Sketch Lustre

In case you’re here and don’t know Sketch, take a look at sketch package!

This readme is a carbon-copy of the Sketch Lustre section in sketch readme.

Setup

If you’re using Lustre (which is strongly recommended), sketch_lustre got you. sketch_lustre exposes one entrypoint, sketch/lustre, containing everything needed to get started.

// main.gleam
import lustre
import sketch
import sketch/lustre as sketch_lustre

pub fn main() {
  // Initialise the cache. Two strategies can be used. Ephemeral caches are designed as throw-away caches.
  let assert Ok(stylesheet) = sketch.stylesheet(strategy: sketch.Ephemeral)
  // Generate the partial view function, compatible with Lustre's runtime.
  lustre.simple(init, update, view(_, stylesheet))
  // And voilà!
  |> lustre.start("#app", Nil)
}

fn view(model, stylesheet) {
  // Add the sketch CSS generation "view middleware".
  use <- sketch_lustre.render(stylesheet, [sketch_lustre.node()])
  // Run your actual view function.
  my_view(model)
}

Usage

sketch_lustre exposes two modules to help you build your site, similarly to Lustre: sketch/lustre/element and sketch/lustre/element/html. The first one let you use raw element generation and exposes the Sketch Lustre Element(msg) type, that can be used (almost) interchangeably with Lustre, and element helpers, i.e. element, fragment, or even keyed.

Because a sketch_lustre view function expects an sketch/lustre/element.Element(msg) to paint, you should now write all your view functions to return Sketch elements. All Sketch elements can be instanciated with element, or with the corresponding sketch/lustre/element/html.element. An element accepts the same thing as a Lustre element, but includes a sketch.Class value as first argument. That class will be applied to the final generated element.

NB: all elements can be generated using the correct function, or using its “underscored” version. In the second case, Sketch Lustre behaves exactly like Lustre, and will not add another class. This is helpful when you want to use a simple node, without any class linked on it.

import sketch/css
import sketch/css/length.{px}
import sketch/lustre/element
import sketch/lustre/element/html

fn main_style() {
  css.class([
    css.background("red"),
    css.font_size(px(16)),
  ])
}

fn view(model: Int) {
  html.div(main_style(), [], [
    html.div_([], [
      html.text(int.to_string(model)),
    ]),
  ])
}

And you’re done! Enjoy your Lustre app, Sketch-enhanced!

Final notes

On Sketch Lustre Element

A Sketch Element(msg) is extremely similar to a Lustre Element(msg), excepted it carries styles information on top. Going from a sketch/lustre/element.Element(msg) to a lustre/element.Element(msg) is straightforward, by using sketch/lustre/element.unstyled. The opposite (going from a Lustre element to a Sketch Lustre element) is also possible by using sketch/lustre/element.styled!

Sketch Lustre Experimental

Because sometimes you may want to avoid the Element(msg) overhead, you can try the experimental Sketch Lustre runtime, sketch_lustre_experimental. That runtime works in the same way, excepts it does not implements its own Element type on top of Lustre’s Element. Most of the time, you should not see any differences. Keep in mind that it can bug though, as it’s still experimental. If you try to use it, please, report any bugs you can find.

Usage with Shadow DOM

In browser, Sketch can work with a Shadow DOM, in order to hide the compiled styles from the rest of the application. With a proper shadow root (represented as a Dynamic in Gleam), you can use sketch/lustre.shadow() to render a stylesheet in the shadow root directly. In the same way you can initialize the cache to render in document or in a style node, you can use a shadow root to paint styles in your application!