QPainterPath will not add a null element
AFAIK it is undocumented that appending a null element, for example a lineTo(the current end point of the path), doesn't actually add anything to a QPainterPath.
path = QPainterPath(QPointF(0,0))
previousCount = path.elementCount()
assert path.elementCount() > previousCount@
The assertion fails. I can understand the reason for it, but it did catch me by surprise.