imgui/examples/example_sdl_vulkan/main.cpp

// dear imgui: standalone example application for SDL2 + Vulkan
// If you are new to dear imgui, see examples/README.txt and documentation 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_XXXX functions and structures are used to interface with imgui_impl_vulkan.cpp/.h.
//   You will use those if you want to use this rendering back-end in your engine/app.
// - Helper ImGui_ImplVulkanH_XXXX functions and structures are only used by this example (main.cpp) and by 
//   the back-end 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_sdl.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>

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

static VkAllocationCallbacks*       g_Allocator = NULL;
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_WindowData g_WindowData;
static uint32_t                     g_MinImageCount = 2;
static bool                         g_WantSwapChainRebuild = false;

static void check_vk_result(VkResult err)
{
    if (err == 0) return;
    printf("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] ObjectType: %i\nMessage: %s\n\n", objectType, pMessage);
    return VK_FALSE;
}
#endif // IMGUI_VULKAN_DEBUG_REPORT

static void SetupVulkan(const char** extensions, uint32_t extensions_count)
{
    VkResult err;

    // Create Vulkan Instance
    {
        VkInstanceCreateInfo create_info = {};
        create_info.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
        create_info.enabledExtensionCount = extensions_count;
        create_info.ppEnabledExtensionNames = extensions;

#ifdef IMGUI_VULKAN_DEBUG_REPORT
        // Enabling multiple validation layers grouped as LunarG standard validation
        const char* layers[] = { "VK_LAYER_LUNARG_standard_validation" };
        create_info.enabledLayerCount = 1;
        create_info.ppEnabledLayerNames = layers;

        // Enable debug report extension (we need additional storage, so we duplicate the user array to add our new extension to it)
        const char** extensions_ext = (const char**)malloc(sizeof(const char*) * (extensions_count + 1));
        memcpy(extensions_ext, extensions, extensions_count * sizeof(const char*));
        extensions_ext[extensions_count] = "VK_EXT_debug_report";
        create_info.enabledExtensionCount = extensions_count + 1;
        create_info.ppEnabledExtensionNames = extensions_ext;

        // Create Vulkan Instance
        err = vkCreateInstance(&create_info, g_Allocator, &g_Instance);
        check_vk_result(err);
        free(extensions_ext);

        // Get the function pointer (required for any extensions)
        auto vkCreateDebugReportCallbackEXT = (PFN_vkCreateDebugReportCallbackEXT)vkGetInstanceProcAddr(g_Instance, "vkCreateDebugReportCallbackEXT");
        IM_ASSERT(vkCreateDebugReportCallbackEXT != NULL);

        // Setup the debug report callback
        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 = NULL;
        err = vkCreateDebugReportCallbackEXT(g_Instance, &debug_report_ci, g_Allocator, &g_DebugReport);
        check_vk_result(err);
#else
        // Create Vulkan Instance without any debug feature
        err = vkCreateInstance(&create_info, g_Allocator, &g_Instance);
        check_vk_result(err);
#endif
    }

    // Select GPU
    {
        uint32_t gpu_count;
        err = vkEnumeratePhysicalDevices(g_Instance, &gpu_count, NULL);
        check_vk_result(err);

        VkPhysicalDevice* gpus = (VkPhysicalDevice*)malloc(sizeof(VkPhysicalDevice) * gpu_count);
        err = vkEnumeratePhysicalDevices(g_Instance, &gpu_count, gpus);
        check_vk_result(err);

        // If a number >1 of GPUs got reported, you should find the best fit GPU for your purpose
        // e.g. VK_PHYSICAL_DEVICE_TYPE_DISCRETE_GPU if available, or with the greatest memory available, etc.
        // for sake of simplicity we'll just take the first one, assuming it has a graphics queue family.
        g_PhysicalDevice = gpus[0];
        free(gpus);
    }

    // Select graphics queue family
    {
        uint32_t count;
        vkGetPhysicalDeviceQueueFamilyProperties(g_PhysicalDevice, &count, NULL);
        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 != -1);
    }

