How to use ANGLE with SDL3 on iOS

app.cpp

#define SDL_MAIN_USE_CALLBACKS 1
#include <SDL3/SDL_main.h>
#include <SDL3/SDL.h>

#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <GLES2/gl2.h>
#include <GLES3/gl3.h>

struct AppState
{
    int w;
    int h;
    SDL_Window* window;
    EGLSurface egl_surface;
    EGLDisplay egl_display;
};

SDL_AppResult SDL_AppInit(void** appstate, int argc, char* argv[])
{
    auto app = new AppState();
    *appstate = app;

    SDL_SetLogPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_VERBOSE);
    SDL_Init(SDL_INIT_VIDEO);
    app->window = SDL_CreateWindow("Experiment", 0, 0, SDL_WINDOW_METAL | SDL_WINDOW_HIGH_PIXEL_DENSITY);
    SDL_SyncWindow(app->window);
    SDL_GetWindowSizeInPixels(app->window, &app->w, &app->h);
    
    auto metal_view = SDL_Metal_CreateView(app->window);
    auto metal_layer = SDL_Metal_GetLayer(metal_view);
    
    EGLAttrib egl_display_attribs[] = {
        EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_METAL_ANGLE,
        EGL_POWER_PREFERENCE_ANGLE, EGL_HIGH_POWER_ANGLE,
        EGL_NONE
    };
    
    auto display = eglGetPlatformDisplay(EGL_PLATFORM_ANGLE_ANGLE, (void*) EGL_DEFAULT_DISPLAY, egl_display_attribs);
    app->egl_display = display;
    if (display == EGL_NO_DISPLAY)
    {
        printf("Failed to get EGL display");
        return SDL_APP_FAILURE;
    }
    
    if (eglInitialize(display, NULL, NULL) == false)
    {
        printf("Failed to initialize EGL");
        return SDL_APP_FAILURE;
    }
    
    EGLint egl_config_attribs[] = {
        EGL_RED_SIZE, 8,
        EGL_GREEN_SIZE, 8,
        EGL_BLUE_SIZE, 8,
        EGL_ALPHA_SIZE, 8,
        EGL_DEPTH_SIZE, 16,
        EGL_STENCIL_SIZE, 8,
        EGL_COLOR_BUFFER_TYPE, EGL_RGB_BUFFER,
        EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT,
        EGL_NONE
    };
    
    EGLConfig config;
    EGLint configs_count;
    if (!eglChooseConfig(display, egl_config_attribs, &config, 1, &configs_count))
    {
        printf("Failed to choose EGL config");
        return SDL_APP_FAILURE;
    }
    
    EGLint egl_context_attribs[] = {
        EGL_CONTEXT_CLIENT_VERSION, 3,
        EGL_NONE
    };
    auto context = eglCreateContext(display, config, EGL_NO_CONTEXT, egl_context_attribs);
    if (context == EGL_NO_CONTEXT) {
        printf("Failed to create EGL context");
        return SDL_APP_FAILURE;
    }
    
    auto surface = eglCreateWindowSurface(display, config, metal_layer, NULL);
    app->egl_surface = surface;
    if (surface == EGL_NO_SURFACE)
    {
        printf("Failed to create EGL surface");
        return SDL_APP_FAILURE;
    }
    
    if (!eglMakeCurrent(display, surface, surface, context))
    {
        printf("Failed to make EGL context current");
        return SDL_APP_FAILURE;
    }
    
    auto renderer = glGetString(GL_RENDERER);
    auto vendor = glGetString(GL_VENDOR);
    auto version = glGetString(GL_VERSION);
    printf("\nOpenGL ES Renderer: %s, Vendor: %s, Version: %s\n", renderer, vendor, version);
    
    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppIterate(void* appstate)
{
    auto app = (AppState*) appstate;
    
    auto now = ((double)SDL_GetTicks()) / 1000.0;
    auto red = float(0.5 + 0.5 * SDL_sin(now));
    auto green = float(0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 2 / 3));
    auto blue = float(0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 4 / 3));
    
    glClearColor(red, green, blue, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    
    eglSwapBuffers(app->egl_display, app->egl_surface);

    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppEvent(void* appstate, SDL_Event* event)
{
    if (event->type == SDL_EVENT_QUIT)
    {
        return SDL_APP_SUCCESS;
    }

    return SDL_APP_CONTINUE;
}

void SDL_AppQuit(void* appstate, SDL_AppResult result)
{
    SDL_Quit();
}

I managed to finally get something on screen via ANGLE on iOS with SDL3 thanks to your gist, so thanks a lot, it works! :D

Yo, I am glad I could help someone else also get this working. Enjoy!