cube/cube.cpp

/*
 * Copyright (c) 2015-2019 The Khronos Group Inc.
 * Copyright (c) 2015-2019 Valve Corporation
 * Copyright (c) 2015-2019 LunarG, Inc.
 *
 * 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.
 *
 * Author: Jeremy Hayes <jeremy@lunarg.com>
 */

#if defined(VK_USE_PLATFORM_XLIB_KHR) || defined(VK_USE_PLATFORM_XCB_KHR)
#include <X11/Xutil.h>
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
#include <linux/input.h>
#include "xdg-shell-client-header.h"
#include "xdg-decoration-client-header.h"
#endif

#include <cassert>
#include <cinttypes>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <csignal>

#include <sstream>
#include <iostream>
#include <memory>

#define VULKAN_HPP_NO_EXCEPTIONS
#define VULKAN_HPP_TYPESAFE_CONVERSION
#include <vulkan/vulkan.hpp>
#include <vulkan/vk_sdk_platform.h>

#include "linmath.h"

#ifndef NDEBUG
#define VERIFY(x) assert(x)
#else
#define VERIFY(x) ((void)(x))
#endif

#define APP_SHORT_NAME "vkcubepp"

// Allow a maximum of two outstanding presentation operations.
constexpr uint32_t FRAME_LAG = 2;

#ifdef _WIN32
#define ERR_EXIT(err_msg, err_class)                                          \
    do {                                                                      \
        if (!suppress_popups) MessageBox(nullptr, err_msg, err_class, MB_OK); \
        exit(1);                                                              \
    } while (0)
#else
#define ERR_EXIT(err_msg, err_class) \
    do {                             \
        printf("%s\n", err_msg);     \
        fflush(stdout);              \
        exit(1);                     \
    } while (0)
#endif

struct texture_object {
    vk::Sampler sampler;

    vk::Image image;
    vk::Buffer buffer;
    vk::ImageLayout imageLayout{vk::ImageLayout::eUndefined};

    vk::MemoryAllocateInfo mem_alloc;
    vk::DeviceMemory mem;
    vk::ImageView view;

    int32_t tex_width{0};
    int32_t tex_height{0};
};

static char const *const tex_files[] = {"lunarg.ppm"};

static int validation_error = 0;

struct vktexcube_vs_uniform {
    // Must start with MVP
    float mvp[4][4];
    float position[12 * 3][4];
    float attr[12 * 3][4];
};

//--------------------------------------------------------------------------------------
// Mesh and VertexFormat Data
//--------------------------------------------------------------------------------------
// clang-format off
static const float g_vertex_buffer_data[] = {
    -1.0f,-1.0f,-1.0f,  // -X side
    -1.0f,-1.0f, 1.0f,
    -1.0f, 1.0f, 1.0f,
    -1.0f, 1.0f, 1.0f,
    -1.0f, 1.0f,-1.0f,
    -1.0f,-1.0f,-1.0f,

    -1.0f,-1.0f,-1.0f,  // -Z side
     1.0f, 1.0f,-1.0f,
     1.0f,-1.0f,-1.0f,
    -1.0f,-1.0f,-1.0f,
    -1.0f, 1.0f,-1.0f,
     1.0f, 1.0f,-1.0f,

    -1.0f,-1.0f,-1.0f,  // -Y side
     1.0f,-1.0f,-1.0f,
     1.0f,-1.0f, 1.0f,
    -1.0f,-1.0f,-1.0f,
     1.0f,-1.0f, 1.0f,
    -1.0f,-1.0f, 1.0f,

    -1.0f, 1.0f,-1.0f,  // +Y side
    -1.0f, 1.0f, 1.0f,
     1.0f, 1.0f, 1.0f,
    -1.0f, 1.0f,-1.0f,
     1.0f, 1.0f, 1.0f,
     1.0f, 1.0f,-1.0f,

     1.0f, 1.0f,-1.0f,  // +X side
     1.0f, 1.0f, 1.0f,
     1.0f,-1.0f, 1.0f,
     1.0f,-1.0f, 1.0f,
     1.0f,-1.0f,-1.0f,
     1.0f, 1.0f,-1.0f,

    -1.0f, 1.0f, 1.0f,  // +Z side
    -1.0f,-1.0f, 1.0f,
     1.0f, 1.0f, 1.0f,
    -1.0f,-1.0f, 1.0f,
     1.0f,-1.0f, 1.0f,
     1.0f, 1.0f, 1.0f,
};

static const float g_uv_buffer_data[] = {
    0.0f, 1.0f,  // -X side
    1.0f, 1.0f,
    1.0f, 0.0f,
    1.0f, 0.0f,
    0.0f, 0.0f,
    0.0f, 1.0f,

    1.0f, 1.0f,  // -Z side
    0.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 1.0f,
    1.0f, 0.0f,
    0.0f, 0.0f,

    1.0f, 0.0f,  // -Y side
    1.0f, 1.0f,
    0.0f, 1.0f,
    1.0f, 0.0f,
    0.0f, 1.0f,
    0.0f, 0.0f,

    1.0f, 0.0f,  // +Y side
    0.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 1.0f,

    1.0f, 0.0f,  // +X side
    0.0f, 0.0f,
    0.0f, 1.0f,
    0.0f, 1.0f,
    1.0f, 1.0f,
    1.0f, 0.0f,

    0.0f, 0.0f,  // +Z side
    0.0f, 1.0f,
    1.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 1.0f,
    1.0f, 0.0f,
};
// clang-format on

struct SwapchainImageResources {
    vk::Image image;
    vk::CommandBuffer cmd;
    vk::CommandBuffer graphics_to_present_cmd;
    vk::ImageView view;
    vk::Buffer uniform_buffer;
    vk::DeviceMemory uniform_memory;
    void *uniform_memory_ptr = nullptr;
    vk::Framebuffer framebuffer;
    vk::DescriptorSet descriptor_set;
};

struct Demo {
    void build_image_ownership_cmd(const SwapchainImageResources &swapchain_image_resource);
    vk::Bool32 check_layers(const std::vector<const char *> &check_names, const std::vector<vk::LayerProperties> &layers);
    void cleanup();
    void destroy_swapchain_related_resources();
    void create_device();
    void destroy_texture(texture_object &tex_objs);
    void draw();
    void draw_build_cmd(const SwapchainImageResources &swapchain_image_resource);
    void prepare_init_cmd();
    void flush_init_cmd();
    void init(int argc, char **argv);
    void init_connection();
    void init_vk();
    void init_vk_swapchain();
    void prepare();
    void prepare_buffers();
    void prepare_cube_data_buffers();
    void prepare_depth();
    void prepare_descriptor_layout();
    void prepare_descriptor_pool();
    void prepare_descriptor_set();
    void prepare_framebuffers();
    vk::ShaderModule prepare_shader_module(const uint32_t *code, size_t size);
    vk::ShaderModule prepare_vs();
    vk::ShaderModule prepare_fs();
    void prepare_pipeline();
    void prepare_render_pass();
    void prepare_texture_image(const char *filename, texture_object &tex_obj, vk::ImageTiling tiling, vk::ImageUsageFlags usage,
                               vk::MemoryPropertyFlags required_props);
    void prepare_texture_buffer(const char *filename, texture_object &tex_obj);
    void prepare_textures();

    void resize();
    void create_surface();
    void set_image_layout(vk::Image image, vk::ImageAspectFlags aspectMask, vk::ImageLayout oldLayout, vk::ImageLayout newLayout,
                          vk::AccessFlags srcAccessMask, vk::PipelineStageFlags src_stages, vk::PipelineStageFlags dest_stages);
    void update_data_buffer();
    bool loadTexture(const char *filename, uint8_t *rgba_data, vk::SubresourceLayout &layout, int32_t &width, int32_t &height);
    bool memory_type_from_properties(uint32_t typeBits, vk::MemoryPropertyFlags requirements_mask, uint32_t &typeIndex);
    vk::SurfaceFormatKHR pick_surface_format(const std::vector<vk::SurfaceFormatKHR> &surface_formats);

#if defined(VK_USE_PLATFORM_WIN32_KHR)
    void run();
    void create_window();
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
    void create_xlib_window();
    void handle_xlib_event(const XEvent *event);
    void run_xlib();
#elif defined(VK_USE_PLATFORM_XCB_KHR)
    void handle_xcb_event(const xcb_generic_event_t *event);
    void run_xcb();
    void create_xcb_window();
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    void run();
    void create_window();
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
    void handle_directfb_event(const DFBInputEvent *event);
    void run_directfb();
    void create_directfb_window();
#elif defined(VK_USE_PLATFORM_METAL_EXT)
    void run();
#elif defined(VK_USE_PLATFORM_DISPLAY_KHR)
    vk::Result create_display_surface();
    void run_display();
#endif

    std::string name = "vkcubepp";  // Name to put on the window/icon
#if defined(VK_USE_PLATFORM_WIN32_KHR)
    HINSTANCE connection = nullptr;  // hInstance - Windows Instance
    HWND window = nullptr;           // hWnd - window handle
    POINT minsize = {0, 0};          // minimum window size
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
    Window xlib_window = 0;
    Atom xlib_wm_delete_window = 0;
    Display *display = nullptr;
#elif defined(VK_USE_PLATFORM_XCB_KHR)
    xcb_window_t xcb_window = 0;
    xcb_screen_t *screen = nullptr;
    xcb_connection_t *connection = nullptr;
    xcb_intern_atom_reply_t *atom_wm_delete_window = nullptr;
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    wl_display *display = nullptr;
    wl_registry *registry = nullptr;
    wl_compositor *compositor = nullptr;
    wl_surface *window = nullptr;
    xdg_wm_base *wm_base = nullptr;
    zxdg_decoration_manager_v1 *xdg_decoration_mgr = nullptr;
    zxdg_toplevel_decoration_v1 *toplevel_decoration = nullptr;
    xdg_surface *window_surface = nullptr;
    bool xdg_surface_has_been_configured = false;
    xdg_toplevel *window_toplevel = nullptr;
    wl_seat *seat = nullptr;
    wl_pointer *pointer = nullptr;
    wl_keyboard *keyboard = nullptr;
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
    IDirectFB *dfb = nullptr;
    IDirectFBSurface *window = nullptr;
    IDirectFBEventBuffer *event_buffer = nullptr;
#elif defined(VK_USE_PLATFORM_METAL_EXT)
    void *caMetalLayer;
#endif

    vk::SurfaceKHR surface;
    bool prepared = false;
    bool use_staging_buffer = false;
    bool use_xlib = false;
    bool separate_present_queue = false;
    int32_t gpu_number = 0;

    vk::Instance inst;
    vk::PhysicalDevice gpu;
    vk::Device device;
    vk::Queue graphics_queue;
    vk::Queue present_queue;
    uint32_t graphics_queue_family_index = 0;
    uint32_t present_queue_family_index = 0;
    std::array<vk::Semaphore, FRAME_LAG> image_acquired_semaphores;
    std::array<vk::Semaphore, FRAME_LAG> draw_complete_semaphores;
    std::array<vk::Semaphore, FRAME_LAG> image_ownership_semaphores;
    vk::PhysicalDeviceProperties gpu_props;
    std::vector<vk::QueueFamilyProperties> queue_props;
    vk::PhysicalDeviceMemoryProperties memory_properties;

    std::vector<const char *> enabled_instance_extensions;
    std::vector<const char *> enabled_layers;
    std::vector<const char *> enabled_device_extensions;

    int32_t width = 0;
    int32_t height = 0;
    vk::Format format;
    vk::ColorSpaceKHR color_space;

    vk::SwapchainKHR swapchain;
    std::vector<SwapchainImageResources> swapchain_image_resources;
    vk::PresentModeKHR presentMode = vk::PresentModeKHR::eFifo;
    std::array<vk::Fence, FRAME_LAG> fences;
    uint32_t frame_index = 0;

    vk::CommandPool cmd_pool;
    vk::CommandPool present_cmd_pool;

    struct {
        vk::Format format;
        vk::Image image;
        vk::MemoryAllocateInfo mem_alloc;
        vk::DeviceMemory mem;
        vk::ImageView view;
    } depth;

    static int32_t const texture_count = 1;
    std::array<texture_object, texture_count> textures;
    texture_object staging_texture;

    struct {
        vk::Buffer buf;
        vk::MemoryAllocateInfo mem_alloc;
        vk::DeviceMemory mem;
        vk::DescriptorBufferInfo buffer_info;
    } uniform_data;

    vk::CommandBuffer cmd;  // Buffer for initialization commands
    vk::PipelineLayout pipeline_layout;
    vk::DescriptorSetLayout desc_layout;
    vk::PipelineCache pipelineCache;
    vk::RenderPass render_pass;
    vk::Pipeline pipeline;

    mat4x4 projection_matrix = {};
    mat4x4 view_matrix = {};
    mat4x4 model_matrix = {};

    float spin_angle = 0.0f;
    float spin_increment = 0.0f;
    bool pause = false;

    vk::ShaderModule vert_shader_module;
    vk::ShaderModule frag_shader_module;

    vk::DescriptorPool desc_pool;
    vk::DescriptorSet desc_set;

    std::vector<vk::Framebuffer> framebuffers;

    bool quit = false;
    uint32_t curFrame = 0;
    uint32_t frameCount = 0;
    bool validate = false;
    bool use_break = false;
    bool suppress_popups = false;
    bool force_errors = false;

    uint32_t current_buffer = 0;
};

#ifdef _WIN32
// MS-Windows event handling function:
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
#endif

