Add support for double tap action from Apple Pencil 2

lib/ui/platform_dispatcher.dart

@@ -371,7 +371,7 @@ class PlatformDispatcher {
   //  * pointer_data.cc
   //  * pointer.dart
   //  * AndroidTouchProcessor.java
-  static const int _kPointerDataFieldCount = 35;
+  static const int _kPointerDataFieldCount = 36;
 
   static PointerDataPacket _unpackPointerDataPacket(ByteData packet) {
     const int kStride = Int64List.bytesPerElement;
@@ -417,6 +417,7 @@ class PlatformDispatcher {
         panDeltaY: packet.getFloat64(kStride * offset++, _kFakeHostEndian),
         scale: packet.getFloat64(kStride * offset++, _kFakeHostEndian),
         rotation: packet.getFloat64(kStride * offset++, _kFakeHostEndian),
+        preferredAction: PointerPreferredAction.values[packet.getInt64(kStride * offset++, _kFakeHostEndian)],
       ));
       assert(offset == (i + 1) * _kPointerDataFieldCount);
     }

lib/ui/pointer.dart

@@ -133,10 +133,21 @@ enum PointerSignalKind {
   /// A pointer-generated scale event (e.g. trackpad pinch).
   scale,
 
+  /// A stylus generated action (e.g. double tap on Apple Pencil 2)
+  stylusAction,
+
   /// An unknown pointer signal kind.
   unknown
 }
 
+  /// The preferred action for stylus action
+enum PointerPreferredAction {
+  ignore,
+  showColorPalette,
+  switchEraser,
+  switchPrevious
+}
+
 /// Information about the state of a pointer.
 class PointerData {
   /// Creates an object that represents the state of a pointer.
@@ -176,6 +187,7 @@ class PointerData {
     this.panDeltaY = 0.0,
     this.scale = 0.0,
     this.rotation = 0.0,
+    this.preferredAction = PointerPreferredAction.ignore,
   });
 
   /// Unique identifier that ties the [PointerEvent] to embedder event created it.
@@ -374,6 +386,11 @@ class PointerData {
   /// The current angle of the pan/zoom in radians, with 0.0 as the initial angle.
   final double rotation;
 
+  /// For events with signal kind of stylusAction
+  ///
+  /// The current preferred action for stylusAction, with ignore as the default.
+  final PointerPreferredAction preferredAction;
+
   @override
   String toString() => 'PointerData(x: $physicalX, y: $physicalY)';
 
@@ -414,6 +431,7 @@ class PointerData {
              'panDeltaY: $panDeltaY, '
              'scale: $scale, '
              'rotation: $rotation'
+             'preferredAction: $preferredAction, '
            ')';
   }
 }

lib/ui/window/pointer_data.h

@@ -11,7 +11,7 @@ namespace flutter {
 
 // If this value changes, update the pointer data unpacking code in
 // platform_dispatcher.dart.
-static constexpr int kPointerDataFieldCount = 35;
+static constexpr int kPointerDataFieldCount = 36;
 static constexpr int kBytesPerField = sizeof(int64_t);
 // Must match the button constants in events.dart.
 enum PointerButtonMouse : int64_t {
@@ -63,6 +63,15 @@ struct alignas(8) PointerData {
     kScroll,
     kScrollInertiaCancel,
     kScale,
+    kStylusAction,
+  };
+
+  // Must match the PointerPreferredAction enum in pointer.dart.
+  enum class PreferredAction : int64_t {
+    kIgnore,
+    kShowColorPalette,
+    kSwitchEraser,
+    kSwitchPrevious
   };
 
   int64_t embedder_id;
@@ -100,6 +109,7 @@ struct alignas(8) PointerData {
   double pan_delta_y;
   double scale;
   double rotation;
+  PreferredAction preferred_action;
 
   void Clear();
 };

lib/ui/window/pointer_data_packet_converter.cc

@@ -293,6 +293,7 @@ void PointerDataPacketConverter::ConvertPointerData(
     switch (pointer_data.signal_kind) {
       case PointerData::SignalKind::kScroll:
       case PointerData::SignalKind::kScrollInertiaCancel:
+      case PointerData::SignalKind::kStylusAction:
       case PointerData::SignalKind::kScale: {
         // Makes sure we have an existing pointer
         auto iter = states_.find(pointer_data.device);

