prism-line-highlight.js

(function () {

	if (typeof self === 'undefined' || !self.Prism || !self.document || !document.querySelector) {
		return;
	}

	function $$(expr, con) {
		return Array.prototype.slice.call((con || document).querySelectorAll(expr));
	}

	function hasClass(element, className) {
		className = " " + className + " ";
		return (" " + element.className + " ").replace(/[\n\t]/g, " ").indexOf(className) > -1
	}

	function callFunction(func) {
		func();
	}

	// Some browsers round the line-height, others don't.
	// We need to test for it to position the elements properly.
	var isLineHeightRounded = (function () {
		var res;
		return function () {
			if (typeof res === 'undefined') {
				var d = document.createElement('div');
				d.style.fontSize = '13px';
				d.style.lineHeight = '1.5';
				d.style.padding = '0';
				d.style.border = '0';
				d.innerHTML = '&nbsp;<br />&nbsp;';
				document.body.appendChild(d);
				// Browsers that round the line-height should have offsetHeight === 38
				// The others should have 39.
				res = d.offsetHeight === 38;
				document.body.removeChild(d);
			}
			return res;
		}
	}());

	/**
	 * Returns the top offset of the content box of the given parent and the content box of one of its children.
	 *
	 * @param {HTMLElement} parent
	 * @param {HTMLElement} child
	 */
	function getContentBoxTopOffset(parent, child) {
		var parentStyle = getComputedStyle(parent);
		var childStyle = getComputedStyle(child);

		/**
		 * Returns the numeric value of the given pixel value.
		 *
		 * @param {string} px
		 */
		function pxToNumber(px) {
			return +px.substr(0, px.length - 2);
		}

		return child.offsetTop + pxToNumber(childStyle.borderTopWidth) + pxToNumber(childStyle.paddingTop)
			- pxToNumber(parentStyle.paddingTop);
	}

	/**
	 * Highlights the lines of the given pre.
	 *
	 * This function is split into a DOM measuring and mutate phase to improve performance.
	 * The returned function mutates the DOM when called.
	 *
	 * @param {HTMLElement} pre
	 * @param {string | null} [lines]
	 * @param {string} [classes='']
	 * @returns {() => void}
	 */
	function highlightLines(pre, lines, classes) {
		lines = typeof lines === 'string' ? lines : pre.getAttribute('data-line');

		var ranges = lines.replace(/\s+/g, '').split(',');
		var offset = Number(pre.getAttribute('data-line-offset'));

		var parseMethod = isLineHeightRounded() ? parseInt : parseFloat;
		var lineHeight = parseMethod(getComputedStyle(pre).lineHeight);
		var hasLineNumbers = hasClass(pre, 'line-numbers');
		var codeElement = pre.querySelector('code');
		var parentElement = hasLineNumbers ? pre : codeElement || pre;
		var mutateActions = /** @type {(() => void)[]} */ ([]);

		/**
		 * The top offset between the content box of the <code> element and the content box of the parent element of
		 * the line highlight element (either `<pre>` or `<code>`).
		 *
		 * This offset might not be zero for some themes where the <code> element has a top margin. Some plugins
		 * (or users) might also add element above the <code> element. Because the line highlight is aligned relative
		 * to the <pre> element, we have to take this into account.
		 *
		 * This offset will be 0 if the parent element of the line highlight element is the `<code>` element.
		 */
		var codePreOffset = !codeElement || parentElement == codeElement ? 0 : getContentBoxTopOffset(pre, codeElement);

		ranges.forEach(function (currentRange) {
			var range = currentRange.split('-');

			var start = +range[0];
			var end = +range[1] || start;

			/** @type {HTMLElement} */
			var line = pre.querySelector('.line-highlight[data-range="' + currentRange + '"]') || document.createElement('div');

			mutateActions.push(function () {
				line.setAttribute('aria-hidden', 'true');
				line.setAttribute('data-range', currentRange);
				line.className = (classes || '') + ' line-highlight';
			});

