imgui/examples/example_sdl3_surface/main.cpp

#include "imgui.h"
#include "imgui_impl_sdl3.h"
#include "imgui_impl_sdlsurface3.h"
#include <SDL3/SDL.h>
#include <stdio.h>
#ifdef __EMSCRIPTEN__
#include "../libs/emscripten/emscripten_mainloop_stub.h"
#endif

int main(int, char**)
{
    if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_GAMEPAD))
    {
        printf("Error: SDL_Init(): %s\n", SDL_GetError());
        return 1;
    }

    float main_scale = SDL_GetDisplayContentScale(SDL_GetPrimaryDisplay());
    SDL_WindowFlags window_flags = SDL_WINDOW_RESIZABLE | SDL_WINDOW_HIDDEN | SDL_WINDOW_HIGH_PIXEL_DENSITY;
    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL3+Surface Example", (int)(1280 * main_scale), (int)(800 * main_scale), window_flags);
    if (window == nullptr)
    {
        printf("Error: SDL_CreateWindow(): %s\n", SDL_GetError());
        return 1;
    }

    SDL_SetWindowPosition(window, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED);
    SDL_ShowWindow(window);

    SDL_Surface* window_surface = SDL_GetWindowSurface(window);
    if (window_surface == nullptr)
    {
        printf("Error: SDL_GetWindowSurface(): %s\n", SDL_GetError());
        SDL_DestroyWindow(window);
        SDL_Quit();
        return 1;
    }

    int framebuffer_w = window_surface->w;
    int framebuffer_h = window_surface->h;
    SDL_Surface* framebuffer = SDL_CreateSurface(framebuffer_w, framebuffer_h, SDL_PIXELFORMAT_RGBA32);
    if (framebuffer == nullptr)
    {
        printf("Error: SDL_CreateSurface(): %s\n", SDL_GetError());
        SDL_DestroyWindow(window);
        SDL_Quit();
        return 1;
    }

    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
#ifdef __EMSCRIPTEN__
    io.IniFilename = nullptr;
#endif

    ImGui::StyleColorsDark();

    ImGuiStyle& style = ImGui::GetStyle();
    style.ScaleAllSizes(main_scale);
    style.FontScaleDpi = main_scale;

    ImGui_ImplSDL3_InitForOther(window);
    ImGui_ImplSDLSurface3_Init(framebuffer);

    bool show_demo_window = true;
    bool show_another_window = false;
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
    bool done = false;

#ifdef __EMSCRIPTEN__
    EMSCRIPTEN_MAINLOOP_BEGIN
#else
    while (!done)
#endif
    {
        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 ((event.type == SDL_EVENT_WINDOW_RESIZED || event.type == SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED) && event.window.windowID == SDL_GetWindowID(window))
            {
                window_surface = SDL_GetWindowSurface(window);
                if (window_surface != nullptr)
                {
                    int new_w = window_surface->w;
                    int new_h = window_surface->h;
                    if (new_w != framebuffer_w || new_h != framebuffer_h)
                    {
                        SDL_DestroySurface(framebuffer);
                        framebuffer = SDL_CreateSurface(new_w, new_h, SDL_PIXELFORMAT_RGBA32);
                        if (framebuffer == nullptr)
                        {
                            printf("Error: SDL_CreateSurface(): %s\n", SDL_GetError());
                            done = true;
                            break;
                        }
                        framebuffer_w = new_w;
                        framebuffer_h = new_h;
                        ImGui_ImplSDLSurface3_Shutdown();
                        ImGui_ImplSDLSurface3_Init(framebuffer);
                    }
                }
            }
        }

        if (done)
            break;

        if (SDL_GetWindowFlags(window) & SDL_WINDOW_MINIMIZED)
        {
            SDL_Delay(10);
            continue;
        }

        ImGui_ImplSDLSurface3_NewFrame();
        ImGui_ImplSDL3_NewFrame();
        ImGui::NewFrame();

        if (show_demo_window)
            ImGui::ShowDemoWindow(&show_demo_window);

        {
            static float f = 0.0f;
            static int counter = 0;

            ImGui::Begin("Hello, world!");
            ImGui::Text("This is some useful text.");
            ImGui::Checkbox("Demo Window", &show_demo_window);
            ImGui::Checkbox("Another Window", &show_another_window);
            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
            ImGui::ColorEdit3("clear color", (float*)&clear_color);
            if (ImGui::Button("Button"))
                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();
        }

        if (show_another_window)
        {
            ImGui::Begin("Another Window", &show_another_window);
            ImGui::Text("Hello from another window!");
            if (ImGui::Button("Close Me"))
                show_another_window = false;
            ImGui::End();
        }

        ImGui::Render();

        SDL_FillSurfaceRect(framebuffer, nullptr, SDL_MapSurfaceRGBA(framebuffer,
            (Uint8)(clear_color.x * 255.0f),
            (Uint8)(clear_color.y * 255.0f),
            (Uint8)(clear_color.z * 255.0f),
            (Uint8)(clear_color.w * 255.0f)));

        ImGui_ImplSDLSurface3_RenderDrawData(ImGui::GetDrawData());

        window_surface = SDL_GetWindowSurface(window);
        if (window_surface != nullptr)
        {
            SDL_BlitSurface(framebuffer, nullptr, window_surface, nullptr);
            SDL_UpdateWindowSurface(window);
        }
    }
#ifdef __EMSCRIPTEN__
    EMSCRIPTEN_MAINLOOP_END;
#endif

    ImGui_ImplSDLSurface3_Shutdown();
    ImGui_ImplSDL3_Shutdown();
    ImGui::DestroyContext();

    SDL_DestroySurface(framebuffer);
    SDL_DestroyWindowSurface(window);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}