examples/platform_view/windows/runner/flutter_window.cpp

// Copyright 2014 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_window.h"

#include <WinUser.h>
#include <flutter/flutter_engine.h>
#include <flutter/method_channel.h>
#include <flutter/plugin_registrar_windows.h>
#include <flutter/standard_method_codec.h>

#include <cstdint>
#include <memory>
#include <optional>
#include <string>

#include "flutter/generated_plugin_registrant.h"

void RegisterMethodChannel(flutter::FlutterEngine* engine) {
  FlutterDesktopPluginRegistrarRef plugin_registrar_ref =
      engine->GetRegistrarForPlugin("platform_view");
  flutter::PluginRegistrarWindows* registrar =
      flutter::PluginRegistrarManager::GetInstance()
          ->GetRegistrar<flutter::PluginRegistrarWindows>(plugin_registrar_ref);
  auto channel =
      std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
          registrar->messenger(), "samples.flutter.io/platform_view",
          &flutter::StandardMethodCodec::GetInstance());
  channel->SetMethodCallHandler([](const auto& call, auto result) {
    int counter = std::get<int32_t>(*call.arguments());
    std::string msg = std::string("Pressed the button ") +
                      std::to_string(counter) + " times!";
    MessageBoxA(NULL, msg.c_str(), "Popup", MB_OK);
    result->Success(flutter::EncodableValue(counter));
  });
}

FlutterWindow::FlutterWindow(const flutter::DartProject& project)
    : project_(project) {}

FlutterWindow::~FlutterWindow() {}

bool FlutterWindow::OnCreate() {
  if (!Win32Window::OnCreate()) {
    return false;
  }

  RECT frame = GetClientArea();

  // The size here must match the window dimensions to avoid unnecessary surface
  // creation / destruction in the startup path.
  flutter_controller_ = std::make_unique<flutter::FlutterViewController>(
      frame.right - frame.left, frame.bottom - frame.top, project_);
  // Ensure that basic setup of the controller was successful.
  if (!flutter_controller_->engine() || !flutter_controller_->view()) {
    return false;
  }
  RegisterPlugins(flutter_controller_->engine());
  RegisterMethodChannel(flutter_controller_->engine());
  SetChildContent(flutter_controller_->view()->GetNativeWindow());
  return true;
}

void FlutterWindow::OnDestroy() {
  if (flutter_controller_) {
    flutter_controller_ = nullptr;
  }

  Win32Window::OnDestroy();
}

LRESULT
FlutterWindow::MessageHandler(HWND hwnd, UINT const message,
                              WPARAM const wparam,
                              LPARAM const lparam) noexcept {
  // Give Flutter, including plugins, an opportunity to handle window messages.
  if (flutter_controller_) {
    std::optional<LRESULT> result =
        flutter_controller_->HandleTopLevelWindowProc(hwnd, message, wparam,
                                                      lparam);
    if (result) {
      return *result;
    }
  }

  switch (message) {
    case WM_FONTCHANGE:
      flutter_controller_->engine()->ReloadSystemFonts();
      break;
  }

  return Win32Window::MessageHandler(hwnd, message, wparam, lparam);
}