Add difficulty, artist and title sort examples

Also:

- Adds hinting at grouping and header status of items
- Passes through criteria and prepare for grouping tests.
- Makes `Filters` list `protected` because naming clash with `Filter()`
  on `BeatmapCarousel`.

osu.Game.Tests/Visual/SongSelect/TestSceneBeatmapCarouselV2.cs

@@ -17,10 +17,13 @@ using osu.Framework.Utils;
 using osu.Game.Beatmaps;
 using osu.Game.Database;
 using osu.Game.Graphics.Containers;
+using osu.Game.Screens.Select;
+using osu.Game.Screens.Select.Filter;
 using osu.Game.Screens.SelectV2;
 using osu.Game.Tests.Beatmaps;
 using osu.Game.Tests.Resources;
 using osuTK.Graphics;
+using BeatmapCarousel = osu.Game.Screens.SelectV2.BeatmapCarousel;
 
 namespace osu.Game.Tests.Visual.SongSelect
 {
@@ -123,6 +126,11 @@ namespace osu.Game.Tests.Visual.SongSelect
                     },
                 };
             });
+
+            AddStep("sort by title", () =>
+            {
+                carousel.Filter(new FilterCriteria { Sort = SortMode.Title });
+            });
         }
 
         [Test]
@@ -139,6 +147,26 @@ namespace osu.Game.Tests.Visual.SongSelect
             AddStep("remove all beatmaps", () => beatmapSets.Clear());
         }
 
+        [Test]
+        public void TestSorting()
+        {
+            AddStep("add 10 beatmaps", () =>
+            {
+                for (int i = 0; i < 10; i++)
+                    beatmapSets.Add(TestResources.CreateTestBeatmapSetInfo(RNG.Next(1, 4)));
+            });
+
+            AddStep("sort by difficulty", () =>
+            {
+                carousel.Filter(new FilterCriteria { Sort = SortMode.Difficulty });
+            });
+
+            AddStep("sort by artist", () =>
+            {
+                carousel.Filter(new FilterCriteria { Sort = SortMode.Artist });
+            });
+        }
+
         [Test]
         public void TestScrollPositionVelocityMaintained()
         {

osu.Game/Screens/SelectV2/BeatmapCarousel.cs

@@ -31,8 +31,8 @@ namespace osu.Game.Screens.SelectV2
 
             Filters = new ICarouselFilter[]
             {
-                new BeatmapCarouselFilterSorting(),
-                new BeatmapCarouselFilterGrouping(),
+                new BeatmapCarouselFilterSorting(() => Criteria),
+                new BeatmapCarouselFilterGrouping(() => Criteria),
             };
 
             AddInternal(carouselPanelPool);

osu.Game/Screens/SelectV2/BeatmapCarouselFilterGrouping.cs

@@ -1,19 +1,36 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using osu.Game.Beatmaps;
+using osu.Game.Screens.Select;
 
 namespace osu.Game.Screens.SelectV2
 {
     public class BeatmapCarouselFilterGrouping : ICarouselFilter
     {
+        private readonly Func<FilterCriteria> getCriteria;
+
+        public BeatmapCarouselFilterGrouping(Func<FilterCriteria> getCriteria)
+        {
+            this.getCriteria = getCriteria;
+        }
+
         public async Task<IEnumerable<CarouselItem>> Run(IEnumerable<CarouselItem> items, CancellationToken cancellationToken) => await Task.Run(() =>
         {
-            // TODO: perform grouping based on FilterCriteria
+            var criteria = getCriteria();
+
+            if (criteria.SplitOutDifficulties)
+            {
+                foreach (var item in items)
+                    ((BeatmapCarouselItem)item).HasGroupHeader = false;
+
+                return items;
+            }
 
             CarouselItem? lastItem = null;
 
@@ -23,15 +40,18 @@ namespace osu.Game.Screens.SelectV2
             {
                 cancellationToken.ThrowIfCancellationRequested();
 
