Enable dependency injection of Window instead of using static property (#27389)

dev/benchmarks/microbenchmarks/lib/stocks/layout_bench.dart

@@ -32,8 +32,14 @@ Future<void> main() async {
     await tester.pump(); // Start drawer animation
     await tester.pump(const Duration(seconds: 1)); // Complete drawer animation
 
-    final TestViewConfiguration big = TestViewConfiguration(size: const Size(360.0, 640.0));
+    final TestViewConfiguration big = TestViewConfiguration(
-    final TestViewConfiguration small = TestViewConfiguration(size: const Size(355.0, 635.0));
+      size: const Size(360.0, 640.0),
+      window: RendererBinding.instance.window,
+    );
+    final TestViewConfiguration small = TestViewConfiguration(
+      size: const Size(355.0, 635.0),
+      window: RendererBinding.instance.window,
+    );
     final RenderView renderView = WidgetsBinding.instance.renderView;
     binding.framePolicy = LiveTestWidgetsFlutterBindingFramePolicy.benchmark;
 

packages/flutter/lib/src/foundation/binding.dart

@@ -6,7 +6,8 @@ import 'dart:async';
 import 'dart:convert' show json;
 import 'dart:developer' as developer;
 import 'dart:io' show exit;
-import 'dart:ui' show saveCompilationTrace;
+// Before adding any more dart:ui imports, pleaes read the README.
+import 'dart:ui' as ui show saveCompilationTrace, Window, window;
 
 import 'package:meta/meta.dart';
 
@@ -66,6 +67,24 @@ abstract class BindingBase {
   static bool _debugInitialized = false;
   static bool _debugServiceExtensionsRegistered = false;
 
+  /// The window to which this binding is bound.
+  ///
+  /// A number of additional bindings are defined as extensions of [BindingBase],
+  /// e.g., [ServicesBinding], [RendererBinding], and [WidgetsBinding]. Each of
+  /// these bindings define behaviors that interact with a [ui.Window], e.g.,
+  /// [ServicesBinding] registers a [ui.Window.onPlatformMessage] handler, and
+  /// [RendererBinding] registers [ui.Window.onMetricsChanged],
+  /// [ui.Window.onTextScaleFactorChanged], [ui.Window.onSemanticsEnabledChanged],
+  /// and [ui.Window.onSemanticsAction] handlers.
+  ///
+  /// Each of these other bindings could individually access a [Window] statically,
+  /// but that would preclude the ability to test these behaviors with a fake
+  /// window for verification purposes.  Therefore, [BindingBase] exposes this
+  /// [Window] for use by other bindings.  A subclass of [BindingBase], such as
+  /// [TestWidgetsFlutterBinding], can override this accessor to return a
+  /// different [Window] implementation, such as a [TestWindow].
+  ui.Window get window => ui.window;
+
   /// The initialization method. Subclasses override this method to hook into
   /// the platform and otherwise configure their services. Subclasses must call
   /// "super.initInstances()".
@@ -122,7 +141,7 @@ abstract class BindingBase {
         name: 'saveCompilationTrace',
         callback: (Map<String, String> parameters) async {
           return <String, dynamic> {
-            'value': saveCompilationTrace(),
+            'value': ui.saveCompilationTrace(),
           };
         }
       );

packages/flutter/lib/src/gestures/binding.dart

@@ -4,7 +4,7 @@
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:ui' as ui show window, PointerDataPacket;
+import 'dart:ui' as ui show PointerDataPacket;
 
 import 'package:flutter/foundation.dart';
 
@@ -62,7 +62,7 @@ mixin GestureBinding on BindingBase implements HitTestable, HitTestDispatcher, H
   void initInstances() {
     super.initInstances();
     _instance = this;
-    ui.window.onPointerDataPacket = _handlePointerDataPacket;
+    window.onPointerDataPacket = _handlePointerDataPacket;
   }
 
   @override
@@ -80,7 +80,7 @@ mixin GestureBinding on BindingBase implements HitTestable, HitTestDispatcher, H
   void _handlePointerDataPacket(ui.PointerDataPacket packet) {
     // We convert pointer data to logical pixels so that e.g. the touch slop can be
     // defined in a device-independent manner.
-    _pendingPointerEvents.addAll(PointerEventConverter.expand(packet.data, ui.window.devicePixelRatio));
+    _pendingPointerEvents.addAll(PointerEventConverter.expand(packet.data, window.devicePixelRatio));
     if (!locked)
       _flushPointerEventQueue();
   }

packages/flutter/lib/src/rendering/binding.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:developer';
 import 'dart:typed_data';
-import 'dart:ui' as ui show window;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -31,7 +30,7 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
       onSemanticsOwnerCreated: _handleSemanticsOwnerCreated,
       onSemanticsOwnerDisposed: _handleSemanticsOwnerDisposed,
     );
-    ui.window
+    window
       ..onMetricsChanged = handleMetricsChanged
       ..onTextScaleFactorChanged = handleTextScaleFactorChanged
       ..onSemanticsEnabledChanged = _handleSemanticsEnabledChanged
@@ -131,7 +130,7 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
   /// Called automatically when the binding is created.
   void initRenderView() {
     assert(renderView == null);
-    renderView = RenderView(configuration: createViewConfiguration());
+    renderView = RenderView(configuration: createViewConfiguration(), window: window);
     renderView.scheduleInitialFrame();
   }
 
@@ -181,9 +180,9 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
   /// this to force the display into 800x600 when a test is run on the device
   /// using `flutter run`.
   ViewConfiguration createViewConfiguration() {
-    final double devicePixelRatio = ui.window.devicePixelRatio;
+    final double devicePixelRatio = window.devicePixelRatio;
     return ViewConfiguration(
-      size: ui.window.physicalSize / devicePixelRatio,
+      size: window.physicalSize / devicePixelRatio,
       devicePixelRatio: devicePixelRatio,
     );
   }
@@ -198,12 +197,12 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
       // the logical coordinates of the event location back to device pixels
       // here.
       return renderView.layer
-          .find<MouseTrackerAnnotation>(offset * ui.window.devicePixelRatio);
+          .find<MouseTrackerAnnotation>(offset * window.devicePixelRatio);
     });
   }
 
   void _handleSemanticsEnabledChanged() {
-    setSemanticsEnabled(ui.window.semanticsEnabled);
+    setSemanticsEnabled(window.semanticsEnabled);
   }
 
