Phoronix: X Generic Event (XGE) Protocol Specification

As part of his work on Multi-Pointer X, Peter Hutterer had developed the Generic Event Extension for X.Org, or commonly referred to as XGE. The X Generic Event Extension makes it possible for clients to reuse a single event opcode, which is needed with MPX since the X Server is currently limited to supporting only 64 opcodes between all X extensions. While MPX went mainline earlier this year, it's being disabled in X Server 1.6 since X Input 2 isn't ready...

http://www.phoronix.com/vr.php?view=Njg4OA