first stab at inline SSR TeX

Author: Fil

docs/tex.md

@@ -48,3 +48,13 @@ c = \pm\sqrt{a^2 + b^2}
     \f\hat\xi\,e^{2 \pi i \xi x}
     \,d\xi
 ```
+
+When possible, a ${tex`\TeX`} expression is compiled server-side, for faster rendering; however, when it uses variables, it needs to load the katex library, and to be compiled client-side:
+
+```js
+const a = view(Inputs.range([0, 5], {step: 1}));
+```
+
+```tex show
+\int_0^1 x^${a}dx = \frac1${a + 1}
+```

package.json

@@ -36,6 +36,7 @@
     "fast-deep-equal": "^3.1.3",
     "gray-matter": "^4.0.3",
     "highlight.js": "^11.8.0",
+    "katex": "^0.16.9",
     "linkedom": "^0.15.6",
     "markdown-it": "^13.0.2",
     "markdown-it-anchor": "^8.6.7",

public/client.js

@@ -161,6 +161,7 @@ async function mermaid() {
 
 export function define(cell) {
   const {id, inline, inputs = [], outputs = [], files = [], databases = [], body} = cell;
+  if (body === undefined) return;
   const variables = [];
   cellsById.get(id)?.variables.forEach((v) => v.delete());
   cellsById.set(id, {cell, variables});

src/markdown.ts

@@ -4,6 +4,7 @@ import {type Patch, type PatchItem, getPatch} from "fast-array-diff";
 import equal from "fast-deep-equal";
 import matter from "gray-matter";
 import hljs from "highlight.js";
+import katex from "katex";
 import {parseHTML} from "linkedom";
 import MarkdownIt from "markdown-it";
 import {type RuleCore} from "markdown-it/lib/parser_core.js";
@@ -79,18 +80,32 @@ function uniqueCodeId(context: ParseContext, content: string): string {
   return id;
 }
 
-function getLiveSource(content, language, option) {
+function getLiveSource(content, language, option): {source?: string; html?: string} {
   return option === "no-run"
-    ? undefined
+    ? {}
     : language === "js"
-    ? content
+    ? {source: content}
     : language === "tex"
-    ? transpileTag(content, "tex.block", true)
+    ? maybeStaticTeX(content, true)
     : language === "dot"
-    ? transpileTag(content, "dot", false)
+    ? {source: transpileTag(content, "dot", false)}
     : language === "mermaid"
-    ? transpileTag(content, "await mermaid", false)
-    : undefined;
+    ? {source: transpileTag(content, "await mermaid", false)}
+    : {};
+}
+
+function maybeStaticTeX(content, displayMode) {
+  try {
+    // TODO smarter detection of ${} contents
+    // TODO smarter insertion of the TeX stylesheet
+    return {
+      html:
+        katex.renderToString(content, {displayMode}) +
+        `<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/katex/dist/katex.min.css">`
+    };
+  } catch {
+    return {source: transpileTag(content, displayMode ? "tex.block" : "tex", true)};
+  }
 }
 
 function makeFenceRenderer(root: string, baseRenderer: RenderRule, sourcePath: string): RenderRule {
@@ -99,7 +114,7 @@ function makeFenceRenderer(root: string, baseRenderer: RenderRule, sourcePath: s
     const [language, option] = token.info.split(" ");
     let result = "";
     let count = 0;
-    const source = getLiveSource(token.content, language, option);
+    const {source, html} = getLiveSource(token.content, language, option);
     if (source != null) {
       const id = uniqueCodeId(context, token.content);
       const sourceLine = context.startLine + context.currentLine;
@@ -115,6 +130,7 @@ function makeFenceRenderer(root: string, baseRenderer: RenderRule, sourcePath: s
       result += `<div id="cell-${id}" class="observablehq observablehq--block"></div>\n`;
       count++;
     }
+    if (html !== undefined) result += html;
     if (source == null || option === "show") {
       result += baseRenderer(tokens, idx, options, context, self);
       count++;
@@ -258,6 +274,13 @@ function makePlaceholderRenderer(root: string, sourcePath: string): RenderRule {
   return (tokens, idx, options, context: ParseContext) => {
     const id = uniqueCodeId(context, tokens[idx].content);
     const token = tokens[idx];
+
+    // inline TeX?
+    if (token.content.match(/^tex[`]/)) {
+      const {html} = maybeStaticTeX(token.content.slice(4, -1), false);
+      if (html !== undefined) return `<span id="cell-${id}">${html}</span>`;
+    }
+
     const transpile = transpileJavaScript(token.content, {
       id,
       root,

yarn.lock

@@ -654,6 +654,11 @@ commander@7:
   resolved "https://registry.yarnpkg.com/commander/-/commander-7.2.0.tgz#a36cb57d0b501ce108e4d20559a150a391d97ab7"
   integrity sha512-QrWXB+ZQSVPmIWIhtEO9H+gwHaMGYiF5ChvoJ+K9ZGHG/sVsa6yiesAD1GC/x46sET00Xlwo1u49RVVVzvcSkw==
 
+commander@^8.3.0:
+  version "8.3.0"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-8.3.0.tgz#4837ea1b2da67b9c616a67afbb0fafee567bca66"
+  integrity sha512-OkTL9umf+He2DZkUq8f8J9of7yL6RJKI24dVITBmNfZBmri9zYZQrKkuXiKhyfPSu8tUhnVBB1iKXevvnlR4Ww==
+
 [email protected]:
   version "0.0.1"
   resolved "https://registry.yarnpkg.com/concat-map/-/concat-map-0.0.1.tgz#d8a96bd77fd68df7793a73036a3ba0d5405d477b"
@@ -1794,6 +1799,13 @@ json5@^1.0.2:
   dependencies:
     minimist "^1.2.0"
 
+katex@^0.16.9:
+  version "0.16.9"
+  resolved "https://registry.yarnpkg.com/katex/-/katex-0.16.9.tgz#bc62d8f7abfea6e181250f85a56e4ef292dcb1fa"
+  integrity sha512-fsSYjWS0EEOwvy81j3vRA8TEAhQhKiqO+FQaKWp0m39qwOzHVBgAUBIXWj1pB+O2W3fIpNa6Y9KSKCVbfPhyAQ==
+  dependencies:
+    commander "^8.3.0"
+
 keyv@^4.5.3:
   version "4.5.4"
   resolved "https://registry.yarnpkg.com/keyv/-/keyv-4.5.4.tgz#a879a99e29452f942439f2a405e3af8b31d4de93"