+    public class CollectionManager : Component
+    {
+        /// <summary>
+        /// Database version in stable-compatible YYYYMMDD format.
+        /// </summary>
+        private const int database_version = 30000000;
+
+        private const string database_name = "collection.db";
+
+        public readonly BindableList<BeatmapCollection> Collections = new BindableList<BeatmapCollection>();
+
+        public bool SupportsImportFromStable => RuntimeInfo.IsDesktop;
+
+        [Resolved]
+        private GameHost host { get; set; }
+
+        [Resolved]
+        private BeatmapManager beatmaps { get; set; }
+
+        private readonly Storage storage;
+
+        public CollectionManager(Storage storage)
+        {
+            this.storage = storage;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            Collections.CollectionChanged += collectionsChanged;
+
+            if (storage.Exists(database_name))
+            {
+                using (var stream = storage.GetStream(database_name))
+                    importCollections(readCollections(stream));
+            }
+        }
+
+        private void collectionsChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    foreach (var c in e.NewItems.Cast<BeatmapCollection>())
+                        c.Changed += backgroundSave;
+                    break;
+
+                case NotifyCollectionChangedAction.Remove:
+                    foreach (var c in e.OldItems.Cast<BeatmapCollection>())
+                        c.Changed -= backgroundSave;
+                    break;
+
+                case NotifyCollectionChangedAction.Replace:
+                    foreach (var c in e.OldItems.Cast<BeatmapCollection>())
+                        c.Changed -= backgroundSave;
+
+                    foreach (var c in e.NewItems.Cast<BeatmapCollection>())
+                        c.Changed += backgroundSave;
+                    break;
+            }
+
+            backgroundSave();
+        }
+
+        /// <summary>
+        /// Set an endpoint for notifications to be posted to.
+        /// </summary>
+        public Action<Notification> PostNotification { protected get; set; }
+
+        /// <summary>
+        /// Set a storage with access to an osu-stable install for import purposes.
+        /// </summary>
+        public Func<Storage> GetStableStorage { private get; set; }
+
+        /// <summary>
+        /// This is a temporary method and will likely be replaced by a full-fledged (and more correctly placed) migration process in the future.
+        /// </summary>
+        public Task ImportFromStableAsync()
+        {
+            var stable = GetStableStorage?.Invoke();
+
+            if (stable == null)
+            {
+                Logger.Log("No osu!stable installation available!", LoggingTarget.Information, LogLevel.Error);
+                return Task.CompletedTask;
+            }
+
+            if (!stable.Exists(database_name))
+            {
+                // This handles situations like when the user does not have a collections.db file
+                Logger.Log($"No {database_name} available in osu!stable installation", LoggingTarget.Information, LogLevel.Error);
+                return Task.CompletedTask;
+            }
+
+            return Task.Run(async () =>
+            {
+                using (var stream = stable.GetStream(database_name))
+                    await Import(stream);
+            });
+        }
+
+        public async Task Import(Stream stream)
+        {
+            var notification = new ProgressNotification
+            {
+                State = ProgressNotificationState.Active,
+                Text = "Collections import is initialising..."
+            };
+
+            PostNotification?.Invoke(notification);
+
+            var collection = readCollections(stream, notification);
+            bool importCompleted = false;
+
+            Schedule(() =>
+            {
+                importCollections(collection);
+                importCompleted = true;
+            });
+
+            while (!IsDisposed && !importCompleted)
+                await Task.Delay(10);
+
+            notification.CompletionText = $"Imported {collection.Count} collections";
+            notification.State = ProgressNotificationState.Completed;
+        }
+
+        private void importCollections(List<BeatmapCollection> newCollections)
+        {
+            foreach (var newCol in newCollections)
+            {
+                var existing = Collections.FirstOrDefault(c => c.Name == newCol.Name);
+                if (existing == null)
+                    Collections.Add(existing = new BeatmapCollection { Name = { Value = newCol.Name.Value } });
+
+                foreach (var newBeatmap in newCol.Beatmaps)
+                {
+                    if (!existing.Beatmaps.Contains(newBeatmap))
+                        existing.Beatmaps.Add(newBeatmap);
+                }
+            }
+        }
+
+        private List<BeatmapCollection> readCollections(Stream stream, ProgressNotification notification = null)
+        {
+            if (notification != null)
+            {
+                notification.Text = "Reading collections...";
+                notification.Progress = 0;
+            }
+
+            var result = new List<BeatmapCollection>();
+
+            try
+            {
+                using (var sr = new SerializationReader(stream))
+                {
+                    sr.ReadInt32(); // Version
+
+                    int collectionCount = sr.ReadInt32();
+                    result.Capacity = collectionCount;
+
+                    for (int i = 0; i < collectionCount; i++)
+                    {
+                        if (notification?.CancellationToken.IsCancellationRequested == true)
+                            return result;
+
+                        var collection = new BeatmapCollection { Name = { Value = sr.ReadString() } };
+                        int mapCount = sr.ReadInt32();
+
+                        for (int j = 0; j < mapCount; j++)
+                        {
+                            if (notification?.CancellationToken.IsCancellationRequested == true)
+                                return result;
+
+                            string checksum = sr.ReadString();
+
+                            var beatmap = beatmaps.QueryBeatmap(b => b.MD5Hash == checksum);
+                            if (beatmap != null)
+                                collection.Beatmaps.Add(beatmap);
+                        }
+
+                        if (notification != null)
+                        {
+                            notification.Text = $"Imported {i + 1} of {collectionCount} collections";
+                            notification.Progress = (float)(i + 1) / collectionCount;
+                        }
+
+                        result.Add(collection);
+                    }
+                }
+            }
+            catch (Exception e)
+            {
+                Logger.Error(e, "Failed to read collection database.");
+            }
+
+            return result;
+        }
+
+        public void DeleteAll()
+        {
+            Collections.Clear();
+            PostNotification?.Invoke(new SimpleNotification { Text = "Deleted all collections!" });
+        }
+
+        private readonly object saveLock = new object();
+        private int lastSave;
+        private int saveFailures;
+
+        /// <summary>
+        /// Perform a save with debounce.
+        /// </summary>
+        private void backgroundSave()
+        {
+            var current = Interlocked.Increment(ref lastSave);
+            Task.Delay(100).ContinueWith(task =>
+            {
+                if (current != lastSave)
+                    return;
+
+                if (!save())
+                    backgroundSave();
+            });
+        }
+
+        private bool save()
+        {
+            lock (saveLock)
+            {
+                Interlocked.Increment(ref lastSave);
+
+                try
+                {
+                    // This is NOT thread-safe!!
+
+                    using (var sw = new SerializationWriter(storage.GetStream(database_name, FileAccess.Write)))
+                    {
+                        sw.Write(database_version);
+                        sw.Write(Collections.Count);
+
+                        foreach (var c in Collections)
+                        {
+                            sw.Write(c.Name.Value);
+                            sw.Write(c.Beatmaps.Count);
+
+                            foreach (var b in c.Beatmaps)
+                                sw.Write(b.MD5Hash);
+                        }
+                    }
+
+                    if (saveFailures < 10)
+                        saveFailures = 0;
+                    return true;
+                }
+                catch (Exception e)
+                {
+                    // Since this code is not thread-safe, we may run into random exceptions (such as collection enumeration or out of range indexing).
+                    // Failures are thus only alerted if they exceed a threshold (once) to indicate "actual" errors having occurred.
+                    if (++saveFailures == 10)
+                        Logger.Error(e, "Failed to save collection database!");
+                }
+
+                return false;
+            }
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+            save();
+        }
+    }
+}

