Merge pull request #504 from peppy/song-select-loading-reoptimisation

Song select performance / code cleanup.

osu.Game/Beatmaps/Drawables/BeatmapGroup.cs

@@ -10,7 +10,7 @@ using osu.Game.Database;
 
 namespace osu.Game.Beatmaps.Drawables
 {
-    internal class BeatmapGroup : IStateful<BeatmapGroupState>
+    public class BeatmapGroup : IStateful<BeatmapGroupState>
     {
         public BeatmapPanel SelectedPanel;
 
@@ -63,8 +63,6 @@ namespace osu.Game.Beatmaps.Drawables
         {
             BeatmapSet = beatmapSet;
             WorkingBeatmap beatmap = database.GetWorkingBeatmap(BeatmapSet.Beatmaps.FirstOrDefault());
-            foreach (var b in BeatmapSet.Beatmaps)
-                b.StarDifficulty = (float)(database.GetWorkingBeatmap(b).Beatmap?.CalculateStarDifficulty() ?? -1f);
 
             Header = new BeatmapSetHeader(beatmap)
             {

osu.Game/Beatmaps/Drawables/BeatmapPanel.cs

@@ -18,7 +18,7 @@ using osu.Game.Graphics.Sprites;
 
 namespace osu.Game.Beatmaps.Drawables
 {
-    internal class BeatmapPanel : Panel
+    public class BeatmapPanel : Panel
     {
         public BeatmapInfo Beatmap;
         private Sprite background;
@@ -59,6 +59,8 @@ namespace osu.Game.Beatmaps.Drawables
 
         protected override void ApplyState(PanelSelectedState last = PanelSelectedState.Hidden)
         {
+            if (!IsLoaded) return;
+
             base.ApplyState(last);
 
             if (last == PanelSelectedState.Hidden && State != last)
@@ -138,7 +140,7 @@ namespace osu.Game.Beatmaps.Drawables
                                 },
                                 starCounter = new StarCounter
                                 {
-                                    Count = beatmap.StarDifficulty,
+                                    Count = (float)beatmap.StarDifficulty,
                                     Scale = new Vector2(0.8f),
                                 }
                             }

osu.Game/Beatmaps/Drawables/BeatmapSetHeader.cs

@@ -17,7 +17,7 @@ using OpenTK.Graphics;
 
 namespace osu.Game.Beatmaps.Drawables
 {
-    internal class BeatmapSetHeader : Panel
+    public class BeatmapSetHeader : Panel
     {
         public Action<BeatmapSetHeader> GainedSelection;
         private SpriteText title, artist;
@@ -32,10 +32,6 @@ namespace osu.Game.Beatmaps.Drawables
 
             Children = new Drawable[]
             {
-                new PanelBackground(beatmap)
-                {
-                    RelativeSizeAxes = Axes.Both,
-                },
                 new FillFlowContainer
                 {
                     Direction = FillDirection.Vertical,
@@ -74,13 +70,23 @@ namespace osu.Game.Beatmaps.Drawables
         }
 
         [BackgroundDependencyLoader]
-        private void load(OsuConfigManager config)
+        private void load(OsuConfigManager config, OsuGameBase game)
         {
             this.config = config;
 
             preferUnicode = config.GetBindable<bool>(OsuConfig.ShowUnicode);
             preferUnicode.ValueChanged += preferUnicode_changed;
             preferUnicode_changed(preferUnicode, null);
+
+            new PanelBackground(beatmap)
+            {
+                RelativeSizeAxes = Axes.Both,
+                Depth = 1,
+            }.LoadAsync(game, b =>
+            {
+                Add(b);
+                b.FadeInFromZero(200);
+            });
         }
 
         private void preferUnicode_changed(object sender, EventArgs e)
@@ -98,16 +104,18 @@ namespace osu.Game.Beatmaps.Drawables
 
         private class PanelBackground : BufferedContainer
         {
-            private readonly WorkingBeatmap working;
-
             public PanelBackground(WorkingBeatmap working)
             {
-                this.working = working;
-
                 CacheDrawnFrameBuffer = true;
 
-                Children = new[]
+                Children = new Drawable[]
                 {
+                    new BeatmapBackgroundSprite(working)
+                    {
+                        Anchor = Anchor.Centre,
+                        Origin = Anchor.Centre,
+                        FillMode = FillMode.Fill,
+                    },
                     new FillFlowContainer
                     {
                         Depth = -1,
@@ -151,21 +159,6 @@ namespace osu.Game.Beatmaps.Drawables
                     },
                 };
             }
-
-            [BackgroundDependencyLoader]
-            private void load(OsuGameBase game)
-            {
-                new BeatmapBackgroundSprite(working)
-                {
-                    Anchor = Anchor.Centre,
-                    Origin = Anchor.Centre,
-                    FillMode = FillMode.Fill,
-                }.LoadAsync(game, bg =>
-                {
-                    Add(bg);
-                    ForceRedraw();
-                });
-            }
         }
 
         public void AddDifficultyIcons(IEnumerable<BeatmapPanel> panels)

osu.Game/Beatmaps/Drawables/Panel.cs

@@ -12,7 +12,7 @@ using osu.Framework.Extensions.Color4Extensions;
 
 namespace osu.Game.Beatmaps.Drawables
 {
-    internal class Panel : Container, IStateful<PanelSelectedState>
+    public class Panel : Container, IStateful<PanelSelectedState>
     {
         public const float MAX_HEIGHT = 80;
 
@@ -51,6 +51,8 @@ namespace osu.Game.Beatmaps.Drawables
 
         protected virtual void ApplyState(PanelSelectedState last = PanelSelectedState.Hidden)
         {
+            if (!IsLoaded) return;
+
             switch (state)
             {
                 case PanelSelectedState.Hidden:
@@ -115,7 +117,7 @@ namespace osu.Game.Beatmaps.Drawables
         }
     }
 
