Merge pull request #3736 from smoogipoo/inter-column-movements

Implement inter-column note movements

osu.Game.Rulesets.Mania.Tests/ManiaPlacementBlueprintTestCase.cs

@@ -46,5 +46,7 @@ namespace osu.Game.Rulesets.Mania.Tests
         protected override void AddHitObject(DrawableHitObject hitObject) => column.Add((DrawableManiaHitObject)hitObject);
 
         public Column ColumnAt(Vector2 screenSpacePosition) => column;
+
+        public int TotalColumns => 1;
     }
 }

osu.Game.Rulesets.Mania.Tests/ManiaSelectionBlueprintTestCase.cs

@@ -2,14 +2,37 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using osu.Framework.Allocation;
+using osu.Framework.Graphics;
 using osu.Framework.Timing;
+using osu.Game.Rulesets.Mania.Edit;
+using osu.Game.Rulesets.Mania.UI;
 using osu.Game.Tests.Visual;
+using osuTK;
+using osuTK.Graphics;
 
 namespace osu.Game.Rulesets.Mania.Tests
 {
-    public abstract class ManiaSelectionBlueprintTestCase : SelectionBlueprintTestCase
+    [Cached(Type = typeof(IManiaHitObjectComposer))]
+    public abstract class ManiaSelectionBlueprintTestCase : SelectionBlueprintTestCase, IManiaHitObjectComposer
     {
         [Cached(Type = typeof(IAdjustableClock))]
         private readonly IAdjustableClock clock = new StopwatchClock();
+
+        private readonly Column column;
+
+        protected ManiaSelectionBlueprintTestCase()
+        {
+            Add(column = new Column(0)
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                AccentColour = Color4.OrangeRed,
+                Clock = new FramedClock(new StopwatchClock()), // No scroll
+            });
+        }
+
+        public Column ColumnAt(Vector2 screenSpacePosition) => column;
+
+        public int TotalColumns => 1;
     }
 }

osu.Game.Rulesets.Mania/Edit/Blueprints/ManiaSelectionBlueprint.cs

@@ -15,6 +15,9 @@ namespace osu.Game.Rulesets.Mania.Edit.Blueprints
 {
     public class ManiaSelectionBlueprint : SelectionBlueprint
     {
+        public Vector2 ScreenSpaceDragPosition { get; private set; }
+        public Vector2 DragPosition { get; private set; }
+
         protected new DrawableManiaHitObject HitObject => (DrawableManiaHitObject)base.HitObject;
 
         protected IClock EditorClock { get; private set; }
@@ -22,6 +25,9 @@ namespace osu.Game.Rulesets.Mania.Edit.Blueprints
         [Resolved]
         private IScrollingInfo scrollingInfo { get; set; }
 
+        [Resolved]
+        private IManiaHitObjectComposer composer { get; set; }
+
         public ManiaSelectionBlueprint(DrawableHitObject hitObject)
             : base(hitObject)
         {
@@ -41,27 +47,22 @@ namespace osu.Game.Rulesets.Mania.Edit.Blueprints
             Position = Parent.ToLocalSpace(HitObject.ToScreenSpace(Vector2.Zero));
         }
 
-        public override void AdjustPosition(DragEvent dragEvent)
+        protected override bool OnMouseDown(MouseDownEvent e)
         {
-            var objectParent = HitObject.Parent;
+            ScreenSpaceDragPosition = e.ScreenSpaceMousePosition;
+            DragPosition = HitObject.ToLocalSpace(e.ScreenSpaceMousePosition);
 
-            // Using the hitobject position is required since AdjustPosition can be invoked multiple times per frame
+            return base.OnMouseDown(e);
-            // without the position having been updated by the parenting ScrollingHitObjectContainer
+        }
-            HitObject.Y += dragEvent.Delta.Y;
 
-            float targetPosition;
+        protected override bool OnDrag(DragEvent e)
+        {
+            var result = base.OnDrag(e);
 
-            // If we're scrolling downwards, a position of 0 is actually further away from the hit target
+            ScreenSpaceDragPosition = e.ScreenSpaceMousePosition;
-            // so we need to flip the vertical coordinate in the hitobject container's space
+            DragPosition = HitObject.ToLocalSpace(e.ScreenSpaceMousePosition);
-            if (scrollingInfo.Direction.Value == ScrollingDirection.Down)
-                targetPosition = -HitObject.Position.Y;
-            else
-                targetPosition = HitObject.Position.Y;
 
