Move Shift scrolling to the ScrollPresenter layer

src/Avalonia.Base/Input/MouseDevice.cs

@@ -202,16 +202,9 @@ namespace Avalonia.Input
 
             var source = _pointer.Captured ?? hitTest;
 
-            // KeyModifiers.Shift should scroll in horizontal direction. This does not work on every platform. 
-            // If Shift-Key is pressed and X is close to 0 we swap the Vector.
-            if (inputModifiers == KeyModifiers.Shift && MathUtilities.IsZero(delta.X))
-            {
-                delta = new Vector(delta.Y, delta.X);
-            }
-
             if (source is not null)
             {
-                var e = new PointerWheelEventArgs(source, _pointer, root, p, timestamp, props, inputModifiers, delta, rawDelta);
+                var e = new PointerWheelEventArgs(source, _pointer, root, p, timestamp, props, inputModifiers, delta);
 
                 source?.RaiseEvent(e);
                 return e.Handled;

src/Avalonia.Base/Input/PointerWheelEventArgs.cs

@@ -6,16 +6,14 @@ namespace Avalonia.Input
     public class PointerWheelEventArgs : PointerEventArgs
     {
         public Vector Delta { get; set; }
-        public Vector RawDelta { get; set; }
 
         internal PointerWheelEventArgs(IInteractive source, IPointer pointer, IVisual rootVisual,
             Point rootVisualPosition, ulong timestamp,
-            PointerPointProperties properties, KeyModifiers modifiers, Vector delta, Vector rawDelta)
+            PointerPointProperties properties, KeyModifiers modifiers, Vector delta)
             : base(InputElement.PointerWheelChangedEvent, source, pointer, rootVisual, rootVisualPosition,
                 timestamp, properties, modifiers)
         {
             Delta = delta;
-            RawDelta = rawDelta;
         }
     }
 }

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -5,6 +5,7 @@ using System.Reactive.Disposables;
 using System.Reactive.Linq;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
+using Avalonia.Utilities;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls.Presenters
@@ -440,15 +441,23 @@ namespace Avalonia.Controls.Presenters
             if (Extent.Height > Viewport.Height || Extent.Width > Viewport.Width)
             {
                 var scrollable = Child as ILogicalScrollable;
-                bool isLogical = scrollable?.IsLogicalScrollEnabled == true;
+                var isLogical = scrollable?.IsLogicalScrollEnabled == true;
 
-                double x = Offset.X;
-                double y = Offset.Y;
+                var x = Offset.X;
+                var y = Offset.Y;
+                var delta = e.Delta;
 
+                // KeyModifiers.Shift should scroll in horizontal direction. This does not work on every platform. 
+                // If Shift-Key is pressed and X is close to 0 we swap the Vector.
+                if (e.KeyModifiers == KeyModifiers.Shift && MathUtilities.IsZero(delta.X))
+                {
+                    delta = new Vector(delta.Y, delta.X);
+                }
+                
                 if (Extent.Height > Viewport.Height)
                 {
                     double height = isLogical ? scrollable!.ScrollSize.Height : 50;
-                    y += -e.Delta.Y * height;
+                    y += -delta.Y * height;
                     y = Math.Max(y, 0);
                     y = Math.Min(y, Extent.Height - Viewport.Height);
                 }
@@ -456,7 +465,7 @@ namespace Avalonia.Controls.Presenters
                 if (Extent.Width > Viewport.Width)
                 {
                     double width = isLogical ? scrollable!.ScrollSize.Width : 50;
-                    x += -e.Delta.X * width;
+                    x += -delta.X * width;
                     x = Math.Max(x, 0);
                     x = Math.Min(x, Extent.Width - Viewport.Width);
                 }