-    internal enum PanelSelectedState
+    public enum PanelSelectedState
     {
         Hidden,
         NotSelected,

osu.Game/Database/BeatmapDatabase.cs

@@ -123,16 +123,15 @@ namespace osu.Game.Database
         /// <param name="paths">Multiple locations on disk</param>
         public void Import(IEnumerable<string> paths)
         {
-            Stack<BeatmapSetInfo> sets = new Stack<BeatmapSetInfo>();
-
             foreach (string p in paths)
+            {
                 try
                 {
                     BeatmapSetInfo set = getBeatmapSet(p);
 
                     //If we have an ID then we already exist in the database.
                     if (set.ID == 0)
-                        sets.Push(set);
+                        Import(new[] { set });
 
                     // We may or may not want to delete the file depending on where it is stored.
                     //  e.g. reconstructing/repairing database with beatmaps from default storage.
@@ -152,9 +151,7 @@ namespace osu.Game.Database
                     e = e.InnerException ?? e;
                     Logger.Error(e, @"Could not import beatmap set");
                 }
-
-            // Batch commit with multiple sets to database
-            Import(sets);
+            }
         }
 
         /// <summary>
@@ -236,6 +233,8 @@ namespace osu.Game.Database
                         // TODO: Diff beatmap metadata with set metadata and leave it here if necessary
                         beatmap.BeatmapInfo.Metadata = null;
 
+                        beatmap.BeatmapInfo.StarDifficulty = beatmap.CalculateStarDifficulty();
+
                         beatmapSet.Beatmaps.Add(beatmap.BeatmapInfo);
                     }
                 beatmapSet.StoryboardFile = archive.StoryboardFilename;

osu.Game/Database/BeatmapInfo.cs

@@ -75,16 +75,7 @@ namespace osu.Game.Database
         // Metadata
         public string Version { get; set; }
 
-        private float starDifficulty = -1;
-        public float StarDifficulty
-        {
-            get
-            {
-                return starDifficulty < 0 ? (Difficulty?.OverallDifficulty ?? 5) : starDifficulty;
-            }
-
-            set { starDifficulty = value; }
-        }
+        public double StarDifficulty { get; set; }
 
         public bool Equals(BeatmapInfo other)
         {

osu.Game/Database/BeatmapSetInfo.cs

@@ -24,7 +24,7 @@ namespace osu.Game.Database
         [OneToMany(CascadeOperations = CascadeOperation.All)]
         public List<BeatmapInfo> Beatmaps { get; set; }
 
-        public float MaxStarDifficulty => Beatmaps.Max(b => b.StarDifficulty);
+        public double MaxStarDifficulty => Beatmaps.Max(b => b.StarDifficulty);
 
         public bool DeletePending { get; set; }
 

osu.Game/Screens/Menu/MainMenu.cs

@@ -27,6 +27,7 @@ namespace osu.Game.Screens.Menu
         internal override bool ShowOverlays => buttons.State != MenuState.Initial;
 
         private BackgroundScreen background;
+        private Screen songSelect;
 
         protected override BackgroundScreen CreateBackground() => background;
 
@@ -46,7 +47,7 @@ namespace osu.Game.Screens.Menu
                             OnChart = delegate { Push(new ChartListing()); },
                             OnDirect = delegate { Push(new OnlineListing()); },
                             OnEdit = delegate { Push(new Editor()); },
-                            OnSolo = delegate { Push(new PlaySongSelect()); },
+                            OnSolo = delegate { Push(consumeSongSelect()); },
                             OnMulti = delegate { Push(new Lobby()); },
                             OnTest  = delegate { Push(new TestBrowser()); },
                             OnExit = delegate { Exit(); },
@@ -62,6 +63,24 @@ namespace osu.Game.Screens.Menu
             background.LoadAsync(game);
 
             buttons.OnSettings = game.ToggleOptions;
+
+            preloadSongSelect();
+        }
+
+        private void preloadSongSelect()
+        {
+            if (songSelect == null)
+            {
+                songSelect = new PlaySongSelect();
+                songSelect.LoadAsync(Game);
+            }
+        }
+
+        private Screen consumeSongSelect()
+        {
+            var s = songSelect;
+            songSelect = null;
+            return s;
         }
 
         protected override void OnEntering(Screen last)
@@ -86,6 +105,9 @@ namespace osu.Game.Screens.Menu
         {
             base.OnResuming(last);
 
+            //we may have consumed our preloaded instance, so let's make another.
+            preloadSongSelect();
+
             const float length = 300;
 
             buttons.State = MenuState.TopLevel;

osu.Game/Screens/Select/BeatmapCarousel.cs

@@ -15,47 +15,234 @@ using OpenTK.Input;
 using System.Collections;
 using osu.Framework.MathUtils;
 using System.Diagnostics;
-using osu.Game.Screens.Select.Filter;
+using System.Threading.Tasks;
+using osu.Framework.Allocation;
+using osu.Framework.Threading;
 
 namespace osu.Game.Screens.Select
 {
-    internal class CarouselContainer : ScrollContainer, IEnumerable<BeatmapGroup>
+    internal class BeatmapCarousel : ScrollContainer, IEnumerable<BeatmapGroup>
     {
-        private Container<Panel> scrollableContent;
-        private List<BeatmapGroup> groups = new List<BeatmapGroup>();
-        private List<Panel> panels = new List<Panel>();
+        public BeatmapInfo SelectedBeatmap => selectedPanel?.Beatmap;
 