#if defined(VK_USE_PLATFORM_WAYLAND_KHR)
static void pointer_handle_enter(void *data, struct wl_pointer *pointer, uint32_t serial, struct wl_surface *surface, wl_fixed_t sx,
                                 wl_fixed_t sy) {}

static void pointer_handle_leave(void *data, struct wl_pointer *pointer, uint32_t serial, struct wl_surface *surface) {}

static void pointer_handle_motion(void *data, struct wl_pointer *pointer, uint32_t time, wl_fixed_t sx, wl_fixed_t sy) {}

static void pointer_handle_button(void *data, struct wl_pointer *wl_pointer, uint32_t serial, uint32_t time, uint32_t button,
                                  uint32_t state) {
    Demo *demo = (Demo *)data;
    if (button == BTN_LEFT && state == WL_POINTER_BUTTON_STATE_PRESSED) {
        xdg_toplevel_move(demo->window_toplevel, demo->seat, serial);
    }
}

static void pointer_handle_axis(void *data, struct wl_pointer *wl_pointer, uint32_t time, uint32_t axis, wl_fixed_t value) {}

static const struct wl_pointer_listener pointer_listener = {
    pointer_handle_enter, pointer_handle_leave, pointer_handle_motion, pointer_handle_button, pointer_handle_axis,
};

static void keyboard_handle_keymap(void *data, struct wl_keyboard *keyboard, uint32_t format, int fd, uint32_t size) {}

static void keyboard_handle_enter(void *data, struct wl_keyboard *keyboard, uint32_t serial, struct wl_surface *surface,
                                  struct wl_array *keys) {}

static void keyboard_handle_leave(void *data, struct wl_keyboard *keyboard, uint32_t serial, struct wl_surface *surface) {}

static void keyboard_handle_key(void *data, struct wl_keyboard *keyboard, uint32_t serial, uint32_t time, uint32_t key,
                                uint32_t state) {
    if (state != WL_KEYBOARD_KEY_STATE_RELEASED) return;
    Demo *demo = (Demo *)data;
    switch (key) {
        case KEY_ESC:  // Escape
            demo->quit = true;
            break;
        case KEY_LEFT:  // left arrow key
            demo->spin_angle -= demo->spin_increment;
            break;
        case KEY_RIGHT:  // right arrow key
            demo->spin_angle += demo->spin_increment;
            break;
        case KEY_SPACE:  // space bar
            demo->pause = !demo->pause;
            break;
    }
}

static void keyboard_handle_modifiers(void *data, wl_keyboard *keyboard, uint32_t serial, uint32_t mods_depressed,
                                      uint32_t mods_latched, uint32_t mods_locked, uint32_t group) {}

static const struct wl_keyboard_listener keyboard_listener = {
    keyboard_handle_keymap, keyboard_handle_enter, keyboard_handle_leave, keyboard_handle_key, keyboard_handle_modifiers,
};

static void seat_handle_capabilities(void *data, wl_seat *seat, uint32_t caps) {
    // Subscribe to pointer events
    Demo *demo = (Demo *)data;
    if ((caps & WL_SEAT_CAPABILITY_POINTER) && !demo->pointer) {
        demo->pointer = wl_seat_get_pointer(seat);
        wl_pointer_add_listener(demo->pointer, &pointer_listener, demo);
    } else if (!(caps & WL_SEAT_CAPABILITY_POINTER) && demo->pointer) {
        wl_pointer_destroy(demo->pointer);
        demo->pointer = nullptr;
    }
    // Subscribe to keyboard events
    if (caps & WL_SEAT_CAPABILITY_KEYBOARD) {
        demo->keyboard = wl_seat_get_keyboard(seat);
        wl_keyboard_add_listener(demo->keyboard, &keyboard_listener, demo);
    } else if (!(caps & WL_SEAT_CAPABILITY_KEYBOARD)) {
        wl_keyboard_destroy(demo->keyboard);
        demo->keyboard = nullptr;
    }
}

static const wl_seat_listener seat_listener = {
    seat_handle_capabilities,
};

static void wm_base_ping(void *data, xdg_wm_base *xdg_wm_base, uint32_t serial) { xdg_wm_base_pong(xdg_wm_base, serial); }

static const struct xdg_wm_base_listener wm_base_listener = {wm_base_ping};

static void registry_handle_global(void *data, wl_registry *registry, uint32_t id, const char *interface, uint32_t version) {
    Demo *demo = (Demo *)data;
    // pickup wayland objects when they appear
    if (strcmp(interface, wl_compositor_interface.name) == 0) {
        demo->compositor = (wl_compositor *)wl_registry_bind(registry, id, &wl_compositor_interface, 1);
    } else if (strcmp(interface, xdg_wm_base_interface.name) == 0) {
        demo->wm_base = (xdg_wm_base *)wl_registry_bind(registry, id, &xdg_wm_base_interface, 1);
        xdg_wm_base_add_listener(demo->wm_base, &wm_base_listener, nullptr);
    } else if (strcmp(interface, wl_seat_interface.name) == 0) {
        demo->seat = (wl_seat *)wl_registry_bind(registry, id, &wl_seat_interface, 1);
        wl_seat_add_listener(demo->seat, &seat_listener, demo);
    } else if (strcmp(interface, zxdg_decoration_manager_v1_interface.name) == 0) {
        demo->xdg_decoration_mgr =
            (zxdg_decoration_manager_v1 *)wl_registry_bind(registry, id, &zxdg_decoration_manager_v1_interface, 1);
    }
}

static void registry_handle_global_remove(void *data, wl_registry *registry, uint32_t name) {}

static const wl_registry_listener registry_listener = {registry_handle_global, registry_handle_global_remove};
#endif

void Demo::build_image_ownership_cmd(const SwapchainImageResources &swapchain_image_resource) {
    auto result = swapchain_image_resource.graphics_to_present_cmd.begin(
        vk::CommandBufferBeginInfo().setFlags(vk::CommandBufferUsageFlagBits::eSimultaneousUse));
    VERIFY(result == vk::Result::eSuccess);

    auto const image_ownership_barrier =
        vk::ImageMemoryBarrier()
            .setSrcAccessMask(vk::AccessFlags())
            .setDstAccessMask(vk::AccessFlags())
            .setOldLayout(vk::ImageLayout::ePresentSrcKHR)
            .setNewLayout(vk::ImageLayout::ePresentSrcKHR)
            .setSrcQueueFamilyIndex(graphics_queue_family_index)
            .setDstQueueFamilyIndex(present_queue_family_index)
            .setImage(swapchain_image_resource.image)
            .setSubresourceRange(vk::ImageSubresourceRange(vk::ImageAspectFlagBits::eColor, 0, 1, 0, 1));

    swapchain_image_resource.graphics_to_present_cmd.pipelineBarrier(vk::PipelineStageFlagBits::eBottomOfPipe,
                                                                     vk::PipelineStageFlagBits::eBottomOfPipe,
                                                                     vk::DependencyFlagBits(), {}, {}, image_ownership_barrier);

    result = swapchain_image_resource.graphics_to_present_cmd.end();
    VERIFY(result == vk::Result::eSuccess);
}

vk::Bool32 Demo::check_layers(const std::vector<const char *> &check_names, const std::vector<vk::LayerProperties> &layers) {
    for (const auto &name : check_names) {
        vk::Bool32 found = VK_FALSE;
        for (const auto &layer : layers) {
            if (!strcmp(name, layer.layerName)) {
                found = VK_TRUE;
                break;
            }
        }
        if (!found) {
            fprintf(stderr, "Cannot find layer: %s\n", name);
            return 0;
        }
    }
    return VK_TRUE;
}

void Demo::cleanup() {
    prepared = false;
    auto result = device.waitIdle();
    VERIFY(result == vk::Result::eSuccess);

    destroy_swapchain_related_resources();
    // Wait for fences from present operations
    for (uint32_t i = 0; i < FRAME_LAG; i++) {
        device.destroyFence(fences[i]);
        device.destroySemaphore(image_acquired_semaphores[i]);
        device.destroySemaphore(draw_complete_semaphores[i]);
        if (separate_present_queue) {
            device.destroySemaphore(image_ownership_semaphores[i]);
        }
    }

    device.destroySwapchainKHR(swapchain);

    device.destroy();
    inst.destroySurfaceKHR(surface);

#if defined(VK_USE_PLATFORM_XLIB_KHR)
    XDestroyWindow(display, xlib_window);
    XCloseDisplay(display);
#elif defined(VK_USE_PLATFORM_XCB_KHR)
    xcb_destroy_window(connection, xcb_window);
    xcb_disconnect(connection);
    free(atom_wm_delete_window);
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    wl_keyboard_destroy(keyboard);
    wl_pointer_destroy(pointer);
    wl_seat_destroy(seat);
    xdg_toplevel_destroy(window_toplevel);
    xdg_surface_destroy(window_surface);
    wl_surface_destroy(window);
    xdg_wm_base_destroy(wm_base);
    if (xdg_decoration_mgr) {
        zxdg_toplevel_decoration_v1_destroy(toplevel_decoration);
        zxdg_decoration_manager_v1_destroy(xdg_decoration_mgr);
    }
    wl_compositor_destroy(compositor);
    wl_registry_destroy(registry);
    wl_display_disconnect(display);
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
    event_buffer->Release(event_buffer);
    window->Release(window);
    dfb->Release(dfb);
#endif

    inst.destroy();
}

void Demo::create_device() {
    float priorities = 0.0;

    std::vector<vk::DeviceQueueCreateInfo> queues;
    queues.push_back(vk::DeviceQueueCreateInfo().setQueueFamilyIndex(graphics_queue_family_index).setQueuePriorities(priorities));

    if (separate_present_queue) {
        queues.push_back(
            vk::DeviceQueueCreateInfo().setQueueFamilyIndex(present_queue_family_index).setQueuePriorities(priorities));
    }

    auto deviceInfo = vk::DeviceCreateInfo().setQueueCreateInfos(queues).setPEnabledExtensionNames(enabled_device_extensions);
    auto device_return = gpu.createDevice(deviceInfo);
    VERIFY(device_return.result == vk::Result::eSuccess);
    device = device_return.value;
}

void Demo::destroy_texture(texture_object &tex_objs) {
    // clean up staging resources
    device.freeMemory(tex_objs.mem);
    if (tex_objs.image) device.destroyImage(tex_objs.image);
    if (tex_objs.buffer) device.destroyBuffer(tex_objs.buffer);
}

void Demo::draw() {
    // Ensure no more than FRAME_LAG renderings are outstanding
    device.waitForFences(fences[frame_index], VK_TRUE, UINT64_MAX);
    device.resetFences({fences[frame_index]});

    vk::Result acquire_result;
    do {
        acquire_result =
            device.acquireNextImageKHR(swapchain, UINT64_MAX, image_acquired_semaphores[frame_index], vk::Fence(), &current_buffer);
        if (acquire_result == vk::Result::eErrorOutOfDateKHR) {
            // demo->swapchain is out of date (e.g. the window was resized) and
            // must be recreated:
            resize();
        } else if (acquire_result == vk::Result::eSuboptimalKHR) {
            // swapchain is not as optimal as it could be, but the platform's
            // presentation engine will still present the image correctly.
            break;
        } else if (acquire_result == vk::Result::eErrorSurfaceLostKHR) {
            inst.destroySurfaceKHR(surface);
            create_surface();
            resize();
        } else {
            VERIFY(acquire_result == vk::Result::eSuccess);
        }
    } while (acquire_result != vk::Result::eSuccess);

    update_data_buffer();

    // Wait for the image acquired semaphore to be signaled to ensure
    // that the image won't be rendered to until the presentation
    // engine has fully released ownership to the application, and it is
    // okay to render to the image.
    vk::PipelineStageFlags const pipe_stage_flags = vk::PipelineStageFlagBits::eColorAttachmentOutput;

    auto submit_result = graphics_queue.submit(vk::SubmitInfo()
                                                   .setWaitDstStageMask(pipe_stage_flags)
                                                   .setWaitSemaphores(image_acquired_semaphores[frame_index])
                                                   .setCommandBuffers(swapchain_image_resources[current_buffer].cmd)
                                                   .setSignalSemaphores(draw_complete_semaphores[frame_index]),
                                               fences[frame_index]);
    VERIFY(submit_result == vk::Result::eSuccess);

    if (separate_present_queue) {
        // If we are using separate queues, change image ownership to the
        // present queue before presenting, waiting for the draw complete
        // semaphore and signalling the ownership released semaphore when
        // finished
        auto change_owner_result =
            present_queue.submit(vk::SubmitInfo()
                                     .setWaitDstStageMask(pipe_stage_flags)
                                     .setWaitSemaphores(draw_complete_semaphores[frame_index])
                                     .setCommandBuffers(swapchain_image_resources[current_buffer].graphics_to_present_cmd)
                                     .setSignalSemaphores(image_ownership_semaphores[frame_index]));
        VERIFY(change_owner_result == vk::Result::eSuccess);
    }

    // If we are using separate queues we have to wait for image ownership,
    // otherwise wait for draw complete
    auto present_result =
        present_queue.presentKHR(vk::PresentInfoKHR()
                                     .setWaitSemaphores(separate_present_queue ? image_ownership_semaphores[frame_index]
                                                                               : draw_complete_semaphores[frame_index])
                                     .setSwapchains(swapchain)
                                     .setImageIndices(current_buffer));
    frame_index += 1;
    frame_index %= FRAME_LAG;
    if (present_result == vk::Result::eErrorOutOfDateKHR) {
        // swapchain is out of date (e.g. the window was resized) and
        // must be recreated:
        resize();
    } else if (present_result == vk::Result::eSuboptimalKHR) {
        // SUBOPTIMAL could be due to resize
        vk::SurfaceCapabilitiesKHR surfCapabilities;
        auto caps_result = gpu.getSurfaceCapabilitiesKHR(surface, &surfCapabilities);
        VERIFY(caps_result == vk::Result::eSuccess);
        if (surfCapabilities.currentExtent.width != static_cast<uint32_t>(width) ||
            surfCapabilities.currentExtent.height != static_cast<uint32_t>(height)) {
            resize();
        }
    } else if (present_result == vk::Result::eErrorSurfaceLostKHR) {
        inst.destroySurfaceKHR(surface);
        create_surface();
        resize();
    } else {
        VERIFY(present_result == vk::Result::eSuccess);
    }
}

void Demo::draw_build_cmd(const SwapchainImageResources &swapchain_image_resource) {
    const auto commandBuffer = swapchain_image_resource.cmd;
    vk::ClearValue const clearValues[2] = {vk::ClearColorValue(std::array<float, 4>({{0.2f, 0.2f, 0.2f, 0.2f}})),
                                           vk::ClearDepthStencilValue(1.0f, 0u)};

    auto result = commandBuffer.begin(vk::CommandBufferBeginInfo().setFlags(vk::CommandBufferUsageFlagBits::eSimultaneousUse));
    VERIFY(result == vk::Result::eSuccess);

    commandBuffer.beginRenderPass(vk::RenderPassBeginInfo()
                                      .setRenderPass(render_pass)
                                      .setFramebuffer(swapchain_image_resource.framebuffer)
                                      .setRenderArea(vk::Rect2D(vk::Offset2D(0, 0), vk::Extent2D(static_cast<uint32_t>(width),
                                                                                                 static_cast<uint32_t>(height))))
                                      .setClearValueCount(2)
                                      .setPClearValues(clearValues),
                                  vk::SubpassContents::eInline);

    commandBuffer.bindPipeline(vk::PipelineBindPoint::eGraphics, pipeline);
    commandBuffer.bindDescriptorSets(vk::PipelineBindPoint::eGraphics, pipeline_layout, 0, swapchain_image_resource.descriptor_set,
                                     {});
    float viewport_dimension;
    float viewport_x = 0.0f;
    float viewport_y = 0.0f;
    if (width < height) {
        viewport_dimension = static_cast<float>(width);
        viewport_y = (height - width) / 2.0f;
    } else {
        viewport_dimension = static_cast<float>(height);
        viewport_x = (width - height) / 2.0f;
    }

    commandBuffer.setViewport(0, vk::Viewport()
                                     .setX(viewport_x)
                                     .setY(viewport_y)
                                     .setWidth(viewport_dimension)
                                     .setHeight(viewport_dimension)
                                     .setMinDepth(0.0f)
                                     .setMaxDepth(1.0f));

    commandBuffer.setScissor(0, vk::Rect2D(vk::Offset2D(0, 0), vk::Extent2D(width, height)));
    commandBuffer.draw(12 * 3, 1, 0, 0);
    // Note that ending the renderpass changes the image's layout from
    // COLOR_ATTACHMENT_OPTIMAL to PRESENT_SRC_KHR
    commandBuffer.endRenderPass();

    if (separate_present_queue) {
        // We have to transfer ownership from the graphics queue family to
        // the
        // present queue family to be able to present.  Note that we don't
        // have
        // to transfer from present queue family back to graphics queue
        // family at
        // the start of the next frame because we don't care about the
        // image's
        // contents at that point.
        commandBuffer.pipelineBarrier(
            vk::PipelineStageFlagBits::eBottomOfPipe, vk::PipelineStageFlagBits::eBottomOfPipe, vk::DependencyFlagBits(), {}, {},
            vk::ImageMemoryBarrier()
                .setSrcAccessMask(vk::AccessFlags())
                .setDstAccessMask(vk::AccessFlags())
                .setOldLayout(vk::ImageLayout::ePresentSrcKHR)
                .setNewLayout(vk::ImageLayout::ePresentSrcKHR)
                .setSrcQueueFamilyIndex(graphics_queue_family_index)
                .setDstQueueFamilyIndex(present_queue_family_index)
                .setImage(swapchain_image_resource.image)
                .setSubresourceRange(vk::ImageSubresourceRange(vk::ImageAspectFlagBits::eColor, 0, 1, 0, 1)));
    }

