void ConvertFromParentCoords(nscoord* aX, nscoord* aY) { *aX -= mPosX; *aY -= mPosY; }
void ConvertFromParentCoords(nscoord* aX, nscoord* aY) const { *aX -= mPosX; *aY -= mPosY; }
  void ConvertFromParentCoords(nscoord* aX, nscoord* aY) { *aX -= mPosX; *aY -= mPosY; }