   /// Whether the render tree associated with this binding should produce a tree

packages/flutter/lib/src/rendering/view.dart

@@ -4,7 +4,7 @@
 
 import 'dart:developer';
 import 'dart:io' show Platform;
-import 'dart:ui' as ui show Scene, SceneBuilder, window;
+import 'dart:ui' as ui show Scene, SceneBuilder, Window;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
@@ -56,8 +56,10 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
   RenderView({
     RenderBox child,
     @required ViewConfiguration configuration,
+    @required ui.Window window,
   }) : assert(configuration != null),
-       _configuration = configuration {
+       _configuration = configuration,
+       _window = window {
     this.child = child;
   }
 
@@ -82,6 +84,8 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
     markNeedsLayout();
   }
 
+  ui.Window _window;
+
   /// Whether Flutter should automatically compute the desired system UI.
   ///
   /// When this setting is enabled, Flutter will hit-test the layer tree at the
@@ -195,7 +199,7 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
       final ui.Scene scene = layer.buildScene(builder);
       if (automaticSystemUiAdjustment)
         _updateSystemChrome();
-      ui.window.render(scene);
+      _window.render(scene);
       scene.dispose();
       assert(() {
         if (debugRepaintRainbowEnabled || debugRepaintTextRainbowEnabled)
@@ -209,8 +213,8 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
 
   void _updateSystemChrome() {
     final Rect bounds = paintBounds;
-    final Offset top = Offset(bounds.center.dx, ui.window.padding.top / ui.window.devicePixelRatio);
+    final Offset top = Offset(bounds.center.dx, _window.padding.top / _window.devicePixelRatio);
-    final Offset bottom = Offset(bounds.center.dx, bounds.center.dy - ui.window.padding.bottom / ui.window.devicePixelRatio);
+    final Offset bottom = Offset(bounds.center.dx, bounds.center.dy - _window.padding.bottom / _window.devicePixelRatio);
     final SystemUiOverlayStyle upperOverlayStyle = layer.find<SystemUiOverlayStyle>(top);
     // Only android has a customizable system navigation bar.
     SystemUiOverlayStyle lowerOverlayStyle;
@@ -254,10 +258,10 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
       properties.add(DiagnosticsNode.message('debug mode enabled - ${Platform.operatingSystem}'));
       return true;
     }());
-    properties.add(DiagnosticsProperty<Size>('window size', ui.window.physicalSize, tooltip: 'in physical pixels'));
+    properties.add(DiagnosticsProperty<Size>('window size', _window.physicalSize, tooltip: 'in physical pixels'));
-    properties.add(DoubleProperty('device pixel ratio', ui.window.devicePixelRatio, tooltip: 'physical pixels per logical pixel'));
+    properties.add(DoubleProperty('device pixel ratio', _window.devicePixelRatio, tooltip: 'physical pixels per logical pixel'));
     properties.add(DiagnosticsProperty<ViewConfiguration>('configuration', configuration, tooltip: 'in logical pixels'));
-    if (ui.window.semanticsEnabled)
+    if (_window.semanticsEnabled)
       properties.add(DiagnosticsNode.message('semantics enabled'));
   }
 }

packages/flutter/lib/src/scheduler/binding.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:collection';
 import 'dart:developer';
-import 'dart:ui' as ui show window;
 import 'dart:ui' show AppLifecycleState;
 
 import 'package:collection/collection.dart' show PriorityQueue, HeapPriorityQueue;
@@ -191,8 +190,8 @@ mixin SchedulerBinding on BindingBase, ServicesBinding {
   void initInstances() {
     super.initInstances();
     _instance = this;
-    ui.window.onBeginFrame = _handleBeginFrame;
+    window.onBeginFrame = _handleBeginFrame;
-    ui.window.onDrawFrame = _handleDrawFrame;
+    window.onDrawFrame = _handleDrawFrame;
     SystemChannels.lifecycle.setMessageHandler(_handleLifecycleMessage);
   }
 
@@ -682,7 +681,7 @@ mixin SchedulerBinding on BindingBase, ServicesBinding {
         debugPrintStack(label: 'scheduleFrame() called. Current phase is $schedulerPhase.');
       return true;
     }());
-    ui.window.scheduleFrame();
+    window.scheduleFrame();
     _hasScheduledFrame = true;
   }
 
@@ -713,7 +712,7 @@ mixin SchedulerBinding on BindingBase, ServicesBinding {
         debugPrintStack(label: 'scheduleForcedFrame() called. Current phase is $schedulerPhase.');
       return true;
     }());
-    ui.window.scheduleFrame();
+    window.scheduleFrame();
     _hasScheduledFrame = true;
   }
 

packages/flutter/lib/src/semantics/binding.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:ui' as ui show AccessibilityFeatures, window;
+import 'dart:ui' as ui show AccessibilityFeatures;
 
 import 'package:flutter/foundation.dart';
 
@@ -21,7 +21,7 @@ mixin SemanticsBinding on BindingBase {
   void initInstances() {
     super.initInstances();
     _instance = this;
-    _accessibilityFeatures = ui.window.accessibilityFeatures;
+    _accessibilityFeatures = window.accessibilityFeatures;
   }
 
   /// Called when the platform accessibility features change.
@@ -29,7 +29,7 @@ mixin SemanticsBinding on BindingBase {
   /// See [Window.onAccessibilityFeaturesChanged].
   @protected
   void handleAccessibilityFeaturesChanged() {
-    _accessibilityFeatures = ui.window.accessibilityFeatures;
+    _accessibilityFeatures = window.accessibilityFeatures;
   }
 
   /// The currently active set of [AccessibilityFeatures].

packages/flutter/lib/src/semantics/semantics.dart

@@ -13,6 +13,7 @@ import 'package:flutter/painting.dart' show MatrixUtils, TransformProperty;
 import 'package:flutter/services.dart';
 import 'package:vector_math/vector_math_64.dart';
 
+import 'binding.dart' show SemanticsBinding;
 import 'semantics_event.dart';
 
 export 'dart:ui' show SemanticsAction;
@@ -2473,7 +2474,7 @@ class SemanticsOwner extends ChangeNotifier {
       final CustomSemanticsAction action = CustomSemanticsAction.getAction(actionId);
       builder.updateCustomAction(id: actionId, label: action.label, hint: action.hint, overrideId: action.action?.index ?? -1);
     }
-    ui.window.updateSemantics(builder.build());
+    SemanticsBinding.instance.window.updateSemantics(builder.build());
     notifyListeners();
   }
 

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

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
 
@@ -20,11 +19,16 @@ mixin ServicesBinding on BindingBase {
   @override
   void initInstances() {
     super.initInstances();
-    ui.window
+    _instance = this;
+    window
       ..onPlatformMessage = BinaryMessages.handlePlatformMessage;
     initLicenses();
   }
 
