Multi-view View Metrics

examples/glfw/FlutterEmbedderGLFW.cc

@@ -81,6 +81,9 @@ void GLFWwindowSizeCallback(GLFWwindow* window, int width, int height) {
   event.width = width * g_pixelRatio;
   event.height = height * g_pixelRatio;
   event.pixel_ratio = g_pixelRatio;
+  // This example only supports a single window, therefore we assume the event
+  // occurred in the only view, the implicit view.
+  event.view_id = kImplicitViewId;
   FlutterEngineSendWindowMetricsEvent(
       reinterpret_cast<FlutterEngine>(glfwGetWindowUserPointer(window)),
       &event);

examples/glfw_drm/FlutterEmbedderGLFW.cc

@@ -104,6 +104,9 @@ void GLFWwindowSizeCallback(GLFWwindow* window, int width, int height) {
   event.width = width * g_pixelRatio;
   event.height = height * g_pixelRatio;
   event.pixel_ratio = g_pixelRatio;
+  // This example only supports a single window, therefore we assume the event
+  // occurred in the only view, the implicit view.
+  event.view_id = kImplicitViewId;
   FlutterEngineSendWindowMetricsEvent(
       reinterpret_cast<FlutterEngine>(glfwGetWindowUserPointer(window)),
       &event);

examples/vulkan_glfw/src/main.cc

@@ -32,6 +32,7 @@ static const size_t kInitialWindowHeight = 600;
 // `VK_PRESENT_MODE_MAILBOX_KHR` for continual swap without horizontal tearing,
 // or `VK_PRESENT_MODE_IMMEDIATE_KHR` for no vsync.
 static const VkPresentModeKHR kPreferredPresentMode = VK_PRESENT_MODE_FIFO_KHR;
+static constexpr FlutterViewId kImplicitViewId = 0;
 
 static_assert(FLUTTER_ENGINE_VERSION == 1,
               "This Flutter Embedder was authored against the stable Flutter "
@@ -86,6 +87,9 @@ void GLFWcursorPositionCallbackAtPhase(GLFWwindow* window,
       std::chrono::duration_cast<std::chrono::microseconds>(
           std::chrono::high_resolution_clock::now().time_since_epoch())
           .count();
+  // This example only supports a single window, therefore we assume the event
+  // occurred in the only view, the implicit view.
+  event.view_id = kImplicitViewId;
   FlutterEngineSendPointerEvent(g_state.engine, &event, 1);
 }
 
@@ -130,6 +134,9 @@ void GLFWframebufferSizeCallback(GLFWwindow* window, int width, int height) {
   event.width = width;
   event.height = height;
   event.pixel_ratio = g_pixelRatio;
+  // This example only supports a single window, therefore we assume the event
+  // occurred in the only view, the implicit view.
+  event.view_id = kImplicitViewId;
   FlutterEngineSendWindowMetricsEvent(g_state.engine, &event);
 }
 

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -898,12 +898,6 @@ - (nonnull NSString*)executableName {
 }
 
 - (void)updateWindowMetricsForViewController:(FlutterViewController*)viewController {
-  if (viewController.viewId != kFlutterImplicitViewId) {
-    // TODO(dkwingsmt): The embedder API only supports single-view for now. As
-    // embedder APIs are converted to multi-view, this method should support any
-    // views.
-    return;
-  }
   if (!_engine || !viewController || !viewController.viewLoaded) {
     return;
   }
@@ -922,6 +916,7 @@ - (void)updateWindowMetricsForViewController:(FlutterViewController*)viewControl
       .left = static_cast<size_t>(scaledBounds.origin.x),
       .top = static_cast<size_t>(scaledBounds.origin.y),
       .display_id = static_cast<uint64_t>(displayId),
+      .view_id = viewController.viewId,
   };
   _embedderAPI.SendWindowMetricsEvent(_engine, &windowMetricsEvent);
 }

shell/platform/embedder/embedder.cc

@@ -2143,8 +2143,8 @@ FlutterEngineResult FlutterEngineSendWindowMetricsEvent(
   if (engine == nullptr || flutter_metrics == nullptr) {
     return LOG_EMBEDDER_ERROR(kInvalidArguments, "Engine handle was invalid.");
   }
-  // TODO(dkwingsmt): Use a real view ID when multiview is supported.
-  int64_t view_id = kFlutterImplicitViewId;
+  FlutterViewId view_id =
+      SAFE_ACCESS(flutter_metrics, view_id, kFlutterImplicitViewId);
 
   flutter::ViewportMetrics metrics;
 

shell/platform/embedder/embedder.h

@@ -859,6 +859,8 @@ typedef struct {
   double physical_view_inset_left;
   /// The identifier of the display the view is rendering on.
   FlutterEngineDisplayId display_id;
+  /// The view that this event is describing.
+  int64_t view_id;
 } FlutterWindowMetricsEvent;
 