    result = commandBuffer.end();
    VERIFY(result == vk::Result::eSuccess);
}

void Demo::prepare_init_cmd() {
    auto cmd_pool_return = device.createCommandPool(vk::CommandPoolCreateInfo().setQueueFamilyIndex(graphics_queue_family_index));
    VERIFY(cmd_pool_return.result == vk::Result::eSuccess);
    cmd_pool = cmd_pool_return.value;

    auto cmd_return = device.allocateCommandBuffers(vk::CommandBufferAllocateInfo()
                                                        .setCommandPool(cmd_pool)
                                                        .setLevel(vk::CommandBufferLevel::ePrimary)
                                                        .setCommandBufferCount(1));
    VERIFY(cmd_return.result == vk::Result::eSuccess);
    cmd = cmd_return.value[0];

    auto result = cmd.begin(vk::CommandBufferBeginInfo());
    VERIFY(result == vk::Result::eSuccess);
}

void Demo::flush_init_cmd() {
    // TODO: hmm.
    // This function could get called twice if the texture uses a staging
    // buffer
    // In that case the second call should be ignored
    if (!cmd) {
        return;
    }

    auto result = cmd.end();
    VERIFY(result == vk::Result::eSuccess);

    auto fenceInfo = vk::FenceCreateInfo();
    if (force_errors) {
        // Remove sType to intentionally force validation layer errors.
        fenceInfo.sType = vk::StructureType::eRenderPassBeginInfo;
    }
    auto fence_return = device.createFence(fenceInfo);
    VERIFY(fence_return.result == vk::Result::eSuccess);
    auto fence = fence_return.value;

    result = graphics_queue.submit(vk::SubmitInfo().setCommandBuffers(cmd), fence);
    VERIFY(result == vk::Result::eSuccess);

    result = device.waitForFences(fence, VK_TRUE, UINT64_MAX);
    VERIFY(result == vk::Result::eSuccess);

    device.freeCommandBuffers(cmd_pool, cmd);
    device.destroyFence(fence);

    cmd = vk::CommandBuffer();
}

void Demo::init(int argc, char **argv) {
    vec3 eye = {0.0f, 3.0f, 5.0f};
    vec3 origin = {0, 0, 0};
    vec3 up = {0.0f, 1.0f, 0.0};

    presentMode = vk::PresentModeKHR::eFifo;
    frameCount = UINT32_MAX;
    width = 500;
    height = 500;
    use_xlib = false;
    /* Autodetect suitable / best GPU by default */
    gpu_number = -1;

    for (int i = 1; i < argc; i++) {
        if (strcmp(argv[i], "--use_staging") == 0) {
            use_staging_buffer = true;
            continue;
        }
        if ((strcmp(argv[i], "--present_mode") == 0) && (i < argc - 1)) {
            presentMode = (vk::PresentModeKHR)atoi(argv[i + 1]);
            i++;
            continue;
        }
        if (strcmp(argv[i], "--break") == 0) {
            use_break = true;
            continue;
        }
        if (strcmp(argv[i], "--validate") == 0) {
            validate = true;
            continue;
        }
        if (strcmp(argv[i], "--xlib") == 0) {
            fprintf(stderr, "--xlib is deprecated and no longer does anything");
            continue;
        }
        if (strcmp(argv[i], "--c") == 0 && frameCount == UINT32_MAX && i < argc - 1 &&
            sscanf(argv[i + 1], "%" SCNu32, &frameCount) == 1) {
            i++;
            continue;
        }
        if (strcmp(argv[i], "--width") == 0 && i < argc - 1 && sscanf(argv[i + 1], "%" SCNi32, &width) == 1 && width > 0) {
            i++;
            continue;
        }
        if (strcmp(argv[i], "--height") == 0 && i < argc - 1 && sscanf(argv[i + 1], "%" SCNi32, &height) == 1 && height > 0) {
            i++;
            continue;
        }
        if (strcmp(argv[i], "--suppress_popups") == 0) {
            suppress_popups = true;
            continue;
        }
        if ((strcmp(argv[i], "--gpu_number") == 0) && (i < argc - 1)) {
            gpu_number = atoi(argv[i + 1]);
            assert(gpu_number >= 0);
            i++;
            continue;
        }
        if (strcmp(argv[i], "--force_errors") == 0) {
            force_errors = true;
            continue;
        }
        std::stringstream usage;
        usage << "Usage:\n  " << APP_SHORT_NAME << "\t[--use_staging] [--validate]\n"
              << "\t[--break] [--c <framecount>] [--suppress_popups]\n"
              << "\t[--gpu_number <index of physical device>]\n"
              << "\t[--present_mode <present mode enum>]\n"
              << "\t[--width <width>] [--height <height>]\n"
              << "\t[--force_errors]\n"
              << "\t<present_mode_enum>\n"
              << "\t\tVK_PRESENT_MODE_IMMEDIATE_KHR = " << VK_PRESENT_MODE_IMMEDIATE_KHR << "\n"
              << "\t\tVK_PRESENT_MODE_MAILBOX_KHR = " << VK_PRESENT_MODE_MAILBOX_KHR << "\n"
              << "\t\tVK_PRESENT_MODE_FIFO_KHR = " << VK_PRESENT_MODE_FIFO_KHR << "\n"
              << "\t\tVK_PRESENT_MODE_FIFO_RELAXED_KHR = " << VK_PRESENT_MODE_FIFO_RELAXED_KHR << "\n";

#if defined(_WIN32)
        if (!suppress_popups) MessageBox(nullptr, usage.str().c_str(), "Usage Error", MB_OK);
#else
        std::cerr << usage.str();
        std::cerr.flush();
#endif
        exit(1);
    }

    if (!use_xlib) {
        init_connection();
    }

    init_vk();

    spin_angle = 4.0f;
    spin_increment = 0.2f;
    pause = false;

    mat4x4_perspective(projection_matrix, static_cast<float>(degreesToRadians(45.0f)), 1.0f, 0.1f, 100.0f);
    mat4x4_look_at(view_matrix, eye, origin, up);
    mat4x4_identity(model_matrix);

    projection_matrix[1][1] *= -1;  // Flip projection matrix from GL to Vulkan orientation.
}

void Demo::init_connection() {
#if defined(VK_USE_PLATFORM_XCB_KHR)
    const xcb_setup_t *setup;
    xcb_screen_iterator_t iter;
    int scr;

    const char *display_envar = getenv("DISPLAY");
    if (display_envar == nullptr || display_envar[0] == '\0') {
        printf("Environment variable DISPLAY requires a valid value.\nExiting ...\n");
        fflush(stdout);
        exit(1);
    }

    connection = xcb_connect(nullptr, &scr);
    if (xcb_connection_has_error(connection) > 0) {
        printf("Cannot connect to XCB.\nExiting ...\n");
        fflush(stdout);
        exit(1);
    }

    setup = xcb_get_setup(connection);
    iter = xcb_setup_roots_iterator(setup);
    while (scr-- > 0) xcb_screen_next(&iter);

    screen = iter.data;
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    display = wl_display_connect(nullptr);

    if (display == nullptr) {
        printf("Cannot connect to wayland.\nExiting ...\n");
        fflush(stdout);
        exit(1);
    }

    registry = wl_display_get_registry(display);
    wl_registry_add_listener(registry, &registry_listener, this);
    wl_display_dispatch(display);
#endif
}
#if defined(VK_USE_PLATFORM_DISPLAY_KHR)
int find_display_gpu(int gpu_number, const std::vector<vk::PhysicalDevice> &physical_devices) {
    uint32_t display_count = 0;
    int gpu_return = gpu_number;
    if (gpu_number >= 0) {
        auto display_props_return = physical_devices[gpu_number].getDisplayPropertiesKHR();
        VERIFY(display_props_return.result == vk::Result::eSuccess);
    } else {
        for (uint32_t i = 0; i < physical_devices.size(); i++) {
            auto display_props_return = physical_devices[i].getDisplayPropertiesKHR();
            VERIFY(display_props_return.result == vk::Result::eSuccess);
            if (display_props_return.value.size() > 0) {
                gpu_return = i;
                break;
            }
        }
    }
    if (display_count > 0)
        return gpu_return;
    else
        return -1;
}
#endif
void Demo::init_vk() {
    std::vector<char const *> instance_validation_layers = {"VK_LAYER_KHRONOS_validation"};

    // Look for validation layers
    vk::Bool32 validation_found = VK_FALSE;
    if (validate) {
        auto layers = vk::enumerateInstanceLayerProperties();
        VERIFY(layers.result == vk::Result::eSuccess);

        validation_found = check_layers(instance_validation_layers, layers.value);
        if (validation_found) {
            enabled_layers.push_back("VK_LAYER_KHRONOS_validation");
        }

        else {
            ERR_EXIT(
                "vkEnumerateInstanceLayerProperties failed to find required validation layer.\n\n"
                "Please look at the Getting Started guide for additional information.\n",
                "vkCreateInstance Failure");
        }
    }

    /* Look for instance extensions */
    vk::Bool32 surfaceExtFound = VK_FALSE;
    vk::Bool32 platformSurfaceExtFound = VK_FALSE;

    auto instance_extensions_return = vk::enumerateInstanceExtensionProperties();
    VERIFY(instance_extensions_return.result == vk::Result::eSuccess);

    for (const auto &extension : instance_extensions_return.value) {
        if (!strcmp(VK_KHR_GET_PHYSICAL_DEVICE_PROPERTIES_2_EXTENSION_NAME, extension.extensionName)) {
            enabled_instance_extensions.push_back(VK_KHR_GET_PHYSICAL_DEVICE_PROPERTIES_2_EXTENSION_NAME);
        } else if (!strcmp(VK_KHR_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            surfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_KHR_SURFACE_EXTENSION_NAME);
        }
#if defined(VK_USE_PLATFORM_WIN32_KHR)
        else if (!strcmp(VK_KHR_WIN32_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_KHR_WIN32_SURFACE_EXTENSION_NAME);
        }
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
        else if (!strcmp(VK_KHR_XLIB_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_KHR_XLIB_SURFACE_EXTENSION_NAME);
        }
#elif defined(VK_USE_PLATFORM_XCB_KHR)
        else if (!strcmp(VK_KHR_XCB_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_KHR_XCB_SURFACE_EXTENSION_NAME);
        }
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
        else if (!strcmp(VK_KHR_WAYLAND_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_KHR_WAYLAND_SURFACE_EXTENSION_NAME);
        }
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
        else if (!strcmp(VK_EXT_DIRECTFB_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_EXT_DIRECTFB_SURFACE_EXTENSION_NAME);
        }
#elif defined(VK_USE_PLATFORM_DISPLAY_KHR)
        else if (!strcmp(VK_KHR_DISPLAY_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_KHR_DISPLAY_EXTENSION_NAME);
        }
#elif defined(VK_USE_PLATFORM_METAL_EXT)
        else if (!strcmp(VK_EXT_METAL_SURFACE_EXTENSION_NAME, extension.extensionName)) {
            platformSurfaceExtFound = 1;
            enabled_instance_extensions.push_back(VK_EXT_METAL_SURFACE_EXTENSION_NAME);
        }
#endif
    }

    if (!surfaceExtFound) {
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_KHR_SURFACE_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
    }

    if (!platformSurfaceExtFound) {
#if defined(VK_USE_PLATFORM_WIN32_KHR)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_KHR_WIN32_SURFACE_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
#elif defined(VK_USE_PLATFORM_XCB_KHR)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_KHR_XCB_SURFACE_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_KHR_WAYLAND_SURFACE_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_KHR_XLIB_SURFACE_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_EXT_DIRECTFB_SURFACE_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
#elif defined(VK_USE_PLATFORM_DISPLAY_KHR)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_KHR_DISPLAY_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
#elif defined(VK_USE_PLATFORM_METAL_EXT)
        ERR_EXIT("vkEnumerateInstanceExtensionProperties failed to find the " VK_EXT_METAL_SURFACE_EXTENSION_NAME
                 " extension.\n\nDo you have a compatible "
                 "Vulkan installable client driver (ICD) installed?\nPlease "
                 "look at the Getting Started guide for additional "
                 "information.\n",
                 "vkCreateInstance Failure");
#endif
    }
    auto const app = vk::ApplicationInfo()
                         .setPApplicationName(APP_SHORT_NAME)
                         .setApplicationVersion(0)
                         .setPEngineName(APP_SHORT_NAME)
                         .setEngineVersion(0);
    auto const inst_info = vk::InstanceCreateInfo()
                               .setPApplicationInfo(&app)
                               .setPEnabledLayerNames(enabled_layers)
                               .setPEnabledExtensionNames(enabled_instance_extensions);

    auto instance_result = vk::createInstance(inst_info);
    if (instance_result.result == vk::Result::eErrorIncompatibleDriver) {
        ERR_EXIT(
            "Cannot find a compatible Vulkan installable client driver (ICD).\n\n"
            "Please look at the Getting Started guide for additional information.\n",
            "vkCreateInstance Failure");
    } else if (instance_result.result == vk::Result::eErrorExtensionNotPresent) {
        ERR_EXIT(
            "Cannot find a specified extension library.\n"
            "Make sure your layers path is set appropriately.\n",
            "vkCreateInstance Failure");
    } else if (instance_result.result != vk::Result::eSuccess) {
        ERR_EXIT(
            "vkCreateInstance failed.\n\n"
            "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
            "Please look at the Getting Started guide for additional information.\n",
            "vkCreateInstance Failure");
    }
    inst = instance_result.value;

    auto physical_device_return = inst.enumeratePhysicalDevices();
    VERIFY(physical_device_return.result == vk::Result::eSuccess);
    auto physical_devices = physical_device_return.value;

    if (physical_devices.size() <= 0) {
        ERR_EXIT(
            "vkEnumeratePhysicalDevices reported zero accessible devices.\n\n"
            "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
            "Please look at the Getting Started guide for additional information.\n",
            "vkEnumeratePhysicalDevices Failure");
    }

    if (gpu_number >= 0 && !(static_cast<uint32_t>(gpu_number) < physical_devices.size())) {
        fprintf(stderr, "GPU %d specified is not present, GPU count = %zu\n", gpu_number, physical_devices.size());
        ERR_EXIT("Specified GPU number is not present", "User Error");
    }
#if defined(VK_USE_PLATFORM_DISPLAY_KHR)
    gpu_number = find_display_gpu(gpu_number, physical_devices);
    if (gpu_number < 0) {
        printf("Cannot find any display!\n");
        fflush(stdout);
        exit(1);
    }
#else
    /* Try to auto select most suitable device */
    if (gpu_number == -1) {
        constexpr uint32_t device_type_count = static_cast<uint32_t>(vk::PhysicalDeviceType::eCpu) + 1;
        std::array<uint32_t, device_type_count> count_device_type{};

        for (uint32_t i = 0; i < physical_devices.size(); i++) {
            const auto physicalDeviceProperties = physical_devices[i].getProperties();
            assert(physicalDeviceProperties.deviceType <= vk::PhysicalDeviceType::eCpu);
            count_device_type[static_cast<int>(physicalDeviceProperties.deviceType)]++;
        }

        std::array<vk::PhysicalDeviceType, device_type_count> const device_type_preference = {
            vk::PhysicalDeviceType::eDiscreteGpu, vk::PhysicalDeviceType::eIntegratedGpu, vk::PhysicalDeviceType::eVirtualGpu,
            vk::PhysicalDeviceType::eCpu, vk::PhysicalDeviceType::eOther};

        vk::PhysicalDeviceType search_for_device_type = vk::PhysicalDeviceType::eDiscreteGpu;
        for (uint32_t i = 0; i < sizeof(device_type_preference) / sizeof(vk::PhysicalDeviceType); i++) {
            if (count_device_type[static_cast<int>(device_type_preference[i])]) {
                search_for_device_type = device_type_preference[i];
                break;
            }
        }

        for (uint32_t i = 0; i < physical_devices.size(); i++) {
            const auto physicalDeviceProperties = physical_devices[i].getProperties();
            if (physicalDeviceProperties.deviceType == search_for_device_type) {
                gpu_number = i;
                break;
            }
        }
    }
#endif
    assert(gpu_number >= 0);
    gpu = physical_devices[gpu_number];
    {
        auto physicalDeviceProperties = gpu.getProperties();
        fprintf(stderr, "Selected GPU %d: %s, type: %s\n", gpu_number, physicalDeviceProperties.deviceName.data(),
                to_string(physicalDeviceProperties.deviceType).c_str());
    }