			// if the line-numbers plugin is enabled, then there is no reason for this plugin to display the line numbers
			if (hasLineNumbers && Prism.plugins.lineNumbers) {
				var startNode = Prism.plugins.lineNumbers.getLine(pre, start);
				var endNode = Prism.plugins.lineNumbers.getLine(pre, end);

				if (startNode) {
					var top = startNode.offsetTop + codePreOffset + 'px';
					mutateActions.push(function () {
						line.style.top = top;
					});
				}

				if (endNode) {
					var height = (endNode.offsetTop - startNode.offsetTop) + endNode.offsetHeight + 'px';
					mutateActions.push(function () {
						line.style.height = height;
					});
				}
			} else {
				mutateActions.push(function () {
					line.setAttribute('data-start', String(start));

					if (end > start) {
						line.setAttribute('data-end', String(end));
					}

					line.style.top = (start - offset - 1) * lineHeight + codePreOffset + 'px';

					line.textContent = new Array(end - start + 2).join(' \n');
				});
			}

			mutateActions.push(function () {
				// allow this to play nicely with the line-numbers plugin
				// need to attack to pre as when line-numbers is enabled, the code tag is relatively which screws up the positioning
				parentElement.appendChild(line);
			});
		});

		return function () {
			mutateActions.forEach(callFunction);
		};
	}

	function applyHash() {
		var hash = location.hash.slice(1);

		// Remove pre-existing temporary lines
		$$('.temporary.line-highlight').forEach(function (line) {
			line.parentNode.removeChild(line);
		});

		var range = (hash.match(/\.([\d,-]+)$/) || [, ''])[1];

		if (!range || document.getElementById(hash)) {
			return;
		}

		var id = hash.slice(0, hash.lastIndexOf('.')),
			pre = document.getElementById(id);

		if (!pre) {
			return;
		}

		if (!pre.hasAttribute('data-line')) {
			pre.setAttribute('data-line', '');
		}

		var mutateDom = highlightLines(pre, range, 'temporary ');
		mutateDom();

		document.querySelector('.temporary.line-highlight').scrollIntoView();
	}

	var fakeTimer = 0; // Hack to limit the number of times applyHash() runs

	Prism.hooks.add('before-sanity-check', function (env) {
		var pre = env.element.parentElement;
		var lines = pre && pre.getAttribute('data-line');

		if (!pre || !lines || !/pre/i.test(pre.nodeName)) {
			return;
		}

		/*
		 * Cleanup for other plugins (e.g. autoloader).
		 *
		 * Sometimes <code> blocks are highlighted multiple times. It is necessary
		 * to cleanup any left-over tags, because the whitespace inside of the <div>
		 * tags change the content of the <code> tag.
		 */
		var num = 0;
		$$('.line-highlight', pre).forEach(function (line) {
			num += line.textContent.length;
			line.parentNode.removeChild(line);
		});
		// Remove extra whitespace
		if (num && /^( \n)+$/.test(env.code.slice(-num))) {
			env.code = env.code.slice(0, -num);
		}
	});

	Prism.hooks.add('complete', function completeHook(env) {
		var pre = env.element.parentElement;
		var lines = pre && pre.getAttribute('data-line');

		if (!pre || !lines || !/pre/i.test(pre.nodeName)) {
			return;
		}

		clearTimeout(fakeTimer);

		var hasLineNumbers = Prism.plugins.lineNumbers;
		var isLineNumbersLoaded = env.plugins && env.plugins.lineNumbers;

		if (hasClass(pre, 'line-numbers') && hasLineNumbers && !isLineNumbersLoaded) {
			Prism.hooks.add('line-numbers', completeHook);
		} else {
			var mutateDom = highlightLines(pre, lines);
			mutateDom();
			fakeTimer = setTimeout(applyHash, 1);
		}
	});

	window.addEventListener('hashchange', applyHash);
	window.addEventListener('resize', function () {
		var actions = [];
		$$('pre[data-line]').forEach(function (pre) {
			actions.push(highlightLines(pre));
		});
		actions.forEach(callFunction);
	});

})();