background-attachment

lea.verou.me/2012/04/background-attachment-local/

w3.org/TR/css3-background/#the-background-attachment

/**
 * Prism: Lightweight, robust, elegant syntax highlighting
 * MIT license http://www.opensource.org/licenses/mit-license.php/
 * @author Lea Verou http://lea.verou.me
 */

(function(){

// Private helper vars
var lang = /\blang(?:uage)?-(?!\*)(\w+)\b/i;

var _ = self.Prism = {
	highlightAll: function(async, callback) {
		var elements = document.querySelectorAll('code[class*="language-"], [class*="language-"] code, code[class*="lang-"], [class*="lang-"] code');

		for (var i=0, element; element = elements[i++];) {
			_.highlightElement(element, async === true, callback);
		}
	},
		
	highlightElement: function(element, async, callback) {
		// Find language
		var language, grammar, parent = element;
		
		while (parent && !lang.test(parent.className)) {
			parent = parent.parentNode;
		}
		
		if (parent) {
			language = (parent.className.match(lang) || [,''])[1];
			grammar = _.languages[language];
		}

		if (!grammar) {
			return;
		}
		
		// Set language on the element, if not present
		element.className = element.className.replace(lang, '').replace(/\s+/g, ' ') + ' language-' + language;
		
		// Set language on the parent, for styling
		parent = element.parentNode;
		
		if (/pre/i.test(parent.nodeName)) {
			parent.className = parent.className.replace(lang, '').replace(/\s+/g, ' ') + ' language-' + language; 
		}

		var code = element.textContent;
		
		if(!code) {
			return;
		}
		
		code = code.replace(/&/g, '&amp;').replace(/</g, '&lt;')
		           .replace(/>/g, '&gt;').replace(/\u00a0/g, ' ');
		//console.time(code.slice(0,50));
		
		var env = {
			element: element,
			language: language,
			grammar: grammar,
			code: code
		};
		
		_.hooks.run('before-highlight', env);
		
		if (async && self.Worker) {
			var worker = new Worker(_.filename);	
			
			worker.onmessage = function(evt) {
				env.highlightedCode = Token.stringify(JSON.parse(evt.data));
				env.element.innerHTML = env.highlightedCode;
				
				callback && callback.call(env.element);
				//console.timeEnd(code.slice(0,50));
				_.hooks.run('after-highlight', env);
			};
			
			worker.postMessage(JSON.stringify({
				language: env.language,
				code: env.code
			}));
		}
		else {
			env.highlightedCode = _.highlight(env.code, env.grammar)
			env.element.innerHTML = env.highlightedCode;
			
			callback && callback.call(element);
			
			_.hooks.run('after-highlight', env);
			//console.timeEnd(code.slice(0,50));
		}
	},
	
	highlight: function (text, grammar) {
		return Token.stringify(_.tokenize(text, grammar));
	},
	
	tokenize: function(text, grammar) {
		var Token = _.Token;
		
		var strarr = [text];
		
		var rest = grammar.rest;
		
		if (rest) {
			for (var token in rest) {
				grammar[token] = rest[token];
			}
			
			delete grammar.rest;
		}
								
		tokenloop: for (var token in grammar) {
			if(!grammar.hasOwnProperty(token) || !grammar[token]) {
				continue;
			}
			
			var pattern = grammar[token], 
				inside = pattern.inside,
				lookbehind = !!pattern.lookbehind || 0;
			
			pattern = pattern.pattern || pattern;
			
			for (var i=0; i<strarr.length; i++) { // Don’t cache length as it changes during the loop
				
				var str = strarr[i];
				
				if (strarr.length > text.length) {
					// Something went terribly wrong, ABORT, ABORT!
					break tokenloop;
				}
				
				if (str instanceof Token) {
					continue;
				}
				
				pattern.lastIndex = 0;
				
				var match = pattern.exec(str);
				
				if (match) {
					if(lookbehind) {
						lookbehind = match[1].length;
					}

					var from = match.index - 1 + lookbehind,
					    match = match[0].slice(lookbehind),
					    len = match.length,
					    to = from + len,
						before = str.slice(0, from + 1),
						after = str.slice(to + 1); 

					var args = [i, 1];
					
					if (before) {
						args.push(before);
					}
					
					var wrapped = new Token(token, inside? _.tokenize(match, inside) : match);
					
					args.push(wrapped);
					
					if (after) {
						args.push(after);
					}
					
					Array.prototype.splice.apply(strarr, args);
				}
			}
		}

		return strarr;
	}