imgui/examples/example_sdl2_vulkan/main.cpp

// Dear ImGui: standalone example application for SDL2 + Vulkan
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

// Important note to the reader who wish to integrate imgui_impl_vulkan.cpp/.h in their own engine/app.
// - Common ImGui_ImplVulkan_XXX functions and structures are used to interface with imgui_impl_vulkan.cpp/.h.
//   You will use those if you want to use this rendering backend in your engine/app.
// - Helper ImGui_ImplVulkanH_XXX functions and structures are only used by this example (main.cpp) and by
//   the backend itself (imgui_impl_vulkan.cpp), but should PROBABLY NOT be used by your own engine/app code.
// Read comments in imgui_impl_vulkan.h.

#include "imgui.h"
#include "imgui_impl_sdl2.h"
#include "imgui_impl_vulkan.h"
#include <stdio.h>          // printf, fprintf
#include <stdlib.h>         // abort
#include <SDL.h>
#include <SDL_vulkan.h>
#include <vulkan/vulkan.h>
//#include <vulkan/vulkan_beta.h>

//#define IMGUI_UNLIMITED_FRAME_RATE
#ifdef _DEBUG
#define IMGUI_VULKAN_DEBUG_REPORT
#endif

// Data
static VkAllocationCallbacks*   g_Allocator = nullptr;
static VkInstance               g_Instance = VK_NULL_HANDLE;
static VkPhysicalDevice         g_PhysicalDevice = VK_NULL_HANDLE;
static VkDevice                 g_Device = VK_NULL_HANDLE;
static uint32_t                 g_QueueFamily = (uint32_t)-1;
static VkQueue                  g_Queue = VK_NULL_HANDLE;
static VkDebugReportCallbackEXT g_DebugReport = VK_NULL_HANDLE;
static VkPipelineCache          g_PipelineCache = VK_NULL_HANDLE;
static VkDescriptorPool         g_DescriptorPool = VK_NULL_HANDLE;

static ImGui_ImplVulkanH_Window g_MainWindowData;
static uint32_t                 g_MinImageCount = 2;
static bool                     g_SwapChainRebuild = false;

static void check_vk_result(VkResult err)
{
    if (err == 0)
        return;
    fprintf(stderr, "[vulkan] Error: VkResult = %d\n", err);
    if (err < 0)
        abort();
}

#ifdef IMGUI_VULKAN_DEBUG_REPORT
static VKAPI_ATTR VkBool32 VKAPI_CALL debug_report(VkDebugReportFlagsEXT flags, VkDebugReportObjectTypeEXT objectType, uint64_t object, size_t location, int32_t messageCode, const char* pLayerPrefix, const char* pMessage, void* pUserData)
{
    (void)flags; (void)object; (void)location; (void)messageCode; (void)pUserData; (void)pLayerPrefix; // Unused arguments
    fprintf(stderr, "[vulkan] Debug report from ObjectType: %i\nMessage: %s\n\n", objectType, pMessage);
    return VK_FALSE;
}
#endif // IMGUI_VULKAN_DEBUG_REPORT

static bool IsExtensionAvailable(const ImVector<VkExtensionProperties>& properties, const char* extension)
{
    for (const VkExtensionProperties& p : properties)
        if (strcmp(p.extensionName, extension) == 0)
            return true;
    return false;
}

static VkPhysicalDevice SetupVulkan_SelectPhysicalDevice()
{
    uint32_t gpu_count;
    VkResult err = vkEnumeratePhysicalDevices(g_Instance, &gpu_count, nullptr);
    check_vk_result(err);
    IM_ASSERT(gpu_count > 0);

    ImVector<VkPhysicalDevice> gpus;
    gpus.resize(gpu_count);
    err = vkEnumeratePhysicalDevices(g_Instance, &gpu_count, gpus.Data);
    check_vk_result(err);

    // If a number >1 of GPUs got reported, find discrete GPU if present, or use first one available. This covers
    // most common cases (multi-gpu/integrated+dedicated graphics). Handling more complicated setups (multiple
    // dedicated GPUs) is out of scope of this sample.
    for (VkPhysicalDevice& device : gpus)
    {
        VkPhysicalDeviceProperties properties;
        vkGetPhysicalDeviceProperties(device, &properties);
        if (properties.deviceType == VK_PHYSICAL_DEVICE_TYPE_DISCRETE_GPU)
            return device;
    }

