Add beatmap deletion support.

Note that this is a very naive approach and will result in file access exceptions. This will be fixed in a further commit.

osu.Game/Database/BeatmapDatabase.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -22,6 +23,7 @@ namespace osu.Game.Database
         private SQLiteConnection connection { get; set; }
         private Storage storage;
         public event Action<BeatmapSetInfo> BeatmapSetAdded;
+        public event Action<BeatmapSetInfo> BeatmapSetRemoved;
 
         private BeatmapImporter ipc;
 
@@ -157,6 +159,13 @@ namespace osu.Game.Database
             connection.Commit();
         }
 
+        public void Delete(BeatmapSetInfo beatmapSet)
+        {
+            storage.Delete(beatmapSet.Path);
+            connection.Delete(beatmapSet);
+            BeatmapSetRemoved?.Invoke(beatmapSet);
+        }
+
         public ArchiveReader GetReader(BeatmapSetInfo beatmapSet)
         {
             if (string.IsNullOrEmpty(beatmapSet.Path))

osu.Game/Overlays/MusicController.cs

@@ -254,14 +254,16 @@ namespace osu.Game.Overlays
         {
             progress.IsEnabled = (beatmapSource.Value != null);
             if (beatmapSource.Value == current) return;
-            bool audioEquals = current?.BeatmapInfo.AudioEquals(beatmapSource.Value.BeatmapInfo) ?? false;
+            bool audioEquals = current?.BeatmapInfo?.AudioEquals(beatmapSource?.Value?.BeatmapInfo) ?? false;
             current = beatmapSource.Value;
             updateDisplay(current, audioEquals ? TransformDirection.None : TransformDirection.Next);
-            appendToHistory(current.BeatmapInfo);
+            appendToHistory(current?.BeatmapInfo);
         }
 
         private void appendToHistory(BeatmapInfo beatmap)
         {
+            if (beatmap == null) return;
+
             if (playHistoryIndex >= 0)
             {
                 if (beatmap.AudioEquals(playHistory[playHistoryIndex]))

osu.Game/Screens/Select/CarouselContainer.cs

@@ -15,6 +15,7 @@ using osu.Framework.Timing;
 using osu.Framework.Input;
 using OpenTK.Input;
 using System.Collections;
+using System.Diagnostics;
 using osu.Framework.MathUtils;
 
 namespace osu.Game.Screens.Select
@@ -95,6 +96,15 @@ namespace osu.Game.Screens.Select
             computeYPositions();
         }
 
+        public void RemoveGroup(BeatmapGroup group)
+        {
+            groups.Remove(group);
+            scrollableContent.Remove(group.Header);
+            scrollableContent.Remove(group.BeatmapPanels);
+
+            computeYPositions();
+        }
+
         private void movePanel(Panel panel, bool advance, bool animated, ref float currentY)
         {
             yPositions.Add(currentY);
@@ -276,6 +286,12 @@ namespace osu.Game.Screens.Select
             if (direction == 0)
                 return base.OnKeyDown(state, args);
 
+            SelectNext(direction, skipDifficulties);
+            return true;
+        }
+
+        public void SelectNext(int direction = 1, bool skipDifficulties = true)
+        {
             if (!skipDifficulties)
             {
                 int i = SelectedGroup.BeatmapPanels.IndexOf(SelectedPanel) + direction;
@@ -284,7 +300,7 @@ namespace osu.Game.Screens.Select
                 {
                     //changing difficulty panel, not set.
                     SelectGroup(SelectedGroup, SelectedGroup.BeatmapPanels[i]);
-                    return true;
+                    return;
                 }
             }
 
@@ -297,11 +313,9 @@ namespace osu.Game.Screens.Select
                 if (groups[index].State != BeatmapGroupState.Hidden)
                 {
                     SelectBeatmap(groups[index].BeatmapPanels.First().Beatmap);
-                    return true;
+                    return;
                 }
             } while (index != startIndex);
-
-            return true;
         }
 
         public void SelectRandom()

osu.Game/Screens/Select/PlaySongSelect.cs

@@ -139,6 +139,7 @@ namespace osu.Game.Screens.Select
                 database = beatmaps;
 
             database.BeatmapSetAdded += onDatabaseOnBeatmapSetAdded;
+            database.BeatmapSetRemoved += onDatabaseOnBeatmapSetRemoved;
 
             trackManager = audio.Track;
 
@@ -189,6 +190,11 @@ namespace osu.Game.Screens.Select
             Schedule(() => addBeatmapSet(s, Game, true));
         }
 
+        private void onDatabaseOnBeatmapSetRemoved(BeatmapSetInfo s)
+        {
+            Schedule(() => removeBeatmapSet(s));
+        }
+
         protected override void OnEntering(Screen last)
         {
             base.OnEntering(last);
@@ -247,6 +253,7 @@ namespace osu.Game.Screens.Select
                 playMode.ValueChanged -= playMode_ValueChanged;
 
             database.BeatmapSetAdded -= onDatabaseOnBeatmapSetAdded;
+            database.BeatmapSetRemoved -= onDatabaseOnBeatmapSetRemoved;
 
             initialAddSetsTask.Cancel();
         }
@@ -278,7 +285,7 @@ namespace osu.Game.Screens.Select
 
             //todo: change background in selectionChanged instead; support per-difficulty backgrounds.
             changeBackground(beatmap);
-            carousel.SelectBeatmap(beatmap.BeatmapInfo);
+            carousel.SelectBeatmap(beatmap?.BeatmapInfo);
         }
 
         /// <summary>
@@ -353,6 +360,21 @@ namespace osu.Game.Screens.Select
             }));
         }
 
+        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)
+                Beatmap = null;
+        }
+
         private void addBeatmapSets(Framework.Game game, CancellationToken token)
         {
             foreach (var beatmapSet in database.Query<BeatmapSetInfo>())
@@ -369,6 +391,13 @@ namespace osu.Game.Screens.Select
                 case Key.Enter:
                     footer.StartButton.TriggerClick();
                     return true;
+                case Key.Delete:
+                    if (Beatmap != null)
+                    {
+                        Beatmap.Dispose();
+                        database.Delete(Beatmap.BeatmapSetInfo);
+                    }
+                    return true;
             }
 
             return base.OnKeyDown(state, args);