glGenFramebuffersEXT(1, &fbo);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &fbo_texture);
glBindTexture(GL_TEXTURE_2D, fbo_texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_width, m_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbo_texture, 0);
GLenum status;
if ((status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT)) != GL_FRAMEBUFFER_COMPLETE_EXT) {
    fprintf(stderr, "glCheckFramebufferStatus: error %p", status);
}
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

#include "main.hpp"

GLuint fbo, fbo_texture, rbo_depth;
GLuint vbo_fbo_vertices;
GLuint program_postproc, attribute_v_coord_postproc, uniform_fbo_texture;
GLuint vs, fs;
Shader shader;

int main(void)
{
    init();

    glGenFramebuffersEXT(1, &fbo);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
    glEnable(GL_TEXTURE_2D);
    glGenTextures(1, &fbo_texture);
    glBindTexture(GL_TEXTURE_2D, fbo_texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_width, m_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbo_texture, 0);

    GLenum status;
    if ((status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT)) != GL_FRAMEBUFFER_COMPLETE_EXT) {
        fprintf(stderr, "glCheckFramebufferStatus: error %p", status);
    }
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

    GLfloat fbo_vertices[] = { -1, -1, 1, -1,-1,  1, 1,  1 };
    glGenBuffers(1, &vbo_fbo_vertices);
    glBindBuffer(GL_ARRAY_BUFFER, vbo_fbo_vertices);
    glBufferData(GL_ARRAY_BUFFER, sizeof(fbo_vertices), fbo_vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    shader.load("shaders/post_processing.vert", "shaders/post_processing.frag");

    attribute_v_coord_postproc = glGetAttribLocation(shader.program(), "v_coord");
    if (attribute_v_coord_postproc == -1) {
        fprintf(stderr, "Could not bind attribute %sn", "v_coord");
        return 0;
    }
    uniform_fbo_texture = glGetUniformLocation(shader.program(), "fbo_texture");
    if (uniform_fbo_texture == -1) {
        fprintf(stderr, "Could not bind uniform %sn", "fbo_texture");
        return 0;
    }

    while (!glfwWindowShouldClose(m_window))
    {
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
        glClear(GL_COLOR_BUFFER_BIT);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
        glClear(GL_COLOR_BUFFER_BIT);
        shader.use();
        glBindTexture(GL_TEXTURE_2D, fbo_texture);
        glUniform1i(uniform_fbo_texture, /*GL_TEXTURE*/0);
        glEnableVertexAttribArray(attribute_v_coord_postproc);
        glBindBuffer(GL_ARRAY_BUFFER, vbo_fbo_vertices);
        glVertexAttribPointer(attribute_v_coord_postproc, 2, GL_FLOAT, GL_FALSE, 0, 0);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
        glDisableVertexAttribArray(attribute_v_coord_postproc);
        glfwSwapBuffers(m_window);
        glfwPollEvents();
    }

    glDeleteRenderbuffersEXT(1, &rbo_depth);
    glDeleteTextures(1, &fbo_texture);
    glDeleteFramebuffersEXT(1, &fbo);
    glDeleteBuffers(1, &vbo_fbo_vertices);
    glDeleteProgram(shader.program());
    glfwDestroyWindow(m_window);
    glfwTerminate();
    exit(EXIT_SUCCESS);
}

void callbackError(int error, const char* description)
{
    fputs(description, stderr);
}

void callbackKey(GLFWwindow* window, int key, int scancode, int action, int mods)
{
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);
}

void callbackFramebufferSize(GLFWwindow* window, int width, int height)
{
   m_width = width; m_height = height;
    glBindTexture(GL_TEXTURE_2D, fbo_texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_width, m_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
    glBindTexture(GL_TEXTURE_2D, 0);
}

void init()
{
    glfwSetErrorCallback(callbackError);
    if (!glfwInit()) exit(EXIT_FAILURE);
    m_width = 800; m_height = 600;
    m_window = glfwCreateWindow(m_width, m_height, "Framebuffer Test", NULL, NULL);
    if (!m_window) { glfwTerminate(); exit(EXIT_FAILURE); }
    glfwMakeContextCurrent(m_window);
    glfwSwapInterval(0);
    glfwSetKeyCallback(m_window, callbackKey);
    glfwSetFramebufferSizeCallback(m_window, callbackFramebufferSize);
    glewExperimental = GL_TRUE;
    if (glewInit() != GLEW_OK) std::cout << "GLEW Init Error" << std::endl;
    glClearColor(0.2, 0.3, 0.4, 1.0);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}

attribute vec2 v_coord;
uniform sampler2D fbo_texture;
varying vec2 f_texcoord;

void main(void)
{
    gl_Position = vec4(v_coord, 0.0, 1.0);
    f_texcoord = (v_coord + 1.0) / 2.0;
}

uniform sampler2D fbo_texture;
varying vec2 f_texcoord;

void main(void)
{
    gl_FragColor = texture2D(fbo_texture, f_texcoord);
    if (f_texcoord.x < 0.2)
    gl_FragColor *= vec4(1.0, 2.0, 1.0, 1.0);
    else if (f_texcoord.x > 0.8)
    gl_FragColor *= vec4(1.0, 2.0, 2.0, 1.0);
    else  gl_FragColor *= vec4(2.0, 1.0, 2.0, 1.0);
}

glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &fbo_texture);
glBindTexture(GL_TEXTURE_2D, fbo_texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_width, m_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fbo_texture, 0);

glBindFramebufferEXT(GL_FRAMEBUFFER, 0);