engine_smoke/main.cpp

// engine_smoke — gamedev stack smoke test.
// Validates SDL3 + sokol_gfx + Dear ImGui (imgui_impl_sdl3 + imgui_impl_opengl3)
// builds and runs on PC (desktop GL 3.3) and WASM (WebGL2 via -sFULL_ES3=1).
//
// Issue 0072a. Standalone — does NOT use fn_framework / add_imgui_app.

#include <cstdio>
#include <cstdint>
#include <cmath>

#include <SDL3/SDL.h>

// sokol_gfx — single TU includes the implementation.
#define SOKOL_IMPL
#if defined(__EMSCRIPTEN__)
    #define SOKOL_GLES3
#else
    #define SOKOL_GLCORE
#endif
#include "sokol_gfx.h"
#include "sokol_log.h"
// sokol_glue.h is NOT used: it pulls in sokol_app symbols. We use SDL3 for
// windowing, so we build sg_environment / sg_swapchain manually.

#include "imgui.h"
#include "backends/imgui_impl_sdl3.h"
#include "backends/imgui_impl_opengl3.h"

#if defined(__EMSCRIPTEN__)
    #include <emscripten/emscripten.h>
#endif

namespace {

struct App {
    SDL_Window* win = nullptr;
    SDL_GLContext gl = nullptr;
    sg_pipeline pip{};
    sg_bindings bind{};
    sg_pass_action pass_action{};
    bool running = true;
    uint64_t frame = 0;
};

App g_app;

// Fullscreen-quad vertex shader (no inputs, gl_VertexID trick).
const char* VS_SRC =
#if defined(__EMSCRIPTEN__)
    "#version 300 es\n"
#else
    "#version 330 core\n"
#endif
    "out vec2 v_uv;\n"
    "void main() {\n"
    "  vec2 p = vec2((gl_VertexID == 1) ? 3.0 : -1.0, (gl_VertexID == 2) ? 3.0 : -1.0);\n"
    "  v_uv = p * 0.5 + 0.5;\n"
    "  gl_Position = vec4(p, 0.0, 1.0);\n"
    "}\n";

const char* FS_SRC =
#if defined(__EMSCRIPTEN__)
    "#version 300 es\n"
    "precision mediump float;\n"
#else
    "#version 330 core\n"
#endif
    "in vec2 v_uv;\n"
    "out vec4 frag;\n"
    "uniform float u_time;\n"
    "void main() {\n"
    "  float r = 0.5 + 0.5 * sin(u_time + v_uv.x * 6.2831);\n"
    "  float g = 0.5 + 0.5 * sin(u_time * 1.3 + v_uv.y * 6.2831);\n"
    "  float b = 0.5 + 0.5 * sin(u_time * 0.7 + (v_uv.x + v_uv.y) * 6.2831);\n"
    "  frag = vec4(r, g, b, 1.0);\n"
    "}\n";

sg_environment make_environment() {
    sg_environment env{};
    env.defaults.color_format = SG_PIXELFORMAT_RGBA8;
    env.defaults.depth_format = SG_PIXELFORMAT_DEPTH_STENCIL;
    env.defaults.sample_count = 1;
    return env;
}

sg_swapchain make_swapchain(int w, int h) {
    sg_swapchain sw{};
    sw.width = w;
    sw.height = h;
    sw.sample_count = 1;
    sw.color_format = SG_PIXELFORMAT_RGBA8;
    sw.depth_format = SG_PIXELFORMAT_DEPTH_STENCIL;
    sw.gl.framebuffer = 0;  // default framebuffer
    return sw;
}

void setup_gfx() {
    sg_desc d{};
    d.environment = make_environment();
    d.logger.func = slog_func;
    sg_setup(&d);

    sg_shader_desc sd{};
    sd.vertex_func.source = VS_SRC;
    sd.fragment_func.source = FS_SRC;
    sd.uniform_blocks[0].stage = SG_SHADERSTAGE_FRAGMENT;
    sd.uniform_blocks[0].size = sizeof(float);
    sd.uniform_blocks[0].layout = SG_UNIFORMLAYOUT_NATIVE;
    sd.uniform_blocks[0].glsl_uniforms[0].type = SG_UNIFORMTYPE_FLOAT;
    sd.uniform_blocks[0].glsl_uniforms[0].glsl_name = "u_time";
    sg_shader shd = sg_make_shader(&sd);

