lib/web_ui/lib/src/engine/window.dart - mirrors/engine - Git at Google

 // 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.

 @JS()
 library window;

 import 'dart:async';
 import 'dart:html' as html;
 import 'dart:typed_data';

 import 'package:js/js.dart';
 import 'package:meta/meta.dart';
 import 'package:ui/ui.dart' as ui;

 import '../engine.dart' show registerHotRestartListener;
 import 'browser_detection.dart';
 import 'navigation/history.dart';
 import 'navigation/js_url_strategy.dart';
 import 'navigation/url_strategy.dart';
 import 'platform_dispatcher.dart';
 import 'services.dart';
 import 'test_embedding.dart';

 typedef _HandleMessageCallBack = Future<bool> Function();

 /// When set to true, all platform messages will be printed to the console.
 const bool debugPrintPlatformMessages = false;

 /// Whether [_customUrlStrategy] has been set or not.
 ///
 /// It is valid to set [_customUrlStrategy] to null, so we can't use a null
 /// check to determine whether it was set or not. We need an extra boolean.
 bool _isUrlStrategySet = false;

 /// A custom URL strategy set by the app before running.
 UrlStrategy? _customUrlStrategy;
 set customUrlStrategy(UrlStrategy? strategy) {
   assert(!_isUrlStrategySet, 'Cannot set URL strategy more than once.');
   _isUrlStrategySet = true;
   _customUrlStrategy = strategy;
 }

 /// The Web implementation of [ui.SingletonFlutterWindow].
 class EngineFlutterWindow extends ui.SingletonFlutterWindow {
   EngineFlutterWindow(this._windowId, this.platformDispatcher) {
     final EnginePlatformDispatcher engineDispatcher =
         platformDispatcher as EnginePlatformDispatcher;
     engineDispatcher.windows[_windowId] = this;
     engineDispatcher.windowConfigurations[_windowId] = const ui.ViewConfiguration();
     if (_isUrlStrategySet) {
       _browserHistory =
           MultiEntriesBrowserHistory(urlStrategy: _customUrlStrategy);
     }
     registerHotRestartListener(() {
       window.resetHistory();
     });
   }

   final Object _windowId;

   @override
   final ui.PlatformDispatcher platformDispatcher;

   /// Handles the browser history integration to allow users to use the back
   /// button, etc.
   BrowserHistory get browserHistory {
     return _browserHistory ??=
         MultiEntriesBrowserHistory(urlStrategy: _urlStrategyForInitialization);
   }

   UrlStrategy? get _urlStrategyForInitialization {
     final UrlStrategy? urlStrategy =
         _isUrlStrategySet ? _customUrlStrategy : _createDefaultUrlStrategy();
     // Prevent any further customization of URL strategy.
     _isUrlStrategySet = true;
     return urlStrategy;
   }

   BrowserHistory?
       _browserHistory; // Must be either SingleEntryBrowserHistory or MultiEntriesBrowserHistory.

   Future<void> _useSingleEntryBrowserHistory() async {
     if (_browserHistory is SingleEntryBrowserHistory) {
       return;
     }

     final UrlStrategy? strategy;
     if (_browserHistory == null) {
       strategy = _urlStrategyForInitialization;
     } else {
       strategy = _browserHistory?.urlStrategy;
       await _browserHistory?.tearDown();
     }
     _browserHistory = SingleEntryBrowserHistory(urlStrategy: strategy);
   }

   Future<void> _useMultiEntryBrowserHistory() async {
     if (_browserHistory is MultiEntriesBrowserHistory) {
       return;
     }

     final UrlStrategy? strategy;
     if (_browserHistory == null) {
       strategy = _urlStrategyForInitialization;
     } else {
       strategy = _browserHistory?.urlStrategy;
       await _browserHistory?.tearDown();
     }
     _browserHistory = MultiEntriesBrowserHistory(urlStrategy: strategy);
   }

