shell/platform/windows/flutter_windows_engine.cc

// 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/flutter_windows_engine.h"

#include <dwmapi.h>

#include <filesystem>
#include <iostream>
#include <sstream>

#include "flutter/fml/logging.h"
#include "flutter/fml/paths.h"
#include "flutter/fml/platform/win/wstring_conversion.h"
#include "flutter/shell/platform/common/client_wrapper/binary_messenger_impl.h"
#include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_message_codec.h"
#include "flutter/shell/platform/common/path_utils.h"
#include "flutter/shell/platform/windows/accessibility_bridge_windows.h"
#include "flutter/shell/platform/windows/flutter_windows_view.h"
#include "flutter/shell/platform/windows/system_utils.h"
#include "flutter/shell/platform/windows/task_runner.h"
#include "flutter/third_party/accessibility/ax/ax_node.h"

// winbase.h defines GetCurrentTime as a macro.
#undef GetCurrentTime

static constexpr char kAccessibilityChannelName[] = "flutter/accessibility";

namespace flutter {

namespace {

// Lifted from vsync_waiter_fallback.cc
static std::chrono::nanoseconds SnapToNextTick(
    std::chrono::nanoseconds value,
    std::chrono::nanoseconds tick_phase,
    std::chrono::nanoseconds tick_interval) {
  std::chrono::nanoseconds offset = (tick_phase - value) % tick_interval;
  if (offset != std::chrono::nanoseconds::zero())
    offset = offset + tick_interval;
  return value + offset;
}

// Creates and returns a FlutterRendererConfig that renders to the view (if any)
// of a FlutterWindowsEngine, using OpenGL (via ANGLE).
// The user_data received by the render callbacks refers to the
// FlutterWindowsEngine.
FlutterRendererConfig GetOpenGLRendererConfig() {
  FlutterRendererConfig config = {};
  config.type = kOpenGL;
  config.open_gl.struct_size = sizeof(config.open_gl);
  config.open_gl.make_current = [](void* user_data) -> bool {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!host->view()) {
      return false;
    }
    return host->view()->MakeCurrent();
  };
  config.open_gl.clear_current = [](void* user_data) -> bool {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!host->view()) {
      return false;
    }
    return host->view()->ClearContext();
  };
  config.open_gl.present = [](void* user_data) -> bool {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!host->view()) {
      return false;
    }
    return host->view()->SwapBuffers();
  };
  config.open_gl.fbo_reset_after_present = true;
  config.open_gl.fbo_with_frame_info_callback =
      [](void* user_data, const FlutterFrameInfo* info) -> uint32_t {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (host->view()) {
      return host->view()->GetFrameBufferId(info->size.width,
                                            info->size.height);
    } else {
      return kWindowFrameBufferID;
    }
  };
  config.open_gl.gl_proc_resolver = [](void* user_data,
                                       const char* what) -> void* {
    return reinterpret_cast<void*>(eglGetProcAddress(what));
  };
  config.open_gl.make_resource_current = [](void* user_data) -> bool {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!host->view()) {
      return false;
    }
    return host->view()->MakeResourceCurrent();
  };
  config.open_gl.gl_external_texture_frame_callback =
      [](void* user_data, int64_t texture_id, size_t width, size_t height,
         FlutterOpenGLTexture* texture) -> bool {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!host->texture_registrar()) {
      return false;
    }
    return host->texture_registrar()->PopulateTexture(texture_id, width, height,
                                                      texture);
  };
  return config;
}

// Creates and returns a FlutterRendererConfig that renders to the view (if any)
// of a FlutterWindowsEngine, using software rasterization.
// The user_data received by the render callbacks refers to the
// FlutterWindowsEngine.
FlutterRendererConfig GetSoftwareRendererConfig() {
  FlutterRendererConfig config = {};
  config.type = kSoftware;
  config.software.struct_size = sizeof(config.software);
  config.software.surface_present_callback = [](void* user_data,
                                                const void* allocation,
                                                size_t row_bytes,
                                                size_t height) {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!host->view()) {
      return false;
    }
    return host->view()->PresentSoftwareBitmap(allocation, row_bytes, height);
  };
  return config;
}

// Converts a FlutterPlatformMessage to an equivalent FlutterDesktopMessage.
static FlutterDesktopMessage ConvertToDesktopMessage(
    const FlutterPlatformMessage& engine_message) {
  FlutterDesktopMessage message = {};
  message.struct_size = sizeof(message);
  message.channel = engine_message.channel;
  message.message = engine_message.message;
  message.message_size = engine_message.message_size;
  message.response_handle = engine_message.response_handle;
  return message;
}

