@Override
        public double getY() {
            return super.getY() - boundsTop;
        }
The algorithm calculates the position starting with the root at 0. I.e.
the left children will get negative positions. However we want the result
to be normalized to (0,0).
<p>
{@link NormalizedPosition} will normalize the position (given relative to
the root position), taking the current bounds into account. This way the
left most node bounds will start at x = 0, the top most node bounds at y
= 0.
stroom-core-client-widget/src/main/java/stroom/widget/htree/client/treelayout/AbegoTreeLayout.java