main.cpp

// Dear ImGui: standalone example application for SDL3 + SDL_GPU

// 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_sdlgpu3.cpp/.h in their own engine/app.
// - Unlike other backends, the user must call the function Imgui_ImplSDLGPU_PrepareDrawData() BEFORE issuing a SDL_GPURenderPass containing ImGui_ImplSDLGPU_RenderDrawData.
//   Calling the function is MANDATORY, otherwise the ImGui will not upload neither the vertex nor the index buffer for the GPU. See imgui_impl_sdlgpu3.cpp for more info.

#include "imgui.h"
#include "imgui_impl_sdl3.h"
#include "imgui_impl_sdlgpu3.h"
#include <stdio.h>          // printf, fprintf
#include <stdlib.h>         // abort
#include <SDL3/SDL.h>

// This example doesn't compile with Emscripten yet! Awaiting SDL3 support.
#ifdef __EMSCRIPTEN__
#include "../libs/emscripten/emscripten_mainloop_stub.h"
#endif

// Main code
int main(int, char**)
{
    // Setup SDL
    // [If using SDL_MAIN_USE_CALLBACKS: all code below until the main loop starts would likely be your SDL_AppInit() function]
    if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMEPAD))
    {
        printf("Error: SDL_Init(): %s\n", SDL_GetError());
        return -1;
    }

    // Create SDL window graphics context
    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL3+SDL_GPU example", 1280, 720, SDL_WINDOW_RESIZABLE | SDL_WINDOW_HIGH_PIXEL_DENSITY);
    if (window == nullptr)
    {
        printf("Error: SDL_CreateWindow(): %s\n", SDL_GetError());
        return -1;
    }

    // Create GPU Device
    SDL_GPUDevice* gpu_device = SDL_CreateGPUDevice(SDL_GPU_SHADERFORMAT_SPIRV | SDL_GPU_SHADERFORMAT_DXIL | SDL_GPU_SHADERFORMAT_METALLIB,true,nullptr);
    if (gpu_device == nullptr)
    {
        printf("Error: SDL_CreateGPUDevice(): %s\n", SDL_GetError());
        return -1;
    }

    // Claim window for GPU Device
    if (!SDL_ClaimWindowForGPUDevice(gpu_device, window))
    {
        printf("Error: SDL_ClaimWindowForGPUDevice(): %s\n", SDL_GetError());
        return -1;
    }
    SDL_SetGPUSwapchainParameters(gpu_device, window, SDL_GPU_SWAPCHAINCOMPOSITION_SDR, SDL_GPU_PRESENTMODE_MAILBOX);

    // 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

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

    // Setup Platform/Renderer backends
    ImGui_ImplSDL3_InitForSDLGPU(window);
    ImGui_ImplSDLGPU3_InitInfo init_info = {};
    init_info.Device = gpu_device;
    init_info.ColorTargetFormat = SDL_GetGPUSwapchainTextureFormat(gpu_device, window);
    init_info.MSAASamples = SDL_GPU_SAMPLECOUNT_1;
    ImGui_ImplSDLGPU3_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).
    // - 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);

    // 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.
        // [If using SDL_MAIN_USE_CALLBACKS: call ImGui_ImplSDL3_ProcessEvent() from your SDL_AppEvent() function]
        SDL_Event event;
        while (SDL_PollEvent(&event))
        {
            ImGui_ImplSDL3_ProcessEvent(&event);
            if (event.type == SDL_EVENT_QUIT)
                done = true;
            if (event.type == SDL_EVENT_WINDOW_CLOSE_REQUESTED && event.window.windowID == SDL_GetWindowID(window))
                done = true;
        }

        // [If using SDL_MAIN_USE_CALLBACKS: all code below would likely be your SDL_AppIterate() function]
        if (SDL_GetWindowFlags(window) & SDL_WINDOW_MINIMIZED)
        {
            SDL_Delay(10);
            continue;
        }

        // Start the Dear ImGui frame
        ImGui_ImplSDLGPU3_NewFrame();
        ImGui_ImplSDL3_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::ColorEdit4("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* draw_data = ImGui::GetDrawData();
        const bool is_minimized = (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f);

        SDL_GPUCommandBuffer* command_buffer = SDL_AcquireGPUCommandBuffer(gpu_device); // Acquire a GPU command buffer

        SDL_GPUTexture* swapchain_texture;
        SDL_AcquireGPUSwapchainTexture(command_buffer, window, &swapchain_texture, nullptr, nullptr); // Acquire a swapchain texture

        if (swapchain_texture != nullptr && !is_minimized)
        {
            // This is mandatory: call Imgui_ImplSDLGPU3_PrepareDrawData() to upload the vertex/index buffer!
            Imgui_ImplSDLGPU3_PrepareDrawData(draw_data, command_buffer);

            // Setup and start a render pass
            SDL_GPUColorTargetInfo target_info = {};
            target_info.texture = swapchain_texture;
            target_info.clear_color = SDL_FColor { clear_color.x, clear_color.y, clear_color.z, clear_color.w };
            target_info.load_op = SDL_GPU_LOADOP_CLEAR;
            target_info.store_op = SDL_GPU_STOREOP_STORE;
            target_info.mip_level = 0;
            target_info.layer_or_depth_plane = 0;
            target_info.cycle = false;
            SDL_GPURenderPass* render_pass = SDL_BeginGPURenderPass(command_buffer, &target_info, 1, nullptr);

            // Render ImGui
            ImGui_ImplSDLGPU3_RenderDrawData(draw_data, command_buffer, render_pass);

            SDL_EndGPURenderPass(render_pass);
        }

        // Submit the command buffer
        SDL_SubmitGPUCommandBuffer(command_buffer);
    }

    // Cleanup
    // [If using SDL_MAIN_USE_CALLBACKS: all code below would likely be your SDL_AppQuit() function]
    SDL_WaitForGPUIdle(gpu_device);
    ImGui_ImplSDL3_Shutdown();
    ImGui_ImplSDLGPU3_Shutdown();
    ImGui::DestroyContext();

    SDL_ReleaseWindowFromGPUDevice(gpu_device, window);
    SDL_DestroyGPUDevice(gpu_device);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}