problem: Automatic size changes of group-based items, are not notified by gobject's "notify" signal

[Nikita Zlobin <nick87720z gmail com>]

g_object_get () showes, that property is changed also if group/table
size is changed automatically, to fit exactly to children.
I setup callback to "notify::width" signal, and it is not called in
such cases. But if i change property manually, by g_object_set(), it
works.