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 <fuchsia/fonts/cpp/fidl.h>
#include <fuchsia/scenic/scheduling/cpp/fidl.h>
#include <fuchsia/sysmem/cpp/fidl.h>
#include <fuchsia/ui/app/cpp/fidl.h>
#include <fuchsia/ui/composition/cpp/fidl.h>
#include <lib/async-loop/cpp/loop.h>
#include <lib/async-loop/default.h>
#include <lib/async/default.h>
#include <lib/fdio/directory.h>
#include <lib/fidl/cpp/binding_set.h>
#include <lib/fidl/cpp/interface_request.h>
#include <lib/sys/cpp/component_context.h>
#include <lib/syslog/global.h>
#include <lib/ui/scenic/cpp/view_identity.h>
#include <zircon/status.h>

#include <string>

#include "src/embedder/embedder_state.h"
#include "src/embedder/engine/embedder.h"
#include "src/embedder/flatland_ids.h"
#include "src/embedder/flatland_view_provider.h"
#include "src/embedder/logging.h"
#include "src/embedder/software_surface.h"
#include "src/embedder/software_surface_producer.h"

namespace embedder {
namespace {

// TODO(akbiggs): Don't hardcode this screen size, get it from
// an event instead.
constexpr int kScreenWidth = 1280;
constexpr int kScreenHeight = 800;

/// Fuchsia implementation of the Flutter Engine's |vsync_callback|.
void FuchsiaVsync(void* user_data, intptr_t baton) {
  EmbedderState* embedder = static_cast<EmbedderState*>(user_data);

  // Encourage the Engine to vsync for a 60Hz display.
  const uint64_t now_nanos = FlutterEngineGetCurrentTime();
  const uint64_t target_vsync_time = now_nanos + 16.6 * 1e6;
  FlutterEngineOnVsync(embedder->engine, baton, now_nanos, target_vsync_time);
}

/// Fuchsia implementation of the Flutter Engine's |log_message_callback|.
void FuchsiaLogMessage(const char* tag, const char* message, void* user_data) {
  FX_LOG(INFO, tag, message);
}

/// Fuchsia implementation of the Flutter Engine's software rendering
/// |surface_acquire_callback|.
bool FuchsiaAcquireSoftwareSurface(void* user_data, size_t width, size_t height,
                                   uint8_t** allocation, size_t* stride) {
  EmbedderState* embedder = static_cast<EmbedderState*>(user_data);

  if (embedder->software_surface_producer == nullptr) {
    FX_LOG(ERROR, kLogTag, "Software surface producer has not been initialized.");
  }

  if (!embedder->software_surface_producer->IsValid()) {
    // TODO(akbiggs): Maybe recover from this state?
    FX_LOGF(ERROR, kLogTag, "Software surface producer has become invalid.");
    return false;
  }

  auto surface = embedder->software_surface_producer->ProduceSurface(
      {.width = static_cast<uint32_t>(width), .height = static_cast<uint32_t>(height)});
  if (surface == nullptr) {
    FX_LOGF(ERROR, kLogTag, "Failed to acquire software surface of size (%lu, %lu).", width,
            height);
    return false;
  }

  // If we receive an unitialized surface, we need to create a Flatland
  // image and associate it with the surface.
  if (surface->GetImageId() == 0) {
    auto image_id = embedder->flatland_connection->NextContentId().value;
    const auto surface_size = surface->GetSize();

    fuchsia::math::SizeU image_size;
    image_size.width = surface_size.width;
    image_size.height = surface_size.height;

    fuchsia::ui::composition::ImageProperties image_properties;
    image_properties.set_size(image_size);

    embedder->flatland_connection->flatland()->CreateImage(
        {image_id}, surface->GetBufferCollectionImportToken(), 0, std::move(image_properties));

    surface->SetImageId(image_id);
    surface->SetReleaseImageCallback([flatland = embedder->flatland_connection.get(), image_id]() {
      flatland->flatland()->ReleaseImage({image_id});
    });
  }

