Created attachment 160987 [details] [review]
patch

I noticed that gdbusproxy.c:on_properties_changed handles the
GVariant's somewhat inefficiently; attached patch fixes that.

The only behavioural change is that the changed_properties and
invalidated_properties parameters send to the gobject signal are now
present even when they're really empty; if that was by design, it's
of course easy to add that back:

- changed_properties,
- _properties);
+ _variant_n_children (changed_properties) != 0 ? changed_properties : NULL,
+ _properties[0] != NULL ? invalidated_properties : NULL);


Also, if in this part of the code:

  g_variant_get (parameters,
                 "(&s@a{sv}^a&s)",
                 &interface_name_for_signal,
                 &changed_properties,
                 &invalidated_properties);

  if (g_strcmp0 (interface_name_for_signal,
      proxy->priv->interface_name) != 0) 
     goto out;

the condition turns out to be often true, so that unpacking the
changed_properties and invalidated_properties would be in vain, the
code could even be amended to only unpack the interface_name_for_signal
first, check, and only then unpack the others.