-        public BeatmapGroup SelectedGroup { get; private set; }
-        public BeatmapPanel SelectedPanel { get; private set; }
+        public Action BeatmapsChanged;
+
+        public IEnumerable<BeatmapSetInfo> Beatmaps
+        {
+            get
+            {
+                return groups.Select(g => g.BeatmapSet);
+            }
+
+            set
+            {
+                scrollableContent.Clear(false);
+                panels.Clear();
+                groups.Clear();
+
+                List<BeatmapGroup> newGroups = null;
+
+                Task.Run(() =>
+                {
+                    newGroups = value.Select(createGroup).ToList();
+                    criteria.Filter(newGroups);
+                }).ContinueWith(t =>
+                {
+                    Schedule(() =>
+                    {
+                        foreach (var g in newGroups)
+                            addGroup(g);
+
+                        computeYPositions();
+                        BeatmapsChanged?.Invoke();
+                    });
+                });
+            }
+        }
 
         private List<float> yPositions = new List<float>();
 
-        public CarouselContainer()
-        {
-            DistanceDecayJump = 0.01;
+        /// <summary>
+        /// Required for now unfortunately.
+        /// </summary>
+        private BeatmapDatabase database;
 
+        private Container<Panel> scrollableContent;
+
+        private List<BeatmapGroup> groups = new List<BeatmapGroup>();
+
+        private List<Panel> panels = new List<Panel>();
+
+        private BeatmapGroup selectedGroup;
+
+        private BeatmapPanel selectedPanel;
+
+        public BeatmapCarousel()
+        {
             Add(scrollableContent = new Container<Panel>
             {
                 RelativeSizeAxes = Axes.X,
             });
         }
 
-        public void AddGroup(BeatmapGroup group)
+        public void AddBeatmap(BeatmapSetInfo beatmapSet)
         {
-            groups.Add(group);
+            var group = createGroup(beatmapSet);
 
-            panels.Add(group.Header);
-            group.Header.UpdateClock(Clock);
-            foreach (BeatmapPanel panel in group.BeatmapPanels)
+            //for the time being, let's completely load the difficulty panels in the background.
+            //this likely won't scale so well, but allows us to completely async the loading flow.
+            Schedule(delegate
             {
-                panels.Add(panel);
-                panel.UpdateClock(Clock);
-            }
-
-            computeYPositions();
+                addGroup(group);
+                computeYPositions();
+                if (selectedGroup == null)
+                    selectGroup(group);
+            });
         }
 
-        public void RemoveGroup(BeatmapGroup group)
+        public void SelectBeatmap(BeatmapInfo beatmap, bool animated = true)
+        {
+            if (beatmap == null)
+            {
+                SelectNext();
+                return;
+            }
+
+            foreach (BeatmapGroup group in groups)
+            {
+                var panel = group.BeatmapPanels.FirstOrDefault(p => p.Beatmap.Equals(beatmap));
+                if (panel != null)
+                {
+                    selectGroup(group, panel, animated);
+                    return;
+                }
+            }
+        }
+
+        public void RemoveBeatmap(BeatmapSetInfo info) => removeGroup(groups.Find(b => b.BeatmapSet.ID == info.ID));
+
+        public Action<BeatmapGroup, BeatmapInfo> SelectionChanged;
+
+        public Action StartRequested;
+
+        public void SelectNext(int direction = 1, bool skipDifficulties = true)
+        {
+            if (groups.Count == 0)
+            {
+                selectedGroup = null;
+                selectedPanel = null;
+                return;
+            }
+
+            if (!skipDifficulties && selectedGroup != null)
+            {
+                int i = selectedGroup.BeatmapPanels.IndexOf(selectedPanel) + direction;
+
+                if (i >= 0 && i < selectedGroup.BeatmapPanels.Count)
+                {
+                    //changing difficulty panel, not set.
+                    selectGroup(selectedGroup, selectedGroup.BeatmapPanels[i]);
+                    return;
+                }
+            }
+
+            int startIndex = groups.IndexOf(selectedGroup);
+            int index = startIndex;
+
+            do
+            {
+                index = (index + direction + groups.Count) % groups.Count;
+                if (groups[index].State != BeatmapGroupState.Hidden)
+                {
+                    SelectBeatmap(groups[index].BeatmapPanels.First().Beatmap);
+                    return;
+                }
+            } while (index != startIndex);
+        }
+
+        public void SelectRandom()
+        {
+            List<BeatmapGroup> visibleGroups = groups.Where(selectGroup => selectGroup.State != BeatmapGroupState.Hidden).ToList();
+            if (visibleGroups.Count < 1)
+                return;
+            BeatmapGroup group = visibleGroups[RNG.Next(visibleGroups.Count)];
+            BeatmapPanel panel = group?.BeatmapPanels.First();
+
+            if (panel == null)
+                return;
+
+            selectGroup(group, panel);
+        }
+
+        private FilterCriteria criteria = new FilterCriteria();
+
+        private ScheduledDelegate filterTask;
+
+        public void Filter(FilterCriteria newCriteria = null, bool debounce = true)
+        {
+            if (!IsLoaded) return;
+
+            criteria = newCriteria ?? criteria ?? new FilterCriteria();
+
+            Action perform = delegate
+            {
+                filterTask = null;
+
+                criteria.Filter(groups);
+
+                var filtered = new List<BeatmapGroup>(groups);
+
+                scrollableContent.Clear(false);
+                panels.Clear();
+                groups.Clear();
+
+                foreach (var g in filtered)
+                    addGroup(g);
+
+                computeYPositions();
+
+                if (selectedGroup == null || selectedGroup.State == BeatmapGroupState.Hidden)
+                    SelectNext();
+            };
+
+            filterTask?.Cancel();
+            if (debounce)
+                filterTask = Scheduler.AddDelayed(perform, 250);
+            else
+                perform();
+        }
+
+        public IEnumerator<BeatmapGroup> GetEnumerator() => groups.GetEnumerator();
+
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+        private BeatmapGroup createGroup(BeatmapSetInfo beatmapSet)
+        {
+            database.GetChildren(beatmapSet);
+            beatmapSet.Beatmaps.ForEach(b => { if (b.Metadata == null) b.Metadata = beatmapSet.Metadata; });
+
+            return new BeatmapGroup(beatmapSet, database)
+            {
+                SelectionChanged = SelectionChanged,
+                StartRequested = b => StartRequested?.Invoke(),
+                State = BeatmapGroupState.Collapsed
+            };
+        }
+
+        [BackgroundDependencyLoader(permitNulls: true)]
+        private void load(BeatmapDatabase database)
+        {
+            this.database = database;
+        }
+
+        private void addGroup(BeatmapGroup group)
+        {
+            groups.Add(group);
+            panels.Add(group.Header);
+            panels.AddRange(group.BeatmapPanels);
+        }
+
+        private void removeGroup(BeatmapGroup group)
         {
             groups.Remove(group);
             panels.Remove(group.Header);
@@ -65,18 +252,12 @@ namespace osu.Game.Screens.Select
             scrollableContent.Remove(group.Header);
             scrollableContent.Remove(group.BeatmapPanels);
 