osu.Game/Collections/DeleteCollectionDialog.cs

@@ -0,0 +1,34 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using Humanizer;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Overlays.Dialog;
+
+namespace osu.Game.Collections
+{
+    public class DeleteCollectionDialog : PopupDialog
+    {
+        public DeleteCollectionDialog(BeatmapCollection collection, Action deleteAction)
+        {
+            HeaderText = "Confirm deletion of";
+            BodyText = $"{collection.Name.Value} ({"beatmap".ToQuantity(collection.Beatmaps.Count)})";
+
+            Icon = FontAwesome.Regular.TrashAlt;
+
+            Buttons = new PopupDialogButton[]
+            {
+                new PopupDialogOkButton
+                {
+                    Text = @"Yes. Go for it.",
+                    Action = deleteAction
+                },
+                new PopupDialogCancelButton
+                {
+                    Text = @"No! Abort mission!",
+                },
+            };
+        }
+    }
+}

osu.Game/Collections/DrawableCollectionList.cs

@@ -0,0 +1,122 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Graphics.Containers;
+using osuTK;
+
+namespace osu.Game.Collections
+{
+    /// <summary>
+    /// Visualises a list of <see cref="BeatmapCollection"/>s.
+    /// </summary>
+    public class DrawableCollectionList : OsuRearrangeableListContainer<BeatmapCollection>
+    {
+        private Scroll scroll;
+
+        protected override ScrollContainer<Drawable> CreateScrollContainer() => scroll = new Scroll();
+
+        protected override FillFlowContainer<RearrangeableListItem<BeatmapCollection>> CreateListFillFlowContainer() => new Flow
+        {
+            DragActive = { BindTarget = DragActive }
+        };
+
+        protected override OsuRearrangeableListItem<BeatmapCollection> CreateOsuDrawable(BeatmapCollection item)
+        {
+            if (item == scroll.PlaceholderItem.Model)
+                return scroll.ReplacePlaceholder();
+
+            return new DrawableCollectionListItem(item, true);
+        }
+
+        /// <summary>
+        /// The scroll container for this <see cref="DrawableCollectionList"/>.
+        /// Contains the main flow of <see cref="DrawableCollectionListItem"/> and attaches a placeholder item to the end of the list.
+        /// </summary>
+        /// <remarks>
+        /// Use <see cref="ReplacePlaceholder"/> to transfer the placeholder into the main list.
+        /// </remarks>
+        private class Scroll : OsuScrollContainer
+        {
+            /// <summary>
+            /// The currently-displayed placeholder item.
+            /// </summary>
+            public DrawableCollectionListItem PlaceholderItem { get; private set; }
+
+            protected override Container<Drawable> Content => content;
+            private readonly Container content;
+
+            private readonly Container<DrawableCollectionListItem> placeholderContainer;
+
+            public Scroll()
+            {
+                ScrollbarVisible = false;
+                Padding = new MarginPadding(10);
+
+                base.Content.Add(new FillFlowContainer
+                {
+                    RelativeSizeAxes = Axes.X,
+                    AutoSizeAxes = Axes.Y,
+                    LayoutDuration = 200,
+                    LayoutEasing = Easing.OutQuint,
+                    Children = new Drawable[]
+                    {
+                        content = new Container { RelativeSizeAxes = Axes.X },
+                        placeholderContainer = new Container<DrawableCollectionListItem>
+                        {
+                            RelativeSizeAxes = Axes.X,
+                            AutoSizeAxes = Axes.Y
+                        }
+                    }
+                });
+
+                ReplacePlaceholder();
+            }
+
+            protected override void Update()
+            {
+                base.Update();
+
+                // AutoSizeAxes cannot be used as the height should represent the post-layout-transform height at all times, so that the placeholder doesn't bounce around.
+                content.Height = ((Flow)Child).Children.Sum(c => c.DrawHeight + 5);
+            }
+
+            /// <summary>
+            /// Replaces the current <see cref="PlaceholderItem"/> with a new one, and returns the previous.
+            /// </summary>
+            /// <returns>The current <see cref="PlaceholderItem"/>.</returns>
+            public DrawableCollectionListItem ReplacePlaceholder()
+            {
+                var previous = PlaceholderItem;
+
+                placeholderContainer.Clear(false);
+                placeholderContainer.Add(PlaceholderItem = new DrawableCollectionListItem(new BeatmapCollection(), false));
+
+                return previous;
+            }
+        }
+
+        /// <summary>
+        /// The flow of <see cref="DrawableCollectionListItem"/>. Disables layout easing unless a drag is in progress.
+        /// </summary>
+        private class Flow : FillFlowContainer<RearrangeableListItem<BeatmapCollection>>
+        {
+            public readonly IBindable<bool> DragActive = new Bindable<bool>();
+
+            public Flow()
+            {
+                Spacing = new Vector2(0, 5);
+                LayoutEasing = Easing.OutQuint;
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+                DragActive.BindValueChanged(active => LayoutDuration = active.NewValue ? 200 : 0);
+            }
+        }
+    }
+}