    // Use first GPU (Integrated) is a Discrete one is not available.
    if (gpu_count > 0)
        return gpus[0];
    return VK_NULL_HANDLE;
}

static void SetupVulkan(ImVector<const char*> instance_extensions)
{
    VkResult err;

    // Create Vulkan Instance
    {
        VkInstanceCreateInfo create_info = {};
        create_info.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;

        // Enumerate available extensions
        uint32_t properties_count;
        ImVector<VkExtensionProperties> properties;
        vkEnumerateInstanceExtensionProperties(nullptr, &properties_count, nullptr);
        properties.resize(properties_count);
        err = vkEnumerateInstanceExtensionProperties(nullptr, &properties_count, properties.Data);
        check_vk_result(err);

        // Enable required extensions
        if (IsExtensionAvailable(properties, VK_KHR_GET_PHYSICAL_DEVICE_PROPERTIES_2_EXTENSION_NAME))
            instance_extensions.push_back(VK_KHR_GET_PHYSICAL_DEVICE_PROPERTIES_2_EXTENSION_NAME);
#ifdef VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME
        if (IsExtensionAvailable(properties, VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME))
        {
            instance_extensions.push_back(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME);
            create_info.flags |= VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR;
        }
#endif

        // Enabling validation layers
#ifdef IMGUI_VULKAN_DEBUG_REPORT
        const char* layers[] = { "VK_LAYER_KHRONOS_validation" };
        create_info.enabledLayerCount = 1;
        create_info.ppEnabledLayerNames = layers;
        instance_extensions.push_back("VK_EXT_debug_report");
#endif

        // Create Vulkan Instance
        create_info.enabledExtensionCount = (uint32_t)instance_extensions.Size;
        create_info.ppEnabledExtensionNames = instance_extensions.Data;
        err = vkCreateInstance(&create_info, g_Allocator, &g_Instance);
        check_vk_result(err);

        // Setup the debug report callback
#ifdef IMGUI_VULKAN_DEBUG_REPORT
        auto vkCreateDebugReportCallbackEXT = (PFN_vkCreateDebugReportCallbackEXT)vkGetInstanceProcAddr(g_Instance, "vkCreateDebugReportCallbackEXT");
        IM_ASSERT(vkCreateDebugReportCallbackEXT != nullptr);
        VkDebugReportCallbackCreateInfoEXT debug_report_ci = {};
        debug_report_ci.sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT;
        debug_report_ci.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT | VK_DEBUG_REPORT_WARNING_BIT_EXT | VK_DEBUG_REPORT_PERFORMANCE_WARNING_BIT_EXT;
        debug_report_ci.pfnCallback = debug_report;
        debug_report_ci.pUserData = nullptr;
        err = vkCreateDebugReportCallbackEXT(g_Instance, &debug_report_ci, g_Allocator, &g_DebugReport);
        check_vk_result(err);
#endif
    }

    // Select Physical Device (GPU)
    g_PhysicalDevice = SetupVulkan_SelectPhysicalDevice();

    // Select graphics queue family
    {
        uint32_t count;
        vkGetPhysicalDeviceQueueFamilyProperties(g_PhysicalDevice, &count, nullptr);
        VkQueueFamilyProperties* queues = (VkQueueFamilyProperties*)malloc(sizeof(VkQueueFamilyProperties) * count);
        vkGetPhysicalDeviceQueueFamilyProperties(g_PhysicalDevice, &count, queues);
        for (uint32_t i = 0; i < count; i++)
            if (queues[i].queueFlags & VK_QUEUE_GRAPHICS_BIT)
            {
                g_QueueFamily = i;
                break;
            }
        free(queues);
        IM_ASSERT(g_QueueFamily != (uint32_t)-1);
    }

    // Create Logical Device (with 1 queue)
    {
        ImVector<const char*> device_extensions;
        device_extensions.push_back("VK_KHR_swapchain");

