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

#define WINDSIZEX 100
#define WINDSIZEY 100


void init(void)
{
   int i, j;
   GLint texID;
   GLfloat   texImage[2][2][4];

   for (i = 0; i < 2; i++)
   {
      for (j = 0; j < 2; j++)
      {
          if (i == 0)
          {
            texImage[i][j][0] = 1.0;
            texImage[i][j][1] = 0.0;
            texImage[i][j][2] = 0.0;
            texImage[i][j][3] = 0.0;
           }
           else
           {
            texImage[i][j][0] = 0.0;
            texImage[i][j][1] = 0.0;
            texImage[i][j][2] = 1.0;
            texImage[i][j][3] = 0.0;
           }
      }
   }

   glEnable(GL_TEXTURE_2D);

   glGenTextures(1, &texID);

   glBindTexture(GL_TEXTURE_2D, texID);

   glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_FLOAT,
         texImage);

   glTexEnvf(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE);
 
   glEnable(GL_POINT_SPRITE);

   GLfloat maxSize;
   glGetFloatv(GL_POINT_SIZE_MAX, &maxSize);
   printf ("max point size: %f\n", maxSize);
}

#define TEX_WIDTH 2
static void test(void)
{    
   GLfloat buf[(TEX_WIDTH+2)*(TEX_WIDTH+2)*3];
   int i, j;

   glClear(GL_COLOR_BUFFER_BIT);

   glPointSize(TEX_WIDTH);
   glPolygonMode (GL_FRONT_AND_BACK, GL_POINT);
   glBegin(GL_TRIANGLES);
      glVertex2f(TEX_WIDTH/2+1, TEX_WIDTH/2+1);
      glVertex2f(20, 8);
      glVertex2f(40, 80);
   glEnd();


   glReadPixels(0, 0, TEX_WIDTH+2, TEX_WIDTH+2, GL_RGB, GL_FLOAT, buf);
   for (i=0; i<TEX_WIDTH+2; i++)
   {
      printf ("row %d: ", i);
      for (j=0; j<TEX_WIDTH+2; j++){
          printf("(%f %f %f) ", buf[(i*(TEX_WIDTH+2)+j)*3], buf[(i*(TEX_WIDTH+2)+j)*3+1], buf[(i*(TEX_WIDTH+2)+j)*3+2]);
      }
      printf("\n");
   }
}

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)
{
   printf ("Please check the support to point_sprite yourself!\n");

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