From f34cc0b8e3517a278dbbecdad433ecf907df96cf Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 17 Aug 2023 08:46:38 +0200
Subject: [PATCH] LibWeb: Null check fonts after parsing them in CRC2D.font
 assignment

Fixes an issue where setting CRC2D.font to an unparseable value would
assert due to a null dereference.
---
 Tests/LibWeb/Text/expected/canvas/basic.txt           |  2 ++
 Tests/LibWeb/Text/input/canvas/basic.html             | 11 +++++++++++
 .../LibWeb/HTML/Canvas/CanvasTextDrawingStyles.h      |  2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 Tests/LibWeb/Text/expected/canvas/basic.txt
 create mode 100644 Tests/LibWeb/Text/input/canvas/basic.html

diff --git a/Tests/LibWeb/Text/expected/canvas/basic.txt b/Tests/LibWeb/Text/expected/canvas/basic.txt
new file mode 100644
index 0000000000..07cc20e4ac
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/canvas/basic.txt
@@ -0,0 +1,2 @@
+normal normal 20px SerenitySans
+normal normal 20px SerenitySans
diff --git a/Tests/LibWeb/Text/input/canvas/basic.html b/Tests/LibWeb/Text/input/canvas/basic.html
new file mode 100644
index 0000000000..8eeb3fe0c1
--- /dev/null
+++ b/Tests/LibWeb/Text/input/canvas/basic.html
@@ -0,0 +1,11 @@
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        let canvas = document.createElement("canvas");
+        let context = canvas.getContext("2d");
+        context.font = '20px SerenitySans';
+        println(context.font);
+        context.font = '!!!'; // Invalid value, should be ignored.
+        println(context.font);
+    });
+</script>
diff --git a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTextDrawingStyles.h b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTextDrawingStyles.h
index b6f662cd7b..36836292bc 100644
--- a/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTextDrawingStyles.h
+++ b/Userland/Libraries/LibWeb/HTML/Canvas/CanvasTextDrawingStyles.h
@@ -45,7 +45,7 @@ public:
         auto font_style_value_result = parse_css_value(parsing_context, font, CSS::PropertyID::Font);
 
         // If the new value is syntactically incorrect (including using property-independent style sheet syntax like 'inherit' or 'initial'), then it must be ignored, without assigning a new font value.
-        if (font_style_value_result.is_error()) {
+        if (font_style_value_result.is_error() || !font_style_value_result.value()) {
             return;
         }
         my_drawing_state().font_style_value = font_style_value_result.value();