WIP threaded FBO read back - requires GLFW

ThreadedFBOReadback.cpp

//
//  ThreadedFBOReadback.cpp
//
//  Created by Theodore Watson on 9/16/14.
//
//

#include "ThreadedFBOReadback.h"
#include "ofAppGLFWWindow.h"

GLFWwindow * gpuWindow = NULL;
GLFWwindow * mainWindow = NULL;

ThreadedFBOReadback::ThreadedFBOReadback(){
    bNeedsToRun = false;
    width = height = 0;
}

void ThreadedFBOReadback::setup( int _width, int _height, int glType, int numSamples){
    width   = _width;
    height  = _height;
    
    mainWindow = glfwGetCurrentContext();
    renderFbo.allocate(width, height, glType, numSamples);
}

void ThreadedFBOReadback::begin(){
    if( bNeedsToRun == false ){
        renderFbo.begin();
    }
}

void ThreadedFBOReadback::end(){
    if( bNeedsToRun == false ){
        renderFbo.end();
        startRender();
    }
}

float ThreadedFBOReadback::getWidth(){
    return width;
}

float ThreadedFBOReadback::getHeight(){
    return height;
}

void ThreadedFBOReadback::startRender(){
    bNeedsToRun = true;
    if( isThreadRunning() == false ){
        startThread();
    }
}

void ThreadedFBOReadback::stopRender(){
    bNeedsToRun = false;
}

void ThreadedFBOReadback::threadedFunction(){
    while( ofThread::isThreadRunning() ){
    
        if(bNeedsToRun && renderFbo.isAllocated() ){
        
            if( gpuWindow == NULL ){
              glfwWindowHint(GLFW_VISIBLE, GL_FALSE);
              gpuWindow = glfwCreateWindow(width, height, "HiddenWindowForSecondContext", 0, mainWindow);
            }
            
            //this tells this thread to use this context
            //shouldn't have to do this for the main thread as that doesn't get unset by this call.
            glfwMakeContextCurrent(gpuWindow);
            renderFbo.readToPixels(outPixels);
            stopRender();
        }
        yield();
    }
}


ofPixels ThreadedFBOReadback::getPixels(){
    return outPixels;
}

ThreadedFBOReadback.h

//
//  ThreadedFBOReadback.h
//
//  Created by Theodore Watson on 9/16/14.
//
//

#pragma once
#include "ofMain.h"

class ThreadedFBOReadback : public ofThread{

    public:
    
        ThreadedFBOReadback();
    
        //setup your FBO
        //using an internal FBO for now as I thought some crashes were due to simultanous use of same fbo.
        //probably cleaner to allow passing in fbo.
        void setup( int width, int height, int glType, int numSamples );

        //use to capture contents into fbo
        //on end() the pixels are downloaded into a second thread.
        //NOTE: right now you can't call begin until threaded readback is finished.
        void begin();
        void end();
    
        float getWidth();
        float getHeight();
    
        //this is dumb for now - needs a isFrameNew type flag
        //not doing it for now as trying to avoid needing to lock
        ofPixels getPixels();

    protected:
        void threadedFunction();

        void startRender();
        void stopRender();
        int width, height; 
    
        bool bNeedsToRun;

        ofPixels outPixels;
        ofFbo renderFbo;

};