libgtkextra-dev software package provides development files for libgtkextra-x11-3.0, 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 libgtkextra-dev
libgtkextra-dev is installed in your system.
Make ensure the libgtkextra-dev package were installed using the commands given below,
$ sudo dpkg-query -l | grep libgtkextra-dev *
You will get with libgtkextra-dev package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Library development |
| Package | libgtkextra-dev |
| Version | 3.1.1-2 |
| Description | development files for libgtkextra-x11-3.0 |
| Sub Section | Libdevel |