[web] Ensure handled key event is not propagated to IME (flutter/engine#46829)

Fixes [136460](https://github.com/flutter/flutter/issues/136460)

Changes:
- Raw keyboard event is handled during capture phase. This is to ensure
that the framework processes the event before reaching to IME text area
and raw keyboard can stop the propagation for handled events.
- `RawKeyboard` event handler is invoked from `KeyboardBinding` event
handler. This is to prevent race condition because both handlers now run
in capture phase and `KeyboardBinding` needs to process the event first.

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link to the migration guide as per the [breaking change policy].*

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responsibilities.
- [x] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
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- [x] All existing and new tests are passing.

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engine/src/flutter/lib/web_ui/lib/src/engine/keyboard_binding.dart

@@ -13,6 +13,7 @@ import 'browser_detection.dart';
 import 'dom.dart';
 import 'key_map.g.dart';
 import 'platform_dispatcher.dart';
+import 'raw_keyboard.dart';
 import 'semantics.dart';
 
 typedef _VoidCallback = void Function();
@@ -104,9 +105,12 @@ class KeyboardBinding {
     _addEventListener('keydown', (DomEvent domEvent) {
       final FlutterHtmlKeyboardEvent event = FlutterHtmlKeyboardEvent(domEvent as DomKeyboardEvent);
       _converter.handleEvent(event);
+      RawKeyboard.instance?.handleHtmlEvent(domEvent);
     });
-    _addEventListener('keyup', (DomEvent event) {
-      _converter.handleEvent(FlutterHtmlKeyboardEvent(event as DomKeyboardEvent));
+    _addEventListener('keyup', (DomEvent domEvent) {
+      final FlutterHtmlKeyboardEvent event = FlutterHtmlKeyboardEvent(domEvent as DomKeyboardEvent);
+      _converter.handleEvent(event);
+      RawKeyboard.instance?.handleHtmlEvent(domEvent);
     });
   }
 
@@ -209,6 +213,7 @@ class FlutterHtmlKeyboardEvent {
 
   bool getModifierState(String key) => _event.getModifierState(key);
   void preventDefault() => _event.preventDefault();
+  void stopPropagation() => _event.stopPropagation();
   bool get defaultPrevented => _event.defaultPrevented;
 }
 

engine/src/flutter/lib/web_ui/lib/src/engine/raw_keyboard.dart

@@ -15,15 +15,6 @@ import 'services.dart';
 /// Provides keyboard bindings, such as the `flutter/keyevent` channel.
 class RawKeyboard {
   RawKeyboard._(this._onMacOs) {
-    _keydownListener = createDomEventListener((DomEvent event) {
-      _handleHtmlEvent(event);
-    });
-    domWindow.addEventListener('keydown', _keydownListener);
-
-    _keyupListener = createDomEventListener((DomEvent event) {
-      _handleHtmlEvent(event);
-    });
-    domWindow.addEventListener('keyup', _keyupListener);
     registerHotRestartListener(() {
       dispose();
     });
@@ -34,6 +25,9 @@ class RawKeyboard {
   /// Use the [instance] getter to get the singleton after calling this method.
   static void initialize({bool onMacOs = false}) {
     _instance ??= RawKeyboard._(onMacOs);
+    // KeyboardBinding is responsible for forwarding the keyboard
+    // events to the RawKeyboard handler.
+    KeyboardBinding.initInstance();
   }
 
   /// The [RawKeyboard] singleton.
@@ -46,24 +40,16 @@ class RawKeyboard {
   /// if no repeat events were received.
   final Map<String, Timer> _keydownTimers = <String, Timer>{};
 
-  DomEventListener? _keydownListener;
-  DomEventListener? _keyupListener;
-
   /// Uninitializes the [RawKeyboard] singleton.
   ///
   /// After calling this method this object becomes unusable and [instance]
   /// becomes `null`. Call [initialize] again to initialize a new singleton.
   void dispose() {
-    domWindow.removeEventListener('keydown', _keydownListener);
-    domWindow.removeEventListener('keyup', _keyupListener);
-
     for (final String key in _keydownTimers.keys) {
       _keydownTimers[key]!.cancel();
     }
     _keydownTimers.clear();
 
-    _keydownListener = null;
-    _keyupListener = null;
     _instance = null;
   }
 
@@ -96,7 +82,7 @@ class RawKeyboard {
     return event.type == 'keydown' && event.key == 'Tab' && event.isComposing;
   }
 
