How could we go about to draw a straight line (vertical or horizontal) on top of any other window on our Linux desktop? I'm using i3 window manager with picom compositor at present, so I'm primarily interested in solutions that works for that.

I should get back to this question in the future and implement a nicer solution than pango-view

pango-view

Produces a vertical line (actually, more of a vertical box of limited width).
Very easy to make it, just issue the command in a terminal. pango-view was already installed.

$ pango-view --height=99999 --margin=1 --background=red -t ''

• https://forum.puppylinux.com/viewtopic.php?p=76743 relevant, very good and recent
• https://askubuntu.com/questions/328543/are-there-any-tools-for-drawing-on-the-desktop-drawing-over-apps
• gromit-mpx is a good over-app painter, but does not provide perfectly straight lines
• https://www.linuxfordevices.com/tutorials/linux/tools-to-draw-on-linux-screen

Using biblatex with a numeric style and a book class with frontmatter/mainmatter, would it be possible to have all citations in the frontmatter appear last in the list of references, as if the frontmatter (from biblatex's point of view) appeared after the mainmatter?

\documentclass{book}
\usepackage[utf8]{inputenc}

\usepackage[backend=biber,sorting=none,style=nature]{biblatex}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@misc{hydrogen,
  author = {Author, A.},
  year = {2001},
  title = {Alpha}}
@misc{neodymium,
  author = {Luthor, Lex.},
  year = {2002},
  title = {Bravo}}
\end{filecontents}
\addbibresource{\jobname.bib}

\frontmatter
\cite{neodymium}

\mainmatter
\cite{hydrogen}

\backmatter
\printbibliography[title={List of references}]

\end{document}

In the above MWE, references in the "List of references" are printed in the same order as they were given in the document, so neodymium would be listed before hydrogen in the "List of references".
This also means that the citation in the frontmatter would be labelled [1] in the text and the first citation in the mainmatter would be labelled [2].
This is just as expected with the numeric style as often used in science and engineering theses.

I wonder if there is some way to make the first citation in the mainmatter be [1] (because it might be jarring for the reader to see the first citation in the first chapter be something like [11], it may make them wonder what they missed), without having a separate \printbibliography for the frontmatter (nor using refsection or refsegments, because I don't think they will help in this case). Preferably any citations in the frontmatter would simply be appended to the end of "List of references", as if the frontmatter was processed after the frontmatter by biblatex.

I think this would be hard to achieve. But I'd like to hear if anyone knows better?
Would something like this be possible? Have I missed something obvious?

I have read the Sorting section in the biblatex manual, and read these related (but not-very-pertinent) questions on TeX.SE

• https://tex.stackexchange.com/questions/540610/numbering-issue-in-printbiblography/540615
• https://tex.stackexchange.com/questions/306678/biblatex-have-two-separate-bibliographies-with-consecutive-numbering
• https://tex.stackexchange.com/questions/244150/citations-out-of-order-with-appendix-and-split-bibliographies-in-backmatter