path: root/src/core.cpp

/*
 * Copyright 2022 Frederico de Oliveira Linhares
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "core.hpp"

#ifdef DEBUG
#include <sstream>
#endif

#include <yaml-cpp/yaml.h>

std::random_device random_seed;
std::mt19937 random_number_generator;

#ifdef DEBUG
static VKAPI_ATTR VkBool32 VKAPI_CALL
vk_debug_callback(
  VkDebugUtilsMessageSeverityFlagBitsEXT message_severity,
  VkDebugUtilsMessageTypeFlagsEXT message_type,
  const VkDebugUtilsMessengerCallbackDataEXT* callback_data,
  void* _obj)
{
  // Set level.
  Log::Level log_level;
  if(message_severity & VK_DEBUG_UTILS_MESSAGE_SEVERITY_VERBOSE_BIT_EXT)
    log_level = Log::Level::Trace;
  else if(message_severity & VK_DEBUG_UTILS_MESSAGE_SEVERITY_INFO_BIT_EXT)
    log_level = Log::Level::Information;
  else if(message_severity & VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT)
    log_level = Log::Level::Warning;
  else if(message_severity & VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT)
    log_level = Log::Level::Error;

  // Log message.
  cg_core.log.message(log_level, callback_data->pMessage);

  return VK_FALSE;
}
#endif

static void
load_variables(void *obj)
{
  using namespace std::chrono;

  YAML::Node root = YAML::LoadFile(cg_core.config_file);

  std::string game_name = root["name"].as<std::string>().c_str();
  cg_core.game_name = new char[game_name.size() + 1];
  strcpy(cg_core.game_name, game_name.c_str());

  cg_core.game_width = root["game"]["width"].as<int>();
  cg_core.game_height = root["game"]["height"].as<int>();
  cg_core.screen_width = root["screen"]["width"].as<int>();
  cg_core.screen_height = root["screen"]["height"].as<int>();

  cg_core.game_version_major = 0;
  cg_core.game_version_minor = 1;
  cg_core.game_version_patch = 0;

  cg_core.fps = 30;
  cg_core.max_frame_duration =
    duration<long long, std::milli>(1000 / cg_core.fps);
}

static void
unload_variables(void *obj)
{
  delete[] cg_core.game_name;
}

static void
load_sdl(void *obj)
{
  if(SDL_Init(SDL_INIT_EVERYTHING) < 0)
  {
    std::string error{"SDL could not initialize! SDL Error → "};
    error += SDL_GetError();
    throw error;
  }

  if(SDL_Vulkan_LoadLibrary(nullptr) != 0)
  {
    SDL_Quit();
    std::string error{"SDL could not initialize Vulkan! SDL_Error → "};
    error += SDL_GetError();
    throw CommandError{error};
  }
}

static void
unload_sdl(void *obj)
{
  SDL_Vulkan_UnloadLibrary();
  SDL_Quit();
}

static void
load_sdl_image(void *obj)
{
  int flags = IMG_INIT_JPG|IMG_INIT_PNG|IMG_INIT_TIF;
  if(!(IMG_Init(flags) & flags))
  {
    std::string error{"Could not initialize SDL image → "};
    error += IMG_GetError();
    throw CommandError{error};
  }
}

static void
unload_sdl_image(void *obj)
{
  IMG_Quit();
}

static void
load_sdl_mixer(void *obj)
{
  int flags = MIX_INIT_OGG|MIX_INIT_MOD;
  int initted = Mix_Init(flags);
  if(initted&flags != flags)
  {
    std::string error{"Could not initialize SDL mixer → "};
    error += Mix_GetError();
    throw CommandError{error};
  }
}

static void
unload_sdl_mixer(void *obj)
{
  while(Mix_Init(0)) Mix_Quit();
}

static void
load_sdl_open_audio(void *obj)
{
  if(Mix_OpenAudio(22050, MIX_DEFAULT_FORMAT, 2, 1024) == -1)
  {
    std::string error{"Could not open SDL mixer audio → "};
    error += Mix_GetError();
    throw CommandError{error};
  }
}

