[dart:ui] Introduce PlatformDispatcher.implicitView

loic-sharma · loic-sharma · commit 054ec8427255 · 2023-02-14T13:34:36.000-08:00
diff --git a/lib/ui/dart_ui.cc b/lib/ui/dart_ui.cc
@@ -95,6 +95,7 @@ typedef CanvasPath Path;
   V(IsolateNameServerNatives::RemovePortNameMapping, 1)               \
   V(NativeStringAttribute::initLocaleStringAttribute, 4)              \
   V(NativeStringAttribute::initSpellOutStringAttribute, 3)            \
+  V(PlatformConfigurationNativeApi::ImplicitViewEnabled, 0)           \
   V(PlatformConfigurationNativeApi::DefaultRouteName, 0)              \
   V(PlatformConfigurationNativeApi::ScheduleFrame, 0)                 \
   V(PlatformConfigurationNativeApi::Render, 1)                        \
diff --git a/lib/ui/platform_dispatcher.dart b/lib/ui/platform_dispatcher.dart
@@ -168,6 +168,23 @@ class PlatformDispatcher {
   // A map of opaque platform view identifiers to view configurations.
   final Map<Object, ViewConfiguration> _viewConfigurations = <Object, ViewConfiguration>{};
 
+  /// The implicit [FlutterView] provided by the platform, if any.
+  ///
+  /// This is used to bootstrap the framework for applications where the
+  /// platform provides a view, such as applications designed for
+  /// single-display mobile devices.
+  ///
+  /// While the [FlutterView]'s properties may change, this reference is
+  /// guaranteed to never change.
+  ///
+  /// See also:
+  ///
+  /// * [View.of], for accessing the current view.
+  FlutterView? get implicitView => _implicitViewEnabled() ? _views[0] : null;
+
+  @Native<Handle Function()>(symbol: 'PlatformConfigurationNativeApi::ImplicitViewEnabled')
+  external static bool _implicitViewEnabled();
+
   /// A callback that is invoked whenever the [ViewConfiguration] of any of the
   /// [views] changes.
   ///
diff --git a/lib/ui/window.dart b/lib/ui/window.dart
@@ -896,6 +896,7 @@ enum Brightness {
 /// * [PlatformDispatcher.views], contains the current list of Flutter windows
 ///   belonging to the application, including top level application windows like
 ///   this one.
+/// * [PlatformDispatcher.implicitView], this window's view.
 final SingletonFlutterWindow window = SingletonFlutterWindow._(0, PlatformDispatcher.instance);
 
 /// Additional data available on each flutter frame.
diff --git a/lib/ui/window/platform_configuration.cc b/lib/ui/window/platform_configuration.cc
@@ -22,6 +22,8 @@
 namespace flutter {
 namespace {
 
+const int kImplicitViewId = 0;
+
 Dart_Handle ToByteData(const fml::Mapping& buffer) {
   return tonic::DartByteData::Create(buffer.GetMapping(), buffer.GetSize());
 }
@@ -67,8 +69,10 @@ void PlatformConfiguration::DidCreateIsolate() {
                   Dart_GetField(library, tonic::ToDart("_drawFrame")));
   report_timings_.Set(tonic::DartState::Current(),
                       Dart_GetField(library, tonic::ToDart("_reportTimings")));
-  windows_.insert(std::make_pair(
-      0, std::make_unique<Window>(0, ViewportMetrics{1.0, 0.0, 0.0, -1})));
+  windows_.insert(
+      std::make_pair(kImplicitViewId,
+                     std::make_unique<Window>(
+                         kImplicitViewId, ViewportMetrics{1.0, 0.0, 0.0, -1})));
 }
 
 void PlatformConfiguration::UpdateLocales(
@@ -427,6 +431,16 @@ Dart_Handle PlatformConfigurationNativeApi::ComputePlatformResolvedLocale(
   return tonic::DartConverter<std::vector<std::string>>::ToDart(results);
 }
 
+Dart_Handle PlatformConfigurationNativeApi::ImplicitViewEnabled() {
+  UIDartState::ThrowIfUIOperationsProhibited();
+  bool enabled = UIDartState::Current()
+                     ->platform_configuration()
+                     ->client()
+                     ->ImplicitViewEnabled();
+
+  return Dart_NewBoolean(enabled);
+}
+
 std::string PlatformConfigurationNativeApi::DefaultRouteName() {
   UIDartState::ThrowIfUIOperationsProhibited();
   return UIDartState::Current()
diff --git a/lib/ui/window/platform_configuration.h b/lib/ui/window/platform_configuration.h
@@ -49,6 +49,16 @@ enum class AccessibilityFeatureFlag : int32_t {
 ///
 class PlatformConfigurationClient {
  public:
+  //--------------------------------------------------------------------------
+  /// @brief      Whether the platform provides an implicit view. If true,
+  ///             the Framework may assume that it can always render into
+  ///             the view with ID 0.
+  ///
+  ///             This value must not change for the lifetime of the
+  ///             application.
+  ///
+  virtual bool ImplicitViewEnabled() = 0;
+
   //--------------------------------------------------------------------------
   /// @brief      The route or path that the embedder requested when the
   ///             application was launched.
@@ -71,7 +81,7 @@ class PlatformConfigurationClient {
   virtual void Render(Scene* scene) = 0;
 
