[Embedder] Wire view focus event and focus request (#163930)

This wires `PlatformDispatcher.onViewFocusChange` and
`PlatformDispatches.requestViewFocusChange` through embedder API.

*If you had to change anything in the [flutter/tests] repo, include a
link to the migration guide as per the [breaking change policy].*

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I readand followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

---------

Co-authored-by: Matthew Kosarek <matt.kosarek@canonical.com>
Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -42555,6 +42555,8 @@ ORIGIN: ../../../flutter/lib/ui/window/pointer_data_packet.cc + ../../../flutter
 ORIGIN: ../../../flutter/lib/ui/window/pointer_data_packet.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/window/pointer_data_packet_converter.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/window/pointer_data_packet_converter.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/ui/window/view_focus.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/ui/window/view_focus.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/window/viewport_metrics.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/window/viewport_metrics.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/flutter_js/src/browser_environment.js + ../../../flutter/LICENSE
@@ -45471,6 +45473,8 @@ FILE: ../../../flutter/lib/ui/window/pointer_data_packet.cc
 FILE: ../../../flutter/lib/ui/window/pointer_data_packet.h
 FILE: ../../../flutter/lib/ui/window/pointer_data_packet_converter.cc
 FILE: ../../../flutter/lib/ui/window/pointer_data_packet_converter.h
+FILE: ../../../flutter/lib/ui/window/view_focus.cc
+FILE: ../../../flutter/lib/ui/window/view_focus.h
 FILE: ../../../flutter/lib/ui/window/viewport_metrics.cc
 FILE: ../../../flutter/lib/ui/window/viewport_metrics.h
 FILE: ../../../flutter/lib/web_ui/flutter_js/src/browser_environment.js

engine/src/flutter/lib/ui/BUILD.gn

@@ -156,6 +156,8 @@ source_set("ui") {
     "window/pointer_data_packet.h",
     "window/pointer_data_packet_converter.cc",
     "window/pointer_data_packet_converter.h",
+    "window/view_focus.cc",
+    "window/view_focus.h",
     "window/viewport_metrics.cc",
     "window/viewport_metrics.h",
   ]

engine/src/flutter/lib/ui/dart_ui.cc

@@ -107,6 +107,7 @@ typedef CanvasPath Path;
   V(PlatformConfigurationNativeApi::GetRootIsolateToken)           \
   V(PlatformConfigurationNativeApi::RegisterBackgroundIsolate)     \
   V(PlatformConfigurationNativeApi::SendPortPlatformMessage)       \
+  V(PlatformConfigurationNativeApi::RequestViewFocusChange)        \
   V(PlatformConfigurationNativeApi::SendChannelUpdate)             \
   V(PlatformConfigurationNativeApi::GetScaledFontSize)             \
   V(PlatformIsolateNativeApi::IsRunningOnPlatformThread)           \

engine/src/flutter/lib/ui/hooks.dart

@@ -58,6 +58,16 @@ void _removeView(int viewId) {
   PlatformDispatcher.instance._removeView(viewId);
 }
 
+@pragma('vm:entry-point')
+void _sendViewFocusEvent(int viewId, int viewFocusState, int viewFocusDirection) {
+  final ViewFocusEvent viewFocusEvent = ViewFocusEvent(
+    viewId: viewId,
+    state: ViewFocusState.values[viewFocusState],
+    direction: ViewFocusDirection.values[viewFocusDirection],
+  );
+  PlatformDispatcher.instance._sendViewFocusEvent(viewFocusEvent);
+}
+
 @pragma('vm:entry-point')
 void _updateDisplays(
   List<int> ids,

engine/src/flutter/lib/ui/platform_dispatcher.dart

@@ -301,6 +301,10 @@ class PlatformDispatcher {
     _invoke(onMetricsChanged, _onMetricsChangedZone);
   }
 
+  void _sendViewFocusEvent(ViewFocusEvent event) {
+    _invoke1<ViewFocusEvent>(onViewFocusChange, _onViewFocusChangeZone, event);
+  }
+
   // Called from the engine, via hooks.dart.
   //
   // Updates the available displays.
@@ -384,9 +388,14 @@ class PlatformDispatcher {
     required ViewFocusState state,
     required ViewFocusDirection direction,
   }) {
-    // TODO(tugorez): implement this method. At the moment will be a no op call.
+    _requestViewFocusChange(viewId, state.index, direction.index);
   }
 
+  @Native<Void Function(Int64, Int64, Int64)>(
+    symbol: 'PlatformConfigurationNativeApi::RequestViewFocusChange',
+  )
+  external static void _requestViewFocusChange(int viewId, int state, int direction);
+
   /// A callback invoked when any view begins a frame.
   ///
   /// A callback that is invoked to notify the application that it is an

engine/src/flutter/lib/ui/window/platform_configuration.cc

@@ -46,6 +46,9 @@ void PlatformConfiguration::DidCreateIsolate() {
                 Dart_GetField(library, tonic::ToDart("_addView")));
   remove_view_.Set(tonic::DartState::Current(),
                    Dart_GetField(library, tonic::ToDart("_removeView")));
+  send_view_focus_event_.Set(
+      tonic::DartState::Current(),
+      Dart_GetField(library, tonic::ToDart("_sendViewFocusEvent")));
   update_window_metrics_.Set(
       tonic::DartState::Current(),
       Dart_GetField(library, tonic::ToDart("_updateWindowMetrics")));
@@ -149,6 +152,22 @@ bool PlatformConfiguration::RemoveView(int64_t view_id) {
   return true;
 }
 
+bool PlatformConfiguration::SendFocusEvent(const ViewFocusEvent& event) {
+  std::shared_ptr<tonic::DartState> dart_state =
+      remove_view_.dart_state().lock();
+  if (!dart_state) {
+    return false;
+  }
+  tonic::DartState::Scope scope(dart_state);
+  tonic::CheckAndHandleError(tonic::DartInvoke(
+      send_view_focus_event_.Get(), {
+                                        tonic::ToDart(event.view_id()),
+                                        tonic::ToDart(event.state()),
+                                        tonic::ToDart(event.direction()),
+                                    }));
+  return true;
+}
+
 bool PlatformConfiguration::UpdateViewMetrics(
     int64_t view_id,
     const ViewportMetrics& view_metrics) {
@@ -552,6 +571,17 @@ Dart_Handle PlatformConfigurationNativeApi::SendPortPlatformMessage(
   return HandlePlatformMessage(dart_state, name, data_handle, response);
 }
 