+  /// The current [ServicesBinding], if one has been created.
+  static ServicesBinding get instance => _instance;
+  static ServicesBinding _instance;
+
   /// Adds relevant licenses to the [LicenseRegistry].
   ///
   /// By default, the [ServicesBinding]'s implementation of [initLicenses] adds

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

@@ -8,6 +8,7 @@ import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
 
+import 'binding.dart' show ServicesBinding;
 import 'platform_channel.dart';
 
 typedef _MessageHandler = Future<ByteData> Function(ByteData message);
@@ -36,7 +37,7 @@ class BinaryMessages {
 
   static Future<ByteData> _sendPlatformMessage(String channel, ByteData message) {
     final Completer<ByteData> completer = Completer<ByteData>();
-    ui.window.sendPlatformMessage(channel, message, (ByteData reply) {
+    ServicesBinding.instance.window.sendPlatformMessage(channel, message, (ByteData reply) {
       try {
         completer.complete(reply);
       } catch (exception, stack) {

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

@@ -4,7 +4,6 @@
 
 import 'dart:async';
 import 'dart:collection' show HashMap;
-import 'dart:ui' as ui show window;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
@@ -710,7 +709,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
   void initState() {
     super.initState();
     _updateNavigator();
-    _locale = _resolveLocales(ui.window.locales, widget.supportedLocales);
+    _locale = _resolveLocales(WidgetsBinding.instance.window.locales, widget.supportedLocales);
     WidgetsBinding.instance.addObserver(this);
   }
 
@@ -996,7 +995,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
   @override
   void didChangeAccessibilityFeatures() {
     setState(() {
-      // The properties of ui.window have changed. We use them in our build
+      // The properties of window have changed. We use them in our build
       // function, so we need setState(), but we don't cache anything locally.
     });
   }
@@ -1007,7 +1006,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
   @override
   void didChangeMetrics() {
     setState(() {
-      // The properties of ui.window have changed. We use them in our build
+      // The properties of window have changed. We use them in our build
       // function, so we need setState(), but we don't cache anything locally.
     });
   }
@@ -1015,8 +1014,8 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
   @override
   void didChangeTextScaleFactor() {
     setState(() {
-      // The textScaleFactor property of ui.window has changed. We reference
+      // The textScaleFactor property of window has changed. We reference
-      // ui.window in our build function, so we need to call setState(), but
+      // window in our build function, so we need to call setState(), but
       // we don't need to cache anything locally.
     });
   }
@@ -1077,12 +1076,12 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
     if (_navigator != null) {
       navigator = Navigator(
         key: _navigator,
-        // If ui.window.defaultRouteName isn't '/', we should assume it was set
+        // If window.defaultRouteName isn't '/', we should assume it was set
         // intentionally via `setInitialRoute`, and should override whatever
         // is in [widget.initialRoute].
-        initialRoute: ui.window.defaultRouteName != Navigator.defaultRouteName
+        initialRoute: WidgetsBinding.instance.window.defaultRouteName != Navigator.defaultRouteName
-            ? ui.window.defaultRouteName
+            ? WidgetsBinding.instance.window.defaultRouteName
-            : widget.initialRoute ?? ui.window.defaultRouteName,
+            : widget.initialRoute ?? WidgetsBinding.instance.window.defaultRouteName,
         onGenerateRoute: _onGenerateRoute,
         onUnknownRoute: _onUnknownRoute,
         observers: widget.navigatorObservers,
@@ -1183,7 +1182,7 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
     assert(_debugCheckLocalizations(appLocale));
 
     return MediaQuery(
-      data: MediaQueryData.fromWindow(ui.window),
+      data: MediaQueryData.fromWindow(WidgetsBinding.instance.window),
       child: Localizations(
         locale: appLocale,
         delegates: _localizationsDelegates.toList(),

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

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:developer' as developer;
 import 'dart:ui' show AppLifecycleState, Locale, AccessibilityFeatures;
-import 'dart:ui' as ui show window;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -141,7 +140,7 @@ abstract class WidgetsBindingObserver {
   ///
   ///   @override
   ///   void didChangeMetrics() {
-  ///     setState(() { _lastSize = ui.window.physicalSize; });
+  ///     setState(() { _lastSize = WidgetsBinding.instance.window.physicalSize; });
   ///   }
   ///
   ///   @override
@@ -197,7 +196,7 @@ abstract class WidgetsBindingObserver {
   ///
   ///   @override
   ///   void didChangeTextScaleFactor() {
-  ///     setState(() { _lastTextScaleFactor = ui.window.textScaleFactor; });
+  ///     setState(() { _lastTextScaleFactor = WidgetsBinding.instance.window.textScaleFactor; });
   ///   }
   ///
   ///   @override
@@ -250,8 +249,8 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
     super.initInstances();
     _instance = this;
     buildOwner.onBuildScheduled = _handleBuildScheduled;
-    ui.window.onLocaleChanged = handleLocaleChanged;
+    window.onLocaleChanged = handleLocaleChanged;
-    ui.window.onAccessibilityFeaturesChanged = handleAccessibilityFeaturesChanged;
+    window.onAccessibilityFeaturesChanged = handleAccessibilityFeaturesChanged;
     SystemChannels.navigation.setMethodCallHandler(_handleNavigationInvocation);
     SystemChannels.system.setMessageHandler(_handleSystemMessage);
   }
@@ -424,7 +423,7 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
   @protected
   @mustCallSuper
   void handleLocaleChanged() {
-    dispatchLocalesChanged(ui.window.locales);
+    dispatchLocalesChanged(window.locales);
   }
 
   /// Notify all the observers that the locale has changed (using

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

@@ -980,10 +980,10 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
 
   @override
   void didChangeMetrics() {
-    if (_lastBottomViewInset < ui.window.viewInsets.bottom) {
+    if (_lastBottomViewInset < WidgetsBinding.instance.window.viewInsets.bottom) {
       _showCaretOnScreen();
     }
-    _lastBottomViewInset = ui.window.viewInsets.bottom;
+    _lastBottomViewInset = WidgetsBinding.instance.window.viewInsets.bottom;
   }
 
   void _formatAndSetValue(TextEditingValue value) {
@@ -1102,7 +1102,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     if (_hasFocus) {
       // Listen for changing viewInsets, which indicates keyboard showing up.
       WidgetsBinding.instance.addObserver(this);
-      _lastBottomViewInset = ui.window.viewInsets.bottom;
+      _lastBottomViewInset = WidgetsBinding.instance.window.viewInsets.bottom;
       _showCaretOnScreen();
       if (!_value.selection.isValid) {
         // Place cursor at the end if the selection is invalid when we receive focus.

