Add support for mice on iOS 13.4+

shell/platform/darwin/ios/framework/Headers/FlutterViewController.h

@@ -47,8 +47,13 @@ extern NSNotificationName const FlutterSemanticsUpdateNotification;
  * Dart-related state and asynchronous tasks when navigating back and forth between a
  * FlutterViewController and other `UIViewController`s.
  */
+#ifdef __IPHONE_13_4
 FLUTTER_EXPORT
+@interface FlutterViewController
+    : UIViewController <FlutterTextureRegistry, FlutterPluginRegistry, UIPointerInteractionDelegate>
+#else
 @interface FlutterViewController : UIViewController <FlutterTextureRegistry, FlutterPluginRegistry>
+#endif
 
 /**
  * Initializes this FlutterViewController with the specified `FlutterEngine`.

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

@@ -33,6 +33,28 @@
 NSNotificationName const FlutterViewControllerShowHomeIndicator =
     @"FlutterViewControllerShowHomeIndicator";
 
+// Struct holding the mouse state. The engine doesn't keep track of which
+// mouse buttons have been pressed, so it's the embedding's responsibility.
+typedef struct MouseState {
+  // True if the last event sent to Flutter had at least one mouse button.
+  // pressed.
+  bool flutter_state_is_down = false;
+
+  // True if kAdd has been sent to Flutter. Used to determine whether
+  // to send a kAdd event before sending an incoming mouse event, since
+  // Flutter expects pointers to be added before events are sent for them.
+  bool flutter_state_is_added = false;
+
+  // Current coordinate of the mouse cursor
+  CGPoint location = CGPointZero;
+
+  // Last reported translation for an in-flight pan gesture
+  CGPoint last_translation = CGPointZero;
+
+  // The currently pressed buttons, as represented in FlutterPointerEvent.
+  uint64_t buttons = 0;
+} MouseState;
+
 // 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.
@@ -77,6 +99,11 @@ @implementation FlutterViewController {
   // UIScrollView with height zero and a content offset so we can get those events. See also:
   // https://github.com/flutter/flutter/issues/35050
   fml::scoped_nsobject<UIScrollView> _scrollView;
+#ifdef __IPHONE_13_4
+  fml::scoped_nsobject<UIPointerInteraction> _pointerInteraction API_AVAILABLE(ios(13.4));
+  fml::scoped_nsobject<UIPanGestureRecognizer> _panGestureRecognizer API_AVAILABLE(ios(13.4));
+  MouseState _mouseState;
+#endif
 }
 
 @synthesize displayingFlutterUI = _displayingFlutterUI;
@@ -528,6 +555,19 @@ - (void)viewDidLoad {
       << "FlutterViewController's view is loaded but is not attached to a FlutterEngine";
   [_engine.get() attachView];
 
+#ifdef __IPHONE_13_4
+  if (@available(iOS 13.4, *)) {
+    _pointerInteraction.reset([[UIPointerInteraction alloc] initWithDelegate:self]);
+    [self.view addInteraction:_pointerInteraction];
+
+    _panGestureRecognizer.reset(
+        [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(scrollEvent:)]);
+    _panGestureRecognizer.get().allowedScrollTypesMask = UIScrollTypeMaskAll;
+    _panGestureRecognizer.get().allowedTouchTypes = @[ @(UITouchTypeIndirectPointer) ];
+    [_flutterView.get() addGestureRecognizer:_panGestureRecognizer.get()];
+  }
+#endif
+
   [super viewDidLoad];
 }
 
@@ -685,8 +725,9 @@ - (void)goToApplicationLifecycle:(nonnull NSString*)state {
         return flutter::PointerData::DeviceKind::kTouch;
       case UITouchTypeStylus:
         return flutter::PointerData::DeviceKind::kStylus;
+      case UITouchTypeIndirectPointer:
+        return flutter::PointerData::DeviceKind::kMouse;
       default:
-        // TODO(53696): Handle the UITouchTypeIndirectPointer enum value.
         FML_DLOG(INFO) << "Unhandled touch type: " << touch.type;
         break;
     }
@@ -1286,4 +1327,67 @@ - (BOOL)isPresentingViewController {
   return self.presentedViewController != nil || self.isPresentingViewControllerAnimating;
 }
 
+#ifdef __IPHONE_13_4
+- (flutter::PointerData)generatePointerDataForMouse {
+  const CGFloat scale = [UIScreen mainScreen].scale;
+
+  flutter::PointerData pointer_data;
+
+  pointer_data.Clear();
+
+  pointer_data.kind = flutter::PointerData::DeviceKind::kMouse;
+  pointer_data.change = _mouseState.flutter_state_is_added ? flutter::PointerData::Change::kAdd
+                                                           : flutter::PointerData::Change::kHover;
+  pointer_data.pointer_identifier = reinterpret_cast<int64_t>(_pointerInteraction.get());
+
+  pointer_data.physical_x = _mouseState.location.x * scale;
+  pointer_data.physical_y = _mouseState.location.y * scale;
+
+  return pointer_data;
+}
+
+- (UIPointerRegion*)pointerInteraction:(UIPointerInteraction*)interaction
+                      regionForRequest:(UIPointerRegionRequest*)request
+                         defaultRegion:(UIPointerRegion*)defaultRegion API_AVAILABLE(ios(13.4)) {
+  if (request != nil) {
+    auto packet = std::make_unique<flutter::PointerDataPacket>(1);
+    _mouseState.location = request.location;
+
+    flutter::PointerData pointer_data = [self generatePointerDataForMouse];
+
+    pointer_data.signal_kind = flutter::PointerData::SignalKind::kNone;
+    packet->SetPointerData(0, pointer_data);
+
+    [_engine.get() dispatchPointerDataPacket:std::move(packet)];
+  }
+  return nil;
+}
+
+- (void)scrollEvent:(UIPanGestureRecognizer*)recognizer {
+  CGPoint translation = [recognizer translationInView:self.view];
+  const CGFloat scale = [UIScreen mainScreen].scale;
+
+  auto packet = std::make_unique<flutter::PointerDataPacket>(1);
+
+  flutter::PointerData pointer_data = [self generatePointerDataForMouse];
+  pointer_data.signal_kind = flutter::PointerData::SignalKind::kScroll;
+  pointer_data.scroll_delta_x = (translation.x - _mouseState.last_translation.x) * scale;
+  pointer_data.scroll_delta_y = -(translation.y - _mouseState.last_translation.y) * scale;
+
+  // The translation reported by UIPanGestureRecognizer is the total translation
+  // generated by the pan gesture since the gesture began. We need to be able
+  // to keep track of the last translation value in order to generate the deltaX
+  // and deltaY coordinates for each subsequent scroll event.
+  if (recognizer.state != UIGestureRecognizerStateEnded) {
+    _mouseState.last_translation = translation;
+  } else {
+    _mouseState.last_translation = CGPointZero;
+  }
+
+  packet->SetPointerData(0, pointer_data);
+
+  [_engine.get() dispatchPointerDataPacket:std::move(packet)];
+}
+#endif
+
 @end