From 906745de38d3b552e28910c9ce4ab88ef7f43ee5 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sat, 14 Jan 2023 23:15:15 +0100
Subject: [PATCH] [Regression] Avoid showing a black canvas during zooming with
 a `drawingDelay` set (PR 15812 follow-up)

After the changes in PR 15812 we'll now *intermittently* display completely black canvases during zooming. To reproduce this, try switching to wrapped-scrolling and zoom in/out very quickly using either the mouse-wheel or pinching.
---
 web/pdf_page_view.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/web/pdf_page_view.js b/web/pdf_page_view.js
index 082e332f8..fdc4ac819 100644
--- a/web/pdf_page_view.js
+++ b/web/pdf_page_view.js
@@ -1071,7 +1071,12 @@ class PDFPageView {
         renderCapability.resolve();
       },
       function (error) {
-        showCanvas();
+        // When zooming with a `drawingDelay` set, avoid temporarily showing
+        // a black canvas if rendering was cancelled before the `onContinue`-
+        // callback had been invoked at least once.
+        if (!(error instanceof RenderingCancelledException)) {
+          showCanvas();
+        }
         renderCapability.reject(error);
       }
     );