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

#define WINDSIZEX 100
#define WINDSIZEY 100

void init(void)
{
}

static const char progStr[] =
"!!ARBvp1.0\n\
	OUTPUT otex0 = result.texcoord[0];\n\
	\n\
	PARAM EX2const = { 0.000000, -2.000000, 1.000000, -1.000000 };\n\
	EX2 otex0, EX2const.y;\n\
	END\n\n\
	\0";


static void test(void)
{
    GLuint vpHandle;
    const   GLsizei FEEDBACK_SIZE = 1024;
    const   GLenum  FEEDBACK_TYPE = GL_4D_COLOR_TEXTURE;
    GLfloat buf[1024];
    GLint   feedbackSize;
    GLint errorPosition; 

    // enable the extension
    glEnable(GL_VERTEX_PROGRAM_ARB);

    //Generate the vertex program and have the API return the VP handle
    glGenProgramsARB(1, &vpHandle);

    //Bind the program with the handle that contains the vertex program
    glBindProgramARB(GL_VERTEX_PROGRAM_ARB, vpHandle);

    glProgramStringARB(GL_VERTEX_PROGRAM_ARB,
	    GL_PROGRAM_FORMAT_ASCII_ARB,
	    (GLint) strlen((const char*)progStr), progStr);

    glGetIntegerv(GL_PROGRAM_ERROR_POSITION_ARB, &errorPosition);

    if (errorPosition != -1) {
	printf("\nERROR loading vertex program!  Error position = %d\n",
		errorPosition);
	exit(1);
    }

    glFeedbackBuffer(FEEDBACK_SIZE, FEEDBACK_TYPE, buf);
    feedbackSize = glRenderMode(GL_FEEDBACK);

    glBegin( GL_POINTS );
    glVertex3f(0.25f, 0.25f, 0.0f);
    glEnd();
    feedbackSize = glRenderMode(GL_RENDER);

    printf("feedback size: %d\n", feedbackSize);
    printf("feedback buffer:%f %f %f %f\n", buf[9], buf[10], buf[11], buf[12]);
    printf("it should be: 0.25 0.25 0.25 0.25\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)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(WINDSIZEX, WINDSIZEY);
    glutInitWindowPosition(100, 100);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0; 
}