osu.Game/Collections/DrawableCollectionListItem.cs

@@ -0,0 +1,237 @@
+// 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.Bindables;
+using osu.Framework.Extensions.Color4Extensions;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Input.Events;
+using osu.Game.Graphics;
+using osu.Game.Graphics.Containers;
+using osu.Game.Graphics.UserInterface;
+using osu.Game.Overlays;
+using osuTK;
+using osuTK.Graphics;
+
+namespace osu.Game.Collections
+{
+    /// <summary>
+    /// Visualises a <see cref="BeatmapCollection"/> inside a <see cref="DrawableCollectionList"/>.
+    /// </summary>
+    public class DrawableCollectionListItem : OsuRearrangeableListItem<BeatmapCollection>
+    {
+        private const float item_height = 35;
+        private const float button_width = item_height * 0.75f;
+
+        /// <summary>
+        /// Whether the <see cref="BeatmapCollection"/> currently exists inside the <see cref="CollectionManager"/>.
+        /// </summary>
+        public IBindable<bool> IsCreated => isCreated;
+
+        private readonly Bindable<bool> isCreated = new Bindable<bool>();
+
+        /// <summary>
+        /// Creates a new <see cref="DrawableCollectionListItem"/>.
+        /// </summary>
+        /// <param name="item">The <see cref="BeatmapCollection"/>.</param>
+        /// <param name="isCreated">Whether <paramref name="item"/> currently exists inside the <see cref="CollectionManager"/>.</param>
+        public DrawableCollectionListItem(BeatmapCollection item, bool isCreated)
+            : base(item)
+        {
+            this.isCreated.Value = isCreated;
+
+            ShowDragHandle.BindTo(this.isCreated);
+        }
+
+        protected override Drawable CreateContent() => new ItemContent(Model)
+        {
+            IsCreated = { BindTarget = isCreated }
+        };
+
+        /// <summary>
+        /// The main content of the <see cref="DrawableCollectionListItem"/>.
+        /// </summary>
+        private class ItemContent : CircularContainer
+        {
+            public readonly Bindable<bool> IsCreated = new Bindable<bool>();
+
+            private readonly IBindable<string> collectionName;
+            private readonly BeatmapCollection collection;
+
+            [Resolved(CanBeNull = true)]
+            private CollectionManager collectionManager { get; set; }
+
+            private Container textBoxPaddingContainer;
+            private ItemTextBox textBox;
+
+            public ItemContent(BeatmapCollection collection)
+            {
+                this.collection = collection;
+
+                RelativeSizeAxes = Axes.X;
+                Height = item_height;
+                Masking = true;
+
+                collectionName = collection.Name.GetBoundCopy();
+            }
+
+            [BackgroundDependencyLoader]
+            private void load(OsuColour colours)
+            {
+                Children = new Drawable[]
+                {
+                    new DeleteButton(collection)
+                    {
+                        Anchor = Anchor.CentreRight,
+                        Origin = Anchor.CentreRight,
+                        IsCreated = { BindTarget = IsCreated },
+                        IsTextBoxHovered = v => textBox.ReceivePositionalInputAt(v)
+                    },
+                    textBoxPaddingContainer = new Container
+                    {
+                        RelativeSizeAxes = Axes.Both,
+                        Padding = new MarginPadding { Right = button_width },
+                        Children = new Drawable[]
+                        {
+                            textBox = new ItemTextBox
+                            {
+                                RelativeSizeAxes = Axes.Both,
+                                Size = Vector2.One,
+                                CornerRadius = item_height / 2,
+                                Current = collection.Name,
+                                PlaceholderText = IsCreated.Value ? string.Empty : "Create a new collection"
+                            },
+                        }
+                    },
+                };
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                collectionName.BindValueChanged(_ => createNewCollection(), true);
+                IsCreated.BindValueChanged(created => textBoxPaddingContainer.Padding = new MarginPadding { Right = created.NewValue ? button_width : 0 }, true);
+            }
+
+            private void createNewCollection()
+            {
+                if (IsCreated.Value)
+                    return;
+
+                if (string.IsNullOrEmpty(collectionName.Value))
+                    return;
+
+                // Add the new collection and disable our placeholder. If all text is removed, the placeholder should not show back again.
+                collectionManager?.Collections.Add(collection);
+                textBox.PlaceholderText = string.Empty;
+
+                // When this item changes from placeholder to non-placeholder (via changing containers), its textbox will lose focus, so it needs to be re-focused.
+                Schedule(() => GetContainingInputManager().ChangeFocus(textBox));
+
+                IsCreated.Value = true;
+            }
+        }
+
+        private class ItemTextBox : OsuTextBox
+        {
+            protected override float LeftRightPadding => item_height / 2;
+
+            [BackgroundDependencyLoader]
+            private void load(OsuColour colours)
+            {
+                BackgroundUnfocused = colours.GreySeafoamDarker.Darken(0.5f);
+                BackgroundFocused = colours.GreySeafoam;
+            }
+        }
+
+        public class DeleteButton : CompositeDrawable
+        {
+            public readonly IBindable<bool> IsCreated = new Bindable<bool>();
+
+            public Func<Vector2, bool> IsTextBoxHovered;
+
+            [Resolved(CanBeNull = true)]
+            private DialogOverlay dialogOverlay { get; set; }
+
+            [Resolved(CanBeNull = true)]
+            private CollectionManager collectionManager { get; set; }
+
+            private readonly BeatmapCollection collection;
+
+            private Drawable fadeContainer;
+            private Drawable background;
+
+            public DeleteButton(BeatmapCollection collection)
+            {
+                this.collection = collection;
+                RelativeSizeAxes = Axes.Y;
+
+                Width = button_width + item_height / 2; // add corner radius to cover with fill
+            }
+
+            [BackgroundDependencyLoader]
+            private void load(OsuColour colours)
+            {
+                InternalChild = fadeContainer = new Container
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    Alpha = 0.1f,
+                    Children = new[]
+                    {
+                        background = new Box
+                        {
+                            RelativeSizeAxes = Axes.Both,
+                            Colour = colours.Red
+                        },
+                        new SpriteIcon
+                        {
+                            Anchor = Anchor.CentreRight,
+                            Origin = Anchor.Centre,
+                            X = -button_width * 0.6f,
+                            Size = new Vector2(10),
+                            Icon = FontAwesome.Solid.Trash
+                        }
+                    }
+                };
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+                IsCreated.BindValueChanged(created => Alpha = created.NewValue ? 1 : 0, true);
+            }
+
+            public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => base.ReceivePositionalInputAt(screenSpacePos) && !IsTextBoxHovered(screenSpacePos);
+
+            protected override bool OnHover(HoverEvent e)
+            {
+                fadeContainer.FadeTo(1f, 100, Easing.Out);
+                return false;
+            }
+
+            protected override void OnHoverLost(HoverLostEvent e)
+            {
+                fadeContainer.FadeTo(0.1f, 100);
+            }
+
+            protected override bool OnClick(ClickEvent e)
+            {
+                background.FlashColour(Color4.White, 150);
+
+                if (collection.Beatmaps.Count == 0)
+                    deleteCollection();
+                else
+                    dialogOverlay?.Push(new DeleteCollectionDialog(collection, deleteCollection));
+
+                return true;
+            }
+
+            private void deleteCollection() => collectionManager?.Collections.Remove(collection);
+        }
+    }
+}

osu.Game/Collections/ManageCollectionsDialog.cs

@@ -0,0 +1,134 @@
+// 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.Shapes;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Graphics;
+using osu.Game.Graphics.Containers;
+using osu.Game.Graphics.Sprites;
+using osu.Game.Graphics.UserInterface;
+using osuTK;
+
+namespace osu.Game.Collections
+{
+    public class ManageCollectionsDialog : OsuFocusedOverlayContainer
+    {
+        private const double enter_duration = 500;
+        private const double exit_duration = 200;
+
+        [Resolved(CanBeNull = true)]
+        private CollectionManager collectionManager { get; set; }
+
+        public ManageCollectionsDialog()
+        {
+            Anchor = Anchor.Centre;
+            Origin = Anchor.Centre;
+
+            RelativeSizeAxes = Axes.Both;
+            Size = new Vector2(0.5f, 0.8f);
+
+            Masking = true;
+            CornerRadius = 10;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(OsuColour colours)
+        {
+            Children = new Drawable[]
+            {
+                new Box
+                {
+                    Colour = colours.GreySeafoamDark,
+                    RelativeSizeAxes = Axes.Both,
+                },
+                new Container
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    Child = new GridContainer
+                    {
+                        RelativeSizeAxes = Axes.Both,
+                        RowDimensions = new[]
+                        {
+                            new Dimension(GridSizeMode.AutoSize),
+                        },
+                        Content = new[]
+                        {
+                            new Drawable[]
+                            {
+                                new Container
+                                {
+                                    RelativeSizeAxes = Axes.X,
+                                    AutoSizeAxes = Axes.Y,
+                                    Children = new Drawable[]
+                                    {
+                                        new OsuSpriteText
+                                        {
+                                            Anchor = Anchor.Centre,
+                                            Origin = Anchor.Centre,
+                                            Text = "Manage collections",
+                                            Font = OsuFont.GetFont(size: 30),
+                                            Padding = new MarginPadding { Vertical = 10 },
+                                        },
+                                        new IconButton
+                                        {
+                                            Anchor = Anchor.CentreRight,
+                                            Origin = Anchor.CentreRight,
+                                            Icon = FontAwesome.Solid.Times,
+                                            Colour = colours.GreySeafoamDarker,
+                                            Scale = new Vector2(0.8f),
+                                            X = -10,
+                                            Action = () => State.Value = Visibility.Hidden
+                                        }
+                                    }
+                                }
+                            },
+                            new Drawable[]
+                            {
+                                new Container
+                                {
+                                    RelativeSizeAxes = Axes.Both,
+                                    Children = new Drawable[]
+                                    {
+                                        new Box
+                                        {
+                                            RelativeSizeAxes = Axes.Both,
+                                            Colour = colours.GreySeafoamDarker
+                                        },
+                                        new DrawableCollectionList
+                                        {
+                                            RelativeSizeAxes = Axes.Both,
+                                            Items = { BindTarget = collectionManager?.Collections ?? new BindableList<BeatmapCollection>() }
+                                        }
+                                    }
+                                }
+                            },
+                        }
+                    }
+                }
+            };
+        }
+
+        protected override void PopIn()
+        {
+            base.PopIn();
+
+            this.FadeIn(enter_duration, Easing.OutQuint);
+            this.ScaleTo(0.9f).Then().ScaleTo(1f, enter_duration, Easing.OutQuint);
+        }
+
+        protected override void PopOut()
+        {
+            base.PopOut();
+
+            this.FadeOut(exit_duration, Easing.OutQuint);
+            this.ScaleTo(0.9f, exit_duration);
+
+            // Ensure that textboxes commit
+            GetContainingInputManager()?.TriggerFocusContention(this);
+        }
+    }
+}

