/*  earth.c  texture globe  needs   readtex.c   and   earth_sm.rgb  
 *  A little bit different "Hello, World!" program ;-)
 *  Author: Norman Walter
 *  e-mail: walternn@studi.informatik.uni-stuttgart.de
 *  www: http://www.norman-interactive.com
 *  Date: 22.3.2002, changes by JSS 7/14/2004
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <GL/glut.h>

#define ANIMATE 10
#define POINT_FILTER 20
#define LINEAR_FILTER 21
#define SLOWER 30         /* added to menu JSS */
#define FASTER 31
#define QUIT 100

static GLuint Globe;
static GLboolean Animate = GL_TRUE;
static GLfloat Xrot = -66.55, Yrot = -23.45, Zrot = 0.0;
static GLfloat DZrot = 0.1; /* JSS added GLfloat, 1.0 -> 0.1 */
static int winWidth = 200;
static int winHeight = 200;

static void drawText(GLfloat x, GLfloat y, char * msg)
{
  int   i, len;

  glPushMatrix();
    glLoadIdentity();
    glTranslatef( 0.0, 0.0, -10.0 ); /* -10 from 10 in frustum */
    glColor3f(1.0f, 1.0f, 0.0f);
    glRasterPos2f(x, y); /* relative to -1.0 1.0 in frustum */
    len = strlen(msg);
    for (i=0; i<len; i++)
      glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, msg[i]);
  glPopMatrix();
}

static void Idle( void )
{
  if(Animate)
  {
    Zrot += DZrot;
    if(Zrot > 360.0)
    {
      Zrot -= 360.0;
    }
    glutPostRedisplay();
  }
}

static void Display( void )
{
  glClearColor(1.0, 1.0, 1.0, 1.0);
  glClear( GL_COLOR_BUFFER_BIT |
           GL_DEPTH_BUFFER_BIT | GL_ACCUM_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );

  glPushMatrix();
    glRotatef(Xrot, 1.0, 0.0, 0.0);
    glRotatef(Yrot, 0.0, 1.0, 0.0);
    glRotatef(Zrot, 0.0, 0.0, 1.0);
    glScalef(5.0, 5.0, 5.0);
    glCallList(Globe);
  glPopMatrix();

  drawText(-0.9, -0.9, "right click for menu");
  glFlush();
  glutSwapBuffers();
} /* end display */


static void Reshape( int width, int height )
{
  winWidth = width;
  winHeight = height;
  glViewport( 0, 0, width, height );
  glMatrixMode( GL_PROJECTION );
  glLoadIdentity();
  glFrustum( -1.0, 1.0, -1.0, 1.0, 10.0, 100.0 );
  glMatrixMode( GL_MODELVIEW );
  glLoadIdentity();
  glTranslatef( 0.0, 0.0, -70.0 );
} /* end reshape */


static void ModeMenu( int entry )
{
  if(entry==ANIMATE)
  {
    Animate = !Animate;
  }
  else if(entry==POINT_FILTER) {
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  }
  else if(entry==LINEAR_FILTER) {
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  }
  else if(entry==SLOWER)
  {
    DZrot /= 2.0;
  }
  else if(entry==FASTER)
  {
    DZrot *= 2.0;
  }
  else if(entry==QUIT) {
    exit(0);
  }
  glutPostRedisplay();
} /* end ModeMenu */

static void Key(unsigned char key, int x, int y )
{
  switch (key)
  {
    case 'x':
      Xrot -= 5.0;
      break;
    case 'X':
      Xrot += 5.0;
      break;
    case 'y':
      Yrot -= 5.0;
      break;
    case 'Y':
      Yrot += 5.0;
      break;
    case 27:
      exit(0);
      break;
  }
  glutPostRedisplay();
}

static void Init( void )
{
  GLUquadricObj *q = gluNewQuadric();

  /* set clear color to white */
  glClearColor (1.0, 1.0, 1.0, 1.0);
  glClear( GL_COLOR_BUFFER_BIT |
           GL_DEPTH_BUFFER_BIT | GL_ACCUM_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );

  Globe = glGenLists(1);

  glNewList(Globe, GL_COMPILE);
    /* globe */
    gluQuadricNormals(q, GL_SMOOTH);
    gluQuadricTexture(q, GL_TRUE);
    gluSphere (q, 1.0, 15, 15);
  glEndList();

  gluDeleteQuadric(q);

  /* fitering = nearest, initially */
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
  glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST);

  glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
  glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);

  if(!LoadRGBMipmaps("earth_small.rgb", GL_RGB))
  {
    printf("Error: couldn't load texture image\n");
    exit(1);
  }

   glEnable(GL_CULL_FACE);
   glEnable(GL_TEXTURE_2D);
} /* end init */

int main(int argc, char *argv[])
{
  glutInit( &argc, argv );
  glutInitWindowSize( winWidth, winHeight );
  glutInitWindowPosition(100,100); 
  glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
  glutCreateWindow(argv[0]);
  Init();
  glutReshapeFunc( Reshape );
  glutKeyboardFunc( Key );
  glutDisplayFunc( Display );
  glutIdleFunc( Idle );
  glutCreateMenu(ModeMenu);
    glutAddMenuEntry("Point Filtered", POINT_FILTER);
    glutAddMenuEntry("Linear Filtered", LINEAR_FILTER);
    glutAddMenuEntry("Toggle Animation", ANIMATE);
    glutAddMenuEntry("Rotate slower", SLOWER);
    glutAddMenuEntry("Rotate faster", FASTER);
    glutAddMenuEntry("Quit", QUIT);
    glutAttachMenu(GLUT_RIGHT_BUTTON);

   glutMainLoop();
   return 0;
} /* end main of earth.c */