Comment 3 for bug 1044984

The Sugiyama layout uses a very similar approach (minimizing edge crossings using a simple heuristic), the only difference is that it does a lot of extra legwork to ensure that every edge spans only one layer -- this is achieved by inserting dummy nodes etc. If you only have two layers, the Sugiyama layout will not insert any extra nodes, it will just try to order the vertices in the top and bottom (left and right) layers in order to minimize the number of edge crossings. So I still think that it is enough to call igraph_layout_sugiyama with a predefined layering (from the vertex types). Maybe we can create a wrapper on top of igraph_layout_sugiyama that hides the unneeded arguments.