如何让导入的css对阴影dom中的元素产生影响？ [英] How to let imported css have effects on elements in the shadow dom?

问题描述

假设我想使用阴影dom创建自定义元素。模板中的某些元素具有在链接的css文件中指定的类名。现在我想让css规则对元素产生影响。但由于影子dom样式边界，我无法实现这一点。

Say if I want to create a custom element using shadow dom. Some elements in the template have class names specified in the linked css file. Now I want to let the css rules have effects on the elements. But I can't achieve that because of the shadow dom style boundary.

<link rel="stylesheet" type="text/css" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">
<template id="blog-header">
	<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>
</template>
<script type="text/javascript">
	var importDoc = document.currentScript.ownerDocument;
	var proto = Object.create(HTMLElement.prototype, {
		createdCallback: {
			value: function() {
				var t = importDoc.querySelector("#blog-header");
				var clone = document.importNode(t.content, true);
				this.createShadowRoot().appendChild(clone);
			}
		}
	});
	document.registerElement("blog-header", {prototype: proto});
</script>

你看， fa-search 是一个在font-awesome css文件中定义的类，我如何设置< i> 元素？

You see, fa-search is a class defined in the font-awesome css file, how can I style the <i> element?

推荐答案

使用导入的字体（即 FontAwesome ）在Shadow DOM中，您应该：

To use an imported font (i.e. FontAwesome) in a Shadow DOM, you should:

1°声明字体

首先，在主文档中包含< link rel =stylesheet> 元素。它将声明一个 @ font-face CSS规则，该字体将使该字体可用于文档中的所有文本。

First, include the <link rel="stylesheet"> element in the main document. It will declare a @font-face CSS rule that will make the font available for all the text in the document.

2°导入样式表

然后，使用 @import url导入相同的文件 < template> 节点中的CSS规则，以使 .fa - * 类选择器可用于Shadow DOM：

Then, import the same file with an @import url CSS rule in the <template> node to make the .fa-* classes selectors available from the Shadow DOM :

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">

<template id="blog-header">
  <style>
    @import url("https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css")
  </style>
  <header>
    <h1>DreamLine</h1>
    //...
  </header>
</template>

var importDoc = document.currentScript.ownerDocument;
var proto = Object.create(HTMLElement.prototype, {
	createdCallback: {
		value: function() {
			var t = importDoc.querySelector("#blog-header");
			var clone = document.importNode(t.content, true);
			this.createShadowRoot().appendChild(clone);
		}
	}
});
document.registerElement("blog-header", {prototype: proto});

/* 
@font-face {
    font-family: "FontAwesome";
    src: url("https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome-webfont.woff2?v=4.5.0") format('woff2');
  }
*/

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">

<template id="blog-header">
  <style>
    @import url("https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css")
  </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>
</template>

<blog-header></blog-header>

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