static JTextField dm_feedTopInputToTextField(final JTextField tf) {
  ret dm_feedTopInputToTextField(tf, null);
}

static JTextField dm_feedTopInputToTextField(final JTextField tf, final F1<S, Bool> condition) {
  final DynModule m = dm_current_mandatory();
  dm_onTopInputChanged(voidfunc(fS s) {
    switch to m.q();
    if (!isFalse(callF(condition, s)))
      setText(tf, s);
  });
  ret tf;
}

Began life as a copy of #1019861