PointerWheelEventArgs: Adds RawDelta

Delta is flipped if the user holds down Shift while scrolling. RawDelta
preserves the original scroll vector.

src/Avalonia.Base/Input/MouseDevice.cs

@@ -196,6 +196,7 @@ namespace Avalonia.Input
             PointerPointProperties props,
             Vector delta, KeyModifiers inputModifiers, IInputElement? hitTest)
         {
+            var rawDelta = delta;
             device = device ?? throw new ArgumentNullException(nameof(device));
             root = root ?? throw new ArgumentNullException(nameof(root));
 
@@ -210,7 +211,7 @@ namespace Avalonia.Input
 
             if (source is not null)
             {
-                var e = new PointerWheelEventArgs(source, _pointer, root, p, timestamp, props, inputModifiers, delta);
+                var e = new PointerWheelEventArgs(source, _pointer, root, p, timestamp, props, inputModifiers, delta, rawDelta);
 
                 source?.RaiseEvent(e);
                 return e.Handled;

src/Avalonia.Base/Input/PointerWheelEventArgs.cs

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