public override void SelectElement(GraphicElement el)
        {
            DeselectCurrentSelectedElement();

            if (el != null)
            {
                var els = EraseIntersectionsTopToBottom(el);
                el.Select();
                DrawBottomToTop(els);
                UpdateScreen(els);
                selectedElements.Add(el);
                ElementSelected.Fire(this, new ElementEventArgs()
                {
                    Element = el
                });
            }
        }