[web] Move context menu handling to its own class

ci/licenses_golden/licenses_flutter

@@ -2042,7 +2042,9 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/js_interop/js_typed_data.dart
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/key_map.g.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/keyboard_binding.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/layers.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/mouse/context_menu.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/mouse/cursor.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/mouse/prevent_default.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/navigation/history.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/noto_font.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/noto_font_encoding.dart + ../../../flutter/LICENSE
@@ -4795,7 +4797,9 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/js_interop/js_typed_data.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/key_map.g.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/keyboard_binding.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/layers.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/mouse/context_menu.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/mouse/cursor.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/mouse/prevent_default.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/history.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/noto_font.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/noto_font_encoding.dart

lib/web_ui/lib/src/engine.dart

@@ -111,7 +111,9 @@ export 'engine/js_interop/js_typed_data.dart';
 export 'engine/key_map.g.dart';
 export 'engine/keyboard_binding.dart';
 export 'engine/layers.dart';
+export 'engine/mouse/context_menu.dart';
 export 'engine/mouse/cursor.dart';
+export 'engine/mouse/prevent_default.dart';
 export 'engine/navigation/history.dart';
 export 'engine/noto_font.dart';
 export 'engine/noto_font_encoding.dart';

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

@@ -318,20 +318,6 @@ class FlutterViewEmbedder {
     assert(element.parentNode == _resourcesHost);
     element.remove();
   }
-
-  /// Disables the browser's context menu for this part of the DOM.
-  ///
-  /// By default, when a Flutter web app starts, the context menu is enabled.
-  ///
-  /// Can be re-enabled by calling [enableContextMenu].
-  void disableContextMenu() => _embeddingStrategy.disableContextMenu();
-
-  /// Enables the browser's context menu for this part of the DOM.
-  ///
-  /// By default, when a Flutter web app starts, the context menu is already
-  /// enabled. Typically, this method would be used after calling
-  /// [disableContextMenu] to first disable it.
-  void enableContextMenu() => _embeddingStrategy.enableContextMenu();
 }
 
 /// The embedder singleton.

lib/web_ui/lib/src/engine/mouse/context_menu.dart

@@ -0,0 +1,42 @@
+// Copyright 2013 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 '../dom.dart';
+import 'prevent_default.dart';
+
+/// Controls the browser's context menu in the given [element].
+class ContextMenu {
+  ContextMenu(this.element);
+
+  final DomElement element;
+
+  /// False when the context menu has been disabled, otherwise true.
+  bool _enabled = true;
+
+  /// Disables the browser's context menu for this [element].
+  ///
+  /// By default, when a Flutter web app starts, the context menu is enabled.
+  ///
+  /// Can be re-enabled by calling [enable].
+  void disable() {
+    if (!_enabled) {
+      return;
+    }
+    _enabled = false;
+    element.addEventListener('contextmenu', preventDefaultListener);
+  }
+
+  /// Enables the browser's context menu for this [element].
+  ///
+  /// By default, when a Flutter web app starts, the context menu is already
+  /// enabled. Typically, this method would be used after calling
+  /// [disable] to first disable it.
+  void enable() {
+    if (_enabled) {
+      return;
+    }
+    _enabled = true;
+    element.removeEventListener('contextmenu', preventDefaultListener);
+  }
+}

lib/web_ui/lib/src/engine/mouse/prevent_default.dart

@@ -0,0 +1,10 @@
+// Copyright 2013 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 '../dom.dart';
+
+/// Listener for DOM events that prevents the default browser behavior.
+final DomEventListener preventDefaultListener = createDomEventListener((DomEvent event) {
+  event.preventDefault();
+});

lib/web_ui/lib/src/engine/platform_dispatcher.dart

@@ -566,11 +566,11 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
         final MethodCall decoded = codec.decodeMethodCall(data);
         switch (decoded.method) {
           case 'enableContextMenu':
-            flutterViewEmbedder.enableContextMenu();
+            implicitView!.contextMenu.enable();
             replyToPlatformMessage(callback, codec.encodeSuccessEnvelope(true));
             return;
           case 'disableContextMenu':
-            flutterViewEmbedder.disableContextMenu();
+            implicitView!.contextMenu.disable();
             replyToPlatformMessage(callback, codec.encodeSuccessEnvelope(true));
             return;
         }