   @visibleForTesting
   Future<void> debugInitializeHistory(
     UrlStrategy? strategy, {
     required bool useSingle,
   }) async {
     // Prevent any further customization of URL strategy.
     _isUrlStrategySet = true;
     await _browserHistory?.tearDown();
     if (useSingle) {
       _browserHistory = SingleEntryBrowserHistory(urlStrategy: strategy);
     } else {
       _browserHistory = MultiEntriesBrowserHistory(urlStrategy: strategy);
     }
   }

   Future<void> resetHistory() async {
     await _browserHistory?.tearDown();
     _browserHistory = null;
     // Reset the globals too.
     _isUrlStrategySet = false;
     _customUrlStrategy = null;
   }

   Future<void> _endOfTheLine = Future<void>.value(null);

   Future<bool> _waitInTheLine(_HandleMessageCallBack callback) async {
     final Future<void> currentPosition = _endOfTheLine;
     final Completer<void> completer = Completer<void>();
     _endOfTheLine = completer.future;
     await currentPosition;
     bool result = false;
     try {
       result = await callback();
     } finally {
       completer.complete();
     }
     return result;
   }

   Future<bool> handleNavigationMessage(ByteData? data) async {
     return _waitInTheLine(() async {
       final MethodCall decoded = const JSONMethodCodec().decodeMethodCall(data);
       final Map<String, dynamic>? arguments = decoded.arguments;
       switch (decoded.method) {
         case 'selectMultiEntryHistory':
           await _useMultiEntryBrowserHistory();
           return true;
         case 'selectSingleEntryHistory':
           await _useSingleEntryBrowserHistory();
           return true;
         // the following cases assert that arguments are not null
         case 'routeUpdated': // deprecated
           assert(arguments != null);
           await _useSingleEntryBrowserHistory();
           browserHistory.setRouteName(arguments!['routeName']);
           return true;
         case 'routeInformationUpdated':
           assert(arguments != null);
           browserHistory.setRouteName(
             arguments!['location'],
             state: arguments['state'],
             replace: arguments['replace'] ?? false,
           );
           return true;
       }
       return false;
     });
   }

   @override
   ui.ViewConfiguration get viewConfiguration {
     final EnginePlatformDispatcher engineDispatcher =
         platformDispatcher as EnginePlatformDispatcher;
     assert(engineDispatcher.windowConfigurations.containsKey(_windowId));
     return engineDispatcher.windowConfigurations[_windowId] ??
         const ui.ViewConfiguration();
   }

   @override
   ui.Size get physicalSize {
     if (_physicalSize == null) {
       computePhysicalSize();
     }
     assert(_physicalSize != null);
     return _physicalSize!;
   }

   /// Computes the physical size of the screen from [html.window].
   ///
   /// This function is expensive. It triggers browser layout if there are
   /// pending DOM writes.
   void computePhysicalSize() {
     bool override = false;

     assert(() {
       if (webOnlyDebugPhysicalSizeOverride != null) {
         _physicalSize = webOnlyDebugPhysicalSizeOverride;
         override = true;
       }
       return true;
     }());

     if (!override) {
       double windowInnerWidth;
       double windowInnerHeight;
       final html.VisualViewport? viewport = html.window.visualViewport;

       if (viewport != null) {
         if (operatingSystem == OperatingSystem.iOs) {
           /// Chrome on iOS reports incorrect viewport.height when app
           /// starts in portrait orientation and the phone is rotated to
           /// landscape.
           ///
           /// We instead use documentElement clientWidth/Height to read
           /// accurate physical size. VisualViewport api is only used during
           /// text editing to make sure inset is correctly reported to
           /// framework.
           final double docWidth =
               html.document.documentElement!.clientWidth.toDouble();
           final double docHeight =
               html.document.documentElement!.clientHeight.toDouble();
           windowInnerWidth = docWidth * devicePixelRatio;
           windowInnerHeight = docHeight * devicePixelRatio;
         } else {
           windowInnerWidth = viewport.width!.toDouble() * devicePixelRatio;
           windowInnerHeight = viewport.height!.toDouble() * devicePixelRatio;
         }
       } else {
         windowInnerWidth = html.window.innerWidth! * devicePixelRatio;
         windowInnerHeight = html.window.innerHeight! * devicePixelRatio;
       }
       _physicalSize = ui.Size(
         windowInnerWidth,
         windowInnerHeight,
       );
     }
   }

