Handle control point positional updates within SliderPath

osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointVisualiser.cs

@@ -117,14 +117,6 @@ namespace osu.Game.Rulesets.Osu.Edit.Blueprints.Sliders.Components
                 return true;
             }
 
-            // Make control points relative
-            Vector2 first = slider.Path.ControlPoints[0].Position.Value;
-            for (int i = 0; i < slider.Path.ControlPoints.Count; i++)
-                slider.Path.ControlPoints[i].Position.Value = slider.Path.ControlPoints[i].Position.Value - first;
-
-            // The slider's position defines the position of the first control point, and all further control points are relative to that point
-            slider.Position += first;
-
             // Since pieces are re-used, they will not point to the deleted control points while remaining selected
             foreach (var piece in Pieces)
                 piece.IsSelected.Value = false;

osu.Game.Rulesets.Osu/Objects/Slider.cs

@@ -100,6 +100,8 @@ namespace osu.Game.Rulesets.Osu.Objects
         {
             SamplesBindable.ItemsAdded += _ => updateNestedSamples();
             SamplesBindable.ItemsRemoved += _ => updateNestedSamples();
+
+            Path.OffsetChanged += offset => Position += offset;
         }
 
         protected override void ApplyDefaultsToSelf(ControlPointInfo controlPointInfo, BeatmapDifficulty difficulty)

osu.Game/Rulesets/Objects/SliderPath.cs

@@ -16,6 +16,12 @@ namespace osu.Game.Rulesets.Objects
 {
     public class SliderPath
     {
+        /// <summary>
+        /// Invoked when the offset of the path changes.
+        /// The provided value indicates the offset, and should be used to re-calculate the position of the containing drawable.
+        /// </summary>
+        public event Action<Vector2> OffsetChanged;
+
         /// <summary>
         /// The current version of this <see cref="SliderPath"/>. Updated when any change to the path occurs.
         /// </summary>
@@ -62,6 +68,20 @@ namespace osu.Game.Rulesets.Objects
                 foreach (var c in items)
                     c.Changed -= invalidate;
 
+                // Make all control points relative to the first one
+                if (ControlPoints.Count > 0)
+                {
+                    Vector2 first = ControlPoints[0].Position.Value;
+
+                    if (first != Vector2.Zero)
+                    {
+                        foreach (var c in ControlPoints)
+                            c.Position.Value -= first;
+
+                        OffsetChanged?.Invoke(first);
+                    }
+                }
+
                 invalidate();
             };
         }