-            HitObject.HitObject.StartTime = scrollingInfo.Algorithm.TimeAt(targetPosition,
+            return result;
-                EditorClock.CurrentTime,
-                scrollingInfo.TimeRange.Value,
-                objectParent.DrawHeight);
         }
 
         public override void Show()

osu.Game.Rulesets.Mania/Edit/IManiaHitObjectComposer.cs

@@ -9,5 +9,7 @@ namespace osu.Game.Rulesets.Mania.Edit
     public interface IManiaHitObjectComposer
     {
         Column ColumnAt(Vector2 screenSpacePosition);
+
+        int TotalColumns { get; }
     }
 }

osu.Game.Rulesets.Mania/Edit/ManiaHitObjectComposer.cs

@@ -12,6 +12,7 @@ using osu.Framework.Allocation;
 using osu.Game.Rulesets.Mania.Edit.Blueprints;
 using osu.Game.Rulesets.Mania.UI;
 using osu.Game.Rulesets.UI;
+using osu.Game.Screens.Edit.Compose.Components;
 using osuTK;
 
 namespace osu.Game.Rulesets.Mania.Edit
@@ -38,6 +39,8 @@ namespace osu.Game.Rulesets.Mania.Edit
         protected override IReadOnlyDependencyContainer CreateChildDependencies(IReadOnlyDependencyContainer parent)
             => dependencies = new DependencyContainer(base.CreateChildDependencies(parent));
 
+        public int TotalColumns => ((ManiaPlayfield)RulesetContainer.Playfield).TotalColumns;
+
         protected override RulesetContainer<ManiaHitObject> CreateRulesetContainer(Ruleset ruleset, WorkingBeatmap beatmap)
         {
             RulesetContainer = new ManiaEditRulesetContainer(ruleset, beatmap);
@@ -54,6 +57,8 @@ namespace osu.Game.Rulesets.Mania.Edit
             new HoldNoteCompositionTool()
         };
 
+        public override SelectionHandler CreateSelectionHandler() => new ManiaSelectionHandler();
+
         public override SelectionBlueprint CreateBlueprintFor(DrawableHitObject hitObject)
         {
             switch (hitObject)

