How to combine heading and enum counters?

Questions
, ,
1

I want to use Typst to write simple legal documents like non-profit organization statutes. I would like to write something like this

/* ... #show/#set magic ... */

#title()

// unnumbered
= Preamble

#lorem(5)

// numbered
= Heading of section I

+ #lorem(5)
+ #lorem(5)
  + #lorem(5) <a>
  + #lorem(5)
+ #lorem(5)
+ ... as defined in @a, and @b

// numbered
= Heading of section II

+ #lorem(5) <b>
+ #lorem(5)

in order to get a result like this (mocked in libreoffice)

image
image652×544 47.6 KB

I no problem with modifying the heading to show the “Section …” numbering, I can probably figure out how to make the Preamble section unnumbered, but I have been unable to work out how to make the cross-references work such that they combine the section number and the enum item with proper nesting. I got close using @preview/itemize:0.2.0 (which solves referencing enum items which is not possible in vanilla typst), but I was unable to do the last step of combining with the section counter. Any tips on how to do that?

2

Hi. Since in the public API you cannot get the position of the reference enum item when customizing the numbering, you have 3 options:

  • Ask author to add this feature in some way
  • Copy the source code and modify the logic
  • Copy the minimal code and hope it works
Copy the whole thing (around 170 LoC) 
#import "@preview/itemize:0.2.0": config, default-enum

#set heading(numbering: "I")
#set enum(numbering: "1.a.")
#show: default-enum
#show <unnumbered>: set heading(numbering: none)

#let enum-label-ID = "__cdl_enum-label-ID__"
#let curr-parent-level = state("__enum-parent-number__", ())
#let enum-numbering = state("__enum-numbering__", (
  numbering: "1.1.1.1.1.",
  full: false,
))
#let curr-base-parent-level = state("__curr-base-parent-level__", ())

// https://github.com/tianyi-smile/itemize/blob/main/src/util/numbering.typ
#let numbering-kind-from-char(c) = {
  let numberings = (
    "1",
    "a",
    "A",
    "i",
    "I",
    "α",
    "Α",
    "*",
    "א",
    "一",
    "壹",
    "あ",
    "い",
    "ア",
    "イ",
    "ㄱ",
    "가",
    "\u{0661}",
    "\u{06F1}",
    "\u{0967}",
    "\u{09E7}",
    "\u{0995}",
    "①",
    "⓵",
  )
  if c in numberings { c }
}

#let numbering-pattern-from-str(pattern) = {
  let pieces = ()
  let handled = 0
  let pattern-to-codepoints = pattern.codepoints()
  for (i, c) in pattern-to-codepoints.enumerate() {
    let kind = numbering-kind-from-char(c)
    if kind == none { continue }
    let prefix = pattern-to-codepoints.slice(handled, i).join()
    pieces.push((prefix, kind))
    handled = 1 + i
  }

  let suffix = pattern-to-codepoints.slice(handled).join()
  if pieces.len() == 0 {
    panic("invalid numbering pattern")
  }
  (pieces: pieces, suffix: suffix, trimmed: false)
}

#let apply-numbering-kth(numbering, k, number) = {
  let fmt = ""
  let self = numbering-pattern-from-str(numbering)
  if self.pieces.len() > 0 {
    let (prefix, _) = self.pieces.first()
    fmt += prefix
    let (_, kind) = if k < self.pieces.len() {
      self.pieces.at(k)
    } else {
      self.pieces.last()
    }
    fmt += std.numbering(kind, number)
  }
  fmt += self.suffix
  return fmt
}