+void PlatformConfigurationNativeApi::RequestViewFocusChange(int64_t view_id,
+                                                            int64_t state,
+                                                            int64_t direction) {
+  ViewFocusChangeRequest request{view_id,  //
+                                 static_cast<ViewFocusState>(state),
+                                 static_cast<ViewFocusDirection>(direction)};
+  UIDartState* dart_state = UIDartState::Current();
+  dart_state->platform_configuration()->client()->RequestViewFocusChange(
+      request);
+}
+
 void PlatformConfigurationNativeApi::RespondToPlatformMessage(
     int response_id,
     const tonic::DartByteData& data) {

engine/src/flutter/lib/ui/window/platform_configuration.h

@@ -16,6 +16,7 @@
 #include "flutter/lib/ui/semantics/semantics_update.h"
 #include "flutter/lib/ui/window/platform_message_response.h"
 #include "flutter/lib/ui/window/pointer_data_packet.h"
+#include "flutter/lib/ui/window/view_focus.h"
 #include "flutter/lib/ui/window/viewport_metrics.h"
 #include "flutter/shell/common/display.h"
 #include "fml/macros.h"
@@ -257,6 +258,14 @@ class PlatformConfigurationClient {
   virtual double GetScaledFontSize(double unscaled_font_size,
                                    int configuration_id) const = 0;
 
+  //--------------------------------------------------------------------------
+  /// @brief      Notifies the client that the Flutter view focus state has
+  ///             changed and the platform view should be updated.
+  ///
+  /// @param[in]  request  The request to change the focus state of the view.
+  virtual void RequestViewFocusChange(
+      const ViewFocusChangeRequest& request) = 0;
+
   virtual std::shared_ptr<PlatformIsolateManager>
   GetPlatformIsolateManager() = 0;
 
@@ -338,6 +347,15 @@ class PlatformConfiguration final {
   ///
   bool RemoveView(int64_t view_id);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Notify the isolate that the focus state of a native view has
+  ///             changed.
+  ///
+  /// @param[in]  event  The focus event describing the change.
+  ///
+  /// @return     Whether the focus event was sent.
+  bool SendFocusEvent(const ViewFocusEvent& event);
+
   //----------------------------------------------------------------------------
   /// @brief      Update the view metrics for the specified view.
   ///
@@ -529,6 +547,7 @@ class PlatformConfiguration final {
   tonic::DartPersistentValue on_error_;
   tonic::DartPersistentValue add_view_;
   tonic::DartPersistentValue remove_view_;
+  tonic::DartPersistentValue send_view_focus_event_;
   tonic::DartPersistentValue update_window_metrics_;
   tonic::DartPersistentValue update_displays_;
   tonic::DartPersistentValue update_locales_;
@@ -617,6 +636,10 @@ class PlatformConfigurationNativeApi {
 
   static void SendChannelUpdate(const std::string& name, bool listening);
 
+  static void RequestViewFocusChange(int64_t view_id,
+                                     int64_t state,
+                                     int64_t direction);
+
   //--------------------------------------------------------------------------
   /// @brief      Requests the Dart VM to adjusts the GC heuristics based on
   ///             the requested `performance_mode`. Returns the old performance

engine/src/flutter/lib/ui/window/view_focus.cc

@@ -0,0 +1,23 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/lib/ui/window/view_focus.h"
+
+namespace flutter {
+ViewFocusChangeRequest::ViewFocusChangeRequest(int64_t view_id,
+                                               ViewFocusState state,
+                                               ViewFocusDirection direction)
+    : view_id_(view_id), state_(state), direction_(direction) {}
+
+int64_t ViewFocusChangeRequest::view_id() const {
+  return view_id_;
+}
+ViewFocusState ViewFocusChangeRequest::state() const {
+  return state_;
+}
+ViewFocusDirection ViewFocusChangeRequest::direction() const {
+  return direction_;
+}
+
+}  // namespace flutter

engine/src/flutter/lib/ui/window/view_focus.h

@@ -0,0 +1,69 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_LIB_UI_WINDOW_VIEW_FOCUS_H_
+#define FLUTTER_LIB_UI_WINDOW_VIEW_FOCUS_H_
+
+#include <cstdint>
+
+namespace flutter {
+
+// Focus state of a View.
+// Must match ViewFocusState in ui/platform_dispatcher.dart.
+enum class ViewFocusState : int64_t {
+  kUnfocused = 0,
+  kFocused,
+};
+
+// Represents the direction of which the focus transitioned over
+// a FlutterView.
+// Must match ViewFocusDirection in ui/platform_dispatcher.dart.
+enum class ViewFocusDirection : int64_t {
+  kUndefined = 0,
+  kForward,
+  kBackward,
+};
+
+// Event sent by the embedder to the engine indicating that native view focus
+// state has changed.
+class ViewFocusEvent {
+ public:
+  ViewFocusEvent(int64_t view_id,
+                 ViewFocusState state,
+                 ViewFocusDirection direction)
+      : view_id_(view_id), state_(state), direction_(direction) {}
+
+  int64_t view_id() const { return view_id_; }
+  ViewFocusState state() const { return state_; }
+  ViewFocusDirection direction() const { return direction_; }
+
+ private:
+  int64_t view_id_;
+  ViewFocusState state_;
+  ViewFocusDirection direction_;
+};
+
+// Request sent by the engine to the embedder indicating that the FlutterView
+// focus state has changed and the native view should be updated.
+class ViewFocusChangeRequest {
+ public:
+  ViewFocusChangeRequest(int64_t view_id,
+                         ViewFocusState state,
+                         ViewFocusDirection direction);
+
+  int64_t view_id() const;
+  ViewFocusState state() const;
+  ViewFocusDirection direction() const;
+
+ private:
+  ViewFocusChangeRequest() = delete;
+
+  int64_t view_id_ = 0;
+  ViewFocusState state_ = ViewFocusState::kUnfocused;
+  ViewFocusDirection direction_ = ViewFocusDirection::kUndefined;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_LIB_UI_WINDOW_VIEW_FOCUS_H_

engine/src/flutter/runtime/dart_isolate_unittests.cc

@@ -735,6 +735,7 @@ class FakePlatformConfigurationClient : public PlatformConfigurationClient {
                            int configuration_id) const override {
     return 0;
   }
+  void RequestViewFocusChange(const ViewFocusChangeRequest& request) override {}
 };
 
 TEST_F(DartIsolateTest, PlatformIsolateCreationAndShutdown) {

engine/src/flutter/runtime/runtime_controller.cc

@@ -209,6 +209,14 @@ bool RuntimeController::RemoveView(int64_t view_id) {
   return platform_configuration->RemoveView(view_id);
 }
 
+bool RuntimeController::SendViewFocusEvent(const ViewFocusEvent& event) {
+  auto* platform_configuration = GetPlatformConfigurationIfAvailable();
+  if (!platform_configuration) {
+    return false;
+  }
+  return platform_configuration->SendFocusEvent(event);
+}
+
 bool RuntimeController::ViewExists(int64_t view_id) const {
   return platform_data_.viewport_metrics_for_views.count(view_id) != 0;
 }
@@ -649,6 +657,11 @@ double RuntimeController::GetScaledFontSize(double unscaled_font_size,
   return client_.GetScaledFontSize(unscaled_font_size, configuration_id);
 }
 