osu.Game.Rulesets.Mania/Edit/ManiaSelectionHandler.cs

@@ -0,0 +1,125 @@
+// 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.Input.Events;
+using osu.Framework.Timing;
+using osu.Game.Rulesets.Edit;
+using osu.Game.Rulesets.Mania.Edit.Blueprints;
+using osu.Game.Rulesets.Mania.Objects;
+using osu.Game.Rulesets.UI;
+using osu.Game.Rulesets.UI.Scrolling;
+using osu.Game.Screens.Edit.Compose.Components;
+using osuTK;
+
+namespace osu.Game.Rulesets.Mania.Edit
+{
+    public class ManiaSelectionHandler : SelectionHandler
+    {
+        [Resolved]
+        private IScrollingInfo scrollingInfo { get; set; }
+
+        [Resolved]
+        private IManiaHitObjectComposer composer { get; set; }
+
+        private IClock editorClock;
+
+        [BackgroundDependencyLoader]
+        private void load(IAdjustableClock clock)
+        {
+            editorClock = clock;
+        }
+
+        public override void HandleDrag(SelectionBlueprint blueprint, DragEvent dragEvent)
+        {
+            adjustOrigins((ManiaSelectionBlueprint)blueprint);
+            performDragMovement(dragEvent);
+            performColumnMovement(dragEvent);
+
+            base.HandleDrag(blueprint, dragEvent);
+        }
+
+        /// <summary>
+        /// Ensures that the position of hitobjects remains centred to the mouse position.
+        /// E.g. The hitobject position will change if the editor scrolls while a hitobject is dragged.
+        /// </summary>
+        /// <param name="reference">The <see cref="ManiaSelectionBlueprint"/> that received the drag event.</param>
+        private void adjustOrigins(ManiaSelectionBlueprint reference)
+        {
+            var referenceParent = (HitObjectContainer)reference.HitObject.Parent;
+
+            float offsetFromReferenceOrigin = reference.DragPosition.Y - reference.HitObject.OriginPosition.Y;
+            float targetPosition = referenceParent.ToLocalSpace(reference.ScreenSpaceDragPosition).Y - offsetFromReferenceOrigin;
+
+            // Flip the vertical coordinate space when scrolling downwards
+            if (scrollingInfo.Direction.Value == ScrollingDirection.Down)
+                targetPosition = targetPosition - referenceParent.DrawHeight;
+
+            float movementDelta = targetPosition - reference.HitObject.Position.Y;
+
+            foreach (var b in SelectedBlueprints.OfType<ManiaSelectionBlueprint>())
+                b.HitObject.Y += movementDelta;
+        }
+
+        private void performDragMovement(DragEvent dragEvent)
+        {
+            foreach (var b in SelectedBlueprints)
+            {
+                var hitObject = b.HitObject;
+
+                var objectParent = (HitObjectContainer)hitObject.Parent;
+
+                // Using the hitobject position is required since AdjustPosition can be invoked multiple times per frame
+                // without the position having been updated by the parenting ScrollingHitObjectContainer
+                hitObject.Y += dragEvent.Delta.Y;
+
+                float targetPosition;
+
+                // If we're scrolling downwards, a position of 0 is actually further away from the hit target
+                // so we need to flip the vertical coordinate in the hitobject container's space
+                if (scrollingInfo.Direction.Value == ScrollingDirection.Down)
+                    targetPosition = -hitObject.Position.Y;
+                else
+                    targetPosition = hitObject.Position.Y;
+
+                objectParent.Remove(hitObject);
+
+                hitObject.HitObject.StartTime = scrollingInfo.Algorithm.TimeAt(targetPosition,
+                    editorClock.CurrentTime,
+                    scrollingInfo.TimeRange.Value,
+                    objectParent.DrawHeight);
+
+                objectParent.Add(hitObject);
+            }
+        }
+
+        private void performColumnMovement(DragEvent dragEvent)
+        {
+            var lastColumn = composer.ColumnAt(dragEvent.ScreenSpaceLastMousePosition);
+            var currentColumn = composer.ColumnAt(dragEvent.ScreenSpaceMousePosition);
+            if (lastColumn == null || currentColumn == null)
+                return;
+
+            int columnDelta = currentColumn.Index - lastColumn.Index;
+            if (columnDelta == 0)
+                return;
+
+            int minColumn = int.MaxValue;
+            int maxColumn = int.MinValue;
+
+            foreach (var obj in SelectedHitObjects.OfType<ManiaHitObject>())
+            {
+                if (obj.Column < minColumn)
+                    minColumn = obj.Column;
+                if (obj.Column > maxColumn)
+                    maxColumn = obj.Column;
+            }
+
+            columnDelta = MathHelper.Clamp(columnDelta, -minColumn, composer.TotalColumns - 1 - maxColumn);
+
+            foreach (var obj in SelectedHitObjects.OfType<ManiaHitObject>())
+                obj.Column += columnDelta;
+        }
+    }
+}

osu.Game.Rulesets.Mania/Objects/ManiaHitObject.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 osu.Framework.Configuration;
 using osu.Game.Rulesets.Mania.Objects.Types;
 using osu.Game.Rulesets.Objects;
 
@@ -8,7 +9,13 @@ namespace osu.Game.Rulesets.Mania.Objects
 {
     public abstract class ManiaHitObject : HitObject, IHasColumn
     {
-        public virtual int Column { get; set; }
+        public readonly Bindable<int> ColumnBindable = new Bindable<int>();
+
+        public virtual int Column
+        {
+            get => ColumnBindable;
+            set => ColumnBindable.Value = value;
+        }
 
         protected override HitWindows CreateHitWindows() => new ManiaHitWindows();
     }

osu.Game.Rulesets.Mania/UI/Column.cs

@@ -145,11 +145,13 @@ namespace osu.Game.Rulesets.Mania.UI
             HitObjectContainer.Add(hitObject);
         }
 
-        public override void Remove(DrawableHitObject h)
+        public override bool Remove(DrawableHitObject h)
         {
-            h.OnNewResult -= OnNewResult;
+            if (!base.Remove(h))
+                return false;
 
