Function vertical_separator 

pub fn vertical_separator(
    scene: &mut Scene,
    transform: Affine,
    x: f64,
    y0: f64,
    y1: f64,
    inset: f64,
    surface: AlphaColor<Srgb>,
)

A 1 px vertical separator between two columns or panes, derived against surface like separator, inset inset from both ends and centred on x. The column rule of a painted split, a gutter beside a list.