   /// Forces the window to recompute its physical size. Useful for tests.
   void debugForceResize() {
     computePhysicalSize();
   }

   void computeOnScreenKeyboardInsets(bool isEditingOnMobile) {
     double windowInnerHeight;
     final html.VisualViewport? viewport = html.window.visualViewport;
     if (viewport != null) {
       if (operatingSystem == OperatingSystem.iOs && !isEditingOnMobile) {
         windowInnerHeight =
             html.document.documentElement!.clientHeight * devicePixelRatio;
       } else {
         windowInnerHeight = viewport.height!.toDouble() * devicePixelRatio;
       }
     } else {
       windowInnerHeight = html.window.innerHeight! * devicePixelRatio;
     }
     final double bottomPadding = _physicalSize!.height - windowInnerHeight;
     _viewInsets =
         WindowPadding(bottom: bottomPadding, left: 0, right: 0, top: 0);
   }

   /// Uses the previous physical size and current innerHeight/innerWidth
   /// values to decide if a device is rotating.
   ///
   /// During a rotation the height and width values will (almost) swap place.
   /// Values can slightly differ due to space occupied by the browser header.
   /// For example the following values are collected for Pixel 3 rotation:
   ///
   /// height: 658 width: 393
   /// new height: 313 new width: 738
   ///
   /// The following values are from a changed caused by virtual keyboard.
   ///
   /// height: 658 width: 393
   /// height: 368 width: 393
   bool isRotation() {
     double height = 0;
     double width = 0;
     if (html.window.visualViewport != null) {
       height =
           html.window.visualViewport!.height!.toDouble() * devicePixelRatio;
       width = html.window.visualViewport!.width!.toDouble() * devicePixelRatio;
     } else {
       height = html.window.innerHeight! * devicePixelRatio;
       width = html.window.innerWidth! * devicePixelRatio;
     }

     // This method compares the new dimensions with the previous ones.
     // Return false if the previous dimensions are not set.
     if (_physicalSize != null) {
       // First confirm both height and width are effected.
       if (_physicalSize!.height != height && _physicalSize!.width != width) {
         // If prior to rotation height is bigger than width it should be the
         // opposite after the rotation and vice versa.
         if ((_physicalSize!.height > _physicalSize!.width && height < width) ||
             (_physicalSize!.width > _physicalSize!.height && width < height)) {
           // Rotation detected
           return true;
         }
       }
     }
     return false;
   }

   @override
   WindowPadding get viewInsets => _viewInsets;
   WindowPadding _viewInsets = ui.WindowPadding.zero as WindowPadding;

   /// Lazily populated and cleared at the end of the frame.
   ui.Size? _physicalSize;

   /// Overrides the value of [physicalSize] in tests.
   ui.Size? webOnlyDebugPhysicalSizeOverride;
 }

 typedef _JsSetUrlStrategy = void Function(JsUrlStrategy?);

 /// A JavaScript hook to customize the URL strategy of a Flutter app.
 //
 // Keep this js name in sync with flutter_web_plugins. Find it at:
 // https://github.com/flutter/flutter/blob/custom_location_strategy/packages/flutter_web_plugins/lib/src/navigation/js_url_strategy.dart
 //
 // TODO: Add integration test https://github.com/flutter/flutter/issues/66852
 @JS('_flutter_web_set_location_strategy')
 external set jsSetUrlStrategy(_JsSetUrlStrategy? newJsSetUrlStrategy);

 UrlStrategy? _createDefaultUrlStrategy() {
   return ui.debugEmulateFlutterTesterEnvironment
       ? TestUrlStrategy.fromEntry(const TestHistoryEntry('default', null, '/'))
       : const HashUrlStrategy();
 }