osu.Game/Graphics/Containers/OsuRearrangeableListContainer.cs

@@ -12,13 +12,13 @@ namespace osu.Game.Graphics.Containers
         /// <summary>
         /// Whether any item is currently being dragged. Used to hide other items' drag handles.
         /// </summary>
-        private readonly BindableBool playlistDragActive = new BindableBool();
+        protected readonly BindableBool DragActive = new BindableBool();
 
         protected override ScrollContainer<Drawable> CreateScrollContainer() => new OsuScrollContainer();
 
         protected sealed override RearrangeableListItem<TModel> CreateDrawable(TModel item) => CreateOsuDrawable(item).With(d =>
         {
-            d.PlaylistDragActive.BindTo(playlistDragActive);
+            d.DragActive.BindTo(DragActive);
         });
 
         protected abstract OsuRearrangeableListItem<TModel> CreateOsuDrawable(TModel item);

osu.Game/Graphics/Containers/OsuRearrangeableListItem.cs

@@ -19,7 +19,7 @@ namespace osu.Game.Graphics.Containers
         /// <summary>
         /// Whether any item is currently being dragged. Used to hide other items' drag handles.
         /// </summary>
-        public readonly BindableBool PlaylistDragActive = new BindableBool();
+        public readonly BindableBool DragActive = new BindableBool();
 
         private Color4 handleColour = Color4.White;
 
@@ -44,8 +44,9 @@ namespace osu.Game.Graphics.Containers
         /// <summary>
         /// Whether the drag handle should be shown.
         /// </summary>
-        protected virtual bool ShowDragHandle => true;
+        protected readonly Bindable<bool> ShowDragHandle = new Bindable<bool>();
 
+        private Container handleContainer;
         private PlaylistItemHandle handle;
 
         protected OsuRearrangeableListItem(TModel item)
@@ -58,8 +59,6 @@ namespace osu.Game.Graphics.Containers
         [BackgroundDependencyLoader]
         private void load()
         {
-            Container handleContainer;
-
             InternalChild = new GridContainer
             {
                 RelativeSizeAxes = Axes.X,
@@ -88,9 +87,12 @@ namespace osu.Game.Graphics.Containers
                 ColumnDimensions = new[] { new Dimension(GridSizeMode.AutoSize) },
                 RowDimensions = new[] { new Dimension(GridSizeMode.AutoSize) }
             };
+        }
 
-            if (!ShowDragHandle)
+        protected override void LoadComplete()
-                handleContainer.Alpha = 0;
+        {
+            base.LoadComplete();
+            ShowDragHandle.BindValueChanged(show => handleContainer.Alpha = show.NewValue ? 1 : 0, true);
         }
 
         protected override bool OnDragStart(DragStartEvent e)
@@ -98,13 +100,13 @@ namespace osu.Game.Graphics.Containers
             if (!base.OnDragStart(e))
                 return false;
 
-            PlaylistDragActive.Value = true;
+            DragActive.Value = true;
             return true;
         }
 
         protected override void OnDragEnd(DragEndEvent e)
         {
-            PlaylistDragActive.Value = false;
+            DragActive.Value = false;
             base.OnDragEnd(e);
         }
 
@@ -112,7 +114,7 @@ namespace osu.Game.Graphics.Containers
 
         protected override bool OnHover(HoverEvent e)
         {
-            handle.UpdateHoverState(IsDragged || !PlaylistDragActive.Value);
+            handle.UpdateHoverState(IsDragged || !DragActive.Value);
             return base.OnHover(e);
         }
 

osu.Game/Graphics/UserInterface/IconButton.cs

@@ -24,7 +24,7 @@ namespace osu.Game.Graphics.UserInterface
             set
             {
                 iconColour = value;
-                icon.Colour = value;
+                icon.FadeColour(value);
             }
         }
 

osu.Game/Graphics/UserInterface/OsuContextMenu.cs

@@ -26,6 +26,8 @@ namespace osu.Game.Graphics.UserInterface
             };
 
             ItemsContainer.Padding = new MarginPadding { Vertical = DrawableOsuMenuItem.MARGIN_VERTICAL };
+
+            MaxHeight = 250;
         }
 
         [BackgroundDependencyLoader]

osu.Game/OsuGame.cs

@@ -31,6 +31,7 @@ using osu.Framework.Input.Events;
 using osu.Framework.Platform;
 using osu.Framework.Threading;
 using osu.Game.Beatmaps;
+using osu.Game.Collections;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
@@ -610,12 +611,19 @@ namespace osu.Game
                 d.Origin = Anchor.TopRight;
             }), rightFloatingOverlayContent.Add, true);
 
+            loadComponentSingleFile(new CollectionManager(Storage)
+            {
+                PostNotification = n => notifications.Post(n),
+                GetStableStorage = GetStorageForStableInstall
+            }, Add, true);
+
             loadComponentSingleFile(screenshotManager, Add);
 
             // dependency on notification overlay, dependent by settings overlay
             loadComponentSingleFile(CreateUpdateManager(), Add, true);
 
             // overlay elements
+            loadComponentSingleFile(new ManageCollectionsDialog(), overlayContent.Add, true);
             loadComponentSingleFile(beatmapListing = new BeatmapListingOverlay(), overlayContent.Add, true);
             loadComponentSingleFile(dashboard = new DashboardOverlay(), overlayContent.Add, true);
             loadComponentSingleFile(news = new NewsOverlay(), overlayContent.Add, true);

osu.Game/Overlays/Settings/Sections/Maintenance/GeneralSettings.cs

@@ -3,9 +3,11 @@
 
 using System.Linq;
 using System.Threading.Tasks;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Game.Beatmaps;
+using osu.Game.Collections;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Scoring;
 using osu.Game.Skinning;
@@ -19,14 +21,15 @@ namespace osu.Game.Overlays.Settings.Sections.Maintenance
         private TriangleButton importBeatmapsButton;
         private TriangleButton importScoresButton;
         private TriangleButton importSkinsButton;
+        private TriangleButton importCollectionsButton;
         private TriangleButton deleteBeatmapsButton;
         private TriangleButton deleteScoresButton;
         private TriangleButton deleteSkinsButton;
         private TriangleButton restoreButton;
         private TriangleButton undeleteButton;
 