+            if (selectedGroup == group)
+                SelectNext();
+
             computeYPositions();
         }
 
-        private void movePanel(Panel panel, bool advance, bool animated, ref float currentY)
-        {
-            yPositions.Add(currentY);
-            panel.MoveToY(currentY, animated ? 750 : 0, EasingTypes.OutExpo);
-
-            if (advance)
-                currentY += panel.DrawHeight + 5;
-        }
-
         /// <summary>
         /// Computes the target Y positions for every panel in the carousel.
         /// </summary>
@@ -99,7 +280,7 @@ namespace osu.Game.Screens.Select
 
                     foreach (BeatmapPanel panel in group.BeatmapPanels)
                     {
-                        if (panel == SelectedPanel)
+                        if (panel == selectedPanel)
                             selectedY = currentY + panel.DrawHeight / 2 - DrawHeight / 2;
 
                         panel.MoveToX(-50, 500, EasingTypes.OutExpo);
@@ -129,105 +310,62 @@ namespace osu.Game.Screens.Select
             return selectedY;
         }
 
-        public void SelectBeatmap(BeatmapInfo beatmap, bool animated = true)
+        private void movePanel(Panel panel, bool advance, bool animated, ref float currentY)
         {
-            foreach (BeatmapGroup group in groups)
-            {
-                var panel = group.BeatmapPanels.FirstOrDefault(p => p.Beatmap.Equals(beatmap));
-                if (panel != null)
-                {
-                    selectGroup(group, panel, animated);
-                    return;
-                }
-            }
+            yPositions.Add(currentY);
+            panel.MoveToY(currentY, animated ? 750 : 0, EasingTypes.OutExpo);
+
+            if (advance)
+                currentY += panel.DrawHeight + 5;
         }
 
-        private void selectGroup(BeatmapGroup group, BeatmapPanel panel, bool animated = true)
+        private void selectGroup(BeatmapGroup group, BeatmapPanel panel = null, bool animated = true)
         {
+            if (panel == null)
+                panel = group.BeatmapPanels.First();
+
             Trace.Assert(group.BeatmapPanels.Contains(panel), @"Selected panel must be in provided group");
 
-            if (SelectedGroup != null && SelectedGroup != group && SelectedGroup.State != BeatmapGroupState.Hidden)
-                SelectedGroup.State = BeatmapGroupState.Collapsed;
+            if (selectedGroup != null && selectedGroup != group && selectedGroup.State != BeatmapGroupState.Hidden)
+                selectedGroup.State = BeatmapGroupState.Collapsed;
 
             group.State = BeatmapGroupState.Expanded;
-            SelectedGroup = group;
+            selectedGroup = group;
             panel.State = PanelSelectedState.Selected;
-            SelectedPanel = panel;
+            selectedPanel = panel;
 
             float selectedY = computeYPositions(animated);
             ScrollTo(selectedY, animated);
         }
 
-        public void Sort(SortMode mode)
+        protected override bool OnKeyDown(InputState state, KeyDownEventArgs args)
         {
-            List<BeatmapGroup> sortedGroups = new List<BeatmapGroup>(groups);
-            switch (mode)
+            int direction = 0;
+            bool skipDifficulties = false;
+
+            switch (args.Key)
             {
-                case SortMode.Artist:
-                    sortedGroups.Sort((x, y) => string.Compare(x.BeatmapSet.Metadata.Artist, y.BeatmapSet.Metadata.Artist, StringComparison.InvariantCultureIgnoreCase));
+                case Key.Up:
+                    direction = -1;
                     break;
-                case SortMode.Title:
-                    sortedGroups.Sort((x, y) => string.Compare(x.BeatmapSet.Metadata.Title, y.BeatmapSet.Metadata.Title, StringComparison.InvariantCultureIgnoreCase));
+                case Key.Down:
+                    direction = 1;
                     break;
-                case SortMode.Author:
-                    sortedGroups.Sort((x, y) => string.Compare(x.BeatmapSet.Metadata.Author, y.BeatmapSet.Metadata.Author, StringComparison.InvariantCultureIgnoreCase));
+                case Key.Left:
+                    direction = -1;
+                    skipDifficulties = true;
                     break;
-                case SortMode.Difficulty:
-                    sortedGroups.Sort((x, y) => x.BeatmapSet.MaxStarDifficulty.CompareTo(y.BeatmapSet.MaxStarDifficulty));
-                    break;
-                default:
-                    Sort(SortMode.Artist); // Temporary
+                case Key.Right:
+                    direction = 1;
+                    skipDifficulties = true;
                     break;
             }
 
