List of function signatures for x11-rs's xlib module:

    https://github.com/Daggerbot/x11-rs/blob/master/src/xlib.rs

Xlib programming manual:

    https://tronche.com/gui/x/xlib/

XScreensaver's "Writing new XScreenSaver modules" and FAQ:

    https://github.com/Zygo/xscreensaver/blob/master2/README.hacking
    https://www.jwz.org/xscreensaver/faq.html