Native font peer is always set on creation of java.awt.Frame and other top level windows.
It seems to be only used by child heavyweight widgets (they copy font from parent on creation).
Toplevel components do not use fonts themselves (title bars are handled by Windows.

However, for pure Swing app such as Notepad or Netbeans there are no heavyweight components
except top levels. Therefore, (at least on Windows) this extra work can be avoided.