[GTK+, Cairo] Как установить шрифт GtkFontButton в cairo_set_font_face?

gtk_font_button_get_font_name ()

const gchar*        gtk_font_button_get_font_name       (GtkFontButton *font_button);
Retrieves the name of the currently selected font. This name includes style and size information as well. If you want to render something with the font, use this string with pango_font_description_from_string() . If you're interested in peeking certain values (family name, style, size, weight) just query these properties from the PangoFontDescription object.

font_button :
a GtkFontButton
Returns :
an internal copy of the font name which must not be freed.