pub type PFNGLSAMPLERPARAMETERFVPROC = Option<unsafe extern "C" fn(sampler: GLuint, pname: GLenum, params: *const GLfloat)>;
enum PFNGLSAMPLERPARAMETERFVPROC { None, Some(unsafe extern "C" fn(_: u32, _: u32, _: *const f32)), }
No value.
Some value of type T.
T