-            HitObjectContainer.Remove(h);
+            h.OnNewResult -= OnNewResult;
+            return true;
         }
 
         internal void OnNewResult(DrawableHitObject judgedObject, JudgementResult result)

osu.Game.Rulesets.Mania/UI/ManiaPlayfield.cs

@@ -55,7 +55,7 @@ namespace osu.Game.Rulesets.Mania.UI
 
         public override void Add(DrawableHitObject h) => getStageByColumn(((ManiaHitObject)h.HitObject).Column).Add(h);
 
-        public override void Remove(DrawableHitObject h) => getStageByColumn(((ManiaHitObject)h.HitObject).Column).Remove(h);
+        public override bool Remove(DrawableHitObject h) => getStageByColumn(((ManiaHitObject)h.HitObject).Column).Remove(h);
 
         public void Add(BarLine barline) => stages.ForEach(s => s.Add(barline));
 
@@ -86,6 +86,11 @@ namespace osu.Game.Rulesets.Mania.UI
             return found;
         }
 
+        /// <summary>
+        /// Retrieves the total amount of columns across all stages in this playfield.
+        /// </summary>
+        public int TotalColumns => stages.Sum(s => s.Columns.Count);
+
         private ManiaStage getStageByColumn(int column)
         {
             int sum = 0;

osu.Game.Rulesets.Mania/UI/ManiaStage.cs

@@ -156,18 +156,29 @@ namespace osu.Game.Rulesets.Mania.UI
         public override void Add(DrawableHitObject h)
         {
             var maniaObject = (ManiaHitObject)h.HitObject;
-            int columnIndex = maniaObject.Column - firstColumnIndex;
+
-            Columns.ElementAt(columnIndex).Add(h);
+            int columnIndex = -1;
+
+            maniaObject.ColumnBindable.BindValueChanged(_ =>
+            {
+                if (columnIndex != -1)
+                    Columns.ElementAt(columnIndex).Remove(h);
+
+                columnIndex = maniaObject.Column - firstColumnIndex;
+                Columns.ElementAt(columnIndex).Add(h);
+            }, true);
+
             h.OnNewResult += OnNewResult;
         }
 
-        public override void Remove(DrawableHitObject h)
+        public override bool Remove(DrawableHitObject h)
         {
             var maniaObject = (ManiaHitObject)h.HitObject;
             int columnIndex = maniaObject.Column - firstColumnIndex;
             Columns.ElementAt(columnIndex).Remove(h);
 
             h.OnNewResult -= OnNewResult;
+            return true;
         }
 
         public void Add(BarLine barline) => base.Add(new DrawableBarLine(barline));

osu.Game.Rulesets.Osu/Edit/Blueprints/OsuSelectionBlueprint.cs

@@ -1,7 +1,6 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
-using osu.Framework.Input.Events;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Rulesets.Objects.Drawables;
 using osu.Game.Rulesets.Osu.Objects;
@@ -16,7 +15,5 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints
             : base(hitObject)
         {
         }
-
-        public override void AdjustPosition(DragEvent dragEvent) => OsuObject.Position += dragEvent.Delta;
     }
 }

osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/SliderCircleSelectionBlueprint.cs

@@ -1,7 +1,6 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
-using osu.Framework.Input.Events;
 using osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components;
 using osu.Game.Rulesets.Osu.Objects;
 using osu.Game.Rulesets.Osu.Objects.Drawables;
@@ -10,13 +9,9 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders
 {
     public class SliderCircleSelectionBlueprint : OsuSelectionBlueprint
     {
-        private readonly Slider slider;
-
         public SliderCircleSelectionBlueprint(DrawableOsuHitObject hitObject, Slider slider, SliderPosition position)
             : base(hitObject)
         {
-            this.slider = slider;
-
             InternalChild = new SliderCirclePiece(slider, position);
 
             Select();
@@ -24,7 +19,5 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders
 
