/** Henon's Strange Attractor Generator 
  * Author: Robert John Morton 
  * Originated as an applet  
  * Finished 30 October 1997
  * Converted to a JFramed application  */

/* Open a terminal and change directory to where this file is loacated.
   To compile this program, enter the terminal command: javac henon.java
   To run this program, enter the terminal command: java henon */

import javax.swing.*;
import java.awt.Dimension;  // to be able to set the preferred JFrame size
import java.awt.Color;      // to be able to set JFrame background colour

public class henon extends JFrame {

  private int
    XE = 345,  // Horizontal extent of window and JFrame.
    YE = 370;  // Vertical extent of window and JFrame.

  /* Declare a reference to an instance of the child class. Beware: an 
  instance of the child class cannot be created here because this 
  must be done within the invokeAndWait environment. */
  private hengraph LG; 

  public henon() {  // construct an instance of this extended JFrame

    // set window frame title on title bar
    super("Hénon's Strange Attractor");

    /* Set up the window listener to listen for the window close command which
    occurs when the user clicks on the X control in the window's title bar.*/
    setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

    /* Set the initial size of the extended JFrame. This is the area INSIDE 
    the frame. It does not include the border or the title bar areas. */
    setPreferredSize(new Dimension(XE,YE));

    setBounds(0,0,XE,YE);        // of area inside window frame
    setBackground(Color.black);  // default background colour of JFrame
    LG = new hengraph(XE,YE);    // Create new instance of henon class
    getContentPane().add(LG);    // and add it to the extended JFrame's pane.
    pack();                      // it should automatically pack to fill JFrame
    setVisible(true);            // make this extended JFrame visible
  }


  public static void main(final String[] args) {

    /* Initiate the creation of a new instance of this extended JFrame then
    wait until the building process has completely finished before giving
    the new instance of the child class permission to commence running. */

    try {
      javax.swing.SwingUtilities.invokeAndWait(
        new Runnable() {public void run() {new henon();}}
      );
    }
    catch(Exception e) {
       System.out.println("Couldn't create Swing GUI. You have probably");
       System.out.println("made a mistake in the constructor code of one");
       System.out.println("of this class's child classes.");
    }
  }

  /* The above try-catch sequence is necessary for the following reason. The 
  statement "new henon();" is a request to Swing to create a GUI instance
  of this application. It includes, in effect, all the statements in the
  constructor methods of all this class's child classes. All these requests
  are made on this, the main() program thread. 

  However, these requests are carried out [ie the actual constructing is
  done] by the underlying Swing system on the Event Despatching Thread. 
  The constructing process necessarily takes longer to do than the mere
  task of REQUESTING that the constructing be done. This means that the
  main() thread will set the run() thread in motion before the GUI has 
  finished being constructed. Hence trouble.

  The solution is to force the main() thread to withhold permission for 
  the run() thread to start its job until the Event Despatching Thread 
  has completely finished constructing the GUI. */

  /* NOTE: This class inherits a paint() method from the JFrame class that 
  it extends. This method automatically calls the paint() method of the
  child [extended JPanel] class when necessary. */
}