 /// The Web implementation of [ui.SingletonFlutterWindow].
 class EngineSingletonFlutterWindow extends EngineFlutterWindow {
   EngineSingletonFlutterWindow(
       Object windowId, ui.PlatformDispatcher platformDispatcher)
       : super(windowId, platformDispatcher);

   @override
   double get devicePixelRatio =>
       _debugDevicePixelRatio ??
       EnginePlatformDispatcher.browserDevicePixelRatio;

   /// Overrides the default device pixel ratio.
   ///
   /// This is useful in tests to emulate screens of different dimensions.
   void debugOverrideDevicePixelRatio(double value) {
     _debugDevicePixelRatio = value;
   }

   double? _debugDevicePixelRatio;
 }

 /// A type of [FlutterView] that can be hosted inside of a [FlutterWindow].
 class EngineFlutterWindowView extends ui.FlutterWindow {
   EngineFlutterWindowView._(this._viewId, this.platformDispatcher);

   final Object _viewId;

   @override
   final ui.PlatformDispatcher platformDispatcher;

   @override
   ui.ViewConfiguration get viewConfiguration {
     final EnginePlatformDispatcher engineDispatcher =
         platformDispatcher as EnginePlatformDispatcher;
     assert(engineDispatcher.windowConfigurations.containsKey(_viewId));
     return engineDispatcher.windowConfigurations[_viewId] ??
         const ui.ViewConfiguration();
   }
 }

 /// The window singleton.
 ///
 /// `dart:ui` window delegates to this value. However, this value has a wider
 /// API surface, providing Web-specific functionality that the standard
 /// `dart:ui` version does not.
 final EngineSingletonFlutterWindow window =
     EngineSingletonFlutterWindow(0, EnginePlatformDispatcher.instance);

 /// The Web implementation of [ui.WindowPadding].
 class WindowPadding implements ui.WindowPadding {
   const WindowPadding({
     required this.left,
     required this.top,
     required this.right,
     required this.bottom,
   });

   @override
   final double left;
   @override
   final double top;
   @override
   final double right;
   @override
   final double bottom;
 }
	// 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.

	@JS()
	library window;

	import 'dart:async';
	import 'dart:html' as html;
	import 'dart:typed_data';

	import 'package:js/js.dart';
	import 'package:meta/meta.dart';
	import 'package:ui/ui.dart' as ui;

	import '../engine.dart' show registerHotRestartListener;
	import 'browser_detection.dart';
	import 'navigation/history.dart';
	import 'navigation/js_url_strategy.dart';
	import 'navigation/url_strategy.dart';
	import 'platform_dispatcher.dart';
	import 'services.dart';
	import 'test_embedding.dart';

	typedef _HandleMessageCallBack = Future<bool> Function();

	/// When set to true, all platform messages will be printed to the console.
	const bool debugPrintPlatformMessages = false;

	/// Whether [_customUrlStrategy] has been set or not.
	///
	/// It is valid to set [_customUrlStrategy] to null, so we can't use a null
	/// check to determine whether it was set or not. We need an extra boolean.
	bool _isUrlStrategySet = false;

	/// A custom URL strategy set by the app before running.
	UrlStrategy? _customUrlStrategy;
	set customUrlStrategy(UrlStrategy? strategy) {
	assert(!_isUrlStrategySet, 'Cannot set URL strategy more than once.');
	_isUrlStrategySet = true;
	_customUrlStrategy = strategy;
	}

	/// The Web implementation of [ui.SingletonFlutterWindow].
	class EngineFlutterWindow extends ui.SingletonFlutterWindow {
	EngineFlutterWindow(this._windowId, this.platformDispatcher) {
	final EnginePlatformDispatcher engineDispatcher =
	platformDispatcher as EnginePlatformDispatcher;
	engineDispatcher.windows[_windowId] = this;
	engineDispatcher.windowConfigurations[_windowId] = const ui.ViewConfiguration();
	if (_isUrlStrategySet) {
	_browserHistory =
	MultiEntriesBrowserHistory(urlStrategy: _customUrlStrategy);
	}
	registerHotRestartListener(() {
	window.resetHistory();
	});
	}

	final Object _windowId;

