GObject size issue.

[Andrew Burr <andrewburr mac com>]

All,
What am I doing wrong here when I get this error? I am can find any
other info on the topic and am stumped.

(<unknown>:1930): GLib-GObject-WARNING **: specified class size for type
`XGCONTROL' is smaller than the parent type's `GtkVBox' class size


struct _XGenericControl
{
    GtkVBox     parent;
    GtkWidget   *label;
};

struct _XGenericControlClass
{
    GtkVBoxClass  parent_class;
};

GtkType
x_generic_control_get_type (void)
{
    static GtkType x_generic_control_type = 0;

    if (!x_generic_control_type) {
        static const GTypeInfo x_generic_control_info = {
            sizeof (XGenericControlClass),
            NULL,           /* base_init */
            NULL,           /* base_finalize */
            (GClassInitFunc) x_generic_control_class_init,
            NULL,           /* class_finalize */
            NULL,           /* class_data */
            sizeof (XGenericControl),
            0,              /* n_preallocs */
            (GInstanceInitFunc) x_generic_control_init
        };

        x_generic_control_type = g_type_register_static (GTK_TYPE_VBOX,
"XGCONTROL", &x_generic_control_info, 0);
    }

    return x_generic_control_type;
}