]> gedit is a quite old piece of software (created in 1998, at the beginnings of the GNOME project), and as every software, the code evolves during its lifetime. So there are sometimes API breaks for gedit plugins, there are no API stability guarantees. When it is possible, instead of directly removing an API, that API is first marked as deprecated, and then removed for the next API break. See the index of deprecated symbols. All previously deprecated APIs have been removed. The GeditDocument:use-gvfs-metadata property has been removed. But there was anyway a warning for not using that property in a gedit plugin. For gedit_document_get_metadata() and gedit_document_set_metadata(), the key names should now have the prefix "gedit-" with possibly an additional namespace for the plugin name, for example "gedit-spell-foobar". So the key names are now the same regardless of the operating system, and the key names should no longer start with "metadata::".