org.jgrapht.alg.drawing.CircularLayoutAlgorithm2D Maven / Gradle / Ivy
/*
* (C) Copyright 2018-2023, by Dimitrios Michail and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht.alg.drawing;
import org.jgrapht.*;
import org.jgrapht.alg.drawing.model.*;
import org.jgrapht.alg.util.*;
import java.util.*;
import java.util.stream.*;
/**
* Circular layout.
*
*
* The algorithm places the graph vertices on a circle evenly spaced. The vertices are iterated
* based on the iteration order of the vertex set of the graph. The order can be adjusted by
* providing an external comparator.
*
* @author Dimitrios Michail
*
* @param the vertex type
* @param the edge type
*/
public class CircularLayoutAlgorithm2D
extends BaseLayoutAlgorithm2D
{
protected double radius;
protected Comparator comparator;
protected Comparator vertexComparator;
/**
* Create a new layout algorithm
*/
public CircularLayoutAlgorithm2D()
{
this(0.5d);
}
/**
* Create a new layout algorithm
*
* @param radius the circle radius
*/
public CircularLayoutAlgorithm2D(double radius)
{
this(radius, null);
}
/**
* Create a new layout algorithm. The algorithm will iterate over the vertices of the graph
* using the provided ordering.
*
* @param radius the circle radius
* @param vertexComparator the vertex comparator. Can be null.
*/
public CircularLayoutAlgorithm2D(double radius, Comparator vertexComparator)
{
this.comparator = new ToleranceDoubleComparator();
this.radius = radius;
if (comparator.compare(radius, 0d) <= 0) {
throw new IllegalArgumentException("Radius must be positive");
}
this.vertexComparator = vertexComparator;
}
@Override
public void layout(Graph graph, LayoutModel2D model)
{
super.init(graph, model);
Box2D drawableArea = model.getDrawableArea();
double width = drawableArea.getWidth();
if (comparator.compare(2d * radius, width) > 0) {
throw new IllegalArgumentException("Circle does not fit into drawable area width");
}
double height = drawableArea.getHeight();
if (comparator.compare(2d * radius, height) > 0) {
throw new IllegalArgumentException("Circle does not fit into drawable area height");
}
double minX = drawableArea.getMinX();
double minY = drawableArea.getMinY();
int n = graph.vertexSet().size();
double angleStep = 2 * Math.PI / n;
Stream vertexStream;
if (vertexComparator != null) {
vertexStream = graph.vertexSet().stream().sorted(vertexComparator);
} else {
vertexStream = graph.vertexSet().stream();
}
Iterator it = vertexStream.iterator();
int i = 0;
while (it.hasNext()) {
double x = radius * Math.cos(angleStep * i) + width / 2;
double y = radius * Math.sin(angleStep * i) + height / 2;
V v = it.next();
model.put(v, Point2D.of(minX + x, minY + y));
i++;
}
}
}