        // Enumerate physical device extension
        uint32_t properties_count;
        ImVector<VkExtensionProperties> properties;
        vkEnumerateDeviceExtensionProperties(g_PhysicalDevice, nullptr, &properties_count, nullptr);
        properties.resize(properties_count);
        vkEnumerateDeviceExtensionProperties(g_PhysicalDevice, nullptr, &properties_count, properties.Data);
#ifdef VK_KHR_PORTABILITY_SUBSET_EXTENSION_NAME
        if (IsExtensionAvailable(properties, VK_KHR_PORTABILITY_SUBSET_EXTENSION_NAME))
            device_extensions.push_back(VK_KHR_PORTABILITY_SUBSET_EXTENSION_NAME);
#endif

        const float queue_priority[] = { 1.0f };
        VkDeviceQueueCreateInfo queue_info[1] = {};
        queue_info[0].sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
        queue_info[0].queueFamilyIndex = g_QueueFamily;
        queue_info[0].queueCount = 1;
        queue_info[0].pQueuePriorities = queue_priority;
        VkDeviceCreateInfo create_info = {};
        create_info.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
        create_info.queueCreateInfoCount = sizeof(queue_info) / sizeof(queue_info[0]);
        create_info.pQueueCreateInfos = queue_info;
        create_info.enabledExtensionCount = (uint32_t)device_extensions.Size;
        create_info.ppEnabledExtensionNames = device_extensions.Data;
        err = vkCreateDevice(g_PhysicalDevice, &create_info, g_Allocator, &g_Device);
        check_vk_result(err);
        vkGetDeviceQueue(g_Device, g_QueueFamily, 0, &g_Queue);
    }

    // Create Descriptor Pool
    {
        VkDescriptorPoolSize pool_sizes[] =
        {
            { VK_DESCRIPTOR_TYPE_SAMPLER, 1000 },
            { VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, 1000 },
            { VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, 1000 },
            { VK_DESCRIPTOR_TYPE_STORAGE_IMAGE, 1000 },
            { VK_DESCRIPTOR_TYPE_UNIFORM_TEXEL_BUFFER, 1000 },
            { VK_DESCRIPTOR_TYPE_STORAGE_TEXEL_BUFFER, 1000 },
            { VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER, 1000 },
            { VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, 1000 },
            { VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC, 1000 },
            { VK_DESCRIPTOR_TYPE_STORAGE_BUFFER_DYNAMIC, 1000 },
            { VK_DESCRIPTOR_TYPE_INPUT_ATTACHMENT, 1000 }
        };
        VkDescriptorPoolCreateInfo pool_info = {};
        pool_info.sType = VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_CREATE_INFO;
        pool_info.flags = VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT;
        pool_info.maxSets = 1000 * IM_ARRAYSIZE(pool_sizes);
        pool_info.poolSizeCount = (uint32_t)IM_ARRAYSIZE(pool_sizes);
        pool_info.pPoolSizes = pool_sizes;
        err = vkCreateDescriptorPool(g_Device, &pool_info, g_Allocator, &g_DescriptorPool);
        check_vk_result(err);
    }
}

// All the ImGui_ImplVulkanH_XXX structures/functions are optional helpers used by the demo.
// Your real engine/app may not use them.
static void SetupVulkanWindow(ImGui_ImplVulkanH_Window* wd, VkSurfaceKHR surface, int width, int height)
{
    wd->Surface = surface;

    // Check for WSI support
    VkBool32 res;
    vkGetPhysicalDeviceSurfaceSupportKHR(g_PhysicalDevice, g_QueueFamily, wd->Surface, &res);
    if (res != VK_TRUE)
    {
        fprintf(stderr, "Error no WSI support on physical device 0\n");
        exit(-1);
    }

    // Select Surface Format
    const VkFormat requestSurfaceImageFormat[] = { VK_FORMAT_B8G8R8A8_UNORM, VK_FORMAT_R8G8B8A8_UNORM, VK_FORMAT_B8G8R8_UNORM, VK_FORMAT_R8G8B8_UNORM };
    const VkColorSpaceKHR requestSurfaceColorSpace = VK_COLORSPACE_SRGB_NONLINEAR_KHR;
    wd->SurfaceFormat = ImGui_ImplVulkanH_SelectSurfaceFormat(g_PhysicalDevice, wd->Surface, requestSurfaceImageFormat, (size_t)IM_ARRAYSIZE(requestSurfaceImageFormat), requestSurfaceColorSpace);

    // Select Present Mode
#ifdef IMGUI_UNLIMITED_FRAME_RATE
    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_MAILBOX_KHR, VK_PRESENT_MODE_IMMEDIATE_KHR, VK_PRESENT_MODE_FIFO_KHR };
#else
    VkPresentModeKHR present_modes[] = { VK_PRESENT_MODE_FIFO_KHR };
#endif
    wd->PresentMode = ImGui_ImplVulkanH_SelectPresentMode(g_PhysicalDevice, wd->Surface, &present_modes[0], IM_ARRAYSIZE(present_modes));
    //printf("[vulkan] Selected PresentMode = %d\n", wd->PresentMode);

