Name: rlT66838 Date: 07/08/99


I discovered my Java application to hang while zooming in on
a graphics repaint while drawing lines.

I experimented and determined it happens with
drawLine(x1,y1,x2,y2) when (x2-x1)*(y2-y1)>2^30 or so.

This happens for lines as small as drawLine(0,0,32900,32900).
That's significantly larger than the screen resolution,
but when I'm zooming in on a small part of my image, this
happens quite easily.

Included is an example program. It draws:
drawLine(0,0,rad,rad), with rad=32000 and each time a
"repaint" button is pressed, rad is increased by 100.
Pressing "repaint" 9 times will cause it to fail at rad=32900.

I used this program to test the limits. The error will occur
on any little program with a drawLine which exceeds this limit.

In the very least, the bug should be fixed so the program
doesn't hang - it could just draw nothing.

Thanks!

********************************
//redraw4.java
//7/7/99

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class redraw4 extends JFrame
  implements ActionListener
{
  static redraw4 frame = new redraw4("Drawing test");
  static Dimension d=new Dimension(200,200);

  test t=new test();
  int rad=32000;

  redraw4(String x)
  {
    super(x);

    Container c=getContentPane();
    c.setLayout(new BorderLayout());
    c.add(t,BorderLayout.CENTER);
    Button b=new Button("repaint");
    b.addActionListener(this);
    c.add(b,BorderLayout.NORTH);
  }

  public void actionPerformed(ActionEvent e)
  {
    String arg = e.getActionCommand();
    if (arg.equals("repaint")) t.repaint();
  }

  public static void main(String[] args)
  {
      frame.addWindowListener
      ( //allow application to close with x button.
        new WindowAdapter()
        {
          public void windowClosing(WindowEvent e) {System.exit(0);}
        }
      );

      frame.pack();
      frame.setVisible(true);
  }

  class test extends JPanel
  {
    public test()
    {
      super();
    }

    public Dimension getPreferredSize() { return d; }

    public void draw(Graphics g)
    {
      g.setXORMode(getBackground());
      g.setColor(Color.white);
      g.setPaintMode();
      g.drawString("drawLine(0,0,"+rad+","+rad+")",10,100);
      g.drawLine(0,0,rad,rad);
      rad=(int)(rad+100);
    }

    public void paint(Graphics g)
    {
      super.paint(g);
      draw(g);
    }
  }
}
(Review ID: 85334)
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