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