-            scrollableContent.Clear(false);
-            panels.Clear();
-            groups.Clear();
+            if (direction == 0)
+                return base.OnKeyDown(state, args);
 
-            foreach (BeatmapGroup group in sortedGroups)
-                AddGroup(group);
-        }
-
-        /// <summary>
-        /// Computes the x-offset of currently visible panels. Makes the carousel appear round.
-        /// </summary>
-        /// <param name="dist">
-        /// Vertical distance from the center of the carousel container
-        /// ranging from -1 to 1.
-        /// </param>
-        /// <param name="halfHeight">Half the height of the carousel container.</param>
-        private static float offsetX(float dist, float halfHeight)
-        {
-            // The radius of the circle the carousel moves on.
-            const float circle_radius = 3;
-            double discriminant = Math.Max(0, circle_radius * circle_radius - dist * dist);
-            float x = (circle_radius - (float)Math.Sqrt(discriminant)) * halfHeight;
-
-            return 125 + x;
-        }
-
-        /// <summary>
-        /// Update a panel's x position and multiplicative alpha based on its y position and
-        /// the current scroll position.
-        /// </summary>
-        /// <param name="p">The panel to be updated.</param>
-        /// <param name="halfHeight">Half the draw height of the carousel container.</param>
-        private void updatePanel(Panel p, float halfHeight)
-        {
-            var height = p.IsPresent ? p.DrawHeight : 0;
-
-            float panelDrawY = p.Position.Y - Current + height / 2;
-            float dist = Math.Abs(1f - panelDrawY / halfHeight);
-
-            // Setting the origin position serves as an additive position on top of potential
-            // local transformation we may want to apply (e.g. when a panel gets selected, we
-            // may want to smoothly transform it leftwards.)
-            p.OriginPosition = new Vector2(-offsetX(dist, halfHeight), 0);
-
-            // We are applying a multiplicative alpha (which is internally done by nesting an
-            // additional container and setting that container's alpha) such that we can
-            // layer transformations on top, with a similar reasoning to the previous comment.
-            p.SetMultiplicativeAlpha(MathHelper.Clamp(1.75f - 1.5f * dist, 0, 1));
+            SelectNext(direction, skipDifficulties);
+            return true;
         }
 
         protected override void Update()
@@ -276,80 +414,46 @@ namespace osu.Game.Screens.Select
                 updatePanel(p, halfHeight);
         }
 
-        protected override bool OnKeyDown(InputState state, KeyDownEventArgs args)
+        /// <summary>
+        /// Computes the x-offset of currently visible panels. Makes the carousel appear round.
+        /// </summary>
+        /// <param name="dist">
+        /// Vertical distance from the center of the carousel container
+        /// ranging from -1 to 1.
+        /// </param>
+        /// <param name="halfHeight">Half the height of the carousel container.</param>
+        private static float offsetX(float dist, float halfHeight)
         {
-            int direction = 0;
-            bool skipDifficulties = false;
+            // The radius of the circle the carousel moves on.
+            const float circle_radius = 3;
+            double discriminant = Math.Max(0, circle_radius * circle_radius - dist * dist);
+            float x = (circle_radius - (float)Math.Sqrt(discriminant)) * halfHeight;
 
-            switch (args.Key)
-            {
-                case Key.Up:
-                    direction = -1;
-                    break;
-                case Key.Down:
-                    direction = 1;
-                    break;
-                case Key.Left:
-                    direction = -1;
-                    skipDifficulties = true;
-                    break;
-                case Key.Right:
-                    direction = 1;
-                    skipDifficulties = true;
-                    break;
-            }
-
-            if (direction == 0)
-                return base.OnKeyDown(state, args);
-
-            SelectNext(direction, skipDifficulties);
-            return true;
+            return 125 + x;
         }
 
-        public void SelectNext(int direction = 1, bool skipDifficulties = true)
+        /// <summary>
+        /// Update a panel's x position and multiplicative alpha based on its y position and
+        /// the current scroll position.
+        /// </summary>
+        /// <param name="p">The panel to be updated.</param>
+        /// <param name="halfHeight">Half the draw height of the carousel container.</param>
+        private void updatePanel(Panel p, float halfHeight)
         {
-            if (!skipDifficulties && SelectedGroup != null)
-            {
-                int i = SelectedGroup.BeatmapPanels.IndexOf(SelectedPanel) + direction;
+            var height = p.IsPresent ? p.DrawHeight : 0;
 
-                if (i >= 0 && i < SelectedGroup.BeatmapPanels.Count)
-                {
-                    //changing difficulty panel, not set.
-                    selectGroup(SelectedGroup, SelectedGroup.BeatmapPanels[i]);
-                    return;
-                }
-            }
+            float panelDrawY = p.Position.Y - Current + height / 2;
+            float dist = Math.Abs(1f - panelDrawY / halfHeight);
 
-            int startIndex = groups.IndexOf(SelectedGroup);
-            int index = startIndex;
+            // Setting the origin position serves as an additive position on top of potential
+            // local transformation we may want to apply (e.g. when a panel gets selected, we
+            // may want to smoothly transform it leftwards.)
+            p.OriginPosition = new Vector2(-offsetX(dist, halfHeight), 0);
 