    /* Look for device extensions */
    vk::Bool32 swapchainExtFound = VK_FALSE;

    auto device_extension_return = gpu.enumerateDeviceExtensionProperties();
    VERIFY(device_extension_return.result == vk::Result::eSuccess);

    for (const auto &extension : device_extension_return.value) {
        if (!strcmp(VK_KHR_SWAPCHAIN_EXTENSION_NAME, extension.extensionName)) {
            swapchainExtFound = 1;
            enabled_device_extensions.push_back(VK_KHR_SWAPCHAIN_EXTENSION_NAME);
        } else if (!strcmp("VK_KHR_portability_subset", extension.extensionName)) {
            enabled_device_extensions.push_back("VK_KHR_portability_subset");
        }
    }

    if (!swapchainExtFound) {
        ERR_EXIT("vkEnumerateDeviceExtensionProperties failed to find the " VK_KHR_SWAPCHAIN_EXTENSION_NAME
                 " extension.\n\n"
                 "Do you have a compatible Vulkan installable client driver (ICD) installed?\n"
                 "Please look at the Getting Started guide for additional information.\n",
                 "vkCreateInstance Failure");
    }

    gpu.getProperties(&gpu_props);

    /* Call with nullptr data to get count */
    queue_props = gpu.getQueueFamilyProperties();
    assert(queue_props.size() >= 1);

    // Query fine-grained feature support for this device.
    //  If app has specific feature requirements it should check supported
    //  features based on this query
    vk::PhysicalDeviceFeatures physDevFeatures;
    gpu.getFeatures(&physDevFeatures);
}

void Demo::create_surface() {
// Create a WSI surface for the window:
#if defined(VK_USE_PLATFORM_WIN32_KHR)
    {
        auto const createInfo = vk::Win32SurfaceCreateInfoKHR().setHinstance(connection).setHwnd(window);

        auto result = inst.createWin32SurfaceKHR(&createInfo, nullptr, &surface);
        VERIFY(result == vk::Result::eSuccess);
    }
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    {
        auto const createInfo = vk::WaylandSurfaceCreateInfoKHR().setDisplay(display).setSurface(window);

        auto result = inst.createWaylandSurfaceKHR(&createInfo, nullptr, &surface);
        VERIFY(result == vk::Result::eSuccess);
    }
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
    {
        auto const createInfo = vk::XlibSurfaceCreateInfoKHR().setDpy(display).setWindow(xlib_window);

        auto result = inst.createXlibSurfaceKHR(&createInfo, nullptr, &surface);
        VERIFY(result == vk::Result::eSuccess);
    }
#elif defined(VK_USE_PLATFORM_XCB_KHR)
    {
        auto const createInfo = vk::XcbSurfaceCreateInfoKHR().setConnection(connection).setWindow(xcb_window);

        auto result = inst.createXcbSurfaceKHR(&createInfo, nullptr, &surface);
        VERIFY(result == vk::Result::eSuccess);
    }
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
    {
        auto const createInfo = vk::DirectFBSurfaceCreateInfoEXT().setDfb(dfb).setSurface(window);

        auto result = inst.createDirectFBSurfaceEXT(&createInfo, nullptr, &surface);
        VERIFY(result == vk::Result::eSuccess);
    }
#elif defined(VK_USE_PLATFORM_METAL_EXT)
    {
        auto const createInfo = vk::MetalSurfaceCreateInfoEXT().setPLayer(static_cast<CAMetalLayer *>(caMetalLayer));

        auto result = inst.createMetalSurfaceEXT(&createInfo, nullptr, &surface);
        VERIFY(result == vk::Result::eSuccess);
    }
#elif defined(VK_USE_PLATFORM_DISPLAY_KHR)
    {
        auto result = create_display_surface();
        VERIFY(result == vk::Result::eSuccess);
    }
#endif
}

void Demo::init_vk_swapchain() {
    create_surface();
    // Iterate over each queue to learn whether it supports presenting:
    std::vector<vk::Bool32> supportsPresent;
    for (uint32_t i = 0; i < static_cast<uint32_t>(queue_props.size()); i++) {
        auto supports = gpu.getSurfaceSupportKHR(i, surface);
        VERIFY(supports.result == vk::Result::eSuccess);
        supportsPresent.push_back(supports.value);
    }

    uint32_t graphicsQueueFamilyIndex = UINT32_MAX;
    uint32_t presentQueueFamilyIndex = UINT32_MAX;
    for (uint32_t i = 0; i < static_cast<uint32_t>(queue_props.size()); i++) {
        if (queue_props[i].queueFlags & vk::QueueFlagBits::eGraphics) {
            if (graphicsQueueFamilyIndex == UINT32_MAX) {
                graphicsQueueFamilyIndex = i;
            }

            if (supportsPresent[i] == VK_TRUE) {
                graphicsQueueFamilyIndex = i;
                presentQueueFamilyIndex = i;
                break;
            }
        }
    }

    if (presentQueueFamilyIndex == UINT32_MAX) {
        // If didn't find a queue that supports both graphics and present,
        // then
        // find a separate present queue.
        for (uint32_t i = 0; i < queue_props.size(); ++i) {
            if (supportsPresent[i] == VK_TRUE) {
                presentQueueFamilyIndex = i;
                break;
            }
        }
    }

    // Generate error if could not find both a graphics and a present queue
    if (graphicsQueueFamilyIndex == UINT32_MAX || presentQueueFamilyIndex == UINT32_MAX) {
        ERR_EXIT("Could not find both graphics and present queues\n", "Swapchain Initialization Failure");
    }

    graphics_queue_family_index = graphicsQueueFamilyIndex;
    present_queue_family_index = presentQueueFamilyIndex;
    separate_present_queue = (graphics_queue_family_index != present_queue_family_index);

    create_device();

    graphics_queue = device.getQueue(graphics_queue_family_index, 0);
    if (!separate_present_queue) {
        present_queue = graphics_queue;
    } else {
        present_queue = device.getQueue(present_queue_family_index, 0);
    }

    // Get the list of VkFormat's that are supported:
    auto surface_formats_return = gpu.getSurfaceFormatsKHR(surface);
    VERIFY(surface_formats_return.result == vk::Result::eSuccess);

    vk::SurfaceFormatKHR surfaceFormat = pick_surface_format(surface_formats_return.value);
    format = surfaceFormat.format;
    color_space = surfaceFormat.colorSpace;

    quit = false;
    curFrame = 0;

    // Create semaphores to synchronize acquiring presentable buffers before
    // rendering and waiting for drawing to be complete before presenting
    auto const semaphoreCreateInfo = vk::SemaphoreCreateInfo();

    // Create fences that we can use to throttle if we get too far
    // ahead of the image presents
    auto const fence_ci = vk::FenceCreateInfo().setFlags(vk::FenceCreateFlagBits::eSignaled);
    for (uint32_t i = 0; i < FRAME_LAG; i++) {
        vk::Result result = device.createFence(&fence_ci, nullptr, &fences[i]);
        VERIFY(result == vk::Result::eSuccess);

        result = device.createSemaphore(&semaphoreCreateInfo, nullptr, &image_acquired_semaphores[i]);
        VERIFY(result == vk::Result::eSuccess);

        result = device.createSemaphore(&semaphoreCreateInfo, nullptr, &draw_complete_semaphores[i]);
        VERIFY(result == vk::Result::eSuccess);

        if (separate_present_queue) {
            result = device.createSemaphore(&semaphoreCreateInfo, nullptr, &image_ownership_semaphores[i]);
            VERIFY(result == vk::Result::eSuccess);
        }
    }
    frame_index = 0;

    // Get Memory information and properties
    memory_properties = gpu.getMemoryProperties();
}

void Demo::prepare() {
    prepare_init_cmd();

    prepare_buffers();
    prepare_depth();
    prepare_textures();
    prepare_cube_data_buffers();

    prepare_descriptor_layout();
    prepare_render_pass();
    prepare_pipeline();

    for (auto &swapchain_image_resource : swapchain_image_resources) {
        auto alloc_return = device.allocateCommandBuffers(vk::CommandBufferAllocateInfo()
                                                              .setCommandPool(cmd_pool)
                                                              .setLevel(vk::CommandBufferLevel::ePrimary)
                                                              .setCommandBufferCount(1));
        VERIFY(alloc_return.result == vk::Result::eSuccess);
        swapchain_image_resource.cmd = alloc_return.value[0];
    }

    if (separate_present_queue) {
        auto present_cmd_pool_return =
            device.createCommandPool(vk::CommandPoolCreateInfo().setQueueFamilyIndex(present_queue_family_index));
        VERIFY(present_cmd_pool_return.result == vk::Result::eSuccess);
        present_cmd_pool = present_cmd_pool_return.value;

        for (auto &swapchain_image_resource : swapchain_image_resources) {
            auto alloc_cmd_return = device.allocateCommandBuffers(vk::CommandBufferAllocateInfo()
                                                                      .setCommandPool(present_cmd_pool)
                                                                      .setLevel(vk::CommandBufferLevel::ePrimary)
                                                                      .setCommandBufferCount(1));
            VERIFY(alloc_cmd_return.result == vk::Result::eSuccess);
            swapchain_image_resource.graphics_to_present_cmd = alloc_cmd_return.value[0];
            build_image_ownership_cmd(swapchain_image_resource);
        }
    }

    prepare_descriptor_pool();
    prepare_descriptor_set();

    prepare_framebuffers();

    for (const auto &swapchain_image_resource : swapchain_image_resources) {
        draw_build_cmd(swapchain_image_resource);
    }

    /*
     * Prepare functions above may generate pipeline commands
     * that need to be flushed before beginning the render loop.
     */
    flush_init_cmd();
    if (staging_texture.buffer) {
        destroy_texture(staging_texture);
    }

    current_buffer = 0;
    prepared = true;
}

void Demo::prepare_buffers() {
    vk::SwapchainKHR oldSwapchain = swapchain;

    // Check the surface capabilities and formats
    auto surface_capabilities_return = gpu.getSurfaceCapabilitiesKHR(surface);
    VERIFY(surface_capabilities_return.result == vk::Result::eSuccess);
    auto surfCapabilities = surface_capabilities_return.value;

    auto present_modes_return = gpu.getSurfacePresentModesKHR(surface);
    VERIFY(present_modes_return.result == vk::Result::eSuccess);
    auto present_modes = present_modes_return.value;

    vk::Extent2D swapchainExtent;
    // width and height are either both -1, or both not -1.
    if (surfCapabilities.currentExtent.width == static_cast<uint32_t>(-1)) {
        // If the surface size is undefined, the size is set to
        // the size of the images requested.
        swapchainExtent.width = width;
        swapchainExtent.height = height;
    } else {
        // If the surface size is defined, the swap chain size must match
        swapchainExtent = surfCapabilities.currentExtent;
        width = surfCapabilities.currentExtent.width;
        height = surfCapabilities.currentExtent.height;
    }

    // The FIFO present mode is guaranteed by the spec to be supported
    // and to have no tearing.  It's a great default present mode to use.
    vk::PresentModeKHR swapchainPresentMode = vk::PresentModeKHR::eFifo;

    //  There are times when you may wish to use another present mode.  The
    //  following code shows how to select them, and the comments provide some
    //  reasons you may wish to use them.
    //
    // It should be noted that Vulkan 1.0 doesn't provide a method for
    // synchronizing rendering with the presentation engine's display.  There
    // is a method provided for throttling rendering with the display, but
    // there are some presentation engines for which this method will not work.
    // If an application doesn't throttle its rendering, and if it renders much
    // faster than the refresh rate of the display, this can waste power on
    // mobile devices.  That is because power is being spent rendering images
    // that may never be seen.

    // VK_PRESENT_MODE_IMMEDIATE_KHR is for applications that don't care
    // about
    // tearing, or have some way of synchronizing their rendering with the
    // display.
    // VK_PRESENT_MODE_MAILBOX_KHR may be useful for applications that
    // generally render a new presentable image every refresh cycle, but are
    // occasionally early.  In this case, the application wants the new
    // image
    // to be displayed instead of the previously-queued-for-presentation
    // image
    // that has not yet been displayed.
    // VK_PRESENT_MODE_FIFO_RELAXED_KHR is for applications that generally
    // render a new presentable image every refresh cycle, but are
    // occasionally
    // late.  In this case (perhaps because of stuttering/latency concerns),
    // the application wants the late image to be immediately displayed,
    // even
    // though that may mean some tearing.

    if (presentMode != swapchainPresentMode) {
        for (const auto &mode : present_modes) {
            if (mode == presentMode) {
                swapchainPresentMode = mode;
                break;
            }
        }
    }

    if (swapchainPresentMode != presentMode) {
        ERR_EXIT("Present mode specified is not supported\n", "Present mode unsupported");
    }

    // Determine the number of VkImages to use in the swap chain.
    // Application desires to acquire 3 images at a time for triple
    // buffering
    uint32_t desiredNumOfSwapchainImages = 3;
    if (desiredNumOfSwapchainImages < surfCapabilities.minImageCount) {
        desiredNumOfSwapchainImages = surfCapabilities.minImageCount;
    }

    // If maxImageCount is 0, we can ask for as many images as we want,
    // otherwise
    // we're limited to maxImageCount
    if ((surfCapabilities.maxImageCount > 0) && (desiredNumOfSwapchainImages > surfCapabilities.maxImageCount)) {
        // Application must settle for fewer images than desired:
        desiredNumOfSwapchainImages = surfCapabilities.maxImageCount;
    }

    vk::SurfaceTransformFlagBitsKHR preTransform;
    if (surfCapabilities.supportedTransforms & vk::SurfaceTransformFlagBitsKHR::eIdentity) {
        preTransform = vk::SurfaceTransformFlagBitsKHR::eIdentity;
    } else {
        preTransform = surfCapabilities.currentTransform;
    }

