How to tell a heading element's font size?

Questions
1

I was trying to modify the table of contents in my document such that each entry has the same typographical styling as the headings they reference. This is important to abide by some styling rules in academia.

So far, I’ve written the following show rule:

#show outline.entry: it => link(
  it.element.location(),
  [
    #set par(first-line-indent: 0pt)
    #grid(columns: (1fr, 7fr), it.prefix(), it.inner())
  ],
)

I suppose that it.element are the heading elements in my document, however, their font size is not preserved if I were to use it.prefix() or it.inner().

Not only that, I was trying to add a title element to my document, but setting it’s size with show title: set text(size: 1em) doesn’t give me text with the same size as the currently set size.

I image there’s some factor that multiplies the current font size prior to the set text(size: 1em), but I can’t tell by the documentation. I don’t know how I could use context to figure it out either.

2

By default, it’s 1.4em for level 1, 1.2em for level 2 and no scaling for the other heading levels.

3

Nice, I can figure out how to get what I want with this!

I’m just interested in a further understanding: changing the font size to 1em doesn’t actually override this 1.4em factor, right? So, if I wanted my heading element to have the same font size as normal text, I would need to show heading.where(level: 1): set text(size: 0.7143em)?

4

You can interrogate your template’s text sizes this way:
(I don’t think you should use advanced state contraptions to adapt heading styles after this, prefer to keep it simple if you can.)

Regular text size is #context text.size.
#let tsize = state("plain-text-size")
#context tsize.update(text.size)

Heading sizes are scaled as follows:
#show heading: it => it + context (text.size/tsize.get())
#show title: it => it + context (text.size/tsize.get())
#title[Title]
= H1
== H2
=== H3

image
image530×682 33.6 KB

1 Like
5

Yes that’s correct. It’s fine to write it as 1em/1.4 too. You can also use an absolute size like 11pt if you want.

The general concept is that style changes using set or show-set are cumulative with existing styles for the same element.

6

Are these factors something I can change or are they set in Rust without a Typst function to modify them? If I can’t modify them, how sure can I be they’ll remain the same over updates?

7

You can modify them only by setting a style in the ways we discussed. It’s possible that these default styles will change in a new Typst version. Not likely, but not impossible.

8

I understand. However, I’m still finding trouble to fix the issue with regards to the table of contents. I’m writting a template, so there’s no guarantee that the end user won’t change the default font size from 1.4em to something else. So I need a way to tell the font size of each heading, which is something I imagine is achievable with context and state but I’m not sure how.

Should I open up another question for this?

9

Based on @bluss first answer, I’ve updated my code to the following:

#show heading: it => {
  let heading-font-size = state("heading-font-size")
  heading-font-size.update(text.size)
  [#it#text.size]
}

#show outline.entry: it => link(
  it.element.location(),
  [
    #let heading-font-size = state("heading-font-size")
    #heading-font-size.at(it.element.location())
    #set text(size: heading-font-size.at(it.element.location()))
    #set par(first-line-indent: 0pt)
    #grid(columns: (1fr, 7fr), align: bottom, it.prefix(), it.inner())
  ],
)

#outline()
#pagebreak()

= Level 1
== Level 2
=== Level 3
==== Level 4

And I get something like this:

image
image1116×570 28.1 KB

image
image497×423 18.6 KB

It’s pretty weird that retrieving the font size for the level 2 heading in the table of contents is failing while the rest is “delayed” by one level.

10

I’m hesitant about trying to solve this with state. It’s your template, so you can have the template dictate the heading sizes (or ask the user to configure them through the template).

I have this way to solve your state problem, using final values and one variable per heading level. That assumes heading sizes don’t change through the document though.

#show heading: it => {
  let heading-font-size = state("heading-font-size:" + str(it.level))
  heading-font-size.update(text.size)
  [#it#text.size]
}

#show outline.entry: it => link(
  it.element.location(),
  [
    #let heading-font-size = state("heading-font-size:" + str(it.element.level))
    #set text(size: heading-font-size.final())
    #set par(first-line-indent: 0pt)
    #grid(columns: (1fr, 7fr), align: bottom, it.prefix(), it.inner())
  ],
)

The explanation for the off by one problem in state is, I think: think of the .at(location) as pointing to a location where the header starts. That happens to be just before where the state update happens. That’s my guess.

1 Like