-  void _handleHtmlEvent(DomEvent domEvent) {
+  void handleHtmlEvent(DomEvent domEvent) {
     if (!domInstanceOfString(domEvent, 'KeyboardEvent')) {
       return;
     }
@@ -158,6 +144,7 @@ class RawKeyboard {
         if (jsonResponse['handled'] as bool) {
           // If the framework handled it, then don't propagate it any further.
           event.preventDefault();
+          event.stopPropagation();
         }
       },
     );

engine/src/flutter/lib/web_ui/test/common/keyboard_test_common.dart

@@ -22,6 +22,7 @@ class MockKeyboardEvent implements FlutterHtmlKeyboardEvent {
     bool altGrKey = false,
     this.location = 0,
     this.onPreventDefault,
+    this.onStopPropagation,
   }) : modifierState =
         <String>{
           if (altKey) 'Alt',
@@ -84,6 +85,12 @@ class MockKeyboardEvent implements FlutterHtmlKeyboardEvent {
   bool get defaultPrevented => _defaultPrevented;
   bool _defaultPrevented = false;
 
+  @override
+  void stopPropagation() {
+    onStopPropagation?.call();
+  }
+  VoidCallback? onStopPropagation;
+
   static bool get lastDefaultPrevented => _lastEvent?.defaultPrevented ?? false;
   static MockKeyboardEvent? _lastEvent;
 }

engine/src/flutter/lib/web_ui/test/engine/raw_keyboard_test.dart

@@ -52,6 +52,10 @@ void testMain() {
 
       DomKeyboardEvent event;
 
+      // Dispatch a keydown event first so that KeyboardBinding will recognize the keyup event.
+      // and will not set preventDefault on it.
+      event = dispatchKeyboardEvent('keydown', key: 'SomeKey', code: 'SomeCode', keyCode: 1);
+
       event = dispatchKeyboardEvent('keyup', key: 'SomeKey', code: 'SomeCode', keyCode: 1);
 
       expect(event.defaultPrevented, isFalse);

engine/src/flutter/lib/web_ui/test/engine/text_editing_test.dart

@@ -12,12 +12,14 @@ import 'package:test/test.dart';
 import 'package:ui/src/engine.dart' show flutterViewEmbedder;
 import 'package:ui/src/engine/browser_detection.dart';
 import 'package:ui/src/engine/dom.dart';
+import 'package:ui/src/engine/raw_keyboard.dart';
 import 'package:ui/src/engine/services.dart';
 import 'package:ui/src/engine/text_editing/autofill_hint.dart';
 import 'package:ui/src/engine/text_editing/input_type.dart';
 import 'package:ui/src/engine/text_editing/text_editing.dart';
 import 'package:ui/src/engine/util.dart';
 import 'package:ui/src/engine/vector_math.dart';
+import 'package:ui/ui.dart' as ui;
 
 import '../common/spy.dart';
 import '../common/test_initialization.dart';
@@ -370,6 +372,52 @@ Future<void> testMain() async {
       expect(lastInputAction, 'TextInputAction.done');
     });
 
+   test('handling keyboard event prevents triggering input action', () {
+      final ui.PlatformMessageCallback? savedCallback = ui.window.onPlatformMessage;
+
+      bool markTextEventHandled = false;
+      ui.window.onPlatformMessage = (String channel, ByteData? data,
+          ui.PlatformMessageResponseCallback? callback) {
+        final ByteData response = const JSONMessageCodec()
+            .encodeMessage(<String, dynamic>{'handled': markTextEventHandled})!;
+        callback!(response);
+      };
+      RawKeyboard.initialize();
+
+      final InputConfiguration config = InputConfiguration();
+      editingStrategy!.enable(
+        config,
+        onChange: trackEditingState,
+        onAction: trackInputAction,
+      );
+
+      // No input action so far.
+      expect(lastInputAction, isNull);
+
+      markTextEventHandled = true;
+      dispatchKeyboardEvent(
+        editingStrategy!.domElement!,
+        'keydown',
+        keyCode: _kReturnKeyCode,
+      );
+
+      // Input action prevented by platform message callback.
+      expect(lastInputAction, isNull);
+
+      markTextEventHandled = false;
+      dispatchKeyboardEvent(
+        editingStrategy!.domElement!,
+        'keydown',
+        keyCode: _kReturnKeyCode,
+      );
+
+      // Input action received.
+      expect(lastInputAction, 'TextInputAction.done');
+
+      ui.window.onPlatformMessage = savedCallback;
+      RawKeyboard.instance?.dispose();
+    });
+
     test('Triggers input action in multi-line mode', () {
       final InputConfiguration config = InputConfiguration(
         inputType: EngineInputType.multiline,

engine/src/flutter/third_party/web_locale_keymap/lib/web_locale_keymap/locale_keymap.dart

@@ -41,6 +41,9 @@ class LocaleKeymap {
       return eventKeyCode;
     }
     if (result == null) {
+      if ((eventCode ?? '').isEmpty && (eventKey ?? '').isEmpty) {
+        return null;
+      }
       final int? heuristicResult = heuristicMapper(eventCode ?? '', eventKey ?? '');
       if (heuristicResult != null) {
         return heuristicResult;