Offset getAbsolutePaintOffset({Offset paintOffset, ViewportAnchor anchor })

Returns the offset at which to paint the content, accounting for the given anchor and the dimensions of the viewport.

Source 

Offset getAbsolutePaintOffset({ Offset paintOffset, ViewportAnchor anchor }) {
  assert(_debugHasAtLeastOneCommonDimension);
  switch (anchor) {
    case ViewportAnchor.start:
      return paintOffset;
    case ViewportAnchor.end:
      return paintOffset + (containerSize - contentSize);
  }
  assert(anchor != null);
  return null;
}