/*
 *  texsub.java
 *  This program texture maps a checkerboard image onto
 *  two rectangles.  This program clamps the texture, if
 *  the texture coordinates fall outside 0.0 and 1.0.
 *  If the s key is pressed, a texture subimage is used to
 *  alter the original texture.  If the r key is pressed, 
 *  the original texture is restored.
 */

import java.awt.Frame;
import java.io.IOException;
import java.lang.String;
import java.lang.System;

import jgl.GL;
import jgl.GLCanvas;

public class texsub extends GLCanvas {

    /* Create checkerboard texture */
    private static final int checkImageWidth = 64;
    private static final int checkImageHeight = 64;
    private static final int subImageWidth = 16;
    private static final int subImageHeight = 16;
    private byte checkImage [][][] =
    		   new byte [checkImageWidth][checkImageHeight][4];
    private byte subImage [][][] =
    		   new byte [subImageWidth][subImageHeight][4];

    private int texName [] = new int [1];

    private void makeCheckImage () {
    	int i, j, c;

	for (i = 0; i < checkImageWidth; i++) {
	    for (j = 0; j < checkImageHeight; j++) {
	    	if ((((i & 0x8) == 0) ^ ((j & 0x8)) == 0)) c = 255; else  c = 0;
		checkImage [i][j][0] = (byte) c;
		checkImage [i][j][1] = (byte) c;
		checkImage [i][j][2] = (byte) c;
		checkImage [i][j][3] = (byte) 255;
	    }
	}

	for (i = 0; i < subImageWidth; i++) {
	    for (j = 0; j < subImageHeight; j++) {
	    	if ((((i & 0x4) == 0) ^ ((j & 0x4)) == 0)) c = 255; else  c = 0;
		subImage [i][j][0] = (byte) c;
		subImage [i][j][1] = (byte) 0;
		subImage [i][j][2] = (byte) 0;
		subImage [i][j][3] = (byte) 255;
	    }
	}
    }

    private void myinit () {
	myGL.glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
	myGL.glShadeModel (GL.GL_FLAT);
	myGL.glEnable (GL.GL_DEPTH_TEST);

	makeCheckImage ();
	myGL.glPixelStorei (GL.GL_UNPACK_ALIGNMENT, 1);

	myGL.glGenTextures (1, texName);
	myGL.glBindTexture (GL.GL_TEXTURE_2D, texName [0]);

	myGL.glTexParameterf (GL.GL_TEXTURE_2D, GL.GL_TEXTURE_WRAP_S, GL.GL_REPEAT);
	myGL.glTexParameterf (GL.GL_TEXTURE_2D, GL.GL_TEXTURE_WRAP_T, GL.GL_REPEAT);
	myGL.glTexParameterf (GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER, GL.GL_NEAREST);
	myGL.glTexParameterf (GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER, GL.GL_NEAREST);
	myGL.glTexImage2D (GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, checkImageWidth,
	    checkImageHeight, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, checkImage);
    }

    public void display () {
	myGL.glClear (GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
	myGL.glEnable (GL.GL_TEXTURE_2D);
	myGL.glTexEnvf (GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE, GL.GL_DECAL);
	myGL.glBindTexture (GL.GL_TEXTURE_2D, texName [0]);
	myGL.glBegin (GL.GL_QUADS);
	myGL.glTexCoord2f (0.0f, 0.0f); myGL.glVertex3f (-2.0f, -1.0f, 0.0f);
	myGL.glTexCoord2f (0.0f, 1.0f); myGL.glVertex3f (-2.0f, 1.0f, 0.0f);
	myGL.glTexCoord2f (1.0f, 1.0f); myGL.glVertex3f (0.0f, 1.0f, 0.0f);
	myGL.glTexCoord2f (1.0f, 0.0f); myGL.glVertex3f (0.0f, -1.0f, 0.0f);

	myGL.glTexCoord2f (0.0f, 0.0f); myGL.glVertex3f (1.0f, -1.0f, 0.0f);
	myGL.glTexCoord2f (0.0f, 1.0f); myGL.glVertex3f (1.0f, 1.0f, 0.0f);
	myGL.glTexCoord2f (1.0f, 1.0f); myGL.glVertex3f (2.41421f, 1.0f, -1.41421f);
	myGL.glTexCoord2f (1.0f, 0.0f); myGL.glVertex3f (2.41421f, -1.0f, -1.41421f);
	myGL.glEnd ();
	myGL.glFlush ();
	myGL.glDisable (GL.GL_TEXTURE_2D);
    }

    public void myReshape (int w, int h) {
        myGL.glViewport (0, 0, w, h);
        myGL.glMatrixMode (GL.GL_PROJECTION);
        myGL.glLoadIdentity ();
	myGLU.gluPerspective (60.0, 1.0 * (double)w/(double)h, 1.0, 30.0);
        myGL.glMatrixMode (GL.GL_MODELVIEW);
        myGL.glLoadIdentity ();
	myGL.glTranslatef (0.0f, 0.0f, -3.6f);
    }

    public void keyboard (char key, int x, int y) {
	switch (key) {
	    case 's':
	    case 'S':
		myGL.glBindTexture (GL.GL_TEXTURE_2D, texName [0]);
		myGL.glTexSubImage2D (GL.GL_TEXTURE_2D, 0, 12, 44,
				      subImageWidth, subImageHeight, GL.GL_RGBA,
				      GL.GL_UNSIGNED_BYTE, subImage);
		myUT.glutPostRedisplay ();
		break;
	    case 'r':
	    case 'R':
		myGL.glBindTexture (GL.GL_TEXTURE_2D, texName [0]);
		myGL.glTexImage2D (GL.GL_TEXTURE_2D, 0, GL.GL_RGBA,
				   checkImageWidth, checkImageHeight, 0, GL.GL_RGBA,
				   GL.GL_UNSIGNED_BYTE, checkImage);
		myUT.glutPostRedisplay ();
		break;
	    case 27:
		System.exit(0);
	    default:
		break;
	}
    }

    public void init () {
	myUT.glutInitWindowSize (500, 500);
	myUT.glutInitWindowPosition (0, 0);
	myUT.glutCreateWindow (this);
	myinit ();
	myUT.glutReshapeFunc ("myReshape");
	myUT.glutDisplayFunc ("display");
	myUT.glutKeyboardFunc ("keyboard");
	myUT.glutMainLoop ();
    }

    static public void main (String args[]) throws IOException {
	Frame mainFrame = new Frame ();
	mainFrame.setSize (508, 527);
	texsub mainCanvas = new texsub ();
	mainCanvas.init();
	mainFrame.add (mainCanvas);
	mainFrame.setVisible (true);
    }

}