-        [BackgroundDependencyLoader]
+        [BackgroundDependencyLoader(permitNulls: true)]
-        private void load(BeatmapManager beatmaps, ScoreManager scores, SkinManager skins, DialogOverlay dialogOverlay)
+        private void load(BeatmapManager beatmaps, ScoreManager scores, SkinManager skins, [CanBeNull] CollectionManager collectionManager, DialogOverlay dialogOverlay)
         {
             if (beatmaps.SupportsImportFromStable)
             {
@@ -93,20 +96,46 @@ namespace osu.Game.Overlays.Settings.Sections.Maintenance
                 });
             }
 
-            AddRange(new Drawable[]
+            Add(deleteSkinsButton = new DangerousSettingsButton
             {
-                deleteSkinsButton = new DangerousSettingsButton
+                Text = "Delete ALL skins",
+                Action = () =>
                 {
-                    Text = "Delete ALL skins",
+                    dialogOverlay?.Push(new DeleteAllBeatmapsDialog(() =>
+                    {
+                        deleteSkinsButton.Enabled.Value = false;
+                        Task.Run(() => skins.Delete(skins.GetAllUserSkins())).ContinueWith(t => Schedule(() => deleteSkinsButton.Enabled.Value = true));
+                    }));
+                }
+            });
+
+            if (collectionManager != null)
+            {
+                if (collectionManager.SupportsImportFromStable)
+                {
+                    Add(importCollectionsButton = new SettingsButton
+                    {
+                        Text = "Import collections from stable",
+                        Action = () =>
+                        {
+                            importCollectionsButton.Enabled.Value = false;
+                            collectionManager.ImportFromStableAsync().ContinueWith(t => Schedule(() => importCollectionsButton.Enabled.Value = true));
+                        }
+                    });
+                }
+
+                Add(new DangerousSettingsButton
+                {
+                    Text = "Delete ALL collections",
                     Action = () =>
                     {
-                        dialogOverlay?.Push(new DeleteAllBeatmapsDialog(() =>
+                        dialogOverlay?.Push(new DeleteAllBeatmapsDialog(collectionManager.DeleteAll));
-                        {
-                            deleteSkinsButton.Enabled.Value = false;
-                            Task.Run(() => skins.Delete(skins.GetAllUserSkins())).ContinueWith(t => Schedule(() => deleteSkinsButton.Enabled.Value = true));
-                        }));
                     }
-                },
+                });
+            }
+
+            AddRange(new Drawable[]
+            {
                 restoreButton = new SettingsButton
                 {
                     Text = "Restore all hidden difficulties",

osu.Game/Screens/Multi/DrawableRoomPlaylistItem.cs

@@ -37,8 +37,6 @@ namespace osu.Game.Screens.Multi
 
         public readonly Bindable<PlaylistItem> SelectedItem = new Bindable<PlaylistItem>();
 
-        protected override bool ShowDragHandle => allowEdit;
-
         private Container maskingContainer;
         private Container difficultyIconContainer;
         private LinkFlowContainer beatmapText;
@@ -63,12 +61,13 @@ namespace osu.Game.Screens.Multi
 
             // TODO: edit support should be moved out into a derived class
             this.allowEdit = allowEdit;
-
             this.allowSelection = allowSelection;
 
             beatmap.BindTo(item.Beatmap);
             ruleset.BindTo(item.Ruleset);
             requiredMods.BindTo(item.RequiredMods);
+
+            ShowDragHandle.Value = allowEdit;
         }
 
         [BackgroundDependencyLoader]

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

@@ -60,6 +60,9 @@ namespace osu.Game.Screens.Select.Carousel
                     match &= terms.Any(term => term.IndexOf(criteriaTerm, StringComparison.InvariantCultureIgnoreCase) >= 0);
             }
 
+            if (match)
+                match &= criteria.Collection?.Beatmaps.Contains(Beatmap) ?? true;
+
             Filtered.Value = !match;
         }
 

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
@@ -17,6 +18,7 @@ using osu.Framework.Graphics.UserInterface;
 using osu.Framework.Input.Events;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.Drawables;
+using osu.Game.Collections;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Backgrounds;
 using osu.Game.Graphics.Sprites;
@@ -46,6 +48,12 @@ namespace osu.Game.Screens.Select.Carousel
         [Resolved]
         private BeatmapDifficultyManager difficultyManager { get; set; }
 
+        [Resolved(CanBeNull = true)]
+        private CollectionManager collectionManager { get; set; }
+
+        [Resolved(CanBeNull = true)]
+        private ManageCollectionsDialog manageCollectionsDialog { get; set; }
+
         private IBindable<StarDifficulty> starDifficultyBindable;
         private CancellationTokenSource starDifficultyCancellationSource;
 
@@ -213,16 +221,39 @@ namespace osu.Game.Screens.Select.Carousel
                 if (editRequested != null)
                     items.Add(new OsuMenuItem("Edit", MenuItemType.Standard, () => editRequested(beatmap)));
 
+                if (beatmap.OnlineBeatmapID.HasValue && beatmapOverlay != null)
+                    items.Add(new OsuMenuItem("Details...", MenuItemType.Standard, () => beatmapOverlay.FetchAndShowBeatmap(beatmap.OnlineBeatmapID.Value)));
+
+                if (collectionManager != null)
+                {
+                    var collectionItems = collectionManager.Collections.Select(createCollectionMenuItem).ToList();
+                    if (manageCollectionsDialog != null)
+                        collectionItems.Add(new OsuMenuItem("Manage...", MenuItemType.Standard, manageCollectionsDialog.Show));
+
+                    items.Add(new OsuMenuItem("Collections") { Items = collectionItems });
+                }
+
                 if (hideRequested != null)
                     items.Add(new OsuMenuItem("Hide", MenuItemType.Destructive, () => hideRequested(beatmap)));
 
-                if (beatmap.OnlineBeatmapID.HasValue && beatmapOverlay != null)
-                    items.Add(new OsuMenuItem("Details", MenuItemType.Standard, () => beatmapOverlay.FetchAndShowBeatmap(beatmap.OnlineBeatmapID.Value)));
-
                 return items.ToArray();
             }
         }
 
+        private MenuItem createCollectionMenuItem(BeatmapCollection collection)
+        {
+            return new ToggleMenuItem(collection.Name.Value, MenuItemType.Standard, s =>
+            {
+                if (s)
+                    collection.Beatmaps.Add(beatmap);
+                else
+                    collection.Beatmaps.Remove(beatmap);
+            })
+            {
+                State = { Value = collection.Beatmaps.Contains(beatmap) }
+            };
+        }
+
         protected override void Dispose(bool isDisposing)
         {
             base.Dispose(isDisposing);

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

@@ -16,6 +16,7 @@ using osu.Framework.Input.Events;
 using osu.Framework.Localisation;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.Drawables;
+using osu.Game.Collections;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Sprites;
 using osu.Game.Graphics.UserInterface;
@@ -34,6 +35,12 @@ namespace osu.Game.Screens.Select.Carousel
         [Resolved(CanBeNull = true)]
         private DialogOverlay dialogOverlay { get; set; }
 