lib/web_ui/lib/src/engine/text_editing/text_editing.dart

@@ -12,6 +12,7 @@ import 'package:ui/ui.dart' as ui;
 import '../browser_detection.dart';
 import '../dom.dart';
 import '../embedder.dart';
+import '../mouse/prevent_default.dart';
 import '../platform_dispatcher.dart';
 import '../safe_browser_api.dart';
 import '../semantics.dart';
@@ -210,9 +211,7 @@ class EngineAutofillForm {
     formElement.noValidate = true;
     formElement.method = 'post';
     formElement.action = '#';
-    formElement.addEventListener('submit', createDomEventListener((DomEvent e) {
-      e.preventDefault();
-    }));
+    formElement.addEventListener('submit', preventDefaultListener);
 
     // We need to explicitly disable pointer events on the form in Safari Desktop,
     // so that we don't have pointer event collisions if users hover over or click

lib/web_ui/lib/src/engine/view_embedder/embedding_strategy/custom_element_embedding_strategy.dart

@@ -51,12 +51,6 @@ class CustomElementEmbeddingStrategy extends EmbeddingStrategy {
     registerElementForCleanup(resourceHost);
   }
 
-  @override
-  void disableContextMenu() => disableContextMenuOn(_hostElement);
-
-  @override
-  void enableContextMenu() => enableContextMenuOn(_hostElement);
-
   void _setHostAttribute(String name, String value) {
     _hostElement.setAttribute(name, value);
   }

lib/web_ui/lib/src/engine/view_embedder/embedding_strategy/embedding_strategy.dart

@@ -20,7 +20,7 @@ import 'full_page_embedding_strategy.dart';
 /// * [CustomElementEmbeddingStrategy] - Flutter is rendered inside a custom host
 ///   element, provided by the web app programmer through the engine
 ///   initialization.
-abstract class EmbeddingStrategy with _ContextMenu {
+abstract class EmbeddingStrategy {
   EmbeddingStrategy() {
     // Initialize code to handle hot-restart (debug only).
     assert(() {
@@ -56,71 +56,3 @@ abstract class EmbeddingStrategy with _ContextMenu {
     _hotRestartCache?.registerElement(element);
   }
 }
-
-/// Provides functionality to disable and enable the browser's context menu.
-mixin _ContextMenu {
-  /// False when the context menu has been disabled, otherwise true.
-  bool _contextMenuEnabled = true;
-
-  /// Listener for contextmenu events that prevents the browser's context menu
-  /// from being shown.
-  final DomEventListener _disablingContextMenuListener = createDomEventListener((DomEvent event) {
-    event.preventDefault();
-  });
-
-  /// Disables the browser's context menu for this part of the DOM.
-  ///
-  /// By default, when a Flutter web app starts, the context menu is enabled.
-  ///
-  /// Can be re-enabled by calling [enableContextMenu].
-  ///
-  /// See also:
-  ///
-  ///  * [disableContextMenuOn], which is like this but takes the relevant
-  ///    [DomElement] as a parameter.
-  void disableContextMenu();
-
-  /// Disables the browser's context menu for the given [DomElement].
-  ///
-  /// See also:
-  ///
-  ///  * [disableContextMenu], which is like this but is not passed a
-  ///    [DomElement].
-  @protected
-  void disableContextMenuOn(DomEventTarget element) {
-    if (!_contextMenuEnabled) {
-      return;
-    }
-
-    element.addEventListener('contextmenu', _disablingContextMenuListener);
-    _contextMenuEnabled = false;
-  }
-
-  /// Enables the browser's context menu for this part of the DOM.
-  ///
-  /// By default, when a Flutter web app starts, the context menu is already
-  /// enabled. Typically, this method would be used after calling
-  /// [disableContextMenu] to first disable it.
-  ///
-  /// See also:
-  ///
-  ///  * [enableContextMenuOn], which is like this but takes the relevant
-  ///    [DomElement] as a parameter.
-  void enableContextMenu();
-
-  /// Enables the browser's context menu for the given [DomElement].
-  ///
-  /// See also:
-  ///
-  ///  * [enableContextMenu], which is like this but is not passed a
-  ///    [DomElement].
-  @protected
-  void enableContextMenuOn(DomEventTarget element) {
-    if (_contextMenuEnabled) {
-      return;
-    }
-
-    element.removeEventListener('contextmenu', _disablingContextMenuListener);
-    _contextMenuEnabled = true;
-  }
-}

lib/web_ui/lib/src/engine/view_embedder/embedding_strategy/full_page_embedding_strategy.dart