         // Todo: This is temporary, since the slider circle masks don't do anything special yet. In the future they will handle input.
         public override bool HandlePositionalInput => false;
-
-        public override void AdjustPosition(DragEvent dragEvent) => slider.Position += dragEvent.Delta;
     }
 }

osu.Game.Rulesets.Osu/Edit/Blueprints/Spinners/SpinnerSelectionBlueprint.cs

@@ -1,7 +1,6 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
-using osu.Framework.Input.Events;
 using osu.Game.Rulesets.Osu.Edit.Blueprints.Spinners.Components;
 using osu.Game.Rulesets.Osu.Objects;
 using osu.Game.Rulesets.Osu.Objects.Drawables;
@@ -20,10 +19,5 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Spinners
         }
 
         public override bool ReceivePositionalInputAt(Vector2 screenSpacePos) => piece.ReceivePositionalInputAt(screenSpacePos);
-
-        public override void AdjustPosition(DragEvent dragEvent)
-        {
-            // Spinners don't support position adjustments
-        }
     }
 }

osu.Game.Rulesets.Osu/Edit/OsuHitObjectComposer.cs

@@ -15,6 +15,7 @@ using osu.Game.Rulesets.Osu.Objects;
 using osu.Game.Rulesets.Osu.Objects.Drawables;
 using osu.Game.Rulesets.Osu.UI;
 using osu.Game.Rulesets.UI;
+using osu.Game.Screens.Edit.Compose.Components;
 
 namespace osu.Game.Rulesets.Osu.Edit
 {
@@ -35,6 +36,8 @@ namespace osu.Game.Rulesets.Osu.Edit
             new SpinnerCompositionTool()
         };
 
+        public override SelectionHandler CreateSelectionHandler() => new OsuSelectionHandler();
+
         protected override Container CreateLayerContainer() => new PlayfieldAdjustmentContainer { RelativeSizeAxes = Axes.Both };
 
         public override SelectionBlueprint CreateBlueprintFor(DrawableHitObject hitObject)

osu.Game.Rulesets.Osu/Edit/OsuSelectionHandler.cs

@@ -0,0 +1,30 @@
+// 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.Input.Events;
+using osu.Game.Rulesets.Edit;
+using osu.Game.Rulesets.Osu.Objects;
+using osu.Game.Screens.Edit.Compose.Components;
+
+namespace osu.Game.Rulesets.Osu.Edit
+{
+    public class OsuSelectionHandler : SelectionHandler
+    {
+        public override void HandleDrag(SelectionBlueprint blueprint, DragEvent dragEvent)
+        {
+            foreach (var h in SelectedHitObjects.OfType<OsuHitObject>())
+            {
+                if (h is Spinner)
+                {
+                    // Spinners don't support position adjustments
+                    continue;
+                }
+
+                h.Position += dragEvent.Delta;
+            }
+
+            base.HandleDrag(blueprint, dragEvent);
+        }
+    }
+}

osu.Game.Tests/Visual/TestCaseHitObjectComposer.cs

@@ -29,7 +29,7 @@ namespace osu.Game.Tests.Visual
     {
         public override IReadOnlyList<Type> RequiredTypes => new[]
         {
-            typeof(SelectionBox),
+            typeof(SelectionHandler),
             typeof(DragBox),
             typeof(HitObjectComposer),
             typeof(OsuHitObjectComposer),

osu.Game/Rulesets/Edit/HitObjectComposer.cs

@@ -171,10 +171,9 @@ namespace osu.Game.Rulesets.Edit
         public virtual SelectionBlueprint CreateBlueprintFor(DrawableHitObject hitObject) => null;
 
         /// <summary>
-        /// Creates a <see cref="SelectionBox"/> which outlines <see cref="DrawableHitObject"/>s
+        /// Creates a <see cref="SelectionHandler"/> which outlines <see cref="DrawableHitObject"/>s and handles movement of selections.
-        /// and handles hitobject pattern adjustments.
         /// </summary>
-        public virtual SelectionBox CreateSelectionBox() => new SelectionBox();
+        public virtual SelectionHandler CreateSelectionHandler() => new SelectionHandler();
 
         /// <summary>
         /// Creates a <see cref="ScalableContainer"/> which provides a layer above or below the <see cref="Playfield"/>.

osu.Game/Rulesets/Edit/SelectionBlueprint.cs

@@ -38,7 +38,7 @@ namespace osu.Game.Rulesets.Edit
         /// <summary>
         /// Invoked when this <see cref="SelectionBlueprint"/> has requested drag.
         /// </summary>
-        public event Action<DragEvent> DragRequested;
+        public event Action<SelectionBlueprint, DragEvent> DragRequested;
 
