Function card 

pub fn card<V: 'static>(
    theme: &Theme,
    id: impl Into<SharedString>,
    items: &[Item],
    cursor: &Cursor,
    cx: &mut Context<'_, V>,
    on: impl Fn(&mut V, Hit, &mut Window, &mut Context<'_, V>) + 'static,
) -> Div

The panel a menu drops: every Item as a row, in a popover::popover_card, with a further panel hanging off each submenu row the Cursor holds open. id prefixes the rows’ element ids, so two menus open at once keep their hover state apart.

The pointer moves the cursor rather than lighting a row of its own, so a submenu can only ever hang off the row that is live. Everything the pointer does arrives as a Hit, dismissal included.