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

// 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;
    });
  }
}