Character activator (#81807)

packages/flutter/lib/src/widgets/shortcuts.dart

@@ -160,6 +160,8 @@ class KeySet<T extends KeyboardKey> {
 ///
 ///  * [SingleActivator], an implementation that represents a single key combined
 ///    with modifiers (control, shift, alt, meta).
+///  * [CharacterActivator], an implementation that represents key combinations
+///    that result in the specified character, such as question mark.
 ///  * [LogicalKeySet], an implementation that requires one or more
 ///    [LogicalKeyboardKey]s to be pressed at the same time. Prefer
 ///    [SingleActivator] when possible.
@@ -179,7 +181,13 @@ abstract class ShortcutActivator {
   /// [Intent]s are stored in a [Map] and indexed by trigger keys. Subclasses
   /// should make sure that the return value of this method does not change
   /// throughout the lifespan of this object.
-  Iterable<LogicalKeyboardKey> get triggers;
+  ///
+  /// This method might also return null, which means this activator declares
+  /// all keys as the trigger key. All activators whose [triggers] returns null
+  /// will be tested with [accepts] on every event. Since this becomes a
+  /// linear search, and having too many might impact performance, it is
+  /// preferred to return non-null [triggers] whenever possible.
+  Iterable<LogicalKeyboardKey>? get triggers;
 
   /// Whether the triggering `event` and the keyboard `state` at the time of the
   /// event meet required conditions, providing that the event is a triggering
@@ -194,6 +202,9 @@ abstract class ShortcutActivator {
   /// this is only used to query whether [RawKeyboard.keysPressed] contains
   /// a key.
   ///
+  /// Since [ShortcutActivator] accepts all event types, subclasses might want
+  /// to check the event type in [accepts].
+  ///
   /// See also:
   ///
   ///  * [LogicalKeyboardKey.collapseSynonyms], which helps deciding whether a
@@ -323,9 +334,6 @@ class LogicalKeySet extends KeySet<LogicalKeyboardKey> with Diagnosticable
     LogicalKeyboardKey.meta: <LogicalKeyboardKey>[LogicalKeyboardKey.metaLeft, LogicalKeyboardKey.metaRight],
   };
 
-  /// Returns a description of the key set that is short and readable.
-  ///
-  /// Intended to be used in debug mode for logging purposes.
   @override
   String debugDescribeKeys() {
     final List<LogicalKeyboardKey> sortedKeys = keys.toList()..sort(
@@ -387,7 +395,7 @@ class ShortcutMapProperty extends DiagnosticsProperty<Map<ShortcutActivator, Int
 
 /// A shortcut key combination of a single key and modifiers.
 ///
-/// This [ShortcutActivator] implements typical shortcuts such as:
+/// The [SingleActivator] implements typical shortcuts such as:
 ///
 ///  * ArrowLeft
 ///  * Shift + Delete
@@ -412,6 +420,11 @@ class ShortcutMapProperty extends DiagnosticsProperty<Map<ShortcutActivator, Int
 ///  * [SingleActivator]s do not consider modifiers to be a trigger key. For
 ///    example, pressing ControlLeft while holding key X *will not* activate a
 ///    `SingleActivator(LogicalKeyboardKey.keyX, control: true)`.
+///
+/// See also:
+///
+///  * [CharacterActivator], an activator that represents key combinations
+///    that result in the specified character, such as question mark.
 class SingleActivator with Diagnosticable implements ShortcutActivator {
   /// Create an activator of a trigger key and modifiers.
   ///
@@ -474,8 +487,8 @@ class SingleActivator with Diagnosticable implements ShortcutActivator {
     this.meta = false,
   }) : // The enumerated check with `identical` is cumbersome but the only way
        // since const constructors can not call functions such as `==` or
-       // `Set.contains`. Checking with `identical` is sufficient since
-       // `LogicalKeyboardKey` only provides cached values.
+       // `Set.contains`. Checking with `identical` might not work when the
+       // key object is created from ID, but it covers common cases.
        assert(
          !identical(trigger, LogicalKeyboardKey.control) &&
          !identical(trigger, LogicalKeyboardKey.controlLeft) &&
@@ -585,6 +598,110 @@ class SingleActivator with Diagnosticable implements ShortcutActivator {
   }
 }
 
