High CPU consumption with repaint while dragging

Question

Hi! I certainly hope someone can help me with this. I am building a graphical user interface for a graph with custom nodes and edges, the nodes being draggable. I have tried making each network component (node or edge) a JComponent. Now, I'm trying using only one JPanel to paint all the components. Either way, I find that dragging takes up too much CPU % especially when using full screen graphics, usually around 92%. And that is on a machine with >1.9GHz.
It does not really make much of a difference when I paint outlines of the components while dragging. Any ideas about this? Thanks.
My runnable test code is rather long so I've uploaded it to : http://web.mit.edu/jabos/www/SyncTest/GUILoad2.java.
-Bosun

Answer 1

Comments about changes to your code:
1 - trouble in rendering with setOpaque(false). Set this to true and add super.paintComponent(g) in paintComponent to take care of background paint updates
2 - had to doctor your ConnComp class; the constructor was under construction...
3 - I'm using j2se 1.4 so I converted your:
ArrayList generics to the old Object casts and
the JFrame setPreferredSize to setSize
This runs okay now. The highest cpu usage numbers I saw were 52% in full screen and 37% in regular mode (2.6 GHz).
The painting part seems okay; I think the trouble is in excessive data storage and manipulation. I would re–design your program to eliminate all the type checking with the instanceof operator. Specifically I would try to use only one ArrayList for the node objects and draw the connection lines between them inside paintComponent depending on how a boolean is set, eg if(showLines). As an aside, GradientPaint is for fill operations and will not benefit your line display.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.ArrayList;
* This demo paints all network components in a single JComponent
* @author jabos
public class DragTest extends JPanel {
     * all components
    public ArrayList comps;
    public ArrayList compsDragged; // actually only RectComps
     * arraylist of all connection components
    public ArrayList conncomps;
    public boolean dragging = false, repaintWhileDragging = true;
    Point2D initp = null;
    public JLabel repaintDrag;
    public DragTest() {
        repaintDrag = new JLabel("repaintWhileDragging : " + repaintWhileDragging);
        repaintDrag.setForeground(Color.MAGENTA);
        add(repaintDrag);
        add(new JLabel("Press \"R\" to change repaint protocols during dragging"));
        comps = new ArrayList();
        compsDragged = new ArrayList();
        conncomps = new ArrayList();
        addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseDragged(MouseEvent e) {
                //* // Remove initial slash to disable repainting while dragging
                if (repaintWhileDragging) {
                    Point2D pp = e.getPoint();
                    AffineTransform t = AffineTransform.getTranslateInstance(
                                                pp.getX() - initp.getX(),
                                                pp.getY() - initp.getY());
                    initp = pp; // reset initp
                    for (int j = 0; j < compsDragged.size(); j++) {
                        Comp comp = (Comp)compsDragged.get(j);
                        if (comp instanceof RectComp)
                            comp.updateCompLocation(t);
                    // and again to update ConnComps
                    for (int j = 0; j < conncomps.size(); j++) {
                        Comp comp = (Comp)conncomps.get(j);
                        if (comp instanceof ConnComp)
                            comp.updateCompLocation(t);
                    dragging = true;
                    repaint();
                dragging = true;
        addMouseListener(new MouseAdapter() {
            // does final repaint if dragging just finished
            public void mouseReleased(MouseEvent e) {
                if (dragging) {
                    Point2D pp = e.getPoint();
                    AffineTransform t = AffineTransform.getTranslateInstance(
                                                pp.getX() - initp.getX(),
                                                pp.getY() - initp.getY());
                    for (int j = 0; j < compsDragged.size(); j++) {
                        Comp comp = (Comp)compsDragged.get(j);
                        if (comp instanceof RectComp)
                            comp.updateCompLocation(t);
                    // and again to update ConnComps
                    for (int j = 0; j < conncomps.size(); j++) {
                        Comp comp = (Comp)conncomps.get(j);
                        if (comp instanceof ConnComp)
                            comp.updateCompLocation(t);
                repaint();
                dragging = false;
                setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
            // Updates list of components being dragged
            public void mousePressed(MouseEvent e) {
                compsDragged.clear();
                initp = e.getPoint();
                for (int j = 0; j < comps.size(); j++) {
                    Comp comp = (Comp)comps.get(j);
                    if (comp.graphic.contains(initp))
                        compsDragged.add(comp);
                setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR));
        addKeyListener(new KeyAdapter() {
            public void keyReleased(KeyEvent e) {
                if(e.getKeyCode() == KeyEvent.VK_R) {
                    repaintWhileDragging = !repaintWhileDragging;
                    repaintDrag.setText("repaintWhileDragging : " +
