/** @see org.eclipse.graph.HorizontalPlacement#applyGPrime() */
 void applyGPrime() {
   super.applyGPrime();
   NodeList subgraphs = ((CompoundDirectedGraph) graph).subgraphs;
   for (int i = 0; i < subgraphs.size(); i++) {
     Subgraph s = (Subgraph) subgraphs.get(i);
     s.x = s.left.x;
     s.width = s.right.x + s.right.width - s.x;
   }
 }
 public void visit(DirectedGraph g) {
   super.visit(g);
 }