From f341d81ae843633c23710c28878bf1c830259eab Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Thu, 19 Nov 2015 12:31:49 +0100
Subject: [PATCH] Ensure that the `hidden` attribute is always removed from the
 canvas when rendering is complete (issue 6661)

Fixes 6661.
---
 web/pdf_page_view.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/web/pdf_page_view.js b/web/pdf_page_view.js
index 561ac8116..52b3f59df 100644
--- a/web/pdf_page_view.js
+++ b/web/pdf_page_view.js
@@ -308,7 +308,11 @@ var PDFPageView = (function PDFPageViewClosure() {
 
       var canvas = document.createElement('canvas');
       canvas.id = 'page' + this.id;
+      // Keep the canvas hidden until the first draw callback, or until drawing
+      // is complete when `!this.renderingQueue`, to prevent black flickering.
       canvas.setAttribute('hidden', 'hidden');
+      var isCanvasHidden = true;
+
       canvasWrapper.appendChild(canvas);
       if (this.annotationLayer && this.annotationLayer.div) {
         // annotationLayer needs to stay on top
@@ -316,7 +320,6 @@ var PDFPageView = (function PDFPageViewClosure() {
       } else {
         div.appendChild(canvasWrapper);
       }
-      var isCanvasHidden = true;
       this.canvas = canvas;
 
 //#if MOZCENTRAL || FIREFOX || GENERIC
@@ -401,6 +404,11 @@ var PDFPageView = (function PDFPageViewClosure() {
 
         self.renderingState = RenderingStates.FINISHED;
 
+        if (isCanvasHidden) {
+          self.canvas.removeAttribute('hidden');
+          isCanvasHidden = false;
+        }
+
         if (self.loadingIconDiv) {
           div.removeChild(self.loadingIconDiv);
           delete self.loadingIconDiv;