Need More Mouse Events

Question

[http://forums.sun.com/thread.jspa?messageID=10811388|http://forums.sun.com/thread.jspa?messageID=10811388]
During search over net I found the above thread and it seems to be describing the same problem which I am also facing. For my application also I need to capture all the mouse events while dragging. I tried the soluiotn mentioned at this thread to solve this problem by overrinding the below method in several ways:
protected AWTEvent coalesceEvents(AWTEvent existingEvent,AWTEvent newEvent);
Even after several attempts, I could not succeed. Can you please suggest how to do that. I was not able to reply to above thread so creating this new thread.
Thanks

Answer 1

I wanted to see if a timer based approach does indeed produce a smoother curve than just simply listening for mouse drag events. What I came up with below was the resulting test code. Lo and behold, using a timer does indeed produce a smoother curve. But it wasn't because it was capturing more mouse positions, it was because it was capturing less. Ain't that a kicker? Another interesting thing is that according to the source code, coalesceEvents is a no-op. The documentation, however, would have you believe that it coalesces mouse events as I thought it did.
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.GeneralPath;
import javax.swing.SwingUtilities;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.BorderFactory;
public class Test {
    private static class TimerBasedPanel extends JPanel implements MouseListener {
        private GeneralPath line;
        private Timer mousePosQuerier;
        private Component mouseEvtSource;
        private int pointCount;
        public TimerBasedPanel(Component mouseEventSource) {
            mousePosQuerier = new Timer(15, new ActionListener() {
                Point lastMousePoint = new Point(-1, -1);
                public void actionPerformed(ActionEvent e) {
                    Point p = MouseInfo.getPointerInfo().getLocation();
                    if (p.x != lastMousePoint.x || p.y != lastMousePoint.y) {
                        lastMousePoint.setLocation(p);
                        SwingUtilities.convertPointFromScreen(p, mouseEvtSource);
                        line.lineTo(p.x, p.y);
                        pointCount++;
                        repaint();
            mouseEvtSource = mouseEventSource;
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            if(line != null) {
                ((Graphics2D) g).draw(line);
        public void mousePressed(MouseEvent e) {
            line = new GeneralPath();
            line.moveTo(e.getX(), e.getY());
            pointCount = 1;
            mousePosQuerier.start();
        public void mouseReleased(MouseEvent e) {
            mousePosQuerier.stop();
            repaint();
            System.out.println("Timer Based, Points Captured: " + pointCount);
        public void mouseEntered(MouseEvent e){}
        public void mouseExited(MouseEvent e){}
        public void mouseClicked(MouseEvent e){}
    private static class DragEventsPanel extends JPanel
            implements MouseListener, MouseMotionListener{
        private GeneralPath line;
        private int pointCount;
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            if(line != null) {
                ((Graphics2D) g).draw(line);
        public void mousePressed(MouseEvent e) {
            line = new GeneralPath();
            line.moveTo(e.getX(), e.getY());
            pointCount = 1;
        public void mouseDragged(MouseEvent e) {
            pointCount++;
            line.lineTo(e.getX(),e.getY());
            repaint();
        public void mouseReleased(MouseEvent e){
            System.out.println("DragEvent Based, Points Captured: " + pointCount);
        public void mouseEntered(MouseEvent e){}
        public void mouseExited(MouseEvent e){}
        public void mouseClicked(MouseEvent e){}
        public void mouseMoved(MouseEvent e) {}
    public static void main(String args[]) {
        JFrame frame = new JFrame();
        JPanel drawPanel = new JPanel() {
            @Override
            protected AWTEvent coalesceEvents(AWTEvent existingEvent,
                                              AWTEvent newEvent) {
                if(newEvent.getID() == MouseEvent.MOUSE_DRAGGED) {
                    return null;
                }else {
                    return super.coalesceEvents(existingEvent, newEvent);
        TimerBasedPanel timerPanel = new TimerBasedPanel(drawPanel);
        DragEventsPanel dragPanel = new DragEventsPanel();
        drawPanel.setBorder(BorderFactory.createTitledBorder("Draw here"));
        timerPanel.setBorder(BorderFactory.createTitledBorder("Uses a timer"));
        dragPanel.setBorder(BorderFactory.createTitledBorder("Listens for drag events."));
        drawPanel.addMouseListener(timerPanel);
        drawPanel.addMouseListener(dragPanel);
        drawPanel.addMouseMotionListener(dragPanel);
        frame.setLayout(new java.awt.GridLayout(0,3));
        frame.add(drawPanel);
        frame.add(timerPanel);
        frame.add(dragPanel);
        frame.setSize(600,200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
}Edited by: Maxideon on Sep 16, 2009 9:56 PM
Minor error, but now fixed.