Color text on set of subslides

[JoshuaLampert]

First of all, thank you for the very nice package. I recently built my own template based on my previous LaTeX template and managed to create almost identical results (while benefiting from typst and touying compared to LaTeX and beamer).
I mainly have two issues, which currently hinder me in completely switching to typst for presentations (this issue and an upcoming one).
I usually heavily use coloring of certain parts (in LaTeX with \color<>[]{}), i.e. I want some text (or part of a formula) to be colored only in a set of subslides. If I haven't missed anything, this is currently not supported by touying out-of-box. After looking at the source code, I figured out I can hack something together by defining it on my own. See https://typst.app/project/r2RWPmJouYepvYdkL3EtPE for an MWE. This already works quite nicely in simple situations, but doesn't work for more complex ones, where I need the callback style because IIUC I cannot get my colors function by utils.methods(self). Note that my example works without the semi-transparent-cover, which I don't quite understand.
Is there interest in including such a function in touying? If yes, I would be happy to create a PR with an initial suggestion.

[OrangeX4]

This is because semi-transparent-cover will place paused contents into a context expression, making touying-fn-wrapper cannot working properly. However, you can use config-methods(color: my color) to add it to methods and obtains it by #let (uncover, color) = utils.methods(self).

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

#let my_color(self: none, visible-subslides, col, cont) = {
  if utils.check-visible(self.subslide, visible-subslides) {
    text(fill: col, cont)
  } else {
    cont
  }
}

#let color(visible-subslides, col, cont) = {
  touying-fn-wrapper(
    my_color,
    last-subslide: utils.last-required-subslide(visible-subslides),
    visible-subslides,
    col,
    cont,
  )
}

#show: simple-theme.with(
  aspect-ratio: "16-9",
  config-methods(
    cover: utils.semi-transparent-cover.with(alpha: 85%),
    color: my_color,
  ),
)

= Title

== Title of Slide

#color("2-", red, "this works as I want")

#slide(repeat: 3, self => [
  #let (uncover, color) = utils.methods(self)
  This doesn't:

  $ f(x) &= (x + 1)^2 \
    uncover("2-", color("2", #red, &= x^2 + x + x + 1)) \
    uncover("3", &= x^2 + 2x + 1)
  $
])

[OrangeX4]

Thanks for your comments, I'm not against including such a function into touying, but I think it should be more elegant designed, for example we might use syntax.

#effect("2", text.with(fill: red))[Something]

[JoshuaLampert]

Ah, that makes sense! Thanks!

Thanks for your comments, I'm not against including such a function into touying, but I think it should be more elegant designed, for example we might use syntax.

Yes, that's true. I like your suggestion. That would also make it more general. I would really like to see this feature in touying.

[OrangeX4]

I may consider it further in the future, thanks.

[JoshuaLampert]

I see a function #effect is included in touying:0.5.4. So thanks a lot for that @OrangeX4. However, I noticed that the callback-style doesn't seem to work with #effect, see my MWE here: https://typst.app/project/rBorvFignPms9v2tUqFSxz. I guess this is because effect is not listed here:

touying/src/configs.typ

Lines 375 to 387 in e54003c

	methods: _get-dict-without-default((
	init: init,
	cover: cover,
	uncover: uncover,
	only: only,
	alternatives-match: alternatives-match,
	alternatives: alternatives,
	alternatives-fn: alternatives-fn,
	alternatives-cases: alternatives-cases,
	alert: alert,
	show-notes: show-notes,
	convert-label-to-short-heading: convert-label-to-short-heading,
	)) + args.named(),

Is that intentional? And if not could it be added?
I also noticed a typo in the example of the docstring for the function here:

touying/src/core.typ

Line 492 in e54003c

/// Example: `#effect(text.with(fill: red), "2-")[Something]` will display `[Something]` if the current slide is 2 or later.

I guess the example should rather read #effect("2-", text.with(fill: red))[Something]?

[OrangeX4]

I forgot to add it to methods, I will add it in the next version.

#effect(text.with(fill: red), "2-")[Something] is right, because I am considering an abbreviation by using #let effect-red = effect.with(text.with(fill: red))

[JoshuaLampert]

I forgot to add it to methods, I will add it in the next version.

Great, thanks! Do you have a rough estimate, when that will be? I'm considering updating my template to touying:0.5.4. But if version 0.5.5 will be out soon, I will directly update it to 0.5.5.

#effect(text.with(fill: red), "2-")[Something] is right, because I am considering an abbreviation by using #let effect-red = effect.with(text.with(fill: red))

I'm not sure I understand. visible-subslides and fn are positional arguments. So #effect(text.with(fill: red), "2-")[Something] as you suggest in the example simply errors as it is the wrong order of arguments. In the example you don't use the abbreviation effect-red? But also something like

#let effect-red = effect.with(text.with(fill: red))
effect-red("2-")[Something]

doesn't work because of the same reason. I updated the above link to demonstrate it. Maybe I'm misunderstanding what you mean. Could you clarify?

[OrangeX4]

I made a mistake, I'm sorry, I will immediately release a new version to fix.

[JoshuaLampert]

Thanks!

[JoshuaLampert]

I saw your fix f56991b. That already looks nice. I have a small suggestion. I think the easiest is to make the suggestion in a PR. Is this fine for you @OrangeX4?

[OrangeX4]

Oh, I have already released a new waiting version. Since I have been busy recently, I just rushed to deal with these things, so it may be a little rough :-(