Function link 

pub fn link(title: &str, destination: &str) -> ViewHandle

Link(_:destination:) — a label that opens a URL.

A LocalizedStringKey in x0 through x3, then the URL by address. The crate builds URLs as Optional<URL> because that is what init?(string:) returns; a .some keeps its payload at offset zero, so the same buffer serves where a bare URL is wanted.