Remove single view assumptions from window.dart (flutter#38453)

* Refactor `window.dart`

* Remove single window assumption from platform dispatcher

* Expose viewId

* Remove FlutterWindow from web_ui

* Refactor EngineFlutterWindow to inherit from FlutterView

* Rename window property

* Undo Iterable -> Map conversion

* Add window and deprecate it so that the change isn't breaking

* Name resolution

* Revisions

* Doc changes

* Refactor deprecation message

* Newline

* Expose getViewById, hide map interface

* Fix compilaiton errors

* Introduce addView API

* Change deprecation message

* Update lib/ui/window.dart

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>

* Take greg's todos

* Add mutual exclusion assertion

* Fix trailing whitespace lint

* Use only one property to store backing view

* Add doc comment to view

* Document view and window parameters in the constructor of ViewConfiguration

* Sync web api

* Refactor assertion

* Improve deprecation message

* Improve window documentation

* Assert one of window/view is null in copyWith ViewConfiguration

* Remove EngineFlutterWindowView

* Make dartdoc happy

* Refactor copyWith()

* Change to internal map implementation

* final private refactor

Co-authored-by: Michael Goderbauer <goderbauer@google.com>

* Deprecate window parameter in copyWith

* Repl Window w/ View

* Add tests for viewConfiguration

* Make test descriptions better

* Add ViewConfiguration initialization with window tests

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

Co-authored-by: David Iglesias <ditman@gmail.com>

* Refactor TODO message

* Add expectation :)

* Fix viewId in window.dart

* Remove double deprecation access

* punctuation

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>

* Add kSingletonWindowID const

Co-authored-by: a-wallen <stephenwallen@google.com>
Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
Co-authored-by: Michael Goderbauer <goderbauer@google.com>
Co-authored-by: David Iglesias <ditman@gmail.com>

Author: 5 people

lib/ui/platform_dispatcher.dart

@@ -222,10 +222,10 @@ class PlatformDispatcher {
     final ViewConfiguration previousConfiguration =
         _viewConfigurations[id] ?? const ViewConfiguration();
     if (!_views.containsKey(id)) {
-      _views[id] = FlutterWindow._(id, this);
+      _views[id] = FlutterView._(id, this);
     }
     _viewConfigurations[id] = previousConfiguration.copyWith(
-      window: _views[id],
+      view: _views[id],
       devicePixelRatio: devicePixelRatio,
       geometry: Rect.fromLTWH(0.0, 0.0, width, height),
       viewPadding: WindowPadding._(
@@ -1289,8 +1289,18 @@ class PlatformConfiguration {
 /// An immutable view configuration.
 class ViewConfiguration {
   /// A const constructor for an immutable [ViewConfiguration].
+  ///
+  /// When constructing a view configuration, supply either the [view] or the
+  /// [window] property, but not both since the [view] and [window] property
+  /// are backed by the same instance variable.
   const ViewConfiguration({
-    this.window,
+    FlutterView? view,
+    @Deprecated('''
+      Use the `view` property instead.
+      This change is related to adding multi-view support in Flutter.
+      This feature was deprecated after 3.7.0-1.2.pre.
+    ''')
+    FlutterView? window,
     this.devicePixelRatio = 1.0,
     this.geometry = Rect.zero,
     this.visible = false,
@@ -1300,10 +1310,17 @@ class ViewConfiguration {
     this.padding = WindowPadding.zero,
     this.gestureSettings = const GestureSettings(),
     this.displayFeatures = const <DisplayFeature>[],
-  });
+  }) : assert(window == null || view == null),
+    _view = view ?? window;
 
   /// Copy this configuration with some fields replaced.
   ViewConfiguration copyWith({
+    FlutterView? view,
+    @Deprecated('''
+      Use the `view` property instead.
+      This change is related to adding multi-view support in Flutter.
+      This feature was deprecated after 3.7.0-1.2.pre.
+    ''')
     FlutterView? window,
     double? devicePixelRatio,
     Rect? geometry,
@@ -1315,8 +1332,9 @@ class ViewConfiguration {
     GestureSettings? gestureSettings,
     List<DisplayFeature>? displayFeatures,
   }) {
+    assert(view == null || window == null);
     return ViewConfiguration(
-      window: window ?? this.window,
+      view: view ?? window ?? _view,
       devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
       geometry: geometry ?? this.geometry,
       visible: visible ?? this.visible,
@@ -1329,11 +1347,22 @@ class ViewConfiguration {
     );
   }
 
