//
//  Snowfall.java - graphic animation
//
//  Dec-11-1996  0.01   North      Create
//  Dec-12-1996  0.02   North      Message Scroll
//

//
// usage:
// <applet code="Snowfall.class" width=XXX height=YYY>
//  <param name="delay" value="NNN">    <!-- flame delay[msec] -->
//  <param name="number" value="NNN">   <!-- number of pixels  -->
//  </applet>
//

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

//
// main class
//
public class Snowfall extends Applet implements Runnable {
	// animation properties
	Thread thAnimator;
	boolean bFrozen = false;
	Image iOffscreen = null;
	Graphics gOffscreen;
	int   nDelay = 100;
	int   nScreenWidth = 600;
	int   nScreenHeight = 400;
	// snow-pixels
	pixel snow[] = new pixel[300];
	int   nPixel;
	// message
	String sMessage = "Snowfall.java ver0.02";
	Color  cMesColor = new Color(255, 0, 0);
	int    nMesSize = 36;
	int    nMesWidth;
	int    cxMesPos;
	int    cyMesPos;

	public void init() {
		// get parameter
		getparam();

		// initialize screen
		resize(nScreenWidth, nScreenHeight);
		setBackground(Color.black);

		// initialize offscreen
		iOffscreen = createImage(nScreenWidth, nScreenHeight);
		gOffscreen = iOffscreen.getGraphics();

		// initialize pixels
		for (int i = 0; i < nPixel; i++) {
			snow[i] = new pixel();
			snow[i].init(nScreenWidth, 1000);
		}

		// initialize message
		if (sMessage != null) {
			Font f = new Font("TimesRoman", Font.ITALIC, nMesSize);
			FontMetrics fm = getFontMetrics(f);
			nMesWidth = fm.stringWidth(sMessage);
			cxMesPos = nScreenWidth + 20;
			cyMesPos = 40;
			gOffscreen.setFont(f);
		}
	}

	public void start() {
		if (!bFrozen) {
			if (thAnimator == null) {
				thAnimator = new Thread(this);
			}
			thAnimator.start();
		}
	}

	public void stop() {
		if (thAnimator != null) {
			thAnimator.stop();
			thAnimator = null;
		}
	}

	public boolean mouseDown(Event e, int x, int y) {
		if (thAnimator == null) {
			bFrozen = false;
			start();
		} else {
			bFrozen = true;
		}
		return true;
	}

	public void run() {
		// remember the starting time
		long nStartTime = System.currentTimeMillis();

		// animation loop
		Graphics g = getGraphics();
		while (!bFrozen) {
			// display
			paint(gOffscreen);
			g.drawImage(iOffscreen, 0, 0, this);

			// delay depending on how far we are behind
			try {
				nStartTime += nDelay;
				Thread.sleep(Math.max(0,
									  nStartTime - System.currentTimeMillis()));
			} catch (InterruptedException e) {
				break;
			}
		}
		thAnimator = null;
	}

	public void paint(Graphics g) {
		// paint background
		g.setColor(Color.black);
		g.fillRect(0, 0, nScreenWidth, nScreenHeight);

		// paint message
		if (sMessage != null) {
			g.setColor(cMesColor);
			g.drawString(sMessage, cxMesPos, cyMesPos);
			if (--cxMesPos + nMesWidth < 0) {
				cxMesPos = nScreenWidth + 20;
			}
		}
		// paint snow-pixels
		for (int i = 0; i < nPixel; i++) {
			//snow[i].erase(g);
			snow[i].drop(nScreenWidth, nScreenHeight);
			snow[i].paint(g);
		}
	}

	private void getparam() {
		String sParam;

		// screen size
		sParam = getParameter("width");
		if (sParam != null) {
			nScreenWidth = Integer.parseInt(sParam);
		}
		sParam = getParameter("height");
		if (sParam != null) {
			nScreenHeight = Integer.parseInt(sParam);
		}

		// number of snow-pixels
		nPixel = 100;
		sParam = getParameter("number");
		if (sParam != null) {
			nPixel = Integer.parseInt(sParam);
		}
		if (nPixel == 0) {
			nPixel = 50;
		} else if (nPixel > 300) {
			nPixel = 300;
		}

		// flame delay
		sParam = getParameter("delay");
		if (sParam != null) {
			nDelay = Integer.parseInt(sParam);
		}

		// message string
		sParam = getParameter("message");
		if (sParam != null) {
			sMessage = sParam;
		}

		// message size
		sParam = getParameter("point");
		if (sParam != null) {
			nMesSize = Integer.parseInt(sParam);
		}
	}
}

//
//  snow-pixel class
//
class pixel {
	public double cx, cy;
	public double dx, dy;
	int    nSize;

	public void init(int nWidth, int nHeight) {
		cx = Math.random() * nWidth - 10 + 5;
		cy = Math.random() * -nHeight;
		dx = Math.random() * 2 - 1;
		dy = Math.random() * 2 + 1;
		nSize = (dy > 2) ? 3 : 2;
	}

	public void drop(int nWidth, int nHeight) {
		cx += dx;
		cy += dy;
		if (cy > nHeight || cx < 0 || cx > nWidth) {
			init(nWidth, 0);
		}
		dx += Math.random() - 0.5;
		if (dx > 1) {
			dx = 1;
		} else if (dx < -1) {
			dx = -1;
		}
	}

	public void paint(Graphics g) {
		g.setColor(Color.white);
		g.fillRect((int)cx, (int)cy, nSize, nSize);
	}

	public void erase(Graphics g) {
		g.setColor(Color.black);
		g.fillRect((int)cx, (int)cy, nSize, nSize);
	}

};

// Snowfall.java