import java.applet.Applet;
import java.awt.Graphics;
import java.lang.System;

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

public class select extends Applet {
    // must use GL to use jGL.....
    // and use GLU to use the glu functions....
    // remember to give GL to initialize GLU
    // and use GLAUX to use the aux functions.....
    // remember to give GL to initialize GLAUX
    GL myGL = new GL ();
    GLU myGLU = new GLU (myGL);
    GLAUX myAUX = new GLAUX (myGL);

    private void drawTriangle (float x1, float y1, float x2, float y2, float x3, float y3, float z) {
	myGL.glBegin (GL.GL_TRIANGLES);
	myGL.glVertex3f (x1, y1, z);
	myGL.glVertex3f (x2, y2, z);
	myGL.glVertex3f (x3, y3, z);
	myGL.glEnd ();
    }

    private void drawViewVolume (float x1, float x2, float y1, float y2, float z1, float z2) {
	myGL.glColor3f (1.0f, 1.0f, 1.0f);
	myGL.glBegin (GL.GL_LINE_LOOP);
	    myGL.glVertex3f (x1, y1, -z1);
	    myGL.glVertex3f (x2, y1, -z1);
	    myGL.glVertex3f (x2, y2, -z1);
	    myGL.glVertex3f (x1, y2, -z1);
	myGL.glEnd ();

	myGL.glBegin (GL.GL_LINE_LOOP);
	    myGL.glVertex3f (x1, y1, -z2);
	    myGL.glVertex3f (x2, y1, -z2);
	    myGL.glVertex3f (x2, y2, -z2);
	    myGL.glVertex3f (x1, y2, -z2);
	myGL.glEnd ();

	myGL.glBegin (GL.GL_LINES); /*  4 lines     */
	    myGL.glVertex3f (x1, y1, -z1);
	    myGL.glVertex3f (x1, y1, -z2);
	    myGL.glVertex3f (x1, y2, -z1);
	    myGL.glVertex3f (x1, y2, -z2);
	    myGL.glVertex3f (x2, y1, -z1);
	    myGL.glVertex3f (x2, y1, -z2);
	    myGL.glVertex3f (x2, y2, -z1);
	    myGL.glVertex3f (x2, y2, -z2);
	myGL.glEnd ();
    }

    private void drawScene () {
	myGL.glMatrixMode (GL.GL_PROJECTION);
	myGL.glLoadIdentity ();
	myGLU.gluPerspective (40.0, 4.0/3.0, 0.01, 100.0);

	myGL.glMatrixMode (GL.GL_MODELVIEW);
	myGL.glLoadIdentity ();
	myGLU.gluLookAt (7.5f, 7.5f, 12.5f, 2.5f, 2.5f, -5.0f, 0.0f, 1.0f, 0.0f);
	myGL.glColor3f (0.0f, 1.0f, 0.0f);  /*  green triangle      */
	drawTriangle (2.0f, 2.0f, 3.0f, 2.0f, 2.5f, 3.0f, -5.0f);
	myGL.glColor3f (1.0f, 0.0f, 0.0f);  /*  red triangle        */
	drawTriangle (2.0f, 7.0f, 3.0f, 7.0f, 2.5f, 8.0f, -5.0f);
	myGL.glColor3f (1.0f, 1.0f, 0.0f);  /*  yellow triangles    */
	drawTriangle (2.0f, 2.0f, 3.0f, 2.0f, 2.5f, 3.0f, 0.0f);
	drawTriangle (2.0f, 2.0f, 3.0f, 2.0f, 2.5f, 3.0f, -10.0f);
	drawViewVolume (0.0f, 5.0f, 0.0f, 5.0f, 0.0f, 10.0f);
    }

    private void processHits (int hits, int buffer []) {
	int i, j;
	int names, ptr;

	System.out.println ("hits = " + hits);
	ptr = 0;
	for (i = 0; i < hits; i++) {        /*  for each hit  */
	    names = buffer [ptr];
	    System.out.println (" number of names for hit = " + names); ptr++;
	    System.out.print ("  z1 is " + buffer [ptr] + ";"); ptr++;
	    System.out.println (" z2 is " + buffer [ptr]); ptr++;
	    System.out.print ("   the name is ");
	    for (j = 0; j < names; j++) {   /*  for each name */
		System.out.print (buffer [ptr] + " "); ptr++;
	    }
	    System.out.println ();
	}
    }

    private static final int BUFSIZE = 512;

    private void selectObjects () {
	int selectBuf [] = new int [BUFSIZE];
	int hits;
	int viewport [] = new int [4];

	myGL.glSelectBuffer (BUFSIZE, selectBuf);
	myGL.glRenderMode (GL.GL_SELECT);

	myGL.glInitNames ();
	myGL.glPushName (-1);

	myGL.glPushMatrix ();
	myGL.glMatrixMode (GL.GL_PROJECTION);
	myGL.glLoadIdentity ();
	myGL.glOrtho (0.0f, 5.0f, 0.0f, 5.0f, 0.0f, 10.0f);
	myGL.glMatrixMode (GL.GL_MODELVIEW);
	myGL.glLoadIdentity ();
	myGL.glLoadName (1);
	drawTriangle (2.0f, 2.0f, 3.0f, 2.0f, 2.5f, 3.0f, -5.0f);
	myGL.glLoadName (2);
	drawTriangle (2.0f, 7.0f, 3.0f, 7.0f, 2.5f, 8.0f, -5.0f);
	myGL.glLoadName (3);
	drawTriangle (2.0f, 2.0f, 3.0f, 2.0f, 2.5f, 3.0f, 0.0f);
	drawTriangle (2.0f, 2.0f, 3.0f, 2.0f, 2.5f, 3.0f, -10.0f);
	myGL.glPopMatrix ();
	myGL.glFlush ();

	hits = myGL.glRenderMode (GL.GL_RENDER);
	processHits (hits, selectBuf);
    }

    private void myinit () {
	myGL.glDepthFunc (GL.GL_LEQUAL);
	myGL.glEnable (GL.GL_DEPTH_TEST);
	myGL.glShadeModel (GL.GL_FLAT);
    }

    private void display () {
    	myGL.glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
	myGL.glClear (GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
	drawScene ();
	selectObjects ();
	myGL.glFlush ();
    }

    public void update (Graphics g) {
	// skip the clear screen command....
	paint (g);
    }

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

    public void init () {
	myAUX.auxInitPosition (0, 0, 200, 200);
	myAUX.auxInitWindow (this);
	myinit ();

	// call display as call auxIdleFunc(display)
        display ();
    }

}