onMouseOver method
Implementation
@HostListener('mouseover')
void onMouseOver(MouseEvent event) {
// If not triggered by mouse movement, don't handle it. This can happen when
// the DOM moved but mouse didn't.
if (!_isMouseDriven) return;
var item = _itemForTarget(event.target);
if (item == null) return;
// Hovering on items clear the selection.
activeModel?.activate(null);
_hoveredItem = item;
_subMenuOpener?.start();
}