    // Create Logical Device (with 1 queue)
    {
        int device_extension_count = 1;
        const char* device_extensions[] = { "VK_KHR_swapchain" };
        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 = device_extension_count;
        create_info.ppEnabledExtensionNames = device_extensions;
        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);
    }
}

static void SetupVulkanWindowData(ImGui_ImplVulkanH_WindowData* 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.
    ImGui_ImplVulkanH_CreateWindowData(g_PhysicalDevice, g_Device, wd, g_QueueFamily, g_Allocator, width, height, g_MinImageCount);
    IM_ASSERT(wd->FramesQueueSize >= 2);
}

static void CleanupVulkan()
{
    ImGui_ImplVulkanH_WindowData* wd = &g_WindowData;
    ImGui_ImplVulkanH_DestroyWindowData(g_Instance, g_Device, wd, g_Allocator);
    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 FrameRender(ImGui_ImplVulkanH_WindowData* wd)
{
    VkResult err;

    VkSemaphore& image_acquired_semaphore  = wd->Frames[wd->FrameIndex].ImageAcquiredSemaphore;
    err = vkAcquireNextImageKHR(g_Device, wd->Swapchain, UINT64_MAX, image_acquired_semaphore, VK_NULL_HANDLE, &wd->FrameIndex);
    check_vk_result(err);

    ImGui_ImplVulkanH_FrameData* 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 Imgui Draw Data and draw funcs into command buffer
    ImGui_ImplVulkan_RenderDrawData(ImGui::GetDrawData(), 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 = &fd->RenderCompleteSemaphore;

        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_WindowData* wd)
{
    ImGui_ImplVulkanH_FrameData* fd = &wd->Frames[wd->FrameIndex];
    VkPresentInfoKHR info = {};
    info.sType = VK_STRUCTURE_TYPE_PRESENT_INFO_KHR;
    info.waitSemaphoreCount = 1;
    info.pWaitSemaphores = &fd->RenderCompleteSemaphore;
    info.swapchainCount = 1;
    info.pSwapchains = &wd->Swapchain;
    info.pImageIndices = &wd->FrameIndex;
    VkResult err = vkQueuePresentKHR(g_Queue, &info);
    check_vk_result(err);
}

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

    // Setup window
    SDL_DisplayMode current;
    SDL_GetCurrentDisplayMode(0, &current);
    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);

    // Setup Vulkan
    uint32_t extensions_count = 0;
    SDL_Vulkan_GetInstanceExtensions(window, &extensions_count, NULL);
    const char** extensions = new const char*[extensions_count];
    SDL_Vulkan_GetInstanceExtensions(window, &extensions_count, extensions);
    SetupVulkan(extensions, extensions_count);
    delete[] 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_WindowData* wd = &g_WindowData;
    SetupVulkanWindowData(wd, surface, w, h);

    // Setup Dear ImGui context
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

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

    // Setup Platform/Renderer bindings
    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.Allocator = g_Allocator;
    init_info.FramesQueueSize = wd->FramesQueueSize;
    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 NULL. 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.
    // - Read 'misc/fonts/README.txt' 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("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/ProggyTiny.ttf", 10.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != NULL);

    // 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();
    }

    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.
        // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
        // 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_RESIZED && event.window.windowID == SDL_GetWindowID(window))
            {
                g_WindowData.Width = (int)event.window.data1;
                g_WindowData.Height = (int)event.window.data2;
                g_WantSwapChainRebuild = true;
            }
        }

        if (g_WantSwapChainRebuild)
        {
            ImGui_ImplVulkanH_CreateWindowData(g_PhysicalDevice, g_Device, &g_WindowData, g_QueueFamily, g_Allocator, g_WindowData.Width, g_WindowData.Height, g_MinImageCount);
            ImGui_ImplVulkan_SetFramesQueueSize(g_WindowData.FramesQueueSize);
            g_WindowData.FrameIndex = 0;
            g_WantSwapChainRebuild = false;
        }

        // Start the Dear ImGui frame
        ImGui_ImplVulkan_NewFrame();
        ImGui_ImplSDL2_NewFrame(window);
        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 created 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 / ImGui::GetIO().Framerate, ImGui::GetIO().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();
        memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
        FrameRender(wd);

        FramePresent(wd);
    }

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

    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}