-                if (item.Model is BeatmapInfo b1)
+                if (item.Model is BeatmapInfo b)
                 {
                     // Add set header
-                    if (lastItem == null || (lastItem.Model is BeatmapInfo b2 && b2.BeatmapSet!.OnlineID != b1.BeatmapSet!.OnlineID))
-                        newItems.Add(new BeatmapCarouselItem(b1.BeatmapSet!));
+                    if (lastItem == null || (lastItem.Model is BeatmapInfo b2 && b2.BeatmapSet!.OnlineID != b.BeatmapSet!.OnlineID))
+                        newItems.Add(new BeatmapCarouselItem(b.BeatmapSet!) { IsGroupHeader = true });
                 }
 
                 newItems.Add(item);
                 lastItem = item;
+
+                var beatmapCarouselItem = (BeatmapCarouselItem)item;
+                beatmapCarouselItem.HasGroupHeader = true;
             }
 
             return newItems;

osu.Game/Screens/SelectV2/BeatmapCarouselFilterSorting.cs

@@ -1,22 +1,59 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using osu.Game.Beatmaps;
+using osu.Game.Screens.Select;
+using osu.Game.Screens.Select.Filter;
+using osu.Game.Utils;
 
 namespace osu.Game.Screens.SelectV2
 {
     public class BeatmapCarouselFilterSorting : ICarouselFilter
     {
+        private readonly Func<FilterCriteria> getCriteria;
+
+        public BeatmapCarouselFilterSorting(Func<FilterCriteria> getCriteria)
+        {
+            this.getCriteria = getCriteria;
+        }
+
         public async Task<IEnumerable<CarouselItem>> Run(IEnumerable<CarouselItem> items, CancellationToken cancellationToken) => await Task.Run(() =>
         {
+            var criteria = getCriteria();
+
             return items.OrderDescending(Comparer<CarouselItem>.Create((a, b) =>
             {
+                int comparison = 0;
+
                 if (a.Model is BeatmapInfo ab && b.Model is BeatmapInfo bb)
-                    return ab.OnlineID.CompareTo(bb.OnlineID);
+                {
+                    switch (criteria.Sort)
+                    {
+                        case SortMode.Artist:
+                            comparison = OrdinalSortByCaseStringComparer.DEFAULT.Compare(ab.BeatmapSet!.Metadata.Artist, bb.BeatmapSet!.Metadata.Artist);
+                            if (comparison == 0)
+                                goto case SortMode.Title;
+                            break;
+
+                        case SortMode.Difficulty:
+                            comparison = ab.StarRating.CompareTo(bb.StarRating);
+                            break;
+
+                        case SortMode.Title:
+                            comparison = OrdinalSortByCaseStringComparer.DEFAULT.Compare(ab.BeatmapSet!.Metadata.Title, bb.BeatmapSet!.Metadata.Title);
+                            break;
+
+                        default:
+                            throw new ArgumentOutOfRangeException();
+                    }
+                }
+
+                if (comparison != 0) return comparison;
 
                 if (a is BeatmapCarouselItem aItem && b is BeatmapCarouselItem bItem)
                     return aItem.ID.CompareTo(bItem.ID);

osu.Game/Screens/SelectV2/BeatmapCarouselItem.cs

@@ -11,7 +11,19 @@ namespace osu.Game.Screens.SelectV2
     {
         public readonly Guid ID;
 
-        public override float DrawHeight => Model is BeatmapInfo ? 40 : 80;
+        /// <summary>
+        /// Whether this item has a header providing extra information for it.
+        /// When displaying items which don't have header, we should make sure enough information is included inline.
+        /// </summary>
+        public bool HasGroupHeader { get; set; }
+
+        /// <summary>
+        /// Whether this item is a group header.
+        /// Group headers are generally larger in display. Setting this will account for the size difference.
+        /// </summary>
+        public bool IsGroupHeader { get; set; }
+
+        public override float DrawHeight => IsGroupHeader ? 80 : 40;
 
         public BeatmapCarouselItem(object model)
             : base(model)

osu.Game/Screens/SelectV2/Carousel.cs

@@ -29,7 +29,7 @@ namespace osu.Game.Screens.SelectV2
         /// <summary>
         /// A collection of filters which should be run each time a <see cref="QueueFilter"/> is executed.
         /// </summary>
-        public IEnumerable<ICarouselFilter> Filters { get; init; } = Enumerable.Empty<ICarouselFilter>();
+        protected IEnumerable<ICarouselFilter> Filters { get; init; } = Enumerable.Empty<ICarouselFilter>();
 
         /// <summary>
         /// Height of the area above the carousel that should be treated as visible due to transparency of elements in front of it.