         /// <summary>
         /// The <see cref="DrawableHitObject"/> which this <see cref="SelectionBlueprint"/> applies to.
@@ -130,12 +130,10 @@ namespace osu.Game.Rulesets.Edit
 
         protected override bool OnDrag(DragEvent e)
         {
-            DragRequested?.Invoke(e);
+            DragRequested?.Invoke(this, e);
             return true;
         }
 
-        public abstract void AdjustPosition(DragEvent dragEvent);
-
         /// <summary>
         /// The screen-space point that causes this <see cref="SelectionBlueprint"/> to be selected.
         /// </summary>

osu.Game/Rulesets/UI/Playfield.cs

@@ -80,7 +80,7 @@ namespace osu.Game.Rulesets.UI
         /// Remove a DrawableHitObject from this Playfield.
         /// </summary>
         /// <param name="h">The DrawableHitObject to remove.</param>
-        public virtual void Remove(DrawableHitObject h) => HitObjectContainer.Remove(h);
+        public virtual bool Remove(DrawableHitObject h) => HitObjectContainer.Remove(h);
 
         /// <summary>
         /// Registers a <see cref="Playfield"/> as a nested <see cref="Playfield"/>.

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

@@ -22,7 +22,7 @@ namespace osu.Game.Screens.Edit.Compose.Components
         private Container<PlacementBlueprint> placementBlueprintContainer;
         private PlacementBlueprint currentPlacement;
 
-        private SelectionBox selectionBox;
+        private SelectionHandler selectionHandler;
 
         private IEnumerable<SelectionBlueprint> selections => selectionBlueprints.Children.Where(c => c.IsAlive);
 
@@ -37,16 +37,16 @@ namespace osu.Game.Screens.Edit.Compose.Components
         [BackgroundDependencyLoader]
         private void load()
         {
-            selectionBox = composer.CreateSelectionBox();
+            selectionHandler = composer.CreateSelectionHandler();
-            selectionBox.DeselectAll = deselectAll;
+            selectionHandler.DeselectAll = deselectAll;
 
             var dragBox = new DragBox(select);
-            dragBox.DragEnd += () => selectionBox.UpdateVisibility();
+            dragBox.DragEnd += () => selectionHandler.UpdateVisibility();
 
             InternalChildren = new[]
             {
                 dragBox,
-                selectionBox,
+                selectionHandler,
                 selectionBlueprints = new SelectionBlueprintContainer { RelativeSizeAxes = Axes.Both },
                 placementBlueprintContainer = new Container<PlacementBlueprint> { RelativeSizeAxes = Axes.Both },
                 dragBox.CreateProxy()
@@ -168,19 +168,19 @@ namespace osu.Game.Screens.Edit.Compose.Components
 
         private void onBlueprintSelected(SelectionBlueprint blueprint)
         {
-            selectionBox.HandleSelected(blueprint);
+            selectionHandler.HandleSelected(blueprint);
             selectionBlueprints.ChangeChildDepth(blueprint, 1);
         }
 
         private void onBlueprintDeselected(SelectionBlueprint blueprint)
         {
-            selectionBox.HandleDeselected(blueprint);
+            selectionHandler.HandleDeselected(blueprint);
             selectionBlueprints.ChangeChildDepth(blueprint, 0);
         }
 
-        private void onSelectionRequested(SelectionBlueprint blueprint, InputState state) => selectionBox.HandleSelectionRequested(blueprint, state);
+        private void onSelectionRequested(SelectionBlueprint blueprint, InputState state) => selectionHandler.HandleSelectionRequested(blueprint, state);
 
-        private void onDragRequested(DragEvent dragEvent) => selectionBox.HandleDrag(dragEvent);
+        private void onDragRequested(SelectionBlueprint blueprint, DragEvent dragEvent) => selectionHandler.HandleDrag(blueprint, dragEvent);
 
         private class SelectionBlueprintContainer : Container<SelectionBlueprint>
         {