static void
unload_sdl_open_audio(void *obj)
{
  Mix_CloseAudio();
}

static void
load_window(void *obj)
{
  cg_core.window = NULL;
  cg_core.window = SDL_CreateWindow(
    cg_core.game_name, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
    cg_core.screen_width, cg_core.screen_height, SDL_WINDOW_VULKAN);
  if(cg_core.window == NULL)
  {
    std::string error{"Window could not be created! SDL_Error → "};
    error += SDL_GetError();
    throw CommandError{error};
  }
}

static void
unload_window(void *obj)
{
  SDL_DestroyWindow(cg_core.window);
}

static void
load_vk_instance(void *obj)
{
  std::vector<const char*> vk_extensions;
  std::vector<const char*> vk_required_layers_names;

  // Get extensions.
  {
    uint32_t vk_extensions_count;
    std::vector<const char*> vk_required_extensions;

    // Load debuging layers.
#ifdef DEBUG
    vk_required_extensions.push_back(VK_EXT_DEBUG_UTILS_EXTENSION_NAME);
    vk_required_layers_names.push_back("VK_LAYER_KHRONOS_validation");
#endif

    // Get extensions for SDL.
    {
      uint32_t vk_sdl_extension_count;
      std::vector<const char*> vk_sdl_extensions;

      if(!SDL_Vulkan_GetInstanceExtensions(
	   cg_core.window, &vk_sdl_extension_count, nullptr))
      {
	std::string error{
	  "Vulkan extensions could not be loaded by SDL! SDL_Error: "};
	error += SDL_GetError();
	throw CommandError{error};
      }

      vk_sdl_extensions.resize(vk_sdl_extension_count);
      SDL_Vulkan_GetInstanceExtensions(
	cg_core.window, &vk_sdl_extension_count, vk_sdl_extensions.data());

      // Combine all extensions.
      vk_extensions_count = vk_sdl_extension_count +
	vk_required_extensions.size();
      vk_extensions.resize(vk_extensions_count);
      for(auto i{0}; i < vk_sdl_extension_count; i++)
	vk_extensions[i] = vk_sdl_extensions[i];
      for(auto i{0}; i < vk_required_extensions.size(); i++)
	vk_extensions[i + vk_sdl_extension_count] = vk_required_extensions[i];
    }

#ifdef DEBUG
    cg_core.log.message(Log::Level::Trace, "Enabled VK extensions.");
    for(auto vk_extension: vk_extensions)
    {
      std::string message{"Extension name: "};
      message += vk_extension;
      cg_core.log.message(Log::Level::Trace, message);
    }
#endif
  }

  // Get available instance layers.
  {
    uint32_t vk_available_layers_count;
    std::vector<VkLayerProperties> vk_available_layers;
    std::vector<const char*> vk_available_layers_names;

    vkEnumerateInstanceLayerProperties(&vk_available_layers_count, nullptr);
    vk_available_layers.resize(vk_available_layers_count);
    vkEnumerateInstanceLayerProperties(&vk_available_layers_count,
				       vk_available_layers.data());
    vk_available_layers_names.resize(vk_available_layers_count);
#ifdef DEBUG
    cg_core.log.message(Log::Level::Trace, "Available VK instance layers.");
#endif
    for(uint32_t i = 0; i < vk_available_layers_count; i++)
    {
#ifdef DEBUG
      std::stringstream message{};
      message << "\nname: " << vk_available_layers[i].layerName << std::endl;
      message << "Description: " << vk_available_layers[i].description <<
	std::endl;
      message << "Spec version: " << vk_available_layers[i].specVersion <<
	std::endl;
      message << "Implementation version: " <<
	vk_available_layers[i].implementationVersion << std::endl;
      cg_core.log.message(Log::Level::Trace, message.str());
#endif

      vk_available_layers_names[i] = vk_available_layers[i].layerName;
    }

    // If required layers are not all available.
    if(!std::includes(
	 vk_available_layers_names.begin(), vk_available_layers_names.end(),
	 vk_required_layers_names.begin(), vk_required_layers_names.begin()))
      throw CommandError{"Some required Vulkan layers are not available."};
  }

