Comment 7 for bug 1283966

Ah, that's a bug in gedit actually. gedit/gedit-window.c declares the "state" property as GFlags:
……………………g_object_class_install_property (object_class,
………………………………………………………………………………………………………… PROP_STATE,
………………………………………………………………………………………………………… g_param_spec_flags ("state",
…………………………………………………………………………………………………………………………………………………… "State",
…………………………………………………………………………………………………………………………………………………… "The window's state",
…………………………………………………………………………………………………………………………………………………… GEDIT_TYPE_WINDOW_STATE,
…………………………………………………………………………………………………………………………………………………… GEDIT_WINDOW_STATE_NORMAL,
…………………………………………………………………………………………………………………………………………………… G_PARAM_READABLE |
…………………………………………………………………………………………………………………………………………………… G_PARAM_STATIC_STRINGS));

But gedit_window_get_property() calls g_value_set_enum() on the GValue; it should be g_value_set_flags().