Function paint_bar_body 

pub fn paint_bar_body(
    scene: &mut Scene,
    transform: Affine,
    rect: Rect,
    theme: &Theme,
    ground: AlphaColor<Srgb>,
    flush: Sides,
)

The square body of a bar standing edge to edge in the screen’s own edge, in rect: the theme’s bar finish over its own panel ground and the edge the theme gives it along its foot. Bars cast no rule at the screen’s edge (design-language.md), so a square body paints no outline; a shell’s bar paints this and its controls on top.