+/// A shortcut combination that is triggered by a key event that produces a
+/// specific character.
+///
+/// Keys often produce different characters when combined with modifiers. For
+/// example, it might be helpful for the user to bring up a help menu by
+/// pressing the question mark ('?'). However, there is no logical key that
+/// directly represents a question mark. Althouh 'Shift+Slash' produces a '?'
+/// character on a US keyboard, its logical key is still considered a Slash key,
+/// and hard-coding 'Shift+Slash' in this situation is unfriendly to other
+/// keyboard layouts.
+///
+/// For example, `CharacterActivator('?')` is triggered when a key combination
+/// results in a question mark, which is 'Shift+Slash' on a US keyboard, but
+/// 'Shift+Comma' on a French keyboard.
+///
+/// {@tool dartpad --template=stateful_widget_scaffold_center}
+/// In the following example, when a key combination results in a question mark,
+/// the counter is increased:
+///
+/// ```dart preamble
+/// class HelpMenuIntent extends Intent {
+///   const HelpMenuIntent();
+/// }
+/// ```
+///
+/// ```dart
+/// @override
+/// Widget build(BuildContext context) {
+///   return Shortcuts(
+///     shortcuts: const <ShortcutActivator, Intent>{
+///       CharacterActivator('?'): HelpMenuIntent(),
+///     },
+///     child: Actions(
+///       actions: <Type, Action<Intent>>{
+///         HelpMenuIntent: CallbackAction<HelpMenuIntent>(
+///           onInvoke: (HelpMenuIntent intent) {
+///             ScaffoldMessenger.of(context).showSnackBar(
+///               const SnackBar(content: Text('Keep calm and carry on!')),
+///             );
+///             return null;
+///           },
+///         ),
+///       },
+///       child: Focus(
+///         autofocus: true,
+///         child: Column(
+///           children: const <Widget>[
+///             Text('Press question mark for help'),
+///           ],
+///         ),
+///       ),
+///     ),
+///   );
+/// }
+/// ```
+/// {@end-tool}
+///
+/// See also:
+///
+///  * [SingleActivator], an activator that represents a single key combined
+///    with modifiers, such as `Ctrl+C`.
+class CharacterActivator with Diagnosticable implements ShortcutActivator {
+  /// Create a [CharacterActivator] from the triggering character.
+  const CharacterActivator(this.character);
+
+  /// The character of the triggering event.
+  ///
+  /// This is typically a single-character string, such as '?' or 'œ', although
+  /// [CharacterActivator] doesn't check the length of [character] or whether it
+  /// can be matched by any key combination at all. It is case-sensitive, since
+  /// the [character] is directly compared by `==` to the character reported by
+  /// the platform.
+  ///
+  /// See also:
+  ///
+  ///  * [RawKeyEvent.character], the character of a key event.
+  final String character;
+
+  @override
+  Iterable<LogicalKeyboardKey>? get triggers => null;
+
+  @override
+  bool accepts(RawKeyEvent event, RawKeyboard state) {
+    return event is RawKeyDownEvent
+        && event.character == character;
+  }
+
+  @override
+  String debugDescribeKeys() {
+    String result = '';
+    assert(() {
+      result = "'$character'";
+      return true;
+    }());
+    return result;
+  }
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(StringProperty('character', character));
+  }
+}
+
 class _ActivatorIntentPair with Diagnosticable {
   const _ActivatorIntentPair(this.activator, this.intent);
   final ShortcutActivator activator;
@@ -639,20 +756,22 @@ class ShortcutManager extends ChangeNotifier with Diagnosticable {
     }
   }
 
-  static Map<LogicalKeyboardKey, List<_ActivatorIntentPair>> _indexShortcuts(Map<ShortcutActivator, Intent> source) {
-    final Map<LogicalKeyboardKey, List<_ActivatorIntentPair>> result = <LogicalKeyboardKey, List<_ActivatorIntentPair>>{};
+  static Map<LogicalKeyboardKey?, List<_ActivatorIntentPair>> _indexShortcuts(Map<ShortcutActivator, Intent> source) {
+    final Map<LogicalKeyboardKey?, List<_ActivatorIntentPair>> result = <LogicalKeyboardKey?, List<_ActivatorIntentPair>>{};
     source.forEach((ShortcutActivator activator, Intent intent) {
-      for (final LogicalKeyboardKey trigger in activator.triggers) {
+      // This intermediate variable is necessary to comply with Dart analyzer.
+      final Iterable<LogicalKeyboardKey?>? nullableTriggers = activator.triggers;
+      for (final LogicalKeyboardKey? trigger in nullableTriggers ?? <LogicalKeyboardKey?>[null]) {
         result.putIfAbsent(trigger, () => <_ActivatorIntentPair>[])
           .add(_ActivatorIntentPair(activator, intent));
       }
     });
     return result;
   }
-  Map<LogicalKeyboardKey, List<_ActivatorIntentPair>> get _indexedShortcuts {
+  Map<LogicalKeyboardKey?, List<_ActivatorIntentPair>> get _indexedShortcuts {
     return _indexedShortcutsCache ??= _indexShortcuts(_shortcuts);
   }
-  Map<LogicalKeyboardKey, List<_ActivatorIntentPair>>? _indexedShortcutsCache;
+  Map<LogicalKeyboardKey?, List<_ActivatorIntentPair>>? _indexedShortcutsCache;
 
