pub type PFNGLGETCOMPRESSEDTEXIMAGEPROC = Option<unsafe extern "C" fn(target: GLenum, lod: GLint, img: *mut c_void)>;
enum PFNGLGETCOMPRESSEDTEXIMAGEPROC { None, Some(unsafe extern "C" fn(_: u32, _: i32, _: *mut c_void)), }
No value.
Some value of type T.
T