+        [Resolved(CanBeNull = true)]
+        private CollectionManager collectionManager { get; set; }
+
+        [Resolved(CanBeNull = true)]
+        private ManageCollectionsDialog manageCollectionsDialog { get; set; }
+
         private readonly BeatmapSetInfo beatmapSet;
 
         public DrawableCarouselBeatmapSet(CarouselBeatmapSet set)
@@ -135,16 +142,61 @@ namespace osu.Game.Screens.Select.Carousel
                 if (beatmapSet.OnlineBeatmapSetID != null && viewDetails != null)
                     items.Add(new OsuMenuItem("Details...", MenuItemType.Standard, () => viewDetails(beatmapSet.OnlineBeatmapSetID.Value)));
 
+                if (collectionManager != null)
+                {
+                    var collectionItems = collectionManager.Collections.Select(createCollectionMenuItem).ToList();
+                    if (manageCollectionsDialog != null)
+                        collectionItems.Add(new OsuMenuItem("Manage...", MenuItemType.Standard, manageCollectionsDialog.Show));
+
+                    items.Add(new OsuMenuItem("Collections") { Items = collectionItems });
+                }
+
                 if (beatmapSet.Beatmaps.Any(b => b.Hidden))
                     items.Add(new OsuMenuItem("Restore all hidden", MenuItemType.Standard, () => restoreHiddenRequested(beatmapSet)));
 
                 if (dialogOverlay != null)
-                    items.Add(new OsuMenuItem("Delete", MenuItemType.Destructive, () => dialogOverlay.Push(new BeatmapDeleteDialog(beatmapSet))));
+                    items.Add(new OsuMenuItem("Delete...", MenuItemType.Destructive, () => dialogOverlay.Push(new BeatmapDeleteDialog(beatmapSet))));
-
                 return items.ToArray();
             }
         }
 
+        private MenuItem createCollectionMenuItem(BeatmapCollection collection)
+        {
+            TernaryState state;
+
+            var countExisting = beatmapSet.Beatmaps.Count(b => collection.Beatmaps.Contains(b));
+
+            if (countExisting == beatmapSet.Beatmaps.Count)
+                state = TernaryState.True;
+            else if (countExisting > 0)
+                state = TernaryState.Indeterminate;
+            else
+                state = TernaryState.False;
+
+            return new TernaryStateMenuItem(collection.Name.Value, MenuItemType.Standard, s =>
+            {
+                foreach (var b in beatmapSet.Beatmaps)
+                {
+                    switch (s)
+                    {
+                        case TernaryState.True:
+                            if (collection.Beatmaps.Contains(b))
+                                continue;
+
+                            collection.Beatmaps.Add(b);
+                            break;
+
+                        case TernaryState.False:
+                            collection.Beatmaps.Remove(b);
+                            break;
+                    }
+                }
+            })
+            {
+                State = { Value = state }
+            };
+        }
+
         private class PanelBackground : BufferedContainer
         {
             public PanelBackground(WorkingBeatmap working)

