From c6d71e58b73b05fcc771ba6a457c941667bdac65 Mon Sep 17 00:00:00 2001
From: claude <claude@verso>
Date: Fri, 19 Jun 2026 14:52:49 +0000
Subject: [PATCH] fix(typst-preview): fix recursive Rust aliasing error and
 stale renders
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Two bugs fixed:

1. 'recursive use of an object' Rust error: inside runWithSession(), calling
   renderer.renderToSvg({ renderSession: session }) passes the session to the
   renderer while runWithSession already holds it — double-aliasing the same
   Rust object. Fixed by using session.renderToSvg({ container }) directly.

2. Stale preview after edits: concurrent doRender calls (compile finishes
   while previous render is still in progress) would both enter runWithSession
   simultaneously, causing the Rust error and leaving the view frozen. Fixed
   with a render guard (isRenderingRef) that queues the latest vectorData and
   flushes it once the current render completes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../components/typst-wasm-preview.tsx         | 53 ++++++++++++++-----
 1 file changed, 41 insertions(+), 12 deletions(-)

diff --git a/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx b/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx
index b3c0a5dada..aab70b3dc5 100644
--- a/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx
+++ b/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx
@@ -39,8 +39,12 @@ const TypstWasmPreview: FC = () => {
   const rendererRef = useRef<TypstRenderer | null>(null)
   const isReadyRef = useRef(false)
   const compileTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
-  // If 'compiled' arrives before renderer is ready, buffer the vector data
+  // If 'compiled' arrives before renderer is ready, buffer the latest vector data
   const pendingVectorRef = useRef<Uint8Array | null>(null)
+  // Prevent concurrent runWithSession calls which cause Rust aliasing errors
+  const isRenderingRef = useRef(false)
+  // Latest pending render while one is in progress
+  const renderQueueRef = useRef<Uint8Array | null>(null)
 
   const [status, setStatus] = useState<Status>('initializing')
   const [errorMsg, setErrorMsg] = useState('')
@@ -52,17 +56,42 @@ const TypstWasmPreview: FC = () => {
       pendingVectorRef.current = vectorData
       return
     }
-    try {
-      await renderer.runWithSession(async session => {
-        session.manipulateData({ action: 'reset', data: vectorData })
-        await renderer.renderToSvg({ renderSession: session, container })
-      })
-      pendingVectorRef.current = null
-      setStatus('ready')
-      setErrorMsg('')
-    } catch (e) {
-      setStatus('error')
-      setErrorMsg(`Render failed: ${e}`)
+
+    // If a render is in progress, queue this data and return —
+    // the in-progress render will pick it up when it finishes
+    if (isRenderingRef.current) {
+      renderQueueRef.current = vectorData
+      return
+    }
+
+    let dataToRender: Uint8Array | null = vectorData
+    while (dataToRender) {
+      isRenderingRef.current = true
+      const data = dataToRender
+      dataToRender = null
+
+      try {
+        await renderer.runWithSession(async session => {
+          session.manipulateData({ action: 'reset', data })
+          // Use session.renderToSvg (NOT renderer.renderToSvg with renderSession)
+          // to avoid double-aliasing the same Rust object inside runWithSession
+          await session.renderToSvg({ container })
+        })
+        pendingVectorRef.current = null
+        setStatus('ready')
+        setErrorMsg('')
+      } catch (e) {
+        setStatus('error')
+        setErrorMsg(`Render failed: ${e}`)
+      } finally {
+        isRenderingRef.current = false
+      }
+
+      // Pick up any compile result that arrived while we were rendering
+      if (renderQueueRef.current) {
+        dataToRender = renderQueueRef.current
+        renderQueueRef.current = null
+      }
     }
   }, [])