  {
    VkApplicationInfo app_info;
    app_info.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
    app_info.pNext = nullptr;
    app_info.pApplicationName = cg_core.game_name;
    app_info.applicationVersion = VK_MAKE_VERSION(
      cg_core.game_version_major,
      cg_core.game_version_minor,
      cg_core.game_version_patch);
    app_info.pEngineName = "CandyGear";
    app_info.engineVersion = VK_MAKE_VERSION(
      CANDY_GEAR_VERSION_MAJOR,
      CANDY_GEAR_VERSION_MINOR,
      CANDY_GEAR_VERSION_PATCH);
    app_info.apiVersion = VK_API_VERSION_1_0;

    VkInstanceCreateInfo create_info;
    create_info.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
    create_info.pNext = nullptr;
    create_info.flags = 0;
    create_info.pApplicationInfo = &app_info;
    create_info.enabledExtensionCount = vk_extensions.size();
    create_info.ppEnabledExtensionNames = vk_extensions.data();
    create_info.enabledLayerCount = vk_required_layers_names.size();
    create_info.ppEnabledLayerNames = vk_required_layers_names.data();

    VkResult result =
      vkCreateInstance(&create_info, nullptr, &cg_core.vk_instance);
    if(result != VK_SUCCESS)
    {
      std::string error{""};
      switch(result)
      {
      case VK_ERROR_LAYER_NOT_PRESENT:
	error = " Layer not present.";
	break;
      case VK_ERROR_EXTENSION_NOT_PRESENT:
	error = " Extension not present.";
      }
      error = "Failed to create Vulkan instance." + error;
      throw CommandError{error};
    }
  }
}

static void
unload_vk_instance(void *obj)
{
  vkDestroyInstance(cg_core.vk_instance, nullptr);
}

static void
load_window_surface(void *obj)
{
  if(!SDL_Vulkan_CreateSurface(
       cg_core.window, cg_core.vk_instance, &cg_core.window_surface))
  {
    std::string error{"Failed to create a window surface → "};
    error += SDL_GetError();
    throw CommandError{error};
  }
}

static void
unload_window_surface(void *obj)
{
  vkDestroySurfaceKHR(cg_core.vk_instance, cg_core.window_surface, nullptr);
}

#ifdef DEBUG
static void
load_vk_debug_callback(void *obj)
{
  PFN_vkCreateDebugUtilsMessengerEXT debug_messenger;

  // A Vulkan instance extension named VK_EXT_debug_utils and a Vulkan instance
  // layer named VK_LAYER_LUNARG_standard_validation are required to enable
  // this callback. These instance extension and instance layer are loaded at
  // Instance::load_vk_instance.
  VkDebugUtilsMessengerCreateInfoEXT create_info;
  create_info.sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT;
  create_info.pNext = nullptr;
  create_info.messageSeverity =
      VK_DEBUG_UTILS_MESSAGE_SEVERITY_VERBOSE_BIT_EXT |
      VK_DEBUG_UTILS_MESSAGE_SEVERITY_INFO_BIT_EXT |
      VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT |
      VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT;
  create_info.messageType = VK_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT |
			    VK_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT |
			    VK_DEBUG_UTILS_MESSAGE_TYPE_PERFORMANCE_BIT_EXT;
  create_info.pfnUserCallback = vk_debug_callback;
  create_info.pUserData = nullptr;
  create_info.flags = 0;

