pub type PFNGLVDPAUMAPSURFACESNVPROC = Option<unsafe extern "C" fn(numSurfaces: GLsizei, surfaces: *const GLvdpauSurfaceNV)>;
enum PFNGLVDPAUMAPSURFACESNVPROC { None, Some(unsafe extern "C" fn(_: i32, _: *const isize)), }
No value.
Some value of type T.
T