+void RuntimeController::RequestViewFocusChange(
+    const ViewFocusChangeRequest& request) {
+  client_.RequestViewFocusChange(request);
+}
+
 void RuntimeController::ShutdownPlatformIsolates() {
   platform_isolate_manager_->ShutdownPlatformIsolates();
 }

engine/src/flutter/runtime/runtime_controller.h

@@ -20,6 +20,7 @@
 #include "flutter/lib/ui/window/platform_configuration.h"
 #include "flutter/lib/ui/window/pointer_data_packet.h"
 #include "flutter/lib/ui/window/pointer_data_packet_converter.h"
+#include "flutter/lib/ui/window/view_focus.h"
 #include "flutter/runtime/dart_vm.h"
 #include "flutter/runtime/platform_data.h"
 #include "flutter/runtime/platform_isolate_manager.h"
@@ -224,6 +225,13 @@ class RuntimeController : public PlatformConfigurationClient,
   ///             cancelled and the return value is always false.
   bool RemoveView(int64_t view_id);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Notify the isolate that the focus state of a native view has
+  ///             changed.
+  ///
+  /// @param[in]  event  The focus event describing the change.
+  bool SendViewFocusEvent(const ViewFocusEvent& event);
+
   //----------------------------------------------------------------------------
   /// @brief      Forward the specified viewport metrics to the running isolate.
   ///             If the isolate is not running, these metrics will be saved and
@@ -785,6 +793,9 @@ class RuntimeController : public PlatformConfigurationClient,
   double GetScaledFontSize(double unscaled_font_size,
                            int configuration_id) const override;
 
+  // |PlatformConfigurationClient|
+  void RequestViewFocusChange(const ViewFocusChangeRequest& request) override;
+
   FML_DISALLOW_COPY_AND_ASSIGN(RuntimeController);
 };
 

engine/src/flutter/runtime/runtime_delegate.h

@@ -14,6 +14,7 @@
 #include "flutter/lib/ui/semantics/semantics_node.h"
 #include "flutter/lib/ui/text/font_collection.h"
 #include "flutter/lib/ui/window/platform_message.h"
+#include "flutter/lib/ui/window/view_focus.h"
 #include "flutter/shell/common/platform_message_handler.h"
 #include "third_party/dart/runtime/include/dart_api.h"
 
@@ -62,6 +63,9 @@ class RuntimeDelegate {
   virtual double GetScaledFontSize(double unscaled_font_size,
                                    int configuration_id) const = 0;
 
+  virtual void RequestViewFocusChange(
+      const ViewFocusChangeRequest& request) = 0;
+
  protected:
   virtual ~RuntimeDelegate();
 };

engine/src/flutter/shell/common/engine.cc

@@ -312,6 +312,10 @@ bool Engine::RemoveView(int64_t view_id) {
   return runtime_controller_->RemoveView(view_id);
 }
 
+bool Engine::SendViewFocusEvent(const ViewFocusEvent& event) {
+  return runtime_controller_->SendViewFocusEvent(event);
+}
+
 void Engine::SetViewportMetrics(int64_t view_id,
                                 const ViewportMetrics& metrics) {
   runtime_controller_->SetViewportMetrics(view_id, metrics);
@@ -522,6 +526,10 @@ double Engine::GetScaledFontSize(double unscaled_font_size,
   return delegate_.GetScaledFontSize(unscaled_font_size, configuration_id);
 }
 
+void Engine::RequestViewFocusChange(const ViewFocusChangeRequest& request) {
+  delegate_.RequestViewFocusChange(request);
+}
+
 void Engine::SetNeedsReportTimings(bool needs_reporting) {
   delegate_.SetNeedsReportTimings(needs_reporting);
 }

engine/src/flutter/shell/common/engine.h

@@ -323,6 +323,14 @@ class Engine final : public RuntimeDelegate, PointerDataDispatcher::Delegate {
     ///
     virtual double GetScaledFontSize(double unscaled_font_size,
                                      int configuration_id) const = 0;
+
+    //--------------------------------------------------------------------------
+    /// @brief      Notifies the client that the Flutter view focus state has
+    ///             changed and the platform view should be updated.
+    ///
+    /// @param[in]  request  The request to change the focus state of the view.
+    virtual void RequestViewFocusChange(
+        const ViewFocusChangeRequest& request) = 0;
   };
 
   //----------------------------------------------------------------------------
@@ -747,6 +755,13 @@ class Engine final : public RuntimeDelegate, PointerDataDispatcher::Delegate {
   ///
   bool RemoveView(int64_t view_id);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Notify the Flutter application that the focus state of a
+  ///             native view has changed.
+  ///
+  /// @param[in]  event  The focus event describing the change.
+  bool SendViewFocusEvent(const ViewFocusEvent& event);
+
   //----------------------------------------------------------------------------
   /// @brief      Updates the viewport metrics for a view. The viewport metrics
   ///             detail the size of the rendering viewport in texels as well as
@@ -1024,6 +1039,9 @@ class Engine final : public RuntimeDelegate, PointerDataDispatcher::Delegate {
   double GetScaledFontSize(double unscaled_font_size,
                            int configuration_id) const override;
 
+  // |RuntimeDelegate|
+  void RequestViewFocusChange(const ViewFocusChangeRequest& request) override;
+
   void SetNeedsReportTimings(bool value) override;
 
   bool HandleLifecyclePlatformMessage(PlatformMessage* message);

engine/src/flutter/shell/common/engine_animator_unittests.cc

@@ -82,6 +82,10 @@ class MockDelegate : public Engine::Delegate {
               GetScaledFontSize,
               (double font_size, int configuration_id),
               (const, override));
+  MOCK_METHOD(void,
+              RequestViewFocusChange,
+              (const ViewFocusChangeRequest&),
+              (override));
 };
 
 class MockAnimatorDelegate : public Animator::Delegate {

engine/src/flutter/shell/common/engine_unittests.cc

@@ -90,6 +90,10 @@ class MockDelegate : public Engine::Delegate {
               GetScaledFontSize,
               (double font_size, int configuration_id),
               (const, override));
+  MOCK_METHOD(void,
+              RequestViewFocusChange,
+              (const ViewFocusChangeRequest&),
+              (override));
 };
 
 class MockResponse : public PlatformMessageResponse {
@@ -137,6 +141,10 @@ class MockRuntimeDelegate : public RuntimeDelegate {
               GetScaledFontSize,
               (double font_size, int configuration_id),
               (const, override));
+  MOCK_METHOD(void,
+              RequestViewFocusChange,
+              (const ViewFocusChangeRequest&),
+              (override));
 };
 
 class MockRuntimeController : public RuntimeController {

engine/src/flutter/shell/common/fixtures/shell_test.dart

@@ -632,3 +632,11 @@ void testDispatchEvents() {
     notifyNative();
   };
 }
+
+@pragma('vm:entry-point')
+void testSendViewFocusEvent() {
+  PlatformDispatcher.instance.onViewFocusChange = (ViewFocusEvent event) {
+    notifyMessage('${event.viewId} ${event.state} ${event.direction}');
+  };
+  notifyNative();
+}

engine/src/flutter/shell/common/platform_view.cc

@@ -97,6 +97,10 @@ void PlatformView::RemoveView(int64_t view_id, RemoveViewCallback callback) {
   delegate_.OnPlatformViewRemoveView(view_id, std::move(callback));
 }
 