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

@@ -3,12 +3,12 @@
 // found in the LICENSE file.
 
 import 'dart:math' as math;
-import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/physics.dart';
 
+import 'binding.dart' show WidgetsBinding;
 import 'overscroll_indicator.dart';
 import 'scroll_metrics.dart';
 import 'scroll_simulation.dart';
@@ -174,8 +174,8 @@ class ScrollPhysics {
   static final Tolerance _kDefaultTolerance = Tolerance(
     // TODO(ianh): Handle the case of the device pixel ratio changing.
     // TODO(ianh): Get this from the local MediaQuery not dart:ui's window object.
-    velocity: 1.0 / (0.050 * ui.window.devicePixelRatio), // logical pixels per second
+    velocity: 1.0 / (0.050 * WidgetsBinding.instance.window.devicePixelRatio), // logical pixels per second
-    distance: 1.0 / ui.window.devicePixelRatio // logical pixels
+    distance: 1.0 / WidgetsBinding.instance.window.devicePixelRatio // logical pixels
   );
 
   /// The tolerance to use for ballistic simulations.

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

@@ -4,7 +4,6 @@
 
 import 'dart:math' as math;
 import 'dart:ui' show SemanticsFlag;
-import 'dart:ui' as ui show window;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
@@ -89,7 +88,7 @@ class _SemanticsDebuggerState extends State<SemanticsDebugger> with WidgetsBindi
   Offset _lastPointerDownLocation;
   void _handlePointerDown(PointerDownEvent event) {
     setState(() {
-      _lastPointerDownLocation = event.position * ui.window.devicePixelRatio;
+      _lastPointerDownLocation = event.position * WidgetsBinding.instance.window.devicePixelRatio;
     });
     // TODO(ianh): Use a gesture recognizer so that we can reset the
     // _lastPointerDownLocation when none of the other gesture recognizers win.
@@ -150,7 +149,7 @@ class _SemanticsDebuggerState extends State<SemanticsDebugger> with WidgetsBindi
         _pipelineOwner,
         _client.generation,
         _lastPointerDownLocation, // in physical pixels
-        ui.window.devicePixelRatio,
+        WidgetsBinding.instance.window.devicePixelRatio,
       ),
       child: GestureDetector(
         behavior: HitTestBehavior.opaque,

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

@@ -10,7 +10,6 @@ import 'dart:math' as math;
 import 'dart:typed_data';
 import 'dart:ui' as ui
     show
-        window,
         ClipOp,
         EngineLayer,
         Image,
@@ -2294,7 +2293,7 @@ class _WidgetInspectorState extends State<WidgetInspector>
     // on the edge of the display. If the pointer is being dragged off the edge
     // of the display we do not want to select anything. A user can still select
     // a widget that is only at the exact screen margin by tapping.
-    final Rect bounds = (Offset.zero & (ui.window.physicalSize / ui.window.devicePixelRatio)).deflate(_kOffScreenMargin);
+    final Rect bounds = (Offset.zero & (WidgetsBinding.instance.window.physicalSize / WidgetsBinding.instance.window.devicePixelRatio)).deflate(_kOffScreenMargin);
     if (!bounds.contains(_lastPointerLocation)) {
       setState(() {
         selection.clear();

packages/flutter/test/rendering/independent_layout_test.dart

@@ -44,7 +44,7 @@ void main() {
     expect(offscreen.child.hasSize, isFalse);
     expect(offscreen.painted, isFalse);
     // Attach the offscreen to a custom render view and owner
-    final RenderView renderView = RenderView(configuration: testConfiguration);
+    final RenderView renderView = RenderView(configuration: testConfiguration, window: null);
     final PipelineOwner pipelineOwner = PipelineOwner();
     renderView.attach(pipelineOwner);
     renderView.child = offscreen.root;
@@ -73,7 +73,7 @@ void main() {
     expect(offscreen.child.hasSize, isFalse);
     expect(offscreen.painted, isFalse);
     // Attach the offscreen to a custom render view and owner
-    final RenderView renderView = RenderView(configuration: testConfiguration);
+    final RenderView renderView = RenderView(configuration: testConfiguration, window: null);
     final PipelineOwner pipelineOwner = PipelineOwner();
     renderView.attach(pipelineOwner);
     renderView.child = offscreen.root;

packages/flutter/test/rendering/object_test.dart

@@ -4,10 +4,14 @@
 
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
-import '../flutter_test_alternative.dart';
+import 'package:flutter_test/src/binding.dart' show TestWidgetsFlutterBinding;
+import 'package:flutter_test/flutter_test.dart';
 
 void main() {
   test('ensure frame is scheduled for markNeedsSemanticsUpdate', () {
+    // Initialize all bindings because owner.flushSemantics() requires a window
+    TestWidgetsFlutterBinding.ensureInitialized();
+
     final TestRenderObject renderObject = TestRenderObject();
     int onNeedVisualUpdateCallCount = 0;
     final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () {

packages/flutter/test/services/platform_messages_test.dart

@@ -5,10 +5,13 @@
 import 'dart:typed_data';
 
 import 'package:flutter/services.dart';
-import '../flutter_test_alternative.dart';
+import 'package:flutter_test/flutter_test.dart';
 
 void main() {
   test('Mock binary message handler control test', () async {
+    // Initialize all bindings because BinaryMessages.send() needs a window.
+    TestWidgetsFlutterBinding.ensureInitialized();
+
     final List<ByteData> log = <ByteData>[];
 
     BinaryMessages.setMockMessageHandler('test1', (ByteData message) async {

packages/flutter/test/widgets/independent_widget_layout_test.dart

@@ -9,7 +9,10 @@ import 'package:flutter/rendering.dart';
 const Size _kTestViewSize = Size(800.0, 600.0);
 
 class OffscreenRenderView extends RenderView {
-  OffscreenRenderView() : super(configuration: const ViewConfiguration(size: _kTestViewSize));
+  OffscreenRenderView() : super(
+    configuration: const ViewConfiguration(size: _kTestViewSize),
+    window: WidgetsBinding.instance.window,
+  );
 
