Ability to disable the browser's context menu on web (#118194)

Enables custom context menus on web

packages/flutter/lib/services.dart

@@ -14,6 +14,7 @@ export 'src/services/asset_bundle.dart';
 export 'src/services/autofill.dart';
 export 'src/services/binary_messenger.dart';
 export 'src/services/binding.dart';
+export 'src/services/browser_context_menu.dart';
 export 'src/services/clipboard.dart';
 export 'src/services/debug.dart';
 export 'src/services/deferred_component.dart';

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

@@ -0,0 +1,83 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/foundation.dart';
+
+import 'system_channels.dart';
+
+/// Controls the browser's context menu on the web platform.
+///
+/// The context menu is the menu that appears on right clicking or selecting
+/// text in the browser, for example.
+///
+/// On web, by default, the browser's context menu is enabled and Flutter's
+/// context menus are hidden.
+///
+/// On all non-web platforms, this does nothing.
+class BrowserContextMenu {
+  BrowserContextMenu._();
+
+  static final BrowserContextMenu _instance = BrowserContextMenu._();
+
+  /// Whether showing the browser's context menu is enabled.
+  ///
+  /// When true, any event that the browser typically uses to trigger its
+  /// context menu (e.g. right click) will do so. When false, the browser's
+  /// context menu will not show.
+  ///
+  /// It's possible for this to be true but for the browser's context menu to
+  /// not show due to direct manipulation of the DOM. For example, handlers for
+  /// the browser's `contextmenu` event could be added/removed in the browser's
+  /// JavaScript console, and this boolean wouldn't know about it. This boolean
+  /// only indicates the results of calling [disableContextMenu] and
+  /// [enableContextMenu] here.
+  ///
+  /// Defaults to true.
+  static bool get enabled => _instance._enabled;
+
+  bool _enabled = true;
+
+  final MethodChannel _channel = SystemChannels.contextMenu;
+
+  /// Disable the browser's context menu.
+  ///
+  /// By default, when the app starts, the browser's context menu is already
+  /// enabled.
+  ///
+  /// This is an asynchronous action. The context menu can be considered to be
+  /// disabled at the time that the Future resolves. [enabled] won't reflect the
+  /// change until that time.
+  ///
+  /// See also:
+  ///  * [enableContextMenu], which performs the opposite operation.
+  static Future<void> disableContextMenu() {
+    assert(kIsWeb, 'This has no effect on platforms other than web.');
+    return _instance._channel.invokeMethod<void>(
+      'disableContextMenu',
+    ).then((_) {
+      _instance._enabled = false;
+    });
+  }
+
+  /// Enable the browser's context menu.
+  ///
+  /// By default, when the app starts, the browser's context menu is already
+  /// enabled. Typically this method would be called after first calling
+  /// [disableContextMenu].
+  ///
+  /// This is an asynchronous action. The context menu can be considered to be
+  /// enabled at the time that the Future resolves. [enabled] won't reflect the
+  /// change until that time.
+  ///
+  /// See also:
+  ///  * [disableContextMenu], which performs the opposite operation.
+  static Future<void> enableContextMenu() {
+    assert(kIsWeb, 'This has no effect on platforms other than web.');
+    return _instance._channel.invokeMethod<void>(
+      'enableContextMenu',
+    ).then((_) {
+      _instance._enabled = true;
+    });
+  }
+}

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

@@ -465,4 +465,17 @@ class SystemChannels {
   ///
   ///  * [DefaultPlatformMenuDelegate], which uses this channel.
   static const MethodChannel menu = OptionalMethodChannel('flutter/menu');
+
+  /// A [MethodChannel] for configuring the browser's context menu on web.
+  ///
+  /// The following outgoing methods are defined for this channel (invoked using
+  /// [OptionalMethodChannel.invokeMethod]):
+  ///
+  ///  * `enableContextMenu`: enables the browser's context menu. When a Flutter
+  ///    app starts, the browser's context menu is already enabled.
+  ///  * `disableContextMenu`: disables the browser's context menu.
+  static const MethodChannel contextMenu = OptionalMethodChannel(
+    'flutter/contextmenu',
+    JSONMethodCodec(),
+  );
 }

