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

#define WINDSIZEX 100
#define WINDSIZEY 100

#define X1       1.25
#define X2       9.5

#define Y1       1.25
#define Y2      10.75

void init(void)
{
   GLfloat red[]   = {1.0, 0.0, 0.0, 1.0};

   glClearColor(0.0, 0.0, 0.0, 1.0);
   glColor4fv(red);
}

void Render()
{
   glClear(GL_COLOR_BUFFER_BIT);

   glBegin(GL_TRIANGLES);
   glVertex2f (X1, Y2);
   glVertex2f (X1, Y1);
   glVertex2f (X2, Y1);
   glEnd();

   glFlush();
}

void test(void)
{    
   //state1
   //glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 0);
   glEnable(GL_LIGHTING);
   //glFrontFace (GL_CCW);

   Render();

   //state2
   glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 1);
   glDisable(GL_LIGHTING);
   glFrontFace (GL_CW);

   Render();
}

void display(void)
{
   glViewport(0, 0, WINDSIZEX, WINDSIZEY);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluOrtho2D(0, WINDSIZEX, 0, WINDSIZEY);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   test();
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize(WINDSIZEX, WINDSIZEY);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutDisplayFunc(display);
   glutMainLoop();
   return 0; 
}