// calculate dimension
            if(m_anchor & A_BOTTOM && m_anchor & A_TOP)
            {
                m_dimension.y = m_parent->GetDimension().y - (m_margin.bottom +  m_margin.top);
            }
            if(m_anchor & A_LEFT && m_anchor & A_RIGHT)
            {
                m_dimension.x = m_parent->GetDimension().x - (m_margin.left +  m_margin.right);
            }