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

@@ -1893,7 +1893,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   final GlobalKey _editableKey = GlobalKey();
 
   /// Detects whether the clipboard can paste.
-  final ClipboardStatusNotifier? clipboardStatus = kIsWeb ? null : ClipboardStatusNotifier();
+  final ClipboardStatusNotifier clipboardStatus = ClipboardStatusNotifier();
 
   TextInputConnection? _textInputConnection;
   bool get _hasInputConnection => _textInputConnection?.attached ?? false;
@@ -1996,8 +1996,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       return widget.toolbarOptions.paste && !widget.readOnly;
     }
     return !widget.readOnly
-        && (clipboardStatus == null
+        && (clipboardStatus.value == ClipboardStatus.pasteable);
-          || clipboardStatus!.value == ClipboardStatus.pasteable);
   }
 
   @override
@@ -2074,7 +2073,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
           break;
       }
     }
-    clipboardStatus?.update();
+    clipboardStatus.update();
   }
 
   /// Cut current selection to [Clipboard].
@@ -2099,7 +2098,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       });
       hideToolbar();
     }
-    clipboardStatus?.update();
+    clipboardStatus.update();
   }
 
   /// Paste text from [Clipboard].
@@ -2285,7 +2284,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
           },
           type: ContextMenuButtonType.copy,
         ),
-      if (toolbarOptions.paste && clipboardStatus != null && pasteEnabled)
+      if (toolbarOptions.paste && pasteEnabled)
         ContextMenuButtonItem(
           onPressed: () {
             pasteText(SelectionChangedCause.toolbar);
@@ -2386,7 +2385,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   ///   button Widgets for the current platform given [ContextMenuButtonItem]s.
   List<ContextMenuButtonItem> get contextMenuButtonItems {
     return buttonItemsForToolbarOptions() ?? EditableText.getEditableButtonItems(
-      clipboardStatus: clipboardStatus?.value,
+      clipboardStatus: clipboardStatus.value,
       onCopy: copyEnabled
           ? () => copySelection(SelectionChangedCause.toolbar)
           : null,
@@ -2407,7 +2406,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   @override
   void initState() {
     super.initState();
-    clipboardStatus?.addListener(_onChangedClipboardStatus);
+    clipboardStatus.addListener(_onChangedClipboardStatus);
     widget.controller.addListener(_didChangeTextEditingValue);
     widget.focusNode.addListener(_handleFocusChanged);
     _scrollController.addListener(_onEditableScroll);
@@ -2531,8 +2530,8 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     final bool canPaste = widget.selectionControls is TextSelectionHandleControls
         ? pasteEnabled
         : widget.selectionControls?.canPaste(this) ?? false;
-    if (widget.selectionEnabled && pasteEnabled && clipboardStatus != null && canPaste) {
+    if (widget.selectionEnabled && pasteEnabled && canPaste) {
-      clipboardStatus!.update();
+      clipboardStatus.update();
     }
   }
 
@@ -2553,8 +2552,8 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     _selectionOverlay = null;
     widget.focusNode.removeListener(_handleFocusChanged);
     WidgetsBinding.instance.removeObserver(this);
-    clipboardStatus?.removeListener(_onChangedClipboardStatus);
+    clipboardStatus.removeListener(_onChangedClipboardStatus);
-    clipboardStatus?.dispose();
+    clipboardStatus.dispose();
     _cursorVisibilityNotifier.dispose();
     super.dispose();
     assert(_batchEditDepth <= 0, 'unfinished batch edits: $_batchEditDepth');
@@ -3688,17 +3687,18 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   @override
   bool showToolbar() {
     // Web is using native dom elements to enable clipboard functionality of the
-    // toolbar: copy, paste, select, cut. It might also provide additional
+    // context menu: copy, paste, select, cut. It might also provide additional
-    // functionality depending on the browser (such as translate). Due to this
+    // functionality depending on the browser (such as translate). Due to this,
-    // we should not show a Flutter toolbar for the editable text elements.
+    // we should not show a Flutter toolbar for the editable text elements
-    if (kIsWeb) {
+    // unless the browser's context menu is explicitly disabled.
+    if (kIsWeb && BrowserContextMenu.enabled) {
       return false;
     }
 