-            do
-            {
-                index = (index + direction + groups.Count) % groups.Count;
-                if (groups[index].State != BeatmapGroupState.Hidden)
-                {
-                    SelectBeatmap(groups[index].BeatmapPanels.First().Beatmap);
-                    return;
-                }
-            } while (index != startIndex);
+            // We are applying a multiplicative alpha (which is internally done by nesting an
+            // additional container and setting that container's alpha) such that we can
+            // layer transformations on top, with a similar reasoning to the previous comment.
+            p.SetMultiplicativeAlpha(MathHelper.Clamp(1.75f - 1.5f * dist, 0, 1));
         }
-
-        public void SelectRandom()
-        {
-            List<BeatmapGroup> visibleGroups = groups.Where(selectGroup => selectGroup.State != BeatmapGroupState.Hidden).ToList();
-            if (visibleGroups.Count < 1)
-                return;
-            BeatmapGroup group = visibleGroups[RNG.Next(visibleGroups.Count)];
-            BeatmapPanel panel = group?.BeatmapPanels.First();
-
-            if (panel == null)
-                return;
-
-            selectGroup(group, panel);
-        }
-
-        public IEnumerator<BeatmapGroup> GetEnumerator() => groups.GetEnumerator();
-
-        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
     }
 }

osu.Game/Screens/Select/FilterControl.cs

@@ -5,6 +5,7 @@ using System;
 using OpenTK;
 using OpenTK.Graphics;
 using osu.Framework.Allocation;
+using osu.Framework.Configuration;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Primitives;
@@ -15,14 +16,13 @@ using osu.Game.Graphics.UserInterface;
 using osu.Game.Screens.Select.Filter;
 using Container = osu.Framework.Graphics.Containers.Container;
 using osu.Framework.Input;
+using osu.Game.Modes;
 
 namespace osu.Game.Screens.Select
 {
     public class FilterControl : Container
     {
-        public Action FilterChanged;
-
-        public string Search => searchTextBox.Text;
+        public Action<FilterCriteria> FilterChanged;
 
         private OsuTabControl<SortMode> sortTabs;
 
@@ -30,16 +30,16 @@ namespace osu.Game.Screens.Select
 
         private SortMode sort = SortMode.Title;
         public SortMode Sort
-        { 
-            get { return sort; } 
+        {
+            get { return sort; }
             set
             {
                 if (sort != value)
                 {
                     sort = value;
-                    FilterChanged?.Invoke();
+                    FilterChanged?.Invoke(CreateCriteria());
                 }
-            } 
+            }
         }
 
         private GroupMode group = GroupMode.All;
@@ -51,11 +51,19 @@ namespace osu.Game.Screens.Select
                 if (group != value)
                 {
                     group = value;
-                    FilterChanged?.Invoke();
+                    FilterChanged?.Invoke(CreateCriteria());
                 }
             }
         }
 
+        public FilterCriteria CreateCriteria() => new FilterCriteria
+        {
+            Group = group,
+            Sort = sort,
+            SearchText = searchTextBox.Text,
+            Mode = playMode
+        };
+
         public Action Exit;
 
         private SearchTextBox searchTextBox;
@@ -88,7 +96,7 @@ namespace osu.Game.Screens.Select
                             OnChange = (sender, newText) =>
                             {
                                 if (newText)
-                                    FilterChanged?.Invoke();
+                                    FilterChanged?.Invoke(CreateCriteria());
                             },
                             Exit = () => Exit?.Invoke(),
                         },
@@ -152,16 +160,21 @@ namespace osu.Game.Screens.Select
             searchTextBox.HoldFocus = false;
             searchTextBox.TriggerFocusLost();
         }
-        
+
         public void Activate()
         {
             searchTextBox.HoldFocus = true;
         }
 
-        [BackgroundDependencyLoader]
-        private void load(OsuColour colours)
+        private readonly Bindable<PlayMode> playMode = new Bindable<PlayMode>();
+
+        [BackgroundDependencyLoader(permitNulls:true)]
+        private void load(OsuColour colours, OsuGame osu)
         {
             sortTabs.AccentColour = colours.GreenLight;
+
+            if (osu != null)
+                playMode.BindTo(osu.PlayMode);
         }
 
         protected override bool OnMouseDown(InputState state, MouseDownEventArgs args) => true;

osu.Game/Screens/Select/FilterCriteria.cs

@@ -0,0 +1,65 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using osu.Game.Beatmaps.Drawables;
+using osu.Game.Modes;
+using osu.Game.Screens.Select.Filter;
+
+namespace osu.Game.Screens.Select
+{
+    public class FilterCriteria
+    {
+        public GroupMode Group;
+        public SortMode Sort;
+        public string SearchText;
+        public PlayMode Mode;
+
+        public void Filter(List<BeatmapGroup> groups)
+        {
+            foreach (var g in groups)
+            {
+                var set = g.BeatmapSet;
+
+                bool hasCurrentMode = set.Beatmaps.Any(bm => bm.Mode == Mode);
+
+                bool match = hasCurrentMode;
+
+                match &= string.IsNullOrEmpty(SearchText)
+                    || (set.Metadata.Artist ?? string.Empty).IndexOf(SearchText, StringComparison.InvariantCultureIgnoreCase) != -1
+                    || (set.Metadata.ArtistUnicode ?? string.Empty).IndexOf(SearchText, StringComparison.InvariantCultureIgnoreCase) != -1
+                    || (set.Metadata.Title ?? string.Empty).IndexOf(SearchText, StringComparison.InvariantCultureIgnoreCase) != -1
+                    || (set.Metadata.TitleUnicode ?? string.Empty).IndexOf(SearchText, StringComparison.InvariantCultureIgnoreCase) != -1;
+
+                switch (g.State)
+                {
+                    case BeatmapGroupState.Hidden:
+                        if (match) g.State = BeatmapGroupState.Collapsed;
+                        break;
+                    default:
+                        if (!match) g.State = BeatmapGroupState.Hidden;
+                        break;
+                }
+            }
+
+            switch (Sort)
+            {
+                default:
+                case SortMode.Artist:
+                    groups.Sort((x, y) => string.Compare(x.BeatmapSet.Metadata.Artist, y.BeatmapSet.Metadata.Artist, StringComparison.InvariantCultureIgnoreCase));
+                    break;
+                case SortMode.Title:
+                    groups.Sort((x, y) => string.Compare(x.BeatmapSet.Metadata.Title, y.BeatmapSet.Metadata.Title, StringComparison.InvariantCultureIgnoreCase));
+                    break;
+                case SortMode.Author:
+                    groups.Sort((x, y) => string.Compare(x.BeatmapSet.Metadata.Author, y.BeatmapSet.Metadata.Author, StringComparison.InvariantCultureIgnoreCase));
+                    break;
+                case SortMode.Difficulty:
+                    groups.Sort((x, y) => x.BeatmapSet.MaxStarDifficulty.CompareTo(y.BeatmapSet.MaxStarDifficulty));
+                    break;
+            }
+        }
+    }
+}

