Function build_vertical_lists 

pub fn build_vertical_lists(
    tex_engine: &dyn TexEngine,
    auxiliary_files: &HashMap<PathBuf, Vec<u8>>,
    preamble: &str,
    contents: &mut dyn Iterator<Item = &String>,
) -> (HashMap<String, u32>, Vec<VList>)

Build verticals list from some text.

This function works by putting the text inside a TeX \vbox{\noindent \hsize=41pt} and then instructing TeX to describe the contents of the box.

This function is the inverse of TeX.2021.173 and onwards (part 12 of TeX: displaying boxes).