libj/J/fbo.h

#ifndef FBO_H
#define FBO_H

#include <map>
#include <iostream>
#include <stdexcept>

#include "to_string.h"

#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>

// TODO: more error checking in debug build.
// TODO: make texture class? for easier switching between linear/nearest interpolation for example

class fbo {
public:
    typedef std::map<GLenum, GLuint> RenderbuffersMap;
    
	int width, height;
	GLuint fbo_number;
	RenderbuffersMap renderbuffers;
	GLuint texture_id;

public:
	fbo(int width, int height) : width(width), height(height), fbo_number(0), renderbuffers(), texture_id(0) {
		glGenFramebuffers(1, &fbo_number);
		bind();

		// generate texture
		glGenTextures(1, &texture_id);
		glEnable(GL_TEXTURE_2D);
		glBindTexture(GL_TEXTURE_2D, texture_id);
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_BYTE, 0);
		glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture_id, 0);

		// attach depth
		create_attach_renderbuffer(GL_DEPTH_COMPONENT, GL_DEPTH_ATTACHMENT);

		// attach stencil
		//create_attach_renderbuffer(GL_STENCIL_INDEX, GL_STENCIL_ATTACHMENT);

		check_status();

		glClearColor(0.0, 0.0, 0.0, 0.0);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		unbind();
	}
	~fbo() {
		end();

		glDeleteFramebuffers(1, &fbo_number);

		for(RenderbuffersMap::const_iterator i = renderbuffers.begin(); i != renderbuffers.end(); ++i){
            RenderbuffersMap::value_type const & it = *i;
			glDeleteFramebuffers(1, &it.second);
		}

		glDeleteTextures(1, &texture_id);
	}

	void begin(){
		bind();
        // FIXME: this should be done, but also switching back should be done...
		//glPushAttrib(GL_VIEWPORT);
		//glViewport(0, 0, width, height);

        // NOTE: commented out, because we don't want fbo's to nest.
		/*GLint savedFramebuffer = -1;
		glGetIntegerv(GL_FRAMEBUFFER_BINDING, &savedFramebuffer);
		std::cout << "sfb: " << savedFramebuffer << ", fbo: " << fbo_number << std::endl;*/
	}

	void end(){
		unbind();
        // FIXME: switch back to previous viewport.
		//glPopAttrib();
	}

private:
	void bind(){
		glBindFramebuffer(GL_FRAMEBUFFER, fbo_number);

		GLenum status = glGetError();
		if(status != GL_NO_ERROR)
			throw std::runtime_error("i has error" + std::to_string(status) + "with fbo: " + std::to_string(fbo_number));
	}

	void unbind(){
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
	}

	void create_attach_renderbuffer(GLenum format, GLenum attachment_point) {
		GLuint buffer;
		glGenRenderbuffers(1, &buffer);
		glBindRenderbuffer(GL_RENDERBUFFER, buffer);
		glRenderbufferStorage(GL_RENDERBUFFER, format, width, height);
		glFramebufferRenderbuffer(GL_FRAMEBUFFER, attachment_point, GL_RENDERBUFFER, buffer);

		renderbuffers[format] = buffer;
	}

	void check_status() {
		GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
		switch(status) {
		case GL_FRAMEBUFFER_COMPLETE:
			std::cout << "FRAMEBUFFER_COMPLETE - OK" << std::endl;
			return;
		case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
			std::cout << "FRAMEBUFFER_INCOMPLETE_ATTACHMENT" << std::endl;
			break;
		case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
			std::cout << "FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT" << std::endl;
			break;
		case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS:
			std::cout << "FRAMEBUFFER_INCOMPLETE_DIMENSIONS" << std::endl;
			break;
		case GL_FRAMEBUFFER_UNSUPPORTED:
			std::cout << "FRAMEBUFFER_UNSUPPORTED" << std::endl;
			break;
		default:
			std::cout << "UNKNOWN FRAMEBUFFER ERROR" << std::endl;
			break;
		}
		//throw std::runtime_error("I will not continu..");
	}

	void check_error(){
		GLenum status = glGetError();
		if(status != GL_NO_ERROR){
			throw std::runtime_error("GL Error: " + std::to_string(status));
		}
	}

};

#endif // FBO_H