+void PlatformView::SendViewFocusEvent(const ViewFocusEvent& event) {
+  delegate_.OnPlatformViewSendViewFocusEvent(event);
+}
+
 sk_sp<GrDirectContext> PlatformView::CreateResourceContext() const {
   FML_DLOG(WARNING) << "This platform does not set up the resource "
                        "context on the IO thread for async texture uploads.";
@@ -219,4 +223,9 @@ double PlatformView::GetScaledFontSize(double unscaled_font_size,
   return -1;
 }
 
+void PlatformView::RequestViewFocusChange(
+    const ViewFocusChangeRequest& request) {
+  // No-op by default.
+}
+
 }  // namespace flutter

engine/src/flutter/shell/common/platform_view.h

@@ -121,6 +121,12 @@ class PlatformView {
     virtual void OnPlatformViewRemoveView(int64_t view_id,
                                           RemoveViewCallback callback) = 0;
 
+    /// @brief Notify the delegate that platform view focus state has changed.
+    ///
+    /// @param[in]  event  The focus event describing the change.
+    virtual void OnPlatformViewSendViewFocusEvent(
+        const ViewFocusEvent& event) = 0;
+
     //--------------------------------------------------------------------------
     /// @brief      Notifies the delegate that the specified callback needs to
     ///             be invoked after the rasterizer is done rendering the next
@@ -605,6 +611,8 @@ class PlatformView {
   ///
   void RemoveView(int64_t view_id, RemoveViewCallback callback);
 
+  void SendViewFocusEvent(const ViewFocusEvent& event);
+
   //----------------------------------------------------------------------------
   /// @brief      Used by the shell to obtain a Skia GPU context that is capable
   ///             of operating on the IO thread. The context must be in the same
@@ -954,6 +962,15 @@ class PlatformView {
   virtual double GetScaledFontSize(double unscaled_font_size,
                                    int configuration_id) const;
 
+  //--------------------------------------------------------------------------
+  /// @brief      Notifies the client that the Flutter view focus state has
+  ///             changed and the platform view should be updated.
+  ///
+  ///             Called on platform thread.
+  ///
+  /// @param[in]  request  The request to change the focus state of the view.
+  virtual void RequestViewFocusChange(const ViewFocusChangeRequest& request);
+
  protected:
   // This is the only method called on the raster task runner.
   virtual std::unique_ptr<Surface> CreateRenderingSurface();

engine/src/flutter/shell/common/shell.cc

@@ -1550,6 +1550,18 @@ double Shell::GetScaledFontSize(double unscaled_font_size,
                                            configuration_id);
 }
 
+void Shell::RequestViewFocusChange(const ViewFocusChangeRequest& request) {
+  FML_DCHECK(is_set_up_);
+
+  fml::TaskRunner::RunNowOrPostTask(
+      task_runners_.GetPlatformTaskRunner(),
+      [view = platform_view_->GetWeakPtr(), request] {
+        if (view) {
+          view->RequestViewFocusChange(request);
+        }
+      });
+}
+
 void Shell::ReportTimings() {
   FML_DCHECK(is_set_up_);
   FML_DCHECK(task_runners_.GetRasterTaskRunner()->RunsTasksOnCurrentThread());
@@ -2102,6 +2114,20 @@ void Shell::OnPlatformViewRemoveView(int64_t view_id,
       });
 }
 
+void Shell::OnPlatformViewSendViewFocusEvent(const ViewFocusEvent& event) {
+  TRACE_EVENT0("flutter", "Shell:: OnPlatformViewSendViewFocusEvent");
+  FML_DCHECK(is_set_up_);
+  FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
+
+  task_runners_.GetUITaskRunner()->RunNowOrPostTask(
+      task_runners_.GetUITaskRunner(),
+      [engine = engine_->GetWeakPtr(), event = event] {
+        if (engine) {
+          engine->SendViewFocusEvent(event);
+        }
+      });
+}
+
 Rasterizer::Screenshot Shell::Screenshot(
     Rasterizer::ScreenshotType screenshot_type,
     bool base64_encode) {

engine/src/flutter/shell/common/shell.h

@@ -588,6 +588,9 @@ class Shell final : public PlatformView::Delegate,
   void OnPlatformViewRemoveView(int64_t view_id,
                                 RemoveViewCallback callback) override;
 
+  // |PlatformView::Delegate|
+  void OnPlatformViewSendViewFocusEvent(const ViewFocusEvent& event) override;
+
   // |PlatformView::Delegate|
   void OnPlatformViewSetViewportMetrics(
       int64_t view_id,
@@ -702,6 +705,9 @@ class Shell final : public PlatformView::Delegate,
   double GetScaledFontSize(double unscaled_font_size,
                            int configuration_id) const override;
 
+  // |Engine::Delegate|
+  void RequestViewFocusChange(const ViewFocusChangeRequest& request) override;
+
   // |Rasterizer::Delegate|
   void OnFrameRasterized(const FrameTiming&) override;
 

engine/src/flutter/shell/common/shell_unittests.cc

@@ -116,6 +116,11 @@ class MockPlatformViewDelegate : public PlatformView::Delegate {
               (int64_t view_id, RemoveViewCallback callback),
               (override));
 
+  MOCK_METHOD(void,
+              OnPlatformViewSendViewFocusEvent,
+              (const ViewFocusEvent& event),
+              (override));
+
   MOCK_METHOD(void,
               OnPlatformViewSetNextFrameCallback,
               (const fml::closure& closure),
@@ -4952,6 +4957,56 @@ TEST_F(ShellTest, WillLogWarningWhenImpellerIsOptedOut) {
   DestroyShell(std::move(shell), task_runners);
 }
 
+TEST_F(ShellTest, SendViewFocusEvent) {
+  Settings settings = CreateSettingsForFixture();
+  TaskRunners task_runners = GetTaskRunnersForFixture();
+  fml::AutoResetWaitableEvent latch;
+  std::string last_event;
+
+  AddNativeCallback(
+      "NotifyNative",
+      CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) { latch.Signal(); }));
+
+  AddNativeCallback("NotifyMessage",
+                    CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
+                      const auto message_from_dart =
+                          tonic::DartConverter<std::string>::FromDart(
+                              Dart_GetNativeArgument(args, 0));
+                      last_event = message_from_dart;
+                      latch.Signal();
+                    }));
+  fml::AutoResetWaitableEvent check_latch;
+
+  std::unique_ptr<Shell> shell = CreateShell(settings, task_runners);
+  ASSERT_TRUE(shell->IsSetup());
+
+  auto configuration = RunConfiguration::InferFromSettings(settings);
+
+  configuration.SetEntrypoint("testSendViewFocusEvent");
+  RunEngine(shell.get(), std::move(configuration));
+  latch.Wait();
+  latch.Reset();
+
+  PostSync(shell->GetTaskRunners().GetPlatformTaskRunner(), [&shell]() {
+    shell->GetPlatformView()->SendViewFocusEvent(ViewFocusEvent(
+        1, ViewFocusState::kFocused, ViewFocusDirection::kUndefined));
+  });
+  latch.Wait();
+  ASSERT_EQ(last_event,
+            "1 ViewFocusState.focused ViewFocusDirection.undefined");
+
+  latch.Reset();
+  PostSync(shell->GetTaskRunners().GetPlatformTaskRunner(), [&shell]() {
+    shell->GetPlatformView()->SendViewFocusEvent(ViewFocusEvent(
+        2, ViewFocusState::kUnfocused, ViewFocusDirection::kBackward));
+  });
+  latch.Wait();
+  ASSERT_EQ(last_event,
+            "2 ViewFocusState.unfocused ViewFocusDirection.backward");
+
+  DestroyShell(std::move(shell), task_runners);
+}
+
 }  // namespace testing
 }  // namespace flutter
 

