#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)
{
    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)
{
        int i, j;
        const int MAX = 2;
        GLint maxBuf = -1, n, val;
        GLenum buffers[MAX], err;
        GLint initDrawBuffer;

        glGetIntegerv(GL_DRAW_BUFFER, &initDrawBuffer);

        glGetIntegerv(GL_MAX_DRAW_BUFFERS, &maxBuf);
        if (maxBuf < 1) {
                return;
        }

        n = maxBuf < MAX ? maxBuf : MAX;
        for (i = 0; i < n; i++) {
                buffers[i] = (i & 1) ? GL_FRONT_LEFT : GL_BACK_LEFT;
        }

        glDrawBuffers(n, buffers);

        for (i = 0; i < n; i++) {
                glGetIntegerv(GL_DRAW_BUFFER0 + i, &val);
                if (val != (GLint) buffers[i]) {
			printf("glGetIntegerv(GL_DRAW_BUFFER%c) returns wrong buffer\n", '0'+i);
                }
        }

}

void
display (void)
{
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    gluOrtho2D (0, WINDSIZEX, 0, WINDSIZEX);
    test ();
}

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

}