ImGui minimal vulkan + glfw integration

imguivulkanminimal.cpp

struct ImGuiBackend
{
    ImGuiContext* imguiCtx = {};
    ImGuiContext* lastImguiCtx = {};

    Context* ctx = {};
    VkRenderPass renderPass = {};
    std::vector<VkFramebuffer> framebuffers;
    VkDescriptorPool descriptorPool = {};
    VkSwapchainKHR lastSwapchain = {};
public:
    void Init(Context& ctx, Swapchain& swapchain, GLFWwindow* window, int imguiFlags);
    void BeginFrame();
    void EndFrame(Swapchain& swapchain);
};

// ---------------------------------------------------------------------------------------

void ImGuiBackend::Init(Context& _ctx, Swapchain& swapchain, GLFWwindow* window, int imguiFlags)
{
    ctx = &_ctx;

    VkCall(vkCreateRenderPass(ctx->device, Temp(VkRenderPassCreateInfo {
        .sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO,
        .attachmentCount = 1,
        .pAttachments = Temp(VkAttachmentDescription {
            .format = swapchain.format.format,
            .samples = VK_SAMPLE_COUNT_1_BIT,
            .loadOp = VK_ATTACHMENT_LOAD_OP_LOAD,
            .storeOp = VK_ATTACHMENT_STORE_OP_STORE,
            .stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE,
            .stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE,
            .initialLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
            .finalLayout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
        }),
        .subpassCount = 1,
        .pSubpasses = Temp(VkSubpassDescription {
            .pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS,
            .colorAttachmentCount = 1,
            .pColorAttachments = Temp(VkAttachmentReference {
                .attachment = 0,
                .layout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
            }),
        }),
        .dependencyCount = 1,
        .pDependencies = Temp(VkSubpassDependency {
            .srcSubpass = VK_SUBPASS_EXTERNAL,
            .srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT,
            .dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT,
            .srcAccessMask = 0,
            .dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT,
        }),
    }), nullptr, &renderPass));

    // Create fixed sampler only descriptor pool for ImGui
    // All application descriptor sets will be managed by descriptor buffers

    constexpr u32 MaxSamplers = 65'536;
    VkCall(vkCreateDescriptorPool(ctx->device, Temp(VkDescriptorPoolCreateInfo {
        .sType = VK_STRUCTURE_TYPE_DESCRIPTOR_POOL_CREATE_INFO,
        .flags = VK_DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT,
        .maxSets = MaxSamplers,
        .poolSizeCount = 1,
        .pPoolSizes = Temp(VkDescriptorPoolSize { VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER, MaxSamplers }),
    }), nullptr, &descriptorPool));

    // Create ImGui context and initialize

    imguiCtx = ImGui::CreateContext();
    lastImguiCtx = ImGui::GetCurrentContext();
    ImGui::SetCurrentContext(imguiCtx);

    auto& io = ImGui::GetIO();
    io.ConfigFlags |= imguiFlags;
    ImGui_ImplGlfw_InitForVulkan(window, true);
    ImGui_ImplVulkan_Init(Temp(ImGui_ImplVulkan_InitInfo {
        .Instance = ctx->instance,
        .PhysicalDevice = ctx->gpu,
        .Device = ctx->device,
        .QueueFamily = ctx->queueFamily,
        .Queue = ctx->queue,
        .DescriptorPool = descriptorPool,
        .Subpass = 0,
        .MinImageCount = 2,
        .ImageCount = 2,
        .CheckVkResultFn = [](VkResult r) { VkCall(r); },
    }), renderPass);

    // Rescale UI and fonts
    // TODO: Don't hardcode 150%

    ImGui::GetStyle().ScaleAllSizes(1.5f);
    auto fontConfig = ImFontConfig();
    fontConfig.GlyphOffset = ImVec2(1.f, 1.67f);
    ImGui::GetIO().Fonts->ClearFonts();
    ImGui::GetIO().Fonts->AddFontFromFileTTF("assets/fonts/CONSOLA.TTF", 20, &fontConfig);
    ImGui_ImplVulkan_CreateFontsTexture(ctx->cmd);
    ctx->Flush();

