Internal Program Version: libdmx  1.1.5

libdmx is an interface to the DMX extension for X, which allows a
single server to be set up as a proxy spanning multiple servers --
not unlike Xinerama across discrete physical machines. It can be
reconfigured on the fly to change the layout, and it is presented as
a single logical display to clients.

libdmx allows clients to configure the layout of DMX servers by
adding and removing screens, input devices, et al.

https://xorg.freedesktop.org