   //--------------------------------------------------------------------------
-  /// @brief      Receives a updated semantics tree from the Framework.
+  /// @brief      Receives an updated semantics tree from the Framework.
   ///
   /// @param[in] update The updated semantic tree to apply.
   ///
@@ -469,6 +479,8 @@ class PlatformMessageHandlerStorage {
 //----------------------------------------------------------------------------
 class PlatformConfigurationNativeApi {
  public:
+  static Dart_Handle ImplicitViewEnabled();
+
   static std::string DefaultRouteName();
 
   static void ScheduleFrame();
diff --git a/lib/web_ui/lib/platform_dispatcher.dart b/lib/web_ui/lib/platform_dispatcher.dart
@@ -33,6 +33,8 @@ abstract class PlatformDispatcher {
 
   Iterable<FlutterView> get views;
 
+  FlutterView? get implicitView;
+
   VoidCallback? get onMetricsChanged;
   set onMetricsChanged(VoidCallback? callback);
 
diff --git a/lib/web_ui/lib/src/engine/platform_dispatcher.dart b/lib/web_ui/lib/src/engine/platform_dispatcher.dart
@@ -148,6 +148,21 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
   final Map<Object, ui.ViewConfiguration> _windowConfigurations =
       <Object, ui.ViewConfiguration>{};
 
+  /// The implicit [FlutterView] provided by the platform, if any.
+  ///
+  /// This is used to bootstrap the framework for applications where the
+  /// platform provides a view, such as applications designed for
+  /// single-display mobile devices.
+  ///
+  /// While the [FlutterView]'s properties may change, this reference is
+  /// guaranteed to never change.
+  ///
+  /// See also:
+  ///
+  /// * [View.of], for accessing the current view.
+  @override
+  ui.FlutterView? get implicitView => viewData[kImplicitViewId];
+
   /// A callback that is invoked whenever the platform's [devicePixelRatio],
   /// [physicalSize], [padding], [viewInsets], or [systemGestureInsets]
   /// values change, for example when the device is rotated or when the
@@ -479,7 +494,7 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
             // 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.
-            (viewData[kSingletonViewId]! as EngineFlutterWindow)
+            (viewData[kImplicitViewId]! as EngineFlutterWindow)
                 .browserHistory
                 .exit()
                 .then((_) {
@@ -584,7 +599,7 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
         // 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.
-        (viewData[kSingletonViewId]! as EngineFlutterWindow)
+        (viewData[kImplicitViewId]! as EngineFlutterWindow)
             .handleNavigationMessage(data)
             .then((bool handled) {
           if (handled) {
@@ -1173,7 +1188,7 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
   @override
   String get defaultRouteName {
     return _defaultRouteName ??=
-        (viewData[kSingletonViewId]! as EngineFlutterWindow).browserHistory.currentPath;
+        (viewData[kImplicitViewId]! as EngineFlutterWindow).browserHistory.currentPath;
   }
 
   /// Lazily initialized when the `defaultRouteName` getter is invoked.
diff --git a/lib/web_ui/lib/src/engine/window.dart b/lib/web_ui/lib/src/engine/window.dart
@@ -27,8 +27,8 @@ typedef _HandleMessageCallBack = Future<bool> Function();
 /// When set to true, all platform messages will be printed to the console.
 const bool debugPrintPlatformMessages = false;
 
-/// The view ID for a singleton flutter window.
-const int kSingletonViewId = 0;
+/// The view ID for the implicit flutter view provided by the platform.
+const int kImplicitViewId = 0;
 
 /// Whether [_customUrlStrategy] has been set or not.
 ///
@@ -349,7 +349,7 @@ class EngineSingletonFlutterWindow extends EngineFlutterWindow {
 /// API surface, providing Web-specific functionality that the standard
 /// `dart:ui` version does not.
 final EngineSingletonFlutterWindow window =
-    EngineSingletonFlutterWindow(kSingletonViewId, EnginePlatformDispatcher.instance);
+    EngineSingletonFlutterWindow(kImplicitViewId, EnginePlatformDispatcher.instance);
 
 /// The Web implementation of [ui.WindowPadding].
 class WindowPadding implements ui.WindowPadding {
diff --git a/lib/web_ui/test/window_test.dart b/lib/web_ui/test/window_test.dart
@@ -41,6 +41,12 @@ void testMain() {
     await window.resetHistory();
   });
 
