Omitting headers/page numbers on empty pages #3122

Thank you! This is super helpful. I'll probably keep this as a separate file and import into my template, since it's quite a lot of code for what can be succinctly bundled in a function call. :)

Are you sure this is not just the difference between the value of counter(page) and the absolute page number loc.page()? If possible, could you provide an example that reproduces your issue?

Yes. it appears to be related to the labels that are used here.

#set page(header: locate(loc => [Header is on page #loc.page()]))

#show heading.where(level: 1): it => locate(loc => [
  #[]<label>
  #pagebreak(to: "odd", weak: true)
  Heading is on page #loc.page() \
])

= L1 Heading
#locate(loc => [This text is on page #loc.page()])

= L1 Heading
#locate(loc => [This text is on page #loc.page()])

Produces

If you remove/comment the line with the label, the heading location is as intended.

It looks like you can force the page counter to update by wrapping it in a context. I was not able to make this work within the scope of the locate(loc => []) function but I don't think you absolutely need to use this since you can just use #here().page() or counter(page).display() to get the current page. https://typst.app/project/rdMJcjjGmGQC25pkLndmTY

Okay, but you still have a number on your "blank" page, which to get rid of, was the reason for this endeavor.

Sure, this solution only shows the modification of the headers. But you can just apply the same principle to the footer. The function page-header() can differentiate between an <empty-page>, a <new-chapter> page and any other page.

You can use this function to hide the page number on empty pages (but not on pages where a new chapter starts). It also alternates the position of the page number between left and right (for even and odd pages):

#let page-footer = context {
  // since the page breaks in chapter-heading() are inserted after the <empty-page> label,
  // the selector has to look "before" the current page to find the relevant label
  let empty-page-labels = query(selector(<empty-page>).before(here()))
  if empty-page-labels.len() > 0 {
    let empty-page = empty-page-labels.last().location().page()
    // look back at the most recent <new-chapter> label
    let new-chapter = query(selector(<new-chapter>).before(here())).last().location().page()
    // check that there is no <new-chapter> label on the current page
    if (new-chapter != here().page()) and (empty-page + 1 == here().page()) {
      return
    }
  }

  // left/right align the page number on even/odd pages
  let page-display = counter(page).display(here().page-numbering())
  return if calc.even(here().page()) { page-display } else { h(1fr) + page-display }
}

let page-display = counter(page).display(here().page-numbering())
//---------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^

causes the Error: Expected string, function, or auto, found none

I added the page-footer to my example project here https://typst.app/project/rmC_x90uIy0QcD-4lMcakP.

I could reproduce your error by omitting #set page(numbering: "1"). Please check if you have your page numbering set up correctly.

Now it works!

This looks great! Thank you very much for posting your solution. I have to admit that I never checked the bookmarks in a PDF viewer since I was just playing around with the headers in a template in the web app...

I found that your solution only worked with version v0.12.0. When I tried version v0.11.1, the table of contents was not correct and the bookmarks were not working either. Do you know what actually changed between the versions?

yes, this was just fixed recently

All locatable elements now emit a start and an end tag instead of just a single tag. This is primarily useful for future work on Tagged PDF, but it also allows us to correctly determine the exact position of an element in cases where we previously couldn't. In the case of show heading: it => pagebreak() + it, the heading's position will be after the pagebreak because neither visible content nor the matching end tag occurred before the pagebreak. Meanwhile, in metadata("hi") + pagebreak(), the position of the metadata will be before the pagebreak because it's end tag already appeared before the pagebreak. Notably, this means that the nesting of zero-sized elements is not necessarily preserved in the tag output (if the metadata was inside of the heading show rule, it remains before the pagebreak, but the heading migrates to after it).

As the comment mentions, this does not include the case where metadata is inserted before the pagebreak, hence the workaround with the state variables.

@jhalmen Your solution works perfectly. I have to change some minor things to adapt it to my needs. Thank you for sharing this. However, it would be great if it was an option passed to pagebreak (even if I understand it will not the case in a near future).

Thanks to nleanba on the forums this can actually be simplified to just:

#show heading.where(level: 1, outlined: true): it => {
    pagebreak(weak: true)
    state("blank-page").update(true)
    pagebreak(to: "odd", weak: true)
    state("blank-page").update(false)
    it
}
#set page(footer: context {
    if not state("blank-page", false).get() {
      align(center, counter(page).display())
    }
 })

resulting possibly in a bit less layout iterations