Fix frozen-counters bug with multiple #pause commands

[enklht]

Description

This PR addresses a bug in the frozen-counters functionality where status updates show unexpected behavior when using multiple #pause commands. This issue may be related to #72.

Problem

When using multiple #pause commands, figure captions are not correctly incremented. For example, in the example below with multiple figures and pauses, the final figure might be captioned as "Figure 2:" though it should be "Figure 3:".

#import "@preview/touying:0.5.3": *
#import themes.simple: *

#show: simple-theme

== slide 1
#figure([test figure], caption: [caption])

== slide 2
#figure([test figure], caption: [caption])
#pause
paused

== slide 3
#figure([test figure], caption: [caption])
#pause
paused

Solution

Instead of storing the counter value at the beginning of a sequence of subslides, we now store the location. We then use status.at(location) to rewind the status when needed. This approach ensures that counters are correctly updated across pauses and slides.

Testing

I have tested my code with examples given in the examples folder in this repository, besides the example above, and two examples in #72. All of them compiled with no errors / warnings.

---

• As I'm not fluent in Typst, my code might not be fully ideomatic. I welcome any revisions or improvements to the implementation.
• It might be better to store the location in some outer variable (e.g. #utils.current-slide) and update it when creating a new slide, instead of querying the label for every new subslide.
• minor fix: I found a variable named current, which is not used, so I deleted it.

[enklht]

It might be better to store the location in some outer variable (e.g. #utils.current-slide) and update it when creating a new slide, instead of querying the label for every new subslide.

I found this idea won't work because Typst doesn't allow changing outer variables within a context. Therefore, querying the label for every new subslide is necessary with this approach.

[enklht]

I added a new state #utils.loc-prior-newslide to store the location of parent slides. This simplifies the code and improves readability (and performance?) The implementation works well in testing. Sorry for sending multiple comments in a short period.

[OrangeX4]

Thank! I'll check it out later.

[OrangeX4]

Thanks, I think your method is more elegant.

[OrangeX4]

With this PR, we can also add the counter(heading) to the frozon-counters: 34bfe9e

[enklht]

Yes, and that resolves the issue #83.