From 7850b17a7d1044c844217db298f637fa252180ed Mon Sep 17 00:00:00 2001
From: Cameron Kaiser <classilla@floodgap.com>
Date: Sun, 14 Jun 2020 20:27:29 -0700
Subject: [PATCH] #612: M1019551

---
 dom/html/HTMLCanvasElement.cpp | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/dom/html/HTMLCanvasElement.cpp b/dom/html/HTMLCanvasElement.cpp
index 8de85ed2a..f7b287b00 100644
--- a/dom/html/HTMLCanvasElement.cpp
+++ b/dom/html/HTMLCanvasElement.cpp
@@ -545,17 +545,23 @@ HTMLCanvasElement::CopyInnerTo(Element* aDest)
     HTMLCanvasElement* dest = static_cast<HTMLCanvasElement*>(aDest);
     dest->mOriginalCanvas = this;
 
-    nsCOMPtr<nsISupports> cxt;
-    dest->GetContext(NS_LITERAL_STRING("2d"), getter_AddRefs(cxt));
-    RefPtr<CanvasRenderingContext2D> context2d =
-      static_cast<CanvasRenderingContext2D*>(cxt.get());
-    if (context2d && !mPrintCallback) {
-      CanvasImageSource source;
-      source.SetAsHTMLCanvasElement() = this;
-      ErrorResult err;
-      context2d->DrawImage(source,
-                           0.0, 0.0, err);
-      rv = err.StealNSResult();
+    // We make sure that the canvas is not zero sized since that would cause
+    // the DrawImage call below to return an error, which would cause printing
+    // to fail.
+    nsIntSize size = GetWidthHeight();
+    if (size.height > 0 && size.width > 0) {
+      nsCOMPtr<nsISupports> cxt;
+      dest->GetContext(NS_LITERAL_STRING("2d"), getter_AddRefs(cxt));
+      RefPtr<CanvasRenderingContext2D> context2d =
+        static_cast<CanvasRenderingContext2D*>(cxt.get());
+      if (context2d && !mPrintCallback) {
+        CanvasImageSource source;
+        source.SetAsHTMLCanvasElement() = this;
+        ErrorResult err;
+        context2d->DrawImage(source,
+                             0.0, 0.0, err);
+        rv = err.StealNSResult();
+      }
     }
   }
   return rv;