osu.Game/Screens/Select/SongSelect.cs

@@ -2,10 +2,8 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
-using System.Threading.Tasks;
 using OpenTK;
 using OpenTK.Input;
 using osu.Framework.Allocation;
@@ -19,7 +17,6 @@ using osu.Framework.Graphics.Primitives;
 using osu.Framework.Graphics.Transforms;
 using osu.Framework.Input;
 using osu.Framework.Screens;
-using osu.Framework.Threading;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.Drawables;
 using osu.Game.Database;
@@ -38,7 +35,7 @@ namespace osu.Game.Screens.Select
         private BeatmapDatabase database;
         protected override BackgroundScreen CreateBackground() => new BackgroundScreenBeatmap(Beatmap);
 
-        private CarouselContainer carousel;
+        private BeatmapCarousel carousel;
         private TrackManager trackManager;
         private DialogOverlay dialogOverlay;
 
@@ -51,8 +48,6 @@ namespace osu.Game.Screens.Select
         private SampleChannel sampleChangeDifficulty;
         private SampleChannel sampleChangeBeatmap;
 
-        private List<BeatmapGroup> beatmapGroups;
-
         protected virtual bool ShowFooter => true;
 
         /// <summary>
@@ -72,7 +67,6 @@ namespace osu.Game.Screens.Select
             const float carousel_width = 640;
             const float filter_height = 100;
 
-            beatmapGroups = new List<BeatmapGroup>();
             Add(new ParallaxContainer
             {
                 Padding = new MarginPadding { Top = filter_height },
@@ -87,18 +81,20 @@ namespace osu.Game.Screens.Select
                     }
                 }
             });
-            Add(carousel = new CarouselContainer
+            Add(carousel = new BeatmapCarousel
             {
                 RelativeSizeAxes = Axes.Y,
                 Size = new Vector2(carousel_width, 1),
                 Anchor = Anchor.CentreRight,
                 Origin = Anchor.CentreRight,
+                SelectionChanged = selectionChanged,
+                StartRequested = raiseSelect
             });
             Add(FilterControl = new FilterControl
             {
                 RelativeSizeAxes = Axes.X,
                 Height = filter_height,
-                FilterChanged = () => filterChanged(),
+                FilterChanged = criteria => filterChanged(criteria),
                 Exit = Exit,
             });
             Add(beatmapInfoWedge = new BeatmapInfoWedge
@@ -132,8 +128,7 @@ namespace osu.Game.Screens.Select
         }
 
         [BackgroundDependencyLoader(permitNulls: true)]
-        private void load(BeatmapDatabase beatmaps, AudioManager audio, DialogOverlay dialog, Framework.Game game,
-            OsuGame osu, OsuColour colours)
+        private void load(BeatmapDatabase beatmaps, AudioManager audio, DialogOverlay dialog, OsuGame osu, OsuColour colours)
         {
             if (Footer != null)
             {
@@ -161,7 +156,16 @@ namespace osu.Game.Screens.Select
 
             initialAddSetsTask = new CancellationTokenSource();
 
-            Task.Factory.StartNew(() => addBeatmapSets(game, initialAddSetsTask.Token), initialAddSetsTask.Token);
+            carousel.BeatmapsChanged = beatmapsLoaded;
+            carousel.Beatmaps = database.Query<BeatmapSetInfo>().Where(b => !b.DeletePending);
+        }
+
+        private void beatmapsLoaded()
+        {
+            if (Beatmap != null)
+                carousel.SelectBeatmap(Beatmap.BeatmapInfo, false);
+            else
+                carousel.SelectNext();
         }
 
         private void raiseSelect()
@@ -173,61 +177,15 @@ namespace osu.Game.Screens.Select
         }
 
         public void SelectRandom() => carousel.SelectRandom();
+
         protected abstract void OnSelected();
 