    // Create SwapChain, RenderPass, Framebuffer, etc.
    IM_ASSERT(g_MinImageCount >= 2);
    ImGui_ImplVulkanH_CreateOrResizeWindow(g_Instance, g_PhysicalDevice, g_Device, wd, g_QueueFamily, g_Allocator, width, height, g_MinImageCount);
}

static void CleanupVulkan()
{
    vkDestroyDescriptorPool(g_Device, g_DescriptorPool, g_Allocator);

#ifdef IMGUI_VULKAN_DEBUG_REPORT
    // Remove the debug report callback
    auto vkDestroyDebugReportCallbackEXT = (PFN_vkDestroyDebugReportCallbackEXT)vkGetInstanceProcAddr(g_Instance, "vkDestroyDebugReportCallbackEXT");
    vkDestroyDebugReportCallbackEXT(g_Instance, g_DebugReport, g_Allocator);
#endif // IMGUI_VULKAN_DEBUG_REPORT

    vkDestroyDevice(g_Device, g_Allocator);
    vkDestroyInstance(g_Instance, g_Allocator);
}

static void CleanupVulkanWindow()
{
    ImGui_ImplVulkanH_DestroyWindow(g_Instance, g_Device, &g_MainWindowData, g_Allocator);
}

static void FrameRender(ImGui_ImplVulkanH_Window* wd, ImDrawData* draw_data)
{
    VkResult err;

    VkSemaphore image_acquired_semaphore  = wd->FrameSemaphores[wd->SemaphoreIndex].ImageAcquiredSemaphore;
    VkSemaphore render_complete_semaphore = wd->FrameSemaphores[wd->SemaphoreIndex].RenderCompleteSemaphore;
    err = vkAcquireNextImageKHR(g_Device, wd->Swapchain, UINT64_MAX, image_acquired_semaphore, VK_NULL_HANDLE, &wd->FrameIndex);
    if (err == VK_ERROR_OUT_OF_DATE_KHR || err == VK_SUBOPTIMAL_KHR)
    {
        g_SwapChainRebuild = true;
        return;
    }
    check_vk_result(err);

    ImGui_ImplVulkanH_Frame* fd = &wd->Frames[wd->FrameIndex];
    {
        err = vkWaitForFences(g_Device, 1, &fd->Fence, VK_TRUE, UINT64_MAX);    // wait indefinitely instead of periodically checking
        check_vk_result(err);

        err = vkResetFences(g_Device, 1, &fd->Fence);
        check_vk_result(err);
    }
    {
        err = vkResetCommandPool(g_Device, fd->CommandPool, 0);
        check_vk_result(err);
        VkCommandBufferBeginInfo info = {};
        info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
        info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
        err = vkBeginCommandBuffer(fd->CommandBuffer, &info);
        check_vk_result(err);
    }
    {
        VkRenderPassBeginInfo info = {};
        info.sType = VK_STRUCTURE_TYPE_RENDER_PASS_BEGIN_INFO;
        info.renderPass = wd->RenderPass;
        info.framebuffer = fd->Framebuffer;
        info.renderArea.extent.width = wd->Width;
        info.renderArea.extent.height = wd->Height;
        info.clearValueCount = 1;
        info.pClearValues = &wd->ClearValue;
        vkCmdBeginRenderPass(fd->CommandBuffer, &info, VK_SUBPASS_CONTENTS_INLINE);
    }

    // Record dear imgui primitives into command buffer
    ImGui_ImplVulkan_RenderDrawData(draw_data, fd->CommandBuffer);