  // Enqueue fences for the next present.
  embedder->flatland_connection->EnqueueAcquireFence(surface->GetAcquireFence());
  embedder->flatland_connection->EnqueueReleaseFence(surface->GetReleaseFence());

  // Preserve the surface for when we need to present it.
  embedder->software_surface = std::move(surface);
  *allocation = embedder->software_surface->GetAllocation();
  *stride = embedder->software_surface->GetBytesPerRow();

  return true;
}

/// Fuchsia implementation of the Flutter Engine's software rendering
/// |surface_present_callback|.
bool FuchsiaPresentSoftwareSurface(void* user_data, const void* allocation, size_t row_bytes,
                                   size_t height) {
  EmbedderState* embedder = static_cast<EmbedderState*>(user_data);

  if (embedder->software_surface == nullptr) {
    // We have no surface acquired to present.
    return false;
  }

  // TODO(akbiggs): Replace with composition logic matching
  // https://github.com/flutter/engine/blob/main/shell/platform/fuchsia/flutter/flatland_external_view_embedder.cc#L108.
  auto image_id = embedder->software_surface->GetImageId();
  embedder->flatland_connection->flatland()->SetContent({kRootTransformId}, {image_id});
  // TODO(akbiggs): Remove SetImageDestinationSize call once
  // https://fuchsia-review.googlesource.com/c/fuchsia/+/696647 lands.
  const auto& surface_size = embedder->software_surface->GetSize();
  fuchsia::math::SizeU image_size;
  image_size.width = surface_size.width;
  image_size.height = surface_size.height;
  embedder->flatland_connection->flatland()->SetImageDestinationSize({image_id}, image_size);

  embedder->flatland_connection->Present();

  // Submit surfaces that are being rendered so that we signal their fences.
  std::vector<std::unique_ptr<SoftwareSurface>> surfaces_to_submit;
  surfaces_to_submit.push_back(std::move(embedder->software_surface));
  embedder->software_surface = nullptr;
  embedder->software_surface_producer->SubmitSurfaces(std::move(surfaces_to_submit));

  return true;
}

/// Runs the Flutter app whose assets (including snapshots) are located
/// at |assets_path| in the component's package.
///
/// The Engine instance will be stored in |embedder| and |embedder| will be
/// the user data for all callbacks from the Flutter Engine.
bool RunFlutterApp(const char* assets_path, EmbedderState* embedder) {
  FlutterRendererConfig renderer_config = {
      .type = kSoftware,
      .software =
          {
              .struct_size = sizeof(FlutterSoftwareRendererConfig),
              .surface_present_callback = FuchsiaPresentSoftwareSurface,
              .surface_acquire_callback = FuchsiaAcquireSoftwareSurface,
          },
  };
  // Connect and set up the system font provider.
  fuchsia::fonts::ProviderSyncPtr sync_font_provider;
  zx_status_t status = embedder->component_context->svc()->Connect<fuchsia::fonts::Provider>(
      sync_font_provider.NewRequest());
  if (status != ZX_OK) {
    FX_LOGF(ERROR, embedder::kLogTag, "Failed to connect to fonts provider service: %s",
            zx_status_get_string(status));
  }
  FlutterProjectArgs project_args = {
      .struct_size = sizeof(FlutterProjectArgs),
      .assets_path = assets_path,

      .vsync_callback = FuchsiaVsync,
      .log_message_callback = FuchsiaLogMessage,

      .log_tag = "flutter_app",
      .font_initialization_data = sync_font_provider.Unbind().TakeChannel().release(),
  };

  FlutterEngineResult result = FlutterEngineRun(FLUTTER_ENGINE_VERSION, &renderer_config,
                                                &project_args, embedder, &embedder->engine);

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

  return true;
}

}  // namespace
}  // namespace embedder

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

  embedder::EmbedderState embedder = {
      // This must be initialized before calling RunFlutterApp, as
      // this hack https://github.com/flutter/engine/pull/33472 relies
      // on it.
      .component_context = sys::ComponentContext::Create(),
  };