    ImGui::SetCurrentContext(lastImguiCtx);
}

void ImGuiBackend::BeginFrame()
{
    lastImguiCtx = ImGui::GetCurrentContext();
    ImGui::SetCurrentContext(imguiCtx);

    ImGui_ImplVulkan_NewFrame();
    ImGui_ImplGlfw_NewFrame();
    ImGui::NewFrame();

    if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DockingEnable)
    {
        ImGuiDockNodeFlags dockspaceFlags = 0;
        ImGuiWindowFlags windowFlags = 0;

        // TODO: More configuration

        // Make dockspace fullscreen
        auto viewport = ImGui::GetMainViewport();
        ImGui::SetNextWindowPos(viewport->WorkPos);
        ImGui::SetNextWindowSize(viewport->WorkSize);
        ImGui::SetNextWindowViewport(viewport->ID);
        ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.f);
        ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.f);
        ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.f, 0.f));
        windowFlags |= ImGuiWindowFlags_NoTitleBar
            | ImGuiWindowFlags_NoCollapse
            | ImGuiWindowFlags_NoResize
            | ImGuiWindowFlags_NoMove
            | ImGuiWindowFlags_NoBringToFrontOnFocus
            | ImGuiWindowFlags_NoNavFocus;

        // Pass through background
        windowFlags |= ImGuiWindowFlags_NoBackground;
        dockspaceFlags |= ImGuiDockNodeFlags_PassthruCentralNode;

        // Register dockspace
        ImGui::Begin("Dockspace", Temp(true), windowFlags);
        ImGui::PopStyleVar(3);
        ImGui::DockSpace(ImGui::GetID("DockspaceID"), ImVec2(0.f, 0.f), dockspaceFlags);
        ImGui::End();
    }
}

void ImGuiBackend::EndFrame(Swapchain& swapchain)
{
    ImGui::Render();

    if (lastSwapchain != swapchain.swapchain)
    {
        lastSwapchain = swapchain.swapchain;

        framebuffers.resize(swapchain.images.size());
        for (pyr::u32 i = 0; i < swapchain.images.size(); ++i)
        {
            vkDestroyFramebuffer(ctx->device, framebuffers[i], nullptr);
            pyr::VkCall(vkCreateFramebuffer(ctx->device, pyr::Temp(VkFramebufferCreateInfo {
                .sType = VK_STRUCTURE_TYPE_FRAMEBUFFER_CREATE_INFO,
                .renderPass = renderPass,
                .attachmentCount = 1,
                .pAttachments = &swapchain.images[i].view,
                .width = swapchain.extent.width,
                .height = swapchain.extent.height,
                .layers = 1,
            }), nullptr, &framebuffers[i]));
        }
    }

    ctx->Transition(ctx->cmd, *swapchain.image, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL);
    vkCmdBeginRenderPass(ctx->cmd, pyr::Temp(VkRenderPassBeginInfo {
        .sType = VK_STRUCTURE_TYPE_RENDER_PASS_BEGIN_INFO,
        .renderPass = renderPass,
        .framebuffer = framebuffers[swapchain.index],
        .renderArea = { {}, swapchain.extent },
    }), VK_SUBPASS_CONTENTS_INLINE);
    ImGui_ImplVulkan_RenderDrawData(ImGui::GetDrawData(), ctx->cmd);
    vkCmdEndRenderPass(ctx->cmd);

    if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        auto contextBackup = glfwGetCurrentContext();
        ImGui::UpdatePlatformWindows();
        ImGui::RenderPlatformWindowsDefault();
        glfwMakeContextCurrent(contextBackup);
    }

    ImGui::SetCurrentContext(lastImguiCtx);
}