libgtkextra-3.0 software package provides useful set of widgets for creating GUIs for GTK+, 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-3.0
libgtkextra-3.0 is installed in your system.
Make ensure the libgtkextra-3.0 package were installed using the commands given below,
$ sudo dpkg-query -l | grep libgtkextra-3.0 *
You will get with libgtkextra-3.0 package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Development |
| Package | libgtkextra-3.0 |
| Version | 3.1.1-2 |
| Description | useful set of widgets for creating GUIs for GTK+ |
| Sub Section | Devel |