import java.applet.Applet;
import java.awt.Graphics;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.awt.event.InputEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.lang.InterruptedException;
import java.lang.Runnable;
import java.lang.Thread;

// must import jgl.GL....
import jgl.GL;
import jgl.GLAUX;

// "double" is a reserved word in Java
public class doublebuffer extends Applet 
			  implements ComponentListener,
				     MouseListener,
				     Runnable {
    // must use GL to use jGL.....
    // and use GLAUX to use the aux functions.....
    // remember to give GL to initialize GLAUX
    GL myGL = new GL ();
    GLAUX myAUX = new GLAUX (myGL);

    private Thread kicker;

    private float spin = 0;

    private void display () {
	myGL.glClear (GL.GL_COLOR_BUFFER_BIT);

	myGL.glPushMatrix ();
	myGL.glRotatef (spin, 0.0f, 0.0f, 1.0f);
	myGL.glRectf (-25.0f, -25.0f, 25.0f, 25.0f);
	myGL.glPopMatrix ();

	myGL.glFlush ();
    }

    private void spinDisplay () {
    	spin += 2.0f;
	if (spin >= 360.0f) {
	    spin -= 360.0f;
	}
	display ();
    }

    public void mouseClicked(MouseEvent e) {}
    public void mouseEntered(MouseEvent e) {}
    public void mouseExited(MouseEvent e) {}
    public void mouseReleased(MouseEvent e) {}

    public void mousePressed(MouseEvent e) {
    	// process which button by myself
    	if ((e.getModifiers() & InputEvent.BUTTON1_MASK)
	    == InputEvent.BUTTON1_MASK) { // left
	    start ();
	} else if ((e.getModifiers() & InputEvent.BUTTON2_MASK)
		   == InputEvent.BUTTON2_MASK) { // middle
	    stop ();
	}
	e.consume ();
    }

    private void myinit () {
	myGL.glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
	myGL.glColor3f (1.0f, 1.0f, 1.0f);
	myGL.glShadeModel (GL.GL_FLAT);
    }

    public void componentMoved (ComponentEvent e) {}
    public void componentShown (ComponentEvent e) {}
    public void componentHidden (ComponentEvent e) {}

    public void componentResized (ComponentEvent e) {
    	// get window width and height by myself
	myReshape (getSize ().width, getSize ().height);
	display ();
	repaint ();
    }

    private void myReshape (int w, int h) {
    	myGL.glViewport (0, 0, w, h);
	myGL.glMatrixMode (GL.GL_PROJECTION);
	myGL.glLoadIdentity ();
	if (w <= h) {
	    myGL.glOrtho (-50.0f, 50.0f,
	    		  -50.0f*(float)h/(float)w, 
			   50.0f*(float)h/(float)w, 
			   -1.0f,  1.0f);
	} else {
	    myGL.glOrtho (-50.0f*(float)w/(float)h, 
			   50.0f*(float)w/(float)h, 
	    		  -50.0f, 50.0f,
			   -1.0f,  1.0f);
	}
	myGL.glMatrixMode (GL.GL_MODELVIEW);
	myGL.glLoadIdentity ();
    }
	
     public void update (Graphics g) {
    	// skip the clear screen command....
 	paint (g);
     }

    public void paint (Graphics g) {
	myGL.glXSwapBuffers (g, this);
	pause ();
    }

    public void init () {
	myAUX.auxInitPosition (0, 0, 500, 500);
	myAUX.auxInitWindow (this);
	myinit ();
	
	// as call auxReshapeFunc()
	addComponentListener (this);
	myReshape (getSize ().width, getSize ().height);

	// as call auxMouseFunc()
	addMouseListener(this);

	// call spinDisplay before paint
	spinDisplay ();
    }

    public void run () {
	// call spinDisplay as call auxIdleFunc(spinDisplay)
	spinDisplay ();
	repaint ();
    }

    public void destroy () {
	removeComponentListener (this);
	removeMouseListener (this);
    }

    public synchronized void start () {
	if (kicker == null || !kicker.isAlive()) {
	    kicker = new Thread (this);
	    kicker.start ();
	}
    }

    public synchronized void stop () {
	kicker = null;
    }

    public void pause () {
	if (kicker != null) { spinDisplay (); }
	try { Thread.sleep (20); } catch (InterruptedException e) {}
    }

}