   @override
   void compositeFrame() {

packages/flutter/test/widgets/media_query_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:ui' as ui;
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
@@ -39,10 +37,10 @@ void main() {
   });
 
   testWidgets('MediaQueryData is sane', (WidgetTester tester) async {
-    final MediaQueryData data = MediaQueryData.fromWindow(ui.window);
+    final MediaQueryData data = MediaQueryData.fromWindow(WidgetsBinding.instance.window);
     expect(data, hasOneLineDescription);
     expect(data.hashCode, equals(data.copyWith().hashCode));
-    expect(data.size, equals(ui.window.physicalSize / ui.window.devicePixelRatio));
+    expect(data.size, equals(WidgetsBinding.instance.window.physicalSize / WidgetsBinding.instance.window.devicePixelRatio));
     expect(data.accessibleNavigation, false);
     expect(data.invertColors, false);
     expect(data.disableAnimations, false);
@@ -50,7 +48,7 @@ void main() {
   });
 
   testWidgets('MediaQueryData.copyWith defaults to source', (WidgetTester tester) async {
-    final MediaQueryData data = MediaQueryData.fromWindow(ui.window);
+    final MediaQueryData data = MediaQueryData.fromWindow(WidgetsBinding.instance.window);
     final MediaQueryData copied = data.copyWith();
     expect(copied.size, data.size);
     expect(copied.devicePixelRatio, data.devicePixelRatio);
@@ -65,7 +63,7 @@ void main() {
   });
 
   testWidgets('MediaQuery.copyWith copies specified values', (WidgetTester tester) async {
-    final MediaQueryData data = MediaQueryData.fromWindow(ui.window);
+    final MediaQueryData data = MediaQueryData.fromWindow(WidgetsBinding.instance.window);
     final MediaQueryData copied = data.copyWith(
       size: const Size(3.14, 2.72),
       devicePixelRatio: 1.41,

packages/flutter_test/lib/flutter_test.dart

@@ -62,3 +62,4 @@ export 'src/test_pointer.dart';
 export 'src/test_text_input.dart';
 export 'src/test_vsync.dart';
 export 'src/widget_tester.dart';
+export 'src/window.dart';

packages/flutter_test/lib/src/accessibility.dart

@@ -108,11 +108,11 @@ class MinimumTapTargetGuideline extends AccessibilityGuideline {
       const double delta = 0.001;
       if (paintBounds.left <= delta
         || paintBounds.top <= delta
-        || (paintBounds.bottom - ui.window.physicalSize.height).abs() <= delta
+        || (paintBounds.bottom - tester.binding.window.physicalSize.height).abs() <= delta
-        || (paintBounds.right - ui.window.physicalSize.width).abs() <= delta)
+        || (paintBounds.right - tester.binding.window.physicalSize.width).abs() <= delta)
         return result;
       // shrink by device pixel ratio.
-      final Size candidateSize = paintBounds.size / ui.window.devicePixelRatio;
+      final Size candidateSize = paintBounds.size / tester.binding.window.devicePixelRatio;
       if (candidateSize.width < size.width || candidateSize.height < size.height)
         result += Evaluation.fail(
           '$node: expected tap target size of at least $size, but found $candidateSize\n'

packages/flutter_test/lib/src/binding.dart

@@ -13,6 +13,7 @@ import 'package:flutter/rendering.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart' show TestWindow;
 import 'package:quiver/testing/async.dart';
 import 'package:quiver/time.dart';
 import 'package:test_api/test_api.dart' as test_package;
@@ -96,12 +97,16 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
   ///
   /// This constructor overrides the [debugPrint] global hook to point to
   /// [debugPrintOverride], which can be overridden by subclasses.
-  TestWidgetsFlutterBinding() {
+  TestWidgetsFlutterBinding() : _window = TestWindow(window: ui.window) {
     debugPrint = debugPrintOverride;
     debugDisableShadows = disableShadows;
     debugCheckIntrinsicSizes = checkIntrinsicSizes;
   }
 
+  @override
+  TestWindow get window => _window;
+  final TestWindow _window;
+
   /// The value to set [debugPrint] to while tests are running.
   ///
   /// This can be used to redirect console output from the framework, or to
@@ -265,8 +270,8 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
 
   @override
   ViewConfiguration createViewConfiguration() {
-    final double devicePixelRatio = ui.window.devicePixelRatio;
+    final double devicePixelRatio = window.devicePixelRatio;
-    final Size size = _surfaceSize ?? ui.window.physicalSize / devicePixelRatio;
+    final Size size = _surfaceSize ?? window.physicalSize / devicePixelRatio;
     return ViewConfiguration(
       size: size,
       devicePixelRatio: devicePixelRatio,
@@ -665,8 +670,8 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
   @override
   void initInstances() {
     super.initInstances();
-    ui.window.onBeginFrame = null;
+    window.onBeginFrame = null;
-    ui.window.onDrawFrame = null;
+    window.onDrawFrame = null;
   }
 
   FakeAsync _currentFakeAsync; // set in runTest; cleared in postTest
@@ -1145,7 +1150,7 @@ class LiveTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
       _pendingFrame = null;
       _expectingFrame = false;
     } else if (framePolicy != LiveTestWidgetsFlutterBindingFramePolicy.benchmark) {
-      ui.window.scheduleFrame();
+      window.scheduleFrame();
     }
   }
 
@@ -1155,6 +1160,7 @@ class LiveTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
     renderView = _LiveTestRenderView(
       configuration: createViewConfiguration(),
       onNeedPaint: _handleViewNeedsPaint,
+      window: window,
     );
     renderView.scheduleInitialFrame();
   }
@@ -1286,7 +1292,10 @@ class LiveTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
 
   @override
   ViewConfiguration createViewConfiguration() {
-    return TestViewConfiguration(size: _surfaceSize ?? _kDefaultTestViewportSize);
+    return TestViewConfiguration(
+      size: _surfaceSize ?? _kDefaultTestViewportSize,
+      window: window,
+    );
   }
 
   @override
@@ -1310,15 +1319,18 @@ class LiveTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
 /// size onto the actual display using the [BoxFit.contain] algorithm.
 class TestViewConfiguration extends ViewConfiguration {
   /// Creates a [TestViewConfiguration] with the given size. Defaults to 800x600.
-  TestViewConfiguration({ Size size = _kDefaultTestViewportSize })
+  TestViewConfiguration({
-    : _paintMatrix = _getMatrix(size, ui.window.devicePixelRatio),
+    Size size = _kDefaultTestViewportSize,
-      _hitTestMatrix = _getMatrix(size, 1.0),
+    ui.Window window,
+  })
+    : _paintMatrix = _getMatrix(size, window.devicePixelRatio, window),
+      _hitTestMatrix = _getMatrix(size, 1.0, window),
       super(size: size);
 
