Add optional KaTeX support to markdown plugin (#5846)

* Add optional KaTeX support to the tiddlywiki/markdown plugin.

Uses the remarkable-katex plugin 1.1.8 by Brad Howes to enable KaTeX support if
the tiddlywiki/katex plugin is installed. Fixes #2984.

TESTED:

Created a test wiki with:
```
$ node tiddlywiki.js test --init markdowndemo
$ node tiddlywiki.js test --listen
```

* Verified markdown support works without the tiddlywiki/katex plugin enabled.
* Verified markdown support works with the tiddlywiki/katex plugin enabled.
* Verified KaTeX (both inline and blocks) work as expected when the
tiddlywiki/katex plugin is enabled.

* Mention remarkable-katex plugin usage in the readme Tiddler.

* Include the remarkable-katex license as a tiddler.

* Include the Remarkable license.

* Include unminified original source of remarkable-katex 1.1.8.

plugins/tiddlywiki/markdown/files/remarkable-katex-license.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2017 Brad Howes
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

plugins/tiddlywiki/markdown/files/remarkable-katex.js

@@ -0,0 +1,137 @@
+"use strict";
+
+/**
+ * Plugin for Remarkable Markdown processor which transforms $..$ and $$..$$ sequences into math HTML using the
+ * Katex package.
+ */
+const rkatex = (md, options) => {
+  const backslash = '\\';
+  const dollar = '$';
+  const opts = options || {};
+  const delimiter = opts.delimiter || dollar;
+  if (delimiter.length !== 1) { throw new Error('invalid delimiter'); }
+
+  const katex = require("katex");
+
+  /**
+   * Render the contents as KaTeX
+   */
+  const renderKatex = (source, displayMode) => katex.renderToString(source,
+                                                                    {displayMode: displayMode,
+                                                                     throwOnError: false});
+
+  /**
+   * Parse '$$' as a block. Based off of similar method in remarkable.
+   */
+  const parseBlockKatex = (state, startLine, endLine) => {
+    let haveEndMarker = false;
+    let pos = state.bMarks[startLine] + state.tShift[startLine];
+    let max = state.eMarks[startLine];
+
+    if (pos + 1 > max) { return false; }
+
+    const marker = state.src.charAt(pos);
+    if (marker !== delimiter) { return false; }
+
+    // scan marker length
+    let mem = pos;
+    pos = state.skipChars(pos, marker);
+    let len = pos - mem;
+
+    if (len !== 2) { return false; }
+
+    // search end of block
+    let nextLine = startLine;
+
+    for (;;) {
+      ++nextLine;
+      if (nextLine >= endLine) { break; }
+
+      pos = mem = state.bMarks[nextLine] + state.tShift[nextLine];
+      max = state.eMarks[nextLine];
+
+      if (pos < max && state.tShift[nextLine] < state.blkIndent) { break; }
+      if (state.src.charAt(pos) !== delimiter) { continue; }
+      if (state.tShift[nextLine] - state.blkIndent >= 4) { continue; }
+
+      pos = state.skipChars(pos, marker);
+      if (pos - mem < len) { continue; }
+
+      pos = state.skipSpaces(pos);
+      if (pos < max) { continue; }
+
+      haveEndMarker = true;
+      break;
+    }
+
+    // If a fence has heading spaces, they should be removed from its inner block
+    len = state.tShift[startLine];
+    state.line = nextLine + (haveEndMarker ? 1 : 0);
+    const content = state.getLines(startLine + 1, nextLine, len, true)
+            .replace(/[ \n]+/g, ' ')
+            .trim();
+
+    state.tokens.push({type: 'katex', params: null, content: content, lines: [startLine, state.line],
+                       level: state.level, block: true});
+    return true;
+  };
+
+  /**
+   * Look for '$' or '$$' spans in Markdown text. Based off of the 'fenced' parser in remarkable.
+   */
+  const parseInlineKatex = (state, silent) => {
+    const start = state.pos;
+    const max = state.posMax;
+    let pos = start;
+
+    // Unexpected starting character
+    if (state.src.charAt(pos) !== delimiter) { return false; }
+
+    ++pos;
+    while (pos < max && state.src.charAt(pos) === delimiter) { ++pos; }
+
+    // Capture the length of the starting delimiter -- closing one must match in size
+    const marker = state.src.slice(start, pos);
+    if (marker.length > 2) { return false; }
+
+    const spanStart = pos;
+    let escapedDepth = 0;
+    while (pos < max) {
+      const char = state.src.charAt(pos);
+      if (char === '{' && (pos == 0 || state.src.charAt(pos - 1) != backslash)) {
+        escapedDepth += 1;
+      } else if (char === '}' && (pos == 0 || state.src.charAt(pos - 1) != backslash)) {
+        escapedDepth -= 1;
+        if (escapedDepth < 0) { return false; }
+      } else if (char === delimiter && escapedDepth === 0) {
+        const matchStart = pos;
+        let matchEnd = pos + 1;
+        while (matchEnd < max && state.src.charAt(matchEnd) === delimiter) { ++matchEnd; }
+
+        if (matchEnd - matchStart === marker.length) {
+          if (!silent) {
+            const content = state.src.slice(spanStart, matchStart)
+                .replace(/[ \n]+/g, ' ')
+                .trim();
+            state.push({type: 'katex', content: content, block: marker.length > 1, level: state.level});
+          }
+          state.pos = matchEnd;
+          return true;
+        }
+      }
+      pos += 1;
+    }
+
+    if (!silent) { state.pending += marker; }
+    state.pos += marker.length;
+
+    return true;
+  };
+
+  md.inline.ruler.push('katex', parseInlineKatex, options);
+  md.block.ruler.push('katex', parseBlockKatex, options);
+  md.renderer.rules.katex = (tokens, idx) => renderKatex(tokens[idx].content, tokens[idx].block);
+  md.renderer.rules.katex.delimiter = delimiter;
+};
+
+module.exports = rkatex;

