Move a lot of the implementation to base SelectionHandler

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

@@ -43,6 +43,8 @@ namespace osu.Game.Screens.Edit.Compose.Components
 
         private OsuSpriteText selectionDetailsText;
 
+        protected ComposeSelectionBox SelectionBox { get; private set; }
+
         [Resolved(CanBeNull = true)]
         protected EditorBeatmap EditorBeatmap { get; private set; }
 
@@ -87,12 +89,37 @@ namespace osu.Game.Screens.Edit.Compose.Components
                             }
                         }
                     },
-                    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 @@ namespace osu.Game.Screens.Edit.Compose.Components
         /// 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 @@ namespace osu.Game.Screens.Edit.Compose.Components
             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();