-  static Matrix4 _getMatrix(Size size, double devicePixelRatio) {
+  static Matrix4 _getMatrix(Size size, double devicePixelRatio, ui.Window window) {
-    final double inverseRatio = devicePixelRatio / ui.window.devicePixelRatio;
+    final double inverseRatio = devicePixelRatio / window.devicePixelRatio;
-    final double actualWidth = ui.window.physicalSize.width * inverseRatio;
+    final double actualWidth = window.physicalSize.width * inverseRatio;
-    final double actualHeight = ui.window.physicalSize.height * inverseRatio;
+    final double actualHeight = window.physicalSize.height * inverseRatio;
     final double desiredWidth = size.width;
     final double desiredHeight = size.height;
     double scale, shiftX, shiftY;
@@ -1377,7 +1389,8 @@ class _LiveTestRenderView extends RenderView {
   _LiveTestRenderView({
     ViewConfiguration configuration,
     this.onNeedPaint,
-  }) : super(configuration: configuration);
+    @required ui.Window window,
+  }) : super(configuration: configuration, window: window);
 
   @override
   TestViewConfiguration get configuration => super.configuration;

packages/flutter_test/lib/src/window.dart

@@ -0,0 +1,303 @@
+// Copyright 2018 The Chromium 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 'dart:typed_data' show ByteData;
+import 'dart:ui' hide window;
+
+import 'package:meta/meta.dart';
+
+/// [Window] that wraps another [Window] and allows faking of some properties
+/// for testing purposes.
+///
+/// Tests for certain widgets, e.g., [MaterialApp], might require faking certain
+/// properties of a [Window]. [TestWindow] facilitates the faking of these properties
+/// by overidding the properties of a real [Window] with desired fake values. The
+/// binding used within tests, [TestWidgetsFlutterBinding], contains a [TestWindow]
+/// that is used by all tests.
+///
+/// ## Sample Code
+///
+/// A test can utilize a [TestWindow] in the following way:
+///
+/// ```dart
+/// testWidgets('your test name here', (WidgetTester tester) async {
+///   // Retrieve the TestWidgetsFlutterBinding.
+///   final TestWidgetsFlutterBinding testBinding = tester.binding;
+///
+///   // Fake the desired properties of the TestWindow. All code running
+///   // within this test will perceive the following fake text scale
+///   // factor as the real text scale factor of the window.
+///   testBinding.window.textScaleFactorFakeValue = 2.5;
+///
+///   // Test code that depends on text scale factor here.
+/// });
+/// ```
+///
+/// The [TestWidgetsFlutterBinding] is recreated for each test and
+/// therefore any fake values defined in one test will not persist
+/// to the next.
+///
+/// If a test needs to override a real [Window] property and then later
+/// return to using the real [Window] property, [TestWindow] provides
+/// methods to clear each individual test value, e.g., [clearLocaleTestValue()].
+///
+/// To clear all fake test values in a [TestWindow], consider using [clearAllTestValues()].
+class TestWindow implements Window {
+  /// Constructs a [TestWindow] that defers all behavior to the given [window] unless
+  /// explicitly overidden for test purposes.
+  TestWindow({
+    @required Window window,
+  }) : _window = window;
+
+  /// The [Window] that is wrapped by this [TestWindow].
+  final Window _window;
+
+  @override
+  double get devicePixelRatio => _devicePixelRatio ?? _window.devicePixelRatio;
+  double _devicePixelRatio;
+  /// Hides the real device pixel ratio and reports the given [devicePixelRatio] instead.
+  set devicePixelRatioTestValue(double devicePixelRatio) {
+    _devicePixelRatio = devicePixelRatio;
+  }
+  /// Deletes any existing test device pixel ratio and returns to using the real device pixel ratio.
+  void clearDevicePixelRatioTestValue() {
+    _devicePixelRatio = null;
+  }
+
+  @override
+  Size get physicalSize => _physicalSizeTestValue ?? _window.physicalSize;
+  Size _physicalSizeTestValue;
+  /// Hides the real physical size and reports the given [physicalSizeTestValue] instead.
+  set physicalSizeTestValue (Size physicalSizeTestValue) {
+    _physicalSizeTestValue = physicalSizeTestValue;
+  }
+  /// Deletes any existing test physical size and returns to using the real physical size.
+  void clearPhysicalSizeTestValue() {
+    _physicalSizeTestValue = null;
+  }
+
+  @override
+  WindowPadding get viewInsets => _viewInsetsTestValue ??  _window.viewInsets;
+  WindowPadding _viewInsetsTestValue;
+  /// Hides the real view insets and reports the given [viewInsetsTestValue] instead.
+  set viewInsetsTestValue(WindowPadding viewInsetsTestValue) {
+    _viewInsetsTestValue = viewInsetsTestValue;
+  }
+  /// Deletes any existing test view insets and returns to using the real view insets.
+  void clearViewInsetsTestValue() {
+    _viewInsetsTestValue = null;
+  }
+
+  @override
+  WindowPadding get padding => _paddingTestValue ?? _window.padding;
+  WindowPadding _paddingTestValue;
+  /// Hides the real padding and reports the given [paddingTestValue] instead.
+  set paddingTestValue(WindowPadding paddingTestValue) {
+    _paddingTestValue = paddingTestValue;
+  }
+  /// Deletes any existing test padding and returns to using the real padding.
+  void clearPaddingTestValue() {
+    _paddingTestValue = null;
+  }
+
+  @override
+  VoidCallback get onMetricsChanged => _window.onMetricsChanged;
+  @override
+  set onMetricsChanged(VoidCallback callback) {
+    _window.onMetricsChanged = callback;
+  }
+
+  @override
+  Locale get locale => _localeTestValue ?? _window.locale;
+  Locale _localeTestValue;
+  /// Hides the real locale and reports the given [localeTestValue] instead.
+  set localeTestValue(Locale localeTestValue) {
+    _localeTestValue = localeTestValue;
+  }
+  /// Deletes any existing test locale and returns to using the real locale.
+  void clearLocaleTestValue() {
+    _localeTestValue = null;
+  }
+
+  @override
+  List<Locale> get locales => _localesTestValue ?? _window.locales;
+  List<Locale> _localesTestValue;
+  /// Hides the real locales and reports the given [localesTestValue] instead.
+  set localesTestValue(List<Locale> localesTestValue) {
+    _localesTestValue = localesTestValue;
+  }
+  /// Deletes any existing test locales and returns to using the real locales.