   /// Returns the [Intent], if any, that matches the current set of pressed
   /// keys.
@@ -662,9 +781,12 @@ class ShortcutManager extends ChangeNotifier with Diagnosticable {
   /// Defaults to a set derived from [RawKeyboard.keysPressed] if `keysPressed`
   /// is not supplied.
   Intent? _find(RawKeyEvent event, RawKeyboard state) {
-    final List<_ActivatorIntentPair>? candidates = _indexedShortcuts[event.logicalKey];
-    if (candidates == null)
-      return null;
+    final List<_ActivatorIntentPair>? candidatesByKey = _indexedShortcuts[event.logicalKey];
+    final List<_ActivatorIntentPair>? candidatesByNull = _indexedShortcuts[null];
+    final List<_ActivatorIntentPair> candidates = <_ActivatorIntentPair>[
+      if (candidatesByKey != null) ...candidatesByKey,
+      if (candidatesByNull != null) ...candidatesByNull,
+    ];
     for (final _ActivatorIntentPair activatorIntent in candidates) {
       if (activatorIntent.activator.accepts(event, state)) {
         return activatorIntent.intent;

packages/flutter/test/widgets/shortcuts_test.dart

@@ -9,7 +9,7 @@ import 'package:flutter_test/flutter_test.dart';
 
 typedef PostInvokeCallback = void Function({Action<Intent> action, Intent intent, BuildContext? context, ActionDispatcher dispatcher});
 
-class TestAction extends CallbackAction<TestIntent> {
+class TestAction extends CallbackAction<Intent> {
   TestAction({
     required OnInvokeCallback onInvoke,
   })  : assert(onInvoke != null),
@@ -31,10 +31,47 @@ class TestDispatcher extends ActionDispatcher {
   }
 }
 
+/// An activator that accepts down events that has [key] as the logical key.
+///
+/// This class is used only to tests. It is intentionally designed poorly by
+/// returning null in [triggers], and checks [key] in [accepts].
+class DumbLogicalActivator extends ShortcutActivator {
+  const DumbLogicalActivator(this.key);
+
+  final LogicalKeyboardKey key;
+
+  @override
+  Iterable<LogicalKeyboardKey>? get triggers => null;
+
+  @override
+  bool accepts(RawKeyEvent event, RawKeyboard state) {
+    return event is RawKeyDownEvent
+        && event.logicalKey == key;
+  }
+
+  /// Returns a short and readable description of the key combination.
+  ///
+  /// Intended to be used in debug mode for logging purposes. In release mode,
+  /// [debugDescribeKeys] returns an empty string.
+  @override
+  String debugDescribeKeys() {
+    String result = '';
+    assert(() {
+      result = key.keyLabel;
+      return true;
+    }());
+    return result;
+  }
+}
+
 class TestIntent extends Intent {
   const TestIntent();
 }
 
+class TestIntent2 extends Intent {
+  const TestIntent2();
+}
+
 class TestShortcutManager extends ShortcutManager {
   TestShortcutManager(this.keys);
 
