Function positioned 

pub fn positioned(
    tree: &mut Tree,
    limits: &Limits,
    width: impl Into<Length>,
    height: impl Into<Length>,
    padding: impl Into<Padding>,
    layout: impl FnOnce(&mut Tree, &Limits) -> Size,
    translate: impl FnOnce(Size, Size) -> Vector,
)

Available on crate feature advanced only.

Computes a padded Size with a positioning step.