+  void clearLocalesTestValue() {
+    _localesTestValue = null;
+  }
+
+  @override
+  VoidCallback get onLocaleChanged => _window.onLocaleChanged;
+  @override
+  set onLocaleChanged(VoidCallback callback) {
+    _window.onLocaleChanged = callback;
+  }
+
+  @override
+  double get textScaleFactor => _textScaleFactorTestValue ?? _window.textScaleFactor;
+  double _textScaleFactorTestValue;
+  /// Hides the real text scale factor and reports the given [textScaleFactorTestValue] instead.
+  set textScaleFactorTestValue(double textScaleFactorTestValue) {
+    _textScaleFactorTestValue = textScaleFactorTestValue;
+  }
+  /// Deletes any existing test text scale factor and returns to using the real text scale factor.
+  void clearTextScaleFactorTestValue() {
+    _textScaleFactorTestValue = null;
+  }
+
+  @override
+  bool get alwaysUse24HourFormat => _alwaysUse24HourFormatTestValue ?? _window.alwaysUse24HourFormat;
+  bool _alwaysUse24HourFormatTestValue;
+  /// Hides the real clock format and reports the given [alwaysUse24HourFormatTestValue] instead.
+  set alwaysUse24HourFormatTestValue(bool alwaysUse24HourFormatTestValue) {
+    _alwaysUse24HourFormatTestValue = alwaysUse24HourFormatTestValue;
+  }
+  /// Deletes any existing test clock format and returns to using the real clock format.
+  void clearAlwaysUse24HourTestValue() {
+    _alwaysUse24HourFormatTestValue = null;
+  }
+
+  @override
+  VoidCallback get onTextScaleFactorChanged => _window.onTextScaleFactorChanged;
+  @override
+  set onTextScaleFactorChanged(VoidCallback callback) {
+    _window.onTextScaleFactorChanged = callback;
+  }
+
+  @override
+  FrameCallback get onBeginFrame => _window.onBeginFrame;
+  @override
+  set onBeginFrame(FrameCallback callback) {
+    _window.onBeginFrame = callback;
+  }
+
+  @override
+  VoidCallback get onDrawFrame => _window.onDrawFrame;
+  @override
+  set onDrawFrame(VoidCallback callback) {
+    _window.onDrawFrame = callback;
+  }
+
+  @override
+  PointerDataPacketCallback get onPointerDataPacket => _window.onPointerDataPacket;
+  @override
+  set onPointerDataPacket(PointerDataPacketCallback callback) {
+    _window.onPointerDataPacket = callback;
+  }
+
+  @override
+  String get defaultRouteName => _defaultRouteNameTestValue ?? _window.defaultRouteName;
+  String _defaultRouteNameTestValue;
+  /// Hides the real default route name and reports the given [defaultRouteNameTestValue] instead.
+  set defaultRouteNameTestValue(String defaultRouteNameTestValue) {
+    _defaultRouteNameTestValue = defaultRouteNameTestValue;
+  }
+  /// Deletes any existing test default route name and returns to using the real default route name.
+  void clearDefaultRouteNameTestValue() {
+    _defaultRouteNameTestValue = null;
+  }
+
+  @override
+  void scheduleFrame() {
+    _window.scheduleFrame();
+  }
+
+  @override
+  void render(Scene scene) {
+    _window.render(scene);
+  }
+
+  @override
+  bool get semanticsEnabled => _semanticsEnabledTestValue ?? _window.semanticsEnabled;
+  bool _semanticsEnabledTestValue;
+  /// Hides the real semantics enabled and reports the given [semanticsEnabledTestValue] instead.
+  set semanticsEnabledTestValue(bool semanticsEnabledTestValue) {
+    _semanticsEnabledTestValue = semanticsEnabledTestValue;
+  }
+  /// Deletes any existing test semantics enabled and returns to using the real semantics enabled.
+  void clearSemanticsEnabledTestValue() {
+    _semanticsEnabledTestValue = null;
+  }
+
+  @override
+  VoidCallback get onSemanticsEnabledChanged => _window.onSemanticsEnabledChanged;
+  @override
+  set onSemanticsEnabledChanged(VoidCallback callback) {
+    _window.onSemanticsEnabledChanged = callback;
+  }
+
+  @override
+  SemanticsActionCallback get onSemanticsAction => _window.onSemanticsAction;
+  @override
+  set onSemanticsAction(SemanticsActionCallback callback) {
+    _window.onSemanticsAction = callback;
+  }
+
+  @override
+  AccessibilityFeatures get accessibilityFeatures => _accessibilityFeaturesTestValue ?? _window.accessibilityFeatures;
+  AccessibilityFeatures _accessibilityFeaturesTestValue;
+  /// Hides the real accessibility features and reports the given [accessibilityFeaturesTestValue] instead.
+  set accessibilityFeaturesTestValue(AccessibilityFeatures accessibilityFeaturesTestValue) {
+    _accessibilityFeaturesTestValue = accessibilityFeaturesTestValue;
+  }
+  /// Deletes any existing test accessibility features and returns to using the real accessibility features.
+  void clearAccessibilityFeaturesTestValue() {
+    _accessibilityFeaturesTestValue = null;
+  }
+
+  @override
+  VoidCallback get onAccessibilityFeaturesChanged => _window.onAccessibilityFeaturesChanged;
+  @override
+  set onAccessibilityFeaturesChanged(VoidCallback callback) {
+    _window.onAccessibilityFeaturesChanged = callback;
+  }
+
+  @override
+  void updateSemantics(SemanticsUpdate update) {
+    _window.updateSemantics(update);
+  }
+
+  @override
+  void setIsolateDebugName(String name) {
+    _window.setIsolateDebugName(name);
+  }
+
+  @override
+  void sendPlatformMessage(String name,
+                           ByteData data,
+                           PlatformMessageResponseCallback callback) {
+    _window.sendPlatformMessage(name, data, callback);
+  }
+
+  @override
+  PlatformMessageCallback get onPlatformMessage => _window.onPlatformMessage;
+  @override
+  set onPlatformMessage(PlatformMessageCallback callback) {
+    _window.onPlatformMessage = callback;
+  }
+
+  /// Delete any test value properties that have been set on this [TestWindow]
+  /// and return to reporting the real [Window] values for all [Window] properties.
+  ///
+  /// If desired, clearing of properties can be done on an individual basis, e.g.,
+  /// [clearLocaleTestValue()].
+  void clearAllTestValues() {
+    clearAccessibilityFeaturesTestValue();
+    clearAlwaysUse24HourTestValue();
+    clearDefaultRouteNameTestValue();
+    clearDevicePixelRatioTestValue();
+    clearLocaleTestValue();
+    clearLocalesTestValue();
+    clearPaddingTestValue();
+    clearPhysicalSizeTestValue();
+    clearSemanticsEnabledTestValue();
+    clearTextScaleFactorTestValue();
+    clearViewInsetsTestValue();
+  }
+}