// Converts a LanguageInfo struct to a FlutterLocale struct. |info| must outlive
// the returned value, since the returned FlutterLocale has pointers into it.
FlutterLocale CovertToFlutterLocale(const LanguageInfo& info) {
  FlutterLocale locale = {};
  locale.struct_size = sizeof(FlutterLocale);
  locale.language_code = info.language.c_str();
  if (!info.region.empty()) {
    locale.country_code = info.region.c_str();
  }
  if (!info.script.empty()) {
    locale.script_code = info.script.c_str();
  }
  return locale;
}

}  // namespace

FlutterWindowsEngine::FlutterWindowsEngine(
    const FlutterProjectBundle& project,
    std::unique_ptr<WindowsRegistry> registry)
    : project_(std::make_unique<FlutterProjectBundle>(project)),
      aot_data_(nullptr, nullptr),
      windows_registry_(std::move(registry)) {
  embedder_api_.struct_size = sizeof(FlutterEngineProcTable);
  FlutterEngineGetProcAddresses(&embedder_api_);

  task_runner_ =
      std::make_unique<TaskRunner>(
          embedder_api_.GetCurrentTime, [this](const auto* task) {
            if (!engine_) {
              FML_LOG(ERROR)
                  << "Cannot post an engine task when engine is not running.";
              return;
            }
            if (embedder_api_.RunTask(engine_, task) != kSuccess) {
              FML_LOG(ERROR) << "Failed to post an engine task.";
            }
          });

  // Set up the legacy structs backing the API handles.
  messenger_ =
      fml::RefPtr<FlutterDesktopMessenger>(new FlutterDesktopMessenger());
  messenger_->SetEngine(this);
  plugin_registrar_ = std::make_unique<FlutterDesktopPluginRegistrar>();
  plugin_registrar_->engine = this;

  messenger_wrapper_ =
      std::make_unique<BinaryMessengerImpl>(messenger_->ToRef());
  message_dispatcher_ =
      std::make_unique<IncomingMessageDispatcher>(messenger_->ToRef());
  message_dispatcher_->SetMessageCallback(
      kAccessibilityChannelName,
      [](FlutterDesktopMessengerRef messenger,
         const FlutterDesktopMessage* message, void* data) {
        FlutterWindowsEngine* engine = static_cast<FlutterWindowsEngine*>(data);
        engine->HandleAccessibilityMessage(messenger, message);
      },
      static_cast<void*>(this));

  FlutterWindowsTextureRegistrar::ResolveGlFunctions(gl_procs_);
  texture_registrar_ =
      std::make_unique<FlutterWindowsTextureRegistrar>(this, gl_procs_);
  surface_manager_ = AngleSurfaceManager::Create();
  window_proc_delegate_manager_ = std::make_unique<WindowProcDelegateManager>();

  // Set up internal channels.
  // TODO: Replace this with an embedder.h API. See
  // https://github.com/flutter/flutter/issues/71099
  settings_plugin_ = std::make_unique<SettingsPlugin>(messenger_wrapper_.get(),
                                                      task_runner_.get());
}

FlutterWindowsEngine::~FlutterWindowsEngine() {
  messenger_->SetEngine(nullptr);
  Stop();
}

void FlutterWindowsEngine::SetSwitches(
    const std::vector<std::string>& switches) {
  project_->SetSwitches(switches);
}

bool FlutterWindowsEngine::Run() {
  return Run("");
}

bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
  if (!project_->HasValidPaths()) {
    FML_LOG(ERROR) << "Missing or unresolvable paths to assets.";
    return false;
  }
  std::string assets_path_string = project_->assets_path().u8string();
  std::string icu_path_string = project_->icu_path().u8string();
  if (embedder_api_.RunsAOTCompiledDartCode()) {
    aot_data_ = project_->LoadAotData(embedder_api_);
    if (!aot_data_) {
      FML_LOG(ERROR) << "Unable to start engine without AOT data.";
      return false;
    }
  }