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -55,7 +55,9 @@
 // This is left a FlutterBinaryMessenger privately for now to give people a chance to notice the
 // change. Unfortunately unless you have Werror turned on, incompatible pointers as arguments are
 // just a warning.
-@interface FlutterViewController () <FlutterBinaryMessenger, UIScrollViewDelegate>
+@interface FlutterViewController () <FlutterBinaryMessenger,
+                                     UIScrollViewDelegate,
+                                     UIPencilInteractionDelegate>
 @property(nonatomic, readwrite, getter=isDisplayingFlutterUI) BOOL displayingFlutterUI;
 @property(nonatomic, assign) BOOL isHomeIndicatorHidden;
 @property(nonatomic, assign) BOOL isPresentingViewControllerAnimating;
@@ -93,7 +95,7 @@ @interface FlutterViewController () <FlutterBinaryMessenger, UIScrollViewDelegat
 // Trackpad rotating
 @property(nonatomic, retain)
     UIRotationGestureRecognizer* rotationGestureRecognizer API_AVAILABLE(ios(13.4));
-
+@property(nonatomic, retain) UIPencilInteraction* pencilInteraction API_AVAILABLE(ios(13.4));
 /**
  * Creates and registers plugins used by this view controller.
  */
@@ -709,6 +711,10 @@ - (void)viewDidLoad {
   [self createTouchRateCorrectionVSyncClientIfNeeded];
 
   if (@available(iOS 13.4, *)) {
+    _pencilInteraction = [[UIPencilInteraction alloc] init];
+    _pencilInteraction.delegate = self;
+    [_flutterView addInteraction:_pencilInteraction];
+
     _hoverGestureRecognizer =
         [[UIHoverGestureRecognizer alloc] initWithTarget:self action:@selector(hoverEvent:)];
     _hoverGestureRecognizer.delegate = self;
@@ -956,7 +962,7 @@ - (void)goToApplicationLifecycle:(nonnull NSString*)state {
     case UITouchTypeDirect:
     case UITouchTypeIndirect:
       return flutter::PointerData::DeviceKind::kTouch;
-    case UITouchTypeStylus:
+    case UITouchTypePencil:
       return flutter::PointerData::DeviceKind::kStylus;
     case UITouchTypeIndirectPointer:
       return flutter::PointerData::DeviceKind::kMouse;
@@ -1211,6 +1217,40 @@ - (void)invalidateTouchRateCorrectionVSyncClient {
   _touchRateCorrectionVSyncClient = nil;
 }
 
+#pragma mark - Stylus Events
+
+#pragma clang diagnostic push
+
+- (void)pencilInteractionDidTap:(UIPencilInteraction*)interaction API_AVAILABLE(ios(13.4)) {
+  flutter::PointerData pointer_data = [self generatePointerDataAtLastMouseLocation];
+
+  switch (UIPencilInteraction.preferredTapAction) {
+    case UIPencilPreferredActionIgnore:
+      pointer_data.preferred_action = flutter::PointerData::PreferredAction::kIgnore;
+      break;
+    case UIPencilPreferredActionShowColorPalette:
+      pointer_data.preferred_action = flutter::PointerData::PreferredAction::kShowColorPalette;
+      break;
+    case UIPencilPreferredActionSwitchEraser:
+      pointer_data.preferred_action = flutter::PointerData::PreferredAction::kSwitchEraser;
+      break;
+    case UIPencilPreferredActionSwitchPrevious:
+      pointer_data.preferred_action = flutter::PointerData::PreferredAction::kSwitchPrevious;
+    default:
+      break;
+  }
+
+  pointer_data.device = reinterpret_cast<int64_t>(_pencilInteraction);
+  pointer_data.kind = flutter::PointerData::DeviceKind::kStylus;
+  pointer_data.signal_kind = flutter::PointerData::SignalKind::kStylusAction;
+
+  auto packet = std::make_unique<flutter::PointerDataPacket>(1);
+  packet->SetPointerData(/*index=*/0, pointer_data);
+  [_engine.get() dispatchPointerDataPacket:std::move(packet)];
+}
+
+#pragma clang diagnostic pop
+
 #pragma mark - Handle view resizing
 
