How to replace gdk_screen_get_monitor_at_window?

[zahlenmeer gmx de]

I am specifically interested in the number of the monitor, which is
returned by gdk_screen_get_monitor_at_window. However, its advertised
replacement gdk_display_get_monitor_at_window only returns the pointer
to the monitor.
My try would be:

gint display_helper_get_monitor_num_at_window (GdkDisplay *display,
                                               GdkWindow  *window)
{
  gint i;
  GdkMonitor *mon;

  for (i = 0; i < gdk_display_get_n_monitors (display); ++i)
  {
    mon = gdk_display_get_monitor_at_window (display, window);
    if (gdk_display_get_monitor (i) == mon)
      return i;
  }

  // no monitor found, can this even happen?
  return -1;
}

Maybe a little context:
I am using the number to identify monitors in a settings backend. The
idea behing this choice was that not all monitors have a model name, but
a number. So the number was the preferred way of identifying monitors
(although I am aware that even the numbers could change).
Is there a recommended way in GTK to identify monitors?