  // FlutterProjectArgs is expecting a full argv, so when processing it for
  // flags the first item is treated as the executable and ignored. Add a dummy
  // value so that all provided arguments are used.
  std::string executable_name = GetExecutableName();
  std::vector<const char*> argv = {executable_name.c_str()};
  std::vector<std::string> switches = project_->GetSwitches();
  std::transform(
      switches.begin(), switches.end(), std::back_inserter(argv),
      [](const std::string& arg) -> const char* { return arg.c_str(); });

  const std::vector<std::string>& entrypoint_args =
      project_->dart_entrypoint_arguments();
  std::vector<const char*> entrypoint_argv;
  std::transform(
      entrypoint_args.begin(), entrypoint_args.end(),
      std::back_inserter(entrypoint_argv),
      [](const std::string& arg) -> const char* { return arg.c_str(); });

  // Configure task runners.
  FlutterTaskRunnerDescription platform_task_runner = {};
  platform_task_runner.struct_size = sizeof(FlutterTaskRunnerDescription);
  platform_task_runner.user_data = task_runner_.get();
  platform_task_runner.runs_task_on_current_thread_callback =
      [](void* user_data) -> bool {
    return static_cast<TaskRunner*>(user_data)->RunsTasksOnCurrentThread();
  };
  platform_task_runner.post_task_callback = [](FlutterTask task,
                                               uint64_t target_time_nanos,
                                               void* user_data) -> void {
    static_cast<TaskRunner*>(user_data)->PostFlutterTask(task,
                                                         target_time_nanos);
  };
  FlutterCustomTaskRunners custom_task_runners = {};
  custom_task_runners.struct_size = sizeof(FlutterCustomTaskRunners);
  custom_task_runners.platform_task_runner = &platform_task_runner;
  custom_task_runners.thread_priority_setter =
      &WindowsPlatformThreadPrioritySetter;

  FlutterProjectArgs args = {};
  args.struct_size = sizeof(FlutterProjectArgs);
  args.shutdown_dart_vm_when_done = true;
  args.assets_path = assets_path_string.c_str();
  args.icu_data_path = icu_path_string.c_str();
  args.command_line_argc = static_cast<int>(argv.size());
  args.command_line_argv = argv.empty() ? nullptr : argv.data();

  // Fail if conflicting non-default entrypoints are specified in the method
  // argument and the project.
  //
  // TODO(cbracken): https://github.com/flutter/flutter/issues/109285
  // The entrypoint method parameter should eventually be removed from this
  // method and only the entrypoint specified in project_ should be used.
  if (!project_->dart_entrypoint().empty() && !entrypoint.empty() &&
      project_->dart_entrypoint() != entrypoint) {
    FML_LOG(ERROR) << "Conflicting entrypoints were specified in "
                      "FlutterDesktopEngineProperties.dart_entrypoint and "
                      "FlutterDesktopEngineRun(engine, entry_point). ";
    return false;
  }
  if (!entrypoint.empty()) {
    args.custom_dart_entrypoint = entrypoint.data();
  } else if (!project_->dart_entrypoint().empty()) {
    args.custom_dart_entrypoint = project_->dart_entrypoint().c_str();
  }
  args.dart_entrypoint_argc = static_cast<int>(entrypoint_argv.size());
  args.dart_entrypoint_argv =
      entrypoint_argv.empty() ? nullptr : entrypoint_argv.data();
  args.platform_message_callback =
      [](const FlutterPlatformMessage* engine_message,
         void* user_data) -> void {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    return host->HandlePlatformMessage(engine_message);
  };
  args.vsync_callback = [](void* user_data, intptr_t baton) -> void {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    host->OnVsync(baton);
  };
  args.on_pre_engine_restart_callback = [](void* user_data) {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    host->view()->OnPreEngineRestart();
  };
  args.update_semantics_node_callback = [](const FlutterSemanticsNode* node,
                                           void* user_data) {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (!node || node->id == kFlutterSemanticsNodeIdBatchEnd) {
      host->accessibility_bridge_->CommitUpdates();
      return;
    }
    host->accessibility_bridge_->AddFlutterSemanticsNodeUpdate(node);
  };
  args.update_semantics_custom_action_callback =
      [](const FlutterSemanticsCustomAction* action, void* user_data) {
        auto host = static_cast<FlutterWindowsEngine*>(user_data);
        if (!action || action->id == kFlutterSemanticsNodeIdBatchEnd) {
          host->accessibility_bridge_->CommitUpdates();
          return;
        }
        host->accessibility_bridge_->AddFlutterSemanticsCustomActionUpdate(
            action);
      };
  args.root_isolate_create_callback = [](void* user_data) {
    auto host = static_cast<FlutterWindowsEngine*>(user_data);
    if (host->root_isolate_create_callback_) {
      host->root_isolate_create_callback_();
    }
  };