plugins/tiddlywiki/markdown/files/remarkable-katex.min.js

@@ -0,0 +1,20 @@
+"use strict";const rkatex=(md,options)=>{const backslash='\\';const dollar='$';const opts=options||{};const delimiter=opts.delimiter||dollar;if(delimiter.length!==1){throw new Error('invalid delimiter');}
+const katex=require("katex");const renderKatex=(source,displayMode)=>katex.renderToString(source,{displayMode:displayMode,throwOnError:false});const parseBlockKatex=(state,startLine,endLine)=>{let haveEndMarker=false;let pos=state.bMarks[startLine]+state.tShift[startLine];let max=state.eMarks[startLine];if(pos+1>max){return false;}
+const marker=state.src.charAt(pos);if(marker!==delimiter){return false;}
+let mem=pos;pos=state.skipChars(pos,marker);let len=pos-mem;if(len!==2){return false;}
+let nextLine=startLine;for(;;){++nextLine;if(nextLine>=endLine){break;}
+pos=mem=state.bMarks[nextLine]+state.tShift[nextLine];max=state.eMarks[nextLine];if(pos<max&&state.tShift[nextLine]<state.blkIndent){break;}
+if(state.src.charAt(pos)!==delimiter){continue;}
+if(state.tShift[nextLine]-state.blkIndent>=4){continue;}
+pos=state.skipChars(pos,marker);if(pos-mem<len){continue;}
+pos=state.skipSpaces(pos);if(pos<max){continue;}
+haveEndMarker=true;break;}
+len=state.tShift[startLine];state.line=nextLine+(haveEndMarker?1:0);const content=state.getLines(startLine+1,nextLine,len,true).replace(/[ \n]+/g,' ').trim();state.tokens.push({type:'katex',params:null,content:content,lines:[startLine,state.line],level:state.level,block:true});return true;};const parseInlineKatex=(state,silent)=>{const start=state.pos;const max=state.posMax;let pos=start;if(state.src.charAt(pos)!==delimiter){return false;}
+++pos;while(pos<max&&state.src.charAt(pos)===delimiter){++pos;}
+const marker=state.src.slice(start,pos);if(marker.length>2){return false;}
+const spanStart=pos;let escapedDepth=0;while(pos<max){const char=state.src.charAt(pos);if(char==='{'&&(pos==0||state.src.charAt(pos-1)!=backslash)){escapedDepth+=1;}else if(char==='}'&&(pos==0||state.src.charAt(pos-1)!=backslash)){escapedDepth-=1;if(escapedDepth<0){return false;}}else if(char===delimiter&&escapedDepth===0){const matchStart=pos;let matchEnd=pos+1;while(matchEnd<max&&state.src.charAt(matchEnd)===delimiter){++matchEnd;}
+if(matchEnd-matchStart===marker.length){if(!silent){const content=state.src.slice(spanStart,matchStart).replace(/[ \n]+/g,' ').trim();state.push({type:'katex',content:content,block:marker.length>1,level:state.level});}
+state.pos=matchEnd;return true;}}
+pos+=1;}
+if(!silent){state.pending+=marker;}
+state.pos+=marker.length;return true;};md.inline.ruler.push('katex',parseInlineKatex,options);md.block.ruler.push('katex',parseBlockKatex,options);md.renderer.rules.katex=(tokens,idx)=>renderKatex(tokens[idx].content,tokens[idx].block);md.renderer.rules.katex.delimiter=delimiter;};module.exports=rkatex;

