Move a lot of the implementation to base SelectionHandler

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

@@ -5,7 +5,6 @@
 using System.Linq;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Primitives;
-using osu.Framework.Input.Events;
 using osu.Framework.Utils;
 using osu.Game.Rulesets.Objects.Types;
 using osu.Game.Rulesets.Osu.Objects;
@@ -16,24 +15,22 @@ namespace osu.Game.Rulesets.Osu.Edit
 {
     public class OsuSelectionHandler : SelectionHandler
     {
-        public override ComposeSelectionBox CreateSelectionBox()
-            => new ComposeSelectionBox
-            {
-                CanRotate = true,
-                CanScaleX = true,
-                CanScaleY = true,
+        protected override void OnSelectionChanged()
+        {
+            base.OnSelectionChanged();
 
-                OperationStarted = () => ChangeHandler.BeginChange(),
-                OperationEnded = () =>
-                {
-                    ChangeHandler.EndChange();
-                    referenceOrigin = null;
-                },
+            bool canOperate = SelectedHitObjects.Count() > 1 || SelectedHitObjects.Any(s => s is Slider);
 
-                OnRotation = e => rotateSelection(e.Delta.X),
-                OnScaleX = handleScaleX,
-                OnScaleY = handleScaleY,
-            };
+            SelectionBox.CanRotate = canOperate;
+            SelectionBox.CanScaleX = canOperate;
+            SelectionBox.CanScaleY = canOperate;
+        }
+
+        protected override void OnDragOperationEnded()
+        {
+            base.OnDragOperationEnded();
+            referenceOrigin = null;
+        }
 
         public override bool HandleMovement(MoveSelectionEvent moveEvent) =>
             moveSelection(moveEvent.InstantDelta);
@@ -43,35 +40,35 @@ public override bool HandleMovement(MoveSelectionEvent moveEvent) =>
         /// </summary>
         private Vector2? referenceOrigin;
 
-        private void handleScaleY(DragEvent e, Anchor reference)
+        public override bool HandleScaleY(in float scale, Anchor reference)
         {
             int direction = (reference & Anchor.y0) > 0 ? -1 : 1;
 
             if (direction < 0)
             {
                 // when resizing from a top drag handle, we want to move the selection first
-                if (!moveSelection(new Vector2(0, e.Delta.Y)))
-                    return;
+                if (!moveSelection(new Vector2(0, scale)))
+                    return false;
             }
 
-            scaleSelection(new Vector2(0, direction * e.Delta.Y));
+            return scaleSelection(new Vector2(0, direction * scale));
         }
 
-        private void handleScaleX(DragEvent e, Anchor reference)
+        public override bool HandleScaleX(in float scale, Anchor reference)
         {
             int direction = (reference & Anchor.x0) > 0 ? -1 : 1;
 
             if (direction < 0)
             {
                 // when resizing from a left drag handle, we want to move the selection first
-                if (!moveSelection(new Vector2(e.Delta.X, 0)))
-                    return;
+                if (!moveSelection(new Vector2(scale, 0)))
+                    return false;
             }
 
-            scaleSelection(new Vector2(direction * e.Delta.X, 0));
+            return scaleSelection(new Vector2(direction * scale, 0));
         }
 
-        private bool rotateSelection(in float delta)
+        public override bool HandleRotation(float delta)
         {
             Quad quad = getSelectionQuad();
 
@@ -96,6 +93,7 @@ private bool rotateSelection(in float delta)
                 }
             }
 
+            // todo: not always
             return true;
         }
 
@@ -161,8 +159,14 @@ private bool moveSelection(Vector2 delta)
             return true;
         }
 
+        /// <summary>
+        /// Returns a gamefield-space quad surrounding the current selection.
+        /// </summary>
         private Quad getSelectionQuad()
         {
+            if (!SelectedHitObjects.Any())
+                return new Quad();
+
             Vector2 minPosition = new Vector2(float.MaxValue, float.MaxValue);
             Vector2 maxPosition = new Vector2(float.MinValue, float.MinValue);
 

