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

public class Lissajous extends JApplet implements ActionListener {
    
    private JLabel stepsLabel, aLabel, bLabel, cLabel, nLabel, infoLabel;
    private JTextField stepsField, aField, bField, cField, nField;
    private final int A=100, B=100, C=100, N=10, STEPS=1000;
    private int steps=STEPS;
    private double a=A, b=B, c=C, n=N;
    
    public void init() {

	Container container = getContentPane();  
	container.setLayout( new FlowLayout() ); 

	infoLabel = new JLabel( "x(t)=a sin(nt+c), y(t)=b sin(t)    " );
	container.add( infoLabel );

	aLabel = new JLabel( "a" );
	aField = new JTextField( 4 );
	aField.setText(""+A);
	container.add( aLabel );
	container.add( aField );

	bLabel = new JLabel( "b" );
	bField = new JTextField( 4 );
	bField.setText(""+B);
	container.add( bLabel );
	container.add( bField );

	cLabel = new JLabel( "c" );
	cField = new JTextField( 4 );
	cField.setText(""+C);
	container.add( cLabel );
	container.add( cField );

	nLabel = new JLabel( "n" );
	nField = new JTextField( 4 );
	nField.setText(""+N);
	container.add( nLabel );
	container.add( nField );

	stepsLabel = new JLabel( "Steps" );
	stepsField = new JTextField( 4 );
	stepsField.setText(""+STEPS);
	container.add( stepsLabel );
	container.add( stepsField );

	aField.addActionListener( this ); 
	bField.addActionListener( this ); 
	cField.addActionListener( this ); 
	nField.addActionListener( this ); 
	stepsField.addActionListener( this ); 

    }
    
    public void actionPerformed( ActionEvent event ) {
	if ( event.getSource() == aField )
	    a = Double.parseDouble( event.getActionCommand());
	else if ( event.getSource() == bField )
	    b = Double.parseDouble( event.getActionCommand());
	else if ( event.getSource() == cField )
	    c = Double.parseDouble( event.getActionCommand());
	else if ( event.getSource() == nField )
	    n = Double.parseDouble( event.getActionCommand());
	else if ( event.getSource() == stepsField )
	    steps = Integer.parseInt( event.getActionCommand());
	
	//whichever textfield changed, re-paint
	repaint();
    }
    
    public void paint( Graphics g ) {
	super.paint( g );
	
	int x1=0, y1=0, x2, y2;   //initialize to avoid syntax error

	g.setColor(new Color(80,80,80));
	g.drawLine(getWidth()/2,0,getWidth()/2,getHeight());
	g.drawLine(0,getHeight()/2,getWidth(),getHeight()/2);

	g.setColor(new Color(255,0,0));
	
	for (int t=1; t<=steps; t++) {
	    //circle:
	    //		x1 = x2 = (int)(Math.cos(t) * a) + getWidth()/2;
	    //y1 = y2 = (int)(Math.sin(t) * a) + getHeight()/2;
	   
	    //Lissajous:
	    x2 = (int)(Math.sin(n*t+c) * a) + getWidth()/2;
	    y2 = (int)(Math.sin(t) * b) + getHeight()/2;
	    
	    if (t > 1)    //skip first
		g.drawLine(x1,y1,x2,y2);

	    x1 = x2;
	    y1 = y2;
	}
    }
}