Use custom template with rehype-typst

[ZreXoc]

Is your feature request related to a problem? Please describe.
I want to use packages (e.g. physica) in my math, and I have patch the inlineMathTemplate and displayMathTemplate with #import "@preview/physica:0.9.4": * manually.

Describe the solution you'd like
add options that can pass custom template to rehype-typst like this:

  .use(rehypeTypst, {
     displayMathTemplate:(code)=> `
#import "@preview/physica:0.9.4": *
#set page(height: auto, width: auto, margin: 0pt)

$ ${code} $
`,
     inlineMathTemplate: `...`,
  })

or just write extra lines to be added before the default templates.

.use(rehypeTypst, {
     displayMathTemplate:`#import "@preview/physica:0.9.4": *`,
     inlineMathTemplate: `#import "@preview/physica:0.9.4": *`,
  })

And I think more than just rendering math is a good idea. Such as rendering some diagrams:

  .use(rehypeTypst, {
    {
         templates: {
          cetz: (content) => `
            #import "@preview/cetz:0.3.1"

            #cetz.canvas({
              import cetz.draw: *
              ${content}`,
          diagram: (content) => `
            #import "@preview/cetz:0.3.1"

            #cetz.canvas({
              #figure(
                diagram(
                  ${content},
                ), caption: "...",
              )
            }),
            `
        }
  }
}

```typst-cetz
circle((0, 0))
line((0, 0), (2, 1))

[Myriad-Dreamin]

Rendering fenced code really looks like a killer feature. But we can be more fit in typst-y style setup.

If I want to extend rehype-typst to support the example in description, I might make the following design:

_
.use(rehypeTypst, {
   transformers: [
     {
       type: FencedCodeMatcher,
       language: /^typst-cetz$/,
       use: 'my-cetz-template.typ',
       show: 'typst-cetz-main',
     }
   ]
}

And implement the show rule typst-cetz-main in our "my-cetz-template.typ" file:

#let typst-cetz-main(content, caption: none, ..more-args) = {
  import "@preview/cetz:0.3.1"
  show raw.where(lang: "typst-cetz"): it => cetz.canvas({
    import cetz.draw: *
    let cetz-scope = (..);
    figure(diagram(eval(it.text, cetz-scope)), caption: caption)
  })
  content        
}

It would capture the typst-cetz content and compile the content by the following template:

#import "my-cetz-template.typ": typst-cetz-main
#show: typst-cetz-main.with(..sys.inputs)
${content}

[Myriad-Dreamin]

@Enter-tainer

[Myriad-Dreamin]

eval(it.text, cetz-scope)

Add some comment, It is fancy but in practical we cannot report the error with precise source location anymore.

[Enter-tainer]

my two cents:

1. @Myriad-Dreamin 's design makes a lot of sense to me. user can register template and hook for various languages(typst-*). Just to confirm, if i understand it correctly, it is for codeblocks but not inline/block math equations.
2. Another problem is that, current template(especially inline math) is more complex than it appears to be. To correctly layout inline equations, we use black magic to query to baseline height. I think it will be unlikely to work if arbitary template is used.

[Myriad-Dreamin]

Just to confirm, if i understand it correctly, it is for codeblocks but not inline/block math equations.

The title was unmatched. I edited the title to match their description.