How glib-rs works, part 3: Boxed types
https://people.gnome.org/~federico/blog/how-glib-rs-works-part-3.html [people.gnome.org]
2017-09-14 00:12
But for external resources, we must tell Rust how to manage them. Again: in the case where the Rust side owns the reference to the external boxed data, we have a ForeignOwned and Drop it by free()ing it; in the case where the Rust side is just borrowing the data temporarily, we have a ForeignBorrowed and don’t touch it when we are done.
source: L