adopt-styles/readme.md

# Pull-Styles

A simple proof-of-concept implementation of a mechanism to pull outside styles
into a Shadow-DOM.

```html
<style>
	p { color: red }
</style>

<my-component>
	<template shadowrootmode="open">
		<adopt-styles adopt="all"></adopt-styles>
		<p>This paragraph is red</p>
	</template>
</my-component>
```

## Rationale

This is primarily meant as a simple proof-of-concept to show how this mechanism
could work as a solution to the [use-case](https://github.com/WICG/webcomponents/issues/909)
of authors wanting to let outside styling rules affect content inside a shadow
DOM.

The aim of this project is not to provide a full solution to the problem, but to
showcase how one possible solution could work and to allow playing around with
the concept in real-world projects.

## Usage

Putting the `<adopt-styles>` node inside a shadow root will search the document
for style sheets and adopt them into the shadow root. Changes in the document's
head that appear related to styles will trigger an update of the adopted styles.

Adding the `layer=` attribute to the `<adopt-styles>` node will wrap the adopted
rules in a layer of the given name.

(Not yet Implemented) Setting the `adopt=` attribute to a value other than
`"all"` will only adopt styles from the CSS layer of the given name.

## Notes

Due to this being a relatively "simple" javascript implementation, outside
selectors will simply be mirrored into the shadow DOM, but more complex
selectors like child selectors won't match elements across shadow DOM
boundaries.

## Planned Features:

- [x] Import `<link>` tags
- [x] Import `<style>` tags
- [x] Import into layer
- [x] Automatic updating
- [ ] Import from layer