import java.awt.*;

class Drawing extends Canvas implements Runnable
{
    private Image    saved = null;
    private Graphics gSaved, gWindow;
    private int      width, height;
    private Thread   computation = null;
    private volatile boolean stop   = false;
    private double   x1, x2, y1, y2;
    private int      nbIterations;

    public void init()
    {
	Dimension d = getSize();

	width = d.width;
	height = d.height;

	saved  = createImage(width, height);
	gSaved = saved.getGraphics();
	gWindow = this.getGraphics();
	this.delete();
    }

    public void paint(Graphics g)
    {
	g.drawImage(saved, 0, 0, this);
    }

    public Dimension getMinimumSize()
    {
	return new Dimension(1200, 900);
    }

    public Dimension getPreferredSize()
    {
	return getMinimumSize();
    }

    public synchronized void compute(double x1, double y1,
				     double x2, double y2, int nb)
    {
	this.interrupt();
	this.delete();

	this.x1 = x1;
	this.y1 = y1;
	this.x2 = x2;
	this.y2 = y2;
	this.nbIterations = nb;

	computation = new Thread(this, "computation of the fractal");
	computation.start();
    }

    public synchronized void interrupt()
    {
	stop = true;
	while (computation != null)
	    {
		try
		    {
			wait();
		    }
		catch(InterruptedException e) { }
	    }
	stop = false;
    }

    public void run()
    {
	Mandelbrot  m = new Mandelbrot(nbIterations);
	double      dx = (x2 - x1) / width;
	double      dy = (y2 - y1) / height;

	main:
	for (int i = 0; i < width; i++)
	    for (int j = 0; j < height; j++)
		if (stop)
		    break main;
		else
		    {
			Color c = m.color(x1 + i * dx,
					  y1 + j * dy);
			gWindow.setColor(c);
			gWindow.drawLine(i, j, i, j);
			gSaved.setColor(c);
			gSaved.drawLine(i, j, i, j);
		    }

	synchronized(this)
	    {
		computation = null;
		notify();
	    }
    }

    public int width()
    {
	return width;
    }

    public int height()
    {
	return height;
    }

    private void delete()
    {
	gSaved.setColor(Color.black);
	gSaved.fillRect(0, 0, width, height);
	gWindow.setColor(Color.black);
	gWindow.fillRect(0, 0, width, height);
    }
}