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterEnginePlatformViewTest.mm

@@ -28,6 +28,7 @@ class FakeDelegate : public PlatformView::Delegate {
                              const ViewportMetrics& viewport_metrics,
                              AddViewCallback callback) override {}
   void OnPlatformViewRemoveView(int64_t view_id, RemoveViewCallback callback) override {}
+  void OnPlatformViewSendViewFocusEvent(const ViewFocusEvent& event) override {}
   void OnPlatformViewSetNextFrameCallback(const fml::closure& closure) override {}
   void OnPlatformViewSetViewportMetrics(int64_t view_id, const ViewportMetrics& metrics) override {}
   const flutter::Settings& OnPlatformViewGetSettings() const override { return settings_; }

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsTest.mm

@@ -263,6 +263,7 @@ class FlutterPlatformViewsTestMockPlatformViewDelegate : public PlatformView::De
                              const ViewportMetrics& viewport_metrics,
                              AddViewCallback callback) override {}
   void OnPlatformViewRemoveView(int64_t view_id, RemoveViewCallback callback) override {}
+  void OnPlatformViewSendViewFocusEvent(const ViewFocusEvent& event) override {};
   void OnPlatformViewSetNextFrameCallback(const fml::closure& closure) override {}
   void OnPlatformViewSetViewportMetrics(int64_t view_id, const ViewportMetrics& metrics) override {}
   const flutter::Settings& OnPlatformViewGetSettings() const override { return settings_; }

engine/src/flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge_test.mm

@@ -75,6 +75,7 @@ class MockDelegate : public PlatformView::Delegate {
                              const ViewportMetrics& viewport_metrics,
                              AddViewCallback callback) override {}
   void OnPlatformViewRemoveView(int64_t view_id, RemoveViewCallback callback) override {}
+  void OnPlatformViewSendViewFocusEvent(const ViewFocusEvent& event) override {};
   void OnPlatformViewSetNextFrameCallback(const fml::closure& closure) override {}
   void OnPlatformViewSetViewportMetrics(int64_t view_id, const ViewportMetrics& metrics) override {}
   const flutter::Settings& OnPlatformViewGetSettings() const override { return settings_; }

engine/src/flutter/shell/platform/embedder/embedder.cc

@@ -2226,6 +2226,24 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
     };
   }
 
+  flutter::PlatformViewEmbedder::ViewFocusChangeRequestCallback
+      view_focus_change_request_callback = nullptr;
+  if (SAFE_ACCESS(args, view_focus_change_request_callback, nullptr) !=
+      nullptr) {
+    view_focus_change_request_callback =
+        [ptr = args->view_focus_change_request_callback,
+         user_data](const flutter::ViewFocusChangeRequest& request) {
+          FlutterViewFocusChangeRequest embedder_request{
+              .struct_size = sizeof(FlutterViewFocusChangeRequest),
+              .view_id = request.view_id(),
+              .state = static_cast<FlutterViewFocusState>(request.state()),
+              .direction =
+                  static_cast<FlutterViewFocusDirection>(request.direction()),
+          };
+          ptr(&embedder_request, user_data);
+        };
+  }
+
   auto external_view_embedder_result = InferExternalViewEmbedderFromArgs(
       SAFE_ACCESS(args, compositor, nullptr), settings.enable_impeller);
   if (external_view_embedder_result.second) {
@@ -2241,6 +2259,7 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
           compute_platform_resolved_locale_callback,  //
           on_pre_engine_restart_callback,             //
           channel_update_callback,                    //
+          view_focus_change_request_callback,         //
       };
 
   auto on_create_platform_view = InferPlatformViewCreationCallback(
@@ -2556,6 +2575,38 @@ FlutterEngineResult FlutterEngineRemoveView(FLUTTER_API_SYMBOL(FlutterEngine)
   return kSuccess;
 }
 
+FlutterEngineResult FlutterEngineSendViewFocusEvent(
+    FLUTTER_API_SYMBOL(FlutterEngine) engine,
+    const FlutterViewFocusEvent* event) {
+  if (!engine) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments, "Engine handle was invalid.");
+  }
+  if (!event) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments,
+                              "View focus event must not be null.");
+  }
+  // The engine must be running to focus a view.
+  auto embedder_engine = reinterpret_cast<flutter::EmbedderEngine*>(engine);
+  if (!embedder_engine->IsValid()) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments, "Engine handle was invalid.");
+  }
+
+  if (!STRUCT_HAS_MEMBER(event, direction)) {
+    return LOG_EMBEDDER_ERROR(kInvalidArguments,
+                              "The event struct has invalid size.");
+  }
+
+  flutter::ViewFocusEvent flutter_event(
+      event->view_id,  //
+      static_cast<flutter::ViewFocusState>(event->state),
+      static_cast<flutter::ViewFocusDirection>(event->direction));
+
+  embedder_engine->GetShell().GetPlatformView()->SendViewFocusEvent(
+      flutter_event);
+
+  return kSuccess;
+}
+
 FLUTTER_EXPORT
 FlutterEngineResult FlutterEngineDeinitialize(FLUTTER_API_SYMBOL(FlutterEngine)
                                                   engine) {
@@ -3657,6 +3708,7 @@ FlutterEngineResult FlutterEngineGetProcAddresses(
   SET_PROC(SetNextFrameCallback, FlutterEngineSetNextFrameCallback);
   SET_PROC(AddView, FlutterEngineAddView);
   SET_PROC(RemoveView, FlutterEngineRemoveView);
+  SET_PROC(SendViewFocusEvent, FlutterEngineSendViewFocusEvent);
 #undef SET_PROC
 
   return kSuccess;

engine/src/flutter/shell/platform/embedder/embedder.h

@@ -1060,6 +1060,74 @@ typedef struct {
   FlutterRemoveViewCallback remove_view_callback;
 } FlutterRemoveViewInfo;
 
