// Dear ImGui: standalone example application for Windows API + Vulkan

// Learn about Dear ImGui:
// - FAQ                  https://dearimgui.com/faq
// - Getting Started      https://dearimgui.com/getting-started
// - Documentation        https://dearimgui.com/docs (same as your local docs/ folder).
// - Introduction, links and more at the top of imgui.cpp

// 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_win32.h"
#define VK_USE_PLATFORM_WIN32_KHR
#include "imgui_impl_vulkan.h"
#include <windows.h>
#include <stdio.h>          // printf, fprintf
#include <stdlib.h>         // abort
#include <tchar.h>

// Volk headers
#ifdef IMGUI_IMPL_VULKAN_USE_VOLK
#define VOLK_IMPLEMENTATION
#include <volk.h>
#endif

//#define APP_USE_UNLIMITED_FRAME_RATE
#ifdef _DEBUG
#define APP_USE_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 == VK_SUCCESS)
        return;
    fprintf(stderr, "[vulkan] Error: VkResult = %d\n", err);
    if (err < 0)
        abort();
}

#ifdef APP_USE_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 // APP_USE_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 void SetupVulkan(ImVector<const char*> instance_extensions)
{
    VkResult err;
#ifdef IMGUI_IMPL_VULKAN_USE_VOLK
    volkInitialize();
#endif

    // 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 APP_USE_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);
#ifdef IMGUI_IMPL_VULKAN_USE_VOLK
        volkLoadInstance(g_Instance);
#endif

        // Setup the debug report callback
#ifdef APP_USE_VULKAN_DEBUG_REPORT
        auto f_vkCreateDebugReportCallbackEXT = (PFN_vkCreateDebugReportCallbackEXT)vkGetInstanceProcAddr(g_Instance, "vkCreateDebugReportCallbackEXT");
        IM_ASSERT(f_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 = f_vkCreateDebugReportCallbackEXT(g_Instance, &debug_report_ci, g_Allocator, &g_DebugReport);
        check_vk_result(err);
#endif
    }

    // Select Physical Device (GPU)
    g_PhysicalDevice = ImGui_ImplVulkanH_SelectPhysicalDevice(g_Instance);
    IM_ASSERT(g_PhysicalDevice != VK_NULL_HANDLE);

    // Select graphics queue family
    g_QueueFamily = ImGui_ImplVulkanH_SelectQueueFamilyIndex(g_PhysicalDevice);
    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
    // If you wish to load e.g. additional textures you may need to alter pools sizes and maxSets.
    {
        VkDescriptorPoolSize pool_sizes[] =
        {
            { VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, IMGUI_IMPL_VULKAN_MINIMUM_IMAGE_SAMPLER_POOL_SIZE },
        };
        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 = 0;
        for (VkDescriptorPoolSize& pool_size : pool_sizes)
            pool_info.maxSets += pool_size.descriptorCount;
        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 APP_USE_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, 0);
}

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

#ifdef APP_USE_VULKAN_DEBUG_REPORT
    // Remove the debug report callback
    auto f_vkDestroyDebugReportCallbackEXT = (PFN_vkDestroyDebugReportCallbackEXT)vkGetInstanceProcAddr(g_Instance, "vkDestroyDebugReportCallbackEXT");
    f_vkDestroyDebugReportCallbackEXT(g_Instance, g_DebugReport, g_Allocator);
#endif // APP_USE_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)
{
    VkSemaphore image_acquired_semaphore  = wd->FrameSemaphores[wd->SemaphoreIndex].ImageAcquiredSemaphore;
    VkSemaphore render_complete_semaphore = wd->FrameSemaphores[wd->SemaphoreIndex].RenderCompleteSemaphore;
    VkResult 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;
    if (err == VK_ERROR_OUT_OF_DATE_KHR)
        return;
    if (err != VK_SUBOPTIMAL_KHR)
        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;
    if (err == VK_ERROR_OUT_OF_DATE_KHR)
        return;
    if (err != VK_SUBOPTIMAL_KHR)
        check_vk_result(err);
    wd->SemaphoreIndex = (wd->SemaphoreIndex + 1) % wd->SemaphoreCount; // Now we can use the next set of semaphores
}

LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

// FIXME: This code would ideally be inside imgui_impl_win32.cpp, it would create a dependency on Vulkan headers in imgui_impl_win32.cpp
static int ImGui_ImplWin32_CreateVkSurface(ImGuiViewport* viewport, ImU64 vk_instance, const void* vk_allocator, ImU64* out_vk_surface)
{
    VkWin32SurfaceCreateInfoKHR createInfo = {};
    createInfo.sType = VK_STRUCTURE_TYPE_WIN32_SURFACE_CREATE_INFO_KHR;
    createInfo.hwnd = (HWND)viewport->PlatformHandleRaw;
    createInfo.hinstance = ::GetModuleHandle(nullptr);
    return (int)vkCreateWin32SurfaceKHR((VkInstance)vk_instance, &createInfo, (VkAllocationCallbacks*)vk_allocator, (VkSurfaceKHR*)out_vk_surface);
}

// Main code
int main(int, char**)
{
    // Make process DPI aware and obtain main monitor scale
    ImGui_ImplWin32_EnableDpiAwareness();
    float main_scale = ImGui_ImplWin32_GetDpiScaleForMonitor(::MonitorFromPoint(POINT{ 0, 0 }, MONITOR_DEFAULTTOPRIMARY));