packages/flutter_test/test/window_test.dart

@@ -0,0 +1,256 @@
+// Copyright 2018 The Chromium 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 'dart:ui' as ui show window;
+import 'dart:ui' show Size, Locale, WindowPadding, AccessibilityFeatures;
+
+import 'package:flutter/widgets.dart' show WidgetsBinding;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meta/meta.dart';
+
+void main() {
+  testWidgets('TestWindow can fake device pixel ratio', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<double>(
+      tester: tester,
+      realValue: ui.window.devicePixelRatio,
+      fakeValue: 2.5,
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.devicePixelRatio;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, double fakeValue) {
+        binding.window.devicePixelRatioTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake physical size', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<Size>(
+      tester: tester,
+      realValue: ui.window.physicalSize,
+      fakeValue: const Size(50, 50),
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.physicalSize;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, Size fakeValue) {
+        binding.window.physicalSizeTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake view insets', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<WindowPadding>(
+      tester: tester,
+      realValue: ui.window.viewInsets,
+      fakeValue: const FakeWindowPadding(),
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.viewInsets;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, WindowPadding fakeValue) {
+        binding.window.viewInsetsTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake padding', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<WindowPadding>(
+      tester: tester,
+      realValue: ui.window.padding,
+      fakeValue: const FakeWindowPadding(),
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.padding;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, WindowPadding fakeValue) {
+        binding.window.paddingTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake locale', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<Locale>(
+      tester: tester,
+      realValue: ui.window.locale,
+      fakeValue: const Locale('fake_language_code'),
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.locale;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, Locale fakeValue) {
+        binding.window.localeTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake locales', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<List<Locale>>(
+      tester: tester,
+      realValue: ui.window.locales,
+      fakeValue: <Locale>[const Locale('fake_language_code')],
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.locales;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, List<Locale> fakeValue) {
+        binding.window.localesTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake text scale factor', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<double>(
+      tester: tester,
+      realValue: ui.window.textScaleFactor,
+      fakeValue: 2.5,
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.textScaleFactor;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, double fakeValue) {
+        binding.window.textScaleFactorTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake clock format', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<bool>(
+      tester: tester,
+      realValue: ui.window.alwaysUse24HourFormat,
+      fakeValue: !ui.window.alwaysUse24HourFormat,
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.alwaysUse24HourFormat;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, bool fakeValue) {
+        binding.window.alwaysUse24HourFormatTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake default route name', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<String>(
+      tester: tester,
+      realValue: ui.window.defaultRouteName,
+      fakeValue: 'fake_route',
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.defaultRouteName;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, String fakeValue) {
+        binding.window.defaultRouteNameTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake semantics enabled', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<bool>(
+      tester: tester,
+      realValue: ui.window.semanticsEnabled,
+      fakeValue: !ui.window.semanticsEnabled,
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.semanticsEnabled;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, bool fakeValue) {
+        binding.window.semanticsEnabledTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can fake accessibility features', (WidgetTester tester) async {
+    verifyThatTestWindowCanFakeProperty<AccessibilityFeatures>(
+      tester: tester,
+      realValue: ui.window.accessibilityFeatures,
+      fakeValue: const FakeAccessibilityFeatures(),
+      propertyRetriever: () {
+        return WidgetsBinding.instance.window.accessibilityFeatures;
+      },
+      propertyFaker: (TestWidgetsFlutterBinding binding, AccessibilityFeatures fakeValue) {
+        binding.window.accessibilityFeaturesTestValue = fakeValue;
+      }
+    );
+  });
+
+  testWidgets('TestWindow can clear out fake properties all at once', (WidgetTester tester) {
+    final double originalDevicePixelRatio = ui.window.devicePixelRatio;
+    final double originalTextScaleFactor = ui.window.textScaleFactor;
+    final TestWindow testWindow = retrieveTestBinding(tester).window;
+
+    // Set fake values for window properties.
+    testWindow.devicePixelRatioTestValue = 2.5;
+    testWindow.textScaleFactorTestValue = 3.0;
+
+    // Erase fake window property values.
+    testWindow.clearAllTestValues();
+
+    // Verify that the window once again reports real property values.
+    expect(WidgetsBinding.instance.window.devicePixelRatio, originalDevicePixelRatio);
+    expect(WidgetsBinding.instance.window.textScaleFactor, originalTextScaleFactor);
+  });
+}
+
+void verifyThatTestWindowCanFakeProperty<WindowPropertyType>({
+  @required WidgetTester tester,
+  @required WindowPropertyType realValue,
+  @required WindowPropertyType fakeValue,
+  @required WindowPropertyType Function() propertyRetriever,
+  @required Function(TestWidgetsFlutterBinding, WindowPropertyType fakeValue) propertyFaker,
+}) {
+  WindowPropertyType propertyBeforeFaking;
+  WindowPropertyType propertyAfterFaking;
+
+  propertyBeforeFaking = propertyRetriever();
+
+  propertyFaker(retrieveTestBinding(tester), fakeValue);
+
+  propertyAfterFaking = propertyRetriever();
+
+  expect(propertyBeforeFaking, realValue);
+  expect(propertyAfterFaking, fakeValue);
+}
+
+TestWidgetsFlutterBinding retrieveTestBinding(WidgetTester tester) {
+  final WidgetsBinding binding = tester.binding;
+  assert(binding is TestWidgetsFlutterBinding);
+  final TestWidgetsFlutterBinding testBinding = binding;
+  return testBinding;
+}
+
+class FakeWindowPadding implements WindowPadding {
+  const FakeWindowPadding({
+    this.left = 0.0,
+    this.top = 0.0,
+    this.right = 0.0,
+    this.bottom = 0.0,
+  });
+
+  @override
+  final double left;
+
+  @override
+  final double top;
+
+  @override
+  final double right;
+
+  @override
+  final double bottom;
+}
+
+class FakeAccessibilityFeatures implements AccessibilityFeatures {
+  const FakeAccessibilityFeatures({
+    this.accessibleNavigation = false,
+    this.invertColors = false,
+    this.disableAnimations = false,
+    this.boldText = false,
+    this.reduceMotion = false,
+  });
+
+  @override
+  final bool accessibleNavigation;
+
+  @override
+  final bool invertColors;
+
+  @override
+  final bool disableAnimations;
+
+  @override
+  final bool boldText;
+
+  @override
+  final bool reduceMotion;
+}