     if (_selectionOverlay == null) {
       return false;
     }
-    clipboardStatus?.update();
+    clipboardStatus.update();
     _selectionOverlay!.showToolbar();
     return true;
   }
@@ -3912,7 +3912,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
         && (widget.selectionControls is TextSelectionHandleControls
             ? pasteEnabled
             : pasteEnabled && (widget.selectionControls?.canPaste(this) ?? false))
-        && (clipboardStatus == null || clipboardStatus!.value == ClipboardStatus.pasteable)
+        && (clipboardStatus.value == ClipboardStatus.pasteable)
       ? () {
         controls?.handlePaste(this);
         pasteText(SelectionChangedCause.toolbar);

packages/flutter/test/material/text_field_test.dart

@@ -11914,7 +11914,7 @@ void main() {
     },
   );
 
-  testWidgets('Web does not check the clipboard status', (WidgetTester tester) async {
+  testWidgets('clipboard status is checked via hasStrings without getting the full clipboard contents', (WidgetTester tester) async {
     final TextEditingController controller = TextEditingController(
       text: 'Atwater Peel Sherbrooke Bonaventure',
     );
@@ -11958,14 +11958,8 @@ void main() {
     // getData is not called unless something is pasted.  hasStrings is used to
     // check the status of the clipboard.
     expect(calledGetData, false);
-    if (kIsWeb) {
-      // hasStrings is not checked because web doesn't show a custom text
-      // selection menu.
-      expect(calledHasStrings, false);
-    } else {
     // hasStrings is checked in order to decide if the content can be pasted.
     expect(calledHasStrings, true);
-    }
   });
 
   testWidgets('TextField changes mouse cursor when hovered', (WidgetTester tester) async {

packages/flutter/test/services/browser_context_menu_test.dart

@@ -0,0 +1,82 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  final List<MethodCall> log = <MethodCall>[];
+
+  Future<void> verify(AsyncCallback test, List<Object> expectations) async {
+    log.clear();
+    await test();
+    expect(log, expectations);
+  }
+
+  group('not on web', () {
+    test('disableContextMenu asserts', () async {
+      try {
+        BrowserContextMenu.disableContextMenu();
+      } catch (error) {
+        expect(error, isAssertionError);
+      }
+    });
+
+    test('enableContextMenu asserts', () async {
+      try {
+        BrowserContextMenu.enableContextMenu();
+      } catch (error) {
+        expect(error, isAssertionError);
+      }
+    });
+  },
+    skip: kIsWeb, // [intended]
+  );
+
+  group('on web', () {
+    group('disableContextMenu', () {
+      // Make sure the context menu is enabled (default) after the test.
+      tearDown(() async {
+        TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.contextMenu, (MethodCall methodCall) {
+          return null;
+        });
+        await BrowserContextMenu.enableContextMenu();
+        TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.contextMenu, null);
+      });
+
+      test('disableContextMenu calls its platform channel method', () async {
+        TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.contextMenu, (MethodCall methodCall) async {
+          log.add(methodCall);
+          return null;
+        });
+
+        await verify(BrowserContextMenu.disableContextMenu, <Object>[
+          isMethodCall('disableContextMenu', arguments: null),
+        ]);
+
+        TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.contextMenu, null);
+      });
+    });
+
+    group('enableContextMenu', () {
+      test('enableContextMenu calls its platform channel method', () async {
+        TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.contextMenu, (MethodCall methodCall) async {
+          log.add(methodCall);
+          return null;
+        });
+
+        await verify(BrowserContextMenu.enableContextMenu, <Object>[
+          isMethodCall('enableContextMenu', arguments: null),
+        ]);
+
+        TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.contextMenu, null);
+      });
+    });
+  },
+    skip: !kIsWeb, // [intended]
+  );
+}

packages/flutter/test/services/text_input_test.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-
 import 'dart:convert' show jsonDecode;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/editable_text_test.dart

