The only place that we see g_signal_emit for PROPERTIES_CHANGED_SIGNAL is in on_properties_changed which directly corresponds to org.freedesktop.DBus.Properties.PropertiesChanged.

The properties also change in two other situations:

  1) they are all dropped when we have a negative NameOwnerChanged

    - in this case, we should emit the signal to invalidate any properties that
      used to exist

  2) they are all filled in when we have a positive NameOwnerChanged

    - in this case, we should emit the signal with the new properties (if any)


It could be argued that it is the responsibility of the user to watch the "g-name-owner" signal in order to know when the properties have changed, but my first assumption would be that watching the "properties-changed" signal would be sufficient for that.