Error handling for KaTeX plugin

editions/katexdemo/tiddlers/HelloThere.tid

@@ -63,3 +63,14 @@ For more flexibility the KaTeX widget can also be used via the full widget synta
 ```
 
 <$latex text="\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi"></$latex>
+
+! Error Handling
+
+An warning message is displayed if KaTeX detects a problem with the ~LaTeX syntax. For example:
+
+```
+$$\displaystyle f(x) = \int_{-\infty}^\infinity\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$
+```
+
+$$\displaystyle f(x) = \int_{-\infty}^\infinity\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$
+

plugins/tiddlywiki/katex/wrapper.js

@@ -36,7 +36,12 @@ KaTeXWidget.prototype.render = function(parent,nextSibling) {
 	var text = this.getAttribute("text",this.parseTreeNode.text || "");
 	// Render it into a span
 	var span = this.document.createElement("span");
-	katex.render(text,span);
+	try {
+		katex.render(text,span);
+	} catch(ex) {
+		span.className = "tc-error";
+		span.textContent = ex;
+	}
 	// Insert it into the DOM
 	parent.insertBefore(span,nextSibling);
 	this.domNodes.push(span);