The built-in official Gnome programming IDE ("Builder") seems to support "C, C++, Python, Vala, Rust and Ctags" too. [2]
Edit- A complete list of fully- and partially-supported languages for Gtk+ 3 is here: https://www.gtk.org/language-bindings.php
Edit 2- I was wrong about Vala! See comments below. :)
1. https://wiki.gnome.org/Projects/Vala 2. https://wiki.gnome.org/Apps/Builder
I think the only Vala maintainer right now is from Elementary OS, where they use primarily Vala.
No, some Gnome developers blame Vala for all their problems and want to rewrite everything in Rust :
http://www.phoronix.com/scan.php?page=news_item&px=GNOME-Val...
Vala isn't in a good state today, it virtually has no maintainer. Gtk isn't in a good shape either. API keep changing, bugs are never fixed and maintainers seem to care very little about stability. Actually the whole GObject ecosystem is in a difficult situation.
IMHO, using Python is right now the only viable way to write Linux desktop apps without using C or C++ .
> The built-in official Gnome programming IDE ("Builder") seems to support "C, C++, Python, Vala, Rust and Ctags" too. [2]
Gnome Builder isn't financed by the Gnome Foundation AFAIK.