pub type PFNGLGETVIDEOUI64VNVPROC = Option<unsafe extern "C" fn(video_slot: GLuint, pname: GLenum, params: *mut GLuint64EXT)>;
enum PFNGLGETVIDEOUI64VNVPROC { None, Some(unsafe extern "C" fn(_: u32, _: u32, _: *mut u64)), }
No value.
Some value of type T.
T