fix: re-render latex support

When a description changed, update the latex rendering.

Similar to voila-dashboards/voila#531

packages/solara-widget-manager/src/mathjax.ts

@@ -20,8 +20,10 @@ RegisterHTMLHandler(browserAdaptor());
 
 // Override dynamically generated fonts in favor
 // of our font css that is picked up by webpack.
+// @ts-ignore
 class emptyFont extends TeXFont {
-  readonly defaultFonts = {};
+  // @ts-ignore
+  static defaultFonts = {};
 }
 
 const chtml = new CHTML({
@@ -57,3 +59,19 @@ export function renderMathJax(): void {
     .updateDocument()
     .reset();
 }
+// this makes it compatible with the old MathJax
+// see https://github.com/voila-dashboards/voila/pull/531
+// @ts-ignore
+window.MathJax = {
+  Hub: {
+    // @ts-ignore
+    Queue: ([_ignore, _ignore2, node]) => {
+      html.findMath({ elements: [node] })
+        .compile()
+        .getMetrics()
+        .typeset()
+        .updateDocument()
+        .reset()
+    }
+  }
+}

tests/integration/latex_test.py

@@ -0,0 +1,21 @@
+import ipywidgets as widgets
+import playwright.sync_api
+from IPython.display import display
+
+
+def test_widget_latex_solara(solara_test, page_session: playwright.sync_api.Page, assert_solara_snapshot):
+    # we tried a FloatSlider before, but that seems to give unstable images (handle moves around randomly)
+    label = widgets.Label(value=r"$E \sim mc^2$")
+    label.add_class("test-class-latex")
+    display(label)
+
+    page_session.locator(".test-class-latex >> .mjx-c1D438").wait_for()
+    page_session.evaluate("document.fonts.ready")
+    page_session.wait_for_timeout(100)
+    assert_solara_snapshot(page_session.locator(".test-class-latex >> .MathJax").screenshot())
+    label.value = r"$\alpha$"
+    label.add_class("test-changed-class-latex")
+    page_session.locator(".test-changed-class-latex >> .mjx-c1D6FC").wait_for()
+    page_session.evaluate("document.fonts.ready")
+    page_session.wait_for_timeout(100)
+    assert_solara_snapshot(page_session.locator(".test-changed-class-latex >> .MathJax").screenshot(), postfix="-changed")