  args.custom_task_runners = &custom_task_runners;

  if (aot_data_) {
    args.aot_data = aot_data_.get();
  }

  FlutterRendererConfig renderer_config = surface_manager_
                                              ? GetOpenGLRendererConfig()
                                              : GetSoftwareRendererConfig();

  auto result = embedder_api_.Run(FLUTTER_ENGINE_VERSION, &renderer_config,
                                  &args, this, &engine_);
  if (result != kSuccess || engine_ == nullptr) {
    FML_LOG(ERROR) << "Failed to start Flutter engine: error " << result;
    return false;
  }

  // Configure device frame rate displayed via devtools.
  FlutterEngineDisplay display = {};
  display.struct_size = sizeof(FlutterEngineDisplay);
  display.display_id = 0;
  display.single_display = true;
  display.refresh_rate =
      1.0 / (static_cast<double>(FrameInterval().count()) / 1000000000.0);

  std::vector<FlutterEngineDisplay> displays = {display};
  embedder_api_.NotifyDisplayUpdate(engine_,
                                    kFlutterEngineDisplaysUpdateTypeStartup,
                                    displays.data(), displays.size());

  SendSystemLocales();

  settings_plugin_->StartWatching();
  settings_plugin_->SendSettings();

  return true;
}

bool FlutterWindowsEngine::Stop() {
  if (engine_) {
    for (const auto& [callback, registrar] :
         plugin_registrar_destruction_callbacks_) {
      callback(registrar);
    }
    FlutterEngineResult result = embedder_api_.Shutdown(engine_);
    engine_ = nullptr;
    return (result == kSuccess);
  }
  return false;
}

void FlutterWindowsEngine::SetView(FlutterWindowsView* view) {
  view_ = view;
}

void FlutterWindowsEngine::OnVsync(intptr_t baton) {
  std::chrono::nanoseconds current_time =
      std::chrono::nanoseconds(embedder_api_.GetCurrentTime());
  std::chrono::nanoseconds frame_interval = FrameInterval();
  auto next = SnapToNextTick(current_time, start_time_, frame_interval);
  embedder_api_.OnVsync(engine_, baton, next.count(),
                        (next + frame_interval).count());
}

std::chrono::nanoseconds FlutterWindowsEngine::FrameInterval() {
  if (frame_interval_override_.has_value()) {
    return frame_interval_override_.value();
  }
  uint64_t interval = 16600000;

  DWM_TIMING_INFO timing_info = {};
  timing_info.cbSize = sizeof(timing_info);
  HRESULT result = DwmGetCompositionTimingInfo(NULL, &timing_info);
  if (result == S_OK && timing_info.rateRefresh.uiDenominator > 0 &&
      timing_info.rateRefresh.uiNumerator > 0) {
    interval = static_cast<double>(timing_info.rateRefresh.uiDenominator *
                                   1000000000.0) /
               static_cast<double>(timing_info.rateRefresh.uiNumerator);
  }

  return std::chrono::nanoseconds(interval);
}

// Returns the currently configured Plugin Registrar.
FlutterDesktopPluginRegistrarRef FlutterWindowsEngine::GetRegistrar() {
  return plugin_registrar_.get();
}

void FlutterWindowsEngine::AddPluginRegistrarDestructionCallback(
    FlutterDesktopOnPluginRegistrarDestroyed callback,
    FlutterDesktopPluginRegistrarRef registrar) {
  plugin_registrar_destruction_callbacks_[callback] = registrar;
}

void FlutterWindowsEngine::SendWindowMetricsEvent(
    const FlutterWindowMetricsEvent& event) {
  if (engine_) {
    embedder_api_.SendWindowMetricsEvent(engine_, &event);
  }
}

void FlutterWindowsEngine::SendPointerEvent(const FlutterPointerEvent& event) {
  if (engine_) {
    embedder_api_.SendPointerEvent(engine_, &event, 1);
  }
}

void FlutterWindowsEngine::SendKeyEvent(const FlutterKeyEvent& event,
                                        FlutterKeyEventCallback callback,
                                        void* user_data) {
  if (engine_) {
    embedder_api_.SendKeyEvent(engine_, &event, callback, user_data);
  }
}

bool FlutterWindowsEngine::SendPlatformMessage(
    const char* channel,
    const uint8_t* message,
    const size_t message_size,
    const FlutterDesktopBinaryReply reply,
    void* user_data) {
  FlutterPlatformMessageResponseHandle* response_handle = nullptr;
  if (reply != nullptr && user_data != nullptr) {
    FlutterEngineResult result =
        embedder_api_.PlatformMessageCreateResponseHandle(
            engine_, reply, user_data, &response_handle);
    if (result != kSuccess) {
      FML_LOG(ERROR) << "Failed to create response handle";
      return false;
    }
  }

