/*
* @(#)QuadTree.java
*
* Copyright (c) 1996-2010 The authors and contributors of JHotDraw.
* You may not use, copy or modify this file, except in compliance with the
* accompanying license terms.
*/
package org.jhotdraw.geom;
import edu.umd.cs.findbugs.annotations.Nullable;
import java.awt.geom.*;
import java.io.Serializable;
import java.util.*;
/**
* A QuadTree allows to quickly find an object on a two-dimensional space.
* <p>
* QuadTree recursively subdivides a space into four rectangles.
* Each node of a QuadTree subdivides the space covered by the rectangle of its
* parent node into four smaller rectangles covering the upper left, upper right,
* lower left and lower right quadrant of the parent rectangle.
*
* @author Werner Randelshofer
* @version $Id$
*/
public class QuadTree<T> implements Serializable {
private static final long serialVersionUID = 1L;
private HashMap<T,Rectangle2D.Double> outside = new HashMap<T,Rectangle2D.Double>();
private QuadNode root;
private int maxCapacity = 32;
private int minSize = 32;
private int maxOutside = 32;
/** Creates a new instance. */
public QuadTree() {
root = new QuadNode(new Rectangle2D.Double(0, 0, 800, 600));
}
public QuadTree(Rectangle2D.Double bounds) {
root = new QuadNode(bounds);
}
public void add(T o, Rectangle2D.Double bounds) {
if (root.bounds.contains(bounds)) {
root.add(o, (Rectangle2D.Double) bounds.clone());
} else {
outside.put(o, (Rectangle2D.Double) bounds.clone());
if (outside.size() > maxOutside) {
reorganize();
}
}
}
public void reorganize() {
root.join();
outside.putAll(root.objects);
root.objects.clear();
Iterator<Map.Entry<T,Rectangle2D.Double>> i = outside.entrySet().iterator();
Map.Entry<T,Rectangle2D.Double> entry = i.next();
Rectangle2D.Double treeBounds = (Rectangle2D.Double) (entry.getValue()).clone();
while (i.hasNext()) {
entry = i.next();
Rectangle2D.Double bounds = entry.getValue();
treeBounds.add(bounds);
}
root.bounds = treeBounds;
i = outside.entrySet().iterator();
while (i.hasNext()) {
entry = i.next();
root.add(entry.getKey(), entry.getValue());
}
outside.clear();
}
public void remove(T o) {
outside.remove(o);
root.remove(o);
}
public Collection<T> findContains(Point2D.Double p) {
HashSet<T> result = new HashSet<T>();
root.findContains(p, result);
for (Map.Entry<T,Rectangle2D.Double> entry : outside.entrySet()) {
if (entry.getValue().contains(p)) {
result.add(entry.getKey());
}
}
return result;
}
public Collection<T> findIntersects(Rectangle2D r) {
return findIntersects(new Rectangle2D.Double(r.getX(), r.getY(), r.getWidth(), r.getHeight()));
}
public Collection<T> findIntersects(Rectangle2D.Double r) {
HashSet<T> result = new HashSet<T>();
root.findIntersects(r, result);
for (Map.Entry<T,Rectangle2D.Double> entry : outside.entrySet()) {
if (entry.getValue().intersects(r)) {
result.add(entry.getKey());
}
}
return result;
}
public Collection<T> findInside(Rectangle2D.Double r) {
HashSet<T> result = new HashSet<T>();
root.findInside(r, result);
for (Map.Entry<T,Rectangle2D.Double> entry : outside.entrySet()) {
if (r.contains(entry.getValue())) {
result.add(entry.getKey());
}
}
return result;
}
private class QuadNode implements Serializable {
private static final long serialVersionUID = 1L;
private Rectangle2D.Double bounds;
/**
* We store an object into this map, if 1) the bounds of the object
* contain our bounds or 2) we are a leaf.