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

@@ -46,7 +46,7 @@ namespace osu.Game.Screens.Edit.Compose.Components
             {
                 Masking = true,
                 BorderColour = Color4.White,
-                BorderThickness = SelectionBox.BORDER_RADIUS,
+                BorderThickness = SelectionHandler.BORDER_RADIUS,
                 Child = new Box
                 {
                     RelativeSizeAxes = Axes.Both,

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

@@ -12,26 +12,31 @@ using osu.Framework.Input.Events;
 using osu.Framework.Input.States;
 using osu.Game.Graphics;
 using osu.Game.Rulesets.Edit;
+using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Drawables;
 using osuTK;
 using osuTK.Input;
 
 namespace osu.Game.Screens.Edit.Compose.Components
 {
     /// <summary>
-    /// A box which surrounds <see cref="SelectionBlueprint"/>s and provides interactive handles, context menus etc.
+    /// A component which outlines <see cref="DrawableHitObject"/>s and handles movement of selections.
     /// </summary>
-    public class SelectionBox : CompositeDrawable
+    public class SelectionHandler : CompositeDrawable
     {
         public const float BORDER_RADIUS = 2;
 
+        protected IEnumerable<SelectionBlueprint> SelectedBlueprints => selectedBlueprints;
         private readonly List<SelectionBlueprint> selectedBlueprints;
 
+        protected IEnumerable<HitObject> SelectedHitObjects => selectedBlueprints.Select(b => b.HitObject.HitObject);
+
         private Drawable outline;
 
         [Resolved]
         private IPlacementHandler placementHandler { get; set; }
 
-        public SelectionBox()
+        public SelectionHandler()
         {
             selectedBlueprints = new List<SelectionBlueprint>();
 
@@ -59,12 +64,13 @@ namespace osu.Game.Screens.Edit.Compose.Components
 
         #region User Input Handling
 
-        public void HandleDrag(DragEvent dragEvent)
+        /// <summary>
+        /// Handles the selected <see cref="DrawableHitObject"/>s being dragged.
+        /// </summary>
+        /// <param name="blueprint">The <see cref="SelectionBlueprint"/> that received the drag event.</param>
+        /// <param name="dragEvent">The drag event.</param>
+        public virtual void HandleDrag(SelectionBlueprint blueprint, DragEvent dragEvent)
         {
-            // Todo: Various forms of snapping
-
-            foreach (var blueprint in selectedBlueprints)
-                blueprint.AdjustPosition(dragEvent);
         }
 
         protected override bool OnKeyDown(KeyDownEvent e)
@@ -90,19 +96,19 @@ namespace osu.Game.Screens.Edit.Compose.Components
         /// <summary>
         /// Bind an action to deselect all selected blueprints.
         /// </summary>
-        public Action DeselectAll { private get; set; }
+        internal Action DeselectAll { private get; set; }
 
         /// <summary>
         /// Handle a blueprint becoming selected.
         /// </summary>
         /// <param name="blueprint">The blueprint.</param>
-        public void HandleSelected(SelectionBlueprint blueprint) => selectedBlueprints.Add(blueprint);
+        internal void HandleSelected(SelectionBlueprint blueprint) => selectedBlueprints.Add(blueprint);
 
         /// <summary>
         /// Handle a blueprint becoming deselected.
         /// </summary>
         /// <param name="blueprint">The blueprint.</param>
-        public void HandleDeselected(SelectionBlueprint blueprint)
+        internal void HandleDeselected(SelectionBlueprint blueprint)
         {
             selectedBlueprints.Remove(blueprint);
 
@@ -115,7 +121,7 @@ namespace osu.Game.Screens.Edit.Compose.Components
         /// Handle a blueprint requesting selection.
         /// </summary>
         /// <param name="blueprint">The blueprint.</param>
-        public void HandleSelectionRequested(SelectionBlueprint blueprint, InputState state)
+        internal void HandleSelectionRequested(SelectionBlueprint blueprint, InputState state)
         {
             if (state.Keyboard.ControlPressed)
             {
@@ -139,7 +145,7 @@ namespace osu.Game.Screens.Edit.Compose.Components
         #endregion
 
         /// <summary>
-        /// Updates whether this <see cref="SelectionBox"/> is visible.
+        /// Updates whether this <see cref="SelectionHandler"/> is visible.
         /// </summary>
         internal void UpdateVisibility()
         {