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

#define WINDSIZEX 100
#define WINDSIZEY 100


void
init (void)
{
    int i;
    GLfloat white[] = { 1.0, 1.0, 1.0, 1.0 };

    glClearColor (0.0, 0.0, 0.0, 1.0);
    glColor4fv (white);
    glDisable (GL_DITHER);
}


static void
drawbox (GLfloat left, GLfloat right, GLfloat top, GLfloat btm, GLfloat z)
{
    glBegin (GL_POLYGON);
    glVertex3f (left, top, z);
    glVertex3f (right, top, z);
    glVertex3f (right, btm, z);
    glVertex3f (left, btm, z);
    glEnd ();
}

#define START_QUERY(id)\
	        glBeginQueryARB(GL_SAMPLES_PASSED_ARB, id);
#define TERM_QUERY()\
	        glEndQueryARB(GL_SAMPLES_PASSED_ARB);\



static void
test (void)
{
    int i, j;
    GLuint texName;
    GLuint queryId;

    int samples;
    int ready;


    glClear (GL_COLOR_BUFFER_BIT);
    glEnable (GL_DEPTH_TEST);
    glGenQueriesARB (1, &queryId);

    if (queryId <= 0)
        return;

    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode (GL_PROJECTION);
    glPushMatrix ();
    glLoadIdentity ();
    glOrtho (-1.0, 1.0, -1.0, 1.0, 0.0, 25.0);

    glDepthMask (GL_TRUE);
    glColor3f (0.0, 1.0, 0);
    drawbox (-0.6, 0.6, 0.6, -0.6, -2.0);

    glDepthMask (GL_FALSE);

    glColor3f (0, 0, 1);
    START_QUERY (queryId);
    drawbox (-0.3, 0.3, 0.3, -0.3, -1.0);
    TERM_QUERY ();

    do
    {
        glGetQueryObjectivARB (queryId, GL_QUERY_RESULT_AVAILABLE_ARB,
                               &ready);
    }
    while (!ready);

    glGetQueryObjectuivARB (queryId, GL_QUERY_RESULT_ARB, &samples);
    printf ("number of samples passed depth test = %d\n", samples);
    printf ("should be 900\n");
    glFlush ();
}

void
display (void)
{
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    test ();
}

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