Implement grouped difficulty icon

osu.Game/Beatmaps/Drawables/GroupedDifficultyIcon.cs

@@ -0,0 +1,58 @@
+// 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 osu.Framework.Graphics;
+using osu.Game.Graphics;
+using osu.Game.Graphics.Sprites;
+using osu.Game.Rulesets;
+using osuTK.Graphics;
+
+namespace osu.Game.Beatmaps.Drawables
+{
+    public class GroupedDifficultyIcon : DifficultyIcon
+    {
+        private readonly OsuSpriteText counter;
+
+        private List<BeatmapInfo> beatmaps;
+
+        protected List<BeatmapInfo> Beatmaps
+        {
+            get => beatmaps;
+            set
+            {
+                beatmaps = value;
+
+                updateDisplay();
+            }
+        }
+
+        public GroupedDifficultyIcon(List<BeatmapInfo> beatmaps, RulesetInfo ruleset, Color4 counterColour)
+            : base(null, ruleset, false)
+        {
+            this.beatmaps = beatmaps;
+
+            AddInternal(counter = new OsuSpriteText
+            {
+                Anchor = Anchor.CentreRight,
+                Origin = Anchor.CentreRight,
+                Padding = new MarginPadding { Left = Size.X },
+                Margin = new MarginPadding { Left = 2, Right = 5 },
+                Font = OsuFont.GetFont(size: 14, weight: FontWeight.SemiBold),
+                Colour = counterColour,
+            });
+
+            updateDisplay();
+        }
+
+        private void updateDisplay()
+        {
+            if (beatmaps == null || beatmaps.Count == 0)
+                return;
+
+            Beatmap = beatmaps.OrderBy(b => b.StarDifficulty).Last();
+            counter.Text = beatmaps.Count.ToString();
+        }
+    }
+}