  FlutterPlatformMessage platform_message = {
      sizeof(FlutterPlatformMessage),
      channel,
      message,
      message_size,
      response_handle,
  };

  FlutterEngineResult message_result =
      embedder_api_.SendPlatformMessage(engine_, &platform_message);
  if (response_handle != nullptr) {
    embedder_api_.PlatformMessageReleaseResponseHandle(engine_,
                                                       response_handle);
  }
  return message_result == kSuccess;
}

void FlutterWindowsEngine::SendPlatformMessageResponse(
    const FlutterDesktopMessageResponseHandle* handle,
    const uint8_t* data,
    size_t data_length) {
  embedder_api_.SendPlatformMessageResponse(engine_, handle, data, data_length);
}

void FlutterWindowsEngine::HandlePlatformMessage(
    const FlutterPlatformMessage* engine_message) {
  if (engine_message->struct_size != sizeof(FlutterPlatformMessage)) {
    FML_LOG(ERROR) << "Invalid message size received. Expected: "
                   << sizeof(FlutterPlatformMessage) << " but received "
                   << engine_message->struct_size;
    return;
  }

  auto message = ConvertToDesktopMessage(*engine_message);

  message_dispatcher_->HandleMessage(
      message, [this] {}, [this] {});
}

void FlutterWindowsEngine::ReloadSystemFonts() {
  embedder_api_.ReloadSystemFonts(engine_);
}

void FlutterWindowsEngine::ScheduleFrame() {
  embedder_api_.ScheduleFrame(engine_);
}

void FlutterWindowsEngine::SetNextFrameCallback(fml::closure callback) {
  next_frame_callback_ = std::move(callback);

  embedder_api_.SetNextFrameCallback(
      engine_,
      [](void* user_data) {
        // Embedder callback runs on raster thread. Switch back to platform
        // thread.
        FlutterWindowsEngine* self =
            static_cast<FlutterWindowsEngine*>(user_data);

        self->task_runner_->PostTask(std::move(self->next_frame_callback_));
      },
      this);
}

void FlutterWindowsEngine::SendSystemLocales() {
  std::vector<LanguageInfo> languages =
      GetPreferredLanguageInfo(*windows_registry_);
  std::vector<FlutterLocale> flutter_locales;
  flutter_locales.reserve(languages.size());
  for (const auto& info : languages) {
    flutter_locales.push_back(CovertToFlutterLocale(info));
  }
  // Convert the locale list to the locale pointer list that must be provided.
  std::vector<const FlutterLocale*> flutter_locale_list;
  flutter_locale_list.reserve(flutter_locales.size());
  std::transform(flutter_locales.begin(), flutter_locales.end(),
                 std::back_inserter(flutter_locale_list),
                 [](const auto& arg) -> const auto* { return &arg; });
  embedder_api_.UpdateLocales(engine_, flutter_locale_list.data(),
                              flutter_locale_list.size());
}

bool FlutterWindowsEngine::RegisterExternalTexture(int64_t texture_id) {
  return (embedder_api_.RegisterExternalTexture(engine_, texture_id) ==
          kSuccess);
}

bool FlutterWindowsEngine::UnregisterExternalTexture(int64_t texture_id) {
  return (embedder_api_.UnregisterExternalTexture(engine_, texture_id) ==
          kSuccess);
}

bool FlutterWindowsEngine::MarkExternalTextureFrameAvailable(
    int64_t texture_id) {
  return (embedder_api_.MarkExternalTextureFrameAvailable(
              engine_, texture_id) == kSuccess);
}

bool FlutterWindowsEngine::PostRasterThreadTask(fml::closure callback) {
  struct Captures {
    fml::closure callback;
  };
  auto captures = new Captures();
  captures->callback = std::move(callback);
  if (embedder_api_.PostRenderThreadTask(
          engine_,
          [](void* opaque) {
            auto captures = reinterpret_cast<Captures*>(opaque);
            captures->callback();
            delete captures;
          },
          captures) == kSuccess) {
    return true;
  }
  delete captures;
  return false;
}