 - (void)updateViewportMetrics {
@@ -1680,7 +1720,7 @@ - (void)pressesCancelled:(NSSet<UIPress*>*)presses
 
 #pragma mark - Orientation updates
 
-- (void)onOrientationPreferencesUpdated:(NSNotification*)notification {
+- (void)onOrientationPreferencesUpdated:(NSNotification*)notification API_AVAILABLE(ios(12.1)) {
   // Notifications may not be on the iOS UI thread
   dispatch_async(dispatch_get_main_queue(), ^{
     NSDictionary* info = notification.userInfo;

shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm

@@ -121,6 +121,7 @@ - (void)performOrientationUpdate:(UIInterfaceOrientationMask)new_preferences;
 - (void)handlePressEvent:(FlutterUIPressProxy*)press
               nextAction:(void (^)())next API_AVAILABLE(ios(13.4));
 - (void)discreteScrollEvent:(UIPanGestureRecognizer*)recognizer;
+- (void)pencilInteractionDidTap:(UIPencilInteraction*)interaction;
 - (void)updateViewportMetrics;
 - (void)onUserSettingsChanged:(NSNotification*)notification;
 - (void)applicationWillTerminate:(NSNotification*)notification;
@@ -1479,6 +1480,27 @@ - (void)testMouseSupport API_AVAILABLE(ios(13.4)) {
       dispatchPointerDataPacket:std::make_unique<flutter::PointerDataPacket>(0)];
 }
 
+- (void)testPencilSupport API_AVAILABLE(ios(13.4)) {
+  if (@available(iOS 13.4, *)) {
+    // noop
+  } else {
+    return;
+  }
+
+  FlutterViewController* vc = [[FlutterViewController alloc] initWithEngine:self.mockEngine
+                                                                    nibName:nil
+                                                                     bundle:nil];
+  XCTAssertNotNil(vc);
+
+  id mockPencilInteraction = OCMClassMock([UIPencilInteraction class]);
+  XCTAssertNotNil(mockPencilInteraction);
+
+  [vc pencilInteractionDidTap:mockPencilInteraction];
+
+  [[[self.mockEngine verify] ignoringNonObjectArgs]
+      dispatchPointerDataPacket:std::make_unique<flutter::PointerDataPacket>(0)];
+}
+
 - (void)testFakeEventTimeStamp {
   FlutterViewController* vc = [[FlutterViewController alloc] initWithEngine:self.mockEngine
                                                                     nibName:nil

shell/platform/embedder/embedder.cc

@@ -2019,6 +2019,8 @@ inline flutter::PointerData::SignalKind ToPointerDataSignalKind(
       return flutter::PointerData::SignalKind::kScrollInertiaCancel;
     case kFlutterPointerSignalKindScale:
       return flutter::PointerData::SignalKind::kScale;
+    case kFlutterPointerSignalKindStylusAction:
+      return flutter::PointerData::SignalKind::kStylusAction;
   }
   return flutter::PointerData::SignalKind::kNone;
 }

shell/platform/embedder/embedder.h

@@ -888,6 +888,7 @@ typedef enum {
   kFlutterPointerSignalKindScroll,
   kFlutterPointerSignalKindScrollInertiaCancel,
   kFlutterPointerSignalKindScale,
+  kFlutterPointerSignalKindStylusAction,
 } FlutterPointerSignalKind;
 
 typedef struct {