It's pretty easy to set the default font for GtkTextView with gtk_widget_modify_font() , but how do you get which one is current? (I do not use any tags in widgets.)
gtk_widget_modify_font()
You can use gtk_widget_get_style() to get the current GtkStyle, and then use gtk_style_get_font() .
gtk_widget_get_style()
gtk_style_get_font()