Changing shape and position of edges in Jung

Question

I need to arrange the nodes in a particular way. I have tried with static layout. I can change the position of the nodes but fails to place the edges in specific locations. The static layout has a setLocation method that I used to change the position of the node but for edges, I have no idea about how to place them in specific locations so that newly positioned nodes are connected with edges.

Another question: How can I change the shape of an edge in Jung by overriding the transform method.

Answer 1

JUNG does not provide good support, at this time, for edge placement. EdgeShape, and in particular EdgeShape.Orthogonal, will show you what built-in support exists.

Answer 2

I know that this thread is a bit old but I think it needs to be revived - hoping this question hasn't been answered already. The reason is that Mr. O'Madadhains' answer couldn't help me. (maybe because of my deficit and will of understanding documentations) After some work on JUNG techniques I'd be happy to get some qualified comment now.

There are two (seeming to be) simple ways to transform edges in a static layout.

The first way is to override the "transform" method of the Transformer directly affecting the edge shape:

Transformer<Graph<Context<String, String>, String>, Shape> edgeTransformer = new Transformer<Graph<Context<String,String>,String>,Shape>(){
        @Override
        public Shape transform(Graph<Context<String, String>, String> graphStringContext)
        {
            return (new Line2D.Double());
        }
    };

(if there is used a "Graph" graph)

Concerning the sense edges do have - which is to connect - a simple example would be returning an individual Line2D (which will consist of the center points the affected vertices do have) to the renderer. The method call obviously is:

vv.getRenderContext().setEdgeShapeTransformer(edgeTransform);

BUT: this just doesn't work. (maybe because I did it wrong; the lack of tutorials excuses that) Whatever one will try to make the "transform" method return, the renderer will just get null-values.

The 2nd possibility is to split the vertex transformation into two transformers. The first transformer will set only the basic vertex position by using:

Transformer<String, Point2D> vertexPositionTransformer = new Transformer<String,Point2D>() {
            @Override
            public Point2D transform(String st) {
                return new Point2D.Double();
            };

The 2nd one is optional. It may be used to change the vertex size or whatever one want the shape to look like. There will be needed the positions of the location transformed vertices, because this transformer would override the position set.

Transformer<String, Shape> vertexShapeTransformer = new Transformer<String, Shape>() {
            @Override
            public Shape transform(String st) {
                return new Ellipse2D.Double();
            };

Now the layout can be instanciated. It will not be constructed the default way with the Graph as single parameter but with an additional one: the vertexPositionTransformer. That will look like:

StaticLayout<String, String> layout = new StaticLayout<String, String>(graph, vertexPositionTransformer);

Transforming the edges on layout construction will automatically set the edge endpoints to the center of each included vertex.

In the code examples I waived the content of the "transform" methods which of course would differ from purpose to purpose. Using the "Transformer" classes/objects has to be done after adding the vertices and edges to the graph that shall be affected by them. That's it. Please correct bad style and such issues. I am glad getting feedback.

Greetings

Lukas Koschine