Implement hitobject deletion

osu.Game.Tests/Visual/TestCaseHitObjectComposer.cs

@@ -77,5 +77,7 @@ namespace osu.Game.Tests.Visual
         }
 
         public void EndPlacement(HitObject hitObject) => composer.Add(hitObject);
+
+        public void Delete(HitObject hitObject) => composer.Remove(hitObject);
     }
 }

osu.Game/Rulesets/Edit/EditRulesetContainer.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System.Linq;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Game.Beatmaps;
@@ -28,6 +29,13 @@ namespace osu.Game.Rulesets.Edit
         /// <param name="hitObject">The <see cref="HitObject"/> to add.</param>
         /// <returns>The visual representation of <paramref name="hitObject"/>.</returns>
         internal abstract DrawableHitObject Add(HitObject hitObject);
+
+        /// <summary>
+        /// Removes a <see cref="HitObject"/> from the <see cref="Beatmap"/> and the display.
+        /// </summary>
+        /// <param name="hitObject">The <see cref="HitObject"/> to remove.</param>
+        /// <returns>The visual representation of the removed <paramref name="hitObject"/>.</returns>
+        internal abstract DrawableHitObject Remove(HitObject hitObject);
     }
 
     public class EditRulesetContainer<TObject> : EditRulesetContainer
@@ -72,5 +80,27 @@ namespace osu.Game.Rulesets.Edit
 
             return drawableObject;
         }
+
+        internal override DrawableHitObject Remove(HitObject hitObject)
+        {
+            var tObject = (TObject)hitObject;
+
+            // Remove from beatmap
+            beatmap.HitObjects.Remove(tObject);
+
+            // Process the beatmap
+            var processor = ruleset.CreateBeatmapProcessor(beatmap);
+
+            processor.PreProcess();
+            processor.PostProcess();
+
+            // Remove visual representation
+            var drawableObject = Playfield.AllHitObjects.Single(d => d.HitObject == hitObject);
+
+            rulesetContainer.Playfield.Remove(drawableObject);
+            rulesetContainer.Playfield.PostProcess();
+
+            return drawableObject;
+        }
     }
 }

osu.Game/Rulesets/Edit/HitObjectComposer.cs

@@ -152,6 +152,8 @@ namespace osu.Game.Rulesets.Edit
             placementContainer.Refresh();
         }
 
+        public void Remove(HitObject hitObject) => maskLayer.RemoveMaskFor(rulesetContainer.Remove(hitObject));
+
         internal abstract EditRulesetContainer CreateRulesetContainer();
 
         protected abstract IReadOnlyList<HitObjectCompositionTool> CompositionTools { get; }

osu.Game/Screens/Edit/Screens/Compose/Compose.cs

@@ -122,5 +122,7 @@ namespace osu.Game.Screens.Edit.Screens.Compose
         }
 
         public void EndPlacement(HitObject hitObject) => composer.Add(hitObject);
+
+        public void Delete(HitObject hitObject) => composer.Remove(hitObject);
     }
 }

osu.Game/Screens/Edit/Screens/Compose/IPlacementHandler.cs

@@ -9,5 +9,7 @@ namespace osu.Game.Screens.Edit.Screens.Compose
     {
         void BeginPlacement(HitObject hitObject);
         void EndPlacement(HitObject hitObject);
+
+        void Delete(HitObject hitObject);
     }
 }

osu.Game/Screens/Edit/Screens/Compose/Layers/HitObjectMaskLayer.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
@@ -69,5 +70,19 @@ namespace osu.Game.Screens.Edit.Screens.Compose.Layers
 
             maskContainer.Add(mask);
         }
+
+        /// <summary>
+        /// Removes a mask for a <see cref="DrawableHitObject"/>.
+        /// </summary>
+        /// <param name="hitObject">The <see cref="DrawableHitObject"/> for which to remove the mask.</param>
+        public void RemoveMaskFor(DrawableHitObject hitObject)
+        {
+            var maskToRemove = maskContainer.Single(m => m.HitObject == hitObject);
+            if (maskToRemove == null)
+                return;
+
+            maskToRemove.Deselect();
+            maskContainer.Remove(maskToRemove);
+        }
     }
 }

osu.Game/Screens/Edit/Screens/Compose/Layers/MaskSelection.cs

@@ -3,15 +3,18 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
+using osu.Framework.Input.Events;
 using osu.Framework.Input.States;
 using osu.Game.Graphics;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Rulesets.Edit.Types;
 using OpenTK;
+using OpenTK.Input;
 
 namespace osu.Game.Screens.Edit.Screens.Compose.Layers
 {
@@ -26,6 +29,9 @@ namespace osu.Game.Screens.Edit.Screens.Compose.Layers
 
         private Drawable outline;
 
+        [Resolved]
+        private IPlacementHandler placementHandler { get; set; }
+
         public MaskSelection()
         {
             selectedMasks = new List<SelectionMask>();
@@ -69,6 +75,21 @@ namespace osu.Game.Screens.Edit.Screens.Compose.Layers
             }
         }
 
+        protected override bool OnKeyDown(KeyDownEvent e)
+        {
+            if (e.Repeat)
+                return base.OnKeyDown(e);
+
+            switch (e.Key)
+            {
+                case Key.Delete:
+                    foreach (var h in selectedMasks.ToList())
+                        placementHandler.Delete(h.HitObject.HitObject);
+                    return true;
+            }
+            return base.OnKeyDown(e);
+        }
+
         #endregion
 
         #region Selection Handling