Adaptive content size for Touying

theme.typ

// This theme is from https://github.com/andreasKroepelin/polylux/blob/main/themes/simple.typ
// Author: Andreas Kröpelin

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

// https://forum.typst.app/t/how-to-auto-size-text-and-images/1290
#let fill-height-with-text(min: 0.3em, max: 5em, eps: 0.1em, debug: false, it) = layout(size => {
  let fits(text-size, it) = {
    measure(width: size.width, {
        set text(text-size)
        it
      }).height <= size.height
  }

  let debug-msg = []
  if not fits(min, it) {
    debug-msg += "Failed: min size too large"
    it
  } else if fits(max, it) {
    debug-msg += "1 render"
    set text(max)
    it
  } else {
    let (a, b) = (min, max)
    let cnt = 0
    while b - a > eps {
      cnt += 1
      let new = 0.5 * (a + b)
      if fits(new, it) {
        a = new
      } else {
        b = new
      }
    }

    debug-msg += [#cnt renders]

    set text(a)
    it
  } + if debug and debug-msg != [] {
    place(
      top + right,
      block(
        fill: teal.transparentize(50%),
        inset: 6pt,
        text(16pt)[
          #debug-msg
        ],
      ),
    )
  } else []
})

#let adaptive-composer = (composer: auto, debug: false, precise-size: true, ..bodies) => components.side-by-side(
  composer: composer,
  ..bodies.pos().map(it => block(
    height: 1fr,
    fill-height-with-text(
      max: 1em,
      eps: if precise-size {
        0.01em
      } else {
        0.1em
      },
      debug: debug,
      it,
    ),
  )),
);

#let slide = (debug: false, precise-size: true, ..args) => slide(
  composer: adaptive-composer.with(debug: debug, precise-size: precise-size),
  ..args,
)

// debug: display re-render attempts
// precise-size: trade size accuracy with speed
#let theme = (debug: false, precise-size: true, ..args) => simple-theme(
  primary: black,
  config-common(slide-fn: slide.with(debug: debug, precise-size: precise-size)),
  ..args,
)