From 500e60cb1bc9fe690657b5f82f9df32c1d278bda Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Thu, 8 Feb 2024 14:20:43 -0500
Subject: [PATCH 01/27] Define structs, class

---
 shell/platform/windows/BUILD.gn               |  2 ++
 .../platform/windows/platform_view_manager.cc |  9 ++++++
 .../platform/windows/platform_view_manager.h  | 31 +++++++++++++++++++
 .../platform/windows/public/flutter_windows.h | 15 +++++++++
 4 files changed, 57 insertions(+)
 create mode 100644 shell/platform/windows/platform_view_manager.cc
 create mode 100644 shell/platform/windows/platform_view_manager.h

diff --git a/shell/platform/windows/BUILD.gn b/shell/platform/windows/BUILD.gn
index 7a30f737b69b6..f8dad4bb1f777 100644
--- a/shell/platform/windows/BUILD.gn
+++ b/shell/platform/windows/BUILD.gn
@@ -98,6 +98,8 @@ source_set("flutter_windows_source") {
     "keyboard_utils.h",
     "platform_handler.cc",
     "platform_handler.h",
+    "platform_view_manager.cc",
+    "platform_view_manager.h",
     "sequential_id_generator.cc",
     "sequential_id_generator.h",
     "settings_plugin.cc",
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
new file mode 100644
index 0000000000000..b5fff47fd340a
--- /dev/null
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -0,0 +1,9 @@
+// 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/shell/platform/windows/platform_view_manager.h"
+
+namespace flutter {
+
+}  // namespace flutter
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
new file mode 100644
index 0000000000000..c36568765b5b7
--- /dev/null
+++ b/shell/platform/windows/platform_view_manager.h
@@ -0,0 +1,31 @@
+// 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_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
+
+#include <map>
+#include <memory>
+
+#include "flutter/shell/platform/common/client_wrapper/include/flutter/method_channel.h"
+#include "flutter/shell/platform/windows/public/flutter_windows.h"
+
+namespace flutter {
+
+class PlatformViewManager {
+ public:
+
+ private:
+  std::unique_ptr<MethodChannel<EncodableValue>> channel_;
+
+  std::map<std::string, FlutterPlatformViewTypeEntry> platform_view_types_;
+
+  std::map<int64_t, HWND> platform_views_;
+
+  std::map<int64_t, FlutterPlatformViewCreationParameters> pending_platform_views_;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index 70cd60a2eb984..f3a400d61229d 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -203,6 +203,21 @@ FLUTTER_EXPORT void FlutterDesktopEngineSetNextFrameCallback(
     VoidCallback callback,
     void* user_data);
 
+typedef struct {
+  size_t cb_size;
+  HWND parent_window;
+  const char* platform_view_type;
+  void* user_data;
+  int64_t platform_view_id;
+} FlutterPlatformViewCreationParameters;
+
+typedef HWND (*FlutterPlatformViewFactory)(const FlutterPlatformViewCreationParameters*);
+
+typedef struct {
+  FlutterPlatformViewFactory factory;
+  void* user_data;
+} FlutterPlatformViewTypeEntry;
+
 // ========== View ==========
 
 // Return backing HWND for manipulation in host application.

From 8dd45432fe3c314a4d5a9227a7a065dd346197e0 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Thu, 8 Feb 2024 14:27:49 -0500
Subject: [PATCH 02/27] Define PV type registration runner API function

---
 .../client_wrapper/testing/stub_flutter_windows_api.cc | 10 ++++++++++
 .../client_wrapper/testing/stub_flutter_windows_api.h  |  4 ++++
 shell/platform/windows/flutter_windows.cc              |  7 +++++++
 shell/platform/windows/public/flutter_windows.h        |  5 +++++
 4 files changed, 26 insertions(+)

diff --git a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.cc b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.cc
index da0a8c57712d3..f01f895c728f5 100644
--- a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.cc
+++ b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.cc
@@ -176,6 +176,16 @@ bool FlutterDesktopEngineProcessExternalWindowMessage(
   return false;
 }
 
+void FlutterDesktopEngineRegisterPlatformViewType(
+    FlutterDesktopEngineRef engine,
+    const char* view_type_name,
+    FlutterPlatformViewTypeEntry view_type) {
+  if (s_stub_implementation) {
+    s_stub_implementation->EngineRegisterPlatformViewType(view_type_name,
+                                                          view_type);
+  }
+}
+
 FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
     FlutterDesktopPluginRegistrarRef controller) {
   // The stub ignores this, so just return an arbitrary non-zero value.
diff --git a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
index 19671159ea426..c9b44199f4053 100644
--- a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
+++ b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
@@ -72,6 +72,10 @@ class StubFlutterWindowsApi {
   // Called for FlutterDesktopEngineReloadSystemFonts.
   virtual void EngineReloadSystemFonts() {}
 
+  // Called for FlutterDesktopEngineRegisterPlatformViewType.
+  virtual void EngineRegisterPlatformViewType(
+      const char* view_type_name, FlutterPlatformViewTypeEntry view_type) {}
+
   // Called for FlutterDesktopViewGetHWND.
   virtual HWND ViewGetHWND() { return reinterpret_cast<HWND>(1); }
 
diff --git a/shell/platform/windows/flutter_windows.cc b/shell/platform/windows/flutter_windows.cc
index 0f293c497c670..dc1eeb73d80ec 100644
--- a/shell/platform/windows/flutter_windows.cc
+++ b/shell/platform/windows/flutter_windows.cc
@@ -246,6 +246,13 @@ bool FlutterDesktopEngineProcessExternalWindowMessage(
   return lresult.has_value();
 }
 
+void FlutterDesktopEngineRegisterPlatformViewType(
+    FlutterDesktopEngineRef engine,
+    const char* view_type_name,
+    FlutterPlatformViewTypeEntry view_type) {
+  // TODO(schectman): forward to platform view manager
+}
+
 FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
     FlutterDesktopPluginRegistrarRef registrar) {
   return HandleForView(registrar->engine->view());
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index f3a400d61229d..11fff8fbeb7ce 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -218,6 +218,11 @@ typedef struct {
   void* user_data;
 } FlutterPlatformViewTypeEntry;
 
+FLUTTER_EXPORT void FlutterDesktopEngineRegisterPlatformViewType(
+    FlutterDesktopEngineRef engine,
+    const char* view_type_name,
+    FlutterPlatformViewTypeEntry view_type);
+
 // ========== View ==========
 
 // Return backing HWND for manipulation in host application.

From ae0d0492664da3026e74a853f3087bf5420a2c5a Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Thu, 8 Feb 2024 17:30:40 -0500
Subject: [PATCH 03/27] Bare minimum PlatformViewHandler

---
 .../platform/windows/platform_view_manager.cc | 24 +++++++++++++++++++
 .../platform/windows/platform_view_manager.h  | 23 +++++++++++++++++-
 .../platform/windows/public/flutter_windows.h |  1 +
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index b5fff47fd340a..92081210d26d1 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -4,6 +4,30 @@
 
 #include "flutter/shell/platform/windows/platform_view_manager.h"
 
+#include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_method_codec.h"
+
 namespace flutter {
 
+namespace {
+constexpr char kChannelName[] = "";
+}
+
+PlatformViewManager::PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger) : task_runner_(task_runner), channel_(std::make_unique<MethodChannel<EncodableValue>>(binary_messenger, kChannelName, &StandardMethodCodec::GetInstance())) {
+  channel_->SetMethodCallHandler([](const MethodCall<EncodableValue>& call, std::unique_ptr<MethodResult<EncodableValue>> result){
+    result->Success();
+  });
+}
+
+void PlatformViewManager::QueuePlatformViewCreation(std::string_view type_name, int64_t id) {}
+
+void PlatformViewManager::InstantiatePlatformView(int64_t id) {}
+
+void PlatformViewManager::RegisterPlatformViewType(std::string_view type_name, const FlutterPlatformViewTypeEntry& type) {}
+
+void PlatformViewManager::FocusPlatformView(int64_t id, FocusChangeDirection direction, bool focus) {}
+
+std::optional<HWND> PlatformViewManager::GetNativeHandleForId(int64_t id) const {
+  return std::nullopt;
+}
+
 }  // namespace flutter
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index c36568765b5b7..60d9d870a73f8 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -5,17 +5,36 @@
 #ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
 #define FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
 
+#include <functional>
 #include <map>
 #include <memory>
+#include <optional>
 
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/method_channel.h"
 #include "flutter/shell/platform/windows/public/flutter_windows.h"
+#include "flutter/shell/platform/windows/task_runner.h"
 
 namespace flutter {
 
+enum class FocusChangeDirection {
+  kProgrammatic,
+  kForward,
+  kBackward
+};
+
 class PlatformViewManager {
  public:
+  PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger);
+
+  void QueuePlatformViewCreation(std::string_view type_name, int64_t id);
+
+  void InstantiatePlatformView(int64_t id);
 
+  void RegisterPlatformViewType(std::string_view type_name, const FlutterPlatformViewTypeEntry& type);
+
+  void FocusPlatformView(int64_t id, FocusChangeDirection direction, bool focus);
+
+  std::optional<HWND> GetNativeHandleForId(int64_t id) const;
  private:
   std::unique_ptr<MethodChannel<EncodableValue>> channel_;
 
@@ -23,7 +42,9 @@ class PlatformViewManager {
 
   std::map<int64_t, HWND> platform_views_;
 
-  std::map<int64_t, FlutterPlatformViewCreationParameters> pending_platform_views_;
+  std::map<int64_t, std::function<HWND()>> pending_platform_views_;
+
+  TaskRunner* task_runner_;
 };
 
 }  // namespace flutter
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index 11fff8fbeb7ce..4d92d07d7f793 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -214,6 +214,7 @@ typedef struct {
 typedef HWND (*FlutterPlatformViewFactory)(const FlutterPlatformViewCreationParameters*);
 
 typedef struct {
+  size_t cb_size;
   FlutterPlatformViewFactory factory;
   void* user_data;
 } FlutterPlatformViewTypeEntry;

From 5f14af0e02f4250bdce68e68552f8858790ac12f Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Thu, 8 Feb 2024 17:38:08 -0500
Subject: [PATCH 04/27] Compositor owns platform view manager

---
 shell/platform/windows/compositor.h                  |  8 ++++++++
 shell/platform/windows/compositor_opengl.cc          |  5 +++--
 shell/platform/windows/compositor_opengl.h           |  3 ++-
 .../platform/windows/compositor_opengl_unittests.cc  | 12 ++++++------
 shell/platform/windows/compositor_software.cc        |  5 +++--
 shell/platform/windows/compositor_software.h         |  3 ++-
 .../windows/compositor_software_unittests.cc         |  8 ++++----
 shell/platform/windows/flutter_windows_engine.cc     |  5 +++--
 8 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/shell/platform/windows/compositor.h b/shell/platform/windows/compositor.h
index c7691f53e8510..e94e08f4a6c3d 100644
--- a/shell/platform/windows/compositor.h
+++ b/shell/platform/windows/compositor.h
@@ -7,6 +7,10 @@
 
 #include "flutter/shell/platform/embedder/embedder.h"
 
+#include <memory>
+
+#include "flutter/shell/platform/windows/platform_view_manager.h"
+
 namespace flutter {
 
 // Enables the Flutter engine to render content on Windows.
@@ -19,6 +23,7 @@ namespace flutter {
 // Platform views are not yet supported.
 class Compositor {
  public:
+  Compositor(std::unique_ptr<PlatformViewManager> manager) : platform_view_manager_(std::move(manager)) {}
   virtual ~Compositor() = default;
 
   // Creates a backing store used for rendering Flutter content.
@@ -32,6 +37,9 @@ class Compositor {
 
   // Present Flutter content and platform views onto the view.
   virtual bool Present(const FlutterLayer** layers, size_t layers_count) = 0;
+
+ protected:
+  std::unique_ptr<PlatformViewManager> platform_view_manager_;
 };
 
 }  // namespace flutter
diff --git a/shell/platform/windows/compositor_opengl.cc b/shell/platform/windows/compositor_opengl.cc
index b43f888d65191..5c3d6b0c85add 100644
--- a/shell/platform/windows/compositor_opengl.cc
+++ b/shell/platform/windows/compositor_opengl.cc
@@ -34,9 +34,10 @@ int GetSupportedTextureFormat(const impeller::DescriptionGLES* description) {
 
 }  // namespace
 
-CompositorOpenGL::CompositorOpenGL(FlutterWindowsEngine* engine,
+CompositorOpenGL::CompositorOpenGL(std::unique_ptr<PlatformViewManager> manager,
+                                   FlutterWindowsEngine* engine,
                                    impeller::ProcTableGLES::Resolver resolver)
-    : engine_(engine), resolver_(resolver) {}
+    : Compositor(std::move(manager)), engine_(engine), resolver_(resolver) {}
 
 bool CompositorOpenGL::CreateBackingStore(
     const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_opengl.h b/shell/platform/windows/compositor_opengl.h
index 06c22202332e2..4c936c6e7d9d2 100644
--- a/shell/platform/windows/compositor_opengl.h
+++ b/shell/platform/windows/compositor_opengl.h
@@ -17,7 +17,8 @@ namespace flutter {
 // Enables the Flutter engine to render content on Windows using OpenGL.
 class CompositorOpenGL : public Compositor {
  public:
-  CompositorOpenGL(FlutterWindowsEngine* engine,
+  CompositorOpenGL(std::unique_ptr<PlatformViewManager> manager,
+                   FlutterWindowsEngine* engine,
                    impeller::ProcTableGLES::Resolver resolver);
 
   /// |Compositor|
diff --git a/shell/platform/windows/compositor_opengl_unittests.cc b/shell/platform/windows/compositor_opengl_unittests.cc
index 08fd6dfaf4861..659165e4a2f6a 100644
--- a/shell/platform/windows/compositor_opengl_unittests.cc
+++ b/shell/platform/windows/compositor_opengl_unittests.cc
@@ -113,7 +113,7 @@ class CompositorOpenGLTest : public WindowsTest {
 TEST_F(CompositorOpenGLTest, CreateBackingStore) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorOpenGL{engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -127,7 +127,7 @@ TEST_F(CompositorOpenGLTest, CreateBackingStore) {
 TEST_F(CompositorOpenGLTest, InitializationFailure) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorOpenGL{engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -140,7 +140,7 @@ TEST_F(CompositorOpenGLTest, InitializationFailure) {
 TEST_F(CompositorOpenGLTest, Present) {
   UseEngineWithView();
 
-  auto compositor = CompositorOpenGL{engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -164,7 +164,7 @@ TEST_F(CompositorOpenGLTest, Present) {
 TEST_F(CompositorOpenGLTest, PresentEmpty) {
   UseEngineWithView();
 
-  auto compositor = CompositorOpenGL{engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
 
