text: /*
   * Copyright (c) 1993-1997, Silicon Graphics, Inc.
   * ALL RIGHTS RESERVED 
   * Permission to use, copy, modify, and distribute this software for 
   * any purpose and without fee is hereby granted, provided that the above
   * copyright notice appear in all copies and that both the copyright notice
   * and this permission notice appear in supporting documentation, and that 
   * the name of Silicon Graphics, Inc. not be used in advertising
   * or publicity pertaining to distribution of the software without specific,
   * written prior permission. 
   *
   * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
   * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
   * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
   * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
   * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
   * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
   * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
   * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
   * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
   * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
   * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
   * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
   * 
   * US Government Users Restricted Rights 
   * Use, duplication, or disclosure by the Government is subject to
   * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
   * (c)(1)(ii) of the Rights in Technical Data and Computer Software
   * clause at DFARS 252.227-7013 and/or in similar or successor
   * clauses in the FAR or the DOD or NASA FAR Supplement.
   * Unpublished-- rights reserved under the copyright laws of the
   * United States.  Contractor/manufacturer is Silicon Graphics,
   * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
   *
   * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
   */
  
  /*
   *  aaindex.c
   *  This program draws shows how to draw anti-aliased lines in color
   *  index mode. It draws two diagonal lines to form an X; when 'r' 
   *  is typed in the window, the lines are rotated in opposite 
   *  directions.
   */
  #include <GL/glut.h>
  #include "stdlib.h"
  
  #define RAMPSIZE 16
  #define RAMP1START 32
  #define RAMP2START 48
  
  static float rotAngle = 0.;
  
  /*  Initialize antialiasing for color index mode,
   *  including loading a green color ramp starting
   *  at RAMP1START, and a blue color ramp starting
   *  at RAMP2START. The ramps must be a multiple of 16.
   */
  void init(void)
  {
     int i;
  
     for (i = 0; i < RAMPSIZE; i++) {
        GLfloat shade;
        shade = (GLfloat) i/(GLfloat) RAMPSIZE;
        glutSetColor(RAMP1START+(GLint)i, 0., shade, 0.);
        glutSetColor(RAMP2START+(GLint)i, 0., 0., shade);
     }
  
     glEnable (GL_LINE_SMOOTH);
     glHint (GL_LINE_SMOOTH_HINT, GL_DONT_CARE);
     glLineWidth (1.5);
  
     glClearIndex ((GLfloat) RAMP1START);
  }
  
  /*  Draw 2 diagonal lines to form an X
   */
  void display(void)
  {
     glClear(GL_COLOR_BUFFER_BIT);
  
     glIndexi(RAMP1START);
     glPushMatrix();
     glRotatef(-rotAngle, 0.0, 0.0, 0.1);
     glBegin (GL_LINES);
        glVertex2f (-0.5, 0.5);
        glVertex2f (0.5, -0.5);
     glEnd ();
     glPopMatrix();
  
     glIndexi(RAMP2START);
     glPushMatrix();
     glRotatef(rotAngle, 0.0, 0.0, 0.1);
     glBegin (GL_LINES);
        glVertex2f (0.5, 0.5);
        glVertex2f (-0.5, -0.5);
     glEnd ();
     glPopMatrix();
  
     glFlush();
  }
  
  void reshape(int w, int h)
  {
     glViewport(0, 0, (GLsizei) w, (GLsizei) h);
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     if (w <= h) 
        gluOrtho2D (-1.0, 1.0, 
           -1.0*(GLfloat)h/(GLfloat)w, 1.0*(GLfloat)h/(GLfloat)w);
     else 
        gluOrtho2D (-1.0*(GLfloat)w/(GLfloat)h, 
           1.0*(GLfloat)w/(GLfloat)h, -1.0, 1.0);
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
  }
  
  void keyboard(unsigned char key, int x, int y)
  {
     switch (key) {
        case 'r':
        case 'R':
           rotAngle += 20.;
           if (rotAngle >= 360.) rotAngle = 0.;
           glutPostRedisplay();	
           break;
        case 27:  /*  Escape Key */
           exit(0);
           break;
        default:
           break;
      }
  }
  
  /*  Main Loop
   *  Open window with initial window size, title bar, 
   *  color index display mode, and handle input events.
   */
  int main(int argc, char** argv)
  {
     glutInit(&argc, argv);
     glutInitDisplayMode (GLUT_SINGLE | GLUT_INDEX);
     glutInitWindowSize (200, 200);
     glutCreateWindow (argv[0]);
     init();
     glutReshapeFunc (reshape);
     glutKeyboardFunc (keyboard);
     glutDisplayFunc (display);
     glutMainLoop();
     return 0;
  }
  