+/// Represents the direction in which the focus transitioned across
+/// [FlutterView]s.
+typedef enum {
+  /// Indicates the focus transition did not have a direction.
+  ///
+  /// This is typically associated with focus being programmatically requested
+  /// or when focus is lost.
+  kUndefined,
+
+  /// Indicates the focus transition was performed in a forward direction.
+  ///
+  /// This is typically result of the user pressing tab.
+  kForward,
+
+  /// Indicates the focus transition was performed in a backward direction.
+  ///
+  /// This is typically result of the user pressing shift + tab.
+  kBackward,
+} FlutterViewFocusDirection;
+
+/// Represents the focus state of a given [FlutterView].
+typedef enum {
+  /// Specifies that a view does not have platform focus.
+  kUnfocused,
+
+  /// Specifies that a view has platform focus.
+  kFocused,
+} FlutterViewFocusState;
+
+/// A view focus event is sent to the engine by the embedder when a native view
+/// focus state has changed.
+///
+/// Passed through FlutterEngineSendViewFocusEvent.
+typedef struct {
+  /// The size of this struct.
+  /// Must be sizeof(FlutterViewFocusEvent).
+  size_t struct_size;
+
+  /// The identifier of the view that received the focus event.
+  FlutterViewId view_id;
+
+  /// The focus state of the view.
+  FlutterViewFocusState state;
+
+  /// The direction in which the focus transitioned across [FlutterView]s.
+  FlutterViewFocusDirection direction;
+} FlutterViewFocusEvent;
+
+/// A FlutterViewFocusChangeRequest is sent by the engine to the embedder when
+/// when a FlutterView focus state has changed and native view focus
+/// needs to be updated.
+///
+/// Received in FlutterProjectArgs.view_focus_change_request_callback.
+typedef struct {
+  /// The size of this struct.
+  /// Must be sizeof(FlutterViewFocusChangeRequest).
+  size_t struct_size;
+
+  /// The identifier of the view that received the focus event.
+  FlutterViewId view_id;
+
+  /// The focus state of the view.
+  FlutterViewFocusState state;
+
+  /// The direction in which the focus transitioned across [FlutterView]s.
+  FlutterViewFocusDirection direction;
+} FlutterViewFocusChangeRequest;
+
 /// The phase of the pointer event.
 typedef enum {
   kCancel,
@@ -1644,6 +1712,10 @@ typedef void (*FlutterChannelUpdateCallback)(
     const FlutterChannelUpdate* /* channel update */,
     void* /* user data */);
 
+typedef void (*FlutterViewFocusChangeRequestCallback)(
+    const FlutterViewFocusChangeRequest* /* request */,
+    void* /* user data */);
+
 typedef struct _FlutterTaskRunner* FlutterTaskRunner;
 
 typedef struct {
@@ -2553,6 +2625,12 @@ typedef struct {
   /// being registered on the framework side. The callback is invoked from
   /// a task posted to the platform thread.
   FlutterChannelUpdateCallback channel_update_callback;
+
+  /// The callback invoked by the engine when FlutterView focus state has
+  /// changed. The embedder can use this callback to request focus change for
+  /// the native view. The callback is invoked from a task posted to the
+  /// platform thread.
+  FlutterViewFocusChangeRequestCallback view_focus_change_request_callback;
 } FlutterProjectArgs;
 
 #ifndef FLUTTER_ENGINE_NO_PROTOTYPES
@@ -2757,6 +2835,16 @@ FlutterEngineResult FlutterEngineRemoveView(FLUTTER_API_SYMBOL(FlutterEngine)
                                                 engine,
                                             const FlutterRemoveViewInfo* info);
 
+//------------------------------------------------------------------------------
+/// @brief      Notifies the engine that platform view focus state has changed.
+///
+/// @param[in]  engine  A running engine instance
+/// @param[in]  event   The focus event data describing the change.
+FLUTTER_EXPORT
+FlutterEngineResult FlutterEngineSendViewFocusEvent(
+    FLUTTER_API_SYMBOL(FlutterEngine) engine,
+    const FlutterViewFocusEvent* event);
+
 FLUTTER_EXPORT
 FlutterEngineResult FlutterEngineSendWindowMetricsEvent(
     FLUTTER_API_SYMBOL(FlutterEngine) engine,
@@ -3433,6 +3521,9 @@ typedef FlutterEngineResult (*FlutterEngineAddViewFnPtr)(
 typedef FlutterEngineResult (*FlutterEngineRemoveViewFnPtr)(
     FLUTTER_API_SYMBOL(FlutterEngine) engine,
     const FlutterRemoveViewInfo* info);
+typedef FlutterEngineResult (*FlutterEngineSendViewFocusEventFnPtr)(
+    FLUTTER_API_SYMBOL(FlutterEngine) engine,
+    const FlutterViewFocusEvent* event);
 
 /// Function-pointer-based versions of the APIs above.
 typedef struct {
@@ -3481,6 +3572,7 @@ typedef struct {
   FlutterEngineSetNextFrameCallbackFnPtr SetNextFrameCallback;
   FlutterEngineAddViewFnPtr AddView;
   FlutterEngineRemoveViewFnPtr RemoveView;
+  FlutterEngineSendViewFocusEventFnPtr SendViewFocusEvent;
 } FlutterEngineProcTable;
 
 //------------------------------------------------------------------------------

engine/src/flutter/shell/platform/embedder/fixtures/main.dart

@@ -1600,3 +1600,30 @@ Future<void> render_impeller_image_snapshot_test() async {
   final bool result = (pixel & 0xFF) == color.alpha && ((pixel >> 8) & 0xFF) == color.blue;
   notifyBoolValue(result);
 }
+
+@pragma('vm:entry-point')
+void testSendViewFocusEvent() {
+  PlatformDispatcher.instance.onViewFocusChange = (ViewFocusEvent event) {
+    notifyStringValue('${event.viewId} ${event.state} ${event.direction}');
+  };
+  signalNativeTest();
+}
+
+@pragma('vm:entry-point')
+void testSendViewFocusChangeRequest() {
+  PlatformDispatcher.instance.requestViewFocusChange(
+    viewId: 1,
+    state: ViewFocusState.unfocused,
+    direction: ViewFocusDirection.undefined,
+  );
+  PlatformDispatcher.instance.requestViewFocusChange(
+    viewId: 2,
+    state: ViewFocusState.focused,
+    direction: ViewFocusDirection.forward,
+  );
+  PlatformDispatcher.instance.requestViewFocusChange(
+    viewId: 3,
+    state: ViewFocusState.focused,
+    direction: ViewFocusDirection.backward,
+  );
+}

engine/src/flutter/shell/platform/embedder/platform_view_embedder.cc

@@ -207,6 +207,13 @@ void PlatformViewEmbedder::SendChannelUpdate(const std::string& name,
   }
 }
 
