Font setting for a specific gtk 3 application

[José Romildo Malaquias <jrmalaq gmail com>]

I want to set the font to be used by a particular Gtk+ 3
application. How can it be done?

I know I can set the font to be used by all Gtk+ 3 applications in the
file $XDG_CONFIG_HOME/gtk-3.0/settings.ini, but I do not know how the
font can be set for only a specific application.

Regards,

Romildo