    // Find a supported composite alpha mode - one of these is guaranteed to be set
    vk::CompositeAlphaFlagBitsKHR compositeAlpha = vk::CompositeAlphaFlagBitsKHR::eOpaque;
    std::array<vk::CompositeAlphaFlagBitsKHR, 4> compositeAlphaFlags = {
        vk::CompositeAlphaFlagBitsKHR::eOpaque,
        vk::CompositeAlphaFlagBitsKHR::ePreMultiplied,
        vk::CompositeAlphaFlagBitsKHR::ePostMultiplied,
        vk::CompositeAlphaFlagBitsKHR::eInherit,
    };
    for (const auto &compositeAlphaFlag : compositeAlphaFlags) {
        if (surfCapabilities.supportedCompositeAlpha & compositeAlphaFlag) {
            compositeAlpha = compositeAlphaFlag;
            break;
        }
    }

    auto swapchain_return = device.createSwapchainKHR(vk::SwapchainCreateInfoKHR()
                                                          .setSurface(surface)
                                                          .setMinImageCount(desiredNumOfSwapchainImages)
                                                          .setImageFormat(format)
                                                          .setImageColorSpace(color_space)
                                                          .setImageExtent({swapchainExtent.width, swapchainExtent.height})
                                                          .setImageArrayLayers(1)
                                                          .setImageUsage(vk::ImageUsageFlagBits::eColorAttachment)
                                                          .setImageSharingMode(vk::SharingMode::eExclusive)
                                                          .setPreTransform(preTransform)
                                                          .setCompositeAlpha(compositeAlpha)
                                                          .setPresentMode(swapchainPresentMode)
                                                          .setClipped(true)
                                                          .setOldSwapchain(oldSwapchain));
    VERIFY(swapchain_return.result == vk::Result::eSuccess);
    swapchain = swapchain_return.value;

    // If we just re-created an existing swapchain, we should destroy the
    // old
    // swapchain at this point.
    // Note: destroying the swapchain also cleans up all its associated
    // presentable images once the platform is done with them.
    if (oldSwapchain) {
        device.destroySwapchainKHR(oldSwapchain);
    }

    auto swapchain_images_return = device.getSwapchainImagesKHR(swapchain);
    VERIFY(swapchain_images_return.result == vk::Result::eSuccess);
    swapchain_image_resources.resize(swapchain_images_return.value.size());

    for (uint32_t i = 0; i < swapchain_image_resources.size(); ++i) {
        auto color_image_view = vk::ImageViewCreateInfo()
                                    .setViewType(vk::ImageViewType::e2D)
                                    .setFormat(format)
                                    .setSubresourceRange(vk::ImageSubresourceRange(vk::ImageAspectFlagBits::eColor, 0, 1, 0, 1));

        swapchain_image_resources[i].image = swapchain_images_return.value[i];

        color_image_view.image = swapchain_image_resources[i].image;

        auto image_view_return = device.createImageView(color_image_view);
        VERIFY(image_view_return.result == vk::Result::eSuccess);
        swapchain_image_resources[i].view = image_view_return.value;
    }
}

void Demo::prepare_cube_data_buffers() {
    mat4x4 VP;
    mat4x4_mul(VP, projection_matrix, view_matrix);

    mat4x4 MVP;
    mat4x4_mul(MVP, VP, model_matrix);

    vktexcube_vs_uniform data;
    memcpy(data.mvp, MVP, sizeof(MVP));
    //    dumpMatrix("MVP", MVP)

    for (int32_t i = 0; i < 12 * 3; i++) {
        data.position[i][0] = g_vertex_buffer_data[i * 3];
        data.position[i][1] = g_vertex_buffer_data[i * 3 + 1];
        data.position[i][2] = g_vertex_buffer_data[i * 3 + 2];
        data.position[i][3] = 1.0f;
        data.attr[i][0] = g_uv_buffer_data[2 * i];
        data.attr[i][1] = g_uv_buffer_data[2 * i + 1];
        data.attr[i][2] = 0;
        data.attr[i][3] = 0;
    }

    auto const buf_info = vk::BufferCreateInfo().setSize(sizeof(data)).setUsage(vk::BufferUsageFlagBits::eUniformBuffer);

    for (auto &swapchain_image_resource : swapchain_image_resources) {
        auto result = device.createBuffer(&buf_info, nullptr, &swapchain_image_resource.uniform_buffer);
        VERIFY(result == vk::Result::eSuccess);

        vk::MemoryRequirements mem_reqs;
        device.getBufferMemoryRequirements(swapchain_image_resource.uniform_buffer, &mem_reqs);

        auto mem_alloc = vk::MemoryAllocateInfo().setAllocationSize(mem_reqs.size).setMemoryTypeIndex(0);

        bool const pass = memory_type_from_properties(
            mem_reqs.memoryTypeBits, vk::MemoryPropertyFlagBits::eHostVisible | vk::MemoryPropertyFlagBits::eHostCoherent,
            mem_alloc.memoryTypeIndex);
        VERIFY(pass);

        result = device.allocateMemory(&mem_alloc, nullptr, &swapchain_image_resource.uniform_memory);
        VERIFY(result == vk::Result::eSuccess);

        result = device.mapMemory(swapchain_image_resource.uniform_memory, 0, VK_WHOLE_SIZE, vk::MemoryMapFlags(),
                                  &swapchain_image_resource.uniform_memory_ptr);
        VERIFY(result == vk::Result::eSuccess);

        memcpy(swapchain_image_resource.uniform_memory_ptr, &data, sizeof data);

        result = device.bindBufferMemory(swapchain_image_resource.uniform_buffer, swapchain_image_resource.uniform_memory, 0);
        VERIFY(result == vk::Result::eSuccess);
    }
}

void Demo::prepare_depth() {
    depth.format = vk::Format::eD16Unorm;

    auto const image = vk::ImageCreateInfo()
                           .setImageType(vk::ImageType::e2D)
                           .setFormat(depth.format)
                           .setExtent({static_cast<uint32_t>(width), static_cast<uint32_t>(height), 1})
                           .setMipLevels(1)
                           .setArrayLayers(1)
                           .setSamples(vk::SampleCountFlagBits::e1)
                           .setTiling(vk::ImageTiling::eOptimal)
                           .setUsage(vk::ImageUsageFlagBits::eDepthStencilAttachment)
                           .setSharingMode(vk::SharingMode::eExclusive)
                           .setInitialLayout(vk::ImageLayout::eUndefined);

    auto result = device.createImage(&image, nullptr, &depth.image);
    VERIFY(result == vk::Result::eSuccess);

    vk::MemoryRequirements mem_reqs;
    device.getImageMemoryRequirements(depth.image, &mem_reqs);

    depth.mem_alloc.setAllocationSize(mem_reqs.size);
    depth.mem_alloc.setMemoryTypeIndex(0);

    auto const pass = memory_type_from_properties(mem_reqs.memoryTypeBits, vk::MemoryPropertyFlagBits::eDeviceLocal,
                                                  depth.mem_alloc.memoryTypeIndex);
    VERIFY(pass);

    result = device.allocateMemory(&depth.mem_alloc, nullptr, &depth.mem);
    VERIFY(result == vk::Result::eSuccess);

    result = device.bindImageMemory(depth.image, depth.mem, 0);
    VERIFY(result == vk::Result::eSuccess);

    auto view = vk::ImageViewCreateInfo()
                    .setImage(depth.image)
                    .setViewType(vk::ImageViewType::e2D)
                    .setFormat(depth.format)
                    .setSubresourceRange(vk::ImageSubresourceRange(vk::ImageAspectFlagBits::eDepth, 0, 1, 0, 1));
    if (force_errors) {
        // Intentionally force a bad pNext value to generate a validation layer error
        view.pNext = &image;
    }
    result = device.createImageView(&view, nullptr, &depth.view);
    VERIFY(result == vk::Result::eSuccess);
}

void Demo::prepare_descriptor_layout() {
    std::array<vk::DescriptorSetLayoutBinding, 2> const layout_bindings = {
        vk::DescriptorSetLayoutBinding()
            .setBinding(0)
            .setDescriptorType(vk::DescriptorType::eUniformBuffer)
            .setDescriptorCount(1)
            .setStageFlags(vk::ShaderStageFlagBits::eVertex)
            .setPImmutableSamplers(nullptr),
        vk::DescriptorSetLayoutBinding()
            .setBinding(1)
            .setDescriptorType(vk::DescriptorType::eCombinedImageSampler)
            .setDescriptorCount(texture_count)
            .setStageFlags(vk::ShaderStageFlagBits::eFragment)
            .setPImmutableSamplers(nullptr)};

    auto const descriptor_layout = vk::DescriptorSetLayoutCreateInfo().setBindings(layout_bindings);

    auto result = device.createDescriptorSetLayout(&descriptor_layout, nullptr, &desc_layout);
    VERIFY(result == vk::Result::eSuccess);

    auto const pPipelineLayoutCreateInfo = vk::PipelineLayoutCreateInfo().setSetLayouts(desc_layout);

    result = device.createPipelineLayout(&pPipelineLayoutCreateInfo, nullptr, &pipeline_layout);
    VERIFY(result == vk::Result::eSuccess);
}

void Demo::prepare_descriptor_pool() {
    std::array<vk::DescriptorPoolSize, 2> const poolSizes = {
        vk::DescriptorPoolSize()
            .setType(vk::DescriptorType::eUniformBuffer)
            .setDescriptorCount(static_cast<uint32_t>(swapchain_image_resources.size())),
        vk::DescriptorPoolSize()
            .setType(vk::DescriptorType::eCombinedImageSampler)
            .setDescriptorCount(static_cast<uint32_t>(swapchain_image_resources.size()) * texture_count)};

    auto const descriptor_pool =
        vk::DescriptorPoolCreateInfo().setMaxSets(static_cast<uint32_t>(swapchain_image_resources.size())).setPoolSizes(poolSizes);

    auto result = device.createDescriptorPool(&descriptor_pool, nullptr, &desc_pool);
    VERIFY(result == vk::Result::eSuccess);
}

void Demo::prepare_descriptor_set() {
    auto const alloc_info = vk::DescriptorSetAllocateInfo().setDescriptorPool(desc_pool).setSetLayouts(desc_layout);

    auto buffer_info = vk::DescriptorBufferInfo().setOffset(0).setRange(sizeof(vktexcube_vs_uniform));

    std::array<vk::DescriptorImageInfo, texture_count> tex_descs;
    for (uint32_t i = 0; i < texture_count; i++) {
        tex_descs[i].setSampler(textures[i].sampler);
        tex_descs[i].setImageView(textures[i].view);
        tex_descs[i].setImageLayout(vk::ImageLayout::eShaderReadOnlyOptimal);
    }

    std::array<vk::WriteDescriptorSet, 2> writes;
    writes[0].setDescriptorCount(1).setDescriptorType(vk::DescriptorType::eUniformBuffer).setPBufferInfo(&buffer_info);
    writes[1]
        .setDstBinding(1)
        .setDescriptorCount(texture_count)
        .setDescriptorType(vk::DescriptorType::eCombinedImageSampler)
        .setImageInfo(tex_descs);

    for (auto &swapchain_image_resource : swapchain_image_resources) {
        auto result = device.allocateDescriptorSets(&alloc_info, &swapchain_image_resource.descriptor_set);
        VERIFY(result == vk::Result::eSuccess);

        buffer_info.setBuffer(swapchain_image_resource.uniform_buffer);
        writes[0].setDstSet(swapchain_image_resource.descriptor_set);
        writes[1].setDstSet(swapchain_image_resource.descriptor_set);
        device.updateDescriptorSets(writes, {});
    }
}

void Demo::prepare_framebuffers() {
    std::array<vk::ImageView, 2> attachments;
    attachments[1] = depth.view;

    for (auto &swapchain_image_resource : swapchain_image_resources) {
        attachments[0] = swapchain_image_resource.view;
        auto const framebuffer_return = device.createFramebuffer(vk::FramebufferCreateInfo()
                                                                     .setRenderPass(render_pass)
                                                                     .setAttachments(attachments)
                                                                     .setWidth(static_cast<uint32_t>(width))
                                                                     .setHeight(static_cast<uint32_t>(height))
                                                                     .setLayers(1));
        VERIFY(framebuffer_return.result == vk::Result::eSuccess);
        swapchain_image_resource.framebuffer = framebuffer_return.value;
    }
}

vk::ShaderModule Demo::prepare_fs() {
    const uint32_t fragShaderCode[] = {
#include "cube.frag.inc"
    };

    frag_shader_module = prepare_shader_module(fragShaderCode, sizeof(fragShaderCode));

    return frag_shader_module;
}

void Demo::prepare_pipeline() {
    vk::PipelineCacheCreateInfo const pipelineCacheInfo;
    auto result = device.createPipelineCache(&pipelineCacheInfo, nullptr, &pipelineCache);
    VERIFY(result == vk::Result::eSuccess);

    std::array<vk::PipelineShaderStageCreateInfo, 2> const shaderStageInfo = {
        vk::PipelineShaderStageCreateInfo().setStage(vk::ShaderStageFlagBits::eVertex).setModule(prepare_vs()).setPName("main"),
        vk::PipelineShaderStageCreateInfo().setStage(vk::ShaderStageFlagBits::eFragment).setModule(prepare_fs()).setPName("main")};

    vk::PipelineVertexInputStateCreateInfo const vertexInputInfo;

    auto const inputAssemblyInfo = vk::PipelineInputAssemblyStateCreateInfo().setTopology(vk::PrimitiveTopology::eTriangleList);

