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

#define WINDSIZEX 100
#define WINDSIZEY 100
#define TEXSIZE 2


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);

    // Check if GL_EXT_framebuffer_object is supported
    if (!strstr (glGetString (GL_EXTENSIONS), "GL_EXT_framebuffer_object"))
    {
        printf ("GL_EXT_framebuffer_object is not supported\n");
	exit(0);
    }
    else
    {
        printf ("GL_EXT_framebuffer_object is supported\n");
    }
}

#define CHECK_FRAMEBUFFER_STATUS()                            \
{                                                           \
        GLenum status;                                            \
        status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT); \
        switch(status) {                                          \
          case GL_FRAMEBUFFER_COMPLETE_EXT:                       \
            printf("GL_FRAMEBUFFER_COMPLETE_EXT\n");              \
            break;                                                \
          case GL_FRAMEBUFFER_UNSUPPORTED_EXT:                    \
            printf("GL_FRAMEBUFFER_UNSUPPORTED_EXT\n");           \
            /* choose different formats */                        \
            break;                                                \
          case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:          \
            printf("GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT\n"); \
            break;                                                \
          case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:          \
            printf("GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT\n"); \
            break;                                                \
          case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:             \
            printf("GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT\n");    \
            break;                                                \
          case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:         \
            printf("%d:GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT\n", __LINE__);\
            break;                                                \
          case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:         \
            printf("GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT\n");\
            break;                                                \
          default:                                                \
            /* programming error; will fail on all hardware */    \
            printf("programming error\n");                        \
            break;                                                \
        }                                                         \
}


static void
test (void)
{
    GLfloat red[] = { 1.0, 0.0, 0.0, 1.0 };
    GLfloat white[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat green[] = { 0.0, 1.0, 0.0, 1.0 };
    GLuint fbs[1];
    GLuint textures[1];
    GLint t[TEXSIZE * TEXSIZE * 3];
    int i, j;


    glClearColor (0.0, 0.0, 0.0, 1.0);
    glClear (GL_COLOR_BUFFER_BIT);

    glGenFramebuffersEXT (1, fbs);
    glGenTextures (1, textures);

    glBindTexture (GL_TEXTURE_1D, textures[0]);
    glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glTexImage1D (GL_TEXTURE_1D, 0, GL_RGB, TEXSIZE, 0,
                  GL_RGB, GL_INT, NULL);
    printf ("glTexImage1D: %s\n", gluErrorString (glGetError ()));

    glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, fbs[0]);
    glFramebufferTexture1DEXT (GL_FRAMEBUFFER_EXT,
                                   GL_COLOR_ATTACHMENT0_EXT,
                                   GL_TEXTURE_1D, textures[0], 0);
    CHECK_FRAMEBUFFER_STATUS ();

    // Render to the texture
    glBindTexture (GL_TEXTURE_1D, 0);
    glDisable (GL_TEXTURE_1D);
    glColor4fv (red);
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear (GL_COLOR_BUFFER_BIT);

    glBegin (GL_LINE);
    glVertex2f (0, 0);
    glVertex2f (TEXSIZE, 0);
    glEnd ();

    // Render to the window
    glEnable (GL_TEXTURE_1D);
    glBindTexture (GL_TEXTURE_1D, textures[0]);
    glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, 0);
    printf ("glBindFramebufferEXT: %s\n", gluErrorString (glGetError ()));
    glBindTexture (GL_TEXTURE_2D, textures[0]);

    glEnable (GL_TEXTURE_1D);
    glColor4fv (white);
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear (GL_COLOR_BUFFER_BIT);

    glBegin (GL_POLYGON);
    glTexCoord2f (0.0, 0.0);
    glVertex2f (0, 0);
    glTexCoord2f (1.0, 0.0);
    glVertex2f (TEXSIZE, 0);
    glTexCoord2f (1.0, 1.0);
    glVertex2f (TEXSIZE, TEXSIZE);
    glTexCoord2f (0.0, 1.0);
    glVertex2f (0, TEXSIZE);
    glEnd ();
    GLfloat buf[WINDSIZEX * WINDSIZEY * 3];

    printf ("read out pixels:\n");
    glReadPixels (0, 0, WINDSIZEX, WINDSIZEY, GL_RGB, GL_FLOAT, buf);

    for (j = 0; j < WINDSIZEY; j++)
    {
        for (i = 0; i < WINDSIZEY; i++)
        {
            if (buf[(j * WINDSIZEX + i) * 3] != 0
                || buf[(j * WINDSIZEX + i) * 3 + 1] != 0
                || buf[(j * WINDSIZEX + i) * 3 + 2] != 0)
            {
                printf ("(%d, %d) = [%f, %f, %f]\n", i, j,
                        buf[(j * WINDSIZEX + i) * 3],
                        buf[(j * WINDSIZEX + i) * 3 + 1],
                        buf[(j * WINDSIZEX + i) * 3 + 2]);
            }
        }
    }

    glFlush ();
    glDeleteTextures(1, textures);
    glDeleteFramebuffersEXT(1, fbs);
}

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

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

}