pub type PFNGLTEXPARAMETERIIVEXTPROC = Option<unsafe extern "C" fn(target: GLenum, pname: GLenum, params: *const GLint)>;
enum PFNGLTEXPARAMETERIIVEXTPROC { None, Some(unsafe extern "C" fn(_: u32, _: u32, _: *const i32)), }
No value.
Some value of type T.
T