Re: thread-safe graphics access

In article <4a3f904c$0$23641$b9f67a60@news.newsdemon.com>,
Knute Johnson <nospam@rabbitbrush.frazmtn.com> wrote:
[...]


Thanks for this interesting example. I was intrigued by the variability
in frame rate as a function of angle and size, which your approach
highlights. For comparison, I tried transforming a Polygon, translating,
scaling and rotating as the panel's size changes:

<code>
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.image.*;
import java.lang.reflect.*;
import javax.swing.*;

public class Rotate extends JPanel implements Runnable {

   private volatile BufferedImage bi;
   private volatile long then;
   private Thread thread;
   private double angle;
   private int n;
   private double rate;
   private static final AffineTransform at = new AffineTransform();
   private static final Polygon poly = new Polygon();
   static {
       poly.addPoint( 1, -1);
       poly.addPoint( 1, 1);
       poly.addPoint(-1, 1);
       poly.addPoint(-1, -1);
   }

   public Rotate() {
       setPreferredSize(new Dimension(400, 400));
       addComponentListener(new ComponentAdapter() {
           @Override
           public void componentResized(ComponentEvent ce) {
               GraphicsConfiguration gc = getGraphicsConfiguration();
               bi = gc.createCompatibleImage(
                   getWidth(), getHeight(), BufferedImage.OPAQUE);
           }
       });
   }

   public void start() {
       then = System.nanoTime();
       thread = new Thread(this);
       thread.start();
   }

   public void stop() {
       thread.interrupt();
   }

   public void run() {
       try {
           while (true) {
               render();
               try {
                   EventQueue.invokeAndWait(new Runnable() {
                       public void run() {
                           paintImmediately(getBounds());
                       }
                   });
               } catch (InvocationTargetException ite) {
                   System.out.println(ite);
               }
           }
       } catch (InterruptedException ie) {
           System.out.println(ie);
       }
   }

   private void render() {
       int w = getWidth();
       int h = getHeight();
       Graphics2D g = bi.createGraphics();
       g.setRenderingHint(
           RenderingHints.KEY_ANTIALIASING,
           RenderingHints.VALUE_ANTIALIAS_ON);
       g.setColor(Color.WHITE);
       g.fillRect(0, 0, w, h);
       g.setColor(Color.RED);
       g.drawString(String.format("%5.1f", rate), 5, 12);
       angle += 0.001;
       at.setToIdentity();
       at.translate(w/2, h/2);
       at.scale(w/3, h/3);
       at.rotate(angle);
       g.setColor(Color.BLUE);
       g.fill(at.createTransformedShape(poly));
       if (++n % 100 == 0) {
           long now = System.nanoTime();
           rate = 100000000000.0 / (now - then);
           then = now;
       }
       g.dispose();
   }

   public void paintComponent(Graphics g) {
       g.drawImage(bi, 0, 0, null);
   }

   public static void main(String[] args) {
       final Rotate rotate = new Rotate();
       final JFrame f = new JFrame();
       f.addWindowListener(new WindowAdapter() {
           public void windowOpened(WindowEvent we) {
               rotate.start();
           }
           public void windowClosing(WindowEvent we) {
               rotate.stop();
               f.dispose();
           }
       });
       f.add(rotate, BorderLayout.CENTER);
       f.pack();
       f.setVisible(true);
   }
}
</code>