Add LaTeX / math input and rendering support (#345)

* Initial display support

* Use better colors for error in math parsing

* Parse math markdown

* Use proper jsx

* Better copy support

* use css var directly

* Remove console.debug call

* Lazy load math module

* Show fallback while katex is loading

src/util/markdown.js

@@ -140,4 +140,59 @@ const spoilerExtensionHtml = {
   },
 };
 
-export { inlineExtension, spoilerExtension, spoilerExtensionHtml };
+const mathExtensionHtml = {
+  enter: {
+    mathFlow() {
+      this.lineEndingIfNeeded();
+    },
+    mathFlowFenceMeta() {
+      this.buffer();
+    },
+    mathText() {
+      this.buffer();
+    },
+  },
+  exit: {
+    mathFlow() {
+      const value = this.encode(this.resume().replace(/(?:\r?\n|\r)$/, ''));
+      this.tag('<div data-mx-maths="');
+      this.tag(value);
+      this.tag('"><code>');
+      this.raw(value);
+      this.tag('</code></div>');
+      this.setData('mathFlowOpen');
+      this.setData('slurpOneLineEnding');
+    },
+    mathFlowFence() {
+      // After the first fence.
+      if (!this.getData('mathFlowOpen')) {
+        this.setData('mathFlowOpen', true);
+        this.setData('slurpOneLineEnding', true);
+        this.buffer();
+      }
+    },
+    mathFlowFenceMeta() {
+      this.resume();
+    },
+    mathFlowValue(token) {
+      this.raw(this.sliceSerialize(token));
+    },
+    mathText() {
+      const value = this.encode(this.resume());
+      this.tag('<span data-mx-maths="');
+      this.tag(value);
+      this.tag('"><code>');
+      this.raw(value);
+      this.tag('</code></span>');
+    },
+    mathTextData(token) {
+      this.raw(this.sliceSerialize(token));
+    },
+  },
+};
+
+export {
+  inlineExtension,
+  spoilerExtension, spoilerExtensionHtml,
+  mathExtensionHtml,
+};