plugins/tiddlywiki/markdown/files/remarkable-license.txt

@@ -0,0 +1,22 @@
+The MIT License (MIT)
+
+Copyright (c) 2014-2016, Jon Schlinkert
+Copyright (c) 2014 Jon Schlinkert, Vitaly Puzrin.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

plugins/tiddlywiki/markdown/files/tiddlywiki.files

@@ -7,6 +7,30 @@
 				"title": "$:/plugins/tiddlywiki/markdown/remarkable.js",
 				"module-type": "library"
 			}
+		},
+		{
+			"file": "remarkable-license.txt",
+			"fields": {
+				"type": "text/plain",
+				"title": "$:/plugins/tiddlywiki/markdown/remarkable-license"
+			}
+		},
+		{
+			"file": "remarkable-katex.min.js",
+			"fields": {
+				"type": "application/javascript",
+				"title": "$:/plugins/tiddlywiki/markdown/remarkable-katex.js",
+				"module-type": "library"
+			},
+			"prefix": "(function(realRequire) {var require = function(m) {if(m===\"katex\"){m = \"$:/plugins/tiddlywiki/katex/katex.min.js\"};return realRequire(m);};",
+			"suffix": "})(require);\n"
+		},
+		{
+			"file": "remarkable-katex-license.txt",
+			"fields": {
+				"type": "text/plain",
+				"title": "$:/plugins/tiddlywiki/markdown/remarkable-katex-license"
+			}
 		}
 	]
 }

plugins/tiddlywiki/markdown/plugin.info

@@ -1,6 +1,6 @@
 {
 	"title": "$:/plugins/tiddlywiki/markdown",
 	"name": "Markdown",
-	"description": "Markdown parser based on remarkable by Jon Schlinkert",
+	"description": "Markdown parser based on remarkable by Jon Schlinkert and remarkable-katex by Brad Howes",
-	"list": "readme usage"
+	"list": "readme usage remarkable-license remarkable-katex-license"
 }

plugins/tiddlywiki/markdown/readme.tid

@@ -1,6 +1,6 @@
 title: $:/plugins/tiddlywiki/markdown/readme
 
-This is a TiddlyWiki plugin for parsing Markdown text, using the [[Remarkable|https://github.com/jonschlinkert/remarkable]] library.
+This is a TiddlyWiki plugin for parsing Markdown text, using the [[Remarkable|https://github.com/jonschlinkert/remarkable]] library. If the KaTeX TiddlyWiki plugin is installed, KaTeX support is enabled using the [[remarkable-katex|https://github.com/bradhowes/remarkable-katex]] Remarkable plugin.
 
 It is completely self-contained, and doesn't need an Internet connection in order to work. It works both in the browser and under Node.js.
 

plugins/tiddlywiki/markdown/wrapper.js

@@ -39,6 +39,12 @@ var accumulatingTypes = {
 
 var md = new Remarkable(remarkableOpts);
 
+// If tiddlywiki/katex plugin is present, use remarkable-katex to enable katex support.
+if ($tw.modules.titles["$:/plugins/tiddlywiki/katex/katex.min.js"]) {
+	var rk = require("$:/plugins/tiddlywiki/markdown/remarkable-katex.js");
+	md = md.use(rk);
+}
+
 if (parseAsBoolean("$:/config/markdown/linkify")) {
 	md = md.use(linkify);
 }
@@ -223,6 +229,16 @@ function convertNodes(remarkableTree, isStartOfInline) {
 			accumulatedText = accumulatedText + currentNode.content;
 			break;
 
+		case "katex":
+			out.push({
+				type: "latex",
+				attributes: {
+					text: { type: "text", value: currentNode.content },
+					displayMode: { type: "text", value: currentNode.block ? "true" : "false" }
+				}
+			});
+			break;
+
 		default:
 			if (currentNode.type.substr(currentNode.type.length - 5) === "_open") {
 				var tagName = currentNode.type.substr(0, currentNode.type.length - 5);