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/* Java Lab 1 i Programspråk                      */
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/* Textsträng som fladdrar runt i appleten        */
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/* Christian Ohlsson di7chro@cse.kau.se           */
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import java.applet.*;
import java.awt.*;
import java.awt.image.*;

public class HelloWorld extends Applet
    implements Runnable {
    
    Thread animationThread = null;
    int delay=100, xspeed, yspeed;
    int xsize, ysize, xOffset, yOffset, helloTextWidth,
	helloTextHeight;
    Image backBuffer;
    Graphics backGC; // Graphics Context
    String helloText;
    
    // Initialize the Applet
    public void init() {
	xsize=getSize().width;
	ysize=getSize().height;
	backBuffer = createImage(xsize, ysize);
	backGC = backBuffer.getGraphics();
	
	// Get the text from the html page that the user wants to scroll
	helloText=getParameter("text");
	String s=getParameter("speed");
	xspeed=yspeed= Integer.parseInt(s);
	
	// Calculate the real size of the string using the font
	FontMetrics fontInfo=backGC.getFontMetrics();
	helloTextWidth=fontInfo.stringWidth(helloText);
	helloTextHeight=fontInfo.getHeight();
	xOffset=5;
	yOffset=5;
	yOffset=helloTextHeight;
    }

    // This method is called when the applet becomes visible
    public void start() {
	// Create a thread and start it
	if(animationThread == null) {
	    animationThread = new Thread(this);
	    animationThread.start();
	}
    }

    // This method is called when the applet becomes invisible
    public void stop() {
	// Stop animation thread
	animationThread = null;
    }

public void run() {
        long time = System.currentTimeMillis();
        while(animationThread != null) {
            // Use a constant frame rate based on the system clock
            try {
                time += delay;
                Thread.sleep(Math.max(0, time -
                                      System.currentTimeMillis()));
            } catch (InterruptedException e) {}
            
            // initiate a repaint of the screen
            repaint();
        }
    }

    public void paint(Graphics g) {
        // Clear the screen
        backGC.setColor(Color.yellow);
        backGC.fillRect(0,0,xsize,ysize);
        
        // Draw text 
        backGC.setColor(Color.black);
        backGC.drawString(helloText, xOffset, yOffset);
        
        xOffset-=xspeed;
	if(xOffset <= 1)
		xspeed = -xspeed;
	if(xOffset+helloTextWidth >= xsize)
		xspeed = -xspeed;

        yOffset-=yspeed;
	if(yOffset <= 5)
		yspeed = -yspeed;

	if(yOffset+helloTextHeight >= ysize)
		yspeed = -yspeed;

        // Copy the backbuffer to the screen
        g.drawImage(backBuffer, 0, 0, this);
    }
    public void update(Graphics g) {
	paint(g);
    }

}