  debug_messenger = (PFN_vkCreateDebugUtilsMessengerEXT)
    vkGetInstanceProcAddr(cg_core.vk_instance,
			  "vkCreateDebugUtilsMessengerEXT");

  if(debug_messenger(cg_core.vk_instance, &create_info, nullptr,
		     &cg_core.vk_callback) != VK_SUCCESS)
    CommandError{"Failed to setup debug callback for Vulkan."};
}

static void
unload_vk_debug_callback(void *obj)
{
  PFN_vkDestroyDebugUtilsMessengerEXT debug_messenger;

  debug_messenger = (PFN_vkDestroyDebugUtilsMessengerEXT)
    vkGetInstanceProcAddr(cg_core.vk_instance,
			  "vkDestroyDebugUtilsMessengerEXT");

  debug_messenger(cg_core.vk_instance, cg_core.vk_callback, nullptr);
}
#endif

static void
load_vk_devices(void *obj)
{
  uint32_t devices_count;
  std::vector<VkPhysicalDevice> vk_physical_devices;

  // Enumerate physical devices
  {
    vkEnumeratePhysicalDevices(cg_core.vk_instance, &devices_count, nullptr);
    if(devices_count < 1)
      CommandError{"Failed to find GPUs with Vulkan support."};
    vk_physical_devices.resize(devices_count);
    vkEnumeratePhysicalDevices(
      cg_core.vk_instance, &devices_count, vk_physical_devices.data());
  }

#ifdef DEBUG
  cg_core.log.message(Log::Level::Trace, "Physical devices properties");
#endif

  cg_core.vk_devices.reserve(devices_count);
  for(auto i = 0; i < devices_count; i++)
  {
    // Use swapchain on first device.
    if(i == 0)
    {
      cg_core.vk_devices.emplace_back(vk_physical_devices[i], true);
      cg_core.vk_device_with_swapchain = &cg_core.vk_devices[i];
    }
    else
      cg_core.vk_devices.emplace_back(vk_physical_devices[i], false);
  }
}

static void
unload_vk_devices(void *obj)
{
  cg_core.vk_devices.clear();
}

static void
load_vk_swapchain(void *obj)
{
  try { cg_core.vk_swapchain = new VK::Swapchain(); }
  catch(const CommandError &error)
  {
    std::string error_message{"Failed to create swapchain → "};
    error_message += error.what();
    throw CommandError{error_message};
  }
}

static void
unload_vk_swapchain(void *obj)
{
  delete cg_core.vk_swapchain;
}

static void
load_vk_render_pass_3d(void *obj)
{
  std::array<VkAttachmentDescription, 2> attachments{};
  // Color attachment.
  attachments[0].flags = 0;
  attachments[0].format = cg_core.vk_swapchain->image_format;
  attachments[0].samples = VK_SAMPLE_COUNT_1_BIT;
  attachments[0].loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
  attachments[0].storeOp = VK_ATTACHMENT_STORE_OP_STORE;
  attachments[0].stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
  attachments[0].stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
  attachments[0].initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
  attachments[0].finalLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
  // Depth attachment.
  attachments[1].flags = 0;
  attachments[1].format = VK_FORMAT_D32_SFLOAT;
  attachments[1].samples = VK_SAMPLE_COUNT_1_BIT;
  attachments[1].loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR;
  attachments[1].storeOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
  attachments[1].stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
  attachments[1].stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
  attachments[1].initialLayout = VK_IMAGE_LAYOUT_UNDEFINED;
  attachments[1].finalLayout =
      VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL;

  VkAttachmentReference color_attachment_ref{};
  color_attachment_ref.attachment = 0;
  color_attachment_ref.layout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
  VkAttachmentReference depth_attachment_ref{};
  depth_attachment_ref.attachment = 1;
  depth_attachment_ref.layout =
    VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL;