    sg_pipeline_desc pd{};
    pd.shader = shd;
    pd.primitive_type = SG_PRIMITIVETYPE_TRIANGLES;
    g_app.pip = sg_make_pipeline(&pd);

    g_app.pass_action.colors[0].load_action = SG_LOADACTION_CLEAR;
    g_app.pass_action.colors[0].clear_value = {0.05f, 0.05f, 0.08f, 1.0f};
}

void frame() {
    SDL_Event ev;
    while (SDL_PollEvent(&ev)) {
        ImGui_ImplSDL3_ProcessEvent(&ev);
        if (ev.type == SDL_EVENT_QUIT) g_app.running = false;
        if (ev.type == SDL_EVENT_WINDOW_CLOSE_REQUESTED) g_app.running = false;
    }

    int w, h;
    SDL_GetWindowSizeInPixels(g_app.win, &w, &h);

    sg_pass p{};
    p.action = g_app.pass_action;
    p.swapchain = make_swapchain(w, h);
    sg_begin_pass(&p);
    sg_apply_pipeline(g_app.pip);

    float t = (float)g_app.frame * (1.0f / 60.0f);
    sg_range time_range{ &t, sizeof(t) };
    sg_apply_uniforms(0, &time_range);

    sg_draw(0, 3, 1);  // 3 vertices, fullscreen tri via gl_VertexID

    // ImGui on top
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplSDL3_NewFrame();
    ImGui::NewFrame();

    ImGui::SetNextWindowPos(ImVec2(10, 10));
    ImGui::Begin("engine_smoke", nullptr,
        ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize |
        ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoMove);
    ImGui::Text("SDL3 + sokol_gfx + ImGui");
    ImGui::Text("FPS: %.1f", ImGui::GetIO().Framerate);
    ImGui::Text("Frame: %llu  Size: %dx%d", (unsigned long long)g_app.frame, w, h);
    if (ImGui::Button("Quit")) g_app.running = false;
    ImGui::End();

    ImGui::Render();
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

    sg_end_pass();
    sg_commit();
    SDL_GL_SwapWindow(g_app.win);
    g_app.frame++;
}

#if defined(__EMSCRIPTEN__)
void emscripten_loop() {
    if (!g_app.running) {
        emscripten_cancel_main_loop();
        return;
    }
    frame();
}
#endif

}  // namespace

int main(int /*argc*/, char** /*argv*/) {
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        std::fprintf(stderr, "SDL_Init failed: %s\n", SDL_GetError());
        return 1;
    }

#if defined(__EMSCRIPTEN__)
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#else
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
#endif
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    g_app.win = SDL_CreateWindow("engine_smoke", 1280, 720,
        SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_HIGH_PIXEL_DENSITY);
    if (!g_app.win) {
        std::fprintf(stderr, "SDL_CreateWindow failed: %s\n", SDL_GetError());
        SDL_Quit();
        return 1;
    }
    g_app.gl = SDL_GL_CreateContext(g_app.win);
    if (!g_app.gl) {
        std::fprintf(stderr, "SDL_GL_CreateContext failed: %s\n", SDL_GetError());
        SDL_DestroyWindow(g_app.win);
        SDL_Quit();
        return 1;
    }
    SDL_GL_MakeCurrent(g_app.win, g_app.gl);
    SDL_GL_SetSwapInterval(1);

    setup_gfx();

    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGui::StyleColorsDark();
    ImGui_ImplSDL3_InitForOpenGL(g_app.win, g_app.gl);
#if defined(__EMSCRIPTEN__)
    ImGui_ImplOpenGL3_Init("#version 300 es");
#else
    ImGui_ImplOpenGL3_Init("#version 330 core");
#endif

#if defined(__EMSCRIPTEN__)
    emscripten_set_main_loop(emscripten_loop, 0, 1);
#else
    while (g_app.running) frame();
#endif

    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplSDL3_Shutdown();
    ImGui::DestroyContext();
    sg_shutdown();
    SDL_GL_DestroyContext(g_app.gl);
    SDL_DestroyWindow(g_app.win);
    SDL_Quit();
    return 0;
}