    // TODO: Where are pViewports and pScissors set?
    auto const viewportInfo = vk::PipelineViewportStateCreateInfo().setViewportCount(1).setScissorCount(1);

    auto const rasterizationInfo = vk::PipelineRasterizationStateCreateInfo()
                                       .setDepthClampEnable(VK_FALSE)
                                       .setRasterizerDiscardEnable(VK_FALSE)
                                       .setPolygonMode(vk::PolygonMode::eFill)
                                       .setCullMode(vk::CullModeFlagBits::eBack)
                                       .setFrontFace(vk::FrontFace::eCounterClockwise)
                                       .setDepthBiasEnable(VK_FALSE)
                                       .setLineWidth(1.0f);

    auto const multisampleInfo = vk::PipelineMultisampleStateCreateInfo();

    auto const stencilOp =
        vk::StencilOpState().setFailOp(vk::StencilOp::eKeep).setPassOp(vk::StencilOp::eKeep).setCompareOp(vk::CompareOp::eAlways);

    auto const depthStencilInfo = vk::PipelineDepthStencilStateCreateInfo()
                                      .setDepthTestEnable(VK_TRUE)
                                      .setDepthWriteEnable(VK_TRUE)
                                      .setDepthCompareOp(vk::CompareOp::eLessOrEqual)
                                      .setDepthBoundsTestEnable(VK_FALSE)
                                      .setStencilTestEnable(VK_FALSE)
                                      .setFront(stencilOp)
                                      .setBack(stencilOp);

    std::array<vk::PipelineColorBlendAttachmentState, 1> const colorBlendAttachments = {
        vk::PipelineColorBlendAttachmentState().setColorWriteMask(vk::ColorComponentFlagBits::eR | vk::ColorComponentFlagBits::eG |
                                                                  vk::ColorComponentFlagBits::eB | vk::ColorComponentFlagBits::eA)};

    auto const colorBlendInfo = vk::PipelineColorBlendStateCreateInfo().setAttachments(colorBlendAttachments);

    std::array<vk::DynamicState, 2> const dynamicStates = {vk::DynamicState::eViewport, vk::DynamicState::eScissor};

    auto const dynamicStateInfo = vk::PipelineDynamicStateCreateInfo().setDynamicStates(dynamicStates);

    auto pipline_return = device.createGraphicsPipelines(pipelineCache, vk::GraphicsPipelineCreateInfo()
                                                                            .setStages(shaderStageInfo)
                                                                            .setPVertexInputState(&vertexInputInfo)
                                                                            .setPInputAssemblyState(&inputAssemblyInfo)
                                                                            .setPViewportState(&viewportInfo)
                                                                            .setPRasterizationState(&rasterizationInfo)
                                                                            .setPMultisampleState(&multisampleInfo)
                                                                            .setPDepthStencilState(&depthStencilInfo)
                                                                            .setPColorBlendState(&colorBlendInfo)
                                                                            .setPDynamicState(&dynamicStateInfo)
                                                                            .setLayout(pipeline_layout)
                                                                            .setRenderPass(render_pass));
    VERIFY(result == vk::Result::eSuccess);
    pipeline = pipline_return.value.at(0);

    device.destroyShaderModule(frag_shader_module);
    device.destroyShaderModule(vert_shader_module);
}

void Demo::prepare_render_pass() {
    // The initial layout for the color and depth attachments will be LAYOUT_UNDEFINED
    // because at the start of the renderpass, we don't care about their contents.
    // At the start of the subpass, the color attachment's layout will be transitioned
    // to LAYOUT_COLOR_ATTACHMENT_OPTIMAL and the depth stencil attachment's layout
    // will be transitioned to LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL.  At the end of
    // the renderpass, the color attachment's layout will be transitioned to
    // LAYOUT_PRESENT_SRC_KHR to be ready to present.  This is all done as part of
    // the renderpass, no barriers are necessary.
    std::array<vk::AttachmentDescription, 2> const attachments = {
        vk::AttachmentDescription()
            .setFormat(format)
            .setSamples(vk::SampleCountFlagBits::e1)
            .setLoadOp(vk::AttachmentLoadOp::eClear)
            .setStoreOp(vk::AttachmentStoreOp::eStore)
            .setStencilLoadOp(vk::AttachmentLoadOp::eDontCare)
            .setStencilStoreOp(vk::AttachmentStoreOp::eDontCare)
            .setInitialLayout(vk::ImageLayout::eUndefined)
            .setFinalLayout(vk::ImageLayout::ePresentSrcKHR),
        vk::AttachmentDescription()
            .setFormat(depth.format)
            .setSamples(vk::SampleCountFlagBits::e1)
            .setLoadOp(vk::AttachmentLoadOp::eClear)
            .setStoreOp(vk::AttachmentStoreOp::eDontCare)
            .setStencilLoadOp(vk::AttachmentLoadOp::eDontCare)
            .setStencilStoreOp(vk::AttachmentStoreOp::eDontCare)
            .setInitialLayout(vk::ImageLayout::eUndefined)
            .setFinalLayout(vk::ImageLayout::eDepthStencilAttachmentOptimal)};

    auto const color_reference = vk::AttachmentReference().setAttachment(0).setLayout(vk::ImageLayout::eColorAttachmentOptimal);

    auto const depth_reference =
        vk::AttachmentReference().setAttachment(1).setLayout(vk::ImageLayout::eDepthStencilAttachmentOptimal);

    auto const subpass = vk::SubpassDescription()
                             .setPipelineBindPoint(vk::PipelineBindPoint::eGraphics)
                             .setColorAttachments(color_reference)
                             .setPDepthStencilAttachment(&depth_reference);

    vk::PipelineStageFlags stages = vk::PipelineStageFlagBits::eEarlyFragmentTests | vk::PipelineStageFlagBits::eLateFragmentTests;
    std::array<vk::SubpassDependency, 2> const dependencies = {
        vk::SubpassDependency()  // Depth buffer is shared between swapchain images
            .setSrcSubpass(VK_SUBPASS_EXTERNAL)
            .setDstSubpass(0)
            .setSrcStageMask(stages)
            .setDstStageMask(stages)
            .setSrcAccessMask(vk::AccessFlagBits::eDepthStencilAttachmentWrite)
            .setDstAccessMask(vk::AccessFlagBits::eDepthStencilAttachmentRead | vk::AccessFlagBits::eDepthStencilAttachmentWrite)
            .setDependencyFlags(vk::DependencyFlags()),
        vk::SubpassDependency()  // Image layout transition
            .setSrcSubpass(VK_SUBPASS_EXTERNAL)
            .setDstSubpass(0)
            .setSrcStageMask(vk::PipelineStageFlagBits::eColorAttachmentOutput)
            .setDstStageMask(vk::PipelineStageFlagBits::eColorAttachmentOutput)
            .setSrcAccessMask(vk::AccessFlagBits())
            .setDstAccessMask(vk::AccessFlagBits::eColorAttachmentWrite | vk::AccessFlagBits::eColorAttachmentRead)
            .setDependencyFlags(vk::DependencyFlags()),
    };

    const auto render_pass_result = device.createRenderPass(
        vk::RenderPassCreateInfo().setAttachments(attachments).setSubpasses(subpass).setDependencies(dependencies));
    VERIFY(render_pass_result.result == vk::Result::eSuccess);
    render_pass = render_pass_result.value;
}

vk::ShaderModule Demo::prepare_shader_module(const uint32_t *code, size_t size) {
    const auto shader_module_return = device.createShaderModule(vk::ShaderModuleCreateInfo().setCodeSize(size).setPCode(code));
    VERIFY(shader_module_return.result == vk::Result::eSuccess);

    return shader_module_return.value;
}

void Demo::prepare_texture_buffer(const char *filename, texture_object &tex_obj) {
    vk::SubresourceLayout tex_layout;
    int32_t tex_width;
    int32_t tex_height;
    if (!loadTexture(filename, nullptr, tex_layout, tex_width, tex_height)) {
        ERR_EXIT("Failed to load textures", "Load Texture Failure");
    }

    tex_obj.tex_width = tex_width;
    tex_obj.tex_height = tex_height;

    auto const buffer_create_info = vk::BufferCreateInfo()
                                        .setSize(tex_width * tex_height * 4)
                                        .setUsage(vk::BufferUsageFlagBits::eTransferSrc)
                                        .setSharingMode(vk::SharingMode::eExclusive);

    auto result = device.createBuffer(&buffer_create_info, nullptr, &tex_obj.buffer);
    VERIFY(result == vk::Result::eSuccess);

    vk::MemoryRequirements mem_reqs;
    device.getBufferMemoryRequirements(tex_obj.buffer, &mem_reqs);

    tex_obj.mem_alloc.setAllocationSize(mem_reqs.size);
    tex_obj.mem_alloc.setMemoryTypeIndex(0);

    vk::MemoryPropertyFlags requirements = vk::MemoryPropertyFlagBits::eHostVisible | vk::MemoryPropertyFlagBits::eHostCoherent;
    auto pass = memory_type_from_properties(mem_reqs.memoryTypeBits, requirements, tex_obj.mem_alloc.memoryTypeIndex);
    VERIFY(pass == true);

    result = device.allocateMemory(&tex_obj.mem_alloc, nullptr, &(tex_obj.mem));
    VERIFY(result == vk::Result::eSuccess);

    result = device.bindBufferMemory(tex_obj.buffer, tex_obj.mem, 0);
    VERIFY(result == vk::Result::eSuccess);

    vk::SubresourceLayout layout;
    layout.rowPitch = tex_width * 4;
    auto data = device.mapMemory(tex_obj.mem, 0, tex_obj.mem_alloc.allocationSize);
    VERIFY(data.result == vk::Result::eSuccess);

    if (!loadTexture(filename, (uint8_t *)data.value, layout, tex_width, tex_height)) {
        fprintf(stderr, "Error loading texture: %s\n", filename);
    }

    device.unmapMemory(tex_obj.mem);
}

void Demo::prepare_texture_image(const char *filename, texture_object &tex_obj, vk::ImageTiling tiling, vk::ImageUsageFlags usage,
                                 vk::MemoryPropertyFlags required_props) {
    vk::SubresourceLayout tex_layout;
    int32_t tex_width;
    int32_t tex_height;
    if (!loadTexture(filename, nullptr, tex_layout, tex_width, tex_height)) {
        ERR_EXIT("Failed to load textures", "Load Texture Failure");
    }

    tex_obj.tex_width = tex_width;
    tex_obj.tex_height = tex_height;

    auto const image_create_info = vk::ImageCreateInfo()
                                       .setImageType(vk::ImageType::e2D)
                                       .setFormat(vk::Format::eR8G8B8A8Unorm)
                                       .setExtent({static_cast<uint32_t>(tex_width), static_cast<uint32_t>(tex_height), 1})
                                       .setMipLevels(1)
                                       .setArrayLayers(1)
                                       .setSamples(vk::SampleCountFlagBits::e1)
                                       .setTiling(tiling)
                                       .setUsage(usage)
                                       .setSharingMode(vk::SharingMode::eExclusive)
                                       .setInitialLayout(vk::ImageLayout::ePreinitialized);

    auto result = device.createImage(&image_create_info, nullptr, &tex_obj.image);
    VERIFY(result == vk::Result::eSuccess);

    vk::MemoryRequirements mem_reqs;
    device.getImageMemoryRequirements(tex_obj.image, &mem_reqs);

    tex_obj.mem_alloc.setAllocationSize(mem_reqs.size);
    tex_obj.mem_alloc.setMemoryTypeIndex(0);

    auto pass = memory_type_from_properties(mem_reqs.memoryTypeBits, required_props, tex_obj.mem_alloc.memoryTypeIndex);
    VERIFY(pass == true);

    result = device.allocateMemory(&tex_obj.mem_alloc, nullptr, &tex_obj.mem);
    VERIFY(result == vk::Result::eSuccess);

    result = device.bindImageMemory(tex_obj.image, tex_obj.mem, 0);
    VERIFY(result == vk::Result::eSuccess);

    if (required_props & vk::MemoryPropertyFlagBits::eHostVisible) {
        auto const subres = vk::ImageSubresource().setAspectMask(vk::ImageAspectFlagBits::eColor).setMipLevel(0).setArrayLayer(0);
        vk::SubresourceLayout layout;
        device.getImageSubresourceLayout(tex_obj.image, &subres, &layout);

        auto data = device.mapMemory(tex_obj.mem, 0, tex_obj.mem_alloc.allocationSize);
        VERIFY(data.result == vk::Result::eSuccess);

        if (!loadTexture(filename, (uint8_t *)data.value, layout, tex_width, tex_height)) {
            fprintf(stderr, "Error loading texture: %s\n", filename);
        }

        device.unmapMemory(tex_obj.mem);
    }

    tex_obj.imageLayout = vk::ImageLayout::eShaderReadOnlyOptimal;
}

void Demo::prepare_textures() {
    vk::Format const tex_format = vk::Format::eR8G8B8A8Unorm;
    vk::FormatProperties props;
    gpu.getFormatProperties(tex_format, &props);

    for (uint32_t i = 0; i < texture_count; i++) {
        if ((props.linearTilingFeatures & vk::FormatFeatureFlagBits::eSampledImage) && !use_staging_buffer) {
            /* Device can texture using linear textures */
            prepare_texture_image(tex_files[i], textures[i], vk::ImageTiling::eLinear, vk::ImageUsageFlagBits::eSampled,
                                  vk::MemoryPropertyFlagBits::eHostVisible | vk::MemoryPropertyFlagBits::eHostCoherent);
            // Nothing in the pipeline needs to be complete to start, and don't allow fragment
            // shader to run until layout transition completes
            set_image_layout(textures[i].image, vk::ImageAspectFlagBits::eColor, vk::ImageLayout::ePreinitialized,
                             textures[i].imageLayout, vk::AccessFlagBits(), vk::PipelineStageFlagBits::eTopOfPipe,
                             vk::PipelineStageFlagBits::eFragmentShader);
            staging_texture.image = vk::Image();
        } else if (props.optimalTilingFeatures & vk::FormatFeatureFlagBits::eSampledImage) {
            /* Must use staging buffer to copy linear texture to optimized */

            prepare_texture_buffer(tex_files[i], staging_texture);

            prepare_texture_image(tex_files[i], textures[i], vk::ImageTiling::eOptimal,
                                  vk::ImageUsageFlagBits::eTransferDst | vk::ImageUsageFlagBits::eSampled,
                                  vk::MemoryPropertyFlagBits::eDeviceLocal);

            set_image_layout(textures[i].image, vk::ImageAspectFlagBits::eColor, vk::ImageLayout::ePreinitialized,
                             vk::ImageLayout::eTransferDstOptimal, vk::AccessFlagBits(), vk::PipelineStageFlagBits::eTopOfPipe,
                             vk::PipelineStageFlagBits::eTransfer);

            auto const subresource = vk::ImageSubresourceLayers()
                                         .setAspectMask(vk::ImageAspectFlagBits::eColor)
                                         .setMipLevel(0)
                                         .setBaseArrayLayer(0)
                                         .setLayerCount(1);

            auto const copy_region = vk::BufferImageCopy()
                                         .setBufferOffset(0)
                                         .setBufferRowLength(staging_texture.tex_width)
                                         .setBufferImageHeight(staging_texture.tex_height)
                                         .setImageSubresource(subresource)
                                         .setImageOffset({0, 0, 0})
                                         .setImageExtent({static_cast<uint32_t>(staging_texture.tex_width),
                                                          static_cast<uint32_t>(staging_texture.tex_height), 1});

            cmd.copyBufferToImage(staging_texture.buffer, textures[i].image, vk::ImageLayout::eTransferDstOptimal, 1, &copy_region);

            set_image_layout(textures[i].image, vk::ImageAspectFlagBits::eColor, vk::ImageLayout::eTransferDstOptimal,
                             textures[i].imageLayout, vk::AccessFlagBits::eTransferWrite, vk::PipelineStageFlagBits::eTransfer,
                             vk::PipelineStageFlagBits::eFragmentShader);
        } else {
            assert(!"No support for R8G8B8A8_UNORM as texture image format");
        }

        auto const samplerInfo = vk::SamplerCreateInfo()
                                     .setMagFilter(vk::Filter::eNearest)
                                     .setMinFilter(vk::Filter::eNearest)
                                     .setMipmapMode(vk::SamplerMipmapMode::eNearest)
                                     .setAddressModeU(vk::SamplerAddressMode::eClampToEdge)
                                     .setAddressModeV(vk::SamplerAddressMode::eClampToEdge)
                                     .setAddressModeW(vk::SamplerAddressMode::eClampToEdge)
                                     .setMipLodBias(0.0f)
                                     .setAnisotropyEnable(VK_FALSE)
                                     .setMaxAnisotropy(1)
                                     .setCompareEnable(VK_FALSE)
                                     .setCompareOp(vk::CompareOp::eNever)
                                     .setMinLod(0.0f)
                                     .setMaxLod(0.0f)
                                     .setBorderColor(vk::BorderColor::eFloatOpaqueWhite)
                                     .setUnnormalizedCoordinates(VK_FALSE);

        auto result = device.createSampler(&samplerInfo, nullptr, &textures[i].sampler);
        VERIFY(result == vk::Result::eSuccess);

        auto const viewInfo = vk::ImageViewCreateInfo()
                                  .setImage(textures[i].image)
                                  .setViewType(vk::ImageViewType::e2D)
                                  .setFormat(tex_format)
                                  .setSubresourceRange(vk::ImageSubresourceRange(vk::ImageAspectFlagBits::eColor, 0, 1, 0, 1));

        result = device.createImageView(&viewInfo, nullptr, &textures[i].view);
        VERIFY(result == vk::Result::eSuccess);
    }
}

vk::ShaderModule Demo::prepare_vs() {
    const uint32_t vertShaderCode[] = {
#include "cube.vert.inc"
    };

    vert_shader_module = prepare_shader_module(vertShaderCode, sizeof(vertShaderCode));

    return vert_shader_module;
}

void Demo::destroy_swapchain_related_resources() {
    device.destroyDescriptorPool(desc_pool);

    device.destroyPipeline(pipeline);
    device.destroyPipelineCache(pipelineCache);
    device.destroyRenderPass(render_pass);
    device.destroyPipelineLayout(pipeline_layout);
    device.destroyDescriptorSetLayout(desc_layout);

    for (const auto &tex : textures) {
        device.destroyImageView(tex.view);
        device.destroyImage(tex.image);
        device.freeMemory(tex.mem);
        device.destroySampler(tex.sampler);
    }

    device.destroyImageView(depth.view);
    device.destroyImage(depth.image);
    device.freeMemory(depth.mem);

    for (const auto &resource : swapchain_image_resources) {
        device.destroyFramebuffer(resource.framebuffer);
        device.destroyImageView(resource.view);
        device.freeCommandBuffers(cmd_pool, {resource.cmd});
        device.destroyBuffer(resource.uniform_buffer);
        device.unmapMemory(resource.uniform_memory);
        device.freeMemory(resource.uniform_memory);
    }

    device.destroyCommandPool(cmd_pool);
    if (separate_present_queue) {
        device.destroyCommandPool(present_cmd_pool);
    }
}

void Demo::resize() {
    // Don't react to resize until after first initialization.
    if (!prepared) {
        return;
    }

