The xcb-util module provides a number of libraries which sit on top of
libxcb, the core X protocol library, and some of the extension
libraries. These experimental libraries provide convenience functions
and interfaces which make the raw X protocol more usable. Some of the
libraries also provide client-side code which is not strictly part of
the X protocol but which have traditionally been provided by Xlib.

WM module is a Framework for window manager implementation. It brings
both client and window-manager helpers for ICCCM and EWMH.

WWW: https://xcb.freedesktop.org/