fix a PlatformView gesture bug (#84257)

packages/flutter/lib/src/services/platform_views.dart

@@ -540,20 +540,24 @@ class _AndroidMotionEventConverter {
     );
   }
 
-  void handlePointerUpEvent(PointerUpEvent event) {
-    pointerPositions.remove(event.pointer);
-    usedAndroidPointerIds.remove(pointerProperties[event.pointer]!.id);
-    pointerProperties.remove(event.pointer);
+  void _remove(int pointer) {
+    pointerPositions.remove(pointer);
+    usedAndroidPointerIds.remove(pointerProperties[pointer]!.id);
+    pointerProperties.remove(pointer);
     if (pointerProperties.isEmpty) {
       downTimeMillis = null;
     }
   }
 
+  void handlePointerUpEvent(PointerUpEvent event) {
+    _remove(event.pointer);
+  }
+
   void handlePointerCancelEvent(PointerCancelEvent event) {
-    pointerPositions.clear();
-    pointerProperties.clear();
-    usedAndroidPointerIds.clear();
-    downTimeMillis = null;
+    // The pointer cancel event is handled like pointer up. Normally,
+    // the difference is that pointer cancel doesn't perform any action,
+    // but in this case neither up or cancel perform any action.
+    _remove(event.pointer);
   }
 
   AndroidMotionEvent? toAndroidMotionEvent(PointerEvent event) {

packages/flutter/test/rendering/platform_view_test.dart

@@ -4,9 +4,11 @@
 
 import 'dart:ui' as ui;
 
+import 'package:fake_async/fake_async.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import '../services/fake_platform_views.dart';
 import 'rendering_tester.dart';
@@ -98,6 +100,56 @@ void main() {
     });
 
   }, skip: isBrowser); // TODO(yjbanov): fails on Web with obscured stack trace: https://github.com/flutter/flutter/issues/42770
+
+  // Regression test for https://github.com/flutter/flutter/issues/69431
+  test('multi-finger touch test', () {
+    renderer; // Initialize bindings.
+    final FakeAndroidPlatformViewsController viewsController = FakeAndroidPlatformViewsController();
+    viewsController.registerViewType('webview');
+    final AndroidViewController viewController =
+      PlatformViewsService.initAndroidView(id: 0, viewType: 'webview', layoutDirection: TextDirection.rtl);
+    final PlatformViewRenderBox platformViewRenderBox = PlatformViewRenderBox(
+      controller: viewController,
+      hitTestBehavior: PlatformViewHitTestBehavior.opaque,
+      gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>{
+        Factory<VerticalDragGestureRecognizer>(
+          () => VerticalDragGestureRecognizer(),
+        ),
+      },
+    );
+    layout(platformViewRenderBox);
+    pumpFrame(phase: EnginePhase.flushSemantics);
+
+    viewController.pointTransformer = (Offset offset) => platformViewRenderBox.globalToLocal(offset);
+
+    FakeAsync().run((FakeAsync async) {
+      // Put one pointer down.
+      ui.window.onPointerDataPacket!(ui.PointerDataPacket(data: <ui.PointerData>[
+        _pointerData(ui.PointerChange.add, Offset.zero, pointer: 1, kind: PointerDeviceKind.touch),
+        _pointerData(ui.PointerChange.down, const Offset(10, 10), pointer: 1, kind: PointerDeviceKind.touch),
+        _pointerData(ui.PointerChange.remove, const Offset(10, 10), pointer: 1, kind: PointerDeviceKind.touch),
+      ]));
+      async.flushMicrotasks();
+
+      // Put another pointer down and then cancel it.
+      ui.window.onPointerDataPacket!(ui.PointerDataPacket(data: <ui.PointerData>[
+        _pointerData(ui.PointerChange.add, Offset.zero, pointer: 2, kind: PointerDeviceKind.touch),
+        _pointerData(ui.PointerChange.down, const Offset(20, 10), pointer: 2, kind: PointerDeviceKind.touch),
+        _pointerData(ui.PointerChange.cancel, const Offset(20, 10), pointer: 2, kind: PointerDeviceKind.touch),
+      ]));
+      async.flushMicrotasks();
+
+      // The first pointer can still moving without crashing.
+      ui.window.onPointerDataPacket!(ui.PointerDataPacket(data: <ui.PointerData>[
+        _pointerData(ui.PointerChange.add, Offset.zero, pointer: 1, kind: PointerDeviceKind.touch),
+        _pointerData(ui.PointerChange.move, const Offset(10, 10), pointer: 1, kind: PointerDeviceKind.touch),
+        _pointerData(ui.PointerChange.remove, const Offset(10, 10), pointer: 1, kind: PointerDeviceKind.touch),
+      ]));
+      async.flushMicrotasks();
+    });
+
+    // Passes if no crashes.
+  });
 }
 
 ui.PointerData _pointerData(
@@ -105,8 +157,11 @@ ui.PointerData _pointerData(
   Offset logicalPosition, {
   int device = 0,
   PointerDeviceKind kind = PointerDeviceKind.mouse,
+  int pointer = 0,
 }) {
   return ui.PointerData(
+    pointerIdentifier: pointer,
+    embedderId: pointer,
     change: change,
     physicalX: logicalPosition.dx * ui.window.devicePixelRatio,
     physicalY: logicalPosition.dy * ui.window.devicePixelRatio,