Function paint_card_surface 

pub fn paint_card_surface(
    scene: &mut Scene,
    transform: Affine,
    rect: Rect,
    alpha: f32,
    theme: &Theme,
)

The card’s body: the one floating card (crate::widget::floating_surface::paint_card), fading with the card.

Anything that stands in a column of cards (a locked-screen stand-in for them, the card for the ones that did not fit) paints this same body, so the column is one material and one shape, and the palette’s.