    // In order to properly resize the window, we must re-create the
    // swapchain
    // AND redo the command buffers, etc.
    //
    // First, perform part of the cleanup() function:
    prepared = false;
    auto result = device.waitIdle();
    VERIFY(result == vk::Result::eSuccess);
    destroy_swapchain_related_resources();

    // Second, re-perform the prepare() function, which will re-create the
    // swapchain.
    prepare();
}

void Demo::set_image_layout(vk::Image image, vk::ImageAspectFlags aspectMask, vk::ImageLayout oldLayout, vk::ImageLayout newLayout,
                            vk::AccessFlags srcAccessMask, vk::PipelineStageFlags src_stages, vk::PipelineStageFlags dest_stages) {
    assert(cmd);

    auto DstAccessMask = [](vk::ImageLayout const &layout) {
        vk::AccessFlags flags;

        switch (layout) {
            case vk::ImageLayout::eTransferDstOptimal:
                // Make sure anything that was copying from this image has
                // completed
                flags = vk::AccessFlagBits::eTransferWrite;
                break;
            case vk::ImageLayout::eColorAttachmentOptimal:
                flags = vk::AccessFlagBits::eColorAttachmentWrite;
                break;
            case vk::ImageLayout::eDepthStencilAttachmentOptimal:
                flags = vk::AccessFlagBits::eDepthStencilAttachmentWrite;
                break;
            case vk::ImageLayout::eShaderReadOnlyOptimal:
                // Make sure any Copy or CPU writes to image are flushed
                flags = vk::AccessFlagBits::eShaderRead | vk::AccessFlagBits::eInputAttachmentRead;
                break;
            case vk::ImageLayout::eTransferSrcOptimal:
                flags = vk::AccessFlagBits::eTransferRead;
                break;
            case vk::ImageLayout::ePresentSrcKHR:
                flags = vk::AccessFlagBits::eMemoryRead;
                break;
            default:
                break;
        }

        return flags;
    };

    cmd.pipelineBarrier(src_stages, dest_stages, vk::DependencyFlagBits(), {}, {},
                        vk::ImageMemoryBarrier()
                            .setSrcAccessMask(srcAccessMask)
                            .setDstAccessMask(DstAccessMask(newLayout))
                            .setOldLayout(oldLayout)
                            .setNewLayout(newLayout)
                            .setSrcQueueFamilyIndex(VK_QUEUE_FAMILY_IGNORED)
                            .setDstQueueFamilyIndex(VK_QUEUE_FAMILY_IGNORED)
                            .setImage(image)
                            .setSubresourceRange(vk::ImageSubresourceRange(aspectMask, 0, 1, 0, 1)));
}

void Demo::update_data_buffer() {
    mat4x4 VP;
    mat4x4_mul(VP, projection_matrix, view_matrix);

    // Rotate around the Y axis
    mat4x4 Model;
    mat4x4_dup(Model, model_matrix);
    mat4x4_rotate_Y(model_matrix, Model, static_cast<float>(degreesToRadians(spin_angle)));
    mat4x4_orthonormalize(model_matrix, model_matrix);

    mat4x4 MVP;
    mat4x4_mul(MVP, VP, model_matrix);

    memcpy(swapchain_image_resources[current_buffer].uniform_memory_ptr, (const void *)&MVP[0][0], sizeof(MVP));
}

/* Convert ppm image data from header file into RGBA texture image */
#include "lunarg.ppm.h"
bool Demo::loadTexture(const char *filename, uint8_t *rgba_data, vk::SubresourceLayout &layout, int32_t &width, int32_t &height) {
    (void)filename;
    char *cPtr;
    cPtr = (char *)lunarg_ppm;
    if ((unsigned char *)cPtr >= (lunarg_ppm + lunarg_ppm_len) || strncmp(cPtr, "P6\n", 3)) {
        return false;
    }
    while (strncmp(cPtr++, "\n", 1))
        ;
    sscanf(cPtr, "%u %u", &width, &height);
    if (rgba_data == nullptr) {
        return true;
    }
    while (strncmp(cPtr++, "\n", 1))
        ;
    if ((unsigned char *)cPtr >= (lunarg_ppm + lunarg_ppm_len) || strncmp(cPtr, "255\n", 4)) {
        return false;
    }
    while (strncmp(cPtr++, "\n", 1))
        ;
    for (int y = 0; y < height; y++) {
        uint8_t *rowPtr = rgba_data;
        for (int x = 0; x < width; x++) {
            memcpy(rowPtr, cPtr, 3);
            rowPtr[3] = 255; /* Alpha of 1 */
            rowPtr += 4;
            cPtr += 3;
        }
        rgba_data += layout.rowPitch;
    }
    return true;
}

bool Demo::memory_type_from_properties(uint32_t typeBits, vk::MemoryPropertyFlags requirements_mask, uint32_t &typeIndex) {
    // Search memtypes to find first index with those properties
    for (uint32_t i = 0; i < VK_MAX_MEMORY_TYPES; i++) {
        if ((typeBits & 1) == 1) {
            // Type is available, does it match user properties?
            if ((memory_properties.memoryTypes[i].propertyFlags & requirements_mask) == requirements_mask) {
                typeIndex = i;
                return true;
            }
        }
        typeBits >>= 1;
    }

    // No memory types matched, return failure
    return false;
}

vk::SurfaceFormatKHR Demo::pick_surface_format(const std::vector<vk::SurfaceFormatKHR> &surface_formats) {
    // Prefer non-SRGB formats...
    for (const auto &surface_format : surface_formats) {
        const vk::Format format = surface_format.format;

        if (format == vk::Format::eR8G8B8A8Unorm || format == vk::Format::eB8G8R8A8Unorm ||
            format == vk::Format::eA2B10G10R10UnormPack32 || format == vk::Format::eA2R10G10B10UnormPack32 ||
            format == vk::Format::eR16G16B16A16Sfloat) {
            return surface_format;
        }
    }

    printf("Can't find our preferred formats... Falling back to first exposed format. Rendering may be incorrect.\n");

    assert(surface_formats.size() >= 1);
    return surface_formats[0];
}

#if defined(VK_USE_PLATFORM_WIN32_KHR)
void Demo::run() {
    if (!prepared) {
        return;
    }

    draw();
    curFrame++;

    if (frameCount != UINT32_MAX && curFrame == frameCount) {
        PostQuitMessage(validation_error);
    }
}

void Demo::create_window() {
    WNDCLASSEX win_class;

    // Initialize the window class structure:
    win_class.cbSize = sizeof(WNDCLASSEX);
    win_class.style = CS_HREDRAW | CS_VREDRAW;
    win_class.lpfnWndProc = WndProc;
    win_class.cbClsExtra = 0;
    win_class.cbWndExtra = 0;
    win_class.hInstance = connection;  // hInstance
    win_class.hIcon = LoadIcon(nullptr, IDI_APPLICATION);
    win_class.hCursor = LoadCursor(nullptr, IDC_ARROW);
    win_class.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    win_class.lpszMenuName = nullptr;
    win_class.lpszClassName = name.c_str();
    win_class.hIconSm = LoadIcon(nullptr, IDI_WINLOGO);

    // Register window class:
    if (!RegisterClassEx(&win_class)) {
        // It didn't work, so try to give a useful error:
        printf("Unexpected error trying to start the application!\n");
        fflush(stdout);
        exit(1);
    }

    // Create window with the registered class:
    RECT wr = {0, 0, static_cast<LONG>(width), static_cast<LONG>(height)};
    AdjustWindowRect(&wr, WS_OVERLAPPEDWINDOW, FALSE);
    window = CreateWindowEx(0,
                            name.c_str(),          // class name
                            name.c_str(),          // app name
                            WS_OVERLAPPEDWINDOW |  // window style
                                WS_VISIBLE | WS_SYSMENU,
                            100, 100,            // x/y coords
                            wr.right - wr.left,  // width
                            wr.bottom - wr.top,  // height
                            nullptr,             // handle to parent
                            nullptr,             // handle to menu
                            connection,          // hInstance
                            nullptr);            // no extra parameters

    if (!window) {
        // It didn't work, so try to give a useful error:
        printf("Cannot create a window in which to draw!\n");
        fflush(stdout);
        exit(1);
    }

    // Window client area size must be at least 1 pixel high, to prevent
    // crash.
    minsize.x = GetSystemMetrics(SM_CXMINTRACK);
    minsize.y = GetSystemMetrics(SM_CYMINTRACK) + 1;
}
#elif defined(VK_USE_PLATFORM_XLIB_KHR)

void Demo::create_xlib_window() {
    const char *display_envar = getenv("DISPLAY");
    if (display_envar == nullptr || display_envar[0] == '\0') {
        printf("Environment variable DISPLAY requires a valid value.\nExiting ...\n");
        fflush(stdout);
        exit(1);
    }

    XInitThreads();
    display = XOpenDisplay(nullptr);
    long visualMask = VisualScreenMask;
    int numberOfVisuals;
    XVisualInfo vInfoTemplate = {};
    vInfoTemplate.screen = DefaultScreen(display);
    XVisualInfo *visualInfo = XGetVisualInfo(display, visualMask, &vInfoTemplate, &numberOfVisuals);

    Colormap colormap = XCreateColormap(display, RootWindow(display, vInfoTemplate.screen), visualInfo->visual, AllocNone);

    XSetWindowAttributes windowAttributes = {};
    windowAttributes.colormap = colormap;
    windowAttributes.background_pixel = 0xFFFFFFFF;
    windowAttributes.border_pixel = 0;
    windowAttributes.event_mask = KeyPressMask | KeyReleaseMask | StructureNotifyMask | ExposureMask;

    xlib_window =
        XCreateWindow(display, RootWindow(display, vInfoTemplate.screen), 0, 0, width, height, 0, visualInfo->depth, InputOutput,
                      visualInfo->visual, CWBackPixel | CWBorderPixel | CWEventMask | CWColormap, &windowAttributes);

    XSelectInput(display, xlib_window, ExposureMask | KeyPressMask);
    XMapWindow(display, xlib_window);
    XFlush(display);
    xlib_wm_delete_window = XInternAtom(display, "WM_DELETE_WINDOW", False);
}

void Demo::handle_xlib_event(const XEvent *event) {
    switch (event->type) {
        case ClientMessage:
            if ((Atom)event->xclient.data.l[0] == xlib_wm_delete_window) {
                quit = true;
            }
            break;
        case KeyPress:
            switch (event->xkey.keycode) {
                case 0x9:  // Escape
                    quit = true;
                    break;
                case 0x71:  // left arrow key
                    spin_angle -= spin_increment;
                    break;
                case 0x72:  // right arrow key
                    spin_angle += spin_increment;
                    break;
                case 0x41:  // space bar
                    pause = !pause;
                    break;
            }
            break;
        case ConfigureNotify:
            if (((int32_t)width != event->xconfigure.width) || ((int32_t)height != event->xconfigure.height)) {
                width = event->xconfigure.width;
                height = event->xconfigure.height;
                resize();
            }
            break;
        default:
            break;
    }
}

void Demo::run_xlib() {
    while (!quit) {
        XEvent event;

        if (pause) {
            XNextEvent(display, &event);
            handle_xlib_event(&event);
        }
        while (XPending(display) > 0) {
            XNextEvent(display, &event);
            handle_xlib_event(&event);
        }

        draw();
        curFrame++;

        if (frameCount != UINT32_MAX && curFrame == frameCount) {
            quit = true;
        }
    }
}
#elif defined(VK_USE_PLATFORM_XCB_KHR)

void Demo::handle_xcb_event(const xcb_generic_event_t *event) {
    uint8_t event_code = event->response_type & 0x7f;
    switch (event_code) {
        case XCB_EXPOSE:
            // TODO: Resize window
            break;
        case XCB_CLIENT_MESSAGE:
            if ((*(xcb_client_message_event_t *)event).data.data32[0] == (*atom_wm_delete_window).atom) {
                quit = true;
            }
            break;
        case XCB_KEY_RELEASE: {
            const xcb_key_release_event_t *key = (const xcb_key_release_event_t *)event;

            switch (key->detail) {
                case 0x9:  // Escape
                    quit = true;
                    break;
                case 0x71:  // left arrow key
                    spin_angle -= spin_increment;
                    break;
                case 0x72:  // right arrow key
                    spin_angle += spin_increment;
                    break;
                case 0x41:  // space bar
                    pause = !pause;
                    break;
            }
        } break;
        case XCB_CONFIGURE_NOTIFY: {
            const xcb_configure_notify_event_t *cfg = (const xcb_configure_notify_event_t *)event;
            if ((width != cfg->width) || (height != cfg->height)) {
                width = cfg->width;
                height = cfg->height;
                resize();
            }
        } break;
        default:
            break;
    }
}

void Demo::run_xcb() {
    xcb_flush(connection);

    while (!quit) {
        xcb_generic_event_t *event;

        if (pause) {
            event = xcb_wait_for_event(connection);
        } else {
            event = xcb_poll_for_event(connection);
        }
        while (event) {
            handle_xcb_event(event);
            free(event);
            event = xcb_poll_for_event(connection);
        }

        draw();
        curFrame++;
        if (frameCount != UINT32_MAX && curFrame == frameCount) {
            quit = true;
        }
    }
}

void Demo::create_xcb_window() {
    uint32_t value_mask, value_list[32];

    xcb_window = xcb_generate_id(connection);

    value_mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
    value_list[0] = screen->black_pixel;
    value_list[1] = XCB_EVENT_MASK_KEY_RELEASE | XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY;

    xcb_create_window(connection, XCB_COPY_FROM_PARENT, xcb_window, screen->root, 0, 0, width, height, 0,
                      XCB_WINDOW_CLASS_INPUT_OUTPUT, screen->root_visual, value_mask, value_list);