+void PlatformViewEmbedder::RequestViewFocusChange(
+    const ViewFocusChangeRequest& request) {
+  if (platform_dispatch_table_.view_focus_change_request_callback != nullptr) {
+    platform_dispatch_table_.view_focus_change_request_callback(request);
+  }
+}
+
 std::shared_ptr<PlatformMessageHandler>
 PlatformViewEmbedder::GetPlatformMessageHandler() const {
   return platform_message_handler_;

engine/src/flutter/shell/platform/embedder/platform_view_embedder.h

@@ -45,6 +45,8 @@ class PlatformViewEmbedder final : public PlatformView {
           const std::vector<std::string>& supported_locale_data)>;
   using OnPreEngineRestartCallback = std::function<void()>;
   using ChanneUpdateCallback = std::function<void(const std::string&, bool)>;
+  using ViewFocusChangeRequestCallback =
+      std::function<void(const ViewFocusChangeRequest&)>;
 
   struct PlatformDispatchTable {
     UpdateSemanticsCallback update_semantics_callback;  // optional
@@ -55,6 +57,8 @@ class PlatformViewEmbedder final : public PlatformView {
         compute_platform_resolved_locale_callback;
     OnPreEngineRestartCallback on_pre_engine_restart_callback;  // optional
     ChanneUpdateCallback on_channel_update;                     // optional
+    ViewFocusChangeRequestCallback
+        view_focus_change_request_callback;  // optional
   };
 
   // Create a platform view that sets up a software rasterizer.
@@ -142,6 +146,9 @@ class PlatformViewEmbedder final : public PlatformView {
   // |PlatformView|
   void SendChannelUpdate(const std::string& name, bool listening) override;
 
+  // |PlatformView|
+  void RequestViewFocusChange(const ViewFocusChangeRequest& request) override;
+
   FML_DISALLOW_COPY_AND_ASSIGN(PlatformViewEmbedder);
 };
 

engine/src/flutter/shell/platform/embedder/platform_view_embedder_unittests.cc

@@ -32,6 +32,10 @@ class MockDelegate : public PlatformView::Delegate {
               OnPlatformViewRemoveView,
               (int64_t view_id, RemoveViewCallback callback),
               (override));
+  MOCK_METHOD(void,
+              OnPlatformViewSendViewFocusEvent,
+              (const ViewFocusEvent& event),
+              (override));
   MOCK_METHOD(void,
               OnPlatformViewSetNextFrameCallback,
               (const fml::closure& closure),

engine/src/flutter/shell/platform/embedder/tests/embedder_config_builder.cc

@@ -37,6 +37,7 @@ EmbedderConfigBuilder::EmbedderConfigBuilder(
     SetLogMessageCallbackHook();
     SetLocalizationCallbackHooks();
     SetChannelUpdateCallbackHook();
+    SetViewFocusChangeRequestHook();
     AddCommandLineArgument("--disable-vm-service");
 
     if (preference == InitializationPreference::kSnapshotsInitialize ||
@@ -112,6 +113,11 @@ void EmbedderConfigBuilder::SetChannelUpdateCallbackHook() {
       context_.GetChannelUpdateCallbackHook();
 }
 
+void EmbedderConfigBuilder::SetViewFocusChangeRequestHook() {
+  project_args_.view_focus_change_request_callback =
+      context_.GetViewFocusChangeRequestCallbackHook();
+}
+
 void EmbedderConfigBuilder::SetLogTag(std::string tag) {
   log_tag_ = std::move(tag);
   project_args_.log_tag = log_tag_.c_str();
@@ -194,6 +200,11 @@ void EmbedderConfigBuilder::SetPlatformMessageCallback(
   context_.SetPlatformMessageCallback(callback);
 }
 
+void EmbedderConfigBuilder::SetViewFocusChangeRequestCallback(
+    const std::function<void(const FlutterViewFocusChangeRequest*)>& callback) {
+  context_.SetViewFocusChangeRequestCallback(callback);
+}
+
 void EmbedderConfigBuilder::SetCompositor(bool avoid_backing_store_cache,
                                           bool use_present_layers_callback) {
   context_.SetupCompositor();

engine/src/flutter/shell/platform/embedder/tests/embedder_config_builder.h

@@ -59,6 +59,8 @@ class EmbedderConfigBuilder {
 
   void SetChannelUpdateCallbackHook();
 
+  void SetViewFocusChangeRequestHook();
+
   // Used to set a custom log tag.
   void SetLogTag(std::string tag);
 
@@ -81,6 +83,10 @@ class EmbedderConfigBuilder {
   void SetPlatformMessageCallback(
       const std::function<void(const FlutterPlatformMessage*)>& callback);
 
+  void SetViewFocusChangeRequestCallback(
+      const std::function<void(const FlutterViewFocusChangeRequest*)>&
+          callback);
+
   void SetCompositor(bool avoid_backing_store_cache = false,
                      bool use_present_layers_callback = false);
 
@@ -101,6 +107,9 @@ class EmbedderConfigBuilder {
   // text context vis `SetVsyncCallback`.
   void SetupVsyncCallback();
 
+  void SetViewFocusChangeRequestCallback(
+      const FlutterViewFocusChangeRequestCallback& callback);
+
  private:
   EmbedderTestContext& context_;
   FlutterProjectArgs project_args_ = {};

engine/src/flutter/shell/platform/embedder/tests/embedder_test_context.cc

@@ -156,6 +156,11 @@ void EmbedderTestContext::SetChannelUpdateCallback(
   channel_update_callback_ = callback;
 }
 
+void EmbedderTestContext::SetViewFocusChangeRequestCallback(
+    const ViewFocusChangeRequestCallback& callback) {
+  view_focus_change_request_callback_ = callback;
+}
+
 void EmbedderTestContext::PlatformMessageCallback(
     const FlutterPlatformMessage* message) {
   if (platform_message_callback_) {
@@ -255,6 +260,16 @@ EmbedderTestContext::GetChannelUpdateCallbackHook() {
   };
 }
 
+FlutterViewFocusChangeRequestCallback
+EmbedderTestContext::GetViewFocusChangeRequestCallbackHook() {
+  return [](const FlutterViewFocusChangeRequest* request, void* user_data) {
+    auto context = reinterpret_cast<EmbedderTestContext*>(user_data);
+    if (context->view_focus_change_request_callback_) {
+      context->view_focus_change_request_callback_(request);
+    }
+  };
+}
+
 FlutterTransformation EmbedderTestContext::GetRootSurfaceTransformation() {
   return FlutterTransformationMake(root_surface_transformation_);
 }

engine/src/flutter/shell/platform/embedder/tests/embedder_test_context.h

@@ -34,6 +34,8 @@ using SemanticsActionCallback =
 using LogMessageCallback =
     std::function<void(const char* tag, const char* message)>;
 using ChannelUpdateCallback = std::function<void(const FlutterChannelUpdate*)>;
+using ViewFocusChangeRequestCallback =
+    std::function<void(const FlutterViewFocusChangeRequest*)>;
 
 struct AOTDataDeleter {
   void operator()(FlutterEngineAOTData aot_data) {
@@ -94,6 +96,9 @@ class EmbedderTestContext {
 
   void SetChannelUpdateCallback(const ChannelUpdateCallback& callback);
 
+  void SetViewFocusChangeRequestCallback(
+      const ViewFocusChangeRequestCallback& callback);
+
   std::future<sk_sp<SkImage>> GetNextSceneImage();
 
