Implement proper rotation algorithm for skin editor

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

@@ -1,7 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using System;
 using System.Collections.Generic;
 using System.Linq;
 using osu.Framework.Graphics;
@@ -12,7 +11,7 @@
 using osu.Game.Rulesets.Objects.Types;
 using osu.Game.Rulesets.Osu.Objects;
 using osu.Game.Screens.Edit.Compose.Components;
-using Vector2 = osuTK.Vector2;
+using osuTK;
 
 namespace osu.Game.Rulesets.Osu.Edit
 {
@@ -173,12 +172,12 @@ public override bool HandleRotation(float delta)
 
             foreach (var h in hitObjects)
             {
-                h.Position = rotatePointAroundOrigin(h.Position, referenceOrigin.Value, delta);
+                h.Position = RotatePointAroundOrigin(h.Position, referenceOrigin.Value, delta);
 
                 if (h is IHasPath path)
                 {
                     foreach (var point in path.Path.ControlPoints)
-                        point.Position.Value = rotatePointAroundOrigin(point.Position.Value, Vector2.Zero, delta);
+                        point.Position.Value = RotatePointAroundOrigin(point.Position.Value, Vector2.Zero, delta);
                 }
             }
 
@@ -324,28 +323,5 @@ private Quad getSurroundingQuad(OsuHitObject[] hitObjects) =>
         private OsuHitObject[] selectedMovableObjects => SelectedItems.OfType<OsuHitObject>()
                                                                       .Where(h => !(h is Spinner))
                                                                       .ToArray();
-
-        /// <summary>
-        /// Rotate a point around an arbitrary origin.
-        /// </summary>
-        /// <param name="point">The point.</param>
-        /// <param name="origin">The centre origin to rotate around.</param>
-        /// <param name="angle">The angle to rotate (in degrees).</param>
-        private static Vector2 rotatePointAroundOrigin(Vector2 point, Vector2 origin, float angle)
-        {
-            angle = -angle;
-
-            point.X -= origin.X;
-            point.Y -= origin.Y;
-
-            Vector2 ret;
-            ret.X = point.X * MathF.Cos(MathUtils.DegreesToRadians(angle)) + point.Y * MathF.Sin(MathUtils.DegreesToRadians(angle));
-            ret.Y = point.X * -MathF.Sin(MathUtils.DegreesToRadians(angle)) + point.Y * MathF.Cos(MathUtils.DegreesToRadians(angle));
-
-            ret.X += origin.X;
-            ret.Y += origin.Y;
-
-            return ret;
-        }
     }
 }

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

@@ -14,6 +14,7 @@
 using osu.Framework.Input;
 using osu.Framework.Input.Bindings;
 using osu.Framework.Input.Events;
+using osu.Framework.Utils;
 using osu.Game.Graphics;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Rulesets.Edit;
@@ -353,6 +354,29 @@ protected virtual IEnumerable<MenuItem> GetContextMenuItemsForSelection(IEnumera
 
         #region Helper Methods
 
+        /// <summary>
+        /// Rotate a point around an arbitrary origin.
+        /// </summary>
+        /// <param name="point">The point.</param>
+        /// <param name="origin">The centre origin to rotate around.</param>
+        /// <param name="angle">The angle to rotate (in degrees).</param>
+        protected static Vector2 RotatePointAroundOrigin(Vector2 point, Vector2 origin, float angle)
+        {
+            angle = -angle;
+
+            point.X -= origin.X;
+            point.Y -= origin.Y;
+
+            Vector2 ret;
+            ret.X = point.X * MathF.Cos(MathUtils.DegreesToRadians(angle)) + point.Y * MathF.Sin(MathUtils.DegreesToRadians(angle));
+            ret.Y = point.X * -MathF.Sin(MathUtils.DegreesToRadians(angle)) + point.Y * MathF.Cos(MathUtils.DegreesToRadians(angle));
+
+            ret.X += origin.X;
+            ret.Y += origin.Y;
+
+            return ret;
+        }
+
         /// <summary>
         /// Given a flip direction, a surrounding quad for all selected objects, and a position,
         /// will return the flipped position in screen space coordinates.

osu.Game/Skinning/Editor/SkinSelectionHandler.cs

@@ -18,16 +18,42 @@ namespace osu.Game.Skinning.Editor
 {
     public class SkinSelectionHandler : SelectionHandler<ISkinnableDrawable>
     {
+        private Vector2? referenceOrigin;
+
         [Resolved]
         private SkinEditor skinEditor { get; set; }
 
+        protected override void OnOperationEnded()
+        {
+            base.OnOperationEnded();
+            referenceOrigin = null;
+        }
+
         public override bool HandleRotation(float angle)
         {
-            // TODO: this doesn't correctly account for origin/anchor specs being different in a multi-selection.
-            foreach (var c in SelectedBlueprints)
-                ((Drawable)c.Item).Rotation += angle;
+            if (SelectedBlueprints.Count == 1)
+            {
+                // for single items, rotate around the origin rather than the selection centre.
+                ((Drawable)SelectedBlueprints.First().Item).Rotation += angle;
+            }
+            else
+            {
+                var selectionQuad = GetSurroundingQuad(SelectedBlueprints.SelectMany(b =>
+                    b.Item.ScreenSpaceDrawQuad.GetVertices().ToArray()));
 
-            return base.HandleRotation(angle);
+                referenceOrigin ??= selectionQuad.Centre;
+
+                foreach (var b in SelectedBlueprints)
+                {
+                    var drawableItem = (Drawable)b.Item;
+
+                    drawableItem.Position = drawableItem.Parent.ToLocalSpace(RotatePointAroundOrigin(b.ScreenSpaceSelectionPoint, referenceOrigin.Value, angle)) - drawableItem.AnchorPosition;
+                    drawableItem.Rotation += angle;
+                }
+            }
+
+            // this isn't always the case but let's be lenient for now.
+            return true;
         }
 
         public override bool HandleScale(Vector2 scale, Anchor anchor)