[Web] Synthesize key events for modifier keys on pointer events.

lib/web_ui/lib/src/engine/embedder.dart

@@ -323,8 +323,8 @@ class FlutterViewEmbedder {
       _sceneHostElement!.style.opacity = '0.3';
     }
 
-    PointerBinding.initInstance(glassPaneElement);
     KeyboardBinding.initInstance();
+    PointerBinding.initInstance(glassPaneElement, KeyboardBinding.instance!.converter);
 
     if (domWindow.visualViewport == null && isWebKit) {
       // Older Safari versions sometimes give us bogus innerWidth/innerHeight

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

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:meta/meta.dart';
 import 'package:ui/ui.dart' as ui;
 
 import '../engine.dart'  show registerHotRestartListener;
@@ -30,6 +31,16 @@ final int _kLogicalShiftLeft = kWebLogicalLocationMap['Shift']![_kLocationLeft]!
 final int _kLogicalShiftRight = kWebLogicalLocationMap['Shift']![_kLocationRight]!;
 final int _kLogicalMetaLeft = kWebLogicalLocationMap['Meta']![_kLocationLeft]!;
 final int _kLogicalMetaRight = kWebLogicalLocationMap['Meta']![_kLocationRight]!;
+
+final int _kPhysicalAltLeft = kWebToPhysicalKey['AltLeft']!;
+final int _kPhysicalAltRight = kWebToPhysicalKey['AltRight']!;
+final int _kPhysicalControlLeft = kWebToPhysicalKey['ControlLeft']!;
+final int _kPhysicalControlRight = kWebToPhysicalKey['ControlRight']!;
+final int _kPhysicalShiftLeft = kWebToPhysicalKey['ShiftLeft']!;
+final int _kPhysicalShiftRight = kWebToPhysicalKey['ShiftRight']!;
+final int _kPhysicalMetaLeft = kWebToPhysicalKey['MetaLeft']!;
+final int _kPhysicalMetaRight = kWebToPhysicalKey['MetaRight']!;
+
 // Map logical keys for modifier keys to the functions that can get their
 // modifier flag out of an event.
 final Map<int, _ModifierGetter> _kLogicalKeyToModifierGetter = <int, _ModifierGetter>{
@@ -106,6 +117,7 @@ class KeyboardBinding {
     }
   }
 
+  KeyboardConverter get converter => _converter;
   late final KeyboardConverter _converter;
   final Map<String, DomEventListener> _listeners = <String, DomEventListener>{};
 
@@ -559,4 +571,107 @@ class KeyboardConverter {
       _dispatchKeyData = null;
     }
   }
+
+  // Synthesize modifier keys up or down events only when the known pressing states are different.
+  void synthesizeModifiersIfNeeded(
+    bool altPressed,
+    bool controlPressed,
+    bool metaPressed,
+    bool shiftPressed,
+    num eventTimestamp,
+  ) {
+    _synthesizeModifierIfNeeded(
+      _kPhysicalAltLeft,
+      _kPhysicalAltRight,
+      _kLogicalAltLeft,
+      _kLogicalAltRight,
+      altPressed ? ui.KeyEventType.down : ui.KeyEventType.up,
+      eventTimestamp,
+    );
+    _synthesizeModifierIfNeeded(
+      _kPhysicalControlLeft,
+      _kPhysicalControlRight,
+      _kLogicalControlLeft,
+      _kLogicalControlRight,
+      controlPressed ? ui.KeyEventType.down : ui.KeyEventType.up,
+      eventTimestamp,
+    );
+    _synthesizeModifierIfNeeded(
+      _kPhysicalMetaLeft,
+      _kPhysicalMetaRight,
+      _kLogicalMetaLeft,
+      _kLogicalMetaRight,
+      metaPressed ? ui.KeyEventType.down : ui.KeyEventType.up,
+      eventTimestamp,
+    );
+    _synthesizeModifierIfNeeded(
+      _kPhysicalShiftLeft,
+      _kPhysicalShiftRight,
+      _kLogicalShiftLeft,
+      _kLogicalShiftRight,
+      shiftPressed ? ui.KeyEventType.down : ui.KeyEventType.up,
+      eventTimestamp,
+    );
+  }
+
+  void _synthesizeModifierIfNeeded(
+    int physicalLeft,
+    int physicalRight,
+    int logicalLeft,
+    int logicalRight,
+    ui.KeyEventType type,
+    num domTimestamp,
+  ) {
+    final bool leftPressed = _pressingRecords.containsKey(physicalLeft);
+    final bool rightPressed = _pressingRecords.containsKey(physicalRight);
+    final bool alreadyPressed = leftPressed || rightPressed;
+    final bool synthesizeDown = type == ui.KeyEventType.down && !alreadyPressed;
+    final bool synthesizeUp = type == ui.KeyEventType.up && alreadyPressed;
+
+    // Synthesize a down event only for the left key if right and left are not pressed
+    if (synthesizeDown) {
+      _synthesizeKeyDownEvent(domTimestamp, physicalLeft, logicalLeft);
+    }
+
+    // Synthesize an up event for left key if pressed
+    if (synthesizeUp && leftPressed) {
+      _synthesizeKeyUpEvent(domTimestamp, physicalLeft, logicalLeft);
+    }
+
+    // Synthesize an up event for right key if pressed
+    if (synthesizeUp && rightPressed) {
+      _synthesizeKeyUpEvent(domTimestamp, physicalRight, logicalRight);
+    }
+  }
+
+  void _synthesizeKeyDownEvent(num domTimestamp, int physical, int logical) {
+    performDispatchKeyData(ui.KeyData(
+      timeStamp: _eventTimeStampToDuration(domTimestamp),
+      type: ui.KeyEventType.down,
+      physical: physical,
+      logical: logical,
+      character: null,
+      synthesized: true,
+    ));
+    // Update pressing state
+    _pressingRecords[physical] = logical;
+  }
+
+  void _synthesizeKeyUpEvent(num domTimestamp, int physical, int logical) {
+    performDispatchKeyData(ui.KeyData(
+      timeStamp: _eventTimeStampToDuration(domTimestamp),
+      type: ui.KeyEventType.up,
+      physical: physical,
+      logical: logical,
+      character: null,
+      synthesized: true,
+    ));
+    // Update pressing states
+    _pressingRecords.remove(physical);
+  }
+
+  @visibleForTesting
+  bool debugKeyIsPressed(int physical) {
+    return _pressingRecords.containsKey(physical);
+  }
 }