   EmbedderTestCompositor& GetCompositor();
@@ -133,6 +138,7 @@ class EmbedderTestContext {
   SemanticsNodeCallback update_semantics_node_callback_;
   SemanticsActionCallback update_semantics_custom_action_callback_;
   ChannelUpdateCallback channel_update_callback_;
+  ViewFocusChangeRequestCallback view_focus_change_request_callback_;
   std::function<void(const FlutterPlatformMessage*)> platform_message_callback_;
   LogMessageCallback log_message_callback_;
   std::unique_ptr<EmbedderTestCompositor> compositor_;
@@ -158,6 +164,8 @@ class EmbedderTestContext {
 
   FlutterChannelUpdateCallback GetChannelUpdateCallbackHook();
 
+  FlutterViewFocusChangeRequestCallback GetViewFocusChangeRequestCallbackHook();
+
   void SetupAOTMappingsIfNecessary();
 
   void SetupAOTDataIfNecessary();

engine/src/flutter/shell/platform/embedder/tests/embedder_unittests.cc

@@ -2045,6 +2045,124 @@ TEST_F(EmbedderTest, CanRenderMultipleViews) {
   latch123.Wait();
 }
 
+bool operator==(const FlutterViewFocusChangeRequest& lhs,
+                const FlutterViewFocusChangeRequest& rhs) {
+  return lhs.view_id == rhs.view_id && lhs.state == rhs.state &&
+         lhs.direction == rhs.direction;
+}
+
+TEST_F(EmbedderTest, SendsViewFocusChangeRequest) {
+  auto& context = GetEmbedderContext<EmbedderTestContextSoftware>();
+  auto platform_task_runner = CreateNewThread("test_platform_thread");
+  UniqueEngine engine;
+  static std::mutex engine_mutex;
+  EmbedderTestTaskRunner test_platform_task_runner(
+      platform_task_runner, [&](FlutterTask task) {
+        std::scoped_lock lock(engine_mutex);
+        if (!engine.is_valid()) {
+          return;
+        }
+        FlutterEngineRunTask(engine.get(), &task);
+      });
+  fml::CountDownLatch latch(3);
+  std::vector<FlutterViewFocusChangeRequest> received_requests;
+  platform_task_runner->PostTask([&]() {
+    EmbedderConfigBuilder builder(context);
+    builder.SetSurface(SkISize::Make(1, 1));
+    builder.SetDartEntrypoint("testSendViewFocusChangeRequest");
+    const auto platform_task_runner_description =
+        test_platform_task_runner.GetFlutterTaskRunnerDescription();
+    builder.SetPlatformTaskRunner(&platform_task_runner_description);
+    builder.SetViewFocusChangeRequestCallback(
+        [&](const FlutterViewFocusChangeRequest* request) {
+          EXPECT_TRUE(platform_task_runner->RunsTasksOnCurrentThread());
+          received_requests.push_back(*request);
+          latch.CountDown();
+        });
+    engine = builder.LaunchEngine();
+    ASSERT_TRUE(engine.is_valid());
+  });
+  latch.Wait();
+
+  std::vector<FlutterViewFocusChangeRequest> expected_requests{
+      {.view_id = 1, .state = kUnfocused, .direction = kUndefined},
+      {.view_id = 2, .state = kFocused, .direction = kForward},
+      {.view_id = 3, .state = kFocused, .direction = kBackward},
+  };
+
+  ASSERT_EQ(received_requests.size(), expected_requests.size());
+  for (size_t i = 0; i < received_requests.size(); ++i) {
+    ASSERT_TRUE(received_requests[i] == expected_requests[i]);
+  }
+
+  fml::AutoResetWaitableEvent kill_latch;
+  platform_task_runner->PostTask(fml::MakeCopyable([&]() mutable {
+    std::scoped_lock lock(engine_mutex);
+    engine.reset();
+
+    // There may still be pending tasks on the platform thread that were queued
+    // by the test_task_runner.  Signal the latch after these tasks have been
+    // consumed.
+    platform_task_runner->PostTask([&kill_latch] { kill_latch.Signal(); });
+  }));
+  kill_latch.Wait();
+}
+
+TEST_F(EmbedderTest, CanSendViewFocusEvent) {
+  auto& context = GetEmbedderContext<EmbedderTestContextSoftware>();
+  EmbedderConfigBuilder builder(context);
+  builder.SetSurface(SkISize::Make(1, 1));
+  builder.SetDartEntrypoint("testSendViewFocusEvent");
+
+  fml::AutoResetWaitableEvent latch;
+  std::string last_event;
+
+  context.AddNativeCallback(
+      "SignalNativeTest",
+      CREATE_NATIVE_ENTRY(
+          [&latch](Dart_NativeArguments args) { latch.Signal(); }));
+  context.AddNativeCallback("NotifyStringValue",
+                            CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
+                              const auto message_from_dart =
+                                  tonic::DartConverter<std::string>::FromDart(
+                                      Dart_GetNativeArgument(args, 0));
+                              last_event = message_from_dart;
+                              latch.Signal();
+                            }));
+
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+  // Wait until the focus change handler is attached.
+  latch.Wait();
+  latch.Reset();
+
+  FlutterViewFocusEvent event1{
+      .struct_size = sizeof(FlutterViewFocusEvent),
+      .view_id = 1,
+      .state = kFocused,
+      .direction = kUndefined,
+  };
+  FlutterEngineResult result =
+      FlutterEngineSendViewFocusEvent(engine.get(), &event1);
+  ASSERT_EQ(result, kSuccess);
+  latch.Wait();
+  ASSERT_EQ(last_event,
+            "1 ViewFocusState.focused ViewFocusDirection.undefined");
+
+  FlutterViewFocusEvent event2{
+      .struct_size = sizeof(FlutterViewFocusEvent),
+      .view_id = 2,
+      .state = kUnfocused,
+      .direction = kBackward,
+  };
+  latch.Reset();
+  result = FlutterEngineSendViewFocusEvent(engine.get(), &event2);
+  ASSERT_EQ(result, kSuccess);
+  latch.Wait();
+  ASSERT_EQ(last_event,
+            "2 ViewFocusState.unfocused ViewFocusDirection.backward");
+}
+
 //------------------------------------------------------------------------------
 /// Test that the backing store is created with the correct view ID, is used
 /// for the correct view, and is cached according to their views.

engine/src/flutter/shell/platform/fuchsia/flutter/tests/platform_view_unittest.cc

@@ -157,6 +157,9 @@ class MockPlatformViewDelegate : public flutter::PlatformView::Delegate {
   void UpdateAssetResolverByType(
       std::unique_ptr<flutter::AssetResolver> updated_asset_resolver,
       flutter::AssetResolver::AssetResolverType type) {}
+  // |flutter::PlatformView::Delegate|
+  void OnPlatformViewSendViewFocusEvent(const flutter::ViewFocusEvent& event) {
+  };
 
   flutter::Surface* surface() const { return surface_.get(); }
   flutter::PlatformMessage* message() const { return message_.get(); }