*
* key = Object
* value = Rectangle2D.Double
*/
private HashMap<T,Rectangle2D.Double> objects;
@Nullable private QuadNode northEast;
@Nullable private QuadNode northWest;
@Nullable private QuadNode southEast;
@Nullable private QuadNode southWest;
public QuadNode(Rectangle2D.Double bounds) {
this.bounds = bounds;
this.objects = new HashMap<T,Rectangle2D.Double>();
}
public boolean isLeaf() {
return northEast == null;
}
public void remove(T o) {
if (objects.remove(o) == null && ! isLeaf()) {
northEast.remove(o);
northWest.remove(o);
southEast.remove(o);
southWest.remove(o);
}
}
public void add(T o, Rectangle2D.Double oBounds) {
// Do we have to split?
if (isLeaf()
&& objects.size() >= maxCapacity
&& bounds.width > minSize && bounds.height > minSize) {
split();
}
if (isLeaf() || oBounds.contains(bounds)) {
// We put an object into our hashtable if we are
// a leaf, or if the bounds of the object contain our bounds.
objects.put(o, oBounds);
} else {
if (northEast.bounds.intersects(oBounds)) {
northEast.add(o, oBounds);
}
if (northWest.bounds.intersects(oBounds)) {
northWest.add(o, oBounds);
}
if (southEast.bounds.intersects(oBounds)) {
southEast.add(o, oBounds);
}
if (southWest.bounds.intersects(oBounds)) {
southWest.add(o, oBounds);
}
}
}
public void split() {
if (isLeaf()) {
double hw = bounds.width / 2;
double hh = bounds.height / 2;
northWest = new QuadNode(
new Rectangle2D.Double(bounds.x, bounds.y, hw, hh)
);
northEast = new QuadNode(
new Rectangle2D.Double(bounds.x + hw, bounds.y, bounds.width - hw, hh)
);
southWest = new QuadNode(
new Rectangle2D.Double(bounds.x, bounds.y + hh, hw, bounds.height - hh)
);
southEast = new QuadNode(
new Rectangle2D.Double(bounds.x + hw, bounds.y + hh, bounds.width - hw, bounds.height - hh)
);
HashMap<T,Rectangle2D.Double> temp = objects;
objects = new HashMap<T,Rectangle2D.Double>();
for (Map.Entry<T,Rectangle2D.Double> entry : temp.entrySet()) {
add(entry.getKey(), entry.getValue());
}
}
}
public void join() {
if (! isLeaf()) {
northWest.join();
northEast.join();
southWest.join();
southEast.join();
objects.putAll(northWest.objects);
objects.putAll(northEast.objects);
objects.putAll(southWest.objects);
objects.putAll(southEast.objects);
northWest = null;
northEast = null;
southWest = null;
southEast = null;
}
}
public void findContains(Point2D.Double p, HashSet<T> result) {
if (bounds.contains(p)) {
for (Map.Entry<T,Rectangle2D.Double> entry : objects.entrySet()) {
if (entry.getValue().contains(p)) {
result.add(entry.getKey());
}
}
if (! isLeaf()) {
northWest.findContains(p, result);
northEast.findContains(p, result);
southWest.findContains(p, result);
southEast.findContains(p, result);
}
}
}
public void findIntersects(Rectangle2D.Double r, HashSet<T> result) {
if (bounds.intersects(r)) {
for (Map.Entry<T,Rectangle2D.Double> entry : objects.entrySet()) {
if (entry.getValue().intersects(r)) {
result.add(entry.getKey());
}
}
if (! isLeaf()) {
northWest.findIntersects(r, result);
northEast.findIntersects(r, result);
southWest.findIntersects(r, result);
southEast.findIntersects(r, result);
}
}
}
public void findInside(Rectangle2D.Double r, HashSet<T> result) {
if (bounds.intersects(r)) {
for (Map.Entry<T,Rectangle2D.Double> entry : objects.entrySet()) {
if (r.contains(entry.getValue())) {
result.add(entry.getKey());
}
}
if (! isLeaf()) {
northWest.findInside(r, result);
northEast.findInside(r, result);
southWest.findInside(r, result);
southEast.findInside(r, result);
}
}
}
}
}