Function paint_window_card 

pub fn paint_window_card(
    scene: &mut Scene,
    transform: Affine,
    rect: Rect,
    theme: &Theme,
    content: impl FnOnce(&mut Scene, &Theme),
) -> Theme

A window card whose parts reach its edge: its shadow and its ground, content on that ground clipped to its shape, and its edge over the two, so a part filled to the outline (a window’s bar at the head) never cuts the card’s frame. Returns the theme a child on the card paints with, as paint_surface does for SurfaceLevel::Window.