Use gtk_box_query_child_packing() and gtk_box_set_child_packing() to query and reset the padding, expand, fill, and pack fields. GtkBoxChild contains the following fields. (These fields should be considered read-only. They should never be directly set by an application.) GtkWidget * widget; the child widget, packed into the GtkBox. guint16 padding; the number of extra pixels to put between this child and its neighbors, set when packed, zero by default. guint expand; flag indicates whether extra space should be given to this child. Any extra space given to the parent GtkBox is divided up among all children with this attribute set to TRUE; set when packed, TRUE by default. guint fill; flag indicates whether any extra space given to this child due to its expand attribute being set is actually allocated to the child, rather than being used as padding around the widget; set when packed, TRUE by default. guint pack; one of GtkPackType indicating whether the child is packed with reference to the start (top/left) or end (bottom/right) of the GtkBox.