Map pen to touch input when touching the screen

Author: frenzibyte

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

@@ -31,13 +31,11 @@ public override bool Initialize(GameHost host)
                 if (enabled.NewValue)
                 {
                     window.PenMove += handlePenMove;
-                    window.PenTouch += handlePenTouch;
                     window.PenButton += handlePenButton;
                 }
                 else
                 {
                     window.PenMove -= handlePenMove;
-                    window.PenTouch -= handlePenTouch;
                     window.PenButton -= handlePenButton;
                 }
             }, true);
@@ -58,11 +56,6 @@ private void handlePenMove(Vector2 position)
             });
         }
 
-        private void handlePenTouch(bool pressed)
-        {
-            enqueueInput(new MouseButtonInputFromPen(pressed) { DeviceType = device_type });
-        }
-
         private void handlePenButton(TabletPenButton button, bool pressed)
         {
             enqueueInput(new TabletPenButtonInput(button, pressed));

osu.Framework/Input/States/TouchState.cs

@@ -9,9 +9,14 @@ namespace osu.Framework.Input.States
     public class TouchState
     {
         /// <summary>
-        /// The maximum amount of touches this can handle.
+        /// The maximum amount of touches this can handle (excluding <see cref="TouchSource.PenTouch"/>).
         /// </summary>
-        public static readonly int MAX_TOUCH_COUNT = Enum.GetValues<TouchSource>().Length;
+        public static readonly int MAX_TOUCH_COUNT = 10;
+
+        /// <summary>
+        /// The maximum number of <see cref="TouchSource"/>s.
+        /// </summary>
+        public static readonly int MAX_SOURCES_COUNT = Enum.GetValues<TouchSource>().Length;
 
         /// <summary>
         /// The list of currently active touch sources.
@@ -25,7 +30,7 @@ public class TouchState
         /// Using <see cref="GetTouchPosition"/> is recommended for retrieving
         /// logically correct values, as this may contain already stale values.
         /// </remarks>
-        public readonly Vector2[] TouchPositions = new Vector2[MAX_TOUCH_COUNT];
+        public readonly Vector2[] TouchPositions = new Vector2[MAX_SOURCES_COUNT];
 
         /// <summary>
         /// Retrieves the current touch position of a specified <paramref name="source"/>.

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/SDL3/SDL3Window_Input.cs

@@ -524,14 +524,29 @@ private void handleKeyboardEvent(SDL_KeyboardEvent evtKey)
 
         private void handleKeymapChangedEvent() => KeymapChanged?.Invoke();
 
+        // pen input events should ultimately have its own input flow with code from InputManager to fall back to mouse input,
+        // but as the current structure of InputManager completely disallows that, synthesize touch input on pen events
+        // so it still works correctly for our use case (consider OsuTouchInputMapper in osu!).
+
         private void handlePenMotionEvent(SDL_PenMotionEvent evtPenMotion)
         {
-            PenMove?.Invoke(new Vector2(evtPenMotion.x, evtPenMotion.y) * Scale);
+            var pos = new Vector2(evtPenMotion.x, evtPenMotion.y) * Scale;
+
+            if (evtPenMotion.pen_state.HasFlagFast(SDL_PenInputFlags.SDL_PEN_INPUT_DOWN))
+                TouchDown?.Invoke(new Touch(TouchSource.PenTouch, pos));
+            else
+                PenMove?.Invoke(pos);
         }
 
         private void handlePenTouchEvent(SDL_PenTouchEvent evtPenTouch)
         {
-            PenTouch?.Invoke(evtPenTouch.down);
+            var pos = new Vector2(evtPenTouch.x, evtPenTouch.y) * Scale;
+            var touch = new Touch(TouchSource.PenTouch, pos);
+
+            if (evtPenTouch.down)
+                TouchDown?.Invoke(touch);
+            else
+                TouchUp?.Invoke(touch);
         }
 
         /// <summary>
@@ -741,11 +756,6 @@ private void updateConfineMode()
         /// </summary>
         public event Action<Vector2>? PenMove;
 
-        /// <summary>
-        /// Invoked when a pen touches (<c>true</c>) or lifts (<c>false</c>) from the tablet surface.
-        /// </summary>
-        public event Action<bool>? PenTouch;
-
         /// <summary>
         /// Invoked when a <see cref="TabletPenButton">pen button</see> is pressed (<c>true</c>) or released (<c>false</c>).
         /// </summary>