Add more IHeadlessWindow methods and update Obsolete message

src/Avalonia.Base/Input/DragEventArgs.cs

@@ -34,7 +34,7 @@ namespace Avalonia.Input
         }
 
         [Unstable]
-        [Obsolete("This constructor may be removed in 12.0. Consider replacing it with RawDragEvent.")]
+        [Obsolete("This constructor might be removed in 12.0. For unit testing, consider using DragDrop.DoDragDrop or IHeadlessWindow.DragDrop.")]
         public DragEventArgs(RoutedEvent<DragEventArgs> routedEvent, IDataObject data, Interactive target, Point targetLocation, KeyModifiers keyModifiers)
             : base(routedEvent)
         {

src/Avalonia.Base/Input/PointerDeltaEventArgs.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Input
         public Vector Delta { get; set; }
 
         [Unstable]
-        [Obsolete("This constructor may be removed in 12.0. Consider replacing it with RawPointerEventArgs or headless unit tests helpers.")]
+        [Obsolete("This constructor might be removed in 12.0.")]
         public PointerDeltaEventArgs(RoutedEvent routedEvent, object? source, 
             IPointer pointer, Visual rootVisual, Point rootVisualPosition, ulong timestamp,
             PointerPointProperties properties, KeyModifiers modifiers, Vector delta) 

src/Avalonia.Base/Input/PointerEventArgs.cs

@@ -15,7 +15,7 @@ namespace Avalonia.Input
         private readonly Lazy<IReadOnlyList<RawPointerPoint>?>? _previousPoints;
 
         [Unstable]
-        [Obsolete("This constructor may be removed in 12.0. Consider replacing it with RawPointerEventArgs or headless unit tests helpers.")]
+        [Obsolete("This constructor might be removed in 12.0. For unit testing, consider using IHeadlessWindow mouse methods.")]
         public PointerEventArgs(RoutedEvent routedEvent,
             object? source,
             IPointer pointer,

src/Avalonia.Base/Input/PointerWheelEventArgs.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Input
         public Vector Delta { get; set; }
 
         [Unstable]
-        [Obsolete("This constructor may be removed in 12.0. Consider replacing it with RawPointerEventArgs or headless unit tests helpers.")]
+        [Obsolete("This constructor might be removed in 12.0. For unit testing, consider using IHeadlessWindow.MouseWheel.")]
         public PointerWheelEventArgs(object source, IPointer pointer, Visual rootVisual,
             Point rootVisualPosition, ulong timestamp,
             PointerPointProperties properties, KeyModifiers modifiers, Vector delta)

src/Avalonia.Headless/HeadlessWindowImpl.cs

@@ -284,6 +284,18 @@ namespace Avalonia.Headless
                 button == 1 ? RawPointerEventType.MiddleButtonUp : RawPointerEventType.RightButtonUp,
                 point, modifiers));
         }
+        
+        void IHeadlessWindow.MouseWheel(Point point, Vector delta, RawInputModifiers modifiers)
+        {
+            Input?.Invoke(new RawMouseWheelEventArgs(MouseDevice, Timestamp, InputRoot,
+                point, delta, modifiers));
+        }
+        
+        void IHeadlessWindow.DragDrop(Point point, RawDragEventType type, IDataObject data, DragDropEffects effects, RawInputModifiers modifiers)
+        {
+            var device = AvaloniaLocator.Current.GetRequiredService<IDragDropDevice>();
+            Input?.Invoke(new RawDragEvent(device, type, InputRoot, point, data, effects, modifiers));
+        }
 
         void IWindowImpl.Move(PixelPoint point)
         {

src/Avalonia.Headless/IHeadlessWindow.cs

@@ -1,4 +1,5 @@
 using Avalonia.Input;
+using Avalonia.Input.Raw;
 using Avalonia.Media.Imaging;
 using Avalonia.Platform;
 using Avalonia.Utilities;
@@ -13,5 +14,7 @@ namespace Avalonia.Headless
         void MouseDown(Point point, int button, RawInputModifiers modifiers = RawInputModifiers.None);
         void MouseMove(Point point, RawInputModifiers modifiers = RawInputModifiers.None);
         void MouseUp(Point point, int button, RawInputModifiers modifiers = RawInputModifiers.None);
+        void MouseWheel(Point point, Vector delta, RawInputModifiers modifiers = RawInputModifiers.None);
+        void DragDrop(Point point, RawDragEventType type, IDataObject data, DragDropEffects effects, RawInputModifiers modifiers);
     }
 }