@@ -49,7 +86,13 @@ class TestShortcutManager extends ShortcutManager {
   }
 }
 
-Widget activatorTester(ShortcutActivator activator, ValueSetter<Intent> onInvoke) {
+Widget activatorTester(
+  ShortcutActivator activator,
+  ValueSetter<Intent> onInvoke, [
+  ShortcutActivator? activator2,
+  ValueSetter<Intent>? onInvoke2,
+]) {
+  final bool hasSecond = activator2 != null && onInvoke2 != null;
   return Actions(
     key: GlobalKey(),
     actions: <Type, Action<Intent>>{
@@ -57,10 +100,16 @@ Widget activatorTester(ShortcutActivator activator, ValueSetter<Intent> onInvoke
         onInvoke(intent);
         return true;
       }),
+      if (hasSecond)
+        TestIntent2: TestAction(onInvoke: (Intent intent) {
+          onInvoke2(intent);
+        }),
     },
     child: Shortcuts(
       shortcuts: <ShortcutActivator, Intent>{
         activator: const TestIntent(),
+        if (hasSecond)
+          activator2: const TestIntent2(),
       },
       child: const Focus(
         autofocus: true,
@@ -967,5 +1016,65 @@ void main() {
       expect(value, isTrue);
       expect(controller.position.pixels, 0.0);
     });
+
+    testWidgets('Shortcuts support activators that returns null in triggers', (WidgetTester tester) async {
+      int invoked = 0;
+      await tester.pumpWidget(activatorTester(
+        const DumbLogicalActivator(LogicalKeyboardKey.keyC),
+        (Intent intent) { invoked += 1; },
+        const SingleActivator(LogicalKeyboardKey.keyC, control: true),
+        (Intent intent) { invoked += 10; },
+      ));
+      await tester.pump();
+
+      // Press KeyC: Accepted by DumbLogicalActivator
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.keyC);
+      expect(invoked, 1);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.keyC);
+      expect(invoked, 1);
+      invoked = 0;
+
+      // Press ControlLeft + KeyC: Accepted by SingleActivator
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.controlLeft);
+      expect(invoked, 0);
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.keyC);
+      expect(invoked, 10);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.keyC);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.controlLeft);
+      expect(invoked, 10);
+      invoked = 0;
+
+      // Press ControlLeft + ShiftLeft + KeyC: Accepted by DumbLogicalActivator
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.shiftLeft);
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.controlLeft);
+      expect(invoked, 0);
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.keyC);
+      expect(invoked, 1);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.keyC);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.controlLeft);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.shiftLeft);
+      expect(invoked, 1);
+      invoked = 0;
+    });
+  });
+
+  group('CharacterActivator', () {
+    testWidgets('is triggered on events with correct character', (WidgetTester tester) async {
+      int invoked = 0;
+      await tester.pumpWidget(activatorTester(
+        const CharacterActivator('?'),
+        (Intent intent) { invoked += 1; },
+      ));
+      await tester.pump();
+
+      // Press KeyC: Accepted by DumbLogicalActivator
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.shiftLeft);
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.slash, character: '?');
+      expect(invoked, 1);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.slash);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.shiftLeft);
+      expect(invoked, 1);
+      invoked = 0;
+    });
   });
 }

packages/flutter_test/lib/src/controller.dart

@@ -1021,10 +1021,10 @@ abstract class WidgetController {
   ///
   ///  - [sendKeyUpEvent] to simulate the corresponding key up event.
   ///  - [sendKeyEvent] to simulate both the key up and key down in the same call.
-  Future<bool> sendKeyDownEvent(LogicalKeyboardKey key, { String platform = _defaultPlatform }) async {
+  Future<bool> sendKeyDownEvent(LogicalKeyboardKey key, { String? character, String platform = _defaultPlatform }) async {
     assert(platform != null);
     // Internally wrapped in async guard.
-    return simulateKeyDownEvent(key, platform: platform);
+    return simulateKeyDownEvent(key, character: character, platform: platform);
   }
 
   /// Simulates sending a physical key up event through the system channel.

packages/flutter_test/lib/src/event_simulation.dart

@@ -194,6 +194,7 @@ class KeyEventSimulator {
     required String platform,
     bool isDown = true,
     PhysicalKeyboardKey? physicalKey,
+    String? character,
   }) {
     assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
 
@@ -211,27 +212,31 @@ class KeyEventSimulator {
       'keymap': platform,
     };
 
