The font was already settable via the gtk-font-name property of the settings object, but this this much more convenient.
70e898b inspector: Add a font button to the visual tab
gtk/inspector/visual.c | 11 +++++++++++
gtk/inspector/visual.ui | 43 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+)
Upstream: git.gnome.org