Styling Web Components

Celý článek

Nolan Lawson has a little emoji-picker-element that is awfully handy and incredibly easy to use. But considering you’d probably be using it within your own app, it should be style-able so it can incorporated nicely anywhere. How to allow that styling isn’t exactly obvious:

What wasn’t obvious to me, though, was how to allow users to style it. What if they wanted a different background color? What if they wanted the emoji to be bigger? What if they wanted a different font for the input field?

Nolan list four possibilities (I’ll rename them a bit in a way that helps me understand them).

1. CSS Custom Properties: Style things like background: var(--background, white);. Custom properties penetrate the Shadow DOM, so you’re essentially adding styling hooks.
2. Pre-built variations: You can add a class attribute to the custom elements, which are easy to access within CSS inside the Shadow DOM thanks to the pseudo selectors, like :host(.dark) { background: black; }.
3. Shadow parts: You add attributes to things you want to be style-able, like <span part="foo">, then CSS from the outside can reach in like custom-component::part(foo) { }.
4. User forced: Despite the nothing in/nothing out vibe of the Shadow DOM, you can always reach the element.shadowRoot and inject a <style>, so there is always a way to get styles in.

It’s probably worth a mention that the DOM you slot into place is style-able from “outside” CSS as it were.

This is such a funky problem. I like the Shadow DOM because it’s the closest thing we have on the web platform to scoped styles which are definitely a good idea. But I don’t love any of those styling solutions. They all seem to force me into thinking about what kind of styling API I want to offer and document it, while not encouraging any particular consistency across components.

To me, the DOM already is a styling API. I like the scoped protection, but there should be an easy way to reach in there and style things if I want to. Seems like there should be a very simple CSS-only way to reach inside and still use the cascade and such. Maybe the dash-separated custom-element name is enough? my-custom-elemement li { }. Or maybe it’s more explicit, like @shadow my-custom-element li { }. I just think it should be easier. Constructable Stylesheets don’t seem like a step toward make it easier, either.

Last time I was thinking about styling web components, I was just trying to figure out how to it works in the first place, not considering how to expose styling options to consumers of the component.

Does this actually come up as a problem in day-to-day work? Sure does.

I don’t see any particularly good options in that thread (yet) for the styling approach. If I was Dave, I’d be tempted to just do nothing. Offer minimal styling, and if people wanna style it, they can do it however they want from their copy of the component. Or they can “force” the styles in, meaning you have complete freedom.

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