the font description to use, or %NULL to undo the effect of previous calls to gtk_widget_override_font()
Deprecated: This function is not useful in the context of CSS-based rendering. If you wish to change the font a widget uses to render its text you should use a custom CSS style, through an application-specific #GtkStyleProvider and a CSS style class.
3.0
Sets the font to use for a widget. All other style values are left untouched. See gtk_widget_override_color().