From 79c63809e368313bd87a11ef1db88d8d20d554ce Mon Sep 17 00:00:00 2001
From: ldm0 <ldm2993593805@163.com>
Date: Sun, 30 Aug 2026 17:05:13 +0800
Subject: [PATCH] fix(css): enable starting-style parsing

---
 .../css_stylesheet_runtime/tests.rs           | 21 +++++++++++++++++++
 moli-renderer-v8/src/style_engine/mod.rs      |  1 +
 2 files changed, 22 insertions(+)

diff --git a/moli-renderer-v8/src/context_bootstrap/css_stylesheet_runtime/tests.rs b/moli-renderer-v8/src/context_bootstrap/css_stylesheet_runtime/tests.rs
index e5af1b5e58..d8aa617dd8 100644
--- a/moli-renderer-v8/src/context_bootstrap/css_stylesheet_runtime/tests.rs
+++ b/moli-renderer-v8/src/context_bootstrap/css_stylesheet_runtime/tests.rs
@@ -777,6 +777,27 @@ fn grouping_rule_css_text_uses_stylo_rule_view_serialization() {
     );
 }
 
+#[test]
+fn starting_style_rule_accepts_an_empty_prelude_and_rejects_nonempty_preludes() {
+    crate::style_engine::ensure_stylo_browser_compat_prefs();
+
+    assert_eq!(
+        parsed_top_level_rule_texts("@starting-style {}"),
+        ["@starting-style {\n}"]
+    );
+    for css_text in [
+        "@starting-style div {}",
+        "@starting-style () {}",
+        "@starting-style ( {}",
+        "@starting-style }{}",
+    ] {
+        assert!(
+            parsed_top_level_rule_texts(css_text).is_empty(),
+            "unexpectedly accepted {css_text:?}"
+        );
+    }
+}
+
 #[test]
 fn grouping_rule_css_text_uses_stylo_page_rule_child_serialization() {
     let css_text =
diff --git a/moli-renderer-v8/src/style_engine/mod.rs b/moli-renderer-v8/src/style_engine/mod.rs
index fe336fea40..f4d0d1a97c 100644
--- a/moli-renderer-v8/src/style_engine/mod.rs
+++ b/moli-renderer-v8/src/style_engine/mod.rs
@@ -1119,6 +1119,7 @@ pub(crate) fn ensure_stylo_browser_compat_prefs() {
         stylo_static_prefs::set_pref!("layout.css.content.alt-text.enabled", true);
         stylo_static_prefs::set_pref!("layout.css.margin-rules.enabled", true);
         stylo_static_prefs::set_pref!("layout.css.scroll-driven-animations.enabled", true);
+        stylo_static_prefs::set_pref!("layout.css.starting-style-at-rules.enabled", true);
         stylo_static_prefs::set_pref!("layout.css.style-queries.enabled", true);
         stylo_static_prefs::set_pref!("layout.css.tree-counting-functions.enabled", true);
         stylo_static_prefs::set_pref!("layout.css.zoom.enabled", true);