Disable context menu (#128365)

## Description

Changes the context menu example for `MenuAnchor` so that it uses right-click, or (on macOS and iOS only) ctrl-left-click, for the context menu. Also disables the browser context menu on web platforms.

## Tests
 - Updated test to reflect new triggers.

examples/api/lib/material/menu_anchor/menu_anchor.1.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:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
@@ -41,6 +42,7 @@ class _MyContextMenuState extends State<MyContextMenu> {
   final FocusNode _buttonFocusNode = FocusNode(debugLabel: 'Menu Button');
   final MenuController _menuController = MenuController();
   ShortcutRegistryEntry? _shortcutsEntry;
+  bool _menuWasEnabled = false;
 
   Color get backgroundColor => _backgroundColor;
   Color _backgroundColor = Colors.red;
@@ -62,6 +64,12 @@ class _MyContextMenuState extends State<MyContextMenu> {
     }
   }
 
+  @override
+  void initState() {
+    super.initState();
+    _disableContextMenu();
+  }
+
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
@@ -84,15 +92,38 @@ class _MyContextMenuState extends State<MyContextMenu> {
   void dispose() {
     _shortcutsEntry?.dispose();
     _buttonFocusNode.dispose();
+    _reenableContextMenu();
     super.dispose();
   }
 
+  Future<void> _disableContextMenu() async {
+    if (!kIsWeb) {
+      // Does nothing on non-web platforms.
+      return;
+    }
+    _menuWasEnabled = BrowserContextMenu.enabled;
+    if (_menuWasEnabled) {
+      await BrowserContextMenu.disableContextMenu();
+    }
+  }
+
+  void _reenableContextMenu() {
+    if (!kIsWeb) {
+      // Does nothing on non-web platforms.
+      return;
+    }
+    if (_menuWasEnabled && !BrowserContextMenu.enabled) {
+      BrowserContextMenu.enableContextMenu();
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     return Padding(
       padding: const EdgeInsets.all(50),
       child: GestureDetector(
         onTapDown: _handleTapDown,
+        onSecondaryTapDown: _handleSecondaryTapDown,
         child: MenuAnchor(
           controller: _menuController,
           anchorTapClosesMenu: true,
@@ -142,7 +173,7 @@ class _MyContextMenuState extends State<MyContextMenu> {
               children: <Widget>[
                 const Padding(
                   padding: EdgeInsets.all(8.0),
-                  child: Text('Ctrl-click anywhere on the background to show the menu.'),
+                  child: Text('Right-click anywhere on the background to show the menu.'),
                 ),
                 Padding(
                   padding: const EdgeInsets.all(12.0),
@@ -185,13 +216,29 @@ class _MyContextMenuState extends State<MyContextMenu> {
     }
   }
 
-  void _handleTapDown(TapDownDetails details) {
-    if (!HardwareKeyboard.instance.logicalKeysPressed.contains(LogicalKeyboardKey.controlLeft) &&
-        !HardwareKeyboard.instance.logicalKeysPressed.contains(LogicalKeyboardKey.controlRight)) {
-      return;
-    }
+  void _handleSecondaryTapDown(TapDownDetails details) {
     _menuController.open(position: details.localPosition);
   }
+
+  void _handleTapDown(TapDownDetails details) {
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.linux:
+      case TargetPlatform.windows:
+        // Don't open the menu on these platforms with a Ctrl-tap (or a
+        // tap).
+        break;
+      case TargetPlatform.iOS:
+      case TargetPlatform.macOS:
+        // Only open the menu on these platforms if the control button is down
+        // when the tap occurs.
+        if (HardwareKeyboard.instance.logicalKeysPressed.contains(LogicalKeyboardKey.controlLeft) ||
+            HardwareKeyboard.instance.logicalKeysPressed.contains(LogicalKeyboardKey.controlRight)) {
+          _menuController.open(position: details.localPosition);
+        }
+    }
+  }
 }
 
 class ContextMenuApp extends StatelessWidget {

examples/api/test/material/menu_anchor/menu_anchor.1_test.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:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_api_samples/material/menu_anchor/menu_anchor.1.dart' as example;
@@ -18,15 +19,13 @@ void main() {
 
     await tester.pumpWidget(const example.ContextMenuApp());
 
-    await tester.sendKeyDownEvent(LogicalKeyboardKey.controlRight);
-    await tester.tapAt(const Offset(100, 200));
+    await tester.tapAt(const Offset(100, 200), buttons: kSecondaryButton);
     await tester.pump();
     expect(tester.getRect(findMenu()), equals(const Rect.fromLTRB(100.0, 200.0, 433.0, 360.0)));
 
     // Make sure tapping in a different place causes the menu to move.
-    await tester.tapAt(const Offset(200, 100));
+    await tester.tapAt(const Offset(200, 100), buttons: kSecondaryButton);
     await tester.pump();
-    await tester.sendKeyUpEvent(LogicalKeyboardKey.controlRight);
 
     expect(tester.getRect(findMenu()), equals(const Rect.fromLTRB(200.0, 100.0, 533.0, 260.0)));
 
@@ -67,8 +66,7 @@ void main() {
     );
 
     // Open the menu so we can look for state changes reflected in the menu.
-    await tester.sendKeyDownEvent(LogicalKeyboardKey.controlRight);
-    await tester.tapAt(const Offset(100, 200));
+    await tester.tapAt(const Offset(100, 200), buttons: kSecondaryButton);
     await tester.pump();
 
     expect(find.text(example.MenuEntry.showMessage.label), findsOneWidget);