    // Create application window
    WNDCLASSEXW wc = { sizeof(wc), CS_CLASSDC, WndProc, 0L, 0L, GetModuleHandle(nullptr), nullptr, nullptr, nullptr, nullptr, L"ImGui Example", nullptr };
    ::RegisterClassExW(&wc);
    HWND hwnd = ::CreateWindowW(wc.lpszClassName, L"Dear ImGui Win32+Vulkan Example", WS_OVERLAPPEDWINDOW, 100, 100, (int)(1280 * main_scale), (int)(800 * main_scale), nullptr, nullptr, wc.hInstance, nullptr);

    ImVector<const char*> extensions;
    extensions.push_back("VK_KHR_surface");
    extensions.push_back("VK_KHR_win32_surface");
    SetupVulkan(extensions);

    // Create Window Surface
    VkSurfaceKHR surface;
    VkResult err;
    VkWin32SurfaceCreateInfoKHR createInfo = {};
    createInfo.sType = VK_STRUCTURE_TYPE_WIN32_SURFACE_CREATE_INFO_KHR;
    createInfo.hwnd = hwnd;
    createInfo.hinstance = ::GetModuleHandle(nullptr);
    if (vkCreateWin32SurfaceKHR(g_Instance, &createInfo, nullptr, &surface) != VK_SUCCESS)
    {
        printf("Failed to create Vulkan surface.\n");
        return 1;
    }

    // Show the window
    // FIXME: Retrieve client size from window itself.
    ImGui_ImplVulkanH_Window* wd = &g_MainWindowData;
    SetupVulkanWindow(wd, surface, (int)(1280 * main_scale), (int)(800 * main_scale));
    ::ShowWindow(hwnd, SW_SHOWDEFAULT);
    ::UpdateWindow(hwnd);

    // 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();

    // Setup scaling
    ImGuiStyle& style = ImGui::GetStyle();
    style.ScaleAllSizes(main_scale);        // Bake a fixed style scale. (until we have a solution for dynamic style scaling, changing this requires resetting Style + calling this again)
    style.FontScaleDpi = main_scale;        // Set initial font scale. (using io.ConfigDpiScaleFonts=true makes this unnecessary. We leave both here for documentation purpose)
    io.ConfigDpiScaleFonts = true;          // [Experimental] Automatically overwrite style.FontScaleDpi in Begin() when Monitor DPI changes. This will scale fonts but _NOT_ scale sizes/padding for now.
    io.ConfigDpiScaleViewports = true;      // [Experimental] Scale Dear ImGui and Platform Windows when Monitor DPI changes.

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

    // Setup Platform/Renderer backends
    ImGui_ImplWin32_Init(hwnd);
    ImGui::GetPlatformIO().Platform_CreateVkSurface = ImGui_ImplWin32_CreateVkSurface;

    ImGui_ImplVulkan_InitInfo init_info = {};
    //init_info.ApiVersion = VK_API_VERSION_1_3;              // Pass in your value of VkApplicationInfo::apiVersion, otherwise will default to header version.
    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.MinImageCount = g_MinImageCount;
    init_info.ImageCount = wd->ImageCount;
    init_info.Allocator = g_Allocator;
    init_info.PipelineInfoMain.RenderPass = wd->RenderPass;
    init_info.PipelineInfoMain.Subpass = 0;
    init_info.PipelineInfoMain.MSAASamples = VK_SAMPLE_COUNT_1_BIT;
    init_info.CheckVkResultFn = check_vk_result;
    ImGui_ImplVulkan_Init(&init_info);

    // 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).
    // - 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. If you like the default font but want it to scale better, consider using the 'ProggyVector' from the same author!
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //style.FontSizeBase = 20.0f;
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf");
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf");
    //IM_ASSERT(font != nullptr);

    // 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 messages (inputs, window resize, etc.)
        // See the WndProc() function below for our to dispatch events to the Win32 backend.
        MSG msg;
        while (::PeekMessage(&msg, nullptr, 0U, 0U, PM_REMOVE))
        {
            ::TranslateMessage(&msg);
            ::DispatchMessage(&msg);
            if (msg.message == WM_QUIT)
                done = true;
        }
        if (done)
            break;

        // Start the Dear ImGui frame
        ImGui_ImplVulkan_NewFrame();
        ImGui_ImplWin32_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_ImplWin32_Shutdown();
    ImGui::DestroyContext();

    CleanupVulkanWindow();
    CleanupVulkan();

    ::DestroyWindow(hwnd);
    ::UnregisterClassW(wc.lpszClassName, wc.hInstance);

    return 0;
}

// Helper functions

// Forward declare message handler from imgui_impl_win32.cpp
extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

// Win32 message handler
// 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.
LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
        return true;

    switch (msg)
    {
    case WM_SIZE:
        if (g_Device != VK_NULL_HANDLE && wParam != SIZE_MINIMIZED)
        {
            // Resize swap chain
            int fb_width = (UINT)LOWORD(lParam);
            int fb_height = (UINT)HIWORD(lParam);
            if (fb_width > 0 && fb_height > 0 && (g_SwapChainRebuild || g_MainWindowData.Width != fb_width || g_MainWindowData.Height != fb_height))
            {
                ImGui_ImplVulkan_SetMinImageCount(g_MinImageCount);
                ImGui_ImplVulkanH_CreateOrResizeWindow(g_Instance, g_PhysicalDevice, g_Device, &g_MainWindowData, g_QueueFamily, g_Allocator, fb_width, fb_height, g_MinImageCount, 0);
                g_MainWindowData.FrameIndex = 0;
                g_SwapChainRebuild = false;
            }
        }
        return 0;
    case WM_SYSCOMMAND:
        if ((wParam & 0xfff0) == SC_KEYMENU) // Disable ALT application menu
            return 0;
        break;
    case WM_DESTROY:
        ::PostQuitMessage(0);
        return 0;
    }
    return ::DefWindowProcW(hWnd, msg, wParam, lParam);
}
