Look for relevant links while matching

Adjust the matching process to look for a "relevant link" while matching.  A
"relevant link" is the element being matched if it is a link or the nearest
ancestor link.

Matching for links now depends on the `VisitedHandlingMode`, which determines
whether all links match as if they are unvisited (the default) or if the
relevant link matches as visited (and all others remain unvisited).

If a relevant link is ever found for any selector, track this as part of the
`MatchingContext` object.  This is used in the next patch to determine if an
additional match and cascade should be performed to compute the styles when
visited.

MozReview-Commit-ID: 3xUbRo7vpuD

components/script/dom/element.rs

@@ -87,8 +87,9 @@ use ref_filter_map::ref_filter_map;
 use script_layout_interface::message::ReflowQueryType;
 use script_thread::Runnable;
 use selectors::attr::{AttrSelectorOperation, NamespaceConstraint};
-use selectors::matching::{ElementSelectorFlags, MatchingContext, MatchingMode, matches_selector_list};
+use selectors::matching::{ElementSelectorFlags, MatchingContext, MatchingMode};
 use selectors::matching::{HAS_EDGE_CHILD_SELECTOR, HAS_SLOW_SELECTOR, HAS_SLOW_SELECTOR_LATER_SIBLINGS};
+use selectors::matching::{RelevantLinkStatus, matches_selector_list};
 use servo_atoms::Atom;
 use std::ascii::AsciiExt;
 use std::borrow::Cow;
@@ -2429,6 +2430,7 @@ impl<'a> ::selectors::Element for Root<Element> {
     fn match_non_ts_pseudo_class<F>(&self,
                                     pseudo_class: &NonTSPseudoClass,
                                     _: &mut MatchingContext,
+                                    _: &RelevantLinkStatus,
                                     _: &mut F)
                                     -> bool
         where F: FnMut(&Self, ElementSelectorFlags),
@@ -2478,6 +2480,20 @@ impl<'a> ::selectors::Element for Root<Element> {
         }
     }
 
+    fn is_link(&self) -> bool {
+        // FIXME: This is HTML only.
+        let node = self.upcast::<Node>();
+        match node.type_id() {
+            // https://html.spec.whatwg.org/multipage/#selector-link
+            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAnchorElement)) |
+            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAreaElement)) |
+            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) => {
+                self.has_attribute(&local_name!("href"))
+            },
+            _ => false,
+        }
+    }
+
     fn get_id(&self) -> Option<Atom> {
         self.id_attribute.borrow().clone()
     }
@@ -2592,20 +2608,6 @@ impl Element {
         }
     }
 
-    fn is_link(&self) -> bool {
-        // FIXME: This is HTML only.
-        let node = self.upcast::<Node>();
-        match node.type_id() {
-            // https://html.spec.whatwg.org/multipage/#selector-link
-            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAnchorElement)) |
-            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAreaElement)) |
-            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) => {
-                self.has_attribute(&local_name!("href"))
-            },
-            _ => false,
-        }
-    }
-
     /// Please call this method *only* for real click events
     ///
     /// https://html.spec.whatwg.org/multipage/#run-authentic-click-activation-steps

components/script/layout_wrapper.rs

@@ -51,7 +51,7 @@ use script_layout_interface::{OpaqueStyleAndLayoutData, PartialPersistentLayoutD
 use script_layout_interface::wrapper_traits::{DangerousThreadSafeLayoutNode, GetLayoutData, LayoutNode};
 use script_layout_interface::wrapper_traits::{PseudoElementType, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
 use selectors::attr::{AttrSelectorOperation, NamespaceConstraint};
-use selectors::matching::{ElementSelectorFlags, MatchingContext};
+use selectors::matching::{ElementSelectorFlags, MatchingContext, RelevantLinkStatus};
 use servo_atoms::Atom;
 use servo_url::ServoUrl;
 use std::fmt;
@@ -680,6 +680,7 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
     fn match_non_ts_pseudo_class<F>(&self,
                                     pseudo_class: &NonTSPseudoClass,
                                     _: &mut MatchingContext,
+                                    _: &RelevantLinkStatus,
                                     _: &mut F)
                                     -> bool
         where F: FnMut(&Self, ElementSelectorFlags),
@@ -687,16 +688,7 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
         match *pseudo_class {
             // https://github.com/servo/servo/issues/8718
             NonTSPseudoClass::Link |
-            NonTSPseudoClass::AnyLink => unsafe {
-                match self.as_node().script_type_id() {
-                    // https://html.spec.whatwg.org/multipage/#selector-link
-                    NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAnchorElement)) |
-                    NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAreaElement)) |
-                    NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) =>
-                        (*self.element.unsafe_get()).get_attr_val_for_layout(&ns!(), &local_name!("href")).is_some(),
-                    _ => false,
-                }
-            },
+            NonTSPseudoClass::AnyLink => self.is_link(),
             NonTSPseudoClass::Visited => false,
 
             // FIXME(#15746): This is wrong, we need to instead use extended filtering as per RFC4647
@@ -731,6 +723,20 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
         }
     }
 
+    #[inline]
+    fn is_link(&self) -> bool {
+        unsafe {
+            match self.as_node().script_type_id() {
+                // https://html.spec.whatwg.org/multipage/#selector-link
+                NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAnchorElement)) |
+                NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLAreaElement)) |
+                NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) =>
+                    (*self.element.unsafe_get()).get_attr_val_for_layout(&ns!(), &local_name!("href")).is_some(),
+                _ => false,
+            }
+        }
+    }
+
     #[inline]
     fn get_id(&self) -> Option<Atom> {
         unsafe {
@@ -1187,6 +1193,7 @@ impl<'le> ::selectors::Element for ServoThreadSafeLayoutElement<'le> {
     fn match_non_ts_pseudo_class<F>(&self,
                                     _: &NonTSPseudoClass,
                                     _: &mut MatchingContext,
+                                    _: &RelevantLinkStatus,
                                     _: &mut F)
                                     -> bool
         where F: FnMut(&Self, ElementSelectorFlags),
@@ -1196,6 +1203,11 @@ impl<'le> ::selectors::Element for ServoThreadSafeLayoutElement<'le> {
         false
     }
 
+    fn is_link(&self) -> bool {
+        warn!("ServoThreadSafeLayoutElement::is_link called");
+        false
+    }
+
     fn get_id(&self) -> Option<Atom> {
         debug!("ServoThreadSafeLayoutElement::get_id called");
         None