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

#define WINDSIZEX 100
#define WINDSIZEY 100

#define SIZEW 4
#define SIZEH 4

static GLfloat pricol[] = {0.4, 0.2, 0.6, 0.8};//{0.3, 0.5, 0.7, 0.9 };

// Draw function used by many test casses
static void Draw()
{
   glBegin(GL_QUADS);
   glVertex2i(0,0);
   glVertex2i(0,SIZEH);
   glVertex2i(SIZEW, SIZEH);
   glVertex2i(SIZEW,0);
   glEnd();
}


void init(void)
{
   glClearColor (1,1,1,1);
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glShadeModel(GL_FLAT);
   glDisable (GL_DITHER);
   glBlendFunc(GL_ZERO, GL_SRC_ALPHA);
}

static void test(void)
{    
   GLfloat *buf;
   char cmd1[1024] = "!!ARBfp1.0\nPARAM state_param = state.depth.range;\nMOV result.color, state_param;\n\nEND";
   GLuint programName;

   //glPushAttrib(GL_ALL_ATTRIB_BITS);

   glColor4fv(pricol);

   glGenProgramsARB(1, &programName);
   // bind a program to the name
   glBindProgramARB(GL_FRAGMENT_PROGRAM_ARB, programName);
   ///////////////////////////////////////
   glProgramStringARB(GL_FRAGMENT_PROGRAM_ARB, GL_PROGRAM_FORMAT_ASCII_ARB,
	 (GLint) strlen(cmd1), cmd1);
   if(glGetError() == GL_INVALID_OPERATION) {
      printf("\nError loading program: check the error\n%s",
	    glGetString(GL_PROGRAM_ERROR_STRING_ARB));
      exit(1);
   }
   glEnable(GL_FRAGMENT_PROGRAM_ARB);
#define DR_LOW 0.3
#define DR_HI 0.8
   glDepthRange(DR_LOW, DR_HI);

   glClear(GL_COLOR_BUFFER_BIT);
   Draw();
   //////////////////////////////////////

   buf = (GLfloat *)malloc(SIZEW * SIZEH *sizeof(GLfloat) * 4);
   glReadPixels(0, 0, SIZEW, SIZEH, GL_RGBA, GL_FLOAT, buf);
   printf("get pixel at (0, 0): %f %f %f %f\n", buf[0], buf[1], buf[2], buf[3]);
   printf("should be: %f, %f, %f, 1.0\n", DR_LOW, DR_HI, DR_HI - DR_LOW);
}

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 | GLUT_DEPTH);
   glutInitWindowSize(WINDSIZEX, WINDSIZEY);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutDisplayFunc(display);
   glutMainLoop();
   return 0; 
}