libdmx-dev software package provides X11 Distributed Multihead extension library (development headers), you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install libdmx-dev
libdmx-dev is installed in your system.
Make ensure the libdmx-dev package were installed using the commands given below,
$ sudo dpkg-query -l | grep libdmx-dev *
You will get with libdmx-dev package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Library development |
| Package | libdmx-dev |
| Version | 1:1.1.3-1 |
| Description | X11 Distributed Multihead extension library (development headers) |
| Sub Section | libdevel |