Adding bibliography with empty title breaks slide titles in university theme

[joschakrug]

Hi all,

when trying to include a bibliography into a presentation using the university theme, subsequent slide headings are breaking once I set the bibliography title to none. (This does not occur when using the simple theme.)

In the PDF generated from the minimum working example below, the second appendix slide still gets the title 'Appendix slide 1':

#import "@preview/touying:0.6.1": *

// no problem when using the simple theme
// #import themes.simple: *
// #show: simple-theme

// ... but subsequent slide headings break in university theme
#import themes.university: *
#show: university-theme

== Main body

#slide[
  Cite something to have a non-empty bibliography @Asterix-2025
]

== References

#slide[
  #bibliography(
    bytes(
      "@book{Asterix-2025,
        title = {Magic Potions for Great Slides},
        author = {Asterix and Obelix},
        date = {2025},
      }"
    ),
    title: none
  )
]

== Appendix slide 1

#slide[
  This should have title 'Appendix slide 1'
]

== Appendix slide 2

#slide[
  This should have title 'Appendix slide 2'
]

My current workaround is to include a title and use a show rule to set its size to .01pt and its fill colour to white, but that is obviously a quick hack rather than an actual solution.

[Lyrics2196]

TLDR

Insert a blank element before the #bibliography function, for example:

== References

#slide[
  #v(0pt) // <---  Invisible element
  #bibliography(
    bytes(
      "@book{Asterix-2025,
        title = {Magic Potions for Great Slides},
        author = {Asterix and Obelix},
        date = {2025},
      }",
    ),
    title: none,
  )
]

This will resolve the issue.

Cause

This problem appears to originate from Typst's special handling of #bibliography() during rendering, causing a conflict with Touying. More specifically, the issue arises when calling #utils.curret-heading (the university theme uses this function), where the page numbers of headings retrieved via the #query function become problematic. In the provided code snippet, I inserted the following code to more straightforwardly illustrate this issue:

== Appendix slide 1

#slide[
  #context {
    let depth = 999
    let current-page = here().page()
    let headings = query(heading)

    for h in headings {
      let page-num = h.location().page()
      [Heading: "#h.body", Level: #h.level, Page: #page-num \ ]
    }
  }

  This should have title 'Appendix slide 1'
]

After rendering, the code yields:

Appendix slide 1

Heading: “Main body”, Level: 2, Page: 1

Heading: “References”, Level: 2, Page: 2

Heading: “Appendix slide 2”, Level: 2, Page: 3

Heading: “Appendix slide 1”, Level: 2, Page: 3

This should have title ‘Appendix slide 1’

Solution

When the page containing the #bibliography function has other content, all headings gain correct positions. Therefore, you can insert a Invisible element before the #bibliography function, for example:

== References

#slide[
  #v(0pt)
  #bibliography(
    bytes(
      "@book{Asterix-2025,
        title = {Magic Potions for Great Slides},
        author = {Asterix and Obelix},
        date = {2025},
      }",
    ),
    title: none,
  )
]

This will resolve the issue.