Reddit_stylesheet_editor.user.js

// ==UserScript==
// @name        Reddit stylesheet editor
// @namespace   flying-sheep
// @description CodeMirror-based stylesheet editor for reddit mods
// @include     http://www.reddit.com/r/*/about/stylesheet/
// @version     1
// @require     https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/codemirror.min.js
// @require     https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/addon/hint/show-hint.min.js
// @require     https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/mode/css/css.min.js
// @require     https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/addon/hint/css-hint.js
// @resource    mainCSS      https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/codemirror.min.js
// @resource    themCSS      https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/theme/ambiance.min.css
// @resource    hintCSS      https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.0.0/addon/hint/show-hint.min.css
// @grant       GM_addStyle
// @grant       GM_getResourceText
// ==/UserScript==

// more stuff: https://cdnjs.com/libraries/codemirror
// docs: http://codemirror.net/doc/manual.html

try {

GM_addStyle(GM_getResourceText('mainCSS'))
GM_addStyle(GM_getResourceText('themCSS'))
GM_addStyle(GM_getResourceText('hintCSS'))

var textAreaID = 'stylesheet_contents'
var textArea = document.getElementById(textAreaID)
var myCodeMirror = CodeMirror.fromTextArea(textArea, {
	lineNumbers: true,
	gutter: true,
	mode: 'css',
	theme: 'ambiance',
	indentWithTabs: true,
})

} catch (e) {
	console.error(e)
}