/*
 *  pickdepth.java
 *  Picking is demonstrated in this program.  In 
 *  rendering mode, three overlapping rectangles are 
 *  drawn.  When the left mouse button is pressed, 
 *  selection mode is entered with the picking matrix.  
 *  Rectangles which are drawn under the cursor position
 *  are "picked."  Pay special attention to the depth 
 *  value range, which is returned.
 */
import java.lang.System;

import jgl.GL;
import jgl.GLUT;
import jgl.GLApplet;

public class pickdepth extends GLApplet {

    private void myinit () {
	myGL.glClearColor (0.0f, 0.0f, 0.0f, 0.0f); 
	myGL.glDepthFunc (GL.GL_LESS);
	myGL.glEnable (GL.GL_DEPTH_TEST);
	myGL.glShadeModel (GL.GL_FLAT);
	myGL.glDepthRange (0.0f, 1.0f); /* The default z mapping */
    }

    /*
     *  The three rectangles are drawn.  In selection mode, 
     *  each rectangle is given the same name.  Note that 
     *  each rectangle is drawn with a different z value.
     */
    private void drawRects (int mode) {
	if (mode == GL.GL_SELECT) 
	    myGL.glLoadName (1);
	myGL.glBegin (GL.GL_QUADS);
	    myGL.glColor3f (1.0f, 1.0f, 0.0f);
	    myGL.glVertex3i (2, 0, 0);
	    myGL.glVertex3i (2, 6, 0);
	    myGL.glVertex3i (6, 6, 0);
	    myGL.glVertex3i (6, 0, 0);
	myGL.glEnd ();
	if (mode == GL.GL_SELECT) 
	    myGL.glLoadName (2);
	myGL.glBegin (GL.GL_QUADS);
	    myGL.glColor3f (0.0f, 1.0f, 1.0f);
	    myGL.glVertex3i (3, 2, -1);
	    myGL.glVertex3i (3, 8, -1);
	    myGL.glVertex3i (8, 8, -1);
	    myGL.glVertex3i (8, 2, -1);
	myGL.glEnd ();
	if (mode == GL.GL_SELECT) 
	    myGL.glLoadName (3);
	myGL.glBegin (GL.GL_QUADS);
	    myGL.glColor3f (1.0f, 0.0f, 1.0f);
	    myGL.glVertex3i (0, 2, -2);
	    myGL.glVertex3i (0, 7, -2);
	    myGL.glVertex3i (5, 7, -2);
	    myGL.glVertex3i (5, 2, -2);
	myGL.glEnd ();
    }

    /*
     *  processHits() prints out the contents of the 
     *  selection array.
     */
    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 ();
	}
    }

    /* 
     *  pickRects() sets up selection mode, name stack, 
     *  and projection matrix for picking.  Then the objects 
     *  are drawn.
     */
    private static final int BUFSIZE = 512;

    public void pickRects (int button, int state, int x, int y) {
	int selectBuf [] = new int [BUFSIZE];
	int hits;
	int viewport [] = new int [4];

	if (button != GLUT.GLUT_LEFT_BUTTON || state != GLUT.GLUT_DOWN)
	    return;

	myGL.glGetIntegerv (GL.GL_VIEWPORT, viewport);

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

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

	myGL.glMatrixMode (GL.GL_PROJECTION);
	myGL.glPushMatrix ();
	myGL.glLoadIdentity ();
	/*  create 5x5 pixel picking region near cursor location        */
	myGLU.gluPickMatrix((double)x,(double)(viewport[3]-y),5.0,5.0,viewport);
	myGL.glOrtho (0.0f, 8.0f, 0.0f, 8.0f, -0.5f, 2.5f);
	drawRects (GL.GL_SELECT);
	myGL.glPopMatrix ();
	myGL.glFlush ();

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

    public void display () {
	myGL.glClear (GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
	drawRects (GL.GL_RENDER);
	myGL.glFlush ();
    }

    public void myReshape (int w, int h) {
        myGL.glViewport (0, 0, w, h);
        myGL.glMatrixMode (GL.GL_PROJECTION);
        myGL.glLoadIdentity ();
	myGL.glOrtho (0.0f, 8.0f, 0.0f, 8.0f, -0.5f, 2.5f);
        myGL.glMatrixMode (GL.GL_MODELVIEW);
        myGL.glLoadIdentity ();
    }

    /*
     *  Main Loop
     *  Open window with initial window size, title bar, 
     *  RGBA display mode, depth buffer, and handle input events.
     */
    public void init () {
	myUT.glutInitWindowSize (100, 100);
	myUT.glutInitWindowPosition (0, 0);
	myUT.glutCreateWindow (this);
	myinit ();
	myUT.glutMouseFunc ("pickRects");
	myUT.glutReshapeFunc ("myReshape");
	myUT.glutDisplayFunc ("display");
	myUT.glutMainLoop ();
    }

}