_BorderWidth
float _BorderWidth() const;
containerSize.width += 2 * _BorderWidth();
containerSize.height += 2 * _BorderWidth();
containerSize.width += 2 * _BorderWidth();
containerSize.height += 2 * _BorderWidth();
containerSize.width += 2 * _BorderWidth();
containerSize.height += 2 * _BorderWidth();
float borderWidth = _BorderWidth();