#define GL_GLEXT_PROTOTYPES
#include <GL/gl.h>
#include <GL/glext.h>
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define TEX_W 256
#define TEX_H 256

#define CHECK_GLERROR()                                     \
{                                                           \
    GLenum err = glGetError();                              \
    while (err != GL_NO_ERROR)                              \
    {                                                       \
        fprintf(stderr, "GL Error %#x, %s, line %d\n",      \
                err, __FILE__, __LINE__);                   \
        err = glGetError();                                 \
    }                                                       \
}

void init(void)
{
    GLuint tex, fbo;
    GLenum status;

    /* Generate a destination texture */
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, TEX_W, TEX_H, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, NULL);
    CHECK_GLERROR();

    /* Prepare a fbo with the texture as color attachment */
    glGenFramebuffersEXT(1, &fbo);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex, 0);
    glViewport(0, 0, TEX_W, TEX_H);
    CHECK_GLERROR();
    status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
    if (status != GL_FRAMEBUFFER_COMPLETE_EXT) fprintf(stderr, "FBO status %#x\n", status);

    glClearColor(0.0, 0.0, 1.0, 0);
    glClear(GL_COLOR_BUFFER_BIT);
    CHECK_GLERROR();

    glEnable(GL_CULL_FACE);
    glCullFace(GL_FRONT);
    glFrontFace(GL_CCW);
    CHECK_GLERROR();

    glColor4f(0.0, 1.0, 0.0, 1.0);
    glBegin(GL_TRIANGLES);
    glVertex3f(-1.0, -1.0, -1.0);
    glVertex3f(-1.0,  1.0, -1.0);
    glVertex3f( 1.0,  1.0,  1.0);
    glEnd();

    glColor4f(1.0, 0.0, 0.0, 1.0);
    glBegin(GL_TRIANGLES);
    glVertex3f( 1.0, -1.0,  1.0);
    glVertex3f( 1.0,  1.0,  1.0);
    glVertex3f(-1.0, -1.0, -1.0);
    glEnd();
    CHECK_GLERROR();

    glDisable(GL_CULL_FACE);
    CHECK_GLERROR();

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    glBindTexture(GL_TEXTURE_2D, tex);
    glEnable(GL_TEXTURE_2D);
    glClearColor(1.0, 1.0, 1.0, 1.0);
    glViewport(0, 0, 200, 200);
    glColor4f(1.0, 1.0, 1.0, 1.0);
    CHECK_GLERROR();
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);

    glBegin(GL_QUADS);
    glTexCoord2f(0.0, 0.0);
    glVertex3f(-1.0, -1.0, -0.5);
    glTexCoord2f(0.0, 1.0);
    glVertex3f(-1.0,  1.0, -0.5);
    glTexCoord2f(1.0, 1.0);
    glVertex3f( 1.0,  1.0, -0.5);
    glTexCoord2f(1.0, 0.0);
    glVertex3f( 1.0, -1.0, -0.5);

    glEnd();
    glFlush();
    glutSwapBuffers();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_ACCUM);
    glutInitWindowSize(200, 200);
    glutCreateWindow(argv[0]);
    init();

    glutDisplayFunc(display);
    glutIdleFunc(display);
    glutMainLoop();
    return 0;
}