MapView constructor:
MapView::MapView(World* mWorld, QWidget* parent)
: QOpenGLWidget(parent)
, world(mWorld)
, camera(new Camera(this))
, ...
{
    setFocusPolicy(Qt::StrongFocus);
    setMouseTracking(true);

    QSurfaceFormat format;
    format.setDepthBufferSize(24);
    format.setMajorVersion(4);
    format.setMinorVersion(3);
    format.setSamples(4);
    format.setProfile(QSurfaceFormat::CoreProfile);
    format.setOption(QSurfaceFormat::DebugContext);

    QSurfaceFormat::setDefaultFormat(format);

    surface = new QOffscreenSurface();
    surface->setFormat(format);
    surface->create();

    qDebug() << "surface validation:" << surface->isValid(); // return true

    // Initialize the camera position and orientation
    camera->setPosition(QVector3D(250.0f, 10.0f, 250.0f));
    camera->setViewCenter(QVector3D(250.0f, 10.0f, 249.0f));
    camera->setUpVector(QVector3D(0.0f, 1.0f, 0.0f));

    // Assign camera to World
    world->setCamera(camera);

    startTimer(16);
}

MapView intializeGL:
void MapView::initializeGL()
{
    QOpenGLContext* _context = world->getContext();

    qDebug() << _context->makeCurrent(surface); // return true
    qDebug() << _context->isValid() << (QOpenGLContext::currentContext() == _context); // return true true

    initializeOpenGLFunctions(); // its still working? or have I call gl funcs from world?

    // Initialize World
    world->initialize(/*this->context(),*/ size(), worldCoords);

    // Initialize camera shader
    camera->initialize();

    // Enable depth testing
    world->getGLFunctions()->glEnable(GL_DEPTH_TEST);
    world->getGLFunctions()->glEnable(GL_CULL_FACE);

    world->getGLFunctions()->glDepthFunc(GL_LEQUAL); // just testing new depth func

    world->getGLFunctions()->glClearColor(0.65f, 0.77f, 1.0f, 1.0f);
}

MapView paintGL: I think there is some problem
void MapView::paintGL()
{
    world->getContext()->makeCurrent(surface);

    world->getGLFunctions()->glDrawBuffer(GL_FRONT);
    world->getGLFunctions()->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    world->draw(...);

    //world->getContext()->swapBuffers(surface); // not working even uncommented
}

World initialize:
void World::initialize(/*QOpenGLContext* context,*/ QSize fboSize, bool** mapCoords)
{
    GLfuncs = context->versionFunctions<QOpenGLFunctions_4_2_Core>();

    if(!GLfuncs)
    {
        qDebug() << QObject::tr("Requires OpenGL >= 4.2");

        qFatal(QObject::tr("Requires OpenGL >= 4.2").toLatin1().data());

        exit(1);
    }

    GLfuncs->initializeOpenGLFunctions();
    ...
}