Sets the horizontal locations of node and edge dummy nodes on each layer. Uses median down and up weighings as well as heuristics to straighten edges as far as possible.
The specific layout interface for hierarchical layouts. It adds a <code>run</code> method with a parameter for the hierarchical layout model that is shared between the layout stages.
Performs a vertex ordering within ranks as described by Gansner et al 1993
An implementation of the first stage of the Sugiyama layout. Straightforward longest path calculation of layer assignment