From e715bff535a3d2431db3a39adff28d33b6793f2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Dach?= <dach.bartlomiej@gmail.com>
Date: Tue, 21 Dec 2021 12:35:48 +0100
Subject: [PATCH] Fix selections including head not correctly dragging if not
 started from head

---
 .../Components/PathControlPointPiece.cs       |  4 ++--
 .../Components/PathControlPointVisualiser.cs  | 22 ++++++++++++-------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointPiece.cs b/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointPiece.cs
index 7b9b6cb976..3db3e85c11 100644
--- a/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointPiece.cs
+++ b/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointPiece.cs
@@ -32,7 +32,7 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
     {
         public Action<PathControlPointPiece, MouseButtonEvent> RequestSelection;
 
-        public Action DragStarted;
+        public Action<PathControlPoint> DragStarted;
         public Action<DragEvent> DragInProgress;
         public Action DragEnded;
 
@@ -188,7 +188,7 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
 
             if (e.Button == MouseButton.Left)
             {
-                DragStarted?.Invoke();
+                DragStarted?.Invoke(ControlPoint);
                 keepSelection = true;
                 return true;
             }
diff --git a/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointVisualiser.cs b/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointVisualiser.cs
index 97775d8122..e06fc1510c 100644
--- a/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointVisualiser.cs
+++ b/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointVisualiser.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics;
 using System.Linq;
 using Humanizer;
 using osu.Framework.Allocation;
@@ -215,13 +216,17 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
 
         private Vector2[] dragStartPositions;
         private PathType?[] dragPathTypes;
-        private HashSet<PathControlPoint> draggedControlPoints;
+        private int draggedControlPointIndex;
+        private HashSet<PathControlPoint> selectedControlPoints;
 
-        private void dragStarted()
+        private void dragStarted(PathControlPoint controlPoint)
         {
             dragStartPositions = slider.Path.ControlPoints.Select(point => point.Position).ToArray();
             dragPathTypes = slider.Path.ControlPoints.Select(point => point.Type).ToArray();
-            draggedControlPoints = new HashSet<PathControlPoint>(Pieces.Where(piece => piece.IsSelected.Value).Select(piece => piece.ControlPoint));
+            draggedControlPointIndex = slider.Path.ControlPoints.IndexOf(controlPoint);
+            selectedControlPoints = new HashSet<PathControlPoint>(Pieces.Where(piece => piece.IsSelected.Value).Select(piece => piece.ControlPoint));
+
+            Debug.Assert(draggedControlPointIndex >= 0);
 
             changeHandler?.BeginChange();
         }
@@ -232,12 +237,13 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
             var oldPosition = slider.Position;
             double oldStartTime = slider.StartTime;
 
-            if (draggedControlPoints.Contains(slider.Path.ControlPoints[0]))
+            if (selectedControlPoints.Contains(slider.Path.ControlPoints[0]))
             {
                 // Special handling for selections containing head control point - the position of the slider changes which means the snapped position and time have to be taken into account
-                var result = snapProvider?.SnapScreenSpacePositionToValidTime(e.ScreenSpaceMousePosition);
+                Vector2 newHeadPosition = Parent.ToScreenSpace(e.MousePosition + (dragStartPositions[0] - dragStartPositions[draggedControlPointIndex]));
+                var result = snapProvider?.SnapScreenSpacePositionToValidTime(newHeadPosition);
 
-                Vector2 movementDelta = Parent.ToLocalSpace(result?.ScreenSpacePosition ?? e.ScreenSpaceMousePosition) - slider.Position;
+                Vector2 movementDelta = Parent.ToLocalSpace(result?.ScreenSpacePosition ?? newHeadPosition) - slider.Position;
 
                 slider.Position += movementDelta;
                 slider.StartTime = result?.Time ?? slider.StartTime;
@@ -249,7 +255,7 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
                     // need to be offset _back_ by the delta corresponding to the movement of the head point.
                     // All other selected control points (if any) will move together with the head point
                     // (and so they will not move at all, relative to each other).
-                    if (!draggedControlPoints.Contains(controlPoint))
+                    if (!selectedControlPoints.Contains(controlPoint))
                         controlPoint.Position -= movementDelta;
                 }
             }
@@ -258,7 +264,7 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
                 for (int i = 0; i < controlPoints.Count; ++i)
                 {
                     var controlPoint = controlPoints[i];
-                    if (draggedControlPoints.Contains(controlPoint))
+                    if (selectedControlPoints.Contains(controlPoint))
                         controlPoint.Position = dragStartPositions[i] + (e.MousePosition - e.MouseDownPosition);
                 }
             }