<li>
Combine the features of sfdp and fdp (e.g., clusters and fixed nodes).
<li>
+Improve the mincross algorithm to better handle flat edges and edge weights.
+<li>
Simplified mincross algorithm based on sifting, supporting clusters.
<li>
Implement swim lanes (nodes sharing x coordinate), possibly based on sifting.
<li>
Allow mixed edge types within the same graph.
<li>
+Allow varied rankdir values within clusters.
+<li>
Allow varied layouts within clusters.
<li>
Improve Spline router, e.g., fewer inflection points).