	@override
	final ui.PlatformDispatcher platformDispatcher;

	/// Handles the browser history integration to allow users to use the back
	/// button, etc.
	BrowserHistory get browserHistory {
	return _browserHistory ??=
	MultiEntriesBrowserHistory(urlStrategy: _urlStrategyForInitialization);
	}

	UrlStrategy? get _urlStrategyForInitialization {
	final UrlStrategy? urlStrategy =
	_isUrlStrategySet ? _customUrlStrategy : _createDefaultUrlStrategy();
	// Prevent any further customization of URL strategy.
	_isUrlStrategySet = true;
	return urlStrategy;
	}

	BrowserHistory?
	_browserHistory; // Must be either SingleEntryBrowserHistory or MultiEntriesBrowserHistory.

	Future<void> _useSingleEntryBrowserHistory() async {
	if (_browserHistory is SingleEntryBrowserHistory) {
	return;
	}

	final UrlStrategy? strategy;
	if (_browserHistory == null) {
	strategy = _urlStrategyForInitialization;
	} else {
	strategy = _browserHistory?.urlStrategy;
	await _browserHistory?.tearDown();
	}
	_browserHistory = SingleEntryBrowserHistory(urlStrategy: strategy);
	}

	Future<void> _useMultiEntryBrowserHistory() async {
	if (_browserHistory is MultiEntriesBrowserHistory) {
	return;
	}

	final UrlStrategy? strategy;
	if (_browserHistory == null) {
	strategy = _urlStrategyForInitialization;
	} else {
	strategy = _browserHistory?.urlStrategy;
	await _browserHistory?.tearDown();
	}
	_browserHistory = MultiEntriesBrowserHistory(urlStrategy: strategy);
	}

	@visibleForTesting
	Future<void> debugInitializeHistory(
	UrlStrategy? strategy, {
	required bool useSingle,
	}) async {
	// Prevent any further customization of URL strategy.
	_isUrlStrategySet = true;
	await _browserHistory?.tearDown();
	if (useSingle) {
	_browserHistory = SingleEntryBrowserHistory(urlStrategy: strategy);
	} else {
	_browserHistory = MultiEntriesBrowserHistory(urlStrategy: strategy);
	}
	}

	Future<void> resetHistory() async {
	await _browserHistory?.tearDown();
	_browserHistory = null;
	// Reset the globals too.
	_isUrlStrategySet = false;
	_customUrlStrategy = null;
	}

	Future<void> _endOfTheLine = Future<void>.value(null);

	Future<bool> _waitInTheLine(_HandleMessageCallBack callback) async {
	final Future<void> currentPosition = _endOfTheLine;
	final Completer<void> completer = Completer<void>();
	_endOfTheLine = completer.future;
	await currentPosition;
	bool result = false;
	try {
	result = await callback();
	} finally {
	completer.complete();
	}
	return result;
	}

	Future<bool> handleNavigationMessage(ByteData? data) async {
	return _waitInTheLine(() async {
	final MethodCall decoded = const JSONMethodCodec().decodeMethodCall(data);
	final Map<String, dynamic>? arguments = decoded.arguments;
	switch (decoded.method) {
	case 'selectMultiEntryHistory':
	await _useMultiEntryBrowserHistory();
	return true;
	case 'selectSingleEntryHistory':
	await _useSingleEntryBrowserHistory();
	return true;
	// the following cases assert that arguments are not null
	case 'routeUpdated': // deprecated
	assert(arguments != null);
	await _useSingleEntryBrowserHistory();
	browserHistory.setRouteName(arguments!['routeName']);
	return true;
	case 'routeInformationUpdated':
	assert(arguments != null);
	browserHistory.setRouteName(
	arguments!['location'],
	state: arguments['state'],
	replace: arguments['replace'] ?? false,
	);
	return true;
	}
	return false;
	});
	}