osu.Game/Screens/Select/CollectionFilterDropdown.cs

@@ -0,0 +1,273 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Specialized;
+using System.Diagnostics;
+using System.Linq;
+using JetBrains.Annotations;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Sprites;
+using osu.Framework.Graphics.UserInterface;
+using osu.Framework.Input.Events;
+using osu.Game.Beatmaps;
+using osu.Game.Collections;
+using osu.Game.Graphics;
+using osu.Game.Graphics.Containers;
+using osu.Game.Graphics.UserInterface;
+using osuTK;
+
+namespace osu.Game.Screens.Select
+{
+    /// <summary>
+    /// A dropdown to select the <see cref="CollectionMenuItem"/> to filter beatmaps using.
+    /// </summary>
+    public class CollectionFilterDropdown : OsuDropdown<CollectionMenuItem>
+    {
+        private readonly IBindableList<BeatmapCollection> collections = new BindableList<BeatmapCollection>();
+        private readonly IBindableList<BeatmapInfo> beatmaps = new BindableList<BeatmapInfo>();
+        private readonly BindableList<CollectionMenuItem> filters = new BindableList<CollectionMenuItem>();
+
+        [Resolved(CanBeNull = true)]
+        private ManageCollectionsDialog manageCollectionsDialog { get; set; }
+
+        public CollectionFilterDropdown()
+        {
+            ItemSource = filters;
+        }
+
+        [BackgroundDependencyLoader(permitNulls: true)]
+        private void load([CanBeNull] CollectionManager collectionManager)
+        {
+            if (collectionManager != null)
+                collections.BindTo(collectionManager.Collections);
+
+            collections.CollectionChanged += (_, __) => collectionsChanged();
+            collectionsChanged();
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            Current.BindValueChanged(filterChanged, true);
+        }
+
+        /// <summary>
+        /// Occurs when a collection has been added or removed.
+        /// </summary>
+        private void collectionsChanged()
+        {
+            var selectedItem = SelectedItem?.Value?.Collection;
+
+            filters.Clear();
+            filters.Add(new AllBeatmapsCollectionMenuItem());
+            filters.AddRange(collections.Select(c => new CollectionMenuItem(c)));
+            filters.Add(new ManageCollectionsMenuItem());
+
+            Current.Value = filters.SingleOrDefault(f => f.Collection != null && f.Collection == selectedItem) ?? filters[0];
+        }
+
+        /// <summary>
+        /// Occurs when the <see cref="CollectionMenuItem"/> selection has changed.
+        /// </summary>
+        private void filterChanged(ValueChangedEvent<CollectionMenuItem> filter)
+        {
+            // Binding the beatmaps will trigger a collection change event, which results in an infinite-loop. This is rebound later, when it's safe to do so.
+            beatmaps.CollectionChanged -= filterBeatmapsChanged;
+
+            if (filter.OldValue?.Collection != null)
+                beatmaps.UnbindFrom(filter.OldValue.Collection.Beatmaps);
+
+            if (filter.NewValue?.Collection != null)
+                beatmaps.BindTo(filter.NewValue.Collection.Beatmaps);
+
+            beatmaps.CollectionChanged += filterBeatmapsChanged;
+
+            // Never select the manage collection filter - rollback to the previous filter.
+            // This is done after the above since it is important that bindable is unbound from OldValue, which is lost after forcing it back to the old value.
+            if (filter.NewValue is ManageCollectionsMenuItem)
+            {
+                Current.Value = filter.OldValue;
+                manageCollectionsDialog?.Show();
+            }
+        }
+
+        /// <summary>
+        /// Occurs when the beatmaps contained by a <see cref="BeatmapCollection"/> have changed.
+        /// </summary>
+        private void filterBeatmapsChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            // The filtered beatmaps have changed, without the filter having changed itself. So a change in filter must be notified.
+            // Note that this does NOT propagate to bound bindables, so the FilterControl must bind directly to the value change event of this bindable.
+            Current.TriggerChange();
+        }
+
+        protected override string GenerateItemText(CollectionMenuItem item) => item.CollectionName.Value;
+
+        protected override DropdownHeader CreateHeader() => new CollectionDropdownHeader
+        {
+            SelectedItem = { BindTarget = Current }
+        };
+
+        protected override DropdownMenu CreateMenu() => new CollectionDropdownMenu();
+
+        public class CollectionDropdownHeader : OsuDropdownHeader
+        {
+            public readonly Bindable<CollectionMenuItem> SelectedItem = new Bindable<CollectionMenuItem>();
+            private readonly Bindable<string> collectionName = new Bindable<string>();
+
+            protected override string Label
+            {
+                get => base.Label;
+                set { } // See updateText().
+            }
+
+            public CollectionDropdownHeader()
+            {
+                Height = 25;
+                Icon.Size = new Vector2(16);
+                Foreground.Padding = new MarginPadding { Top = 4, Bottom = 4, Left = 8, Right = 4 };
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                SelectedItem.BindValueChanged(_ => updateBindable(), true);
+            }
+
+            private void updateBindable()
+            {
+                collectionName.UnbindAll();
+
+                if (SelectedItem.Value != null)
+                    collectionName.BindTo(SelectedItem.Value.CollectionName);
+
+                collectionName.BindValueChanged(_ => updateText(), true);
+            }
+
+            // Dropdowns don't bind to value changes, so the real name is copied directly from the selected item here.
+            private void updateText() => base.Label = collectionName.Value;
+        }
+
+        private class CollectionDropdownMenu : OsuDropdownMenu
+        {
+            public CollectionDropdownMenu()
+            {
+                MaxHeight = 200;
+            }
+
+            protected override DrawableDropdownMenuItem CreateDrawableDropdownMenuItem(MenuItem item) => new CollectionDropdownMenuItem(item);
+        }
+
+        private class CollectionDropdownMenuItem : OsuDropdownMenu.DrawableOsuDropdownMenuItem
+        {
+            [NotNull]
+            protected new CollectionMenuItem Item => ((DropdownMenuItem<CollectionMenuItem>)base.Item).Value;
+
+            [Resolved]
+            private OsuColour colours { get; set; }
+
+            [Resolved]
+            private IBindable<WorkingBeatmap> beatmap { get; set; }
+
+            [CanBeNull]
+            private readonly BindableList<BeatmapInfo> collectionBeatmaps;
+
+            [NotNull]
+            private readonly Bindable<string> collectionName;
+
+            private IconButton addOrRemoveButton;
+            private Content content;
+            private bool beatmapInCollection;
+
+            public CollectionDropdownMenuItem(MenuItem item)
+                : base(item)
+            {
+                collectionBeatmaps = Item.Collection?.Beatmaps.GetBoundCopy();
+                collectionName = Item.CollectionName.GetBoundCopy();
+            }
+
+            [BackgroundDependencyLoader]
+            private void load()
+            {
+                AddInternal(addOrRemoveButton = new IconButton
+                {
+                    Anchor = Anchor.CentreRight,
+                    Origin = Anchor.CentreRight,
+                    X = -OsuScrollContainer.SCROLL_BAR_HEIGHT,
+                    Scale = new Vector2(0.65f),
+                    Action = addOrRemove,
+                });
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                if (collectionBeatmaps != null)
+                {
+                    collectionBeatmaps.CollectionChanged += (_, __) => collectionChanged();
+                    beatmap.BindValueChanged(_ => collectionChanged(), true);
+                }
+
+                // Although the DrawableMenuItem binds to value changes of the item's text, the item is an internal implementation detail of Dropdown that has no knowledge
+                // of the underlying CollectionFilter value and its accompanying name, so the real name has to be copied here. Without this, the collection name wouldn't update when changed.
+                collectionName.BindValueChanged(name => content.Text = name.NewValue, true);
+
+                updateButtonVisibility();
+            }
+
+            protected override bool OnHover(HoverEvent e)
+            {
+                updateButtonVisibility();
+                return base.OnHover(e);
+            }
+
+            protected override void OnHoverLost(HoverLostEvent e)
+            {
+                updateButtonVisibility();
+                base.OnHoverLost(e);
+            }
+
+            private void collectionChanged()
+            {
+                Debug.Assert(collectionBeatmaps != null);
+
+                beatmapInCollection = collectionBeatmaps.Contains(beatmap.Value.BeatmapInfo);
+
+                addOrRemoveButton.Enabled.Value = !beatmap.IsDefault;
+                addOrRemoveButton.Icon = beatmapInCollection ? FontAwesome.Solid.MinusSquare : FontAwesome.Solid.PlusSquare;
+                addOrRemoveButton.TooltipText = beatmapInCollection ? "Remove selected beatmap" : "Add selected beatmap";
+
+                updateButtonVisibility();
+            }
+
+            protected override void OnSelectChange()
+            {
+                base.OnSelectChange();
+                updateButtonVisibility();
+            }
+
+            private void updateButtonVisibility()
+            {
+                if (collectionBeatmaps == null)
+                    addOrRemoveButton.Alpha = 0;
+                else
+                    addOrRemoveButton.Alpha = IsHovered || IsPreSelected || beatmapInCollection ? 1 : 0;
+            }
+
+            private void addOrRemove()
+            {
+                Debug.Assert(collectionBeatmaps != null);
+
+                if (!collectionBeatmaps.Remove(beatmap.Value.BeatmapInfo))
+                    collectionBeatmaps.Add(beatmap.Value.BeatmapInfo);
+            }
+
+            protected override Drawable CreateContent() => content = (Content)base.CreateContent();
+        }
+    }
+}

osu.Game/Screens/Select/CollectionMenuItem.cs

@@ -0,0 +1,55 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using JetBrains.Annotations;
+using osu.Framework.Bindables;
+using osu.Game.Collections;
+
+namespace osu.Game.Screens.Select
+{
+    /// <summary>
+    /// A <see cref="BeatmapCollection"/> filter.
+    /// </summary>
+    public class CollectionMenuItem
+    {
+        /// <summary>
+        /// The collection to filter beatmaps from.
+        /// May be null to not filter by collection (include all beatmaps).
+        /// </summary>
+        [CanBeNull]
+        public readonly BeatmapCollection Collection;
+
+        /// <summary>
+        /// The name of the collection.
+        /// </summary>
+        [NotNull]
+        public readonly Bindable<string> CollectionName;
+
+        /// <summary>
+        /// Creates a new <see cref="CollectionMenuItem"/>.
+        /// </summary>
+        /// <param name="collection">The collection to filter beatmaps from.</param>
+        public CollectionMenuItem([CanBeNull] BeatmapCollection collection)
+        {
+            Collection = collection;
+            CollectionName = Collection?.Name.GetBoundCopy() ?? new Bindable<string>("All beatmaps");
+        }
+    }
+
+    public class AllBeatmapsCollectionMenuItem : CollectionMenuItem
+    {
+        public AllBeatmapsCollectionMenuItem()
+            : base(null)
+        {
+        }
+    }
+
+    public class ManageCollectionsMenuItem : CollectionMenuItem
+    {
+        public ManageCollectionsMenuItem()
+            : base(null)
+        {
+            CollectionName.Value = "Manage collections...";
+        }
+    }
+}

osu.Game/Screens/Select/FilterControl.cs

@@ -21,7 +21,8 @@ namespace osu.Game.Screens.Select
 {
     public class FilterControl : Container
     {
-        public const float HEIGHT = 100;
+        public const float HEIGHT = 2 * side_margin + 85;
+        private const float side_margin = 20;
 
         public Action<FilterCriteria> FilterChanged;
 
