I am trying to make a semi-resuseable widget but I am running into a problem. I am trying to encapsulate a some CSS code inside a shadow root so that it does not affect the rest of the webpage but this CSS is used across multiple widgets so I am trying to include a remote stylesheet. None of the examples I have found use a remote style sheet and I was wondering if this was possible.
EX:
<template id="templateContent">
<head>
<link rel="stylesheet" href="css/generalStyle1.css">
</head>
<body>
<div class="affectedByGeneralStyle1"></div>
</body>
</template>
script to include template:
<div id="host"></div>
<script>
var importedData = (html_import_element).import.getElementById("templateContent");
var shadow = document.querySelector('#host').createShadowRoot();
var clone = document.importNode(importedData.content, true);
shadow.appendChild(clone);
</script>
i came across the same problem recently, what i ended up doing was using:
<template id="templateContent">
<style> @import "css/generalStyle.css"; </style>
</template>
additional info: this worked just fine except, now i'm having some cache issues as Chrome does not seem to reload those ressources after a hard reload.
Let add to the answer . Now direct tag is supported in shadow dom.
You can directly use
<link rel="stylesheet" href="yourcss1.css">
<link href="yourcss2.css" rel="stylesheet" type="text/css">
Check they has been update by whatwg and W3C
Useful link for using css in shadow dom.
https://w3c.github.io/webcomponents/spec/shadow/#inertness-of-html-elements-in-a-shadow-tree https://github.com/whatwg/html/commit/43c57866c2bbc20dc0deb15a721a28cbaad2140c
https://github.com/w3c/webcomponents/issues/628
Direct css link can be use in shadow dom
Thanks.
actually polymer has an internal utility to load css links, i have implemented a javascript function that is using polymer internal css processor,so if you want to add css links at runtime you can use it:
Polymer('my-element', {
ready: function () {
this.importCss("path/myfile.css");
},
importCss: function (path) {
var $shadow = $(this.shadowRoot);
var $head = $("<div></div>");
var $link = $("<link rel='stylesheet' type='text/css'>");
$link.attr("href", path);
$head.append($link);
var head = $head[0];
this.copySheetAttributes = Polymer.api.declaration.styles.copySheetAttributes;
Polymer.api.declaration.styles.convertSheetsToStyles.call(this, head);
var styles = Polymer.api.declaration.styles.findLoadableStyles(head);
if (styles.length) {
var templateUrl = this.baseURI;
Polymer.styleResolver.loadStyles(styles, templateUrl, function () {
var $style = $shadow.find("style");
if ($style.length > 0){
$shadow.find("style").append($head.find("style").html());
}else{
$shadow.append($head.html());
}
});
}
}
});
Note: this code needs jquery to run
I added the stylesheet's link element directly to the shadow root this way:
let link = document.createElement('link');
link.setAttribute('rel', 'stylesheet');
link.setAttribute('href', 'whatever.css');
this.shadowRoot.appendChild(link);
It seems to work fine. (I called this from the constructor of the component.)
