How to enforce a custom layout in JUNG graph?

Question

I have following three sets of integers like the following:

set0 = {1} //this will always be a singleton set.
set1 = {2, 3, 4, 5}
set2 = {6, 7}

I have a graph that has edges which are either from set1 to set2 OR set2 to set3, thus forming a clear tree-like hierarchy of vertices.

 Set0 -- Set1  -- Set2

To display this tree-like graph I created a DelegateForest and TreeLayout

package Test;

import java.util.HashSet;
import java.util.Set;

import javax.swing.JFrame;
import javax.swing.JPanel;

import edu.uci.ics.jung.algorithms.layout.Layout;
import edu.uci.ics.jung.algorithms.layout.TreeLayout;
import edu.uci.ics.jung.graph.DelegateForest;
import edu.uci.ics.jung.graph.Forest;
import edu.uci.ics.jung.graph.Graph;
import edu.uci.ics.jung.visualization.VisualizationViewer;
import edu.uci.ics.jung.visualization.decorators.ToStringLabeller;

class Main{
    public static void main(String[] args){

    Set<Integer> set0 = new HashSet<Integer>();
    Set<Integer> set1 = new HashSet<Integer>();
    Set<Integer> set2 = new HashSet<Integer>();

    set0.add(1);

    set1.add(2);
    set1.add(3);
    set1.add(4);
    set1.add(5);

    set2.add(6);
    set2.add(7);

    JFrame frame = new JFrame();
    frame.add(createGraphPanel(set0, set1, set2));
    frame.pack();
    frame.setVisible(true);


    }

    private static JPanel createGraphPanel( Set<Integer> setZero, Set<Integer> firstSet, Set<Integer> secondSet) {
            // create a graph
            Graph<Integer, String> graph = new DelegateForest<Integer, String>();

                Integer vertex1 = setZero.iterator().next();
            for (Integer i : firstSet) {
                graph.addEdge(vertex1+"-"+i, vertex1, i);
            }

            Layout<Integer, String> layout = new TreeLayout<Integer, String>((Forest<Integer, String>) graph);
            VisualizationViewer<Integer, String> vv = new  VisualizationViewer<Integer,String>(layout);

            vv.getRenderContext().setVertexLabelTransformer(
                    new ToStringLabeller<Integer>());

            return vv;
        }
    }

However, the graph that I got (currently, just containing set1 and set2) looks like this

I would like to do a couple of things to this graph:

1. Instead of the nodes flowing from top to bottom, I would like them to flow form left to right. (Something like rotating it by 90 degrees)
2. Currently, the layout algorithm makes sure that there is no overlap, which spreads the nodes for set2 in a linear fashion. If the set2 is huge it would go beyond the bounds of the panel. I don't mind overlap and would like these nodes to appear close together as a cluster with partial overlaps allowed.

How can I achieve the two requirements?

Answer 1

I've extended the TreeLayout class and swapped all the x / y variables. This should display the tree horizontally. However, you'll have to add your own code to prevent the vertices from being placed in a line (perhaps use a bounding box and start at the top once you go past it).

public class HorizontalOverlappingTreeLayout<V, E> extends TreeLayout<V, E> {

    public static void main(String[] args) {
        Set<Integer> set0 = new HashSet<Integer>();
        Set<Integer> set1 = new HashSet<Integer>();
        Set<Integer> set2 = new HashSet<Integer>();
        set0.add(1);
        set1.add(2);
        set1.add(3);
        set1.add(4);
        set1.add(5);
        set2.add(6);
        set2.add(7);

        JPanel panel = new JPanel();
        Graph<Integer, String> graph = new DelegateForest<Integer, String>();
        Integer vertex1 = set0.iterator().next();
        for (Integer i : set1) {
            graph.addEdge(vertex1 + "-" + i, vertex1, i);
        }

        Layout<Integer, String> layout = new HorizontalOverlappingTreeLayout<Integer, String>(
                (Forest<Integer, String>) graph);
        VisualizationViewer<Integer, String> vv = new VisualizationViewer<Integer, String>(layout);
        vv.getRenderContext().setVertexLabelTransformer(new ToStringLabeller<Integer>());
        panel.add(vv);

        JFrame frame = new JFrame();
        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public HorizontalOverlappingTreeLayout(Forest<V, E> g) {
        super(g);
    }

    @Override
    protected void buildTree() {
        this.m_currentPoint = new Point(0, 20);
        Collection<V> roots = TreeUtils.getRoots(graph);
        if (roots.size() > 0 && graph != null) {
            calculateDimensionY(roots);
            for (V v : roots) {
                calculateDimensionY(v);
                m_currentPoint.y += this.basePositions.get(v) / 2 + this.distY;
                buildTree(v, this.m_currentPoint.y);
            }
        }
        // TODO: removed code here
    }

    @Override
    protected void buildTree(V v, int y) {
        if (!alreadyDone.contains(v)) {
            alreadyDone.add(v);

            // go one level further down
            this.m_currentPoint.x += this.distX;
            this.m_currentPoint.y = y;

            this.setCurrentPositionFor(v);

            int sizeYofCurrent = basePositions.get(v);

            int lastY = y - sizeYofCurrent / 2;

            int sizeYofChild;
            int startYofChild;

            for (V element : graph.getSuccessors(v)) {
                sizeYofChild = this.basePositions.get(element);
                startYofChild = lastY + sizeYofChild / 2;
                buildTree(element, startYofChild);
                lastY = lastY + sizeYofChild + distY;
            }
            this.m_currentPoint.x -= this.distX;
        }
    }

    private int calculateDimensionY(V v) {
        int size = 0;
        int childrenNum = graph.getSuccessors(v).size();

        if (childrenNum != 0) {
            for (V element : graph.getSuccessors(v)) {
                size += calculateDimensionY(element) + distY;
            }
        }
        size = Math.max(0, size - distY);
        basePositions.put(v, size);

        return size;
    }

    private int calculateDimensionY(Collection<V> roots) {
        int size = 0;
        for (V v : roots) {
            int childrenNum = graph.getSuccessors(v).size();

            if (childrenNum != 0) {
                for (V element : graph.getSuccessors(v)) {
                    size += calculateDimensionY(element) + distY;
                }
            }
            size = Math.max(0, size - distY);
            basePositions.put(v, size);
        }

        return size;
    }

}

Answer 2

To answer problem (1): there is a demo (L2RTreeLayoutDemo) that does this.

To answer problem (2): change the x and/or y spacing in the layout; this is settable in the constructor.