   // The context will be bound twice: first to initialize the compositor, second
   // to clear the surface.
@@ -177,7 +177,7 @@ TEST_F(CompositorOpenGLTest, PresentEmpty) {
 TEST_F(CompositorOpenGLTest, HeadlessPresentIgnored) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorOpenGL{engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -199,7 +199,7 @@ TEST_F(CompositorOpenGLTest, HeadlessPresentIgnored) {
 TEST_F(CompositorOpenGLTest, NoSurfaceIgnored) {
   UseEngineWithView(/*add_surface = */ false);
 
-  auto compositor = CompositorOpenGL{engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
diff --git a/shell/platform/windows/compositor_software.cc b/shell/platform/windows/compositor_software.cc
index 6f6353cbe269c..30da2a640fc23 100644
--- a/shell/platform/windows/compositor_software.cc
+++ b/shell/platform/windows/compositor_software.cc
@@ -8,8 +8,9 @@
 
 namespace flutter {
 
-CompositorSoftware::CompositorSoftware(FlutterWindowsEngine* engine)
-    : engine_(engine) {}
+CompositorSoftware::CompositorSoftware(std::unique_ptr<PlatformViewManager> manager,
+                                       FlutterWindowsEngine* engine)
+    : Compositor(std::move(manager)), engine_(engine) {}
 
 bool CompositorSoftware::CreateBackingStore(
     const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_software.h b/shell/platform/windows/compositor_software.h
index c4e39111b3c1f..ae33242f636db 100644
--- a/shell/platform/windows/compositor_software.h
+++ b/shell/platform/windows/compositor_software.h
@@ -15,7 +15,8 @@ namespace flutter {
 // rasterization and bitmaps.
 class CompositorSoftware : public Compositor {
  public:
-  CompositorSoftware(FlutterWindowsEngine* engine);
+  CompositorSoftware(std::unique_ptr<PlatformViewManager> manager,
+                     FlutterWindowsEngine* engine);
 
   /// |Compositor|
   bool CreateBackingStore(const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_software_unittests.cc b/shell/platform/windows/compositor_software_unittests.cc
index bef9fca3061b7..bb7b30889d637 100644
--- a/shell/platform/windows/compositor_software_unittests.cc
+++ b/shell/platform/windows/compositor_software_unittests.cc
@@ -76,7 +76,7 @@ class CompositorSoftwareTest : public WindowsTest {
 TEST_F(CompositorSoftwareTest, CreateBackingStore) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorSoftware{engine()};
+  auto compositor = CompositorSoftware{nullptr, engine()};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -88,7 +88,7 @@ TEST_F(CompositorSoftwareTest, CreateBackingStore) {
 TEST_F(CompositorSoftwareTest, Present) {
   UseEngineWithView();
 
-  auto compositor = CompositorSoftware{engine()};
+  auto compositor = CompositorSoftware{nullptr, engine()};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -109,7 +109,7 @@ TEST_F(CompositorSoftwareTest, Present) {
 TEST_F(CompositorSoftwareTest, PresentEmpty) {
   UseEngineWithView();
 
-  auto compositor = CompositorSoftware{engine()};
+  auto compositor = CompositorSoftware{nullptr, engine()};
 
   EXPECT_CALL(*view(), ClearSoftwareBitmap).WillOnce(Return(true));
   EXPECT_TRUE(compositor.Present(nullptr, 0));
@@ -118,7 +118,7 @@ TEST_F(CompositorSoftwareTest, PresentEmpty) {
 TEST_F(CompositorSoftwareTest, HeadlessPresentIgnored) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorSoftware{engine()};
+  auto compositor = CompositorSoftware{nullptr, engine()};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index a5766c16577cd..b0d8875b89d92 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -380,14 +380,15 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
 
   args.custom_task_runners = &custom_task_runners;
 
+  auto platform_view_manager = std::make_unique<PlatformViewManager>(task_runner_.get(), messenger_wrapper_.get());
   if (egl_manager_) {
     auto resolver = [](const char* name) -> void* {
       return reinterpret_cast<void*>(::eglGetProcAddress(name));
     };
 
-    compositor_ = std::make_unique<CompositorOpenGL>(this, resolver);
+    compositor_ = std::make_unique<CompositorOpenGL>(std::move(platform_view_manager), this, resolver);
   } else {
-    compositor_ = std::make_unique<CompositorSoftware>(this);
+    compositor_ = std::make_unique<CompositorSoftware>(std::move(platform_view_manager), this);
   }
 
   FlutterCompositor compositor = {};

From 200f13a8ba3809ea5adaa865d16a35f114764cf1 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Thu, 8 Feb 2024 17:56:08 -0500
Subject: [PATCH 05/27] Set up for mocking

---
 shell/platform/windows/BUILD.gn               |  1 +
 shell/platform/windows/compositor.h           |  6 ++---
 shell/platform/windows/compositor_opengl.cc   |  4 ++--
 shell/platform/windows/compositor_opengl.h    |  2 +-
 shell/platform/windows/compositor_software.cc |  4 ++--
 shell/platform/windows/compositor_software.h  |  2 +-
 .../windows/flutter_windows_engine.cc         |  8 ++++---
 .../platform/windows/flutter_windows_engine.h |  4 ++++
 .../platform/windows/platform_view_manager.h  |  2 +-
 .../windows/testing/engine_modifier.h         |  4 ++++
 .../testing/mock_platform_view_manager.h      | 24 +++++++++++++++++++
 11 files changed, 47 insertions(+), 14 deletions(-)
 create mode 100644 shell/platform/windows/testing/mock_platform_view_manager.h

diff --git a/shell/platform/windows/BUILD.gn b/shell/platform/windows/BUILD.gn
index f8dad4bb1f777..b6953b393c29d 100644
--- a/shell/platform/windows/BUILD.gn
+++ b/shell/platform/windows/BUILD.gn
@@ -222,6 +222,7 @@ executable("flutter_windows_unittests") {
     "testing/flutter_windows_engine_builder.cc",
     "testing/flutter_windows_engine_builder.h",
     "testing/mock_direct_manipulation.h",
+    "testing/mock_platform_view_manager.h",
     "testing/mock_text_input_manager.cc",
     "testing/mock_text_input_manager.h",
     "testing/mock_window.cc",
diff --git a/shell/platform/windows/compositor.h b/shell/platform/windows/compositor.h
index e94e08f4a6c3d..7ecd7dc78e4b2 100644
--- a/shell/platform/windows/compositor.h
+++ b/shell/platform/windows/compositor.h
@@ -7,8 +7,6 @@
 
 #include "flutter/shell/platform/embedder/embedder.h"
 
-#include <memory>
-
 #include "flutter/shell/platform/windows/platform_view_manager.h"
 
 namespace flutter {
@@ -23,7 +21,7 @@ namespace flutter {
 // Platform views are not yet supported.
 class Compositor {
  public:
-  Compositor(std::unique_ptr<PlatformViewManager> manager) : platform_view_manager_(std::move(manager)) {}
+  Compositor(PlatformViewManager* manager) : platform_view_manager_(manager) {}
   virtual ~Compositor() = default;
 
   // Creates a backing store used for rendering Flutter content.
@@ -39,7 +37,7 @@ class Compositor {
   virtual bool Present(const FlutterLayer** layers, size_t layers_count) = 0;
 
  protected:
-  std::unique_ptr<PlatformViewManager> platform_view_manager_;
+  PlatformViewManager* platform_view_manager_;
 };
 
 }  // namespace flutter
diff --git a/shell/platform/windows/compositor_opengl.cc b/shell/platform/windows/compositor_opengl.cc
index 5c3d6b0c85add..d21df04062115 100644
--- a/shell/platform/windows/compositor_opengl.cc
+++ b/shell/platform/windows/compositor_opengl.cc
@@ -34,10 +34,10 @@ int GetSupportedTextureFormat(const impeller::DescriptionGLES* description) {
 
 }  // namespace
 
-CompositorOpenGL::CompositorOpenGL(std::unique_ptr<PlatformViewManager> manager,
+CompositorOpenGL::CompositorOpenGL(PlatformViewManager* manager,
                                    FlutterWindowsEngine* engine,
                                    impeller::ProcTableGLES::Resolver resolver)
-    : Compositor(std::move(manager)), engine_(engine), resolver_(resolver) {}
+    : Compositor(manager), engine_(engine), resolver_(resolver) {}
 
 bool CompositorOpenGL::CreateBackingStore(
     const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_opengl.h b/shell/platform/windows/compositor_opengl.h
index 4c936c6e7d9d2..f956199b47811 100644
--- a/shell/platform/windows/compositor_opengl.h
+++ b/shell/platform/windows/compositor_opengl.h
@@ -17,7 +17,7 @@ namespace flutter {
 // Enables the Flutter engine to render content on Windows using OpenGL.
 class CompositorOpenGL : public Compositor {
  public:
-  CompositorOpenGL(std::unique_ptr<PlatformViewManager> manager,
+  CompositorOpenGL(PlatformViewManager* manager,
                    FlutterWindowsEngine* engine,
                    impeller::ProcTableGLES::Resolver resolver);
 
diff --git a/shell/platform/windows/compositor_software.cc b/shell/platform/windows/compositor_software.cc
index 30da2a640fc23..e7e0e5655e89d 100644
--- a/shell/platform/windows/compositor_software.cc
+++ b/shell/platform/windows/compositor_software.cc
@@ -8,9 +8,9 @@
 
 namespace flutter {
 
-CompositorSoftware::CompositorSoftware(std::unique_ptr<PlatformViewManager> manager,
+CompositorSoftware::CompositorSoftware(PlatformViewManager* manager,
                                        FlutterWindowsEngine* engine)
-    : Compositor(std::move(manager)), engine_(engine) {}
+    : Compositor(manager), engine_(engine) {}
 
 bool CompositorSoftware::CreateBackingStore(
     const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_software.h b/shell/platform/windows/compositor_software.h
index ae33242f636db..49c82a002ffa3 100644
--- a/shell/platform/windows/compositor_software.h
+++ b/shell/platform/windows/compositor_software.h
@@ -15,7 +15,7 @@ namespace flutter {
 // rasterization and bitmaps.
 class CompositorSoftware : public Compositor {
  public:
-  CompositorSoftware(std::unique_ptr<PlatformViewManager> manager,
+  CompositorSoftware(PlatformViewManager* manager,
                      FlutterWindowsEngine* engine);
 
   /// |Compositor|
diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index b0d8875b89d92..784e220ea31aa 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -380,15 +380,17 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
 
   args.custom_task_runners = &custom_task_runners;
 
-  auto platform_view_manager = std::make_unique<PlatformViewManager>(task_runner_.get(), messenger_wrapper_.get());
+  if (!platform_view_manager_) {
+    platform_view_manager_ = std::make_unique<PlatformViewManager>(task_runner_.get(), messenger_wrapper_.get());
+  }
   if (egl_manager_) {
     auto resolver = [](const char* name) -> void* {
       return reinterpret_cast<void*>(::eglGetProcAddress(name));
     };
 
-    compositor_ = std::make_unique<CompositorOpenGL>(std::move(platform_view_manager), this, resolver);
+    compositor_ = std::make_unique<CompositorOpenGL>(platform_view_manager_.get(), this, resolver);
   } else {
-    compositor_ = std::make_unique<CompositorSoftware>(std::move(platform_view_manager), this);
+    compositor_ = std::make_unique<CompositorSoftware>(platform_view_manager_.get(), this);
   }
 
   FlutterCompositor compositor = {};
diff --git a/shell/platform/windows/flutter_windows_engine.h b/shell/platform/windows/flutter_windows_engine.h
index 3914978f9fc1d..d564c1e4a102c 100644
--- a/shell/platform/windows/flutter_windows_engine.h
+++ b/shell/platform/windows/flutter_windows_engine.h
@@ -137,6 +137,8 @@ class FlutterWindowsEngine {
 
   TaskRunner* task_runner() { return task_runner_.get(); }
 
+  BinaryMessenger* messenger_wrapper() { return messenger_wrapper_.get(); }
+
   FlutterWindowsTextureRegistrar* texture_registrar() {
     return texture_registrar_.get();
   }
@@ -427,6 +429,8 @@ class FlutterWindowsEngine {
 
   std::shared_ptr<egl::ProcTable> gl_;
 
+  std::unique_ptr<PlatformViewManager> platform_view_manager_;
+
   FML_DISALLOW_COPY_AND_ASSIGN(FlutterWindowsEngine);
 };
 
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 60d9d870a73f8..e0339fbbcc83e 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -26,7 +26,7 @@ class PlatformViewManager {
  public:
   PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger);
 
-  void QueuePlatformViewCreation(std::string_view type_name, int64_t id);
+  virtual void QueuePlatformViewCreation(std::string_view type_name, int64_t id);
 
   void InstantiatePlatformView(int64_t id);
 
diff --git a/shell/platform/windows/testing/engine_modifier.h b/shell/platform/windows/testing/engine_modifier.h
index e9fd3b8833ec6..2e61ef78e53fe 100644
--- a/shell/platform/windows/testing/engine_modifier.h
+++ b/shell/platform/windows/testing/engine_modifier.h
@@ -68,6 +68,10 @@ class EngineModifier {
     engine_->lifecycle_manager_ = std::move(handler);
   }
 
+  void SetPlatformViewManager(std::unique_ptr<PlatformViewManager>&& manager) {
+    engine_->platform_view_manager_ = std::move(manager);
+  }
+
  private:
   FlutterWindowsEngine* engine_;
 
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
new file mode 100644
index 0000000000000..1bfab46b4f217
--- /dev/null
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -0,0 +1,24 @@
+// 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_SHELL_PLATFORM_WINDOWS_TESTING_MOCK_PLATFORM_VIEW_MANAGER_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_TESTING_MOCK_PLATFORM_VIEW_MANAGER_H_
+
+#include "flutter/shell/platform/windows/platform_view_manager.h"
+
+#include "flutter/shell/platform/windows/flutter_windows_engine.h"
+#include "gmock/gmock.h"
+
+namespace flutter {
+
+class MockPlatformViewManager : public PlatformViewManager {
+ public:
+  MockPlatformViewManager(FlutterWindowsEngine* engine) : PlatformViewManager(engine->task_runner(), engine->messenger_wrapper()) {}
+
+  MOCK_METHOD(void, QueuePlatformViewCreation, (std::string_view, const FlutterPlatformViewTypeEntry&));
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_TESTING_MOCK_PLATFORM_VIEW_MANAGER_H_

From ed90810145922d6fecb917ed8bba1383da83d1ea Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Tue, 13 Feb 2024 11:25:16 -0500
Subject: [PATCH 06/27] Add unit test

---
 shell/platform/windows/fixtures/main.dart     | 22 ++++++++++++++++-
 .../flutter_windows_engine_unittests.cc       | 24 +++++++++++++++++++
 .../platform/windows/platform_view_manager.cc | 12 ++++++++--
 .../platform/windows/platform_view_manager.h  |  2 ++
 .../testing/mock_platform_view_manager.h      |  4 +++-
 5 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/shell/platform/windows/fixtures/main.dart b/shell/platform/windows/fixtures/main.dart
index 3e1c25eb6da0e..7e6d750af5fe3 100644
--- a/shell/platform/windows/fixtures/main.dart
+++ b/shell/platform/windows/fixtures/main.dart
@@ -4,7 +4,7 @@
 
 import 'dart:async';
 import 'dart:io' as io;
-import 'dart:typed_data' show ByteData, Uint8List;
+import 'dart:typed_data' show ByteData, Endian, Uint8List;
 import 'dart:ui' as ui;
 import 'dart:convert';
 
