Log element during selector matching

MozReview-Commit-ID: D8eFyRCy5BR

7 files changed, 34 insertions, 2 deletions

diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index f875986edd2..c0d4b6b700a 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -151,6 +151,12 @@ impl fmt::Debug for Element {
     }
 }
 
+impl fmt::Debug for Root<Element> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
 #[derive(PartialEq, HeapSizeOf)]
 pub enum ElementCreator {
     ParserCreated(u64),
diff --git a/components/selectors/Cargo.toml b/components/selectors/Cargo.toml
index 15aba3d1811..90ff6ecaa17 100644
--- a/components/selectors/Cargo.toml
+++ b/components/selectors/Cargo.toml
@@ -25,6 +25,7 @@ gecko_like_types = []
 bitflags = "0.7"
 matches = "0.1"
 cssparser = "0.13.7"
+log = "0.3"
 fnv = "1.0"
 phf = "0.7.18"
 precomputed-hash = "0.1"
diff --git a/components/selectors/lib.rs b/components/selectors/lib.rs
index a6f4acd3d84..130475271fc 100644
--- a/components/selectors/lib.rs
+++ b/components/selectors/lib.rs
@@ -4,6 +4,7 @@
 
 #[macro_use] extern crate bitflags;
 #[macro_use] extern crate cssparser;
+#[macro_use] extern crate log;
 #[macro_use] extern crate matches;
 extern crate fnv;
 extern crate phf;
diff --git a/components/selectors/matching.rs b/components/selectors/matching.rs
index 3c269427421..84ddde2b261 100644
--- a/components/selectors/matching.rs
+++ b/components/selectors/matching.rs
@@ -198,7 +198,7 @@ fn may_match<E>(hashes: &AncestorHashes,
 /// and `is_unvisited` are based on relevant link state of only the current
 /// complex selector being matched (not the global relevant link status for all
 /// selectors in `MatchingContext`).
-#[derive(PartialEq, Eq, Copy, Clone)]
+#[derive(PartialEq, Eq, Copy, Clone, Debug)]
 pub enum RelevantLinkStatus {
     /// Looking for a possible relevant link.  This is the initial mode when
     /// matching a selector.
@@ -429,6 +429,9 @@ fn matches_complex_selector_internal<E, F>(mut selector_iter: SelectorIter<E::Im
         matches_simple_selector(simple, element, context, &relevant_link, flags_setter)
     });
 
+    debug!("Matching for {:?}, simple selector {:?}, relevant link {:?}",
+           element, selector_iter, relevant_link);
+
     let combinator = selector_iter.next_sequence();
     let siblings = combinator.map_or(false, |c| c.is_sibling());
     if siblings {
diff --git a/components/selectors/parser.rs b/components/selectors/parser.rs
index 92ba8c17601..a00122a3208 100644
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@@ -453,6 +453,16 @@ impl<'a, Impl: SelectorImpl> Iterator for SelectorIter<'a, Impl> {
     }
 }
 
+impl<'a, Impl: SelectorImpl> fmt::Debug for SelectorIter<'a, Impl> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let iter = self.iter.clone().rev();
+        for component in iter {
+            component.to_css(f)?
+        }
+        Ok(())
+    }
+}
+
 /// An iterator over all simple selectors belonging to ancestors.
 pub struct AncestorIter<'a, Impl: 'a + SelectorImpl>(SelectorIter<'a, Impl>);
 impl<'a, Impl: 'a + SelectorImpl> AncestorIter<'a, Impl> {
diff --git a/components/selectors/tree.rs b/components/selectors/tree.rs
index 6122f22490f..93b59dbb4c5 100644
--- a/components/selectors/tree.rs
+++ b/components/selectors/tree.rs
@@ -8,8 +8,9 @@
 use attr::{AttrSelectorOperation, NamespaceConstraint};
 use matching::{ElementSelectorFlags, MatchingContext, RelevantLinkStatus};
 use parser::SelectorImpl;
+use std::fmt::Debug;
 
-pub trait Element: Sized {
+pub trait Element: Sized + Debug {
     type Impl: SelectorImpl;
 
     fn parent_element(&self) -> Option<Self>;
diff --git a/components/style/restyle_hints.rs b/components/style/restyle_hints.rs
index 53e33608967..44eec13f13c 100644
--- a/components/style/restyle_hints.rs
+++ b/components/style/restyle_hints.rs
@@ -29,6 +29,7 @@ use smallvec::SmallVec;
 use std::cell::Cell;
 use std::clone::Clone;
 use std::cmp;
+use std::fmt;
 
 /// When the ElementState of an element (like IN_HOVER_STATE) changes,
 /// certain pseudo-classes (like :hover) may require us to restyle that
@@ -607,6 +608,15 @@ impl<'a, E> ElementWrapper<'a, E>
     }
 }
 
+impl<'a, E> fmt::Debug for ElementWrapper<'a, E>
+    where E: TElement,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // Ignore other fields for now, can change later if needed.
+        self.element.fmt(f)
+    }
+}
+
 #[cfg(feature = "gecko")]
 fn dir_selector_to_state(s: &[u16]) -> ElementState {
     // Jump through some hoops to deal with our Box<[u16]> thing.