 /// The phase of the pointer event.

shell/platform/embedder/fixtures/main.dart

@@ -1334,6 +1334,42 @@ void pointer_data_packet_view_id() {
   signalNativeTest();
 }
 
+Map<int, Size> _getAllViewSizes() {
+  final Map<int, Size> result = <int, Size>{};
+  for (final FlutterView view in PlatformDispatcher.instance.views) {
+    result[view.viewId] = view.physicalSize;
+  }
+  return result;
+}
+
+List<int> _findDifferences(Map<int, Size> a, Map<int, Size> b) {
+  final Set<int> result = <int>{};
+  a.forEach((int viewId, Size sizeA) {
+    if (!b.containsKey(viewId) || b[viewId] != sizeA) {
+      result.add(viewId);
+    }
+  });
+  b.forEach((int viewId, Size sizeB) {
+    if (!a.containsKey(viewId)) {
+      result.add(viewId);
+    }
+  });
+  return result.toList()..sort();
+}
+
+@pragma('vm:entry-point')
+void window_metrics_event_view_id() {
+  Map<int, Size> sizes = _getAllViewSizes();
+  PlatformDispatcher.instance.onMetricsChanged = () {
+    final Map<int, Size> newSizes = _getAllViewSizes();
+    final List<int> differences = _findDifferences(sizes, newSizes);
+    sizes = newSizes;
+    signalNativeMessage('Changed: $differences');
+  };
+
+  signalNativeTest();
+}
+
 @pragma('vm:entry-point')
 Future<void> channel_listener_response() async {
   channelBuffers.setListener('test/listen',

shell/platform/embedder/tests/embedder_unittests.cc

@@ -2726,7 +2726,7 @@ TEST_F(EmbedderTest, CanSendPointer) {
 
 /// Send a pointer event to Dart and wait until the Dart code echos with the
 /// view ID.
-TEST_F(EmbedderTest, CanSendPointerWithViewId) {
+TEST_F(EmbedderTest, CanSendPointerEventWithViewId) {
   auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
   EmbedderConfigBuilder builder(context);
   builder.SetSoftwareRendererConfig();
@@ -2766,6 +2766,103 @@ TEST_F(EmbedderTest, CanSendPointerWithViewId) {
   message_latch.Wait();
 }
 
