gtkmm-documentation binary package in Ubuntu Xenial amd64

 GLib is a low-level general-purpose library used mainly by GTK+/GNOME
 applications, but is useful for other programs as well.
 glibmm is the C++ wrapper for GLib.
 .
 Gtkmm is a C++ interface for the popular GUI library GTK+. It provides
 a convenient interface for C++ programmers to create graphical user
 interfaces with GTK+'s flexible OO framework. Highlights include type
 safe callbacks, widgets extensible using inheritance and over 180
 classes that can be freely combined to quickly create complex user
 interfaces.
 .
 This package contains tutorial, FAQ, as well as examples for the above
 components.

Source package