import java.awt.*;
import java.applet.*;

public class beats extends Applet {
	public Image offScreenImage;
	mycan c;
	public int f1 = 57;
	public int f2 = 50;

	public void init() {
		super.init();
		setBackground(Color.white);
		offScreenImage = createImage(500,180);
		c = new mycan(this,offScreenImage);

		//{{INIT_CONTROLS
		setLayout(new BorderLayout(0,0));
		resize(500,200);
		panel1 = new java.awt.Panel();
		panel1.setLayout(new GridLayout(0,6,0,0));
		panel1.reshape(0,150,500,50);
		add("South", panel1);
		f1Scroll = new java.awt.Scrollbar(Scrollbar.HORIZONTAL,57,0,1,100);
		f1Scroll.reshape(0,0,83,50);
		panel1.add(f1Scroll);
		label1 = new java.awt.Label("f1 = 57 Hz");
		label1.reshape(83,0,83,50);
		panel1.add(label1);
		labelBlank1 = new java.awt.Label("");
		labelBlank1.reshape(166,0,83,50);
		panel1.add(labelBlank1);
		f2Scroll = new java.awt.Scrollbar(Scrollbar.HORIZONTAL,50,0,1,100);
		f2Scroll.reshape(249,0,83,50);
		panel1.add(f2Scroll);
		label2 = new java.awt.Label("f2 = 50 Hz");
		label2.reshape(332,0,83,50);
		panel1.add(label2);
		//}}
		add("Center",c);
	}

	public boolean handleEvent(Event evt) {
		if(evt.target == f1Scroll){
			f1 = f1Scroll.getValue();
			label1.setText("f1 = "+f1+" Hz");
			c.repaint();
			return true;
		}
		if(evt.target == f2Scroll){
			f2 = f2Scroll.getValue();
			label2.setText("f2 = "+f2+" Hz");
			c.repaint();
			return true;
		}
		return super.handleEvent(evt);
	}

	//{{DECLARE_CONTROLS
	java.awt.Panel panel1;
	java.awt.Scrollbar f1Scroll;
	java.awt.Label label1;
	java.awt.Label labelBlank1;
	java.awt.Scrollbar f2Scroll;
	java.awt.Label label2;
	//}}
}

class mycan extends java.awt.Canvas
{
	public double scale=0.003;
	public int phase = 0;
	public int x0 = 0;
	Image offScreenImage;
	beats a;
	
	public mycan(beats myApplet, Image myImage) {
		offScreenImage = myImage;
		a = myApplet;
		resize(500,180);
		repaint();
	}

	public void update(Graphics g){
		Graphics offg = offScreenImage.getGraphics();
		paint(offg);
		g.drawImage(offScreenImage, 0, 0, this);
	}
	
	public void paint(Graphics g){
		int y1 = 0;
		g.setColor(Color.white);                                   // background
		g.fillRect(0,0,500,180);
		g.setColor(Color.black);                                   // axis
		g.drawLine(0,90,500,90);
		/*
		g.setColor(Color.pink);                                    // envelope
		for (int i=1; i<500; i++) {
			int y = 90 + (int)(80.0*Math.cos((phase+i)*scale*(a.f1-a.f2)));
			if (i>1) {
				g.drawLine(i-1,y1,i,y);
				g.drawLine(i-1,180-y1,i,180-y);
			}
			y1 = y;
		}
		*/
		g.setColor(Color.red);                                     // beats
		for (int i=1; i<500; i++) {
			int y = 90 + (int)(80.0*Math.cos((-phase+i)*scale*(a.f1-a.f2))
			                        *Math.sin((-phase+i)*scale*(a.f1+a.f2)));
			if (i>1) g.drawLine(i-1,y1,i,y);
			y1 = y;
		}
	}
	public boolean handleEvent(Event evt){
		if (evt.target == this && evt.id == Event.MOUSE_DOWN) {
			x0 = evt.x;
			return true;
		}
		if (evt.target == this && evt.id == Event.MOUSE_DRAG) {
			phase = evt.x - x0;
			repaint();
			return true;
		}
		return false;
	}
}