// BGRoll.java
// Draw Rolling String
// by nagatani@eken.phys.nagoya-u.ac.jp

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

public class BGRoll extends StringRoll {
	
	int	xOffset;
	int	xPos,	yPos;

	BGRoll (Image imageBG, int xOffset, Applet applet) {
		
		super (imageBG, 0, 0, applet);
		this.xOffset = xOffset;
		nMode = 0;
	}
	
	public void paint (Graphics g, Applet applet) {
		
		g.drawImage (imageString, xPos, yPos - yImage, applet);
		if (yPos < yWindow)
			g.drawImage (imageString, xPos, yPos, applet);
	}
	
	public void move () {
		
		// Every Time Displaying Mode
		
		double	T = t +	0.03  * Math.sin ( 3 * 2.0*Math.PI*t + 1)
			      +	0.01  * Math.sin ( 5 * 2.0*Math.PI*t + 2)
			      +	0.003 * Math.sin (14 * 2.0*Math.PI*t + 3);
		xPos = (int) (xOffset
				+  5 * Math.sin ( 2 * 2.0*Math.PI*t + 0)
				+  3 * Math.sin ( 6 * 2.0*Math.PI*t + 1)
				+  2 * Math.sin (10 * 2.0*Math.PI*t + 2));
		yPos = (int) ((1.0 - T) * yImage);
		
		t += 0.01;
		if (t >= 1.0) {
			t = 0.0;
		}
		return;
	}
}