@@ -159,6 +159,26 @@ void enableLifecycleToFrom() async {
   });
 }
 
+@pragma('vm:entry-point')
+void sendCreationMethod() async {
+  final List<int> data = <int>[
+    // Method name
+    7, 'create'.length, ...utf8.encode('create'),
+    // Method arguments: {'type': 'type':, 'id': 0}
+    13, 2,
+    7, 'type'.length, ...utf8.encode('type'),
+    7, 'type'.length, ...utf8.encode('type'),
+    7, 'id'.length, ...utf8.encode('id'),
+    3, 0, 0, 0, 0,
+  ];
+
+  final Completer<ByteData?> completed = Completer<ByteData?>();
+  final ByteData bytes = ByteData.sublistView(Uint8List.fromList(data));
+  ui.PlatformDispatcher.instance.sendPlatformMessage('flutter/platform_views', bytes, (ByteData? response) {
+    completed.complete(response);
+  });
+}
+
 @pragma('vm:entry-point')
 void customEntrypoint() {}
 
diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index e44a5592dc1be..8403b42121833 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -12,6 +12,7 @@
 #include "flutter/shell/platform/windows/testing/egl/mock_manager.h"
 #include "flutter/shell/platform/windows/testing/engine_modifier.h"
 #include "flutter/shell/platform/windows/testing/flutter_windows_engine_builder.h"
+#include "flutter/shell/platform/windows/testing/mock_platform_view_manager.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler.h"
 #include "flutter/shell/platform/windows/testing/mock_windows_proc_table.h"
 #include "flutter/shell/platform/windows/testing/test_keyboard.h"
@@ -1169,5 +1170,28 @@ TEST_F(FlutterWindowsEngineTest, ChannelListenedTo) {
   }
 }
 
+TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
+  FlutterWindowsEngineBuilder builder{GetContext()};
+  builder.SetDartEntrypoint("sendCreationMethod");
+  auto engine = builder.Build();
+
+  EngineModifier modifier(engine.get());
+  modifier.embedder_api().RunsAOTCompiledDartCode = []() { return false; };
+
+  bool received_call = false;
+
+  auto manager = std::make_unique<MockPlatformViewManager>(engine.get());
+  EXPECT_CALL(*manager, QueuePlatformViewCreation).WillRepeatedly([&](std::string_view type_name, int64_t id){
+    received_call = true;
+  });
+  modifier.SetPlatformViewManager(std::move(manager));
+
+  engine->Run();
+
+  while (!received_call) {
+    engine->task_runner()->ProcessTasks();
+  }
+}
+
 }  // namespace testing
 }  // namespace flutter
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index 92081210d26d1..9333676515b87 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -9,15 +9,23 @@
 namespace flutter {
 
 namespace {
-constexpr char kChannelName[] = "";
+constexpr char kChannelName[] = "flutter/platform_views";
 }
 
 PlatformViewManager::PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger) : task_runner_(task_runner), channel_(std::make_unique<MethodChannel<EncodableValue>>(binary_messenger, kChannelName, &StandardMethodCodec::GetInstance())) {
-  channel_->SetMethodCallHandler([](const MethodCall<EncodableValue>& call, std::unique_ptr<MethodResult<EncodableValue>> result){
+  channel_->SetMethodCallHandler([this](const MethodCall<EncodableValue>& call, std::unique_ptr<MethodResult<EncodableValue>> result){
+    const auto& args = std::get<EncodableMap>(*call.arguments());
+    if (call.method_name() == "create") {
+      const auto& type = std::get<std::string>(args.find(EncodableValue("type"))->second);
+      const auto& id = std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
+      QueuePlatformViewCreation(type, id);
+    }
     result->Success();
   });
 }
 
+PlatformViewManager::~PlatformViewManager() {}
+
 void PlatformViewManager::QueuePlatformViewCreation(std::string_view type_name, int64_t id) {}
 
 void PlatformViewManager::InstantiatePlatformView(int64_t id) {}
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index e0339fbbcc83e..802518ca9fc9f 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -26,6 +26,8 @@ class PlatformViewManager {
  public:
   PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger);
 
+  virtual ~PlatformViewManager();
+
   virtual void QueuePlatformViewCreation(std::string_view type_name, int64_t id);
 
   void InstantiatePlatformView(int64_t id);
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
index 1bfab46b4f217..a1eec36a19193 100644
--- a/shell/platform/windows/testing/mock_platform_view_manager.h
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -16,7 +16,9 @@ class MockPlatformViewManager : public PlatformViewManager {
  public:
   MockPlatformViewManager(FlutterWindowsEngine* engine) : PlatformViewManager(engine->task_runner(), engine->messenger_wrapper()) {}
 
-  MOCK_METHOD(void, QueuePlatformViewCreation, (std::string_view, const FlutterPlatformViewTypeEntry&));
+  ~MockPlatformViewManager() {}
+
+  MOCK_METHOD(void, QueuePlatformViewCreation, (std::string_view, int64_t id));
 };
 
 }  // namespace flutter

From 5d410ff79517c0b6f84c9802cb333dc47c607457 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Tue, 13 Feb 2024 11:58:17 -0500
Subject: [PATCH 07/27] Formatting

---
 .../testing/stub_flutter_windows_api.h        |  3 +-
 .../windows/flutter_windows_engine.cc         |  9 ++--
 .../flutter_windows_engine_unittests.cc       |  7 +--
 .../platform/windows/platform_view_manager.cc | 44 +++++++++++++------
 .../platform/windows/platform_view_manager.h  | 20 +++++----
 .../platform/windows/public/flutter_windows.h | 15 ++++---
 .../testing/mock_platform_view_manager.h      |  4 +-
 7 files changed, 64 insertions(+), 38 deletions(-)

diff --git a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
index c9b44199f4053..548d0ee93e61c 100644
--- a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
+++ b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
@@ -74,7 +74,8 @@ class StubFlutterWindowsApi {
 
   // Called for FlutterDesktopEngineRegisterPlatformViewType.
   virtual void EngineRegisterPlatformViewType(
-      const char* view_type_name, FlutterPlatformViewTypeEntry view_type) {}
+      const char* view_type_name,
+      FlutterPlatformViewTypeEntry view_type) {}
 
   // Called for FlutterDesktopViewGetHWND.
   virtual HWND ViewGetHWND() { return reinterpret_cast<HWND>(1); }
diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index 784e220ea31aa..c46372cb00c2e 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -381,16 +381,19 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
   args.custom_task_runners = &custom_task_runners;
 
   if (!platform_view_manager_) {
-    platform_view_manager_ = std::make_unique<PlatformViewManager>(task_runner_.get(), messenger_wrapper_.get());
+    platform_view_manager_ = std::make_unique<PlatformViewManager>(
+        task_runner_.get(), messenger_wrapper_.get());
   }
   if (egl_manager_) {
     auto resolver = [](const char* name) -> void* {
       return reinterpret_cast<void*>(::eglGetProcAddress(name));
     };
 
-    compositor_ = std::make_unique<CompositorOpenGL>(platform_view_manager_.get(), this, resolver);
+    compositor_ = std::make_unique<CompositorOpenGL>(
+        platform_view_manager_.get(), this, resolver);
   } else {
-    compositor_ = std::make_unique<CompositorSoftware>(platform_view_manager_.get(), this);
+    compositor_ = std::make_unique<CompositorSoftware>(
+        platform_view_manager_.get(), this);
   }
 
   FlutterCompositor compositor = {};
diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index 8403b42121833..7f2b2aa5bfcd7 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -1181,9 +1181,10 @@ TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
   bool received_call = false;
 
   auto manager = std::make_unique<MockPlatformViewManager>(engine.get());
-  EXPECT_CALL(*manager, QueuePlatformViewCreation).WillRepeatedly([&](std::string_view type_name, int64_t id){
-    received_call = true;
-  });
+  EXPECT_CALL(*manager, QueuePlatformViewCreation)
+      .WillRepeatedly([&](std::string_view type_name, int64_t id) {
+        received_call = true;
+      });
   modifier.SetPlatformViewManager(std::move(manager));
 
   engine->Run();
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index 9333676515b87..de2d7012af03f 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -12,29 +12,45 @@ namespace {
 constexpr char kChannelName[] = "flutter/platform_views";
 }
 
-PlatformViewManager::PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger) : task_runner_(task_runner), channel_(std::make_unique<MethodChannel<EncodableValue>>(binary_messenger, kChannelName, &StandardMethodCodec::GetInstance())) {
-  channel_->SetMethodCallHandler([this](const MethodCall<EncodableValue>& call, std::unique_ptr<MethodResult<EncodableValue>> result){
-    const auto& args = std::get<EncodableMap>(*call.arguments());
-    if (call.method_name() == "create") {
-      const auto& type = std::get<std::string>(args.find(EncodableValue("type"))->second);
-      const auto& id = std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
-      QueuePlatformViewCreation(type, id);
-    }
-    result->Success();
-  });
+PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
+                                         BinaryMessenger* binary_messenger)
+    : task_runner_(task_runner),
+      channel_(std::make_unique<MethodChannel<EncodableValue>>(
+          binary_messenger,
+          kChannelName,
+          &StandardMethodCodec::GetInstance())) {
+  channel_->SetMethodCallHandler(
+      [this](const MethodCall<EncodableValue>& call,
+             std::unique_ptr<MethodResult<EncodableValue>> result) {
+        const auto& args = std::get<EncodableMap>(*call.arguments());
+        if (call.method_name() == "create") {
+          const auto& type =
+              std::get<std::string>(args.find(EncodableValue("type"))->second);
+          const auto& id =
+              std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
+          QueuePlatformViewCreation(type, id);
+        }
+        result->Success();
+      });
 }
 
 PlatformViewManager::~PlatformViewManager() {}
 
-void PlatformViewManager::QueuePlatformViewCreation(std::string_view type_name, int64_t id) {}
+void PlatformViewManager::QueuePlatformViewCreation(std::string_view type_name,
+                                                    int64_t id) {}
 
 void PlatformViewManager::InstantiatePlatformView(int64_t id) {}
 
-void PlatformViewManager::RegisterPlatformViewType(std::string_view type_name, const FlutterPlatformViewTypeEntry& type) {}
+void PlatformViewManager::RegisterPlatformViewType(
+    std::string_view type_name,
+    const FlutterPlatformViewTypeEntry& type) {}
 
-void PlatformViewManager::FocusPlatformView(int64_t id, FocusChangeDirection direction, bool focus) {}
+void PlatformViewManager::FocusPlatformView(int64_t id,
+                                            FocusChangeDirection direction,
+                                            bool focus) {}
 
-std::optional<HWND> PlatformViewManager::GetNativeHandleForId(int64_t id) const {
+std::optional<HWND> PlatformViewManager::GetNativeHandleForId(
+    int64_t id) const {
   return std::nullopt;
 }
 
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 802518ca9fc9f..9afd791683de3 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -16,27 +16,29 @@
 
 namespace flutter {
 
-enum class FocusChangeDirection {
-  kProgrammatic,
-  kForward,
-  kBackward
-};
+enum class FocusChangeDirection { kProgrammatic, kForward, kBackward };
 
 class PlatformViewManager {
  public:
-  PlatformViewManager(TaskRunner* task_runner, BinaryMessenger* binary_messenger);
+  PlatformViewManager(TaskRunner* task_runner,
+                      BinaryMessenger* binary_messenger);
 
   virtual ~PlatformViewManager();
 
-  virtual void QueuePlatformViewCreation(std::string_view type_name, int64_t id);
+  virtual void QueuePlatformViewCreation(std::string_view type_name,
+                                         int64_t id);
 
   void InstantiatePlatformView(int64_t id);
 
-  void RegisterPlatformViewType(std::string_view type_name, const FlutterPlatformViewTypeEntry& type);
+  void RegisterPlatformViewType(std::string_view type_name,
+                                const FlutterPlatformViewTypeEntry& type);
 
-  void FocusPlatformView(int64_t id, FocusChangeDirection direction, bool focus);
+  void FocusPlatformView(int64_t id,
+                         FocusChangeDirection direction,
+                         bool focus);
 
   std::optional<HWND> GetNativeHandleForId(int64_t id) const;
+
  private:
   std::unique_ptr<MethodChannel<EncodableValue>> channel_;
 
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index 4d92d07d7f793..ce8cb6e026a18 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -104,8 +104,8 @@ FLUTTER_EXPORT FlutterDesktopEngineRef FlutterDesktopViewControllerGetEngine(
     FlutterDesktopViewControllerRef controller);
 // Returns the view managed by the given controller.
 