    // Submit command buffer
    vkCmdEndRenderPass(fd->CommandBuffer);
    {
        VkPipelineStageFlags wait_stage = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
        VkSubmitInfo info = {};
        info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
        info.waitSemaphoreCount = 1;
        info.pWaitSemaphores = &image_acquired_semaphore;
        info.pWaitDstStageMask = &wait_stage;
        info.commandBufferCount = 1;
        info.pCommandBuffers = &fd->CommandBuffer;
        info.signalSemaphoreCount = 1;
        info.pSignalSemaphores = &render_complete_semaphore;

        err = vkEndCommandBuffer(fd->CommandBuffer);
        check_vk_result(err);
        err = vkQueueSubmit(g_Queue, 1, &info, fd->Fence);
        check_vk_result(err);
    }
}

static void FramePresent(ImGui_ImplVulkanH_Window* wd)
{
    if (g_SwapChainRebuild)
        return;
    VkSemaphore render_complete_semaphore = wd->FrameSemaphores[wd->SemaphoreIndex].RenderCompleteSemaphore;
    VkPresentInfoKHR info = {};
    info.sType = VK_STRUCTURE_TYPE_PRESENT_INFO_KHR;
    info.waitSemaphoreCount = 1;
    info.pWaitSemaphores = &render_complete_semaphore;
    info.swapchainCount = 1;
    info.pSwapchains = &wd->Swapchain;
    info.pImageIndices = &wd->FrameIndex;
    VkResult err = vkQueuePresentKHR(g_Queue, &info);
    if (err == VK_ERROR_OUT_OF_DATE_KHR || err == VK_SUBOPTIMAL_KHR)
    {
        g_SwapChainRebuild = true;
        return;
    }
    check_vk_result(err);
    wd->SemaphoreIndex = (wd->SemaphoreIndex + 1) % wd->ImageCount; // Now we can use the next set of semaphores
}

// Main code
int main(int, char**)
{
    // Setup SDL
    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0)
    {
        printf("Error: %s\n", SDL_GetError());
        return -1;
    }

    // From 2.0.18: Enable native IME.
#ifdef SDL_HINT_IME_SHOW_UI
    SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
#endif

    // Create window with Vulkan graphics context
    SDL_WindowFlags window_flags = (SDL_WindowFlags)(SDL_WINDOW_VULKAN | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2+Vulkan example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, window_flags);

    ImVector<const char*> extensions;
    uint32_t extensions_count = 0;
    SDL_Vulkan_GetInstanceExtensions(window, &extensions_count, nullptr);
    extensions.resize(extensions_count);
    SDL_Vulkan_GetInstanceExtensions(window, &extensions_count, extensions.Data);
    SetupVulkan(extensions);

    // Create Window Surface
    VkSurfaceKHR surface;
    VkResult err;
    if (SDL_Vulkan_CreateSurface(window, g_Instance, &surface) == 0)
    {
        printf("Failed to create Vulkan surface.\n");
        return 1;
    }

    // Create Framebuffers
    int w, h;
    SDL_GetWindowSize(window, &w, &h);
    ImGui_ImplVulkanH_Window* wd = &g_MainWindowData;
    SetupVulkanWindow(wd, surface, w, h);

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoTaskBarIcons;
    //io.ConfigFlags |= ImGuiConfigFlags_ViewportsNoMerge;

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();
    //ImGui::StyleColorsLight();

    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
    ImGuiStyle& style = ImGui::GetStyle();
    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        style.WindowRounding = 0.0f;
        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
    }

    // Setup Platform/Renderer backends
    ImGui_ImplSDL2_InitForVulkan(window);
    ImGui_ImplVulkan_InitInfo init_info = {};
    init_info.Instance = g_Instance;
    init_info.PhysicalDevice = g_PhysicalDevice;
    init_info.Device = g_Device;
    init_info.QueueFamily = g_QueueFamily;
    init_info.Queue = g_Queue;
    init_info.PipelineCache = g_PipelineCache;
    init_info.DescriptorPool = g_DescriptorPool;
    init_info.Subpass = 0;
    init_info.MinImageCount = g_MinImageCount;
    init_info.ImageCount = wd->ImageCount;
    init_info.MSAASamples = VK_SAMPLE_COUNT_1_BIT;
    init_info.Allocator = g_Allocator;
    init_info.CheckVkResultFn = check_vk_result;
    ImGui_ImplVulkan_Init(&init_info, wd->RenderPass);

    // Load Fonts
    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
    // - If the file cannot be loaded, the function will return a nullptr. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
    // - Use '#define IMGUI_ENABLE_FREETYPE' in your imconfig file to use Freetype for higher quality font rendering.
    // - Read 'docs/FONTS.md' for more instructions and details.
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf", 18.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, nullptr, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != nullptr);

