#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
test (void)
{
    GLfloat r1[4], r2[4];
    int texName;

    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glGenTextures (1, &texName);
    glBindTexture (GL_TEXTURE_1D, texName);
    glTexEnvf (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_WRAP_S,
                     GL_CLAMP_TO_BORDER_ARB);
    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_WRAP_T,
                     GL_CLAMP_TO_BORDER_ARB);

    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_COMPARE_MODE_ARB,
                     GL_COMPARE_R_TO_TEXTURE_ARB);
    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_COMPARE_FUNC_ARB,
                     GL_LEQUAL);

    glEnable (GL_DEPTH_TEST);
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glDisable (GL_TEXTURE_1D);
    glColor3f (0.0, 0.0, 1.0);

    glBegin (GL_QUAD_STRIP);
    glVertex3f (10.0, 20.0, -0.25);
    glVertex3f (10.0, 40.0, -0.25);
    glVertex3f (20.0, 20.0, -0.25);
    glVertex3f (20.0, 40.0, -0.25);
    glEnd ();

    glBegin (GL_QUAD_STRIP);
    glVertex3f (40.0, 20.0, -0.5);
    glVertex3f (40.0, 40.0, -0.5);
    glVertex3f (50.0, 20.0, -0.5);
    glVertex3f (50.0, 40.0, -0.5);
    glEnd ();

    glCopyTexImage1D (GL_TEXTURE_1D, 0, GL_DEPTH_COMPONENT, 0, 30, 64, 0);
    glTexParameteri (GL_TEXTURE_1D, GL_DEPTH_TEXTURE_MODE_ARB,
                     GL_LUMINANCE);
    glEnable (GL_TEXTURE_1D);
    glDisable (GL_DEPTH_TEST);


    glClear (GL_COLOR_BUFFER_BIT);
    glClear (GL_DEPTH_BUFFER_BIT);
    glColor3f (1.0, 0.0, 0.0);

    GLfloat z = 0.3;

    glBegin (GL_QUAD_STRIP);
    glTexCoord4f (0.0, 0.0, z, 1.0);
    glVertex2f (0.0, 0.0);
    glTexCoord4f (0.0, 1.0, z, 1.0);
    glVertex2f (0.0, 63.0);
    glTexCoord4f (1.0, 0.0, z, 1.0);
    glVertex2f (63.0, 00.0);
    glTexCoord4f (1.0, 1.0, z, 1.0);
    glVertex2f (63.0, 63.0);
    glEnd ();

    glReadPixels (15, 30, 1, 1, GL_RGBA, GL_FLOAT, &r1);
    glReadPixels (45, 30, 1, 1, GL_RGBA, GL_FLOAT, &r2);

    printf
        ("(15, 30) = (%f, %f, %f, %f), should be (0.000000, 0.000000, 0.000000, 1.000000)\n",
         r1[0], r1[1], r1[2], r1[3]);
    printf
        ("(45, 30) = (%f, %f, %f, %f), should be (1.000000, 1.000000, 1.000000, 1.000000)\n",
         r2[0], r2[1], r2[2], r2[3]);

    glDisable (GL_TEXTURE_1D);
    glDisable (GL_DEPTH_TEST);

    glFlush ();
}

void
display (void)
{
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    glOrtho (0, 63, 0, 63, 0, 1.0);
    glViewport (0, 0, 63, 63);
    test ();
}


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;
}