-FLUTTER_EXPORT FlutterDesktopViewRef
-FlutterDesktopViewControllerGetView(FlutterDesktopViewControllerRef controller);
+FLUTTER_EXPORT FlutterDesktopViewRef FlutterDesktopViewControllerGetView(
+    FlutterDesktopViewControllerRef controller);
 
 // Requests new frame from the engine and repaints the view.
 FLUTTER_EXPORT void FlutterDesktopViewControllerForceRedraw(
@@ -167,8 +167,8 @@ FLUTTER_EXPORT bool FlutterDesktopEngineRun(FlutterDesktopEngineRef engine,
 // This should be called on every run of the application-level runloop, and
 // a wait for native events in the runloop should never be longer than the
 // last return value from this function.
-FLUTTER_EXPORT uint64_t
-FlutterDesktopEngineProcessMessages(FlutterDesktopEngineRef engine);
+FLUTTER_EXPORT uint64_t FlutterDesktopEngineProcessMessages(
+    FlutterDesktopEngineRef engine);
 
 FLUTTER_EXPORT void FlutterDesktopEngineReloadSystemFonts(
     FlutterDesktopEngineRef engine);
@@ -187,8 +187,8 @@ FlutterDesktopEngineGetPluginRegistrar(FlutterDesktopEngineRef engine,
 //
 // Callers should use |FlutterDesktopMessengerAddRef| if the returned pointer
 // will potentially outlive 'engine', such as when passing it to another thread.
-FLUTTER_EXPORT FlutterDesktopMessengerRef
-FlutterDesktopEngineGetMessenger(FlutterDesktopEngineRef engine);
+FLUTTER_EXPORT FlutterDesktopMessengerRef FlutterDesktopEngineGetMessenger(
+    FlutterDesktopEngineRef engine);
 
 // Returns the texture registrar associated with the engine.
 FLUTTER_EXPORT FlutterDesktopTextureRegistrarRef
@@ -211,7 +211,8 @@ typedef struct {
   int64_t platform_view_id;
 } FlutterPlatformViewCreationParameters;
 
-typedef HWND (*FlutterPlatformViewFactory)(const FlutterPlatformViewCreationParameters*);
+typedef HWND (*FlutterPlatformViewFactory)(
+    const FlutterPlatformViewCreationParameters*);
 
 typedef struct {
   size_t cb_size;
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
index a1eec36a19193..2ada72c7d8268 100644
--- a/shell/platform/windows/testing/mock_platform_view_manager.h
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -14,7 +14,9 @@ namespace flutter {
 
 class MockPlatformViewManager : public PlatformViewManager {
  public:
-  MockPlatformViewManager(FlutterWindowsEngine* engine) : PlatformViewManager(engine->task_runner(), engine->messenger_wrapper()) {}
+  MockPlatformViewManager(FlutterWindowsEngine* engine)
+      : PlatformViewManager(engine->task_runner(),
+                            engine->messenger_wrapper()) {}
 
   ~MockPlatformViewManager() {}
 

From 484c8c1d80cad36ee73c275c8fc69cbb39d19fcc Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Tue, 13 Feb 2024 13:45:14 -0500
Subject: [PATCH 08/27] License fix, await future

---
 ci/licenses_golden/licenses_flutter       | 4 ++++
 shell/platform/windows/fixtures/main.dart | 1 +
 2 files changed, 5 insertions(+)

diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index 26dfb762b3930..34b0f49b05ddd 100644
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -7290,6 +7290,8 @@ ORIGIN: ../../../flutter/shell/platform/windows/keyboard_utils.cc + ../../../flu
 ORIGIN: ../../../flutter/shell/platform/windows/keyboard_utils.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/platform_handler.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/platform_handler.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/platform_view_manager.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/platform_view_manager.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/public/flutter_windows.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/sequential_id_generator.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/sequential_id_generator.h + ../../../flutter/LICENSE
@@ -10177,6 +10179,8 @@ FILE: ../../../flutter/shell/platform/windows/keyboard_utils.cc
 FILE: ../../../flutter/shell/platform/windows/keyboard_utils.h
 FILE: ../../../flutter/shell/platform/windows/platform_handler.cc
 FILE: ../../../flutter/shell/platform/windows/platform_handler.h
+FILE: ../../../flutter/shell/platform/windows/platform_view_manager.cc
+FILE: ../../../flutter/shell/platform/windows/platform_view_manager.h
 FILE: ../../../flutter/shell/platform/windows/public/flutter_windows.h
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator.cc
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator.h
diff --git a/shell/platform/windows/fixtures/main.dart b/shell/platform/windows/fixtures/main.dart
index 7e6d750af5fe3..3eba41cc634b6 100644
--- a/shell/platform/windows/fixtures/main.dart
+++ b/shell/platform/windows/fixtures/main.dart
@@ -177,6 +177,7 @@ void sendCreationMethod() async {
   ui.PlatformDispatcher.instance.sendPlatformMessage('flutter/platform_views', bytes, (ByteData? response) {
     completed.complete(response);
   });
+  await completed.future;
 }
 
 @pragma('vm:entry-point')

From b8fadd7e9a440c38b8cb392a50ab79a725c4cd35 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Tue, 13 Feb 2024 17:09:16 -0500
Subject: [PATCH 09/27] PR Feedback

---
 shell/platform/windows/compositor.h           |  1 +
 shell/platform/windows/fixtures/main.dart     |  3 ++
 .../platform/windows/platform_view_manager.cc |  8 ++---
 .../platform/windows/platform_view_manager.h  | 36 ++++++++++++++-----
 .../platform/windows/public/flutter_windows.h | 12 ++++---
 5 files changed, 44 insertions(+), 16 deletions(-)

diff --git a/shell/platform/windows/compositor.h b/shell/platform/windows/compositor.h
index 7ecd7dc78e4b2..dcf8f327951a9 100644
--- a/shell/platform/windows/compositor.h
+++ b/shell/platform/windows/compositor.h
@@ -37,6 +37,7 @@ class Compositor {
   virtual bool Present(const FlutterLayer** layers, size_t layers_count) = 0;
 
  protected:
+  // Pointer to the platform view manager owned by the engine.
   PlatformViewManager* platform_view_manager_;
 };
 
diff --git a/shell/platform/windows/fixtures/main.dart b/shell/platform/windows/fixtures/main.dart
index 3eba41cc634b6..d9eb23b3b9a4f 100644
--- a/shell/platform/windows/fixtures/main.dart
+++ b/shell/platform/windows/fixtures/main.dart
@@ -161,6 +161,9 @@ void enableLifecycleToFrom() async {
 
 @pragma('vm:entry-point')
 void sendCreationMethod() async {
+  // The platform view method channel uses the standard method codec.
+  // See https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/services/message_codecs.dart#L262
+  // for the implementation of the encoding and magic number identifiers.
   final List<int> data = <int>[
     // Method name
     7, 'create'.length, ...utf8.encode('create'),
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index de2d7012af03f..9892f1bd00cd9 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -37,20 +37,20 @@ PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
 PlatformViewManager::~PlatformViewManager() {}
 
 void PlatformViewManager::QueuePlatformViewCreation(std::string_view type_name,
-                                                    int64_t id) {}
+                                                    PlatformViewId id) {}
 
-void PlatformViewManager::InstantiatePlatformView(int64_t id) {}
+void PlatformViewManager::InstantiatePlatformView(PlatformViewId id) {}
 
 void PlatformViewManager::RegisterPlatformViewType(
     std::string_view type_name,
     const FlutterPlatformViewTypeEntry& type) {}
 
-void PlatformViewManager::FocusPlatformView(int64_t id,
+void PlatformViewManager::FocusPlatformView(PlatformViewId id,
                                             FocusChangeDirection direction,
                                             bool focus) {}
 
 std::optional<HWND> PlatformViewManager::GetNativeHandleForId(
-    int64_t id) const {
+    PlatformViewId id) const {
   return std::nullopt;
 }
 
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 9afd791683de3..532833c40bb67 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -16,8 +16,16 @@
 
 namespace flutter {
 
-enum class FocusChangeDirection { kProgrammatic, kForward, kBackward };
+// Possible reasons for change of keyboard foucs.
+enum class FocusChangeDirection {
+  kProgrammatic,  // Un-directed focus change.
+  kForward,       // Keyboard focus moves forwards, e.g. TAB-key.
+  kBackward       // Keyboard focus moves backwards, e.g. Shift+TAB.
+};
 
+// Keeps track of registered platform view types and platform view instances,
+// and is responsible for processing and responding to platform view related
+// method invokations from the framework.
 class PlatformViewManager {
  public:
   PlatformViewManager(TaskRunner* task_runner,
@@ -25,29 +33,41 @@ class PlatformViewManager {
 
   virtual ~PlatformViewManager();
 
+  // Add a new platform view instance to be lazily instantiated when it is next
+  // composited.
   virtual void QueuePlatformViewCreation(std::string_view type_name,
-                                         int64_t id);
+                                         PlatformViewId id);
 
-  void InstantiatePlatformView(int64_t id);
+  // Create a queued platform view instance.
+  void InstantiatePlatformView(PlatformViewId id);
 
+  // The runner-facing API calls this method to register a window type
+  // corresponding to a platform view identifier supplied to the widget tree.
   void RegisterPlatformViewType(std::string_view type_name,
                                 const FlutterPlatformViewTypeEntry& type);
 
-  void FocusPlatformView(int64_t id,
+  // The framework may invoke this method when keyboard focus must be given to
+  // the platform view.
+  void FocusPlatformView(PlatformViewId id,
                          FocusChangeDirection direction,
                          bool focus);
 
-  std::optional<HWND> GetNativeHandleForId(int64_t id) const;
+  // Find the HWND corresponding to a platform view id. Returns null if the id
+  // has no associated platform view.
+  std::optional<HWND> GetNativeHandleForId(PlatformViewId id) const;
 
  private:
   std::unique_ptr<MethodChannel<EncodableValue>> channel_;
 
-  std::map<std::string, FlutterPlatformViewTypeEntry> platform_view_types_;
+  std::unordered_map<std::string, FlutterPlatformViewTypeEntry>
+      platform_view_types_;
 
-  std::map<int64_t, HWND> platform_views_;
+  std::unordered_map<PlatformViewId, HWND> platform_views_;
 
-  std::map<int64_t, std::function<HWND()>> pending_platform_views_;
+  std::unordered_map<PlatformViewId, std::function<HWND()>>
+      pending_platform_views_;
 
+  // Pointer to the task runner of the associated engine.
   TaskRunner* task_runner_;
 };
 
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index ce8cb6e026a18..4819a02d6f757 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -203,21 +203,25 @@ FLUTTER_EXPORT void FlutterDesktopEngineSetNextFrameCallback(
     VoidCallback callback,
     void* user_data);
 
+typedef int64_t PlatformViewId;
+
 typedef struct {
-  size_t cb_size;
+  size_t struct_size;
   HWND parent_window;
   const char* platform_view_type;
+  // user_data may hold any necessary additional information for creating a new
+  // platform view. For example, an instance of FlutterWindow.
   void* user_data;
-  int64_t platform_view_id;
+  PlatformViewId platform_view_id;
 } FlutterPlatformViewCreationParameters;
 
 typedef HWND (*FlutterPlatformViewFactory)(
     const FlutterPlatformViewCreationParameters*);
 
 typedef struct {
-  size_t cb_size;
+  size_t struct_size;
   FlutterPlatformViewFactory factory;
-  void* user_data;
+  void* user_data;  // Arbitrary user data supplied to the cretaion struct.
 } FlutterPlatformViewTypeEntry;
 
 FLUTTER_EXPORT void FlutterDesktopEngineRegisterPlatformViewType(

From 1d203f4b8902cf5fc2e242ef00ce60588a2e2318 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:16:48 -0500
Subject: [PATCH 10/27] _internal header file

---
 shell/platform/windows/BUILD.gn               |  1 +
 .../windows/flutter_windows_internal.h        | 26 +++++++++++++++++++
 .../platform/windows/public/flutter_windows.h |  5 ----
 3 files changed, 27 insertions(+), 5 deletions(-)
 create mode 100644 shell/platform/windows/flutter_windows_internal.h

diff --git a/shell/platform/windows/BUILD.gn b/shell/platform/windows/BUILD.gn
index b6953b393c29d..810e720e01259 100644
--- a/shell/platform/windows/BUILD.gn
+++ b/shell/platform/windows/BUILD.gn
@@ -80,6 +80,7 @@ source_set("flutter_windows_source") {
     "flutter_windows.cc",
     "flutter_windows_engine.cc",
     "flutter_windows_engine.h",
+    "flutter_windows_internal.h",
     "flutter_windows_texture_registrar.cc",
     "flutter_windows_texture_registrar.h",
     "flutter_windows_view.cc",
diff --git a/shell/platform/windows/flutter_windows_internal.h b/shell/platform/windows/flutter_windows_internal.h
new file mode 100644
index 0000000000000..a0eb5ff533703
--- /dev/null
+++ b/shell/platform/windows/flutter_windows_internal.h
@@ -0,0 +1,26 @@
+// 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_SHELL_PLATFORM_WINDOWS_FLUTTER_WINDOWS_INTERNAL_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_FLUTTER_WINDOWS_INTERNAL_H_
+
+#include "flutter/shell/platform/windows/public/flutter_windows.h"
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+// Declare functions that are currently in-progress and shall be exposed to the
+// public facing API upon completion.
+
+FLUTTER_EXPORT void FlutterDesktopEngineRegisterPlatformViewType(
+    FlutterDesktopEngineRef engine,
+    const char* view_type_name,
+    FlutterPlatformViewTypeEntry view_type);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_FLUTTER_WINDOWS_INTERNAL_H_
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index 4819a02d6f757..47c3262cd18d4 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -224,11 +224,6 @@ typedef struct {
   void* user_data;  // Arbitrary user data supplied to the cretaion struct.
 } FlutterPlatformViewTypeEntry;
 
-FLUTTER_EXPORT void FlutterDesktopEngineRegisterPlatformViewType(
-    FlutterDesktopEngineRef engine,
-    const char* view_type_name,
-    FlutterPlatformViewTypeEntry view_type);
-
 // ========== View ==========
 
 // Return backing HWND for manipulation in host application.

From b9acc1aa99394c2d2a37de4d00623cc8054fa2a9 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:26:14 -0500
Subject: [PATCH 11/27] Wait to add manager to compositors

---
 shell/platform/windows/compositor.h                  |  7 -------
 shell/platform/windows/compositor_opengl.cc          |  5 ++---
 shell/platform/windows/compositor_opengl.h           |  3 +--
 .../platform/windows/compositor_opengl_unittests.cc  | 12 ++++++------
 shell/platform/windows/compositor_software.cc        |  5 ++---
 shell/platform/windows/compositor_software.h         |  3 +--
 .../windows/compositor_software_unittests.cc         |  8 ++++----
 shell/platform/windows/flutter_windows.cc            |  3 ++-
 shell/platform/windows/flutter_windows_engine.cc     |  6 ++++--
 shell/platform/windows/flutter_windows_engine.h      |  1 +
 10 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/shell/platform/windows/compositor.h b/shell/platform/windows/compositor.h
index dcf8f327951a9..c7691f53e8510 100644
--- a/shell/platform/windows/compositor.h
+++ b/shell/platform/windows/compositor.h
@@ -7,8 +7,6 @@
 
 #include "flutter/shell/platform/embedder/embedder.h"
 
-#include "flutter/shell/platform/windows/platform_view_manager.h"
-
 namespace flutter {
 
 // Enables the Flutter engine to render content on Windows.
@@ -21,7 +19,6 @@ namespace flutter {
 // Platform views are not yet supported.
 class Compositor {
  public:
-  Compositor(PlatformViewManager* manager) : platform_view_manager_(manager) {}
   virtual ~Compositor() = default;
 
   // Creates a backing store used for rendering Flutter content.
@@ -35,10 +32,6 @@ class Compositor {
 
   // Present Flutter content and platform views onto the view.
   virtual bool Present(const FlutterLayer** layers, size_t layers_count) = 0;
-
- protected:
-  // Pointer to the platform view manager owned by the engine.
-  PlatformViewManager* platform_view_manager_;
 };
 
 }  // namespace flutter
diff --git a/shell/platform/windows/compositor_opengl.cc b/shell/platform/windows/compositor_opengl.cc
index d21df04062115..b43f888d65191 100644
--- a/shell/platform/windows/compositor_opengl.cc
+++ b/shell/platform/windows/compositor_opengl.cc
@@ -34,10 +34,9 @@ int GetSupportedTextureFormat(const impeller::DescriptionGLES* description) {
 
 }  // namespace
 
-CompositorOpenGL::CompositorOpenGL(PlatformViewManager* manager,
-                                   FlutterWindowsEngine* engine,
+CompositorOpenGL::CompositorOpenGL(FlutterWindowsEngine* engine,
                                    impeller::ProcTableGLES::Resolver resolver)
-    : Compositor(manager), engine_(engine), resolver_(resolver) {}
+    : engine_(engine), resolver_(resolver) {}
 
 bool CompositorOpenGL::CreateBackingStore(
     const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_opengl.h b/shell/platform/windows/compositor_opengl.h
index f956199b47811..06c22202332e2 100644
--- a/shell/platform/windows/compositor_opengl.h
+++ b/shell/platform/windows/compositor_opengl.h
@@ -17,8 +17,7 @@ namespace flutter {
 // Enables the Flutter engine to render content on Windows using OpenGL.
 class CompositorOpenGL : public Compositor {
  public:
-  CompositorOpenGL(PlatformViewManager* manager,
-                   FlutterWindowsEngine* engine,
+  CompositorOpenGL(FlutterWindowsEngine* engine,
                    impeller::ProcTableGLES::Resolver resolver);
 
