From 084017a67319a993d73c6bdf612dd8532f1b8dbe Mon Sep 17 00:00:00 2001
From: Niklas von Hertzen <niklasvh@gmail.com>
Date: Mon, 12 Jul 2021 19:09:57 +0800
Subject: [PATCH] fix: crash on background-size with calc() (fix #2469) (#2569)

---
 src/render/background.ts            | 4 ++++
 tests/reftests/background/size.html | 1 +
 2 files changed, 5 insertions(+)

diff --git a/src/render/background.ts b/src/render/background.ts
index 3fed4d3..6e0e877 100644
--- a/src/render/background.ts
+++ b/src/render/background.ts
@@ -91,6 +91,10 @@ export const calculateBackgroundSize = (
 ): [number, number] => {
     const [first, second] = size;
 
+    if (!first) {
+        return [0, 0];
+    }
+
     if (isLengthPercentage(first) && second && isLengthPercentage(second)) {
         return [getAbsoluteValue(first, bounds.width), getAbsoluteValue(second, bounds.height)];
     }
diff --git a/tests/reftests/background/size.html b/tests/reftests/background/size.html
index d551136..48b7463 100644
--- a/tests/reftests/background/size.html
+++ b/tests/reftests/background/size.html
@@ -61,6 +61,7 @@
     <div style='background-size: auto;'></div>
 </div>
 <div class="container" style="padding: 10px; background-size: contain; background-origin: content-box; background-clip: content-box"></div>
+<div class="container" style="background-size: calc(100% - 10px)"></div>
 <div class="sliver">
     <div></div>
 </div>