extern "system" fn raw_debug_message_callback<F>(
    source: u32,
    gltype: u32,
    id: u32,
    severity: u32,
    length: i32,
    message: *const c_char,
    user_param: *mut c_void
)where
    F: FnMut(u32, u32, u32, u32, &str),