   /// |Compositor|
diff --git a/shell/platform/windows/compositor_opengl_unittests.cc b/shell/platform/windows/compositor_opengl_unittests.cc
index 659165e4a2f6a..08fd6dfaf4861 100644
--- a/shell/platform/windows/compositor_opengl_unittests.cc
+++ b/shell/platform/windows/compositor_opengl_unittests.cc
@@ -113,7 +113,7 @@ class CompositorOpenGLTest : public WindowsTest {
 TEST_F(CompositorOpenGLTest, CreateBackingStore) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -127,7 +127,7 @@ TEST_F(CompositorOpenGLTest, CreateBackingStore) {
 TEST_F(CompositorOpenGLTest, InitializationFailure) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -140,7 +140,7 @@ TEST_F(CompositorOpenGLTest, InitializationFailure) {
 TEST_F(CompositorOpenGLTest, Present) {
   UseEngineWithView();
 
-  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -164,7 +164,7 @@ TEST_F(CompositorOpenGLTest, Present) {
 TEST_F(CompositorOpenGLTest, PresentEmpty) {
   UseEngineWithView();
 
-  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{engine(), kMockResolver};
 
   // The context will be bound twice: first to initialize the compositor, second
   // to clear the surface.
@@ -177,7 +177,7 @@ TEST_F(CompositorOpenGLTest, PresentEmpty) {
 TEST_F(CompositorOpenGLTest, HeadlessPresentIgnored) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -199,7 +199,7 @@ TEST_F(CompositorOpenGLTest, HeadlessPresentIgnored) {
 TEST_F(CompositorOpenGLTest, NoSurfaceIgnored) {
   UseEngineWithView(/*add_surface = */ false);
 
-  auto compositor = CompositorOpenGL{nullptr, engine(), kMockResolver};
+  auto compositor = CompositorOpenGL{engine(), kMockResolver};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
diff --git a/shell/platform/windows/compositor_software.cc b/shell/platform/windows/compositor_software.cc
index e7e0e5655e89d..6f6353cbe269c 100644
--- a/shell/platform/windows/compositor_software.cc
+++ b/shell/platform/windows/compositor_software.cc
@@ -8,9 +8,8 @@
 
 namespace flutter {
 
-CompositorSoftware::CompositorSoftware(PlatformViewManager* manager,
-                                       FlutterWindowsEngine* engine)
-    : Compositor(manager), engine_(engine) {}
+CompositorSoftware::CompositorSoftware(FlutterWindowsEngine* engine)
+    : engine_(engine) {}
 
 bool CompositorSoftware::CreateBackingStore(
     const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_software.h b/shell/platform/windows/compositor_software.h
index 49c82a002ffa3..c4e39111b3c1f 100644
--- a/shell/platform/windows/compositor_software.h
+++ b/shell/platform/windows/compositor_software.h
@@ -15,8 +15,7 @@ namespace flutter {
 // rasterization and bitmaps.
 class CompositorSoftware : public Compositor {
  public:
-  CompositorSoftware(PlatformViewManager* manager,
-                     FlutterWindowsEngine* engine);
+  CompositorSoftware(FlutterWindowsEngine* engine);
 
   /// |Compositor|
   bool CreateBackingStore(const FlutterBackingStoreConfig& config,
diff --git a/shell/platform/windows/compositor_software_unittests.cc b/shell/platform/windows/compositor_software_unittests.cc
index bb7b30889d637..bef9fca3061b7 100644
--- a/shell/platform/windows/compositor_software_unittests.cc
+++ b/shell/platform/windows/compositor_software_unittests.cc
@@ -76,7 +76,7 @@ class CompositorSoftwareTest : public WindowsTest {
 TEST_F(CompositorSoftwareTest, CreateBackingStore) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorSoftware{nullptr, engine()};
+  auto compositor = CompositorSoftware{engine()};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -88,7 +88,7 @@ TEST_F(CompositorSoftwareTest, CreateBackingStore) {
 TEST_F(CompositorSoftwareTest, Present) {
   UseEngineWithView();
 
-  auto compositor = CompositorSoftware{nullptr, engine()};
+  auto compositor = CompositorSoftware{engine()};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
@@ -109,7 +109,7 @@ TEST_F(CompositorSoftwareTest, Present) {
 TEST_F(CompositorSoftwareTest, PresentEmpty) {
   UseEngineWithView();
 
-  auto compositor = CompositorSoftware{nullptr, engine()};
+  auto compositor = CompositorSoftware{engine()};
 
   EXPECT_CALL(*view(), ClearSoftwareBitmap).WillOnce(Return(true));
   EXPECT_TRUE(compositor.Present(nullptr, 0));
@@ -118,7 +118,7 @@ TEST_F(CompositorSoftwareTest, PresentEmpty) {
 TEST_F(CompositorSoftwareTest, HeadlessPresentIgnored) {
   UseHeadlessEngine();
 
-  auto compositor = CompositorSoftware{nullptr, engine()};
+  auto compositor = CompositorSoftware{engine()};
 
   FlutterBackingStoreConfig config = {};
   FlutterBackingStore backing_store = {};
diff --git a/shell/platform/windows/flutter_windows.cc b/shell/platform/windows/flutter_windows.cc
index dc1eeb73d80ec..e06c303701112 100644
--- a/shell/platform/windows/flutter_windows.cc
+++ b/shell/platform/windows/flutter_windows.cc
@@ -250,7 +250,8 @@ void FlutterDesktopEngineRegisterPlatformViewType(
     FlutterDesktopEngineRef engine,
     const char* view_type_name,
     FlutterPlatformViewTypeEntry view_type) {
-  // TODO(schectman): forward to platform view manager
+  // TODO(schectman): forward to platform view manager.
+  // https://github.com/flutter/flutter/issues/143375
 }
 
 FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index c46372cb00c2e..f86993808a03c 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -389,11 +389,13 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
       return reinterpret_cast<void*>(::eglGetProcAddress(name));
     };
 
+    // TODO(schectman) Pass the platform view manager to the compositor
+    // constructors: https://github.com/flutter/flutter/issues/143375
     compositor_ = std::make_unique<CompositorOpenGL>(
-        platform_view_manager_.get(), this, resolver);
+        this, resolver);
   } else {
     compositor_ = std::make_unique<CompositorSoftware>(
-        platform_view_manager_.get(), this);
+        this);
   }
 
   FlutterCompositor compositor = {};
diff --git a/shell/platform/windows/flutter_windows_engine.h b/shell/platform/windows/flutter_windows_engine.h
index d564c1e4a102c..fc2bae6b1a7c8 100644
--- a/shell/platform/windows/flutter_windows_engine.h
+++ b/shell/platform/windows/flutter_windows_engine.h
@@ -32,6 +32,7 @@
 #include "flutter/shell/platform/windows/keyboard_handler_base.h"
 #include "flutter/shell/platform/windows/keyboard_key_embedder_handler.h"
 #include "flutter/shell/platform/windows/platform_handler.h"
+#include "flutter/shell/platform/windows/platform_view_manager.h"
 #include "flutter/shell/platform/windows/public/flutter_windows.h"
 #include "flutter/shell/platform/windows/settings_plugin.h"
 #include "flutter/shell/platform/windows/task_runner.h"

From 35eb6887607a42481ac668dcda8268826188d7e2 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:26:58 -0500
Subject: [PATCH 12/27] Rename fixture function

---
 shell/platform/windows/fixtures/main.dart                  | 2 +-
 shell/platform/windows/flutter_windows_engine_unittests.cc | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/shell/platform/windows/fixtures/main.dart b/shell/platform/windows/fixtures/main.dart
index d9eb23b3b9a4f..f0613bbbcd472 100644
--- a/shell/platform/windows/fixtures/main.dart
+++ b/shell/platform/windows/fixtures/main.dart
@@ -160,7 +160,7 @@ void enableLifecycleToFrom() async {
 }
 
 @pragma('vm:entry-point')
-void sendCreationMethod() async {
+void sendCreatePlatformViewMethod() async {
   // The platform view method channel uses the standard method codec.
   // See https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/services/message_codecs.dart#L262
   // for the implementation of the encoding and magic number identifiers.
diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index 7f2b2aa5bfcd7..67cdd7ea73855 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -1172,7 +1172,7 @@ TEST_F(FlutterWindowsEngineTest, ChannelListenedTo) {
 
 TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
   FlutterWindowsEngineBuilder builder{GetContext()};
-  builder.SetDartEntrypoint("sendCreationMethod");
+  builder.SetDartEntrypoint("sendCreatePlatformViewMethod");
   auto engine = builder.Build();
 
   EngineModifier modifier(engine.get());

From 659ebd60a77014aaf7e1cb190f3b61e630959956 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:28:35 -0500
Subject: [PATCH 13/27] Reorder parameters

---
 shell/platform/windows/platform_view_manager.cc | 6 +++---
 shell/platform/windows/platform_view_manager.h  | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index 9892f1bd00cd9..3954daf7ad441 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -28,7 +28,7 @@ PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
               std::get<std::string>(args.find(EncodableValue("type"))->second);
           const auto& id =
               std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
-          QueuePlatformViewCreation(type, id);
+          QueuePlatformViewCreation(id, type);
         }
         result->Success();
       });
@@ -36,8 +36,8 @@ PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
 
 PlatformViewManager::~PlatformViewManager() {}
 
-void PlatformViewManager::QueuePlatformViewCreation(std::string_view type_name,
-                                                    PlatformViewId id) {}
+void PlatformViewManager::QueuePlatformViewCreation(PlatformViewId id,
+                                                    std::string_view type_name) {}
 
 void PlatformViewManager::InstantiatePlatformView(PlatformViewId id) {}
 
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 532833c40bb67..a714cb5931674 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -35,8 +35,8 @@ class PlatformViewManager {
 
   // Add a new platform view instance to be lazily instantiated when it is next
   // composited.
-  virtual void QueuePlatformViewCreation(std::string_view type_name,
-                                         PlatformViewId id);
+  virtual void QueuePlatformViewCreation(PlatformViewId id,
+                                         std::string_view type_name);
 
   // Create a queued platform view instance.
   void InstantiatePlatformView(PlatformViewId id);

From db2851b8fea9c83b73bc4dc1ea48c594ed50df3d Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:32:29 -0500
Subject: [PATCH 14/27] Use constants

---
 shell/platform/windows/fixtures/main.dart | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/shell/platform/windows/fixtures/main.dart b/shell/platform/windows/fixtures/main.dart
index f0613bbbcd472..bae5b7932cc56 100644
--- a/shell/platform/windows/fixtures/main.dart
+++ b/shell/platform/windows/fixtures/main.dart
@@ -164,15 +164,18 @@ void sendCreatePlatformViewMethod() async {
   // The platform view method channel uses the standard method codec.
   // See https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/services/message_codecs.dart#L262
   // for the implementation of the encoding and magic number identifiers.
+  const int valueString = 7;
+  const int valueMap = 13;
+  const int valueInt32 = 3;
   final List<int> data = <int>[
     // Method name
-    7, 'create'.length, ...utf8.encode('create'),
+    valueString, 'create'.length, ...utf8.encode('create'),
     // Method arguments: {'type': 'type':, 'id': 0}
-    13, 2,
-    7, 'type'.length, ...utf8.encode('type'),
-    7, 'type'.length, ...utf8.encode('type'),
-    7, 'id'.length, ...utf8.encode('id'),
-    3, 0, 0, 0, 0,
+    valueMap, 2,
+    valueString, 'type'.length, ...utf8.encode('type'),
+    valueString, 'type'.length, ...utf8.encode('type'),
+    valueString, 'id'.length, ...utf8.encode('id'),
+    valueInt32, 0, 0, 0, 0,
   ];
 
   final Completer<ByteData?> completed = Completer<ByteData?>();

From db48ddde54b2f7fe047468bb5b67add2fe52a004 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:37:53 -0500
Subject: [PATCH 15/27] Reorder params in test

---
 shell/platform/windows/flutter_windows_engine_unittests.cc  | 2 +-
 shell/platform/windows/testing/mock_platform_view_manager.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index 67cdd7ea73855..fbb5074fcff3b 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -1182,7 +1182,7 @@ TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
 
   auto manager = std::make_unique<MockPlatformViewManager>(engine.get());
   EXPECT_CALL(*manager, QueuePlatformViewCreation)
-      .WillRepeatedly([&](std::string_view type_name, int64_t id) {
+      .WillRepeatedly([&](PlatformViewId id, std::string_view type_name) {
         received_call = true;
       });
   modifier.SetPlatformViewManager(std::move(manager));
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
index 2ada72c7d8268..d8774a59a9c78 100644
--- a/shell/platform/windows/testing/mock_platform_view_manager.h
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -20,7 +20,7 @@ class MockPlatformViewManager : public PlatformViewManager {
 
   ~MockPlatformViewManager() {}
 
-  MOCK_METHOD(void, QueuePlatformViewCreation, (std::string_view, int64_t id));
+  MOCK_METHOD(void, QueuePlatformViewCreation, (PlatformViewId id, std::string_view));
 };
 
 }  // namespace flutter

From f87ed964682a36cbf83e3d4d2102f012f300607f Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 13:39:19 -0500
Subject: [PATCH 16/27] Format

---
 shell/platform/windows/flutter_windows_engine.cc            | 6 ++----
 shell/platform/windows/platform_view_manager.cc             | 5 +++--
 shell/platform/windows/testing/mock_platform_view_manager.h | 4 +++-
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index f86993808a03c..8626f0ff237b6 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -391,11 +391,9 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
 
     // TODO(schectman) Pass the platform view manager to the compositor
     // constructors: https://github.com/flutter/flutter/issues/143375
-    compositor_ = std::make_unique<CompositorOpenGL>(
-        this, resolver);
+    compositor_ = std::make_unique<CompositorOpenGL>(this, resolver);
   } else {
-    compositor_ = std::make_unique<CompositorSoftware>(
-        this);
+    compositor_ = std::make_unique<CompositorSoftware>(this);
   }
 
   FlutterCompositor compositor = {};
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index 3954daf7ad441..1526a4d7d7289 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -36,8 +36,9 @@ PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
 
 PlatformViewManager::~PlatformViewManager() {}
 
-void PlatformViewManager::QueuePlatformViewCreation(PlatformViewId id,
-                                                    std::string_view type_name) {}
+void PlatformViewManager::QueuePlatformViewCreation(
+    PlatformViewId id,
+    std::string_view type_name) {}
 
 void PlatformViewManager::InstantiatePlatformView(PlatformViewId id) {}
 
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
index d8774a59a9c78..cd6f435620903 100644
--- a/shell/platform/windows/testing/mock_platform_view_manager.h
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -20,7 +20,9 @@ class MockPlatformViewManager : public PlatformViewManager {
 
