Add marker IInputs for tablet pen position & touch

These just map to the respective mouse inputs.

osu.Framework/Input/Handlers/Tablet/OpenTabletDriverHandler.cs

@@ -88,11 +88,11 @@ public override bool Initialize(GameHost host)
             return true;
         }
 
-        void IAbsolutePointer.SetPosition(System.Numerics.Vector2 pos) => enqueueInput(new MousePositionAbsoluteInput { Position = new Vector2(pos.X, pos.Y) });
+        void IAbsolutePointer.SetPosition(System.Numerics.Vector2 pos) => enqueueInput(new TabletPenPositionAbsoluteInput { Position = new Vector2(pos.X, pos.Y) });
 
-        void IRelativePointer.SetPosition(System.Numerics.Vector2 delta) => enqueueInput(new MousePositionRelativeInput { Delta = new Vector2(delta.X, delta.Y) });
+        void IRelativePointer.SetPosition(System.Numerics.Vector2 delta) => enqueueInput(new TabletPenPositionRelativeInput { Delta = new Vector2(delta.X, delta.Y) });
 
-        void IPressureHandler.SetPressure(float percentage) => enqueueInput(new MouseButtonInput(osuTK.Input.MouseButton.Left, percentage > 0));
+        void IPressureHandler.SetPressure(float percentage) => enqueueInput(new TabletPenTouchInput(percentage > 0));
 
         private void handleTabletsChanged(object? sender, IEnumerable<TabletReference> tablets)
         {

osu.Framework/Input/StateChanges/TabletPenPositionAbsoluteInput.cs

@@ -0,0 +1,7 @@
+// Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+namespace osu.Framework.Input.StateChanges
+{
+    public class TabletPenPositionAbsoluteInput : MousePositionAbsoluteInput;
+}

osu.Framework/Input/StateChanges/TabletPenPositionRelativeInput.cs

@@ -0,0 +1,7 @@
+// Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+namespace osu.Framework.Input.StateChanges
+{
+    public class TabletPenPositionRelativeInput : MousePositionRelativeInput;
+}

osu.Framework/Input/StateChanges/TabletPenTouchInput.cs

@@ -0,0 +1,19 @@
+// Copyright (c) ppy Pty Ltd <[email protected]>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osuTK.Input;
+
+namespace osu.Framework.Input.StateChanges
+{
+    /// <summary>
+    /// Denotes a pen touching or lifting from the tablet surface.
+    /// </summary>
+    /// <remarks>This currently emulates a left mouse press or release.</remarks>
+    public class TabletPenTouchInput : MouseButtonInput
+    {
+        public TabletPenTouchInput(bool isPressed)
+            : base(MouseButton.Left, isPressed)
+        {
+        }
+    }
+}