touying animations broken

[aarneng]

Click to show MRE

#import "@preview/touying:0.7.3": *
#import themes.university: *
#import "@preview/numbly:0.1.0": numbly
#import "@preview/theorion:0.6.0": *  // <--- importing 0.3.3 works, 0.4.0 does not
#import cosmos.clouds: *
#show: show-theorion

#show: university-theme.with(
  aspect-ratio: "16-9",
  config-common(frozen-counters: (theorem-counter,)),  // freeze theorem counter for animation
)

= test

#proposition[
  The formula:
  #pause
]

Since release 0.4.0, touying animations seem to be broken (see MRE) with all the themes clouds, default, fancy, simple, and rainbow. (with some variation, like touying's #pause working inside theorems with simple theme in version 0.4.0 but not version 0.6.0)

The error message when trying to use #pause is:

error: panicked with: "Unsupported mark `touying-jump/pause/meanwhile` at page 2. You can't use it inside some functions like `context`. You may want to use the callback-style `uncover` function instead."
   ┌─ @preview/touying:0.7.3/src/configs.typ:66:8
   │  
66 │ ╭         panic(
67 │ │           "Unsupported mark `"
68 │ │             + kind
69 │ │             + "` at page "
70 │ │             + str(page-num)
71 │ │             + ". You can't use it inside some functions like `context`. You may want to use the callback-style `uncover` function instead.",
72 │ │         )
   │ ╰─────────^

See also the discussion on the forum where the bug was originally discovered: https://forum.typst.app/t/how-to-incrementally-reveal-theorem-content-in-touying-and-theorion/8932

Possible causes:

It seems the render-fn of each theme is wrapped in a context block, due to the use of the function indent-repairer requiring it. I don't have concrete suggestions on how to fix the function, but reading the current implementation seems slightly hacky and I'm hopeful that there's a better way of doing things. (in fact it suffices to avoid putting the content of indent-repairer inside the contextual parts of the function)

If indent-repairer can be made non-contextual, the render-fn:s can then be re-written to only make if target() == "html" contextual and returning the html element early, for example the clouds theme is currently implemented by

typst-theorion/cosmos/clouds.typ

Lines 12 to 44 in 4038d9b

	// Main rendering
	let rendered = block(
	inset: 1em,
	fill: fill,
	radius: .4em,
	width: 100%,
	..args,
	indent-repairer[
	#if full-title != "" {
	strong(full-title) + sym.space
	}
	#body
	],
	)
	if "html" in dictionary(std) {
	// HTML rendering
	if target() == "html" {
	html.elem("div", attrs: (
	style: "background: "
	+ fill.to-hex()
	+ "; border-radius: .4em; padding: 1em; width: 100%; box-sizing: border-box; margin-bottom: .5em;",
	))[
	#if full-title != "" {
	strong(full-title) + sym.space.nobreak + sym.space.nobreak
	}
	#body
	]
	} else {
	rendered
	}
	} else {
	rendered
	}

and with the proposed rewrite it would look something like this:

// Main rendering
let rendered = block(
  inset: 1em,
  fill: fill,
  radius: .4em,
  width: 100%,
  ..args,
  indent-repairer[  // updated non-contextual version
    #if full-title != "" {
      strong(full-title) + sym.space
    }
    #body
  ],
)
if "html" in dictionary(std) {
  // HTML rendering
  context if target() == "html" {
    return html.elem("div", attrs: (  // return html element early
      style: "background: "
        + fill.to-hex()
        + "; border-radius: .4em; padding: 1em; width: 100%; box-sizing: border-box; margin-bottom: .5em;",
    ))[
      #if full-title != "" {
        strong(full-title) + sym.space.nobreak + sym.space.nobreak
      }
      #body
    ]
  } 
  // else
  rendered  // note that this isn't inside a context block anymore
} else {
  rendered
}

Also for the time being, if these bugs cannot be fixed the claim "Touying animation support" in the README should be updated to accurately reflect the current status