如何通过EGL创建OpenGL 3.3或4.x上下文

我有兴趣制作一个不依赖X11的OpenGL应用程序。正如我所看到的，这应该可以通过EGL实现。甚至在互联网上也有例子。但是我如何控制上下文版本呢？下面的示例代码创建了一个版本为2.1的OpenGL上下文（在wayland上），但在我的计算机上，它显示支持的OpenGL最高版本是3.3（可以在X服务器中使用GLX和xlib使用glXCreateContextAttribsARB创建此类上下文）。所以我的问题是：我可以通过EGL以某种方式创建一个更高版本的OpenGL上下文吗？如果可以，如何创建？

示例代码：

#include <wayland-client.h>
#include <wayland-egl.h>
#include <EGL/egl.h>
#include <GL/gl.h>
#include <string.h>
#include <stdio.h>
#define WIDTH 256
#define HEIGHT 256
static struct wl_display *display;
static struct wl_compositor *compositor = NULL;
static struct wl_shell *shell = NULL;
static EGLDisplay egl_display;
static char running = 1;
struct window {
    EGLContext egl_context;
    struct wl_surface *surface;
    struct wl_shell_surface *shell_surface;
    struct wl_egl_window *egl_window;
    EGLSurface egl_surface;
};
// listeners
static void registry_add_object (void *data, struct wl_registry *registry, uint32_t name, const char *interface, uint32_t version) {
    if (!strcmp(interface,"wl_compositor")) {
        compositor = wl_registry_bind (registry, name, &wl_compositor_interface, 0);
    }
    else if (!strcmp(interface,"wl_shell")) {
        shell = wl_registry_bind (registry, name, &wl_shell_interface, 0);
    }
}
static void registry_remove_object (void *data, struct wl_registry *registry, uint32_t name) {
}
static struct wl_registry_listener registry_listener = {&registry_add_object, &registry_remove_object};
static void shell_surface_ping (void *data, struct wl_shell_surface *shell_surface, uint32_t serial) {
    wl_shell_surface_pong (shell_surface, serial);
}
static void shell_surface_configure (void *data, struct wl_shell_surface *shell_surface, uint32_t edges, int32_t width, int32_t height) {
    struct window *window = data;
    wl_egl_window_resize (window->egl_window, width, height, 0, 0);
}
static void shell_surface_popup_done (void *data, struct wl_shell_surface *shell_surface) {
}
static struct wl_shell_surface_listener shell_surface_listener = {&shell_surface_ping, &shell_surface_configure, &shell_surface_popup_done};
static void create_window (struct window *window, int32_t width, int32_t height) {
    eglBindAPI (EGL_OPENGL_API);
    EGLint attributes[] = {
        EGL_RED_SIZE, 8,
        EGL_GREEN_SIZE, 8,
        EGL_BLUE_SIZE, 8,
    EGL_NONE};
    EGLConfig config;
    EGLint num_config;
    eglChooseConfig (egl_display, attributes, &config, 1, &num_config);
    window->egl_context = eglCreateContext (egl_display, config, EGL_NO_CONTEXT, NULL);
    window->surface = wl_compositor_create_surface (compositor);
    window->shell_surface = wl_shell_get_shell_surface (shell, window->surface);
    wl_shell_surface_add_listener (window->shell_surface, &shell_surface_listener, window);
    wl_shell_surface_set_toplevel (window->shell_surface);
    window->egl_window = wl_egl_window_create (window->surface, width, height);
    window->egl_surface = eglCreateWindowSurface (egl_display, config, window->egl_window, NULL);
    eglMakeCurrent (egl_display, window->egl_surface, window->egl_surface, window->egl_context);
}
static void delete_window (struct window *window) {
    eglDestroySurface (egl_display, window->egl_surface);
    wl_egl_window_destroy (window->egl_window);
    wl_shell_surface_destroy (window->shell_surface);
    wl_surface_destroy (window->surface);
    eglDestroyContext (egl_display, window->egl_context);
}
static void draw_window (struct window *window) {
    glClearColor (0.0, 1.0, 0.0, 1.0);
    glClear (GL_COLOR_BUFFER_BIT);
    printf("%sn", glGetString(GL_VERSION));
    eglSwapBuffers (egl_display, window->egl_surface);
}
int main () {
    display = wl_display_connect (NULL);
    struct wl_registry *registry = wl_display_get_registry (display);
    wl_registry_add_listener (registry, &registry_listener, NULL);
    wl_display_dispatch (display);
    egl_display = eglGetDisplay (display);
    eglInitialize (egl_display, NULL, NULL);
    struct window window;
    create_window (&window, WIDTH, HEIGHT);
    while (running) {
        wl_display_dispatch_pending (display);
        draw_window (&window);
    }
    delete_window (&window);
    eglTerminate (egl_display);
    wl_display_disconnect (display);
    return 0;
}

来源：https://github.com/eyelash/tutorials