+  test('EnginePlatformDispatcher.instance.implicitView should be non-null', () async {
+    expect(EnginePlatformDispatcher.instance.implicitView, isNotNull);
+    expect(EnginePlatformDispatcher.instance.implicitView?.viewId, 0);
+    expect(window.viewId, 0);
+  });
+
   test('window.defaultRouteName should work with JsUrlStrategy', () async {
     dynamic state = <dynamic, dynamic>{};
     final JsUrlStrategy jsUrlStrategy = JsUrlStrategy(
diff --git a/runtime/runtime_controller.cc b/runtime/runtime_controller.cc
@@ -298,6 +298,11 @@ RuntimeController::GetPlatformConfigurationIfAvailable() {
   return root_isolate ? root_isolate->platform_configuration() : nullptr;
 }
 
+// |PlatformConfigurationClient|
+bool RuntimeController::ImplicitViewEnabled() {
+  return client_.ImplicitViewEnabled();
+}
+
 // |PlatformConfigurationClient|
 std::string RuntimeController::DefaultRouteName() {
   return client_.DefaultRouteName();
diff --git a/runtime/runtime_controller.h b/runtime/runtime_controller.h
@@ -610,6 +610,9 @@ class RuntimeController : public PlatformConfigurationClient {
 
   bool FlushRuntimeStateToIsolate();
 
+  // |PlatformConfigurationClient|
+  bool ImplicitViewEnabled() override;
+
   // |PlatformConfigurationClient|
   std::string DefaultRouteName() override;
 
diff --git a/runtime/runtime_delegate.h b/runtime/runtime_delegate.h
@@ -21,6 +21,8 @@ namespace flutter {
 
 class RuntimeDelegate {
  public:
+  virtual bool ImplicitViewEnabled() = 0;
+
   virtual std::string DefaultRouteName() = 0;
 
   virtual void ScheduleFrame(bool regenerate_layer_tree = true) = 0;
diff --git a/shell/common/engine.cc b/shell/common/engine.cc
@@ -431,6 +431,13 @@ void Engine::SetAccessibilityFeatures(int32_t flags) {
   runtime_controller_->SetAccessibilityFeatures(flags);
 }
 
+bool Engine::ImplicitViewEnabled() {
+  // TODO(loicsharma): This value should be provided by the embedder
+  // when it launches the engine. For now, assume the embedder always creates a
+  // view.
+  return true;
+}
+
 std::string Engine::DefaultRouteName() {
   if (!initial_route_.empty()) {
     return initial_route_;
diff --git a/shell/common/engine.h b/shell/common/engine.h
@@ -888,6 +888,9 @@ class Engine final : public RuntimeDelegate, PointerDataDispatcher::Delegate {
   const std::weak_ptr<VsyncWaiter> GetVsyncWaiter() const;
 
  private:
+  // |RuntimeDelegate|
+  bool ImplicitViewEnabled() override;
+
   // |RuntimeDelegate|
   std::string DefaultRouteName() override;
 
diff --git a/shell/common/engine_unittests.cc b/shell/common/engine_unittests.cc
@@ -48,6 +48,7 @@ class MockResponse : public PlatformMessageResponse {
 
 class MockRuntimeDelegate : public RuntimeDelegate {
  public:
+  MOCK_METHOD0(ImplicitViewEnabled, bool());
   MOCK_METHOD0(DefaultRouteName, std::string());
   MOCK_METHOD1(ScheduleFrame, void(bool));
   MOCK_METHOD1(Render, void(std::shared_ptr<flutter::LayerTree>));
diff --git a/shell/platform/embedder/fixtures/main.dart b/shell/platform/embedder/fixtures/main.dart
@@ -45,8 +45,15 @@ void executableNameNotNull() {
   notifyStringValue(Platform.executable);
 }
 
+@pragma('vm:entry-point')
+void implicitViewNotNull() {
+  notifyBoolValue(PlatformDispatcher.instance.implicitView != null);
+}
+
 @pragma('vm:external-name', 'NotifyStringValue')
 external void notifyStringValue(String value);
+@pragma('vm:external-name', 'NotifyBoolValue')
+external void notifyBoolValue(bool value);
 
 @pragma('vm:entry-point')
 void invokePlatformTaskRunner() {
diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -174,6 +174,25 @@ TEST_F(EmbedderTest, ExecutableNameNotNull) {
   latch.Wait();
 }
 
+TEST_F(EmbedderTest, ImplicitViewNotNull) {
+  auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
+
+  fml::AutoResetWaitableEvent latch;
+  context.AddNativeCallback(
+      "NotifyBoolValue", CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
+        const auto dart_bool = tonic::DartConverter<bool>::FromDart(
+            Dart_GetNativeArgument(args, 0));
+        EXPECT_TRUE(dart_bool);
+        latch.Signal();
+      }));
+
+  EmbedderConfigBuilder builder(context);
+  builder.SetSoftwareRendererConfig();
+  builder.SetDartEntrypoint("implicitViewNotNull");
+  auto engine = builder.LaunchEngine();
+  latch.Wait();
+}
+
 std::atomic_size_t EmbedderTestTaskRunner::sEmbedderTaskRunnerIdentifiers = {};
 
 TEST_F(EmbedderTest, CanSpecifyCustomPlatformTaskRunner) {