@@ -48,12 +48,6 @@ class FullPageEmbeddingStrategy extends EmbeddingStrategy {
     registerElementForCleanup(resourceHost);
   }
 
-  @override
-  void disableContextMenu() => disableContextMenuOn(domWindow);
-
-  @override
-  void enableContextMenu() => enableContextMenuOn(domWindow);
-
   void _setHostAttribute(String name, String value) {
     domDocument.body!.setAttribute(name, value);
   }

lib/web_ui/lib/src/engine/window.dart

@@ -17,6 +17,7 @@ import '../engine.dart' show DimensionsProvider, registerHotRestartListener, ren
 import 'display.dart';
 import 'dom.dart';
 import 'embedder.dart';
+import 'mouse/context_menu.dart';
 import 'mouse/cursor.dart';
 import 'navigation/history.dart';
 import 'platform_dispatcher.dart';
@@ -36,6 +37,7 @@ const int kImplicitViewId = 0;
 /// In addition to everything defined in [ui.FlutterView], this class adds
 /// a few web-specific properties.
 abstract interface class EngineFlutterView extends ui.FlutterView {
+  ContextMenu get contextMenu;
   MouseCursor get mouseCursor;
   DomElement get rootElement;
 }
@@ -67,6 +69,9 @@ class EngineFlutterWindow extends ui.SingletonFlutterWindow implements EngineFlu
   @override
   late final MouseCursor mouseCursor = MouseCursor(rootElement);
 
+  @override
+  late final ContextMenu contextMenu = ContextMenu(rootElement);
+
   @override
   DomElement get rootElement => flutterViewEmbedder.flutterViewElement;
 

lib/web_ui/test/engine/mouse/context_menu_test.dart

@@ -0,0 +1,104 @@
+// Copyright 2013 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:test/bootstrap/browser.dart';
+import 'package:test/test.dart';
+import 'package:ui/src/engine.dart';
+
+void main() {
+  internalBootstrapBrowserTest(() => testMain);
+}
+
+void testMain() {
+  group('$ContextMenu', () {
+    test('can disable context menu', () {
+      final DomElement rootViewElement = createDomElement('div');
+      final ContextMenu contextMenu = ContextMenu(rootViewElement);
+
+      // When the app starts, contextmenu events are not prevented.
+      DomEvent event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+
+      // Disabling the context menu causes contextmenu events to be prevented.
+      contextMenu.disable();
+      event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isTrue);
+
+      // Disabling again has no effect.
+      contextMenu.disable();
+      event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isTrue);
+    });
+
+    test('does not disable context menu outside root view element', () {
+      final DomElement rootViewElement = createDomElement('div');
+      final ContextMenu contextMenu = ContextMenu(rootViewElement);
+
+      contextMenu.disable();
+
+      // Dispatching on a DOM element outside of target's subtree has no effect.
+      final DomEvent event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      domDocument.body!.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+    });
+
+    test('can enable context menu after disabling', () {
+      final DomElement rootViewElement = createDomElement('div');
+      final ContextMenu contextMenu = ContextMenu(rootViewElement);
+
+      // When the app starts, contextmenu events are not prevented.
+      DomEvent event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+
+      // Disabling the context menu causes contextmenu events to be prevented.
+      contextMenu.disable();
+      event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isTrue);
+
+      // Enabling the context menu means that contextmenu events are back to not
+      // being prevented.
+      contextMenu.enable();
+      event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+
+      // Enabling again has no effect.
+      contextMenu.enable();
+      event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+    });
+
+    test('enabling before disabling has no effect', () {
+      final DomElement rootViewElement = createDomElement('div');
+      final ContextMenu contextMenu = ContextMenu(rootViewElement);
+
+      // When the app starts, contextmenu events are not prevented.
+      DomEvent event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+
+      // Enabling has no effect.
+      contextMenu.enable();
+      event = createDomEvent('Event', 'contextmenu');
+      expect(event.defaultPrevented, isFalse);
+      rootViewElement.dispatchEvent(event);
+      expect(event.defaultPrevented, isFalse);
+    });
+  });
+}