QScrollArea in Qml: Flickable + QQuickPaintedItem

[alan73]

I'm trying to realize something similiar to QScrollArea (in widgets world) with the help of Qml.
I decided to probe Flickable plus QQuickPaintedItem based item (named Drawer in my case):

Flickable {
  ...
  onContentXChanged(): {
  drawer.update()
  }

Drawer {
  id: drawer
  ...
}

Drawer's render target is set to FrameBufferObject. Its paint function looks like this:

void Drawer::paint(QPainter *painter)
{
   // Some function to compute rect which is needed to be redrawn
   QRect updateRect = computeUpdateRect();

   // How to shift contents of Frame buffer, e.g. to right, and draw only updateRect in this space?
}

Imagine how we do scrolling in QScrollArea widget, e.g. to left: all entry of viewport is shifted to right and the only small rect in left is redrawn.
I want to do the same with Flickable+QQuickPaintedItem. But I can't understand some things:

1. How can I manipulate Frame Buffer object inside QQuickPaintedItem?
2. Maybe there is some more right way to implement QScrollArea in QML?

By the way, is double buffering enabled by default in QQuickPaintedItem?