marked-element.html
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<!--
@license
Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->
<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="marked-import.html">
<!--
Element wrapper for the [marked](https://github.com/chjj/marked) library.
`<marked-element>` accepts Markdown source, and renders it to a child
element with the class `markdown-html`. This child element can be styled
as you would a normal DOM element. If you do not provide a child element
with the `markdown-html` class, the Markdown source will still be rendered,
but to a shadow DOM child that cannot be styled.
The Markdown source can be specified either via the `markdown` attribute:
<marked-element markdown="`Markdown` is _awesome_!">
<div class="markdown-html"></div>
</marked-element>
Or, you can provide it via a `<script type="text/markdown">` element child:
<marked-element>
<div class="markdown-html"></div>
<script type="text/markdown">
Check out my markdown!
We can even embed elements without fear of the HTML parser mucking up their
textual representation:
```html
<awesome-sauce>
<div>Oops, I'm about to forget to close this div.
</awesome-sauce>
```
</script>
</marked-element>
Note that the `<script type="text/markdown">` approach is _static_. Changes to
the script content will _not_ update the rendered markdown!
### Styling
If you are using a child with the `markdown-html` class, you can style it
as you would a regular DOM element:
.markdown-html p {
color: red;
}
.markdown-html td:first-child {
padding-left: 24px;
}
@element marked-element
@group Molecules
@hero hero.svg
@demo demo/index.html
-->
<dom-module id="marked-element">
<template>
<style>
/* Thanks IE 10. */
.hidden {
display: none !important;
}
</style>
<content select=".markdown-html"></content>
<div id="content" class="hidden"></div>
</template>
</dom-module>
<script>
'use strict';
Polymer({
is: 'marked-element',
properties: {
/** The markdown source that should be rendered by this element. */
markdown: {
observer: 'render',
type: String,
value: null
}
},
ready: function() {
if (!this.markdown) {
// Use the Markdown from the first `<script>` descendant whose MIME type starts with
// "text/markdown". Script elements beyond the first are ignored.
var markdownElement = Polymer.dom(this).querySelector('[type^="text/markdown"]');
if (markdownElement != null) {
this.markdown = this._unindent(markdownElement.textContent);
}
}
},
/**
* Renders `markdown` to HTML when the element is attached.
*
* This serves a dual purpose:
*
* * Prevents unnecessary work (no need to render when not visible).
*
* * `attached` fires top-down, so we can give ancestors a chance to
* register listeners for the `syntax-highlight` event _before_ we render
* any markdown.
*
*/
attached: function() {
this._attached = true;
this._outputElement = this.outputElement;
this.render();
},
detached: function() {
this._attached = false;
},
get outputElement () {
var child = Polymer.dom(this).queryDistributedElements('.markdown-html')[0];
if (child)
return child;
this.toggleClass('hidden', false, this.$.content);
return this.$.content;
},
/**
* Renders `markdown` into this element's DOM.
*
* This is automatically called whenever the `markdown` property is changed.
*
* The only case where you should be calling this is if you are providing
* markdown via `<script type="text/markdown">` after this element has been
* constructed (or updating that markdown).
*/
render: function() {
if (!this._attached) return;
if (!this.markdown) {
Polymer.dom(this._outputElement).innerHTML = '';
return;
}
Polymer.dom(this._outputElement).innerHTML = marked(this.markdown, {
highlight: this._highlight.bind(this),
});
},
_highlight: function(code, lang) {
var event = this.fire('syntax-highlight', {code: code, lang: lang});
return event.detail.code || code;
},
_unindent: function(text) {
if (!text) return text;
var lines = text.replace(/\t/g, ' ').split('\n');
var indent = lines.reduce(function(prev, line) {
if (/^\s*$/.test(line)) return prev; // Completely ignore blank lines.
var lineIndent = line.match(/^(\s*)/)[0].length;
if (prev === null) return lineIndent;
return lineIndent < prev ? lineIndent : prev;
}, null);
return lines.map(function(l) { return l.substr(indent); }).join('\n');
},
});
</script>