    /* Magic code that will send notification when window is destroyed */
    xcb_intern_atom_cookie_t cookie = xcb_intern_atom(connection, 1, 12, "WM_PROTOCOLS");
    xcb_intern_atom_reply_t *reply = xcb_intern_atom_reply(connection, cookie, 0);

    xcb_intern_atom_cookie_t cookie2 = xcb_intern_atom(connection, 0, 16, "WM_DELETE_WINDOW");
    atom_wm_delete_window = xcb_intern_atom_reply(connection, cookie2, 0);

    xcb_change_property(connection, XCB_PROP_MODE_REPLACE, xcb_window, (*reply).atom, 4, 32, 1, &(*atom_wm_delete_window).atom);

    free(reply);

    xcb_map_window(connection, xcb_window);

    // Force the x/y coordinates to 100,100 results are identical in
    // consecutive
    // runs
    std::array<uint32_t, 2> const coords = {100, 100};
    xcb_configure_window(connection, xcb_window, XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y, coords.data());
}
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)

void Demo::run() {
    while (!quit) {
        if (pause) {
            wl_display_dispatch(display);
        } else {
            wl_display_dispatch_pending(display);
            // update_data_buffer();
            draw();
            curFrame++;
            if (frameCount != UINT32_MAX && curFrame == frameCount) {
                quit = true;
            }
        }
    }
}

static void handle_surface_configure(void *data, xdg_surface *xdg_surface, uint32_t serial) {
    Demo *demo = (Demo *)data;
    xdg_surface_ack_configure(xdg_surface, serial);
    if (demo->xdg_surface_has_been_configured) {
        demo->resize();
    }
    demo->xdg_surface_has_been_configured = true;
}

static const xdg_surface_listener surface_listener = {handle_surface_configure};

static void handle_toplevel_configure(void *data, xdg_toplevel *xdg_toplevel, int32_t width, int32_t height,
                                      struct wl_array *states) {
    Demo *demo = (Demo *)data;
    /* zero values imply the program may choose its own size, so in that case
     * stay with the existing value (which on startup is the default) */
    if (width > 0) {
        demo->width = width;
    }
    if (height > 0) {
        demo->height = height;
    }
    // This will be followed by a surface configure
}

static void handle_toplevel_close(void *data, xdg_toplevel *xdg_toplevel) {
    Demo *demo = (Demo *)data;
    demo->quit = true;
}

static const xdg_toplevel_listener toplevel_listener = {handle_toplevel_configure, handle_toplevel_close};

void Demo::create_window() {
    if (!wm_base) {
        printf("Compositor did not provide the standard protocol xdg-wm-base\n");
        fflush(stdout);
        exit(1);
    }

    window = wl_compositor_create_surface(compositor);
    if (!window) {
        printf("Can not create wayland_surface from compositor!\n");
        fflush(stdout);
        exit(1);
    }

    window_surface = xdg_wm_base_get_xdg_surface(wm_base, window);
    if (!window_surface) {
        printf("Can not get xdg_surface from wayland_surface!\n");
        fflush(stdout);
        exit(1);
    }
    window_toplevel = xdg_surface_get_toplevel(window_surface);
    if (!window_toplevel) {
        printf("Can not allocate xdg_toplevel for xdg_surface!\n");
        fflush(stdout);
        exit(1);
    }
    xdg_surface_add_listener(window_surface, &surface_listener, this);
    xdg_toplevel_add_listener(window_toplevel, &toplevel_listener, this);
    xdg_toplevel_set_title(window_toplevel, APP_SHORT_NAME);
    if (xdg_decoration_mgr) {
        // if supported, let the compositor render titlebars for us
        toplevel_decoration = zxdg_decoration_manager_v1_get_toplevel_decoration(xdg_decoration_mgr, window_toplevel);
        zxdg_toplevel_decoration_v1_set_mode(toplevel_decoration, ZXDG_TOPLEVEL_DECORATION_V1_MODE_SERVER_SIDE);
    }

    wl_surface_commit(window);
}
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)

void Demo::handle_directfb_event(const DFBInputEvent *event) {
    if (event->type != DIET_KEYPRESS) return;
    switch (event->key_symbol) {
        case DIKS_ESCAPE:  // Escape
            quit = true;
            break;
        case DIKS_CURSOR_LEFT:  // left arrow key
            spin_angle -= spin_increment;
            break;
        case DIKS_CURSOR_RIGHT:  // right arrow key
            spin_angle += spin_increment;
            break;
        case DIKS_SPACE:  // space bar
            pause = !pause;
            break;
        default:
            break;
    }
}

void Demo::run_directfb() {
    while (!quit) {
        DFBInputEvent event;

        if (pause) {
            event_buffer->WaitForEvent(event_buffer);
            if (!event_buffer->GetEvent(event_buffer, DFB_EVENT(&event))) handle_directfb_event(&event);
        } else {
            if (!event_buffer->GetEvent(event_buffer, DFB_EVENT(&event))) handle_directfb_event(&event);

            draw();
            curFrame++;
            if (frameCount != UINT32_MAX && curFrame == frameCount) {
                quit = true;
            }
        }
    }
}

void Demo::create_directfb_window() {
    DFBResult ret;

    ret = DirectFBInit(nullptr, nullptr);
    if (ret) {
        printf("DirectFBInit failed to initialize DirectFB!\n");
        fflush(stdout);
        exit(1);
    }

    ret = DirectFBCreate(&dfb);
    if (ret) {
        printf("DirectFBCreate failed to create main interface of DirectFB!\n");
        fflush(stdout);
        exit(1);
    }

    DFBSurfaceDescription desc;
    desc.flags = (DFBSurfaceDescriptionFlags)(DSDESC_CAPS | DSDESC_WIDTH | DSDESC_HEIGHT);
    desc.caps = DSCAPS_PRIMARY;
    desc.width = width;
    desc.height = height;
    ret = dfb->CreateSurface(dfb, &desc, &window);
    if (ret) {
        printf("CreateSurface failed to create DirectFB surface interface!\n");
        fflush(stdout);
        exit(1);
    }

    ret = dfb->CreateInputEventBuffer(dfb, DICAPS_KEYS, DFB_FALSE, &event_buffer);
    if (ret) {
        printf("CreateInputEventBuffer failed to create DirectFB event buffer interface!\n");
        fflush(stdout);
        exit(1);
    }
}
#elif defined(VK_USE_PLATFORM_METAL_EXT)
void Demo::run() {
    draw();
    curFrame++;
    if (frameCount != UINT32_MAX && curFrame == frameCount) {
        quit = true;
    }
}
#elif defined(VK_USE_PLATFORM_DISPLAY_KHR)

vk::Result Demo::create_display_surface() {
    auto display_properties_return = gpu.getDisplayPropertiesKHR();
    VERIFY((display_properties_return.result == vk::Result::eSuccess) ||
           (display_properties_return.result == vk::Result::eIncomplete));

    auto display = display_properties_return.value.at(0).display;

    auto display_mode_props_return = gpu.getDisplayModePropertiesKHR(display);
    VERIFY(display_mode_props_return.result == vk::Result::eSuccess);

    if (display_mode_props_return.value.size() == 0) {
        printf("Cannot find any mode for the display!\n");
        fflush(stdout);
        exit(1);
    }
    auto display_mode_prop = display_mode_props_return.value.at(0);

    // Get the list of planes
    auto display_plane_props_return = gpu.getDisplayPlanePropertiesKHR();
    VERIFY(display_plane_props_return.result == vk::Result::eSuccess);

    if (display_plane_props_return.value.size() == 0) {
        printf("Cannot find any plane!\n");
        fflush(stdout);
        exit(1);
    }

    vk::Bool32 found_plane = VK_FALSE;
    // Find a plane compatible with the display
    for (uint32_t plane_index = 0; plane_index < display_plane_props_return.value.size(); plane_index++) {
        // Disqualify planes that are bound to a different display
        if (plane_props[plane_index].currentDisplay && (plane_props[plane_index].currentDisplay != display)) {
            continue;
        }

        auto display_plane_supported_displays_return = gpu.getDisplayPlaneSupportedDisplaysKHR(plane_index);
        VERIFY(display_plane_supported_displays_return.result == vk::Result::eSuccess);

        if (display_plane_supported_displays_return.value.size() == 0) {
            continue;
        }

        for (const auto &supported_display : display_plane_supported_displays_return.value) {
            if (supported_display == display) {
                found_plane = VK_TRUE;
                break;
            }
        }

        if (found_plane) {
            break;
        }
    }

    if (!found_plane) {
        printf("Cannot find a plane compatible with the display!\n");
        fflush(stdout);
        exit(1);
    }

    vk::DisplayPlaneCapabilitiesKHR planeCaps = gpu.getDisplayPlaneCapabilitiesKHR(mode_props.displayMode, plane_index);
    // Find a supported alpha mode
    vk::DisplayPlaneAlphaFlagBitsKHR alphaMode = vk::DisplayPlaneAlphaFlagBitsKHR::eOpaque;
    std::array<vk::DisplayPlaneAlphaFlagBitsKHR, 4> alphaModes = {
        vk::DisplayPlaneAlphaFlagBitsKHR::eOpaque,
        vk::DisplayPlaneAlphaFlagBitsKHR::eGlobal,
        vk::DisplayPlaneAlphaFlagBitsKHR::ePerPixel,
        vk::DisplayPlaneAlphaFlagBitsKHR::ePerPixelPremultiplied,
    };
    for (const auto &alpha_mode : alphaModes) {
        if (planeCaps.supportedAlpha & alpha_mode) {
            alphaMode = alpha_mode;
            break;
        }
    }

    vk::Extent2D image_extent{};
    image_extent.setWidth(mode_props.parameters.visibleRegion.width).setHeight(mode_props.parameters.visibleRegion.height);

    auto const createInfo = vk::DisplaySurfaceCreateInfoKHR()
                                .setDisplayMode(mode_props.displayMode)
                                .setPlaneIndex(plane_index)
                                .setPlaneStackIndex(plane_props[plane_index].currentStackIndex)
                                .setGlobalAlpha(1.0f)
                                .setAlphaMode(alphaMode)
                                .setImageExtent(image_extent);

    return inst.createDisplayPlaneSurfaceKHR(&createInfo, nullptr, &surface);
}

void Demo::run_display() {
    while (!quit) {
        draw();
        curFrame++;

        if (frameCount != UINT32_MAX && curFrame == frameCount) {
            quit = true;
        }
    }
}
#endif

#if _WIN32
// Include header required for parsing the command line options.
#include <shellapi.h>

Demo demo;

// MS-Windows event handling function:
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
    switch (uMsg) {
        case WM_CLOSE:
            PostQuitMessage(validation_error);
            break;
        case WM_PAINT:
            demo.run();
            break;
        case WM_GETMINMAXINFO:  // set window's minimum size
            ((MINMAXINFO *)lParam)->ptMinTrackSize = demo.minsize;
            return 0;
        case WM_ERASEBKGND:
            return 1;
        case WM_SIZE:
            // Resize the application to the new window size, except when
            // it was minimized. Vulkan doesn't support images or swapchains
            // with width=0 and height=0.
            if (wParam != SIZE_MINIMIZED) {
                demo.width = lParam & 0xffff;
                demo.height = (lParam & 0xffff0000) >> 16;
                demo.resize();
            }
            break;
        case WM_KEYDOWN:
            switch (wParam) {
                case VK_ESCAPE:
                    PostQuitMessage(validation_error);
                    break;
                case VK_LEFT:
                    demo.spin_angle -= demo.spin_increment;
                    break;
                case VK_RIGHT:
                    demo.spin_angle += demo.spin_increment;
                    break;
                case VK_SPACE:
                    demo.pause = !demo.pause;
                    break;
            }
            return 0;
        default:
            break;
    }

    return (DefWindowProc(hWnd, uMsg, wParam, lParam));
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR pCmdLine, int nCmdShow) {
    // TODO: Gah.. refactor. This isn't 1989.
    MSG msg;    // message
    bool done;  // flag saying when app is complete
    int argc;
    char **argv;

    // Ensure wParam is initialized.
    msg.wParam = 0;

    // Use the CommandLine functions to get the command line arguments.
    // Unfortunately, Microsoft outputs
    // this information as wide characters for Unicode, and we simply want the
    // Ascii version to be compatible
    // with the non-Windows side.  So, we have to convert the information to
    // Ascii character strings.
    LPWSTR *commandLineArgs = CommandLineToArgvW(GetCommandLineW(), &argc);
    if (nullptr == commandLineArgs) {
        argc = 0;
    }

    if (argc > 0) {
        argv = (char **)malloc(sizeof(char *) * argc);
        if (argv == nullptr) {
            argc = 0;
        } else {
            for (int iii = 0; iii < argc; iii++) {
                size_t wideCharLen = wcslen(commandLineArgs[iii]);
                size_t numConverted = 0;

                argv[iii] = (char *)malloc(sizeof(char) * (wideCharLen + 1));
                if (argv[iii] != nullptr) {
                    wcstombs_s(&numConverted, argv[iii], wideCharLen + 1, commandLineArgs[iii], wideCharLen + 1);
                }
            }
        }
    } else {
        argv = nullptr;
    }

    demo.init(argc, argv);

    // Free up the items we had to allocate for the command line arguments.
    if (argc > 0 && argv != nullptr) {
        for (int iii = 0; iii < argc; iii++) {
            if (argv[iii] != nullptr) {
                free(argv[iii]);
            }
        }
        free(argv);
    }

    demo.connection = hInstance;
    demo.name = "Vulkan Cube";
    demo.create_window();
    demo.init_vk_swapchain();

    demo.prepare();

    done = false;  // initialize loop condition variable

    // main message loop
    while (!done) {
        if (demo.pause) {
            const BOOL succ = WaitMessage();

            if (!succ) {
                const auto &suppress_popups = demo.suppress_popups;
                ERR_EXIT("WaitMessage() failed on paused demo", "event loop error");
            }
        }

        PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE);
        if (msg.message == WM_QUIT)  // check for a quit message
        {
            done = true;  // if found, quit app
        } else {
            /* Translate and dispatch to event queue*/
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        RedrawWindow(demo.window, nullptr, nullptr, RDW_INTERNALPAINT);
    }

    demo.cleanup();

    return static_cast<int>(msg.wParam);
}

#elif defined(__linux__) || defined(__FreeBSD__)

int main(int argc, char **argv) {
    Demo demo;

    demo.init(argc, argv);

#if defined(VK_USE_PLATFORM_XCB_KHR)
    demo.create_xcb_window();
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
    demo.use_xlib = true;
    demo.create_xlib_window();
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    demo.create_window();
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
    demo.create_directfb_window();
#endif

    demo.init_vk_swapchain();

    demo.prepare();

#if defined(VK_USE_PLATFORM_XCB_KHR)
    demo.run_xcb();
#elif defined(VK_USE_PLATFORM_XLIB_KHR)
    demo.run_xlib();
#elif defined(VK_USE_PLATFORM_WAYLAND_KHR)
    demo.run();
#elif defined(VK_USE_PLATFORM_DIRECTFB_EXT)
    demo.run_directfb();
#elif defined(VK_USE_PLATFORM_DISPLAY_KHR)
    demo.run_display();
#endif

    demo.cleanup();

    return validation_error;
}

#elif defined(VK_USE_PLATFORM_METAL_EXT)

// Global function invoked from NS or UI views and controllers to create demo
static void demo_main(Demo &demo, void *caMetalLayer, int argc, const char *argv[]) {
    demo.init(argc, (char **)argv);
    demo.caMetalLayer = caMetalLayer;
    demo.init_vk_swapchain();
    demo.prepare();
    demo.spin_angle = 0.4f;
}

#else
#error "Platform not supported"
#endif