lib/web_ui/lib/src/engine/pointer_binding.dart

@@ -5,6 +5,7 @@
 import 'dart:math' as math;
 
 import 'package:meta/meta.dart';
+import 'package:ui/src/engine/keyboard_binding.dart';
 import 'package:ui/ui.dart' as ui;
 
 import '../engine.dart' show registerHotRestartListener;
@@ -73,7 +74,7 @@ class SafariPointerEventWorkaround {
 }
 
 class PointerBinding {
-  PointerBinding(this.glassPaneElement)
+  PointerBinding(this.glassPaneElement, this._keyboardConverter)
     : _pointerDataConverter = PointerDataConverter(),
       _detector = const PointerSupportDetector() {
     if (isIosSafari) {
@@ -86,9 +87,9 @@ class PointerBinding {
   static PointerBinding? get instance => _instance;
   static PointerBinding? _instance;
 
-  static void initInstance(DomElement glassPaneElement) {
+  static void initInstance(DomElement glassPaneElement, KeyboardConverter keyboardConverter) {
     if (_instance == null) {
-      _instance = PointerBinding(glassPaneElement);
+      _instance = PointerBinding(glassPaneElement, keyboardConverter);
       assert(() {
         registerHotRestartListener(_instance!.dispose);
         return true;
@@ -107,6 +108,7 @@ class PointerBinding {
 
   PointerSupportDetector _detector;
   final PointerDataConverter _pointerDataConverter;
+  KeyboardConverter _keyboardConverter;
   late _BaseAdapter _adapter;
 
   /// Should be used in tests to define custom detection of pointer support.
@@ -137,15 +139,23 @@ class PointerBinding {
     }
   }
 
+  @visibleForTesting
+  void debugOverrideKeyboardConverter(KeyboardConverter keyboardConverter) {
+    _keyboardConverter = keyboardConverter;
+    _adapter.clearListeners();
+    _adapter = _createAdapter();
+    _pointerDataConverter.clearPointerState();
+  }
+
   _BaseAdapter _createAdapter() {
     if (_detector.hasPointerEvents) {
-      return _PointerAdapter(_onPointerData, glassPaneElement, _pointerDataConverter);
+      return _PointerAdapter(_onPointerData, glassPaneElement, _pointerDataConverter, _keyboardConverter);
     }
     if (_detector.hasTouchEvents) {
-      return _TouchAdapter(_onPointerData, glassPaneElement, _pointerDataConverter);
+      return _TouchAdapter(_onPointerData, glassPaneElement, _pointerDataConverter, _keyboardConverter);
     }
     if (_detector.hasMouseEvents) {
-      return _MouseAdapter(_onPointerData, glassPaneElement, _pointerDataConverter);
+      return _MouseAdapter(_onPointerData, glassPaneElement, _pointerDataConverter, _keyboardConverter);
     }
     throw UnsupportedError('This browser does not support pointer, touch, or mouse events.');
   }
@@ -239,14 +249,20 @@ class _Listener {
 
 /// Common functionality that's shared among adapters.
 abstract class _BaseAdapter {
-  _BaseAdapter(this._callback, this.glassPaneElement, this._pointerDataConverter) {
+  _BaseAdapter(
+    this._callback,
+    this.glassPaneElement,
+    this._pointerDataConverter,
+    this._keyboardConverter,
+  ) {
     setup();
   }
 
   final List<_Listener> _listeners = <_Listener>[];
   final DomElement glassPaneElement;
   final _PointerDataCallback _callback;
   final PointerDataConverter _pointerDataConverter;
+  final KeyboardConverter _keyboardConverter;
 
