src/embedder/main.cc

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// Entrypoint for running a Flutter app on Fuchsia.
//
// Usage: ./main <path_to_flutter_asset_bundle>

#include <lib/async-loop/cpp/loop.h>
#include <lib/async-loop/default.h>
#include <lib/syslog/global.h>
#include <string>

#include "src/embedder/engine/embedder.h"

namespace {

constexpr char kLogTag[] = "flutter_embedder";

bool FuchsiaPresentSoftwareSurface(void *user_data, const void *allocation,
                                   size_t row_bytes, size_t height) {
  // TODO(akbiggs): Present the surface to the screen.
  FX_LOGF(ERROR, kLogTag,
          "surface_present_callback (row_bytes=%lu, height=%lu)", row_bytes,
          height);
  return true;
}

void FuchsiaLogMessage(const char *tag, const char *message, void *user_data) {
  // TODO(akbiggs): This does not report the file and line number of the Dart
  // app that the log came from.
  FX_LOG(INFO, tag, message);
}

bool RunFlutterApp(const char *assets_path) {
  FlutterRendererConfig renderer_config = {
      .type = kSoftware,
      .software =
          {
              .struct_size = sizeof(FlutterSoftwareRendererConfig),
              .surface_present_callback = FuchsiaPresentSoftwareSurface,
              // TODO(akbiggs): Add callback for acquiring the software surface.
          },
  };
  FlutterProjectArgs project_args = {
      .struct_size = sizeof(FlutterProjectArgs),
      .assets_path = assets_path,
      .log_message_callback = FuchsiaLogMessage,
      .log_tag = "flutter_app",
  };

  // TODO(akbiggs): Store this FlutterEngine instance somewhere instead of
  // throwing it away.
  FlutterEngine engine;
  FlutterEngineResult result = FlutterEngineRun(
      FLUTTER_ENGINE_VERSION, &renderer_config, &project_args,
      // user_data is an arbitrary object that we can pass around to engine
      // callbacks. When we need to make those callbacks change state in our
      // embedder we should pass a pointer to a collection of our state here.
      nullptr /* user_data */, &engine);

  if (result != kSuccess || engine == nullptr) {
    FX_LOGF(ERROR, kLogTag, "Could not run the Flutter Engine. Error code: %d",
            static_cast<int>(result));
    return false;
  }

  return true;
}

} // namespace

int main(int argc, const char *argv[]) {
  if (argc != 2) {
    FX_LOG(ERROR, kLogTag, "usage: executable <path to flutter bundle>");
    return EXIT_FAILURE;
  }
  const char *assets_path = argv[1];

  async::Loop loop(&kAsyncLoopConfigAttachToCurrentThread);
  RunFlutterApp(assets_path);
  loop.Run();

  return EXIT_SUCCESS;
}