Initial implementation of rearrangeable playlist

osu.Game/Screens/Multi/DrawableRoomPlaylist.cs

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+// 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.Extensions.IEnumerableExtensions;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Graphics.Containers;
+using osu.Game.Online.Multiplayer;
+using osuTK;
+
+namespace osu.Game.Screens.Multi
+{
+    public class DrawableRoomPlaylist : RearrangeableListContainer<PlaylistItem>
+    {
+        public readonly Bindable<PlaylistItem> SelectedItem = new Bindable<PlaylistItem>();
+
+        private readonly bool allowEdit;
+        private readonly bool allowSelection;
+
+        public DrawableRoomPlaylist(bool allowEdit, bool allowSelection)
+        {
+            this.allowEdit = allowEdit;
+            this.allowSelection = allowSelection;
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            SelectedItem.BindValueChanged(item =>
+            {
+                if (item.OldValue != null && ItemMap.TryGetValue(item.OldValue, out var oldItem))
+                    ((DrawableRoomPlaylistItem)oldItem).Deselect();
+
+                if (item.NewValue != null && ItemMap.TryGetValue(item.NewValue, out var newItem))
+                    ((DrawableRoomPlaylistItem)newItem).Select();
+            }, true);
+
+            Items.ItemsRemoved += items =>
+            {
+                if (items.Any(i => i == SelectedItem.Value))
+                    SelectedItem.Value = null;
+            };
+        }
+
+        protected override ScrollContainer<Drawable> CreateScrollContainer() => new OsuScrollContainer
+        {
+            ScrollbarVisible = false
+        };
+
+        protected override FillFlowContainer<RearrangeableListItem<PlaylistItem>> CreateListFillFlowContainer() => new FillFlowContainer<RearrangeableListItem<PlaylistItem>>
+        {
+            LayoutDuration = 200,
+            LayoutEasing = Easing.OutQuint,
+            Spacing = new Vector2(0, 2)
+        };
+
+        protected override RearrangeableListItem<PlaylistItem> CreateDrawable(PlaylistItem item) => new DrawableRoomPlaylistItem(item, allowEdit, allowSelection)
+        {
+            RequestSelection = requestSelection,
+            RequestDeletion = requestDeletion
+        };
+
+        private void requestSelection(PlaylistItem item) => SelectedItem.Value = item;
+
+        private void requestDeletion(PlaylistItem item)
+        {
+            if (SelectedItem.Value == item)
+            {
+                if (Items.Count == 1)
+                    SelectedItem.Value = null;
+                else
+                    SelectedItem.Value = Items.GetNext(item) ?? Items[^2];
+            }
+
+            Items.Remove(item);
+        }
+    }
+}