1 files changed, 63 insertions, 0 deletions
diff --git a/widget/tests/system_font_changes.xhtml b/widget/tests/system_font_changes.xhtml
new file mode 100644
index 0000000000..1cef650015
--- /dev/null
+++ b/widget/tests/system_font_changes.xhtml
@@ -0,0 +1,63 @@
+<?xml version="1.0"?>
+
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+
+<window id="system_font_changes_window"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+        width="300"
+        height="300"
+        onload="start();">
+
+<span id="target" style="font:menu">Hello world</span>
+
+<script type="application/javascript"><![CDATA[
+  function is(condition, message) {
+    window.arguments[0].SimpleTest.is(condition, message);
+  }
+  function registerCleanupFunction(func) {
+    window.arguments[0].SimpleTest.registerCleanupFunction(func);
+  }
+
+  async function waitForFrame() {
+    return new Promise(resolve => {
+      requestAnimationFrame(resolve);
+    });
+  }
+
+  let windowUtils = window.windowUtils;
+  async function start() {
+    await waitForFrame();
+
+    const originalSystemFont = windowUtils.systemFont;
+    registerCleanupFunction(() => {
+      windowUtils.systemFont = originalSystemFont;
+    });
+
+    windowUtils.systemFont = 'Sans 11';
+    is(windowUtils.systemFont, 'Sans 11');
+
+    // Wait for two frames for the safety since the notification for system
+    // font changes is asynchronously processed.
+    await waitForFrame();
+    await waitForFrame();
+
+    const target = document.getElementById('target');
+    is(getComputedStyle(target).fontFamily, 'Sans');
+
+    windowUtils.systemFont = 'Serif 11';
+    is(windowUtils.systemFont, 'Serif 11');
+
+    await waitForFrame();
+    await waitForFrame();
+
+    is(getComputedStyle(target).fontFamily, 'Serif');
+
+    window.close();
+    window.arguments[0].SimpleTest.finish();
+  }
+]]></script>
+</window>