gtkmm-documentation, describing the C++ binding of GTK, is one of the modules
listed at https://l10n.gnome.org/module/.
Is this necessary or desired? It has attracted very little interest from translators.
The latest update of a translation is almost 2 years old. All translations except
one is less than 50% translated. The exception is Chinese, 72%.
The intended audience of gtkmm-documentation consists of C++ programmers, using
or thinking of using gtkmm. To use gtkmm, you also have to read some of the
reference documentation, which is only available in English.