                                         repaintWhileDragging);
//        setOpaque(false);
        setFocusable(true);
        requestFocusInWindow();
    public static void main(String[] args) {
        GraphicsDevice device =
            GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
        JFrame f = new JFrame("GUILOAD2", device.getDefaultConfiguration());
        //* // remove initial slash to disable full screen
        device.setFullScreenWindow(SwingUtilities.getWindowAncestor(f));
        //needs to be set AFTER fullscreenmode so that the toolbar is NOT draggable!
        f.setExtendedState(JFrame.MAXIMIZED_BOTH);
            // enable use of Look and Feel
            f.setUndecorated(true);    // Set false, EE is still minimizable
            f.getRootPane().setWindowDecorationStyle(JRootPane.FRAME);
        f.setBounds(GraphicsEnvironment.getLocalGraphicsEnvironment().
                            getMaximumWindowBounds());
        DragTest p = new DragTest();
        p.setBackground(Color.WHITE);
        RectComp[] rc = new RectComp[100];
        int n = -1, x = 30, y = 30, b = 100, inc = 40;
        // add REctComps
        for (int i = 0; i < 10; i++) {
            p.add(rc[++n] = new RectComp(new Point2D.Double(x += inc, y += inc),
                                         new Color(x % 255, y % 255, (b += 10) % 255)));
        x = 34; y = 32; b = 32;
        // add ConnComps
        while (n > 0) {
            p.add(new ConnComp(rc[n--], rc[n],
                               new Color((x += inc) % 255, (y += inc) % 255,
                                         (b += inc) % 255),
                               new Color((x += inc) % 255, (y += inc) % 255,
                                         (b += inc) % 255)));
        f.setContentPane(p);
        f.setSize(700, 700);
        makeFramex(f, false);
        /* // remove initial slash to disable full screen; Also, uncomment above
        f.setResizable(false);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setIgnoreRepaint(true);
        f.setVisible(true);
    public static void makeFramex(JFrame frame, boolean resizable) {
        frame.setSize(frame.getSize());
//        frame.setResizable(resizable);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//        frame.pack();
        frame.setVisible(true);
     * Adds network component c to this simulation
     * @param c
    public void add(Comp c) {
        comps.add(c);
        if (c instanceof ConnComp) {
            conncomps.add((ConnComp)c);
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2D = (Graphics2D) g;
        g2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                             RenderingHints.VALUE_ANTIALIAS_ON);
        for (int j = 0; j < comps.size(); j++) {
            Comp comp = (Comp)comps.get(j);
            //for (Comp i : dragging ? compsDragged : comps) {
            try {
                g2D.setPaint(comp.color);
                if (comp instanceof ConnComp) {
                    g2D.setStroke(((ConnComp) comp).compStroke);
                    g2D.draw(comp.graphic);
                if (comp instanceof RectComp)
                    g2D.fill(comp.graphic);
            } catch (Exception e) {
                e.printStackTrace();  //To change body of catch statement
                                      // use File | Settings | File Templates.
     * A network component that simulates a node
    private static class RectComp extends Comp {
        RectComp(Point2D centero, Paint c) {
            super(c);
            center = centero;
            graphic = new Ellipse2D.Double(center.getX() - radius,
                              center.getY() - radius, radius * 2 - 2, radius * 2 - 2);
        public void updateCompLocation(AffineTransform t) {
            graphic = t.createTransformedShape(graphic);
            Rectangle2D r = graphic.getBounds2D();
            center = new Point2D.Double(r.getCenterX(), r.getCenterY());
            //System.out.println("newCenterX=" + r.getCenterX());
     * A network component that simulates a connection between two nodes
    private static class ConnComp extends Comp {
        Stroke compStroke;
        RectComp origin, destination;
        Paint color;
        ConnComp(RectComp origino, RectComp desto, Color c1, Color c2) {
            super(c1);
            if (c2 != null)
                color = new GradientPaint(origino.center, c1, desto.center, c2);
            else
                color = c1;
            graphic = new Line2D.Double(origino.center, desto.center);
            this.origin = origino;
            this.destination = desto;
            compStroke = new BasicStroke(3);
//            updateCompLocation(new AffineTransform());
        public void updateCompLocation(AffineTransform t) {
            ((Line2D)graphic).setLine(origin.center, destination.center);
            if(color instanceof GradientPaint)
                color = new GradientPaint(((Line2D)graphic).getP1(),
                                          ((GradientPaint)color).getColor1(),
                                          ((Line2D)graphic).getP2(),
                                          ((GradientPaint)color).getColor2());
            //System.out.println("newLineX:" + ((Line2D) graphic).getX1() +
            //                     "---" + ((Line2D) graphic).getX2());
     * demo Superclass for all network components
    private abstract static class Comp {
        Point2D center;
        Shape graphic;
        int radius = 20;
        Paint color;
        Comp(Paint c) {
            color = c;
         * Updates internal parameters of Comp necessary for correct repaint
         * @param t
        public abstract void updateCompLocation(AffineTransform t);
}