#include <GL/glut.h>
#include <stdlib.h>

#define MUNDO 4.0f

void inicializar (void);
void redimensiona (int alto, int ancho);
void dibuja (void);
void teclado (unsigned char key, int cx, int cy);
void tecladoEspecial (int key, int cy, int cx);
void animacion (void);
void raton (int boton, int estado, int cx, int cy);

int main(int argc, char** argv) {
   
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (640, 480);
   glutInitWindowPosition (100, 105);
   glutCreateWindow (argv[0]);
   inicializar();
   
   glutDisplayFunc(dibuja);
   glutReshapeFunc(redimensiona);
   glutKeyboardFunc(teclado);
   glutSpecialFunc(tecladoEspecial);
   glutMouseFunc(raton);
   glutIdleFunc(animacion);
   glutMainLoop();
   
   return 0;
}

void inicializar () {
   glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
   glEnable(GL_DEPTH_TEST);
}

void redimensiona (int ancho, int alto) {
   float aspect;
   
   glViewport (0, 0, ancho, alto);
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   
   if (alto == 0){
   	  alto = 1;
   }
   
   aspect = (float) ancho / (float) alto;
   
   if (ancho <= alto) {
   	  glOrtho(-MUNDO, MUNDO, -MUNDO/aspect, MUNDO/aspect, -MUNDO, MUNDO);
   } else {
   	  glOrtho(-MUNDO * aspect, MUNDO * aspect, -MUNDO, MUNDO, -MUNDO, MUNDO);
   }
   
   /*
      gluPerspective(45, aspect, -MUNDO, MUNDO); 
   */
   
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

void teclado (unsigned char key, int cx, int cy) {
	
	switch (key) {
		case 27:
		   exit(0);
		break;
		
		default: break;
	}
	
	glutPostRedisplay();
}

void tecladoEspecial (int key, int cy, int cx) {
	
	switch (key) {
		case GLUT_KEY_UP:
		break;
		
		case GLUT_KEY_DOWN:
		break;
		
		case GLUT_KEY_LEFT:
		break;
		
		case GLUT_KEY_RIGHT:
		break;
		
		case GLUT_KEY_HOME:
		break;
		
		default: break;
	}
	
	glutPostRedisplay();
}

void raton (int boton, int estado, int cx, int cy) {
 
    if (boton == GLUT_LEFT_BUTTON && estado == GLUT_DOWN) { 
    }
    else if (boton == GLUT_RIGHT_BUTTON && estado == GLUT_UP) {
    }
    
    glutPostRedisplay();
}

void animacion (void) {
	glutPostRedisplay();
}	

void dibuja (void) {
	
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	
	/*
	  dibuja aqui !!
	 */
	    
	glutSwapBuffers();
}