how to determine on what segment a point is in

import java.awt.*;

import java.awt.event.*;

import java.awt.geom.*;

import javax.swing.*;

public class ProximityTest extends JPanel {

Color[] colors = { Color.red, Color.green.darker(), Color.blue };

Line2D.Double[] lines;

Point probe;

Point offset = new Point(5,20);

JLabel lineLabel;

JLabel distLabel;

public ProximityTest() {

lines = new Line2D.Double[3];

lines[0] = new Line2D.Double(50,50,350,250);

lines[1] = new Line2D.Double(50,350,375,150);

lines[2] = new Line2D.Double(100,50,150,350);

probe = new Point();

addMouseMotionListener(mml);

}

protected void paintComponent(Graphics g) {

super.paintComponent(g);

Graphics2D g2 = (Graphics2D)g;

g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,

RenderingHints.VALUE_ANTIALIAS_ON);

for(int j = 0; j < lines.length; j++) {

g2.setPaint(colors[j]);

g2.draw(lines[j]);

}

g2.setPaint(Color.red);

g2.fill(new Ellipse2D.Double(probe.x-2,probe.y-2,4,4));

}

private void checkProximity() {

int index = -1;

double min = Double.MAX_VALUE;

for(int j = 0; j < lines.length; j++) {

double distance = lines[j].ptSegDist(probe);

if(distance < min) {

min = distance;

index = j;

}

}

lineLabel.setForeground(colors[index]);

distLabel.setText(String.format("%.1f", min));

}

private JPanel getLast() {

lineLabel = new JLabel("line");

distLabel = new JLabel(" ");

Dimension d = distLabel.getPreferredSize();

d.width = 45;

distLabel.setPreferredSize(d);

JPanel panel = new JPanel(new GridBagLayout());

GridBagConstraints gbc = new GridBagConstraints();

gbc.insets = new Insets(2,2,2,2);

gbc.anchor = GridBagConstraints.WEST;

gbc.weightx = 1.0;

panel.add(new JLabel(), gbc);

gbc.weightx = 0;

panel.add(new JLabel("closest"), gbc);

panel.add(lineLabel, gbc);

panel.add(distLabel, gbc);

gbc.weightx = 1.0;

panel.add(new JLabel(), gbc);

return panel;

}

public static void main(String[] args) {

ProximityTest test = new ProximityTest();

JFrame f = new JFrame();

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.getContentPane().add(test);

f.getContentPane().add(test.getLast(), "Last");

f.setSize(400,400);

f.setLocation(200,200);

f.setVisible(true);

}

private MouseMotionListener mml = new MouseMotionAdapter() {

public void mouseMoved(MouseEvent e) {

Point p = e.getPoint();

probe.setLocation(p.x-offset.x, p.y-offset.y);

checkProximity();

repaint();

}

};

}

crwooda at 2007-7-29 14:01:44 >