	@override
	ui.ViewConfiguration get viewConfiguration {
	final EnginePlatformDispatcher engineDispatcher =
	platformDispatcher as EnginePlatformDispatcher;
	assert(engineDispatcher.windowConfigurations.containsKey(_windowId));
	return engineDispatcher.windowConfigurations[_windowId] ??
	const ui.ViewConfiguration();
	}

	@override
	ui.Size get physicalSize {
	if (_physicalSize == null) {
	computePhysicalSize();
	}
	assert(_physicalSize != null);
	return _physicalSize!;
	}

	/// Computes the physical size of the screen from [html.window].
	///
	/// This function is expensive. It triggers browser layout if there are
	/// pending DOM writes.
	void computePhysicalSize() {
	bool override = false;

	assert(() {
	if (webOnlyDebugPhysicalSizeOverride != null) {
	_physicalSize = webOnlyDebugPhysicalSizeOverride;
	override = true;
	}
	return true;
	}());

	if (!override) {
	double windowInnerWidth;
	double windowInnerHeight;
	final html.VisualViewport? viewport = html.window.visualViewport;

	if (viewport != null) {
	if (operatingSystem == OperatingSystem.iOs) {
	/// Chrome on iOS reports incorrect viewport.height when app
	/// starts in portrait orientation and the phone is rotated to
	/// landscape.
	///
	/// We instead use documentElement clientWidth/Height to read
	/// accurate physical size. VisualViewport api is only used during
	/// text editing to make sure inset is correctly reported to
	/// framework.
	final double docWidth =
	html.document.documentElement!.clientWidth.toDouble();
	final double docHeight =
	html.document.documentElement!.clientHeight.toDouble();
	windowInnerWidth = docWidth * devicePixelRatio;
	windowInnerHeight = docHeight * devicePixelRatio;
	} else {
	windowInnerWidth = viewport.width!.toDouble() * devicePixelRatio;
	windowInnerHeight = viewport.height!.toDouble() * devicePixelRatio;
	}
	} else {
	windowInnerWidth = html.window.innerWidth! * devicePixelRatio;
	windowInnerHeight = html.window.innerHeight! * devicePixelRatio;
	}
	_physicalSize = ui.Size(
	windowInnerWidth,
	windowInnerHeight,
	);
	}
	}

	/// Forces the window to recompute its physical size. Useful for tests.
	void debugForceResize() {
	computePhysicalSize();
	}

	void computeOnScreenKeyboardInsets(bool isEditingOnMobile) {
	double windowInnerHeight;
	final html.VisualViewport? viewport = html.window.visualViewport;
	if (viewport != null) {
	if (operatingSystem == OperatingSystem.iOs && !isEditingOnMobile) {
	windowInnerHeight =
	html.document.documentElement!.clientHeight * devicePixelRatio;
	} else {
	windowInnerHeight = viewport.height!.toDouble() * devicePixelRatio;
	}
	} else {
	windowInnerHeight = html.window.innerHeight! * devicePixelRatio;
	}
	final double bottomPadding = _physicalSize!.height - windowInnerHeight;
	_viewInsets =
	WindowPadding(bottom: bottomPadding, left: 0, right: 0, top: 0);
	}

	/// Uses the previous physical size and current innerHeight/innerWidth
	/// values to decide if a device is rotating.
	///
	/// During a rotation the height and width values will (almost) swap place.
	/// Values can slightly differ due to space occupied by the browser header.
	/// For example the following values are collected for Pixel 3 rotation:
	///
	/// height: 658 width: 393
	/// new height: 313 new width: 738
	///
	/// The following values are from a changed caused by virtual keyboard.
	///
	/// height: 658 width: 393
	/// height: 368 width: 393
	bool isRotation() {
	double height = 0;
	double width = 0;
	if (html.window.visualViewport != null) {
	height =
	html.window.visualViewport!.height!.toDouble() * devicePixelRatio;
	width = html.window.visualViewport!.width!.toDouble() * devicePixelRatio;
	} else {
	height = html.window.innerHeight! * devicePixelRatio;
	width = html.window.innerWidth! * devicePixelRatio;
	}