  VkSubpassDescription subpass = {};
  subpass.flags = 0;
  subpass.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
  subpass.inputAttachmentCount = 0;
  subpass.pInputAttachments = nullptr;
  subpass.colorAttachmentCount = 1;
  subpass.pColorAttachments = &color_attachment_ref;
  subpass.pResolveAttachments = nullptr;
  subpass.pDepthStencilAttachment = &depth_attachment_ref;
  subpass.preserveAttachmentCount = 0;
  subpass.pPreserveAttachments = nullptr;

  VkSubpassDependency dependency = {};
  dependency.srcSubpass = VK_SUBPASS_EXTERNAL;
  dependency.dstSubpass = 0;
  dependency.srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT |
    VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT;
  dependency.srcAccessMask = 0;
  dependency.dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT |
    VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT;
  dependency.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_READ_BIT |
    VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT |
    VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;

  VkRenderPassCreateInfo render_pass_info{};
  render_pass_info.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
  render_pass_info.pNext = nullptr;
  render_pass_info.flags = 0;
  render_pass_info.attachmentCount = attachments.size();
  render_pass_info.pAttachments = attachments.data();
  render_pass_info.subpassCount = 1;
  render_pass_info.pSubpasses = &subpass;
  render_pass_info.dependencyCount = 1;
  render_pass_info.pDependencies = &dependency;

  if(vkCreateRenderPass(
       cg_core.vk_device_with_swapchain->device, &render_pass_info,
       nullptr, &cg_core.vk_render_pass_3d) != VK_SUCCESS)
    throw CommandError{"Failed to create Vulkan Render Pass 3D."};
}

static void
unload_vk_render_pass_3d(void *obj)
{
  vkDestroyRenderPass(
    cg_core.vk_device_with_swapchain->device, cg_core.vk_render_pass_3d,
    nullptr);
}

static void
load_vk_render_pass_2d(void *obj)
{
  std::array<VkAttachmentDescription, 1> attachments{};
  // Color attachment.
  attachments[0].flags = 0;
  attachments[0].format = cg_core.vk_swapchain->image_format;
  attachments[0].samples = VK_SAMPLE_COUNT_1_BIT;
  attachments[0].loadOp = VK_ATTACHMENT_LOAD_OP_LOAD;
  attachments[0].storeOp = VK_ATTACHMENT_STORE_OP_STORE;
  attachments[0].stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE;
  attachments[0].stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE;
  attachments[0].initialLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;
  attachments[0].finalLayout = VK_IMAGE_LAYOUT_PRESENT_SRC_KHR;

  VkAttachmentReference color_attachment_ref{};
  color_attachment_ref.attachment = 0;
  color_attachment_ref.layout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL;

  VkSubpassDescription subpass{};
  subpass.flags = 0;
  subpass.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
  subpass.inputAttachmentCount = 0;
  subpass.pInputAttachments = nullptr;
  subpass.colorAttachmentCount = 1;
  subpass.pColorAttachments = &color_attachment_ref;
  subpass.pResolveAttachments = nullptr;
  subpass.pDepthStencilAttachment = nullptr;
  subpass.preserveAttachmentCount = 0;
  subpass.pPreserveAttachments = nullptr;

  VkSubpassDependency dependency{};
  dependency.srcSubpass = VK_SUBPASS_EXTERNAL;
  dependency.dstSubpass = 0;
  dependency.srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT |
    VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT;
  dependency.srcAccessMask = 0;
  dependency.dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT |
    VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT;
  dependency.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_READ_BIT |
    VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT |
    VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;

