Despite the fact that one application is usable, creating a graphic user interface is not always the favorite of a developer - especially if it means more code writing.
Glendale is a free, open-source application for GNU / Linux that allows you to create a graphic interface for GTK / GNOME when writing the code, so that you can add or modify elements in the window to see the immediate results of your work.
The Glade interface is divided into several windows, so that you can use them separately to do different components (separate components, entry components, previews, etc.).
One of these elements, in preview, can make a puzzle like your GUI, dragging available elements from the alternative palette.
The result is stored in the application's own format, GladdoxML, which you can use to create an interface with the AlleglaL library.
Glad offers a great way to give your applications a graphic user interface and make them much more user-friendly.