+TEST_F(EmbedderTest, WindowMetricsEventDefaultsToImplicitView) {
+  auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
+  EmbedderConfigBuilder builder(context);
+  builder.SetSoftwareRendererConfig();
+  builder.SetDartEntrypoint("window_metrics_event_view_id");
+
+  fml::AutoResetWaitableEvent ready_latch, message_latch;
+  context.AddNativeCallback(
+      "SignalNativeTest",
+      CREATE_NATIVE_ENTRY(
+          [&ready_latch](Dart_NativeArguments args) { ready_latch.Signal(); }));
+  context.AddNativeCallback(
+      "SignalNativeMessage",
+      CREATE_NATIVE_ENTRY([&message_latch](Dart_NativeArguments args) {
+        auto message = tonic::DartConverter<std::string>::FromDart(
+            Dart_GetNativeArgument(args, 0));
+        ASSERT_EQ("Changed: [0]", message);
+        message_latch.Signal();
+      }));
+
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+
+  ready_latch.Wait();
+
+  FlutterWindowMetricsEvent event = {};
+  // Simulate an event that comes from an old version of embedder.h that doesn't
+  // have the view_id field.
+  event.struct_size = offsetof(FlutterWindowMetricsEvent, view_id);
+  event.width = 200;
+  event.height = 300;
+  event.pixel_ratio = 1.5;
+  // Skip assigning event.view_id here to test the default behavior.
+
+  FlutterEngineResult result =
+      FlutterEngineSendWindowMetricsEvent(engine.get(), &event);
+  ASSERT_EQ(result, kSuccess);
+
+  message_latch.Wait();
+}
+
+TEST_F(EmbedderTest, IgnoresWindowMetricsEventForUnknownView) {
+  auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
+  EmbedderConfigBuilder builder(context);
+  builder.SetSoftwareRendererConfig();
+  builder.SetDartEntrypoint("window_metrics_event_view_id");
+
+  fml::AutoResetWaitableEvent ready_latch, message_latch;
+  context.AddNativeCallback(
+      "SignalNativeTest",
+      CREATE_NATIVE_ENTRY(
+          [&ready_latch](Dart_NativeArguments args) { ready_latch.Signal(); }));
+
+  context.AddNativeCallback(
+      "SignalNativeMessage",
+      CREATE_NATIVE_ENTRY([&message_latch](Dart_NativeArguments args) {
+        auto message = tonic::DartConverter<std::string>::FromDart(
+            Dart_GetNativeArgument(args, 0));
+        // Message latch should only be signaled once as the bad
+        // view metric should be dropped by the engine.
+        ASSERT_FALSE(message_latch.IsSignaledForTest());
+        ASSERT_EQ("Changed: [0]", message);
+        message_latch.Signal();
+      }));
+
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+
+  ready_latch.Wait();
+
+  // Send a window metric for a nonexistent view, which should be dropped by the
+  // engine.
+  FlutterWindowMetricsEvent bad_event = {};
+  bad_event.struct_size = sizeof(FlutterWindowMetricsEvent);
+  bad_event.width = 200;
+  bad_event.height = 300;
+  bad_event.pixel_ratio = 1.5;
+  bad_event.view_id = 100;
+
+  FlutterEngineResult result =
+      FlutterEngineSendWindowMetricsEvent(engine.get(), &bad_event);
+  ASSERT_EQ(result, kSuccess);
+
+  // Send a window metric for a valid view. The engine notifies the Dart app.
+  FlutterWindowMetricsEvent event = {};
+  event.struct_size = sizeof(FlutterWindowMetricsEvent);
+  event.width = 200;
+  event.height = 300;
+  event.pixel_ratio = 1.5;
+  event.view_id = 0;
+
+  result = FlutterEngineSendWindowMetricsEvent(engine.get(), &event);
+  ASSERT_EQ(result, kSuccess);
+
+  message_latch.Wait();
+}
+
 TEST_F(EmbedderTest, RegisterChannelListener) {
   auto& context = GetEmbedderContext(EmbedderTestContextType::kSoftwareContext);
 

shell/platform/glfw/flutter_glfw.cc

@@ -297,6 +297,9 @@ static void SendWindowMetrics(FlutterDesktopWindowControllerState* controller,
   } else {
     event.pixel_ratio = controller->window_wrapper->pixel_ratio_override;
   }
+  // The GLFW embedder doesn't support multiple views. We assume all pointer
+  // events come from the only view, the implicit view.
+  event.view_id = flutter::kFlutterImplicitViewId;
   FlutterEngineSendWindowMetricsEvent(controller->engine->flutter_engine,
                                       &event);
 }

shell/platform/linux/fl_engine.cc

@@ -760,6 +760,10 @@ void fl_engine_send_window_metrics_event(FlEngine* self,
   event.width = width;
   event.height = height;
   event.pixel_ratio = pixel_ratio;
+  // TODO(dkwingsmt): Assign the correct view ID once the Linux embedder
+  // supports multiple views.
+  // https://github.com/flutter/flutter/issues/138178
+  event.view_id = flutter::kFlutterImplicitViewId;
   self->embedder_api.SendWindowMetricsEvent(self->engine, &event);
 }
 

shell/platform/windows/flutter_windows_view.cc

@@ -352,6 +352,7 @@ void FlutterWindowsView::SendWindowMetrics(size_t width,
   event.width = width;
   event.height = height;
   event.pixel_ratio = dpiScale;
+  event.view_id = view_id_;
   engine_->SendWindowMetricsEvent(event);
 }
 
@@ -588,10 +589,7 @@ void FlutterWindowsView::SendPointerEventWithData(
   event.device_kind = state->device_kind;
   event.device = state->pointer_id;
   event.buttons = state->buttons;
-  // TODO(dkwingsmt): Use the correct view ID for pointer events once the
-  // Windows embedder supports multiple views.
-  // https://github.com/flutter/flutter/issues/138179
-  event.view_id = flutter::kFlutterImplicitViewId;
+  event.view_id = view_id_;
 
   // Set metadata that's always the same regardless of the event.
   event.struct_size = sizeof(event);