I had assumed so. I commented in a Rust context about this since gtk-rs does not add anything manually. The response was "if it isn't in GTK+, it shouldn't be in the bindings". I can see the point they are making, but this is so obviously a missing feature that should be in GTK+. The response, I suspect quite reasonably, is "raise a bug and send in a pull request". I am not sure I will as I am not sure I want to get involved in programming this in C – I have a Rust implementation.

My overiding question is why the gtkmm folk didn't follow the points made by the gtk-rs folk and get it into GTK+?

I'm happy with the way things are in GtkD though.