	// This method compares the new dimensions with the previous ones.
	// Return false if the previous dimensions are not set.
	if (_physicalSize != null) {
	// First confirm both height and width are effected.
	if (_physicalSize!.height != height && _physicalSize!.width != width) {
	// If prior to rotation height is bigger than width it should be the
	// opposite after the rotation and vice versa.
	if ((_physicalSize!.height > _physicalSize!.width && height < width) \|\|
	(_physicalSize!.width > _physicalSize!.height && width < height)) {
	// Rotation detected
	return true;
	}
	}
	}
	return false;
	}

	@override
	WindowPadding get viewInsets => _viewInsets;
	WindowPadding _viewInsets = ui.WindowPadding.zero as WindowPadding;

	/// Lazily populated and cleared at the end of the frame.
	ui.Size? _physicalSize;

	/// Overrides the value of [physicalSize] in tests.
	ui.Size? webOnlyDebugPhysicalSizeOverride;
	}

	typedef _JsSetUrlStrategy = void Function(JsUrlStrategy?);

	/// A JavaScript hook to customize the URL strategy of a Flutter app.
	//
	// Keep this js name in sync with flutter_web_plugins. Find it at:
	// https://github.com/flutter/flutter/blob/custom_location_strategy/packages/flutter_web_plugins/lib/src/navigation/js_url_strategy.dart
	//
	// TODO: Add integration test https://github.com/flutter/flutter/issues/66852
	@JS('_flutter_web_set_location_strategy')
	external set jsSetUrlStrategy(_JsSetUrlStrategy? newJsSetUrlStrategy);

	UrlStrategy? _createDefaultUrlStrategy() {
	return ui.debugEmulateFlutterTesterEnvironment
	? TestUrlStrategy.fromEntry(const TestHistoryEntry('default', null, '/'))
	: const HashUrlStrategy();
	}

	/// The Web implementation of [ui.SingletonFlutterWindow].
	class EngineSingletonFlutterWindow extends EngineFlutterWindow {
	EngineSingletonFlutterWindow(
	Object windowId, ui.PlatformDispatcher platformDispatcher)
	: super(windowId, platformDispatcher);

	@override
	double get devicePixelRatio =>
	_debugDevicePixelRatio ??
	EnginePlatformDispatcher.browserDevicePixelRatio;

	/// Overrides the default device pixel ratio.
	///
	/// This is useful in tests to emulate screens of different dimensions.
	void debugOverrideDevicePixelRatio(double value) {
	_debugDevicePixelRatio = value;
	}

	double? _debugDevicePixelRatio;
	}

	/// A type of [FlutterView] that can be hosted inside of a [FlutterWindow].
	class EngineFlutterWindowView extends ui.FlutterWindow {
	EngineFlutterWindowView._(this._viewId, this.platformDispatcher);

	final Object _viewId;

	@override
	final ui.PlatformDispatcher platformDispatcher;

	@override
	ui.ViewConfiguration get viewConfiguration {
	final EnginePlatformDispatcher engineDispatcher =
	platformDispatcher as EnginePlatformDispatcher;
	assert(engineDispatcher.windowConfigurations.containsKey(_viewId));
	return engineDispatcher.windowConfigurations[_viewId] ??
	const ui.ViewConfiguration();
	}
	}

	/// The window singleton.
	///
	/// `dart:ui` window delegates to this value. However, this value has a wider
	/// API surface, providing Web-specific functionality that the standard
	/// `dart:ui` version does not.
	final EngineSingletonFlutterWindow window =
	EngineSingletonFlutterWindow(0, EnginePlatformDispatcher.instance);

	/// The Web implementation of [ui.WindowPadding].
	class WindowPadding implements ui.WindowPadding {
	const WindowPadding({
	required this.left,
	required this.top,
	required this.right,
	required this.bottom,
	});

	@override
	final double left;
	@override
	final double top;
	@override
	final double right;
	@override
	final double bottom;
	}