System Defaults in GSettings

Posted by Ross Burton on July 4, 2011

Note: Florian in the comments points me at the documentation (albeit rather concise) for this in the API documentation under Vendor Overrides.

GSettings, like GConf before it, allows the administrator of a system to override the default settings or lock down keys to particular settings. This is well documented in the GNOME wiki.

However GConf didn't really have the concept of vendor patches. Traditionally if a Vendor wanted to change a default (say, the wallpaper) they'd have to patch the GConf schemas directly. Luckily for people who maintain distributions, GSettings provides a way of installing vendor overrides directly. It's not documented as far as I can tell so consider this a first draft at the manual...

First, find the setting you want to override, dconf-editor is useful for this. Say you're making a work-orientated custom distribution so you want the shell's popup calendar to show the week number by default. Some digging in dconf-editor leads us to the folder (the "schema") with a boolean key show-weekdate that defaults to false. By changing the default of this to true, all users will have work week shown unless they explicitly set it to false.

Now we've found the information we need we can write the override file. Create a new file with the extension .gschema.override, such as mydistro-tweaks.gschema.override. This file is a .ini-style keyfile, logically mapping schemas to groups and key/value pairs to (predicable) key/value pairs. The value needs to be in the GVariant serialisation format, but for things like booleans, numbers and strings these are fairly obvious. So we'd have a file that looks a little something like this:


Note that you can set multiple keys in multiple schemas in the same override file, so if we also wanted to show the date in the panel we'd have this:



Now the file is ready to be installed. Put it in a package, install to $prefix/share/glib-2.0/schemas and finally run glib-compile-schemas $prefix/share/glib-2.0/schemas in the post-install/post-remove hooks. Done!

(many thanks to Ryan Lortie for telling me how vendor patches work)

tags: tech