liblightdm-qt-3-0 software package provides simple display manager (Qt library), you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install liblightdm-qt-3-0
liblightdm-qt-3-0 is installed in your system.
Make ensure the liblightdm-qt-3-0 package were installed using the commands given below,
$ sudo dpkg-query -l | grep liblightdm-qt-3-0 *
You will get with liblightdm-qt-3-0 package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Library development |
| Package | liblightdm-qt-3-0 |
| Version | 1.10.3-3 |
| Description | simple display manager (Qt library) |
| Sub Section | Libdevel |