style: Correct style sharing handling for any element that considered `:has()` in selector matching

For any element that anchors a `:has()` selector (i.e. Matches a selector that
contains a `:has()` on its rightmost side), we prevent style sharing altogether,
as evaluation of the `:has()` selector is required in the first place to
determine style sharing.

On the other hand, any element matching a rule containing `:has()` without
anchoring it can do style sharing for siblings, but not cousins.

Differential Revision: https://phabricator.services.mozilla.com/D176836

1 files changed, 8 insertions, 0 deletions

diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index ac4f113c93e..eb3ab03c73c 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -895,6 +895,9 @@ fn selector_flags_to_node_flags(flags: ElementSelectorFlags) -> u32 {
     if flags.contains(ElementSelectorFlags::HAS_EMPTY_SELECTOR) {
         gecko_flags |= NODE_HAS_EMPTY_SELECTOR;
     }
+    if flags.contains(ElementSelectorFlags::ANCHORS_RELATIVE_SELECTOR) {
+        gecko_flags |= NODE_ANCHORS_RELATIVE_SELECTOR;
+    }
 
     gecko_flags
 }
@@ -1729,6 +1732,11 @@ impl<'le> TElement for GeckoElement<'le> {
             }
         }
     }
+
+    fn anchors_relative_selector(&self) -> bool {
+        use crate::gecko_bindings::structs::NODE_ANCHORS_RELATIVE_SELECTOR;
+        self.flags() & NODE_ANCHORS_RELATIVE_SELECTOR != 0
+    }
 }
 
 impl<'le> PartialEq for GeckoElement<'le> {