First pass at KaTeX plugin

Finally fixes #458 thanks to the KaTeX plugin from Khan Academy

editions/katexdemo/tiddlers/DefaultTiddlers.tid

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+title: $:/DefaultTiddlers
+
+HelloThere
+KaTeX
+ImplementationNotes

editions/katexdemo/tiddlers/HelloThere.tid

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+title: HelloThere
+
+This is a TiddlyWiki plugin for mathematical typesetting based on KaTeX from Khan Academy.
+
+! Installation
+
+To add the plugin to your own TiddlyWiki5, just drag this link to the browser window:
+
+[[$:/plugins/tiddlywiki/katex]]
+
+! Using KaTeX
+
+The KaTeX widget is provided under the name `<$latex>` and is also available under the alias `<$katex>`. It's better to use the generic `<$latex>` name unless you are running multiple LaTeX plugins and wish to specifically target KaTeX.
+
+! Examples
+
+These examples are taken from http://khan.github.io/KaTeX/
+
+!! Example 1
+
+```
+$$\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$
+```
+
+$$\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$
+
+!! Example 2
+
+```
+$$\displaystyle \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} = 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}} {1+\frac{e^{-8\pi}} {1+\cdots} } } }$$
+```
+
+$$\displaystyle \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} = 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}} {1+\frac{e^{-8\pi}} {1+\cdots} } } }$$
+
+!! Example 3
+
+```
+$$\displaystyle \left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$
+```
+
+$$\displaystyle \left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$
+
+!! Example 4
+
+```
+$$\displaystyle 1 +  \frac{q^2}{(1-q)}+\frac{q^6}{(1-q)(1-q^2)}+\cdots = \prod_{j=0}^{\infty}\frac{1}{(1-q^{5j+2})(1-q^{5j+3})}, \quad\quad \text{for }\lvert q\rvert<1.$$
+```
+
+$$\displaystyle 1 +  \frac{q^2}{(1-q)}+\frac{q^6}{(1-q)(1-q^2)}+\cdots = \prod_{j=0}^{\infty}\frac{1}{(1-q^{5j+2})(1-q^{5j+3})}, \quad\quad \text{for }\lvert q\rvert<1.$$
+
+!! Widget Example
+
+For more flexibility the KaTeX widget can also be used via the full widget syntax:
+
+```
+<$latex text="\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi"></$latex>
+```
+
+<$latex text="\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi"></$latex>

editions/katexdemo/tiddlers/ImplementationNotes.tid

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+title: ImplementationNotes
+
+! CSS Handling
+
+The [[original CSS from KaTeX|https://github.com/Khan/KaTeX/blob/master/static%2Ffonts.css]] includes a number of font definitions in this format:
+
+```
+@font-face {
+    font-family: 'KaTeX_AMS';
+    src: url('fonts/KaTeX_AMS-Regular.eot');
+    src: url('fonts/KaTeX_AMS-Regular.eot?#iefix') format('embedded-opentype'),
+         url('fonts/KaTeX_AMS-Regular.woff') format('woff'),
+         url('fonts/KaTeX_AMS-Regular.ttf') format('truetype');
+    font-weight: normal;
+    font-style: normal;
+}
+```
+
+These definitions are currently removed manually from [[$:/plugins/tiddlywiki/katex/katex.min.css]] so that they can be redefined as data URIs using TiddlyWiki's macro notation:
+
+```
+@font-face {
+    font-family: 'KaTeX_AMS';
+    src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_AMS-Regular.woff'>>) format('woff');
+    font-weight: normal;
+    font-style: normal;
+}
+```
+

editions/katexdemo/tiddlers/KaTeX.tid

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+title: KaTeX
+
+~KaTeX is a ~JavaScript library for mathematics typesetting from Khan Academy:
+
+http://khan.github.io/KaTeX/
+

editions/katexdemo/tiddlers/SiteSubtitle.tid

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+title: $:/SiteSubtitle
+
+a demo of the KaTeX plugin for TiddlyWiki5

editions/katexdemo/tiddlers/SiteTitle.tid

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+title: $:/SiteTitle
+
+KaTeX Demo

editions/katexdemo/tiddlywiki.info

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+{
+	"plugins": [
+		"tiddlywiki/katex"
+	],
+	"themes": [
+		"tiddlywiki/vanilla",
+		"tiddlywiki/snowwhite"
+	],
+	"includeWikis": [
+	],
+	"build": {
+		"index": [
+			"--rendertiddler","$:/core/save/all","katexdemo.html","text/plain"]
+	}
+}

