#ifdef _WIN32
        #include "windows.h"
#endif

#include <GL/glut.h>
#include <GL/glext.h>

#include <stdio.h>

PFNGLGENFRAMEBUFFERSPROC           glGenFramebuffers=0;
PFNGLDELETEFRAMEBUFFERSPROC        glDeleteFramebuffers=0;
PFNGLBINDFRAMEBUFFERPROC           glBindFramebuffer=0;
PFNGLCHECKFRAMEBUFFERSTATUSPROC    glCheckFramebufferStatus=0;
PFNGLFRAMEBUFFERRENDERBUFFERPROC   glFramebufferRenderbuffer=0;

PFNGLGENRENDERBUFFERSPROC          glGenRenderbuffers=0;
PFNGLDELETERENDERBUFFERSPROC       glDeleteRenderbuffers=0;
PFNGLBINDRENDERBUFFERPROC          glBindRenderbuffer=0;
PFNGLRENDERBUFFERSTORAGEPROC       glRenderbufferStorage=0;
PFNGLFRAMEBUFFERTEXTURE2DPROC      glFramebufferTexture2D=0;


void checkFBO() {
    GLenum status;
    status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if (status != GL_FRAMEBUFFER_COMPLETE) {
        printf("Error: %d", status);
    }
}

GLuint fboId;
GLuint texId;
GLuint depthId;

int width = 256;
int height = 256;

void init() {
    char *exStr =(char*)glGetString(GL_EXTENSIONS);
    if (strstr(exStr,"GL_ARB_framebuffer_object")==NULL) {
        printf("GL_ARB_framebuffer_object not supported.\n");
        exit(1);
    } if (strstr(exStr,"GL_ARB_texture_float")==NULL) {
        printf("GL_ARB_texture_float not supported.\n");
        exit(1);
    }
#ifdef _WIN32
    #define GET_PROC_ADDRESS(x) wglGetProcAddress(x);
#else
    #define GET_PROC_ADDRESS(x) glXGetProcAddress((const GLubyte*)x);
#endif

    glGenFramebuffers= (PFNGLGENFRAMEBUFFERSPROC)  GET_PROC_ADDRESS("glGenFramebuffers");
    glBindFramebuffer= (PFNGLBINDFRAMEBUFFERPROC)  GET_PROC_ADDRESS("glBindFramebuffer");
    glDeleteFramebuffers = (PFNGLDELETEFRAMEBUFFERSPROC) GET_PROC_ADDRESS("glDeleteFramebuffers");
    glCheckFramebufferStatus= (PFNGLCHECKFRAMEBUFFERSTATUSPROC)  GET_PROC_ADDRESS("glCheckFramebufferStatus");
    glGenRenderbuffers=(PFNGLGENRENDERBUFFERSPROC)GET_PROC_ADDRESS("glGenRenderbuffers");
    glBindRenderbuffer = (PFNGLBINDRENDERBUFFERPROC) GET_PROC_ADDRESS("glBindRenderbuffer");
    glRenderbufferStorage= (PFNGLRENDERBUFFERSTORAGEPROC) GET_PROC_ADDRESS("glRenderbufferStorage");
    glDeleteRenderbuffers= (PFNGLDELETERENDERBUFFERSPROC)  GET_PROC_ADDRESS("glDeleteRenderbuffers");
    glFramebufferRenderbuffer = (PFNGLFRAMEBUFFERRENDERBUFFERPROC) GET_PROC_ADDRESS("glFramebufferRenderbuffer");
    glFramebufferTexture2D = (PFNGLFRAMEBUFFERTEXTURE2DPROC)GET_PROC_ADDRESS("glFramebufferTexture2D");
}

void initFBO() {
    glPushAttrib(GL_TEXTURE_BIT | GL_COLOR_BUFFER_BIT | GL_VIEWPORT_BIT);
    glGenTextures(1, &texId);
    glBindTexture(GL_TEXTURE_2D, texId);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, width, height, 0, GL_RGBA, GL_FLOAT, NULL);

    glGenRenderbuffers(1, &depthId);
    glBindRenderbuffer(GL_RENDERBUFFER, depthId);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, width, height);

    glGenFramebuffers(1, &fboId);
    glBindFramebuffer(GL_FRAMEBUFFER, fboId);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texId, 0);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthId);

    glDrawBuffer(GL_COLOR_ATTACHMENT0);
    glReadBuffer(GL_NONE);
    glViewport(0, 0, width, height);
    checkFBO();

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glPopAttrib();
}

static void display(void) {
    glPushAttrib(GL_VIEWPORT_BIT | GL_COLOR_BUFFER_BIT);
    glBindFramebuffer(GL_FRAMEBUFFER, fboId);
    glDrawBuffer(GL_COLOR_ATTACHMENT0);
    glViewport(0, 0, width, height);
    glClearColor(0.2, 0.1, 0.3, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();
    glTranslatef(0.0, 0.0, -5.0);
    glEnable(GL_DEPTH_TEST);

    glutSolidSphere(1.0, 32, 32);

    glPopAttrib();
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();
    glTranslatef(0.0, 0.0, -3.0);

    glBindTexture(GL_TEXTURE_2D, texId);
    glEnable(GL_TEXTURE_2D);
    glDisable(GL_DEPTH_TEST);

    glBegin(GL_QUADS);
    glTexCoord2f(0.0f, 0.0f); glVertex2f(-0.5f, -0.5f);
    glTexCoord2f(1.0f, 0.0f); glVertex2f(0.5f, -0.5f);
    glTexCoord2f(1.0f, 1.0f); glVertex2f(0.5f, 0.5f);
    glTexCoord2f(0.0f, 1.0f); glVertex2f(-0.5f, 0.5f);
    glEnd();

    glDisable(GL_TEXTURE_2D);
    glBegin(GL_LINE_LOOP);
    glVertex2f(-0.5f, -0.5f);
    glVertex2f(0.5f, -0.5f);
    glVertex2f(0.5f, 0.5f);
    glVertex2f(-0.5f, 0.5f);
    glEnd();

    glutSwapBuffers();
}

static void reshape(int w, int h) {
   glViewport(0, 0, w, h);

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-1.0, 1.0, -1.0, 1.0, 0.01, 10.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

static void key(unsigned char key, int x, int y) {
    switch (key) {
        case 27 :
        case 'q':
            exit(0);
            break;
    }
    glutPostRedisplay();
}

static void idle(void) {
    glutPostRedisplay();
}

int main(int argc, char *argv[]) {
    glutInit(&argc, argv);
    glutInitWindowSize(640,480);
    glutInitWindowPosition(10,10);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);

    glutCreateWindow("OpenGL-Example");

    init();
    initFBO();

    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutKeyboardFunc(key);
    glutIdleFunc(idle);

    glutMainLoop();

    glDeleteFramebuffers(1, &fboId);
    glDeleteTextures(1, &texId);
    glDeleteRenderbuffers(1, &depthId);

    return 0;
}