#let ref-enum(
  it,
  full: auto,
  numbering: auto,
  supplement: auto,
  no-label-warning: false,
) = {
  let el = it.element
  if el != none {
    if (
      el.func() == text
        or el.func() == enum.item
        or el.func() == metadata and el.value == enum-label-ID
    ) {
      let enum-count = curr-parent-level.at(it.target)
      if enum-count.len() > 0 {
        let supplement-body = if it.supplement == auto {
          if supplement not in (auto, [], none) {
            [#supplement#h(0em, weak: true)~]
          }
        } else {
          [#it.supplement#h(0em, weak: true)~]
        }
        let number-body = if numbering != auto {
          let _full = full
          let _numbering = numbering
          let (
            numbering,
            full,
            auto-base-level,
            curr-enum-level,
          ) = enum-numbering.at(it.target)
          if auto-base-level {
            if (_full == auto and full) or (_full == true) {
              let base-num-count = curr-base-parent-level.at(it.target)
              [#std.numbering(_numbering, ..base-num-count)]
            } else {
              [#apply-numbering-kth(
                _numbering,
                curr-enum-level,
                enum-count.last(),
              )]
            }
          } else {
            if (_full == auto and full) or (_full == true) {
              [#std.numbering(_numbering, ..enum-count)]
            } else {
              [#apply-numbering-kth(
                _numbering,
                enum-count.len() - 1,
                enum-count.last(),
              )]
            }
          }
        } else {
          let _full = full
          let (
            numbering,
            full,
            auto-base-level,
            curr-enum-level,
          ) = enum-numbering.at(it.target)
          if auto-base-level {
            if (_full == auto and full) or (_full == true) {
              let base-num-count = curr-base-parent-level.at(it.target)
              [#std.numbering(numbering, ..base-num-count)]
            } else {
              [#apply-numbering-kth(
                numbering,
                curr-enum-level,
                enum-count.last(),
              )]
            }
          } else {
            if (_full == auto and full) or (_full == true) {
              let last-heading = counter(heading).at(el.location()).first()
              [#std.numbering(
                heading.numbering.first() + "." + numbering,
                last-heading,
                ..enum-count,
              )]
            } else {
              [#apply-numbering-kth(
                numbering,
                enum-count.len() - 1,
                enum-count.last(),
              )]
            }
          }
        }
        link(el.location(), [#supplement-body#number-body])
      } else {
        it
      }
    } else {
      it
    }
  } else {
    if no-label-warning [#text(weight: "bold", fill: red)[[???]]] else { it }
  }
}

#show ref: ref-enum.with(full: true)

#set document(title: [Title])
/* ... #show/#set magic ... */

#title()

// unnumbered
= Preamble <unnumbered>

#lorem(5)

// numbered
= Heading of section I

+ #lorem(5)
+ #lorem(5)
  + #lorem(5) <a>
  + #lorem(5)
+ #lorem(5)
+ ... as defined in @a, and @b

// numbered
= Heading of section II

+ #lorem(5) <b>
+ #lorem(5)

Or a minimal solution (17 LoC):

#import "@preview/itemize:0.2.0": config, default-enum

#set heading(numbering: "I")
#set enum(numbering: "1.a.")
#show: default-enum
#show ref: it => {
  let curr-parent-level = state("__enum-parent-number__", ())
  let default = (numbering: "1.1.1.1.1.", full: false)
  let enum-numbering = state("__enum-numbering__", default)
  let enum-label-ID = "__cdl_enum-label-ID__"
  if it.element == none { return it }
  let el = it.element
  let is-metadata = el.func() == metadata and el.value == enum-label-ID
  if el.func() not in (text, enum.item) and not is-metadata { return it }
  let enum-count = curr-parent-level.at(it.target)
  if enum-count.len() == 0 { return it }
  let (numbering, ..) = enum-numbering.at(it.target)
  let last-section = counter(heading).at(el.location()).first()
  let numbering = heading.numbering.first() + "." + numbering
  let num = std.numbering(numbering, last-section, ..enum-count)
  link(el.location(), num)
}
#show <unnumbered>: set heading(numbering: none)

#set document(title: [Title])
/* ... #show/#set magic ... */

#title()

// unnumbered
= Preamble <unnumbered>

#lorem(5)

// numbered
= Heading of section I

+ #lorem(5)
+ #lorem(5)
  + #lorem(5) <a>
  + #lorem(5)
+ #lorem(5)
+ ... as defined in @a, and @b

// numbered
= Heading of section II

+ #lorem(5) <b>
+ #lorem(5)

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image223×302 21.6 KB