Function selection_tier_on 

pub fn selection_tier_on(
    theme: &Theme,
    state: SelectionState,
    ground: AlphaColor<Srgb>,
) -> SelectionTier

selection_tier for a control that sits on ground rather than on surfaces.base: a list row on a sidebar, a menu row on panel_ground, a card on a sheet. The active fill is one surface step of that ground (Colors::lift_on) and hover is half a step, so a selection is the same lift on every ground, including a raised or white one where a lift of the desktop would vanish into it.