static bool showTitledForm_blocking(S title, O... _parts) {
  assertNotOnAWTThread();
  final new Var<Bool> var;
  onFrameClose(showFormTitled(title, arrayPlus(_parts,
    r { var.set(true) })),
    r { if (!var.has()) var.set(false) });
  waitUntilVarSet(var);
  ret var.get();
}