-  /// The top level view into which the view is placed and its geometry is
-  /// relative to.
+  /// The top level view for which this [ViewConfiguration]'s properties apply to.
+  ///
+  /// If this property is null, this [ViewConfiguration] is a top level view.
+  @Deprecated('''
+    Use the `view` property instead.
+    This change is related to adding multi-view support in Flutter.
+    This feature was deprecated after 3.7.0-1.2.pre.
+  ''')
+  FlutterView? get window => _view;
+
+  /// The top level view for which this [ViewConfiguration]'s properties apply to.
   ///
-  /// If null, then this configuration represents a top level view itself.
-  final FlutterView? window;
+  /// If this property is null, this [ViewConfiguration] is a top level view.
+  FlutterView? get view => _view;
+
+  final FlutterView?  _view;
 
   /// The pixel density of the output surface.
   final double devicePixelRatio;
@@ -1427,7 +1456,7 @@ class ViewConfiguration {
 
   @override
   String toString() {
-    return '$runtimeType[window: $window, geometry: $geometry]';
+    return '$runtimeType[view: $view, geometry: $geometry]';
   }
 }
 
@@ -1666,7 +1695,7 @@ enum AppLifecycleState {
   /// On Android, this corresponds to an app or the Flutter host view running
   /// in the foreground inactive state.  Apps transition to this state when
   /// another activity is focused, such as a split-screen app, a phone call,
-  /// a picture-in-picture app, a system dialog, or another window.
+  /// a picture-in-picture app, a system dialog, or another view.
   ///
   /// Apps in this state should assume that they may be [paused] at any time.
   inactive,

lib/ui/window.dart

@@ -5,8 +5,8 @@ part of dart.ui;
 
 /// A view into which a Flutter [Scene] is drawn.
 ///
-/// Each [FlutterView] has its own layer tree that is rendered into an area
-/// inside of a [FlutterWindow] whenever [render] is called with a [Scene].
+/// Each [FlutterView] has its own layer tree that is rendered
+/// whenever [render] is called on it with a [Scene].
 ///
 /// ## Insets and Padding
 ///
@@ -51,18 +51,21 @@ part of dart.ui;
 /// the [viewPadding] anyway, so there is no need to account for
 /// that in the [padding], which is always safe to use for such
 /// calculations.
-///
-/// See also:
-///
-///  * [FlutterWindow], a special case of a [FlutterView] that is represented on
-///    the platform as a separate window which can host other [FlutterView]s.
-abstract class FlutterView {
+class FlutterView {
+  FlutterView._(this.viewId, this.platformDispatcher);
+
+  /// The opaque ID for this view.
+  final Object viewId;
+
   /// The platform dispatcher that this view is registered with, and gets its
   /// information from.
-  PlatformDispatcher get platformDispatcher;
+  final PlatformDispatcher platformDispatcher;
 
   /// The configuration of this view.
-  ViewConfiguration get viewConfiguration;
+  ViewConfiguration get viewConfiguration {
+    assert(platformDispatcher._viewConfigurations.containsKey(viewId));
+    return platformDispatcher._viewConfigurations[viewId]!;
+  }
 
   /// The number of device pixels for each logical pixel for the screen this
   /// view is displayed on.
@@ -281,39 +284,7 @@ abstract class FlutterView {
   external static void _updateSemantics(SemanticsUpdate update);
 }
 
-/// A top-level platform window displaying a Flutter layer tree drawn from a
-/// [Scene].
-///
-/// The current list of all Flutter views for the application is available from
-/// `WidgetsBinding.instance.platformDispatcher.views`. Only views that are of type
-/// [FlutterWindow] are top level platform windows.
-///
-/// There is also a [PlatformDispatcher.instance] singleton object in `dart:ui`
-/// if `WidgetsBinding` is unavailable, but we strongly advise avoiding a static
-/// reference to it. See the documentation for [PlatformDispatcher.instance] for
-/// more details about why it should be avoided.
-///
-/// See also:
-///
-/// * [PlatformDispatcher], which manages the current list of [FlutterView] (and
-///   thus [FlutterWindow]) instances.
-class FlutterWindow extends FlutterView {
-  FlutterWindow._(this._windowId, this.platformDispatcher);
-
-  /// The opaque ID for this view.
-  final Object _windowId;
-
-  @override
-  final PlatformDispatcher platformDispatcher;
-
-  @override
-  ViewConfiguration get viewConfiguration {
-    assert(platformDispatcher._viewConfigurations.containsKey(_windowId));
-    return platformDispatcher._viewConfigurations[_windowId]!;
-  }
-}
-
-/// A [FlutterWindow] that includes access to setting callbacks and retrieving
+/// A [FlutterView] that includes access to setting callbacks and retrieving
 /// properties that reside on the [PlatformDispatcher].
 ///
 /// It is the type of the global [window] singleton used by applications that
@@ -328,7 +299,7 @@ class FlutterWindow extends FlutterView {
 /// `WidgetsBinding.instance.platformDispatcher` over a static reference to
 /// [window], or [PlatformDispatcher.instance]. See the documentation for
 /// [PlatformDispatcher.instance] for more details about this recommendation.
-class SingletonFlutterWindow extends FlutterWindow {
+class SingletonFlutterWindow extends FlutterView {
   SingletonFlutterWindow._(super.windowId, super.platformDispatcher)
       : super._();
 