   ~MockPlatformViewManager() {}
 
-  MOCK_METHOD(void, QueuePlatformViewCreation, (PlatformViewId id, std::string_view));
+  MOCK_METHOD(void,
+              QueuePlatformViewCreation,
+              (PlatformViewId id, std::string_view));
 };
 
 }  // namespace flutter

From 42f976e1a7fded9f0d2b1fbc22b524906c7c2b0e Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 14 Feb 2024 14:28:19 -0500
Subject: [PATCH 17/27] License

---
 ci/licenses_golden/licenses_flutter | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index 34b0f49b05ddd..185dc221c3685 100644
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -7272,6 +7272,7 @@ ORIGIN: ../../../flutter/shell/platform/windows/flutter_window.h + ../../../flut
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_engine.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_engine.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_internal.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_texture_registrar.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_texture_registrar.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/flutter_windows_view.cc + ../../../flutter/LICENSE
@@ -10161,6 +10162,7 @@ FILE: ../../../flutter/shell/platform/windows/flutter_window.h
 FILE: ../../../flutter/shell/platform/windows/flutter_windows.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_engine.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_engine.h
+FILE: ../../../flutter/shell/platform/windows/flutter_windows_internal.h
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_texture_registrar.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_texture_registrar.h
 FILE: ../../../flutter/shell/platform/windows/flutter_windows_view.cc

From 284b309bb9234c0fd258a161d127d0e8ae06fe67 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Fri, 16 Feb 2024 12:15:13 -0500
Subject: [PATCH 18/27] Break up PlatformViewManager

---
 shell/platform/windows/BUILD.gn               |  2 +
 .../windows/flutter_windows_engine.cc         |  6 +-
 .../platform/windows/flutter_windows_engine.h |  4 +-
 .../flutter_windows_engine_unittests.cc       |  5 +-
 .../platform/windows/platform_view_manager.cc | 47 ++++++++--------
 .../platform/windows/platform_view_manager.h  | 36 ++----------
 .../platform/windows/platform_view_plugin.cc  | 29 ++++++++++
 shell/platform/windows/platform_view_plugin.h | 55 +++++++++++++++++++
 .../windows/testing/engine_modifier.h         |  4 +-
 .../testing/mock_platform_view_manager.h      | 11 ++--
 10 files changed, 128 insertions(+), 71 deletions(-)
 create mode 100644 shell/platform/windows/platform_view_plugin.cc
 create mode 100644 shell/platform/windows/platform_view_plugin.h

diff --git a/shell/platform/windows/BUILD.gn b/shell/platform/windows/BUILD.gn
index 810e720e01259..8b5ed885e97c7 100644
--- a/shell/platform/windows/BUILD.gn
+++ b/shell/platform/windows/BUILD.gn
@@ -101,6 +101,8 @@ source_set("flutter_windows_source") {
     "platform_handler.h",
     "platform_view_manager.cc",
     "platform_view_manager.h",
+    "platform_view_plugin.cc",
+    "platform_view_plugin.h",
     "sequential_id_generator.cc",
     "sequential_id_generator.h",
     "settings_plugin.cc",
diff --git a/shell/platform/windows/flutter_windows_engine.cc b/shell/platform/windows/flutter_windows_engine.cc
index 8626f0ff237b6..282b7c2482c2c 100644
--- a/shell/platform/windows/flutter_windows_engine.cc
+++ b/shell/platform/windows/flutter_windows_engine.cc
@@ -380,9 +380,9 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
 
   args.custom_task_runners = &custom_task_runners;
 
-  if (!platform_view_manager_) {
-    platform_view_manager_ = std::make_unique<PlatformViewManager>(
-        task_runner_.get(), messenger_wrapper_.get());
+  if (!platform_view_plugin_) {
+    platform_view_plugin_ = std::make_unique<PlatformViewPlugin>(
+        messenger_wrapper_.get(), task_runner_.get());
   }
   if (egl_manager_) {
     auto resolver = [](const char* name) -> void* {
diff --git a/shell/platform/windows/flutter_windows_engine.h b/shell/platform/windows/flutter_windows_engine.h
index fc2bae6b1a7c8..df9dde3074121 100644
--- a/shell/platform/windows/flutter_windows_engine.h
+++ b/shell/platform/windows/flutter_windows_engine.h
@@ -32,7 +32,7 @@
 #include "flutter/shell/platform/windows/keyboard_handler_base.h"
 #include "flutter/shell/platform/windows/keyboard_key_embedder_handler.h"
 #include "flutter/shell/platform/windows/platform_handler.h"
-#include "flutter/shell/platform/windows/platform_view_manager.h"
+#include "flutter/shell/platform/windows/platform_view_plugin.h"
 #include "flutter/shell/platform/windows/public/flutter_windows.h"
 #include "flutter/shell/platform/windows/settings_plugin.h"
 #include "flutter/shell/platform/windows/task_runner.h"
@@ -430,7 +430,7 @@ class FlutterWindowsEngine {
 
   std::shared_ptr<egl::ProcTable> gl_;
 
-  std::unique_ptr<PlatformViewManager> platform_view_manager_;
+  std::unique_ptr<PlatformViewPlugin> platform_view_plugin_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(FlutterWindowsEngine);
 };
diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index fbb5074fcff3b..3510560cd7b0c 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -1181,11 +1181,12 @@ TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
   bool received_call = false;
 
   auto manager = std::make_unique<MockPlatformViewManager>(engine.get());
-  EXPECT_CALL(*manager, QueuePlatformViewCreation)
+  EXPECT_CALL(*manager, AddPlatformView)
       .WillRepeatedly([&](PlatformViewId id, std::string_view type_name) {
         received_call = true;
+        return true;
       });
-  modifier.SetPlatformViewManager(std::move(manager));
+  modifier.SetPlatformViewPlugin(std::move(manager));
 
   engine->Run();
 
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index 1526a4d7d7289..aef30e03d2339 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -12,10 +12,8 @@ namespace {
 constexpr char kChannelName[] = "flutter/platform_views";
 }
 
-PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
-                                         BinaryMessenger* binary_messenger)
-    : task_runner_(task_runner),
-      channel_(std::make_unique<MethodChannel<EncodableValue>>(
+PlatformViewManager::PlatformViewManager(BinaryMessenger* binary_messenger)
+    : channel_(std::make_unique<MethodChannel<EncodableValue>>(
           binary_messenger,
           kChannelName,
           &StandardMethodCodec::GetInstance())) {
@@ -28,31 +26,30 @@ PlatformViewManager::PlatformViewManager(TaskRunner* task_runner,
               std::get<std::string>(args.find(EncodableValue("type"))->second);
           const auto& id =
               std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
-          QueuePlatformViewCreation(id, type);
+          if (AddPlatformView(id, type)) {
+            result->Success();
+          } else {
+            result->Error("AddPlatformView", "Failed to add platform view");
+          }
+          return;
+        } else if (call.method_name() == "focus") {
+          const auto& id =
+              std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
+          const auto& direction =
+              std::get<std::int32_t>(args.find(EncodableValue("direction"))->second);
+          const auto& focus =
+              std::get<bool>(args.find(EncodableValue("focus"))->second);
+          if (FocusPlatformView(id, static_cast<FocusChangeDirection>(direction), focus)) {
+            result->Success();
+          } else {
+            result->Error("FocusPlatformView", "Failed to focus platform view");
+          }
+          return;
         }
-        result->Success();
+        result->NotImplemented();
       });
 }
 
 PlatformViewManager::~PlatformViewManager() {}
 
-void PlatformViewManager::QueuePlatformViewCreation(
-    PlatformViewId id,
-    std::string_view type_name) {}
-
-void PlatformViewManager::InstantiatePlatformView(PlatformViewId id) {}
-
-void PlatformViewManager::RegisterPlatformViewType(
-    std::string_view type_name,
-    const FlutterPlatformViewTypeEntry& type) {}
-
-void PlatformViewManager::FocusPlatformView(PlatformViewId id,
-                                            FocusChangeDirection direction,
-                                            bool focus) {}
-
-std::optional<HWND> PlatformViewManager::GetNativeHandleForId(
-    PlatformViewId id) const {
-  return std::nullopt;
-}
-
 }  // namespace flutter
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index a714cb5931674..bff397a08f60c 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -5,10 +5,7 @@
 #ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
 #define FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_MANAGER_H_
 
-#include <functional>
-#include <map>
 #include <memory>
-#include <optional>
 
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/method_channel.h"
 #include "flutter/shell/platform/windows/public/flutter_windows.h"
@@ -28,47 +25,24 @@ enum class FocusChangeDirection {
 // method invokations from the framework.
 class PlatformViewManager {
  public:
-  PlatformViewManager(TaskRunner* task_runner,
-                      BinaryMessenger* binary_messenger);
+  PlatformViewManager(BinaryMessenger* binary_messenger);
 
   virtual ~PlatformViewManager();
 
   // Add a new platform view instance to be lazily instantiated when it is next
   // composited.
-  virtual void QueuePlatformViewCreation(PlatformViewId id,
-                                         std::string_view type_name);
-
-  // Create a queued platform view instance.
-  void InstantiatePlatformView(PlatformViewId id);
-
-  // The runner-facing API calls this method to register a window type
-  // corresponding to a platform view identifier supplied to the widget tree.
-  void RegisterPlatformViewType(std::string_view type_name,
-                                const FlutterPlatformViewTypeEntry& type);
+  virtual bool AddPlatformView(PlatformViewId id,
+                                         std::string_view type_name) = 0;
 
   // The framework may invoke this method when keyboard focus must be given to
   // the platform view.
-  void FocusPlatformView(PlatformViewId id,
+  virtual bool FocusPlatformView(PlatformViewId id,
                          FocusChangeDirection direction,
-                         bool focus);
-
-  // Find the HWND corresponding to a platform view id. Returns null if the id
-  // has no associated platform view.
-  std::optional<HWND> GetNativeHandleForId(PlatformViewId id) const;
+                         bool focus) = 0;
 
  private:
   std::unique_ptr<MethodChannel<EncodableValue>> channel_;
 
-  std::unordered_map<std::string, FlutterPlatformViewTypeEntry>
-      platform_view_types_;
-
-  std::unordered_map<PlatformViewId, HWND> platform_views_;
-
-  std::unordered_map<PlatformViewId, std::function<HWND()>>
-      pending_platform_views_;
-
-  // Pointer to the task runner of the associated engine.
-  TaskRunner* task_runner_;
 };
 
 }  // namespace flutter
diff --git a/shell/platform/windows/platform_view_plugin.cc b/shell/platform/windows/platform_view_plugin.cc
new file mode 100644
index 0000000000000..dc5787a64514f
--- /dev/null
+++ b/shell/platform/windows/platform_view_plugin.cc
@@ -0,0 +1,29 @@
+// 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/shell/platform/windows/platform_view_plugin.h"
+
+namespace flutter {
+
+PlatformViewPlugin::PlatformViewPlugin(BinaryMessenger* messenger, TaskRunner* task_runner) : PlatformViewManager(messenger), task_runner_(task_runner) {}
+
+PlatformViewPlugin::~PlatformViewPlugin() {}
+
+std::optional<HWND> PlatformViewPlugin::GetNativeHandleForId(PlatformViewId id) const {
+  return std::nullopt;
+}
+
+void PlatformViewPlugin::RegisterPlatformViewType(std::string_view type_name, const FlutterPlatformViewTypeEntry& type) {}
+
+void PlatformViewPlugin::InstantiatePlatformView(PlatformViewId id) {}
+
+bool PlatformViewPlugin::AddPlatformView(PlatformViewId id, std::string_view type_name) {
+  return true;
+}
+
+bool PlatformViewPlugin::FocusPlatformView(PlatformViewId id, FocusChangeDirection direction, bool focus) {
+  return true;
+}
+
+}  // namespace flutter
diff --git a/shell/platform/windows/platform_view_plugin.h b/shell/platform/windows/platform_view_plugin.h
new file mode 100644
index 0000000000000..cc579c80d1b1b
--- /dev/null
+++ b/shell/platform/windows/platform_view_plugin.h
@@ -0,0 +1,55 @@
+// 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_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_PLUGIN_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_PLUGIN_H_
+
+#include "flutter/shell/platform/windows/platform_view_manager.h"
+
+#include <functional>
+#include <map>
+#include <optional>
+
+namespace flutter {
+
+class PlatformViewPlugin : public PlatformViewManager {
+ public:
+  PlatformViewPlugin(BinaryMessenger* messenger, TaskRunner* task_runner);
+
+  ~PlatformViewPlugin();
+
+  // Find the HWND corresponding to a platform view id. Returns null if the id
+  // has no associated platform view.
+  std::optional<HWND> GetNativeHandleForId(PlatformViewId id) const;
+
+  // Create a queued platform view instance.
+  void InstantiatePlatformView(PlatformViewId id);
+
+  // The runner-facing API calls this method to register a window type
+  // corresponding to a platform view identifier supplied to the widget tree.
+  void RegisterPlatformViewType(std::string_view type_name,
+                                const FlutterPlatformViewTypeEntry& type);
+
+  // | PlatformViewManager |
+  bool AddPlatformView(PlatformViewId id, std::string_view type_name) override;
+
+  // | PlatformViewManager |
+  bool FocusPlatformView(PlatformViewId id, FocusChangeDirection direction, bool focus) override;
+
+ private:
+  std::unordered_map<std::string, FlutterPlatformViewTypeEntry>
+      platform_view_types_;
+
+  std::unordered_map<PlatformViewId, HWND> platform_views_;
+
+  std::unordered_map<PlatformViewId, std::function<HWND()>>
+      pending_platform_views_;
+
+  // Pointer to the task runner of the associated engine.
+  TaskRunner* task_runner_;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_PLATFORM_VIEW_PLUGIN_H_
diff --git a/shell/platform/windows/testing/engine_modifier.h b/shell/platform/windows/testing/engine_modifier.h
index 2e61ef78e53fe..f33b66afb0676 100644
--- a/shell/platform/windows/testing/engine_modifier.h
+++ b/shell/platform/windows/testing/engine_modifier.h
@@ -68,8 +68,8 @@ class EngineModifier {
     engine_->lifecycle_manager_ = std::move(handler);
   }
 
-  void SetPlatformViewManager(std::unique_ptr<PlatformViewManager>&& manager) {
-    engine_->platform_view_manager_ = std::move(manager);
+  void SetPlatformViewPlugin(std::unique_ptr<PlatformViewPlugin>&& manager) {
+    engine_->platform_view_plugin_ = std::move(manager);
   }
 
  private:
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
index cd6f435620903..90df8bfcbd906 100644
--- a/shell/platform/windows/testing/mock_platform_view_manager.h
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -5,23 +5,22 @@
 #ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_TESTING_MOCK_PLATFORM_VIEW_MANAGER_H_
 #define FLUTTER_SHELL_PLATFORM_WINDOWS_TESTING_MOCK_PLATFORM_VIEW_MANAGER_H_
 