plugins/tiddlywiki/katex/files/README.md

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+# [<img src="https://khan.github.io/KaTeX/katex-logo.svg" width="130" alt="KaTeX">](http://khan.github.io/KaTeX/) [![Build Status](https://travis-ci.org/Khan/KaTeX.svg?branch=master)](https://travis-ci.org/Khan/KaTeX)
+
+KaTeX is a fast, easy-to-use JavaScript library for TeX math rendering on the web.
+
+ * **Fast:** KaTeX renders its math synchronously and doesn't need to reflow the page. See how it compares to a competitor in [this speed test](http://jsperf.com/katex-vs-mathjax/).
+ * **Print quality:** KaTeX’s layout is based on Donald Knuth’s TeX, the gold standard for math typesetting.
+ * **Self contained:** KaTeX has no dependencies and can easily be bundled with your website resources.
+ * **Server side rendering:** KaTeX produces the same output regardless of browser or environment, so you can pre-render expressions using Node.js and send them as plain HTML.
+
+KaTeX supports all major browsers, including Chrome, Safari, Firefox, Opera, and IE 8 - IE 11.
+
+## Usage
+
+Download the built files from [the releases page](https://github.com/khan/katex/releases). Include the `katex.min.js` and `katex.min.css` files on your page:
+
+```html
+<link rel="stylesheet" type="text/css" href="/path/to/katex.min.css">
+<script src="/path/to/katex.min.js" type="text/javascript"></script>
+```
+
+Call `katex.render` with a TeX expression and a DOM element to render into:
+
+```js
+katex.render("c = \\pm\\sqrt{a^2 + b^2}", element);
+```
+
+To generate HTML on the server, you can use `katex.renderToString`:
+
+```js
+var html = katex.renderToString("c = \\pm\\sqrt{a^2 + b^2}");
+// '<span class="katex">...</span>'
+```
+
+Make sure to include the CSS and font files, but there is no need to include the JavaScript.
+
+## Contributing
+
+See [CONTRIBUTING.md](CONTRIBUTING.md)
+
+## License
+
+KaTeX is licenced under the [MIT License](http://opensource.org/licenses/MIT).

plugins/tiddlywiki/katex/files/tiddlywiki.files

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+{
+	"tiddlers": [
+		{
+			"file": "fonts/KaTeX_AMS-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_AMS-Regular.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Main-Bold.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Main-Bold.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Main-Italic.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Main-Italic.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Main-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Main-Regular.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Math-BoldItalic.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Math-BoldItalic.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Math-Italic.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Math-Italic.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Math-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Math-Regular.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Size1-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size1-Regular.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Size2-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size2-Regular.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Size3-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size3-Regular.woff"
+			}
+		},{
+			"file": "fonts/KaTeX_Size4-Regular.woff",
+			"fields": {
+				"type": "application/font-woff",
+				"title": "$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size4-Regular.woff"
+			}
+		},{
+			"file": "katex.without-font-face.min.css",
+			"fields": {
+				"type": "text/plain",
+				"title": "$:/plugins/tiddlywiki/katex/katex.min.css"
+			}
+		},{
+			"file": "katex.min.js",
+			"fields": {
+				"type": "application/javascript",
+				"title": "$:/plugins/tiddlywiki/katex/katex.min.js",
+				"module-type": "library"
+			}
+		}
+	]
+}

plugins/tiddlywiki/katex/latex-parser.js

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+/*\
+title: $:/plugins/tiddlywiki/katex/latex-parser.js
+type: application/javascript
+module-type: wikirule
+
+Wiki text inline rule for LaTeX. For example:
+
+```
+	$$latex-goes-here$$
+```
+
+This wikiparser can be modified using the rules eg:
+
+```
+\rules except latex-parser 
+\rules only latex-parser 
+```
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+exports.name = "latex-parser";
+exports.types = {inline: true};
+
+exports.init = function(parser) {
+	this.parser = parser;
+	// Regexp to match
+	this.matchRegExp = /\$\$(?!\$)/mg;
+};
+
+exports.parse = function() {
+	// Move past the match
+	this.parser.pos = this.matchRegExp.lastIndex;
+	var reEnd = /\$\$/mg;
+	// Look for the end marker
+	reEnd.lastIndex = this.parser.pos;
+	var match = reEnd.exec(this.parser.source),
+		text;
+	// Process the text
+	if(match) {
+		text = this.parser.source.substring(this.parser.pos,match.index);
+		this.parser.pos = match.index + match[0].length;
+	} else {
+		text = this.parser.source.substr(this.parser.pos);
+		this.parser.pos = this.parser.sourceLength;
+	}
+	return [{
+		type: "latex",
+		attributes: {
+			text: {
+				type: "text",
+				value: text
+			}}
+	}];
+};
+
+})();