bool FlutterWindowsEngine::DispatchSemanticsAction(
    uint64_t target,
    FlutterSemanticsAction action,
    fml::MallocMapping data) {
  return (embedder_api_.DispatchSemanticsAction(engine_, target, action,
                                                data.GetMapping(),
                                                data.GetSize()) == kSuccess);
}

void FlutterWindowsEngine::UpdateSemanticsEnabled(bool enabled) {
  if (engine_ && semantics_enabled_ != enabled) {
    semantics_enabled_ = enabled;
    embedder_api_.UpdateSemanticsEnabled(engine_, enabled);

    if (!semantics_enabled_ && accessibility_bridge_) {
      accessibility_bridge_.reset();
    } else if (semantics_enabled_ && !accessibility_bridge_) {
      accessibility_bridge_ = CreateAccessibilityBridge(this, view());
    }
  }
}

std::shared_ptr<AccessibilityBridge>
FlutterWindowsEngine::CreateAccessibilityBridge(FlutterWindowsEngine* engine,
                                                FlutterWindowsView* view) {
  return std::make_shared<AccessibilityBridgeWindows>(engine, view);
}

gfx::NativeViewAccessible FlutterWindowsEngine::GetNativeAccessibleFromId(
    AccessibilityNodeId id) {
  if (!accessibility_bridge_) {
    return nullptr;
  }
  std::shared_ptr<FlutterPlatformNodeDelegate> node_delegate =
      accessibility_bridge_->GetFlutterPlatformNodeDelegateFromID(id).lock();
  if (!node_delegate) {
    return nullptr;
  }
  return node_delegate->GetNativeViewAccessible();
}

std::string FlutterWindowsEngine::GetExecutableName() const {
  std::pair<bool, std::string> result = fml::paths::GetExecutablePath();
  if (result.first) {
    const std::string& executable_path = result.second;
    size_t last_separator = executable_path.find_last_of("/\\");
    if (last_separator == std::string::npos ||
        last_separator == executable_path.size() - 1) {
      return executable_path;
    }
    return executable_path.substr(last_separator + 1);
  }
  return "Flutter";
}

void FlutterWindowsEngine::UpdateAccessibilityFeatures(
    FlutterAccessibilityFeature flags) {
  embedder_api_.UpdateAccessibilityFeatures(engine_, flags);
}

void FlutterWindowsEngine::UpdateHighContrastEnabled(bool enabled) {
  high_contrast_enabled_ = enabled;
  int flags = EnabledAccessibilityFeatures();
  if (enabled) {
    flags |=
        FlutterAccessibilityFeature::kFlutterAccessibilityFeatureHighContrast;
  } else {
    flags &=
        ~FlutterAccessibilityFeature::kFlutterAccessibilityFeatureHighContrast;
  }
  UpdateAccessibilityFeatures(static_cast<FlutterAccessibilityFeature>(flags));
}

int FlutterWindowsEngine::EnabledAccessibilityFeatures() const {
  int flags = 0;
  if (high_contrast_enabled()) {
    flags |=
        FlutterAccessibilityFeature::kFlutterAccessibilityFeatureHighContrast;
  }
  // As more accessibility features are enabled for Windows,
  // the corresponding checks and flags should be added here.
  return flags;
}

void FlutterWindowsEngine::HandleAccessibilityMessage(
    FlutterDesktopMessengerRef messenger,
    const FlutterDesktopMessage* message) {
  const auto& codec = StandardMessageCodec::GetInstance();
  auto data = codec.DecodeMessage(message->message, message->message_size);
  EncodableMap map = std::get<EncodableMap>(*data);
  std::string type = std::get<std::string>(map.at(EncodableValue("type")));
  if (type.compare("announce") == 0) {
    if (semantics_enabled_) {
      EncodableMap data_map =
          std::get<EncodableMap>(map.at(EncodableValue("data")));
      std::string text =
          std::get<std::string>(data_map.at(EncodableValue("message")));
      std::wstring wide_text = fml::Utf8ToWideString(text);
      view_->AnnounceAlert(wide_text);
    }
  }
  SendPlatformMessageResponse(message->response_handle,
                              reinterpret_cast<const uint8_t*>(""), 0);
}

}  // namespace flutter