Package x11trace

A program for X11 protocol tracing

http://xtrace.alioth.debian.org/

What strace is for system calls, x11trace is for X11 connections:
you hook it between one or more X11 clients and an X server and
it prints the requests going from client to server and the replies,
events and errors going the other way.

General Commands
Command Description
x11trace trace communication between X11 client and server