plugins/tiddlywiki/katex/plugin.info

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+{
+	"title": "$:/plugins/tiddlywiki/katex",
+	"description": "Mathematics typesetting plugin wrapping KaTeX",
+	"author": "JeremyRuston"
+}

plugins/tiddlywiki/katex/styles.tid

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+title: $:/plugins/tiddlywiki/katex/styles
+tags: [[$:/tags/Stylesheet]]
+
+\rules only filteredtranscludeinline transcludeinline macrodef macrocallinline
+
+/* KaTeX styles */
+
+{{$:/plugins/tiddlywiki/katex/katex.min.css}}
+
+/* Override font URLs */
+
+@font-face {
+	font-family: 'KaTeX_AMS';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_AMS-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Caligraphic';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Caligraphic-Bold.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Caligraphic';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Caligraphic-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Fraktur';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Fraktur-Bold.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Fraktur';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Fraktur-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Greek';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Greek-Bold.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Greek';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Greek-BoldItalic.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: italic;
+}
+
+@font-face {
+	font-family: 'KaTeX_Greek';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Greek-Italic.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: italic;
+}
+
+@font-face {
+	font-family: 'KaTeX_Greek';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Greek-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Main';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Main-Bold.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Main';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Main-Italic.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: italic;
+}
+
+@font-face {
+	font-family: 'KaTeX_Main';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Main-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Math';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Math-BoldItalic.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: italic;
+}
+
+@font-face {
+	font-family: 'KaTeX_Math';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Math-Italic.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: italic;
+}
+
+@font-face {
+	font-family: 'KaTeX_Math';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Math-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_SansSerif';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_SansSerif-Bold.woff'>>) format('woff');
+	font-weight: bold;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_SansSerif';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_SansSerif-Italic.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: italic;
+}
+
+@font-face {
+	font-family: 'KaTeX_SansSerif';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_SansSerif-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Script';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Script-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Size1';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size1-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Size2';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size2-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Size3';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size3-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Size4';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Size4-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}
+
+@font-face {
+	font-family: 'KaTeX_Typewriter';
+	src: url(<<datauri '$:/plugins/tiddlywiki/katex/fonts/KaTeX_Typewriter-Regular.woff'>>) format('woff');
+	font-weight: normal;
+	font-style: normal;
+}

plugins/tiddlywiki/katex/wrapper.js

@@ -0,0 +1,69 @@
+/*\
+title: $:/plugins/tiddlywiki/katex/wrapper.js
+type: application/javascript
+module-type: widget
+
+Wrapper for `katex.min.js` that provides a `<$latex>` widget. It is also available under the alias `<$katex>`
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var katex = require("$:/plugins/tiddlywiki/katex/katex.min.js"),
+	Widget = require("$:/core/modules/widgets/widget.js").widget;
+
+var KaTeXWidget = function(parseTreeNode,options) {
+	this.initialise(parseTreeNode,options);
+};
+
+/*
+Inherit from the base widget class
+*/
+KaTeXWidget.prototype = new Widget();
+
+/*
+Render this widget into the DOM
+*/
+KaTeXWidget.prototype.render = function(parent,nextSibling) {
+	// Housekeeping
+	this.parentDomNode = parent;
+	this.computeAttributes();
+	this.execute();
+	// Get the source text
+	var text = this.getAttribute("text",this.parseTreeNode.text || "");
+	// Render it into a span
+	var span = this.document.createElement("span");
+	katex.render(text,span);
+	// Insert it into the DOM
+	parent.insertBefore(span,nextSibling);
+	this.domNodes.push(span);
+};
+
+/*
+Compute the internal state of the widget
+*/
+KaTeXWidget.prototype.execute = function() {
+	// Nothing to do for a katex widget
+};
+
+/*
+Selectively refreshes the widget if needed. Returns true if the widget or any of its children needed re-rendering
+*/
+KaTeXWidget.prototype.refresh = function(changedTiddlers) {
+	var changedAttributes = this.computeAttributes();
+	if(changedAttributes.text) {
+		this.refreshSelf();
+		return true;
+	} else {
+		return false;	
+	}
+};
+
+exports.latex = KaTeXWidget;
+exports.katex = KaTeXWidget;
+
+})();
+