@@ -1488,13 +1488,14 @@ void main() {
       expect(tester.takeException(), isNull);
   });
 
-  /// Toolbar is not used in Flutter Web. Skip this check.
+  // Toolbar is not used in Flutter Web unless the browser context menu is
-  ///
+  // explicitly disabled. Skip this check.
-  /// Web is using native DOM elements (it is also used as platform input)
+  //
-  /// to enable clipboard functionality of the toolbar: copy, paste, select,
+  // Web is using native DOM elements (it is also used as platform input)
-  /// cut. It might also provide additional functionality depending on the
+  // to enable clipboard functionality of the toolbar: copy, paste, select,
-  /// browser (such as translation). Due to this, in browsers, we should not
+  // cut. It might also provide additional functionality depending on the
-  /// show a Flutter toolbar for the editable text elements.
+  // browser (such as translation). Due to this, in browsers, we should not
+  // show a Flutter toolbar for the editable text elements.
   testWidgets('can show toolbar when there is text and a selection', (WidgetTester tester) async {
     await tester.pumpWidget(
       MaterialApp(
@@ -1542,6 +1543,69 @@ void main() {
     expect(find.text('Paste'), kIsWeb ? findsNothing : findsOneWidget);
   });
 
+  group('BrowserContextMenu', () {
+    setUp(() async {
+      SystemChannels.contextMenu.setMockMethodCallHandler((MethodCall call) {
+        // Just complete successfully, so that BrowserContextMenu thinks that
+        // the engine successfully received its call.
+        return Future<void>.value();
+      });
+      await BrowserContextMenu.disableContextMenu();
+    });
+
+    tearDown(() async {
+      await BrowserContextMenu.enableContextMenu();
+      SystemChannels.contextMenu.setMockMethodCallHandler(null);
+    });
+
+    testWidgets('web can show toolbar when the browser context menu is disabled', (WidgetTester tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: EditableText(
+            backgroundCursorColor: Colors.grey,
+            controller: controller,
+            focusNode: focusNode,
+            style: textStyle,
+            cursorColor: cursorColor,
+            selectionControls: materialTextSelectionControls,
+          ),
+        ),
+      );
+
+      final EditableTextState state =
+          tester.state<EditableTextState>(find.byType(EditableText));
+
+      // Can't show the toolbar when there's no focus.
+      expect(state.showToolbar(), false);
+      await tester.pumpAndSettle();
+      expect(find.text('Paste'), findsNothing);
+
+      // Can show the toolbar when focused even though there's no text.
+      state.renderEditable.selectWordsInRange(
+        from: Offset.zero,
+        cause: SelectionChangedCause.tap,
+      );
+      await tester.pump();
+      expect(state.showToolbar(), isTrue);
+      await tester.pumpAndSettle();
+      expect(find.text('Paste'), findsOneWidget);
+
+      // Hide the menu again.
+      state.hideToolbar();
+      await tester.pump();
+      expect(find.text('Paste'), findsNothing);
+
+      // Can show the menu with text and a selection.
+      controller.text = 'blah';
+      await tester.pump();
+      expect(state.showToolbar(), isTrue);
+      await tester.pumpAndSettle();
+      expect(find.text('Paste'), findsOneWidget);
+    },
+      skip: !kIsWeb, // [intended]
+    );
+  });
+
   testWidgets('can hide toolbar with DismissIntent', (WidgetTester tester) async {
     await tester.pumpWidget(
       MaterialApp(