   /// Each subclass is expected to override this method to attach its own event
   /// listeners and convert events into pointer events.
@@ -570,7 +586,8 @@ class _PointerAdapter extends _BaseAdapter with _WheelEventListenerMixin {
   _PointerAdapter(
     super.callback,
     super.glassPaneElement,
-    super.pointerDataConverter
+    super.pointerDataConverter,
+    super.keyboardConverter,
   );
 
   final Map<int, _ButtonSanitizer> _sanitizers = <int, _ButtonSanitizer>{};
@@ -602,13 +619,27 @@ class _PointerAdapter extends _BaseAdapter with _WheelEventListenerMixin {
     String eventName,
     _PointerEventListener handler, {
     bool useCapture = true,
+    bool checkModifiers = true,
   }) {
     addEventListener(target, eventName, (DomEvent event) {
       final DomPointerEvent pointerEvent = event as DomPointerEvent;
+      if (checkModifiers) {
+        _checkModifiersState(event);
+      }
       handler(pointerEvent);
     }, useCapture: useCapture);
   }
 
+  void _checkModifiersState(DomPointerEvent event) {
+    _keyboardConverter.synthesizeModifiersIfNeeded(
+      event.getModifierState('Alt'),
+      event.getModifierState('Control'),
+      event.getModifierState('Meta'),
+      event.getModifierState('Shift'),
+      event.timeStamp!,
+    );
+  }
+
   @override
   void setup() {
     _addPointerEventListener(glassPaneElement, 'pointerdown', (DomPointerEvent event) {
@@ -654,7 +685,7 @@ class _PointerAdapter extends _BaseAdapter with _WheelEventListenerMixin {
         _convertEventsToPointerData(data: pointerData, event: event, details: details);
         _callback(pointerData);
       }
-    }, useCapture: false);
+    }, useCapture: false, checkModifiers: false);
 
     _addPointerEventListener(domWindow, 'pointerup', (DomPointerEvent event) {
       final int device = _getPointerId(event);
@@ -680,7 +711,7 @@ class _PointerAdapter extends _BaseAdapter with _WheelEventListenerMixin {
         _convertEventsToPointerData(data: pointerData, event: event, details: details);
         _callback(pointerData);
       }
-    });
+    }, checkModifiers: false);
 
     _addWheelEventListener((DomEvent event) {
       _handleWheelEvent(event);
@@ -767,21 +798,35 @@ class _TouchAdapter extends _BaseAdapter {
   _TouchAdapter(
     super.callback,
     super.glassPaneElement,
-    super.pointerDataConverter
+    super.pointerDataConverter,
+    super.keyboardConverter,
   );
 
   final Set<int> _pressedTouches = <int>{};
   bool _isTouchPressed(int identifier) => _pressedTouches.contains(identifier);
   void _pressTouch(int identifier) { _pressedTouches.add(identifier); }
   void _unpressTouch(int identifier) { _pressedTouches.remove(identifier); }
 
-  void _addTouchEventListener(DomEventTarget target, String eventName, _TouchEventListener handler) {
+  void _addTouchEventListener(DomEventTarget target, String eventName, _TouchEventListener handler, {bool checkModifiers = true,}) {
     addEventListener(target, eventName, (DomEvent event) {
       final DomTouchEvent touchEvent = event as DomTouchEvent;
+      if (checkModifiers) {
+        _checkModifiersState(event);
+      }
       handler(touchEvent);
     });
   }
 
+  void _checkModifiersState(DomTouchEvent event) {
+    _keyboardConverter.synthesizeModifiersIfNeeded(
+      event.altKey,
+      event.ctrlKey,
+      event.metaKey,
+      event.shiftKey,
+      event.timeStamp!,
+    );
+  }
+
   @override
   void setup() {
     _addTouchEventListener(glassPaneElement, 'touchstart', (DomTouchEvent event) {
@@ -910,7 +955,8 @@ class _MouseAdapter extends _BaseAdapter with _WheelEventListenerMixin {
   _MouseAdapter(
     super.callback,
     super.glassPaneElement,
-    super.pointerDataConverter
+    super.pointerDataConverter,
+    super.keyboardConverter,
   );
 
   final _ButtonSanitizer _sanitizer = _ButtonSanitizer();
@@ -920,13 +966,27 @@ class _MouseAdapter extends _BaseAdapter with _WheelEventListenerMixin {
     String eventName,
     _MouseEventListener handler, {
     bool useCapture = true,
+    bool checkModifiers = true,
   }) {
     addEventListener(target, eventName, (DomEvent event) {
       final DomMouseEvent mouseEvent = event as DomMouseEvent;
+      if (checkModifiers) {
+        _checkModifiersState(event);
+      }
       handler(mouseEvent);
     }, useCapture: useCapture);
   }
 
+  void _checkModifiersState(DomMouseEvent event) {
+    _keyboardConverter.synthesizeModifiersIfNeeded(
+      event.getModifierState('Alt'),
+      event.getModifierState('Control'),
+      event.getModifierState('Meta'),
+      event.getModifierState('Shift'),
+      event.timeStamp!,
+    );
+  }
+
   @override
   void setup() {
     _addMouseEventListener(glassPaneElement, 'mousedown', (DomMouseEvent event) {