-        private ScheduledDelegate filterTask;
-
-        private void filterChanged(bool debounce = true, bool eagerSelection = true)
+        private void filterChanged(FilterCriteria criteria, bool debounce = true)
         {
-            filterTask?.Cancel();
-            filterTask = Scheduler.AddDelayed(() =>
-            {
-                filterTask = null;
-                var search = FilterControl.Search;
-                BeatmapGroup newSelection = null;
-                carousel.Sort(FilterControl.Sort);
-                foreach (var beatmapGroup in carousel)
-                {
-                    var set = beatmapGroup.BeatmapSet;
-
-                    bool hasCurrentMode = set.Beatmaps.Any(bm => bm.Mode == playMode);
-
-                    bool match = hasCurrentMode;
-
-                    match &= string.IsNullOrEmpty(search)
-                        || (set.Metadata.Artist ?? "").IndexOf(search, StringComparison.InvariantCultureIgnoreCase) != -1
-                        || (set.Metadata.ArtistUnicode ?? "").IndexOf(search, StringComparison.InvariantCultureIgnoreCase) != -1
-                        || (set.Metadata.Title ?? "").IndexOf(search, StringComparison.InvariantCultureIgnoreCase) != -1
-                        || (set.Metadata.TitleUnicode ?? "").IndexOf(search, StringComparison.InvariantCultureIgnoreCase) != -1;
-
-                    if (match)
-                    {
-                        if (newSelection == null || beatmapGroup.BeatmapSet.OnlineBeatmapSetID == Beatmap.BeatmapSetInfo.OnlineBeatmapSetID)
-                        {
-                            if (newSelection != null)
-                                newSelection.State = BeatmapGroupState.Collapsed;
-                            newSelection = beatmapGroup;
-                        }
-                        else
-                            beatmapGroup.State = BeatmapGroupState.Collapsed;
-                    }
-                    else
-                    {
-                        beatmapGroup.State = BeatmapGroupState.Hidden;
-                    }
-                }
-
-                if (newSelection != null)
-                {
-                    if (newSelection.BeatmapPanels.Any(b => b.Beatmap.ID == Beatmap.BeatmapInfo.ID))
-                        carousel.SelectBeatmap(Beatmap.BeatmapInfo, false);
-                    else if (eagerSelection)
-                        carousel.SelectBeatmap(newSelection.BeatmapSet.Beatmaps[0], false);
-                }
-            }, debounce ? 250 : 0);
+            carousel.Filter(criteria, debounce);
         }
 
-        private void onBeatmapSetAdded(BeatmapSetInfo s) => Schedule(() => addBeatmapSet(s, Game, true));
+        private void onBeatmapSetAdded(BeatmapSetInfo s) => carousel.AddBeatmap(s);
 
         private void onBeatmapSetRemoved(BeatmapSetInfo s) => Schedule(() => removeBeatmapSet(s));
 
@@ -288,10 +246,7 @@ namespace osu.Game.Screens.Select
             initialAddSetsTask.Cancel();
         }
 
-        private void playMode_ValueChanged(object sender, EventArgs e)
-        {
-            filterChanged(false);
-        }
+        private void playMode_ValueChanged(object sender, EventArgs e) => carousel.Filter();
 
         private void changeBackground(WorkingBeatmap beatmap)
         {
@@ -352,63 +307,18 @@ namespace osu.Game.Screens.Select
             }
         }
 
-        private void addBeatmapSet(BeatmapSetInfo beatmapSet, Framework.Game game, bool select = false)
+        private void selectBeatmap(BeatmapSetInfo beatmapSet = null)
         {
-            beatmapSet = database.GetWithChildren<BeatmapSetInfo>(beatmapSet.ID);
-            beatmapSet.Beatmaps.ForEach(b =>
-            {
-                database.GetChildren(b);
-                if (b.Metadata == null) b.Metadata = beatmapSet.Metadata;
-            });
-
-            var group = new BeatmapGroup(beatmapSet, database)
-            {
-                SelectionChanged = selectionChanged,
-                StartRequested = b => raiseSelect()
-            };
-
-            //for the time being, let's completely load the difficulty panels in the background.
-            //this likely won't scale so well, but allows us to completely async the loading flow.
-            Task.WhenAll(group.BeatmapPanels.Select(panel => panel.LoadAsync(game))).ContinueWith(task => Schedule(delegate
-            {
-                beatmapGroups.Add(group);
-
-                group.State = BeatmapGroupState.Collapsed;
-                carousel.AddGroup(group);
-
-                filterChanged(false, false);
-
-                if (Beatmap == null || select)
-                    carousel.SelectBeatmap(beatmapSet.Beatmaps.First());
-                else
-                    carousel.SelectBeatmap(Beatmap.BeatmapInfo);
-            }));
+            carousel.SelectBeatmap(beatmapSet != null ? beatmapSet.Beatmaps.First() : Beatmap?.BeatmapInfo);
         }
 
         private void removeBeatmapSet(BeatmapSetInfo beatmapSet)
         {
-            var group = beatmapGroups.Find(b => b.BeatmapSet.ID == beatmapSet.ID);
-            if (group == null) return;
-
-            if (carousel.SelectedGroup == group)
-                carousel.SelectNext();
-
-            beatmapGroups.Remove(group);
-            carousel.RemoveGroup(group);
-
-            if (beatmapGroups.Count == 0)
+            carousel.RemoveBeatmap(beatmapSet);
+            if (carousel.SelectedBeatmap == null)
                 Beatmap = null;
         }
 
-        private void addBeatmapSets(Framework.Game game, CancellationToken token)
-        {
-            foreach (var beatmapSet in database.Query<BeatmapSetInfo>().Where(b => !b.DeletePending))
-            {
-                if (token.IsCancellationRequested) return;
-                addBeatmapSet(beatmapSet, game);
-            }
-        }
-
         private void promptDelete()
         {
             if (Beatmap != null)

osu.Game/osu.Game.csproj

@@ -197,7 +197,8 @@
     <Compile Include="Screens\Play\PlayerLoader.cs" />
     <Compile Include="Screens\Play\SkipButton.cs" />
     <Compile Include="Modes\UI\StandardComboCounter.cs" />
-    <Compile Include="Screens\Select\CarouselContainer.cs" />
+    <Compile Include="Screens\Select\BeatmapCarousel.cs" />
+    <Compile Include="Screens\Select\FilterCriteria.cs" />
     <Compile Include="Screens\Select\Filter\GroupMode.cs" />
     <Compile Include="Screens\Select\Filter\SortMode.cs" />
     <Compile Include="Screens\Select\MatchSongSelect.cs" />