Geany is a small and lightweight integrated development environment. It was developed to provide a small and fast IDE, which has only a few dependencies from other packages. Another goal was to be as independent as possible from a special Desktop Environment like KDE or GNOME. So it is using only the GTK+ toolkit and therefore you need only the GTK+ runtime libraries to run Geany.
grade: devel # must be 'stable' to release into candidate/stable channels
confinement: devmode # use 'strict' once you have the right plugs