  VkRenderPassCreateInfo render_pass_info{};
  render_pass_info.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
  render_pass_info.pNext = nullptr;
  render_pass_info.flags = 0;
  render_pass_info.attachmentCount = attachments.size();
  render_pass_info.pAttachments = attachments.data();
  render_pass_info.subpassCount = 1;
  render_pass_info.pSubpasses = &subpass;
  render_pass_info.dependencyCount = 1;
  render_pass_info.pDependencies = &dependency;

  if(vkCreateRenderPass(
       cg_core.vk_device_with_swapchain->device, &render_pass_info,
       nullptr, &cg_core.vk_render_pass_2d) != VK_SUCCESS)
    throw CommandError{"Failed to create Vulkan Render Pass 2D."};
}

static void
unload_vk_render_pass_2d(void *obj)
{
  vkDestroyRenderPass(
    cg_core.vk_device_with_swapchain->device, cg_core.vk_render_pass_2d,
    nullptr);
}

static void
load_vk_graphics_pipeline_3d(void *obj)
{
  try
  {
    cg_core.vk_graphics_pipeline_3d = new VK::GraphicsPipeline3D();
  }
  catch(const CommandError &e)
  {
    throw CommandError{"Failed to create 3d graphics pipeline."};
  }
}

static void
unload_vk_graphics_pipeline_3d(void *obj)
{
  delete cg_core.vk_graphics_pipeline_3d;
}

static void
load_vk_graphics_pipeline_2d(void *obj)
{
  try
  {
    cg_core.vk_graphics_pipeline_2d = new VK::GraphicsPipeline2D();
  }
  catch(const CommandError &e)
  {
    throw CommandError{"Failed to create 2d graphics pipeline."};
  }
}

static void
unload_vk_graphics_pipeline_2d(void *obj)
{
  delete cg_core.vk_graphics_pipeline_2d;
}

static void
load_vk_renderer(void *obj)
{
  try
  {
    cg_core.vk_renderer = new VK::Renderer();
  }
  catch(const CommandError &e)
  {
    throw CommandError{"Failed to create renderer."};
  }
}

static void
unload_vk_renderer(void *obj)
{
  delete cg_core.vk_renderer;
}

static void
load_mruby(void *obj)
{
  cg_core.mrb = mrb_open();
  if (!cg_core.mrb) throw CommandError{"Failed to initialize mruby."};
}

static void
unload_mruby(void *obj)
{
  mrb_close(cg_core.mrb);
}

static void
load_mruby_symbols(void *obj)
{
  cg_core.sym_fatal = mrb_intern_cstr(cg_core.mrb, "fatal");
  cg_core.sym_error = mrb_intern_cstr(cg_core.mrb, "error");
  cg_core.sym_warning = mrb_intern_cstr(cg_core.mrb, "warning");
  cg_core.sym_information = mrb_intern_cstr(cg_core.mrb, "information");
  cg_core.sym_debug = mrb_intern_cstr(cg_core.mrb, "debug");
  cg_core.sym_trace = mrb_intern_cstr(cg_core.mrb, "trace");
}

const CommandChain cg_sCore::loader{
  {&load_variables, &unload_variables},
  {&load_sdl, &unload_sdl},
  {&load_sdl_image, &unload_sdl_image},
  {&load_sdl_mixer, &unload_sdl_mixer},
  {&load_sdl_open_audio, &unload_sdl_open_audio},
  {&load_window, &unload_window},
  {&load_vk_instance, &unload_vk_instance},
  {&load_window_surface, &unload_window_surface},
#ifdef DEBUG
  {&load_vk_debug_callback, &unload_vk_debug_callback},
#endif
  {&load_vk_devices, &unload_vk_devices},
  {&load_vk_swapchain, &unload_vk_swapchain},
  {&load_vk_render_pass_3d, &unload_vk_render_pass_3d},
  {&load_vk_render_pass_2d, &unload_vk_render_pass_2d},
  {&load_vk_graphics_pipeline_3d, &unload_vk_graphics_pipeline_3d},
  {&load_vk_graphics_pipeline_2d, &unload_vk_graphics_pipeline_2d},
  {&load_vk_renderer, &unload_vk_renderer},
  {&load_mruby, &unload_mruby},
  {&load_mruby_symbols, nullptr}
};