-#include "flutter/shell/platform/windows/platform_view_manager.h"
+#include "flutter/shell/platform/windows/platform_view_plugin.h"
 
 #include "flutter/shell/platform/windows/flutter_windows_engine.h"
 #include "gmock/gmock.h"
 
 namespace flutter {
 
-class MockPlatformViewManager : public PlatformViewManager {
+class MockPlatformViewManager : public PlatformViewPlugin {
  public:
   MockPlatformViewManager(FlutterWindowsEngine* engine)
-      : PlatformViewManager(engine->task_runner(),
-                            engine->messenger_wrapper()) {}
+      : PlatformViewPlugin(engine->messenger_wrapper(), engine->task_runner()) {}
 
   ~MockPlatformViewManager() {}
 
-  MOCK_METHOD(void,
-              QueuePlatformViewCreation,
+  MOCK_METHOD(bool,
+              AddPlatformView,
               (PlatformViewId id, std::string_view));
 };
 

From e000930bf65d3a359341b0674069a49f1cdc724d Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Fri, 16 Feb 2024 12:21:07 -0500
Subject: [PATCH 19/27] PR Feedback

---
 ci/licenses_golden/licenses_flutter           |  4 ++++
 .../platform/windows/platform_view_manager.h  | 19 +++++++++++--------
 shell/platform/windows/platform_view_plugin.h | 16 +++++++++++++---
 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index 185dc221c3685..9467def74913f 100644
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -7293,6 +7293,8 @@ ORIGIN: ../../../flutter/shell/platform/windows/platform_handler.cc + ../../../f
 ORIGIN: ../../../flutter/shell/platform/windows/platform_handler.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/platform_view_manager.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/platform_view_manager.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/platform_view_plugin.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/windows/platform_view_plugin.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/public/flutter_windows.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/sequential_id_generator.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/sequential_id_generator.h + ../../../flutter/LICENSE
@@ -10183,6 +10185,8 @@ FILE: ../../../flutter/shell/platform/windows/platform_handler.cc
 FILE: ../../../flutter/shell/platform/windows/platform_handler.h
 FILE: ../../../flutter/shell/platform/windows/platform_view_manager.cc
 FILE: ../../../flutter/shell/platform/windows/platform_view_manager.h
+FILE: ../../../flutter/shell/platform/windows/platform_view_plugin.cc
+FILE: ../../../flutter/shell/platform/windows/platform_view_plugin.h
 FILE: ../../../flutter/shell/platform/windows/public/flutter_windows.h
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator.cc
 FILE: ../../../flutter/shell/platform/windows/sequential_id_generator.h
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index bff397a08f60c..7528e01eb9b8b 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -20,9 +20,10 @@ enum class FocusChangeDirection {
   kBackward       // Keyboard focus moves backwards, e.g. Shift+TAB.
 };
 
-// Keeps track of registered platform view types and platform view instances,
-// and is responsible for processing and responding to platform view related
-// method invokations from the framework.
+// The platform method handler for platform view related communication between
+// the engine and the framework. This base class is derived by a concrete class
+// (i.e. PlatformViewPlugin) to provide implementation of its abstract virtual
+// methods.
 class PlatformViewManager {
  public:
   PlatformViewManager(BinaryMessenger* binary_messenger);
@@ -30,15 +31,17 @@ class PlatformViewManager {
   virtual ~PlatformViewManager();
 
   // Add a new platform view instance to be lazily instantiated when it is next
-  // composited.
+  // composited. The manager will invoke Success when this method returns true,
+  // and invoke Error otherwise.
   virtual bool AddPlatformView(PlatformViewId id,
-                                         std::string_view type_name) = 0;
+                               std::string_view type_name) = 0;
 
   // The framework may invoke this method when keyboard focus must be given to
-  // the platform view.
+  // the platform view. The manager will invoke Success when this method returns
+  // true, and invoke Error otherwise.
   virtual bool FocusPlatformView(PlatformViewId id,
-                         FocusChangeDirection direction,
-                         bool focus) = 0;
+                                 FocusChangeDirection direction,
+                                 bool focus) = 0;
 
  private:
   std::unique_ptr<MethodChannel<EncodableValue>> channel_;
diff --git a/shell/platform/windows/platform_view_plugin.h b/shell/platform/windows/platform_view_plugin.h
index cc579c80d1b1b..f3d035b64589a 100644
--- a/shell/platform/windows/platform_view_plugin.h
+++ b/shell/platform/windows/platform_view_plugin.h
@@ -13,6 +13,8 @@
 
 namespace flutter {
 
+// The concrete implementation of PlatformViewManager that keeps track of
+// existing platform view types and instances, and handles their instantiation.
 class PlatformViewPlugin : public PlatformViewManager {
  public:
   PlatformViewPlugin(BinaryMessenger* messenger, TaskRunner* task_runner);
@@ -23,18 +25,26 @@ class PlatformViewPlugin : public PlatformViewManager {
   // has no associated platform view.
   std::optional<HWND> GetNativeHandleForId(PlatformViewId id) const;
 
-  // Create a queued platform view instance.
-  void InstantiatePlatformView(PlatformViewId id);
-
   // The runner-facing API calls this method to register a window type
   // corresponding to a platform view identifier supplied to the widget tree.
   void RegisterPlatformViewType(std::string_view type_name,
                                 const FlutterPlatformViewTypeEntry& type);
 
+  // Create a queued platform view instance after it has been added.
+  // id must correspond to an identifier that has already been added with
+  // AddPlatformView.
+  // This method will create the platform view within a task queued to the
+  // engine's TaskRunner, which will run on the UI thread.
+  void InstantiatePlatformView(PlatformViewId id);
+
   // | PlatformViewManager |
+  // type_name must correspond to a string that has already been registered
+  // with RegisterPlatformViewType.
   bool AddPlatformView(PlatformViewId id, std::string_view type_name) override;
 
   // | PlatformViewManager |
+  // id must correspond to an identifier that has already been added with
+  // AddPlatformView.
   bool FocusPlatformView(PlatformViewId id, FocusChangeDirection direction, bool focus) override;
 
  private:

From 676868fd441f1abfdd6095ea78d0f90f867f10d6 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Fri, 16 Feb 2024 12:22:05 -0500
Subject: [PATCH 20/27] Formatting

---
 .../platform/windows/platform_view_manager.cc  |  7 ++++---
 shell/platform/windows/platform_view_manager.h |  1 -
 shell/platform/windows/platform_view_plugin.cc | 18 +++++++++++++-----
 shell/platform/windows/platform_view_plugin.h  |  4 +++-
 .../testing/mock_platform_view_manager.h       |  7 +++----
 5 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index aef30e03d2339..8de30fdeb81f0 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -35,11 +35,12 @@ PlatformViewManager::PlatformViewManager(BinaryMessenger* binary_messenger)
         } else if (call.method_name() == "focus") {
           const auto& id =
               std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
-          const auto& direction =
-              std::get<std::int32_t>(args.find(EncodableValue("direction"))->second);
+          const auto& direction = std::get<std::int32_t>(
+              args.find(EncodableValue("direction"))->second);
           const auto& focus =
               std::get<bool>(args.find(EncodableValue("focus"))->second);
-          if (FocusPlatformView(id, static_cast<FocusChangeDirection>(direction), focus)) {
+          if (FocusPlatformView(
+                  id, static_cast<FocusChangeDirection>(direction), focus)) {
             result->Success();
           } else {
             result->Error("FocusPlatformView", "Failed to focus platform view");
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 7528e01eb9b8b..7cbe25ce8d9e7 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -45,7 +45,6 @@ class PlatformViewManager {
 
  private:
   std::unique_ptr<MethodChannel<EncodableValue>> channel_;
-
 };
 
 }  // namespace flutter
diff --git a/shell/platform/windows/platform_view_plugin.cc b/shell/platform/windows/platform_view_plugin.cc
index dc5787a64514f..bad994dfa05af 100644
--- a/shell/platform/windows/platform_view_plugin.cc
+++ b/shell/platform/windows/platform_view_plugin.cc
@@ -6,23 +6,31 @@
 
 namespace flutter {
 
-PlatformViewPlugin::PlatformViewPlugin(BinaryMessenger* messenger, TaskRunner* task_runner) : PlatformViewManager(messenger), task_runner_(task_runner) {}
+PlatformViewPlugin::PlatformViewPlugin(BinaryMessenger* messenger,
+                                       TaskRunner* task_runner)
+    : PlatformViewManager(messenger), task_runner_(task_runner) {}
 
 PlatformViewPlugin::~PlatformViewPlugin() {}
 
-std::optional<HWND> PlatformViewPlugin::GetNativeHandleForId(PlatformViewId id) const {
+std::optional<HWND> PlatformViewPlugin::GetNativeHandleForId(
+    PlatformViewId id) const {
   return std::nullopt;
 }
 
-void PlatformViewPlugin::RegisterPlatformViewType(std::string_view type_name, const FlutterPlatformViewTypeEntry& type) {}
+void PlatformViewPlugin::RegisterPlatformViewType(
+    std::string_view type_name,
+    const FlutterPlatformViewTypeEntry& type) {}
 
 void PlatformViewPlugin::InstantiatePlatformView(PlatformViewId id) {}
 
-bool PlatformViewPlugin::AddPlatformView(PlatformViewId id, std::string_view type_name) {
+bool PlatformViewPlugin::AddPlatformView(PlatformViewId id,
+                                         std::string_view type_name) {
   return true;
 }
 
-bool PlatformViewPlugin::FocusPlatformView(PlatformViewId id, FocusChangeDirection direction, bool focus) {
+bool PlatformViewPlugin::FocusPlatformView(PlatformViewId id,
+                                           FocusChangeDirection direction,
+                                           bool focus) {
   return true;
 }
 
diff --git a/shell/platform/windows/platform_view_plugin.h b/shell/platform/windows/platform_view_plugin.h
index f3d035b64589a..928b691f58cd1 100644
--- a/shell/platform/windows/platform_view_plugin.h
+++ b/shell/platform/windows/platform_view_plugin.h
@@ -45,7 +45,9 @@ class PlatformViewPlugin : public PlatformViewManager {
   // | PlatformViewManager |
   // id must correspond to an identifier that has already been added with
   // AddPlatformView.
-  bool FocusPlatformView(PlatformViewId id, FocusChangeDirection direction, bool focus) override;
+  bool FocusPlatformView(PlatformViewId id,
+                         FocusChangeDirection direction,
+                         bool focus) override;
 
  private:
   std::unordered_map<std::string, FlutterPlatformViewTypeEntry>
diff --git a/shell/platform/windows/testing/mock_platform_view_manager.h b/shell/platform/windows/testing/mock_platform_view_manager.h
index 90df8bfcbd906..a3c6922269932 100644
--- a/shell/platform/windows/testing/mock_platform_view_manager.h
+++ b/shell/platform/windows/testing/mock_platform_view_manager.h
@@ -15,13 +15,12 @@ namespace flutter {
 class MockPlatformViewManager : public PlatformViewPlugin {
  public:
   MockPlatformViewManager(FlutterWindowsEngine* engine)
-      : PlatformViewPlugin(engine->messenger_wrapper(), engine->task_runner()) {}
+      : PlatformViewPlugin(engine->messenger_wrapper(), engine->task_runner()) {
+  }
 
   ~MockPlatformViewManager() {}
 
-  MOCK_METHOD(bool,
-              AddPlatformView,
-              (PlatformViewId id, std::string_view));
+  MOCK_METHOD(bool, AddPlatformView, (PlatformViewId id, std::string_view));
 };
 
 }  // namespace flutter

From 6e6ef7ebabd2a9d719f0c1b003cbbf7613b8b5bc Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Fri, 16 Feb 2024 13:51:16 -0500
Subject: [PATCH 21/27] PR Feedback

---
 shell/platform/windows/fixtures/main.dart     | 12 +++--
 .../platform/windows/platform_view_manager.cc | 54 ++++++++++++++-----
 .../platform/windows/platform_view_manager.h  |  2 +-
 .../platform/windows/platform_view_plugin.cc  | 10 ++++
 4 files changed, 60 insertions(+), 18 deletions(-)

diff --git a/shell/platform/windows/fixtures/main.dart b/shell/platform/windows/fixtures/main.dart
index bae5b7932cc56..4512c58e93b22 100644
--- a/shell/platform/windows/fixtures/main.dart
+++ b/shell/platform/windows/fixtures/main.dart
@@ -167,14 +167,18 @@ void sendCreatePlatformViewMethod() async {
   const int valueString = 7;
   const int valueMap = 13;
   const int valueInt32 = 3;
+  const String method = 'create';
+  const String typeKey = 'viewType';
+  const String typeValue = 'type';
+  const String idKey = 'id';
   final List<int> data = <int>[
     // Method name
-    valueString, 'create'.length, ...utf8.encode('create'),
+    valueString, method.length, ...utf8.encode(method),
     // Method arguments: {'type': 'type':, 'id': 0}
     valueMap, 2,
-    valueString, 'type'.length, ...utf8.encode('type'),
-    valueString, 'type'.length, ...utf8.encode('type'),
-    valueString, 'id'.length, ...utf8.encode('id'),
+    valueString, typeKey.length, ...utf8.encode(typeKey),
+    valueString, typeValue.length, ...utf8.encode(typeValue),
+    valueString, idKey.length, ...utf8.encode(idKey),
     valueInt32, 0, 0, 0, 0,
   ];
 
diff --git a/shell/platform/windows/platform_view_manager.cc b/shell/platform/windows/platform_view_manager.cc
index 8de30fdeb81f0..cb403673597b6 100644
--- a/shell/platform/windows/platform_view_manager.cc
+++ b/shell/platform/windows/platform_view_manager.cc
@@ -10,7 +10,13 @@ namespace flutter {
 
 namespace {
 constexpr char kChannelName[] = "flutter/platform_views";
-}
+constexpr char kCreateMethod[] = "create";
+constexpr char kFocusMethod[] = "focus";
+constexpr char kViewTypeParameter[] = "viewType";
+constexpr char kIdParameter[] = "id";
+constexpr char kDirectionParameter[] = "direction";
+constexpr char kFocusParameter[] = "focus";
+}  // namespace
 