  // Serving the component context must happen after RunFlutterApp
  // because the embedder platform has a hack that adds inspect data into the
  // Dart VM using the component context
  // (https://github.com/flutter/engine/pull/33472).
  if (!embedder::RunFlutterApp(assets_path, &embedder)) {
    return EXIT_FAILURE;
  }

  // Attaching the async loop to the current thread must happen
  // immediately after RunFlutterApp to ensure that bindings in the embedder
  // use the embedder's dispatcher to send requests instead of the Dart VM's
  // dispatcher.
  //
  // Bindings created in the embedder before this line will never get fired.
  //
  // TODO(https://fxbug.dev/75282): Remove the logic in the Dart VM that sets its
  // own default dispatcher to reduce the amount of global state.
  async::Loop loop(&kAsyncLoopConfigAttachToCurrentThread);

  // Necessary to get Flutter to render frames.
  FlutterWindowMetricsEvent window_metrics_event = {
      .struct_size = sizeof(FlutterWindowMetricsEvent),

      // TODO(akbiggs): Don't hardcode these.
      .width = embedder::kScreenWidth,
      .height = embedder::kScreenHeight,

      .pixel_ratio = 1,
      .left = 0,
      .top = 0,
      .physical_view_inset_top = 0,
      .physical_view_inset_right = 0,
      .physical_view_inset_bottom = 0,
      .physical_view_inset_left = 0,
  };
  FlutterEngineSendWindowMetricsEvent(embedder.engine, &window_metrics_event);

  // Connect to Flatland.
  fuchsia::ui::composition::FlatlandHandle flatland_handle;
  zx_status_t status =
      embedder.component_context->svc()->Connect<fuchsia::ui::composition::Flatland>(
          flatland_handle.NewRequest());
  if (status != ZX_OK) {
    FX_LOGF(ERROR, embedder::kLogTag, "Failed to connect to Flatland: %s",
            zx_status_get_string(status));
    return EXIT_FAILURE;
  }
  // TODO(akbiggs): Create this on the raster thread per FlatlandConnection's
  // documentation.
  embedder.flatland_connection = std::make_unique<embedder::FlatlandConnection>(
      // TODO(akbiggs): Pick a more appropriate debug name based on the Flutter
      // app name.
      "FlutterEmbedder" /* debug_name */, std::move(flatland_handle),
      /* on_error_callback = */
      []() {
        // TODO(akbiggs): What should we do on errors?
      },
      /* on_frame_presented_callback = */
      [](fuchsia::scenic::scheduling::FramePresentedInfo info) {
        // TODO(akbiggs): What should we do after a frame finishes presenting?
      });

  embedder::FlatlandViewProvider view_provider(embedder.flatland_connection.get());
  fidl::BindingSet<fuchsia::ui::app::ViewProvider> view_provider_bindings;
  status = embedder.component_context->outgoing()->AddPublicService<fuchsia::ui::app::ViewProvider>(
      [&view_provider,
       &view_provider_bindings](fidl::InterfaceRequest<fuchsia::ui::app::ViewProvider> request) {
        view_provider_bindings.AddBinding(&view_provider, std::move(request));
      });
  if (status != ZX_OK) {
    FX_LOGF(ERROR, embedder::kLogTag, "Failed to add ViewProvider service: %s",
            zx_status_get_string(status));
  }

  // Our run loop's dispatcher must be used to serve the component context in
  // order for requests' handlers to get called while we're looping.
  status = embedder.component_context->outgoing()->ServeFromStartupInfo(loop.dispatcher());
  if (status != ZX_OK) {
    FX_LOGF(ERROR, embedder::kLogTag, "Failed to serve component context: %s",
            zx_status_get_string(status));
  }

  embedder.software_surface_producer = std::make_unique<embedder::SoftwareSurfaceProducer>();

  // Loop until we're done.
  loop.Run();

  FX_LOG(INFO, embedder::kLogTag, "Done looping.");
  return EXIT_SUCCESS;
}