From fc28de377611b62ef297b59ee854cbefdb7d3995 Mon Sep 17 00:00:00 2001
From: Samuel Seng <djsamseng@gmail.com>
Date: Sun, 29 Jan 2023 12:09:23 -0500
Subject: [PATCH] Fix race condition: Render last requested page

Test Plan: Copy into local project and quickly change
pages. Ensure that the correct page gets rendered.
---
 package.json                        | 1 +
 packages/react-pdf-js/src/index.tsx | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/package.json b/package.json
index 9a062b92..738bd9f3 100644
--- a/package.json
+++ b/package.json
@@ -22,6 +22,7 @@
     "trailingComma": "es5"
   },
   "devDependencies": {
+    "eslint": "^8.33.0",
     "prettier": "2.7.1",
     "turbo": "1.4.7",
     "typescript": "4.8.3"
diff --git a/packages/react-pdf-js/src/index.tsx b/packages/react-pdf-js/src/index.tsx
index d40239ce..933d3616 100644
--- a/packages/react-pdf-js/src/index.tsx
+++ b/packages/react-pdf-js/src/index.tsx
@@ -52,6 +52,7 @@ export const usePdf = ({
   const [pdfDocument, setPdfDocument] = useState<PDFDocumentProxy>();
   const [pdfPage, setPdfPage] = useState<PDFPageProxy>();
   const renderTask = useRef<PDFRenderTask | null>(null);
+  const lastPageRequestedRenderRef = useRef<PDFPageProxy | null>(null);
   const onDocumentLoadSuccessRef = useRef(onDocumentLoadSuccess);
   const onDocumentLoadFailRef = useRef(onDocumentLoadFail);
   const onPageLoadSuccessRef = useRef(onPageLoadSuccess);
@@ -137,6 +138,7 @@ export const usePdf = ({
 
       // if previous render isn't done yet, we cancel it
       if (renderTask.current) {
+        lastPageRequestedRenderRef.current = page;
         renderTask.current.cancel();
         return;
       }
@@ -158,7 +160,9 @@ export const usePdf = ({
           renderTask.current = null;
 
           if (reason && reason.name === 'RenderingCancelledException') {
-            drawPDF(page);
+            const lastPageRequestedRender = lastPageRequestedRenderRef.current ?? page;
+            lastPageRequestedRenderRef.current = null;
+            drawPDF(lastPageRequestedRender);
           } else if (isFunction(onPageRenderFailRef.current)) {
             onPageRenderFailRef.current();
           }