Revert pen input flow and map pen to touch on mobile platforms

osu.Framework.Tests/Visual/Input/TestSceneTouchInput.cs

@@ -203,8 +203,8 @@ public void TestMouseInputAppliedFromLatestTouch()
 
             AddStep("retrieve receptors", () =>
             {
-                firstReceptor = receptors[(int)TouchSource.Touch1];
-                lastReceptor = receptors[(int)TouchSource.Touch10];
+                firstReceptor = receptors.First();
+                lastReceptor = receptors.Last();
             });
 
             AddStep("activate first", () =>

osu.Framework.Tests/Visual/Input/TestSceneTouchVisualiser.cs

@@ -35,7 +35,7 @@ public TestSceneTouchVisualiser()
 
         public partial class TouchVisualiser : CompositeDrawable
         {
-            private readonly Drawable[] drawableTouches = new Drawable[10];
+            private readonly Drawable[] drawableTouches = new Drawable[TouchState.MAX_TOUCH_COUNT];
 
             public TouchVisualiser()
             {

osu.Framework/Input/Handlers/Pen/PenHandler.cs

@@ -45,22 +45,24 @@ public override bool Initialize(GameHost host)
             return true;
         }
 
-        // iPadOS doesn't support external tablets, so we are sure it's direct Apple Pencil input.
-        // Other platforms support both direct and indirect tablet input, but SDL doesn't provide any information on the current device type.
-        private static readonly TabletPenDeviceType device_type = RuntimeInfo.OS == RuntimeInfo.Platform.iOS ? TabletPenDeviceType.Direct : TabletPenDeviceType.Unknown;
+        // Pen input is not necessarily direct on mobile platforms (specifically Android, where external tablets are supported),
+        // but until users experience issues with this, consider it "direct" for now.
+        private static readonly TabletPenDeviceType device_type = RuntimeInfo.IsMobile ? TabletPenDeviceType.Direct : TabletPenDeviceType.Unknown;
 
-        private void handlePenMove(Vector2 position)
+        private void handlePenMove(Vector2 position, bool pressed)
         {
-            enqueueInput(new MousePositionAbsoluteInputFromPen
-            {
-                Position = position,
-                DeviceType = device_type
-            });
+            if (pressed && device_type == TabletPenDeviceType.Direct)
+                enqueueInput(new TouchInput(new Input.Touch(TouchSource.PenTouch, position), true));
+            else
+                enqueueInput(new MousePositionAbsoluteInputFromPen { DeviceType = device_type, Position = position });
         }
 
-        private void handlePenTouch(bool pressed)
+        private void handlePenTouch(bool pressed, Vector2 position)
         {
-            enqueueInput(new MouseButtonInputFromPen(pressed) { DeviceType = device_type });
+            if (device_type == TabletPenDeviceType.Direct)
+                enqueueInput(new TouchInput(new Input.Touch(TouchSource.PenTouch, position), pressed));
+            else
+                enqueueInput(new MouseButtonInputFromPen(pressed) { DeviceType = device_type });
         }
 
         private void handlePenButton(TabletPenButton button, bool pressed)

osu.Framework/Input/StateChanges/ISourcedFromPen.cs

@@ -6,7 +6,8 @@ namespace osu.Framework.Input.StateChanges
     /// <summary>
     /// Denotes a simulated mouse input that was made by a tablet/pen device.
     /// </summary>
-    public interface ISourcedFromPen : IInput
+    // todo: this is not ready to be used externally for distinguishing input, therefore it's internal for now.
+    internal interface ISourcedFromPen : IInput
     {
         /// <summary>
         /// The type of the tablet or pen device that made this input.

osu.Framework/Input/States/TouchState.cs

@@ -9,10 +9,15 @@ namespace osu.Framework.Input.States
     public class TouchState
     {
         /// <summary>
-        /// The maximum amount of touches this can handle.
+        /// The maximum number of touches this can handle.
         /// </summary>
         public static readonly int MAX_TOUCH_COUNT = Enum.GetValues<TouchSource>().Length;
 