 PlatformViewManager::PlatformViewManager(BinaryMessenger* binary_messenger)
     : channel_(std::make_unique<MethodChannel<EncodableValue>>(
@@ -21,24 +27,46 @@ PlatformViewManager::PlatformViewManager(BinaryMessenger* binary_messenger)
       [this](const MethodCall<EncodableValue>& call,
              std::unique_ptr<MethodResult<EncodableValue>> result) {
         const auto& args = std::get<EncodableMap>(*call.arguments());
-        if (call.method_name() == "create") {
-          const auto& type =
-              std::get<std::string>(args.find(EncodableValue("type"))->second);
-          const auto& id =
-              std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
+        if (call.method_name() == kCreateMethod) {
+          const auto& type_itr = args.find(EncodableValue(kViewTypeParameter));
+          const auto& id_itr = args.find(EncodableValue(kIdParameter));
+          if (type_itr == args.end()) {
+            result->Error("AddPlatformView", "Parameter viewType is required");
+            return;
+          }
+          if (id_itr == args.end()) {
+            result->Error("AddPlatformView", "Parameter id is required");
+            return;
+          }
+          const auto& type = std::get<std::string>(type_itr->second);
+          const auto& id = std::get<std::int32_t>(id_itr->second);
           if (AddPlatformView(id, type)) {
             result->Success();
           } else {
             result->Error("AddPlatformView", "Failed to add platform view");
           }
           return;
-        } else if (call.method_name() == "focus") {
-          const auto& id =
-              std::get<std::int32_t>(args.find(EncodableValue("id"))->second);
-          const auto& direction = std::get<std::int32_t>(
-              args.find(EncodableValue("direction"))->second);
-          const auto& focus =
-              std::get<bool>(args.find(EncodableValue("focus"))->second);
+        } else if (call.method_name() == kFocusMethod) {
+          const auto& id_itr = args.find(EncodableValue(kIdParameter));
+          const auto& direction_itr =
+              args.find(EncodableValue(kDirectionParameter));
+          const auto& focus_itr = args.find(EncodableValue(kFocusParameter));
+          if (id_itr == args.end()) {
+            result->Error("FocusPlatformView", "Parameter id is required");
+            return;
+          }
+          if (direction_itr == args.end()) {
+            result->Error("FocusPlatformView",
+                          "Parameter direction is required");
+            return;
+          }
+          if (focus_itr == args.end()) {
+            result->Error("FocusPlatformView", "Parameter focus is required");
+            return;
+          }
+          const auto& id = std::get<std::int32_t>(id_itr->second);
+          const auto& direction = std::get<std::int32_t>(direction_itr->second);
+          const auto& focus = std::get<bool>(focus_itr->second);
           if (FocusPlatformView(
                   id, static_cast<FocusChangeDirection>(direction), focus)) {
             result->Success();
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 7cbe25ce8d9e7..49c645e659b0d 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -16,7 +16,7 @@ namespace flutter {
 // Possible reasons for change of keyboard foucs.
 enum class FocusChangeDirection {
   kProgrammatic,  // Un-directed focus change.
-  kForward,       // Keyboard focus moves forwards, e.g. TAB-key.
+  kForward,       // Keyboard focus moves forwards, e.g. TAB key.
   kBackward       // Keyboard focus moves backwards, e.g. Shift+TAB.
 };
 
diff --git a/shell/platform/windows/platform_view_plugin.cc b/shell/platform/windows/platform_view_plugin.cc
index bad994dfa05af..a54ebfebf1a64 100644
--- a/shell/platform/windows/platform_view_plugin.cc
+++ b/shell/platform/windows/platform_view_plugin.cc
@@ -12,22 +12,32 @@ PlatformViewPlugin::PlatformViewPlugin(BinaryMessenger* messenger,
 
 PlatformViewPlugin::~PlatformViewPlugin() {}
 
+// TODO(schectman): Impelement platform view lookup.
+// https://github.com/flutter/flutter/issues/143375
 std::optional<HWND> PlatformViewPlugin::GetNativeHandleForId(
     PlatformViewId id) const {
   return std::nullopt;
 }
 
+// TODO(schectman): Impelement platform view type registration.
+// https://github.com/flutter/flutter/issues/143375
 void PlatformViewPlugin::RegisterPlatformViewType(
     std::string_view type_name,
     const FlutterPlatformViewTypeEntry& type) {}
 
+// TODO(schectman): Impelement platform view instantiation.
+// https://github.com/flutter/flutter/issues/143375
 void PlatformViewPlugin::InstantiatePlatformView(PlatformViewId id) {}
 
+// TODO(schectman): Impelement platform view addition.
+// https://github.com/flutter/flutter/issues/143375
 bool PlatformViewPlugin::AddPlatformView(PlatformViewId id,
                                          std::string_view type_name) {
   return true;
 }
 
+// TODO(schectman): Impelement platform view focus request.
+// https://github.com/flutter/flutter/issues/143375
 bool PlatformViewPlugin::FocusPlatformView(PlatformViewId id,
                                            FocusChangeDirection direction,
                                            bool focus) {

From 22a9e4605911e5b70de115017c3fb3430e672307 Mon Sep 17 00:00:00 2001
From: yaakovschectman <109111084+yaakovschectman@users.noreply.github.com>
Date: Wed, 21 Feb 2024 06:46:46 -0500
Subject: [PATCH 22/27] Update
 shell/platform/windows/flutter_windows_engine_unittests.cc
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
---
 shell/platform/windows/flutter_windows_engine_unittests.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index 3510560cd7b0c..d7aad7abc77b1 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -1175,7 +1175,7 @@ TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
   builder.SetDartEntrypoint("sendCreatePlatformViewMethod");
   auto engine = builder.Build();
 
-  EngineModifier modifier(engine.get());
+  EngineModifier modifier{engine.get()};
   modifier.embedder_api().RunsAOTCompiledDartCode = []() { return false; };
 
   bool received_call = false;

From 95a849819fdf4e9c013139bfd8047edcb194dc84 Mon Sep 17 00:00:00 2001
From: yaakovschectman <109111084+yaakovschectman@users.noreply.github.com>
Date: Wed, 21 Feb 2024 14:51:46 -0500
Subject: [PATCH 23/27] Update shell/platform/windows/platform_view_manager.h
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
---
 shell/platform/windows/platform_view_manager.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 49c645e659b0d..43b13250f2dd9 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -13,7 +13,7 @@
 
 namespace flutter {
 
-// Possible reasons for change of keyboard foucs.
+// Possible reasons for change of keyboard focus.
 enum class FocusChangeDirection {
   kProgrammatic,  // Un-directed focus change.
   kForward,       // Keyboard focus moves forwards, e.g. TAB key.

From 1fa97f3a43fba8dcb3776a9e48357ce497d9192f Mon Sep 17 00:00:00 2001
From: yaakovschectman <109111084+yaakovschectman@users.noreply.github.com>
Date: Wed, 21 Feb 2024 14:51:54 -0500
Subject: [PATCH 24/27] Update shell/platform/windows/public/flutter_windows.h
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
---
 shell/platform/windows/public/flutter_windows.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index 47c3262cd18d4..1d6168b95449a 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -221,7 +221,7 @@ typedef HWND (*FlutterPlatformViewFactory)(
 typedef struct {
   size_t struct_size;
   FlutterPlatformViewFactory factory;
-  void* user_data;  // Arbitrary user data supplied to the cretaion struct.
+  void* user_data;  // Arbitrary user data supplied to the creation struct.
 } FlutterPlatformViewTypeEntry;
 
 // ========== View ==========

From 5453b290a3d2b17874aeec989225dd3c14a68bb6 Mon Sep 17 00:00:00 2001
From: yaakovschectman <109111084+yaakovschectman@users.noreply.github.com>
Date: Wed, 21 Feb 2024 14:52:25 -0500
Subject: [PATCH 25/27] Update
 shell/platform/windows/flutter_windows_engine_unittests.cc
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
---
 shell/platform/windows/flutter_windows_engine_unittests.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/windows/flutter_windows_engine_unittests.cc b/shell/platform/windows/flutter_windows_engine_unittests.cc
index d7aad7abc77b1..5650d25336677 100644
--- a/shell/platform/windows/flutter_windows_engine_unittests.cc
+++ b/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -1182,7 +1182,7 @@ TEST_F(FlutterWindowsEngineTest, ReceivePlatformViewMessage) {
 
   auto manager = std::make_unique<MockPlatformViewManager>(engine.get());
   EXPECT_CALL(*manager, AddPlatformView)
-      .WillRepeatedly([&](PlatformViewId id, std::string_view type_name) {
+      .WillOnce([&](PlatformViewId id, std::string_view type_name) {
         received_call = true;
         return true;
       });

From dfa6b73bf0892d6b0f5f61e96770139a364cf8e4 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Wed, 21 Feb 2024 14:59:45 -0500
Subject: [PATCH 26/27] PR Feedback

---
 .../testing/stub_flutter_windows_api.h        |  1 +
 .../windows/flutter_windows_internal.h        | 21 +++++++++++++++++++
 .../platform/windows/platform_view_manager.h  |  2 +-
 shell/platform/windows/platform_view_plugin.h | 10 ++++-----
 .../platform/windows/public/flutter_windows.h | 21 -------------------
 5 files changed, 28 insertions(+), 27 deletions(-)

diff --git a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
index 548d0ee93e61c..43eaa50074132 100644
--- a/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
+++ b/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h
@@ -7,6 +7,7 @@
 
 #include <memory>
 
+#include "flutter/shell/platform/windows/flutter_windows_internal.h"
 #include "flutter/shell/platform/windows/public/flutter_windows.h"
 
 namespace flutter {
diff --git a/shell/platform/windows/flutter_windows_internal.h b/shell/platform/windows/flutter_windows_internal.h
index a0eb5ff533703..47b98e983a48a 100644
--- a/shell/platform/windows/flutter_windows_internal.h
+++ b/shell/platform/windows/flutter_windows_internal.h
@@ -14,6 +14,27 @@ extern "C" {
 // Declare functions that are currently in-progress and shall be exposed to the
 // public facing API upon completion.
 
+typedef int64_t PlatformViewId;
+
+typedef struct {
+  size_t struct_size;
+  HWND parent_window;
+  const char* platform_view_type;
+  // user_data may hold any necessary additional information for creating a new
+  // platform view. For example, an instance of FlutterWindow.
+  void* user_data;
+  PlatformViewId platform_view_id;
+} FlutterPlatformViewCreationParameters;
+
+typedef HWND (*FlutterPlatformViewFactory)(
+    const FlutterPlatformViewCreationParameters*);
+
+typedef struct {
+  size_t struct_size;
+  FlutterPlatformViewFactory factory;
+  void* user_data;  // Arbitrary user data supplied to the creation struct.
+} FlutterPlatformViewTypeEntry;
+
 FLUTTER_EXPORT void FlutterDesktopEngineRegisterPlatformViewType(
     FlutterDesktopEngineRef engine,
     const char* view_type_name,
diff --git a/shell/platform/windows/platform_view_manager.h b/shell/platform/windows/platform_view_manager.h
index 43b13250f2dd9..d4b736f9602fc 100644
--- a/shell/platform/windows/platform_view_manager.h
+++ b/shell/platform/windows/platform_view_manager.h
@@ -8,7 +8,7 @@
 #include <memory>
 
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/method_channel.h"
-#include "flutter/shell/platform/windows/public/flutter_windows.h"
+#include "flutter/shell/platform/windows/flutter_windows_internal.h"
 #include "flutter/shell/platform/windows/task_runner.h"
 
 namespace flutter {
diff --git a/shell/platform/windows/platform_view_plugin.h b/shell/platform/windows/platform_view_plugin.h
index 928b691f58cd1..490d21a8e0ba2 100644
--- a/shell/platform/windows/platform_view_plugin.h
+++ b/shell/platform/windows/platform_view_plugin.h
@@ -30,6 +30,11 @@ class PlatformViewPlugin : public PlatformViewManager {
   void RegisterPlatformViewType(std::string_view type_name,
                                 const FlutterPlatformViewTypeEntry& type);
 
+  // | PlatformViewManager |
+  // type_name must correspond to a string that has already been registered
+  // with RegisterPlatformViewType.
+  bool AddPlatformView(PlatformViewId id, std::string_view type_name) override;
+
   // Create a queued platform view instance after it has been added.
   // id must correspond to an identifier that has already been added with
   // AddPlatformView.
@@ -37,11 +42,6 @@ class PlatformViewPlugin : public PlatformViewManager {
   // engine's TaskRunner, which will run on the UI thread.
   void InstantiatePlatformView(PlatformViewId id);
 
-  // | PlatformViewManager |
-  // type_name must correspond to a string that has already been registered
-  // with RegisterPlatformViewType.
-  bool AddPlatformView(PlatformViewId id, std::string_view type_name) override;
-
   // | PlatformViewManager |
   // id must correspond to an identifier that has already been added with
   // AddPlatformView.
diff --git a/shell/platform/windows/public/flutter_windows.h b/shell/platform/windows/public/flutter_windows.h
index 1d6168b95449a..a9f7f973fb987 100644
--- a/shell/platform/windows/public/flutter_windows.h
+++ b/shell/platform/windows/public/flutter_windows.h
@@ -203,27 +203,6 @@ FLUTTER_EXPORT void FlutterDesktopEngineSetNextFrameCallback(
     VoidCallback callback,
     void* user_data);
 
-typedef int64_t PlatformViewId;
-
-typedef struct {
-  size_t struct_size;
-  HWND parent_window;
-  const char* platform_view_type;
-  // user_data may hold any necessary additional information for creating a new
-  // platform view. For example, an instance of FlutterWindow.
-  void* user_data;
-  PlatformViewId platform_view_id;
-} FlutterPlatformViewCreationParameters;
-
-typedef HWND (*FlutterPlatformViewFactory)(
-    const FlutterPlatformViewCreationParameters*);
-
-typedef struct {
-  size_t struct_size;
-  FlutterPlatformViewFactory factory;
-  void* user_data;  // Arbitrary user data supplied to the creation struct.
-} FlutterPlatformViewTypeEntry;
-
 // ========== View ==========
 
 // Return backing HWND for manipulation in host application.

From 585ca1110fd9db885a6afe2b3414da0af6ebb733 Mon Sep 17 00:00:00 2001
From: schectman <schectman@google.com>
Date: Thu, 22 Feb 2024 16:17:35 -0500
Subject: [PATCH 27/27] Include internal header

---
 shell/platform/windows/BUILD.gn | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/shell/platform/windows/BUILD.gn b/shell/platform/windows/BUILD.gn
index a91224d0c5b99..fe72e926d48dd 100644
--- a/shell/platform/windows/BUILD.gn
+++ b/shell/platform/windows/BUILD.gn
@@ -8,6 +8,7 @@ import("//flutter/shell/platform/glfw/config.gni")
 import("//flutter/testing/testing.gni")
 
 _public_headers = [ "public/flutter_windows.h" ]
+_internal_headers = [ "flutter_windows_internal.h" ]
 
 config("relative_angle_headers") {
   include_dirs = [ "//third_party/angle/include" ]
@@ -24,7 +25,7 @@ config("relative_flutter_windows_headers") {
 # The headers are a separate source set since the client wrapper is allowed
 # to depend on the public headers, but none of the rest of the code.
 source_set("flutter_windows_headers") {
-  public = _public_headers
+  public = _public_headers + _internal_headers
 
   public_deps = [ "//flutter/shell/platform/common:common_cpp_library_headers" ]
 
@@ -80,7 +81,6 @@ source_set("flutter_windows_source") {
     "flutter_windows.cc",
     "flutter_windows_engine.cc",
     "flutter_windows_engine.h",
-    "flutter_windows_internal.h",
     "flutter_windows_texture_registrar.cc",
     "flutter_windows_texture_registrar.h",
     "flutter_windows_view.cc",