Convert heading to latex command

[ramiromagno]

Description

How to go from (.qmd):

# Acknowledgments {.bmsection}

to latex (.tex):

\bmsection*{Acknowledgments}

Do I need to write a lua filter?

[dragonstyle]

I think a filter is your best bet. There is this filter which almost (but not quite, I think) does what you're looking for:

https://github.com/quarto-ext/latex-environment

Might be a nice addition to this extension - I'll try to add it soon!

[cscheid]

I'm going to just write out the solution because this is a good "Hello, World" filter from which you can learn to generalize:

-- filter.lua

-- this function will be executed for all Header elements in the document
Header = function(el)
  -- el.level == 1 makes it so you only catch "# ..." and not "## ...", etc
  -- el.classes is a pandoc List object, which has the method "includes"
  if el.level == 1 and el.classes:includes("bmsection") then
    -- pandoc.utils.stringify converts a pandoc value (in this case,
    -- the list of inlines that make up the header) into a plain string.
    local text = pandoc.utils.stringify(el.content)

    -- a RawBlock element contains a string that is passed through
    -- directly to the final element.
    local result = pandoc.RawBlock("latex", "\\bmsection*{" .. text .. "}")
    return result
  else
    -- a "return nil" statement is implied at the end of a lua function, but
    -- if you want to be explicit, you can add it.
    -- returning "nil" means "do not modify this element"
    return nil
  end
end

For the following document,

---
title: test
filters:
  - filter.lua
---

Some text.

# Acknowledgments {.bmsection}

Some acks.

You get this output:

$ quarto render 6228.qmd --to latex
$ tail 6228.tex
\maketitle
Some text.

\bmsection*{Acknowledgments}

Some acks.



\end{document}

[ramiromagno]

Hey guys!,

Thank you so much for your flash answers!

@dragonstyle : Indeed, I am already using the latex-environment extension, it's quite useful! But yeah, using it for environments only.

@cscheid : thank you so much for sharing the lua filter code! Valeu!

P.S. the more I use Quarto, the more I understand I'll have to learn Pandoc & Lua... :)

[ramiromagno]

@cscheid I am so happy I managed to adapt your code to handle unnumbered sections (probably not the most idiomatic Lua code, but works!):

Header = function(el)
  -- el.level == 1 makes it so you only catch "# ..." and not "## ...", etc
  -- el.classes is a pandoc List object, which has the method "includes"
  if el.level == 1 and el.classes:includes("bmsection") then
    if el.classes:includes("unnumbered") then
      -- pandoc.utils.stringify converts a pandoc value (in this case,
      -- the list of inlines that make up the header) into a plain string.
      local text = pandoc.utils.stringify(el.content)

      -- a RawBlock element contains a string that is passed through
      -- directly to the final element.
      local result = pandoc.RawBlock("latex", "\\bmsection*{" .. text .. "}")
      return result
    else
      -- pandoc.utils.stringify converts a pandoc value (in this case,
      -- the list of inlines that make up the header) into a plain string.
      local text = pandoc.utils.stringify(el.content)

      -- a RawBlock element contains a string that is passed through
      -- directly to the final element.
      local result = pandoc.RawBlock("latex", "\\bmsection{" .. text .. "}")
      return result
    end
  else
    -- a "return nil" statement is implied at the end of a lua function, but
    -- if you want to be explicit, you can add it.
    -- returning "nil" means "do not modify this element"
    return nil
  end
end

You don't happen to know how I could change it still to handle references, i.e. to take

# Heading text {#ref .bmsection .unnumbered}

and convert

\bmsection*{heading text\label{ref}}

[mcanouil]

Checkout the documentation page for Lua development and the native format to get a better sense of what the Lua filter is reading/modifying: https://quarto.org/docs/extensions/lua.html.

[ramiromagno]

Thanks for the pointer!