Install libgtkextra-dev by entering the following commands in the terminal:
sudo apt update sudo apt install libgtkextra-dev
Description:
development files for libgtkextra-x11-3.0
libgtkextra-x11-3.0 provides a useful set of widgets for creating GUI's for GTK+
Homepage: http://gtkextra.sourceforge.net/cms/
Version: 3.3.4-1
Section: universe/libdevel