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

@@ -43,6 +43,8 @@ public class SelectionHandler : CompositeDrawable, IKeyBindingHandler<PlatformAc
 
         private OsuSpriteText selectionDetailsText;
 
+        protected ComposeSelectionBox SelectionBox { get; private set; }
+
         [Resolved(CanBeNull = true)]
         protected EditorBeatmap EditorBeatmap { get; private set; }
 
@@ -87,12 +89,37 @@ private void load(OsuColour colours)
                             }
                         }
                     },
-                    CreateSelectionBox(),
+                    SelectionBox = CreateSelectionBox(),
                 }
             };
         }
 
-        public virtual ComposeSelectionBox CreateSelectionBox() => new ComposeSelectionBox();
+        public ComposeSelectionBox CreateSelectionBox()
+            => new ComposeSelectionBox
+            {
+                OperationStarted = OnDragOperationBegan,
+                OperationEnded = OnDragOperationEnded,
+
+                OnRotation = e => HandleRotation(e.Delta.X),
+                OnScaleX = (e, anchor) => HandleScaleX(e.Delta.X, anchor),
+                OnScaleY = (e, anchor) => HandleScaleY(e.Delta.Y, anchor),
+            };
+
+        /// <summary>
+        /// Fired when a drag operation ends from the selection box.
+        /// </summary>
+        protected virtual void OnDragOperationBegan()
+        {
+            ChangeHandler.BeginChange();
+        }
+
+        /// <summary>
+        /// Fired when a drag operation begins from the selection box.
+        /// </summary>
+        protected virtual void OnDragOperationEnded()
+        {
+            ChangeHandler.EndChange();
+        }
 
         #region User Input Handling
 
@@ -108,7 +135,30 @@ private void load(OsuColour colours)
         /// Whether any <see cref="DrawableHitObject"/>s could be moved.
         /// Returning true will also propagate StartTime changes provided by the closest <see cref="IPositionSnapProvider.SnapScreenSpacePositionToValidTime"/>.
         /// </returns>
-        public virtual bool HandleMovement(MoveSelectionEvent moveEvent) => true;
+        public virtual bool HandleMovement(MoveSelectionEvent moveEvent) => false;
+
+        /// <summary>
+        /// Handles the selected <see cref="DrawableHitObject"/>s being rotated.
+        /// </summary>
+        /// <param name="angle">The delta angle to apply to the selection.</param>
+        /// <returns>Whether any <see cref="DrawableHitObject"/>s could be moved.</returns>
+        public virtual bool HandleRotation(float angle) => false;
+
+        /// <summary>
+        /// Handles the selected <see cref="DrawableHitObject"/>s being scaled in a vertical direction.
+        /// </summary>
+        /// <param name="scale">The delta scale to apply.</param>
+        /// <param name="anchor">The point of reference where the scale is originating from.</param>
+        /// <returns>Whether any <see cref="DrawableHitObject"/>s could be moved.</returns>
+        public virtual bool HandleScaleY(in float scale, Anchor anchor) => false;
+
+        /// <summary>
+        /// Handles the selected <see cref="DrawableHitObject"/>s being scaled in a horizontal direction.
+        /// </summary>
+        /// <param name="scale">The delta scale to apply.</param>
+        /// <param name="anchor">The point of reference where the scale is originating from.</param>
+        /// <returns>Whether any <see cref="DrawableHitObject"/>s could be moved.</returns>
+        public virtual bool HandleScaleX(in float scale, Anchor anchor) => false;
 
         public bool OnPressed(PlatformAction action)
         {
@@ -211,11 +261,22 @@ internal void UpdateVisibility()
             selectionDetailsText.Text = count > 0 ? count.ToString() : string.Empty;
 
             if (count > 0)
+            {
                 Show();
+                OnSelectionChanged();
+            }
             else
                 Hide();
         }
 
+        /// <summary>
+        /// Triggered whenever more than one object is selected, on each change.
+        /// Should update the selection box's state to match supported operations.
+        /// </summary>
+        protected virtual void OnSelectionChanged()
+        {
+        }
+
         protected override void Update()
         {
             base.Update();