lib/web_ui/lib/platform_dispatcher.dart

@@ -190,7 +190,13 @@ class PlatformConfiguration {
 
 class ViewConfiguration {
   const ViewConfiguration({
-    this.window,
+    FlutterView? view,
+    @Deprecated('''
+      Use the `view` property instead.
+      This change is related to adding multi-view support in Flutter.
+      This feature was deprecated after 3.7.0-1.2.pre.
+    ''')
+    FlutterView? window,
     this.devicePixelRatio = 1.0,
     this.geometry = Rect.zero,
     this.visible = false,
@@ -200,10 +206,17 @@ class ViewConfiguration {
     this.padding = WindowPadding.zero,
     this.gestureSettings = const GestureSettings(),
     this.displayFeatures = const <DisplayFeature>[],
-  });
+  }) : assert(window == null || view == null),
+  _view = view ?? window;
 
   ViewConfiguration copyWith({
-    FlutterWindow? window,
+    FlutterView? view,
+    @Deprecated('''
+      Use the `view` property instead.
+      This change is related to adding multi-view support in Flutter.
+      This feature was deprecated after 3.7.0-1.2.pre.
+    ''')
+    FlutterView? window,
     double? devicePixelRatio,
     Rect? geometry,
     bool? visible,
@@ -214,8 +227,9 @@ class ViewConfiguration {
     GestureSettings? gestureSettings,
     List<DisplayFeature>? displayFeatures,
   }) {
+    assert(view == null || window == null);
     return ViewConfiguration(
-      window: window ?? this.window,
+      view: view ?? window ?? _view,
       devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
       geometry: geometry ?? this.geometry,
       visible: visible ?? this.visible,
@@ -228,7 +242,14 @@ class ViewConfiguration {
     );
   }
 
-  final FlutterWindow? window;
+  @Deprecated('''
+    Use the `view` property instead.
+    This change is related to adding multi-view support in Flutter.
+    This feature was deprecated after 3.7.0-1.2.pre.
+  ''')
+  FlutterView? get window => _view;
+  FlutterView? get view => _view;
+  final FlutterView? _view;
   final double devicePixelRatio;
   final Rect geometry;
   final bool visible;
@@ -241,7 +262,7 @@ class ViewConfiguration {
 
   @override
   String toString() {
-    return '$runtimeType[window: $window, geometry: $geometry]';
+    return '$runtimeType[view: $view, geometry: $geometry]';
   }
 }
 

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

@@ -136,11 +136,10 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
         _onPlatformConfigurationChanged, _onPlatformConfigurationChangedZone);
   }
 
-  /// The current list of windows,
+  /// The current list of windows.
   @override
-  Iterable<ui.FlutterView> get views => _windows.values;
-  Map<Object, ui.FlutterWindow> get windows => _windows;
-  final Map<Object, ui.FlutterWindow> _windows = <Object, ui.FlutterWindow>{};
+  Iterable<ui.FlutterView> get views => viewData.values;
+  final Map<Object, ui.FlutterView> viewData = <Object, ui.FlutterView>{};
 
   /// A map of opaque platform window identifiers to window configurations.
   ///
@@ -478,10 +477,10 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
         final MethodCall decoded = codec.decodeMethodCall(data);
         switch (decoded.method) {
           case 'SystemNavigator.pop':
-            // TODO(gspencergoog): As multi-window support expands, the pop call
-            // will need to include the window ID. Right now only one window is
+            // TODO(a-wallen): As multi-window support expands, the pop call
+            // will need to include the view ID. Right now only one view is
             // supported.
-            (_windows[0]! as EngineFlutterWindow)
+            (viewData[kSingletonViewId]! as EngineFlutterWindow)
                 .browserHistory
                 .exit()
                 .then((_) {
@@ -568,10 +567,10 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
         return;
 
       case 'flutter/navigation':
-        // TODO(gspencergoog): As multi-window support expands, the navigation call
-        // will need to include the window ID. Right now only one window is
+        // TODO(a-wallen): As multi-window support expands, the navigation call
+        // will need to include the view ID. Right now only one view is
         // supported.
-        (_windows[0]! as EngineFlutterWindow)
+        (viewData[kSingletonViewId]! as EngineFlutterWindow)
             .handleNavigationMessage(data)
             .then((bool handled) {
           if (handled) {
@@ -1160,7 +1159,7 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
   @override
   String get defaultRouteName {
     return _defaultRouteName ??=
-        (_windows[0]! as EngineFlutterWindow).browserHistory.currentPath;
+        (viewData[kSingletonViewId]! as EngineFlutterWindow).browserHistory.currentPath;
   }
 
   /// Lazily initialized when the `defaultRouteName` getter is invoked.