Create an OpenGL context for an OpenGL window, and make it current.
SDL_GLContext SDL_GL_CreateContext(SDL_Window * window);
the window to associate with the context
Returns the OpenGL context associated with
window or NULL on error; call SDL_GetError() for more details.
Windows users new to OpenGL should note that, for historical reasons, GL functions added after OpenGL version 1.1 are not available by default. Those functions must be loaded at run-time, either with an OpenGL extension-handling library or with SDL_GL_GetProcAddress() and its related functions.
SDL_GLContext is an alias for
void *. It's opaque to the application.
This function is available since SDL 2.0.0.