-    if (kIsWeb) {
+    final String resultCharacter = character ?? _keyLabel(key);
+    void assignWeb() {
       result['code'] = _getWebKeyCode(key);
-      result['key'] = _keyLabel(key);
+      result['key'] = resultCharacter;
       result['metaState'] = _getWebModifierFlags(key, isDown);
+    }
+    if (kIsWeb) {
+      assignWeb();
       return result;
     }
 
     switch (platform) {
       case 'android':
         result['keyCode'] = keyCode;
-        if (_keyLabel(key).isNotEmpty) {
-          result['codePoint'] = _keyLabel(key).codeUnitAt(0);
-          result['character'] = _keyLabel(key);
+        if (resultCharacter.isNotEmpty) {
+          result['codePoint'] = resultCharacter.codeUnitAt(0);
+          result['character'] = resultCharacter;
         }
         result['scanCode'] = scanCode;
         result['metaState'] = _getAndroidModifierFlags(key, isDown);
         break;
       case 'fuchsia':
         result['hidUsage'] = physicalKey.usbHidUsage;
-        if (_keyLabel(key).isNotEmpty) {
-          result['codePoint'] = _keyLabel(key).codeUnitAt(0);
+        if (resultCharacter.isNotEmpty) {
+          result['codePoint'] = resultCharacter.codeUnitAt(0);
         }
         result['modifiers'] = _getFuchsiaModifierFlags(key, isDown);
         break;
@@ -240,34 +245,33 @@ class KeyEventSimulator {
         result['keyCode'] = keyCode;
         result['scanCode'] = scanCode;
         result['modifiers'] = _getGlfwModifierFlags(key, isDown);
-        result['unicodeScalarValues'] = _keyLabel(key).isNotEmpty ? _keyLabel(key).codeUnitAt(0) : 0;
+        result['unicodeScalarValues'] = resultCharacter.isNotEmpty ? resultCharacter.codeUnitAt(0) : 0;
         break;
       case 'macos':
         result['keyCode'] = scanCode;
-        if (_keyLabel(key).isNotEmpty) {
-          result['characters'] = _keyLabel(key);
-          result['charactersIgnoringModifiers'] = _keyLabel(key);
+        if (resultCharacter.isNotEmpty) {
+          result['characters'] = resultCharacter;
+          result['charactersIgnoringModifiers'] = resultCharacter;
         }
         result['modifiers'] = _getMacOsModifierFlags(key, isDown);
         break;
       case 'ios':
         result['keyCode'] = scanCode;
-        result['characters'] = _keyLabel(key);
-        result['charactersIgnoringModifiers'] = _keyLabel(key);
+        result['characters'] = resultCharacter;
+        result['charactersIgnoringModifiers'] = resultCharacter;
         result['modifiers'] = _getIOSModifierFlags(key, isDown);
         break;
-      case 'web':
-        result['code'] = _getWebKeyCode(key);
-        result['key'] = _keyLabel(key);
-        result['metaState'] = _getWebModifierFlags(key, isDown);
-        break;
       case 'windows':
         result['keyCode'] = keyCode;
         result['scanCode'] = scanCode;
-        if (_keyLabel(key).isNotEmpty) {
-          result['characterCodePoint'] = _keyLabel(key).codeUnitAt(0);
+        if (resultCharacter.isNotEmpty) {
+          result['characterCodePoint'] = resultCharacter.codeUnitAt(0);
         }
         result['modifiers'] = _getWindowsModifierFlags(key, isDown);
+        break;
+      case 'web':
+        assignWeb();
+        break;
     }
     return result;
   }
@@ -631,12 +635,12 @@ class KeyEventSimulator {
   /// See also:
   ///
   ///  - [simulateKeyUpEvent] to simulate the corresponding key up event.
-  static Future<bool> simulateKeyDownEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey}) async {
+  static Future<bool> simulateKeyDownEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey, String? character}) async {
     return TestAsyncUtils.guard<bool>(() async {
       platform ??= Platform.operatingSystem;
       assert(_osIsSupported(platform!), 'Platform $platform not supported for key simulation');
 
-      final Map<String, dynamic> data = getKeyData(key, platform: platform!, isDown: true, physicalKey: physicalKey);
+      final Map<String, dynamic> data = getKeyData(key, platform: platform!, isDown: true, physicalKey: physicalKey, character: character);
       bool result = false;
       await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
         SystemChannels.keyEvent.name,
@@ -715,8 +719,8 @@ class KeyEventSimulator {
 /// See also:
 ///
 ///  - [simulateKeyUpEvent] to simulate the corresponding key up event.
-Future<bool> simulateKeyDownEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey}) {
-  return KeyEventSimulator.simulateKeyDownEvent(key, platform: platform, physicalKey: physicalKey);
+Future<bool> simulateKeyDownEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey, String? character}) {
+  return KeyEventSimulator.simulateKeyDownEvent(key, platform: platform, physicalKey: physicalKey, character: character);
 }
 
 /// Simulates sending a hardware key up event through the system channel.