Function selection_floor_ramp 

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

The face of a control that has its own floor (a filled rest face rather than a transparent one), for state, standing on ground: one ordered ramp from the ground, so rest, hover and active are each further from the ground than the last on every material, and no state mixes a floor with the transparent tier.