Function expand_path_signed 

pub fn expand_path_signed(
    path: impl Shape,
    expand: Diagonal2,
    join: Join,
    miter_limit: f64,
    tolerance: f64,
) -> BezPath

Expand a path when the sign is known.

Applies the expansion based on the path orientation, so that expansion happens with positive expand values on subpaths with negative area, or vice versa. This is backwards from the intuitive sign convention, but results from the choice of convention for the offset primitives.