Font Awesome is not working in my shadow DOM since I have the following in it to prevent styles from leaking in and out:
:host {
all: initial; /* 1st rule so subsequent properties are reset. */
display: block;
contain: content; /* Boom. CSS containment FTW. */
}
I'm able to use other stylesheets by just inlining them within the :host property, but that doesn't work with Font Awesome since it uses relative paths in its stylesheet.
I found this post and tried it with the scoped CSS I implement, but the icons show as squares, as can be seen in my example.
I had the same issue with StencilJS. After hours of struggle and the answer from @Intervalia I was able to fix it.
The problem is that the browser doesn't load the fonts when they are only included in the shadow dom (your custom web component). This means that the fonts must also be included in the normal html file (aka light DOM) so that the browser can load them and use them in the shadow dom.
In my case I didn't use Font awesome instead it was a custom font but I tried it a second time with font awesome and a clean Stenciljs project. The solution is always the same doesn't matter which custom font you need.
Step 1: Move the font into your project. I created a seperate "assets" folder inside the "src" folder to have access from all the components. In this example I downloaded font awesome for web environment https://fontawesome.com/download. (I wouldn't recommend "npm install" since you have to use it in the index.html too)
Step 2: Prepare your web component (in this case my-component.tsx). You can import multiple css files using the styleUrls property. Just import the fontawesome css from your assets directory.
import { Component, Prop, h } from '@stencil/core';
@Component({
tag: 'my-component',
styleUrls: [
'my-component.css',
'../../assets/fontawesome/css/all.css'
],
shadow: true
})
export class MyComponent {
@Prop() first: string;
render() {
return <div> <i class="fas fa-question-circle"></i> </div>;
}
}
Step 3 prepare the file where you want to use the component (in this case index.html). The important line is the "link" tag. This includes the "font awesome css" again and force the Browser to really download the fonts.
<!DOCTYPE html>
<html dir="ltr" lang="en">
<head>
<meta charset="utf-8">
<title>Stencil Component Starter</title>
<link rel="stylesheet" type="text/css" href="./assets/fontawesome/css/all.css">
</head>
<body>
<my-component first="Stencil" last="'Don't call me a framework' JS"></my-component>
</body>
</html>
I know it feels wrong and looks weird but it is not enough to include font awesome only in the index html or in the web component. It must really be included in both files. That doesn't mean the Browser will load it multiple times - it will only be loaded once.
That means that you can't deliver the font with the web component - as far as i know. This isn't a stenciljs bug this is a general problem of the browsers. Please let me know if you have better solutions.
Just for fun here is a screenshot that shows that the browser doesn't load the fonts when it is only included in one file. http://prntscr.com/p2f9tc
Update 05.10.2019:
If you want to use your font inside your web-component the explanation above is correct and still necessary. But you can also use the slot tag inside the web-component. Than you automatically bypass the font from outside (the html) into the web-component. But notice it only works for the stuff you write between the tags of your web component.
That means you can use <my-component> <i class="your-font"/> </my-component>. In this case you don't have to import the font into the web components.
One thing I have noticed is that if the page does not load the CSS file then the shadowDOM won't load it either.
I really think that the only problem us that if the font is not defined on the page that it will not work in the component since the rest of the CSS seems to properly apply to the shadowDOM elements.
This example shows just the shadowDOM trying to load the CSS and it does not work:
let template = `
<style>
:host {
display: block;
}
</style>
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.1/css/all.css" integrity="sha384-fnmOCqbTlWIlj8LyTjo7mOUStjsKC4pOpQbqyi7RrhN7udi9RwhKkMHpvLbHG9Sr" crossorigin="anonymous">
<header>
<h1>DreamLine</h1>
<nav>
<ul>
<li><a href="#0">Tour</a></li>
<li><a href="#0">Blog</a></li>
<li><a href="#0">Contact</a></li>
<li><a href="#0">Error</a></li>
<li><a href="#0"><i class="fa fa-search"></i> Search</a></li>
</ul>
</nav>
</header>
`;
class MyEl extends HTMLElement {
connectedCallback() {
this.attachShadow({mode: 'open'}).innerHTML = template;
}
}
customElements.define("blog-header", MyEl);<i class="fa fa-battery-full" style="font-size: 45px;"></i>
<hr/>
<blog-header></blog-header>
<hr/>And this example shows both the page and the shadowDOM loading it and it works:
let template = `
<style>
:host {
display: block;
}
</style>
<header>
<h1>DreamLine</h1>
<nav>
<ul>
<li><a href="#0">Tour</a></li>
<li><a href="#0">Blog</a></li>
<li><a href="#0">Contact</a></li>
<li><a href="#0">Error</a></li>
<li><a href="#0"><i class="fa fa-search"></i> Search</a></li>
</ul>
</nav>
</header>
`;
class MyEl extends HTMLElement {
connectedCallback() {
const styles = document.querySelector('link[href*="fontawesome"]');
this.attachShadow({mode: 'open'}).innerHTML = template;
if (styles) {
this.shadowRoot.appendChild(styles.cloneNode());
}
}
}
customElements.define("blog-header", MyEl);<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.1/css/all.css" integrity="sha384-fnmOCqbTlWIlj8LyTjo7mOUStjsKC4pOpQbqyi7RrhN7udi9RwhKkMHpvLbHG9Sr" crossorigin="anonymous">
<i class="fa fa-battery-full" style="font-size: 45px;"></i>
<hr/>
<blog-header></blog-header>
<hr/>The code I like to use looks for the <link> tag I want in the body and then uses a clone of that tag inside the shadowDOM. This way my component is not out of sync. Yes, this can cause problems if the component was not expecting a change in the CSS but I find it works well for my projects.
来源：https://stackoverflow.com/questions/54546007/why-doesnt-font-awesome-work-in-my-shadow-dom