prism-line-highlight.js

(function () {

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

	var LINE_NUMBERS_CLASS = 'line-numbers';
	var LINKABLE_LINE_NUMBERS_CLASS = 'linkable-line-numbers';
	var NEW_LINE_EXP = /\n(?!$)/g;

	/**
	 * @param {string} selector
	 * @param {ParentNode} [container]
	 * @returns {HTMLElement[]}
	 */
	function $$(selector, container) {
		return Array.prototype.slice.call((container || document).querySelectorAll(selector));
	}

	/**
	 * Returns whether the given element has the given class.
	 *
	 * @param {Element} element
	 * @param {string} className
	 * @returns {boolean}
	 */
	function hasClass(element, className) {
		return element.classList.contains(className);
	}

	/**
	 * Calls the given function.
	 *
	 * @param {() => any} func
	 * @returns {void}
	 */
	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);
	}

	/**
	 * Returns whether the Line Highlight plugin is active for the given element.
	 *
	 * If this function returns `false`, do not call `highlightLines` for the given element.
	 *
	 * @param {HTMLElement | null | undefined} pre
	 * @returns {boolean}
	 */
	function isActiveFor(pre) {
		if (!pre || !/pre/i.test(pre.nodeName)) {
			return false;
		}

		if (pre.hasAttribute('data-line')) {
			return true;
		}

		if (pre.id && Prism.util.isActive(pre, LINKABLE_LINE_NUMBERS_CLASS)) {
			// Technically, the line numbers plugin is also necessary but this plugin doesn't control the classes of
			// the line numbers plugin, so we can't assume that they are present.
			return true;
		}

		return false;
	}

	var scrollIntoView = true;

	Prism.plugins.lineHighlight = {
		/**
		 * 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}
		 */
		highlightLines: function highlightLines(pre, lines, classes) {
			lines = typeof lines === 'string' ? lines : (pre.getAttribute('data-line') || '');

			var ranges = lines.replace(/\s+/g, '').split(',').filter(Boolean);
			var offset = +pre.getAttribute('data-line-offset') || 0;

			var parseMethod = isLineHeightRounded() ? parseInt : parseFloat;
			var lineHeight = parseMethod(getComputedStyle(pre).lineHeight);
			var hasLineNumbers = Prism.util.isActive(pre, LINE_NUMBERS_CLASS);
			var codeElement = pre.querySelector('code');
			var parentElement = hasLineNumbers ? pre : codeElement || pre;
			var mutateActions = /** @type {(() => void)[]} */ ([]);
			var lineBreakMatch = codeElement.textContent.match(NEW_LINE_EXP);
			var numberOfLines = lineBreakMatch ? lineBreakMatch.length + 1 : 1;
			/**
			 * 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;
				end = Math.min(numberOfLines + offset, end);

				if (end < start) {
					return;
				}

				/** @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 () {
					line.style.width = pre.scrollWidth + 'px';
				});

				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);
				});
			});

			var id = pre.id;
			if (hasLineNumbers && Prism.util.isActive(pre, LINKABLE_LINE_NUMBERS_CLASS) && id) {
				// This implements linkable line numbers. Linkable line numbers use Line Highlight to create a link to a
				// specific line. For this to work, the pre element has to:
				//  1) have line numbers,
				//  2) have the `linkable-line-numbers` class or an ascendant that has that class, and
				//  3) have an id.

				if (!hasClass(pre, LINKABLE_LINE_NUMBERS_CLASS)) {
					// add class to pre
					mutateActions.push(function () {
						pre.classList.add(LINKABLE_LINE_NUMBERS_CLASS);
					});
				}

				var start = parseInt(pre.getAttribute('data-start') || '1');

				// iterate all line number spans
				$$('.line-numbers-rows > span', pre).forEach(function (lineSpan, i) {
					var lineNumber = i + start;
					lineSpan.onclick = function () {
						var hash = id + '.' + lineNumber;

						// this will prevent scrolling since the span is obviously in view
						scrollIntoView = false;
						location.hash = hash;
						setTimeout(function () {
							scrollIntoView = true;
						}, 1);
					};
				});
			}

			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('.'));
		var pre = document.getElementById(id);

		if (!pre) {
			return;
		}

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

		var mutateDom = Prism.plugins.lineHighlight.highlightLines(pre, range, 'temporary ');
		mutateDom();

		if (scrollIntoView) {
			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;
		if (!isActiveFor(pre)) {
			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;
		if (!isActiveFor(pre)) {
			return;
		}

		clearTimeout(fakeTimer);

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

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

	window.addEventListener('hashchange', applyHash);
	window.addEventListener('resize', function () {
		var actions = $$('pre')
			.filter(isActiveFor)
			.map(function (pre) {
				return Prism.plugins.lineHighlight.highlightLines(pre);
			});
		actions.forEach(callFunction);
	});

}());