After a system update last night, I noticed that Firefox and several other applications were using a different font for their UI. The new font renders larger glyphs, making all UIs look cramped, fit less text, and it’s somehow not as comfortable to read as the previous default (this last might be due to familiarity, but I do find the new default font too wide).
I used my laptop (which hadn’t been updated) as a reference to compare what’s changed and why a different font is being used. Not new fontconfig rules were installed, so fontconfig should behave the same.
GTK’s default font is configured via dconf, and is stored under the key
org.gnome.desktop.interface.font-name (this is true even if my desktop isn’t
GNOME; GTK configuration keys often start with org.gnome…). Checking this
configuration value revealed that the default font had changed.
This value can be changed interactively using the dconf-editor GUI, or via the
command line. The command line incantation to restore the previous default is:
dconf write /org/gnome/desktop/interface/font-name '"Cantarell 11"'
The double quotes are required because dconf expects a value surrounded by
quotes, and the terminal will “swallow” the outer quote and treat their inner
content as a single string.
Source of the change
The default values for dconf are stored in some XML files in
/usr/share/glib-2.0/schemas. In this case, the value is in
org.gnome.desktop.interface.gschema.xml, which is provided by the
gsettings-desktop-schemas. The upstream changelog for this project lists the
change in default font under Major changes in 48.beta. I’m not
running beta; I’m running the final release, but it seems that this is one of
those projects where stable releases don’t mention all applicable major changes;
end users are expected to read all changelog details for release candidates and
betas too.