@@ -41,6 +42,7 @@ namespace osu.Game.Screens.Select
                 Sort = sortMode.Value,
                 AllowConvertedBeatmaps = showConverted.Value,
                 Ruleset = ruleset.Value,
+                Collection = collectionDropdown?.Current.Value.Collection
             };
 
             if (!minimumStars.IsDefault)
@@ -54,6 +56,7 @@ namespace osu.Game.Screens.Select
         }
 
         private SeekLimitedSearchTextBox searchTextBox;
+        private CollectionFilterDropdown collectionDropdown;
 
         public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) =>
             base.ReceivePositionalInputAt(screenSpacePos) || sortTabs.ReceivePositionalInputAt(screenSpacePos);
@@ -90,65 +93,104 @@ namespace osu.Game.Screens.Select
                 },
                 new Container
                 {
-                    Padding = new MarginPadding(20),
+                    Padding = new MarginPadding(side_margin),
                     RelativeSizeAxes = Axes.Both,
                     Width = 0.5f,
                     Anchor = Anchor.TopRight,
                     Origin = Anchor.TopRight,
-                    Children = new Drawable[]
+                    Child = new GridContainer
                     {
-                        searchTextBox = new SeekLimitedSearchTextBox { RelativeSizeAxes = Axes.X },
+                        RelativeSizeAxes = Axes.Both,
-                        new Box
+                        RowDimensions = new[]
                         {
-                            RelativeSizeAxes = Axes.X,
+                            new Dimension(GridSizeMode.Absolute, 60),
-                            Height = 1,
+                            new Dimension(GridSizeMode.Absolute, 5),
-                            Colour = OsuColour.Gray(80),
+                            new Dimension(GridSizeMode.Absolute, 20),
-                            Origin = Anchor.BottomLeft,
-                            Anchor = Anchor.BottomLeft,
                         },
-                        new FillFlowContainer
+                        Content = new[]
                         {
-                            Anchor = Anchor.BottomRight,
+                            new Drawable[]
-                            Origin = Anchor.BottomRight,
-                            Direction = FillDirection.Horizontal,
-                            RelativeSizeAxes = Axes.X,
-                            AutoSizeAxes = Axes.Y,
-                            Spacing = new Vector2(OsuTabControl<SortMode>.HORIZONTAL_SPACING, 0),
-                            Children = new Drawable[]
                             {
-                                new OsuTabControlCheckbox
+                                new Container
                                 {
-                                    Text = "Show converted",
+                                    RelativeSizeAxes = Axes.Both,
-                                    Current = config.GetBindable<bool>(OsuSetting.ShowConvertedBeatmaps),
+                                    Children = new Drawable[]
-                                    Anchor = Anchor.BottomRight,
+                                    {
-                                    Origin = Anchor.BottomRight,
+                                        searchTextBox = new SeekLimitedSearchTextBox { RelativeSizeAxes = Axes.X },
-                                },
+                                        new Box
-                                sortTabs = new OsuTabControl<SortMode>
+                                        {
+                                            RelativeSizeAxes = Axes.X,
+                                            Height = 1,
+                                            Colour = OsuColour.Gray(80),
+                                            Origin = Anchor.BottomLeft,
+                                            Anchor = Anchor.BottomLeft,
+                                        },
+                                        new FillFlowContainer
+                                        {
+                                            Anchor = Anchor.BottomRight,
+                                            Origin = Anchor.BottomRight,
+                                            Direction = FillDirection.Horizontal,
+                                            RelativeSizeAxes = Axes.X,
+                                            AutoSizeAxes = Axes.Y,
+                                            Spacing = new Vector2(OsuTabControl<SortMode>.HORIZONTAL_SPACING, 0),
+                                            Children = new Drawable[]
+                                            {
+                                                new OsuTabControlCheckbox
+                                                {
+                                                    Text = "Show converted",
+                                                    Current = config.GetBindable<bool>(OsuSetting.ShowConvertedBeatmaps),
+                                                    Anchor = Anchor.BottomRight,
+                                                    Origin = Anchor.BottomRight,
+                                                },
+                                                sortTabs = new OsuTabControl<SortMode>
+                                                {
+                                                    RelativeSizeAxes = Axes.X,
+                                                    Width = 0.5f,
+                                                    Height = 24,
+                                                    AutoSort = true,
+                                                    Anchor = Anchor.BottomRight,
+                                                    Origin = Anchor.BottomRight,
+                                                    AccentColour = colours.GreenLight,
+                                                    Current = { BindTarget = sortMode }
+                                                },
+                                                new OsuSpriteText
+                                                {
+                                                    Text = "Sort by",
+                                                    Font = OsuFont.GetFont(size: 14),
+                                                    Margin = new MarginPadding(5),
+                                                    Anchor = Anchor.BottomRight,
+                                                    Origin = Anchor.BottomRight,
+                                                },
+                                            }
+                                        },
+                                    }
+                                }
+                            },
+                            null,
+                            new Drawable[]
+                            {
+                                new Container
                                 {
-                                    RelativeSizeAxes = Axes.X,
+                                    RelativeSizeAxes = Axes.Both,
-                                    Width = 0.5f,
+                                    Children = new Drawable[]
-                                    Height = 24,
+                                    {
-                                    AutoSort = true,
+                                        collectionDropdown = new CollectionFilterDropdown
-                                    Anchor = Anchor.BottomRight,
+                                        {
-                                    Origin = Anchor.BottomRight,
+                                            Anchor = Anchor.TopRight,
-                                    AccentColour = colours.GreenLight,
+                                            Origin = Anchor.TopRight,
-                                    Current = { BindTarget = sortMode }
+                                            RelativeSizeAxes = Axes.X,
-                                },
+                                            Width = 0.4f,
-                                new OsuSpriteText
+                                        }
-                                {
+                                    }
-                                    Text = "Sort by",
+                                }
-                                    Font = OsuFont.GetFont(size: 14),
+                            },
-                                    Margin = new MarginPadding(5),
+                        }
-                                    Anchor = Anchor.BottomRight,
-                                    Origin = Anchor.BottomRight,
-                                },
-                            }
-                        },
                     }
                 }
             };
 
-            searchTextBox.Current.ValueChanged += _ => FilterChanged?.Invoke(CreateCriteria());
+            collectionDropdown.Current.ValueChanged += _ => updateCriteria();
+            searchTextBox.Current.ValueChanged += _ => updateCriteria();
 
             updateCriteria();
         }
@@ -156,7 +198,6 @@ namespace osu.Game.Screens.Select
         public void Deactivate()
         {
             searchTextBox.ReadOnly = true;
-
             searchTextBox.HoldFocus = false;
             if (searchTextBox.HasFocus)
                 GetContainingInputManager().ChangeFocus(searchTextBox);

osu.Game/Screens/Select/FilterCriteria.cs

@@ -4,7 +4,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using JetBrains.Annotations;
 using osu.Game.Beatmaps;
+using osu.Game.Collections;
 using osu.Game.Rulesets;
 using osu.Game.Screens.Select.Filter;
 
@@ -51,6 +53,12 @@ namespace osu.Game.Screens.Select
             }
         }
 
+        /// <summary>
+        /// The collection to filter beatmaps from.
+        /// </summary>
+        [CanBeNull]
+        public BeatmapCollection Collection;
+
         public struct OptionalRange<T> : IEquatable<OptionalRange<T>>
             where T : struct
         {