+        /// <summary>
+        /// The maximum number of touches this can handle excluding the synthetic source <see cref="TouchSource.PenTouch"/>.
+        /// </summary>
+        internal static readonly int MAX_NATIVE_TOUCH_COUNT = 10;
+
         /// <summary>
         /// The list of currently active touch sources.
         /// </summary>

osu.Framework/Input/TouchSource.cs

@@ -57,5 +57,10 @@ public enum TouchSource
         /// The tenth and last available touch source.
         /// </summary>
         Touch10,
+
+        /// <summary>
+        /// A touch source that represents a pen/stylus.
+        /// </summary>
+        PenTouch,
     }
 }

osu.Framework/Platform/SDL2/SDL2Window_Input.cs

@@ -207,7 +207,7 @@ private void handleDropEvent(SDL_DropEvent evtDrop)
             }
         }
 
-        private readonly long?[] activeTouches = new long?[TouchState.MAX_TOUCH_COUNT];
+        private readonly long?[] activeTouches = new long?[TouchState.MAX_NATIVE_TOUCH_COUNT];
 
         private TouchSource? getTouchSource(long fingerId)
         {
@@ -230,7 +230,7 @@ private void handleDropEvent(SDL_DropEvent evtDrop)
                 return (TouchSource)i;
             }
 
-            // we only handle up to TouchState.MAX_TOUCH_COUNT. Ignore any further touches for now.
+            // we only handle up to TouchState.MAX_NATIVE_TOUCH_COUNT. Ignore any further touches for now.
             return null;
         }
 

osu.Framework/Platform/SDL3/SDL3Window_Input.cs

@@ -247,7 +247,7 @@ private void handleDropEvent(SDL_DropEvent evtDrop)
             }
         }
 
-        private readonly SDL_FingerID?[] activeTouches = new SDL_FingerID?[TouchState.MAX_TOUCH_COUNT];
+        private readonly SDL_FingerID?[] activeTouches = new SDL_FingerID?[TouchState.MAX_NATIVE_TOUCH_COUNT];
 
         private TouchSource? getTouchSource(SDL_FingerID fingerId)
         {
@@ -270,7 +270,7 @@ private void handleDropEvent(SDL_DropEvent evtDrop)
                 return (TouchSource)i;
             }
 
-            // we only handle up to TouchState.MAX_TOUCH_COUNT. Ignore any further touches for now.
+            // we only handle up to TouchState.MAX_NATIVE_TOUCH_COUNT. Ignore any further touches for now.
             return null;
         }
 
@@ -532,12 +532,12 @@ private void handleKeyboardEvent(SDL_KeyboardEvent evtKey)
 
         private void handlePenMotionEvent(SDL_PenMotionEvent evtPenMotion)
         {
-            PenMove?.Invoke(new Vector2(evtPenMotion.x, evtPenMotion.y) * Scale);
+            PenMove?.Invoke(new Vector2(evtPenMotion.x, evtPenMotion.y) * Scale, evtPenMotion.pen_state.HasFlagFast(SDL_PenInputFlags.SDL_PEN_INPUT_DOWN));
         }
 
         private void handlePenTouchEvent(SDL_PenTouchEvent evtPenTouch)
         {
-            PenTouch?.Invoke(evtPenTouch.down);
+            PenTouch?.Invoke(evtPenTouch.down, new Vector2(evtPenTouch.x, evtPenTouch.y) * Scale);
         }
 
         /// <summary>
@@ -743,14 +743,15 @@ private void updateConfineMode()
         public event Action<Touch>? TouchUp;
 
         /// <summary>
-        /// Invoked when a pen moves.
+        /// Invoked when a pen moves. Passes pen position and whether the pen is touching the tablet surface.
         /// </summary>
-        public event Action<Vector2>? PenMove;
+        public event Action<Vector2, bool>? PenMove;
 
         /// <summary>
         /// Invoked when a pen touches (<c>true</c>) or lifts (<c>false</c>) from the tablet surface.
+        /// Also passes the current position of the pen.
         /// </summary>
-        public event Action<bool>? PenTouch;
+        public event Action<bool, Vector2>? PenTouch;
 
         /// <summary>
         /// Invoked when a <see cref="TabletPenButton">pen button</see> is pressed (<c>true</c>) or released (<c>false</c>).