OpenGL by itself is useless, it just does 3D graphics, and its GLUT library is too bare-bones to be of much use. SDL is a good, portable chassis for OpenGL application that don't need native GUI integration. An SDL OpenGL app will compile and run almost anywhere, with minimal fuss. Compare that to using OpenGL contexts inside platform-specific toolkits.
It's very, very barebones (just enough to GL up to do a thing), but it's quite good in that role.
#include <GLFW/glfw3.h>
int main(void)
{
GLFWwindow* window;
if (!glfwInit())
return -1;
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window) {
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
while (!glfwWindowShouldClose(window)) {
/* Render here */
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
#include <GL3/gl3.h>
#include <SDL.h>
/* Our program's entry point */
int main(int argc, char *argv[])
{
SDL_Window *mainwindow;
SDL_GLContext maincontext;
SDL_Event event;
int running = 1;
if (SDL_Init(SDL_INIT_VIDEO) < 0)
exit(1);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
mainwindow = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
if (!mainwindow)
exit(1);
maincontext = SDL_GL_CreateContext(mainwindow);
SDL_GL_SetSwapInterval(1);
while (running) {
while (SDL_PollEvent(&event) {
if ( event == SDL_WINDOWEVENT_CLOSE ) {
running = 0;
break;
}
/* render */
}
SDL_GL_SwapWindow(mainwindow);
}
SDL_GL_DeleteContext(maincontext);
SDL_DestroyWindow(mainwindow);
SDL_Quit();
return 0;
}
There's nothing wrong with using SDL for making a game (well, maybe a couple of things, but that's not relevant here), but it simply isn't the smallest GL scaffolding library out there.
But I got bit by half-assed "GL" ways of doing things before. SDL has everything, in layers, so you can grow into it. Unlike "portable GL" libraries which are discrete, isolate dead-ends.
GLFW does not attempt to handle OpenGL for you, it handles windowing and input for you. I personally really don't want SDL anywhere near my projects because it imposes its own structure upon me. (I don't use Allegro, even for 2D code, for similar reasons.) I am simply not all that fussed by writing up a VBO handler and some pretty simple OpenAL code myself--it isn't difficult enough for me to warrant the huge blob of extraneous SDL stuff.
window = glfwCreateWindow(640, 480, "Hello World", glfwGetPrimaryMonitor(), NULL);
glfwOpenWindowHint(GLFW_OPENGL_VERSION_MAJOR, 3);
glfwOpenWindowHint(GLFW_OPENGL_VERSION_MINOR, 2);
glfwOpenWindowHint(GLFW_DEPTH_BIT, 24);
When wrapping OpenGL code myself, at least the dubious design decisions are my own and I understand them intuitively.