iOS some pointer/keyboard fixes (#15061)

* Fix stylus input state mapping on iOS

* Fix UIKeyboardHidUsage.KeyboardDeleteOrBackspace mapping on iOS, should be mapped to Backspace

* Release iOS pen pointer on PenUp event, fixing IsPrimary state

* Don't limit scroll gestures to single primary input - user should be able to scroll two different scrolls

src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs

@@ -94,8 +94,7 @@ namespace Avalonia.Input.GestureRecognizers
 
         protected override void PointerPressed(PointerPressedEventArgs e)
         {
-            if (e.Pointer.IsPrimary && 
-                (e.Pointer.Type == PointerType.Touch || e.Pointer.Type == PointerType.Pen))
+            if (e.Pointer.Type == PointerType.Touch || e.Pointer.Type == PointerType.Pen)
             {
                 EndGesture();
                 _tracking = e.Pointer;

src/Avalonia.Base/Input/PenDevice.cs

@@ -1,12 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reflection;
 using Avalonia.Input.GestureRecognizers;
 using Avalonia.Input.Raw;
 using Avalonia.Interactivity;
 using Avalonia.Metadata;
-using Avalonia.Platform;
 using Avalonia.VisualTree;
 
 #pragma warning disable CS0618
@@ -20,6 +18,7 @@ namespace Avalonia.Input
     public class PenDevice : IPenDevice, IDisposable
     {
         private readonly Dictionary<long, Pointer> _pointers = new();
+        private readonly bool _releasePointerOnPenUp;
         private int _clickCount;
         private Rect _lastClickRect;
         private ulong _lastClickTime;
@@ -27,6 +26,11 @@ namespace Avalonia.Input
 
         private bool _disposed;
 
+        public PenDevice(bool releasePointerOnPenUp = false)
+        {
+            _releasePointerOnPenUp = releasePointerOnPenUp;
+        }
+
         public void ProcessRawEvent(RawInputEventArgs e)
         {
             if (!e.Handled && e is RawPointerEventArgs margs)
@@ -52,26 +56,35 @@ namespace Avalonia.Input
             var keyModifiers = e.InputModifiers.ToKeyModifiers();
 
             bool shouldReleasePointer = false;
-            switch (e.Type)
+            try
             {
-                case RawPointerEventType.LeaveWindow:
-                    shouldReleasePointer = true;
-                    break;
-                case RawPointerEventType.LeftButtonDown:
-                    e.Handled = PenDown(pointer, e.Timestamp, e.Root, e.Position, props, keyModifiers, e.InputHitTestResult);
-                    break;
-                case RawPointerEventType.LeftButtonUp:
-                    e.Handled = PenUp(pointer, e.Timestamp, e.Root, e.Position, props, keyModifiers, e.InputHitTestResult);
-                    break;
-                case RawPointerEventType.Move:
-                    e.Handled = PenMove(pointer, e.Timestamp, e.Root, e.Position, props, keyModifiers, e.InputHitTestResult, e.IntermediatePoints);
-                    break;
+                switch (e.Type)
+                {
+                    case RawPointerEventType.LeaveWindow:
+                        shouldReleasePointer = true;
+                        break;
+                    case RawPointerEventType.LeftButtonDown:
+                        e.Handled = PenDown(pointer, e.Timestamp, e.Root, e.Position, props, keyModifiers, e.InputHitTestResult);
+                        break;
+                    case RawPointerEventType.LeftButtonUp:
+                        if (_releasePointerOnPenUp)
+                        {
+                            shouldReleasePointer = true;
+                        }
+                        e.Handled = PenUp(pointer, e.Timestamp, e.Root, e.Position, props, keyModifiers, e.InputHitTestResult);
+                        break;
+                    case RawPointerEventType.Move:
+                        e.Handled = PenMove(pointer, e.Timestamp, e.Root, e.Position, props, keyModifiers, e.InputHitTestResult, e.IntermediatePoints);
+                        break;
+                }
             }
-
-            if (shouldReleasePointer)
+            finally
             {
-                pointer.Dispose();
-                _pointers.Remove(e.RawPointerId);
+                if (shouldReleasePointer)
+                {
+                    pointer.Dispose();
+                    _pointers.Remove(e.RawPointerId);
+                }
             }
         }
 

src/iOS/Avalonia.iOS/InputHandler.cs

@@ -17,7 +17,7 @@ internal sealed class InputHandler
     private readonly ITopLevelImpl _tl;
     private readonly TouchDevice _touchDevice = new();
     private readonly MouseDevice _mouseDevice = new();
-    private readonly PenDevice _penDevice = new();
+    private readonly PenDevice _penDevice = new(releasePointerOnPenUp: true);
     private static long _nextTouchPointId = 1;
     private readonly Dictionary<UITouch, long> _knownTouches = new();
 
@@ -68,8 +68,13 @@ internal sealed class InputHandler
                     (TouchDevice, UITouchPhase.Cancelled) => RawPointerEventType.TouchCancel,
                     (TouchDevice, _) => RawPointerEventType.TouchUpdate,
                     
-                    (_, UITouchPhase.Began) => IsRightClick() ? RawPointerEventType.RightButtonDown : RawPointerEventType.LeftButtonDown,
-                    (_, UITouchPhase.Ended or UITouchPhase.Cancelled) => IsRightClick() ? RawPointerEventType.RightButtonUp : RawPointerEventType.RightButtonDown,
+                    (_, UITouchPhase.Began) => IsRightClick()
+                        ? RawPointerEventType.RightButtonDown
+                        : RawPointerEventType.LeftButtonDown,
+                    (_, UITouchPhase.Ended) => IsRightClick()
+                        ? RawPointerEventType.RightButtonUp
+                        : RawPointerEventType.LeftButtonUp,
+                    (_, UITouchPhase.Cancelled) => RawPointerEventType.LeaveWindow,
                     (_, _) => RawPointerEventType.Move,
                 }, ToPointerPoint(t), modifiers, id)
             {
@@ -288,7 +293,8 @@ internal sealed class InputHandler
         [UIKeyboardHidUsage.Keyboard0] = PhysicalKey.Digit0,
         [UIKeyboardHidUsage.KeyboardReturnOrEnter] = PhysicalKey.Enter,
         [UIKeyboardHidUsage.KeyboardEscape] = PhysicalKey.Escape,
-        [UIKeyboardHidUsage.KeyboardDeleteOrBackspace] = PhysicalKey.Delete,
+        // See KeyboardDeleteForward for an actual Delete.
+        [UIKeyboardHidUsage.KeyboardDeleteOrBackspace] = PhysicalKey.Backspace,
         [UIKeyboardHidUsage.KeyboardTab] = PhysicalKey.Tab,
         [UIKeyboardHidUsage.KeyboardSpacebar] = PhysicalKey.Space,
         [UIKeyboardHidUsage.KeyboardHyphen] = PhysicalKey.NumPadSubtract,