    // Upload Fonts
    {
        // Use any command queue
        VkCommandPool command_pool = wd->Frames[wd->FrameIndex].CommandPool;
        VkCommandBuffer command_buffer = wd->Frames[wd->FrameIndex].CommandBuffer;

        err = vkResetCommandPool(g_Device, command_pool, 0);
        check_vk_result(err);
        VkCommandBufferBeginInfo begin_info = {};
        begin_info.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
        begin_info.flags |= VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT;
        err = vkBeginCommandBuffer(command_buffer, &begin_info);
        check_vk_result(err);

        ImGui_ImplVulkan_CreateFontsTexture(command_buffer);

        VkSubmitInfo end_info = {};
        end_info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
        end_info.commandBufferCount = 1;
        end_info.pCommandBuffers = &command_buffer;
        err = vkEndCommandBuffer(command_buffer);
        check_vk_result(err);
        err = vkQueueSubmit(g_Queue, 1, &end_info, VK_NULL_HANDLE);
        check_vk_result(err);

        err = vkDeviceWaitIdle(g_Device);
        check_vk_result(err);
        ImGui_ImplVulkan_DestroyFontUploadObjects();
    }

    // Our state
    bool show_demo_window = true;
    bool show_another_window = false;
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // Main loop
    bool done = false;
    while (!done)
    {
        // Poll and handle events (inputs, window resize, etc.)
        // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
        // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application, or clear/overwrite your copy of the mouse data.
        // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application, or clear/overwrite your copy of the keyboard data.
        // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
        SDL_Event event;
        while (SDL_PollEvent(&event))
        {
            ImGui_ImplSDL2_ProcessEvent(&event);
            if (event.type == SDL_QUIT)
                done = true;
            if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
                done = true;
        }

        // Resize swap chain?
        if (g_SwapChainRebuild)
        {
            int width, height;
            SDL_GetWindowSize(window, &width, &height);
            if (width > 0 && height > 0)
            {
                ImGui_ImplVulkan_SetMinImageCount(g_MinImageCount);
                ImGui_ImplVulkanH_CreateOrResizeWindow(g_Instance, g_PhysicalDevice, g_Device, &g_MainWindowData, g_QueueFamily, g_Allocator, width, height, g_MinImageCount);
                g_MainWindowData.FrameIndex = 0;
                g_SwapChainRebuild = false;
            }
        }

        // Start the Dear ImGui frame
        ImGui_ImplVulkan_NewFrame();
        ImGui_ImplSDL2_NewFrame();
        ImGui::NewFrame();

        // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
        if (show_demo_window)
            ImGui::ShowDemoWindow(&show_demo_window);

        // 2. Show a simple window that we create ourselves. We use a Begin/End pair to create a named window.
        {
            static float f = 0.0f;
            static int counter = 0;

            ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.

            ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
            ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
            ImGui::Checkbox("Another Window", &show_another_window);

            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

            if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                counter++;
            ImGui::SameLine();
            ImGui::Text("counter = %d", counter);

            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
            ImGui::End();
        }

        // 3. Show another simple window.
        if (show_another_window)
        {
            ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
            ImGui::Text("Hello from another window!");
            if (ImGui::Button("Close Me"))
                show_another_window = false;
            ImGui::End();
        }

        // Rendering
        ImGui::Render();
        ImDrawData* main_draw_data = ImGui::GetDrawData();
        const bool main_is_minimized = (main_draw_data->DisplaySize.x <= 0.0f || main_draw_data->DisplaySize.y <= 0.0f);
        wd->ClearValue.color.float32[0] = clear_color.x * clear_color.w;
        wd->ClearValue.color.float32[1] = clear_color.y * clear_color.w;
        wd->ClearValue.color.float32[2] = clear_color.z * clear_color.w;
        wd->ClearValue.color.float32[3] = clear_color.w;
        if (!main_is_minimized)
            FrameRender(wd, main_draw_data);

        // Update and Render additional Platform Windows
        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
        {
            ImGui::UpdatePlatformWindows();
            ImGui::RenderPlatformWindowsDefault();
        }

        // Present Main Platform Window
        if (!main_is_minimized)
            FramePresent(wd);
    }

    // Cleanup
    err = vkDeviceWaitIdle(g_Device);
    check_vk_result(err);
    ImGui_ImplVulkan_Shutdown();
    ImGui_ImplSDL2_Shutdown();
    ImGui::DestroyContext();

    CleanupVulkanWindow();
    CleanupVulkan();

    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}