Auto merge of #17740 - hiikezoe:post-traversal-fix, r=emilio

Post traversal fix triggered by animation-only restyle for event handling

<!-- Please describe your changes on the following line: -->
https://bugzilla.mozilla.org/show_bug.cgi?id=1371450

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

components/style/data.rs

@@ -61,6 +61,12 @@ impl RestyleData {
         *self = Self::new();
     }
 
+    /// Clear restyle flags and damage.
+    fn clear_flags_and_damage(&mut self) {
+        self.damage = RestyleDamage::empty();
+        self.flags = RestyleFlags::empty();
+    }
+
     /// Returns whether this element or any ancestor is going to be
     /// reconstructed.
     pub fn reconstructed_self_or_ancestor(&self) -> bool {
@@ -331,4 +337,9 @@ impl ElementData {
     pub fn clear_restyle_state(&mut self) {
         self.restyle.clear();
     }
+
+    /// Drops restyle flags and damage from the element.
+    pub fn clear_restyle_flags_and_damage(&mut self) {
+        self.restyle.clear_flags_and_damage();
+    }
 }

components/style/gecko/generated/atom_macro.rs

@@ -4900,8 +4900,6 @@ cfg_if! {
             pub static nsGkAtoms_refx: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms4refyE"]
             pub static nsGkAtoms_refy: *mut nsIAtom;
-            #[link_name = "_ZN9nsGkAtoms7isindexE"]
-            pub static nsGkAtoms_isindex: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms7fefuncaE"]
             pub static nsGkAtoms_fefunca: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms7fefuncbE"]
@@ -10029,8 +10027,6 @@ cfg_if! {
             pub static nsGkAtoms_refx: *mut nsIAtom;
             #[link_name = "?refy@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_refy: *mut nsIAtom;
-            #[link_name = "?isindex@nsGkAtoms@@2PEAVnsIAtom@@EA"]
-            pub static nsGkAtoms_isindex: *mut nsIAtom;
             #[link_name = "?fefunca@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_fefunca: *mut nsIAtom;
             #[link_name = "?fefuncb@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -15158,8 +15154,6 @@ cfg_if! {
             pub static nsGkAtoms_refx: *mut nsIAtom;
             #[link_name = "\x01?refy@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_refy: *mut nsIAtom;
-            #[link_name = "\x01?isindex@nsGkAtoms@@2PAVnsIAtom@@A"]
-            pub static nsGkAtoms_isindex: *mut nsIAtom;
             #[link_name = "\x01?fefunca@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_fefunca: *mut nsIAtom;
             #[link_name = "\x01?fefuncb@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -20290,8 +20284,6 @@ macro_rules! atom {
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_refx as *mut _) } };
 ("refy") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_refy as *mut _) } };
-("isindex") =>
-  { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_isindex as *mut _) } };
 ("fefunca") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_fefunca as *mut _) } };
 ("fefuncb") =>

components/style/gecko/generated/bindings.rs

@@ -2709,8 +2709,9 @@ extern "C" {
                                    change_hint: nsChangeHint);
 }
 extern "C" {
-    pub fn Servo_TakeChangeHint(element: RawGeckoElementBorrowed)
+    pub fn Servo_TakeChangeHint(element: RawGeckoElementBorrowed,
-     -> nsChangeHint;
+                                restyle_behavior: TraversalRestyleBehavior,
+                                was_restyled: *mut bool) -> nsChangeHint;
 }
 extern "C" {
     pub fn Servo_ResolveStyle(element: RawGeckoElementBorrowed,

ports/geckolib/glue.rs

@@ -257,16 +257,16 @@ pub extern "C" fn Servo_TraverseSubtree(root: RawGeckoElementBorrowed,
     debug_assert!(!snapshots.is_null());
 
     let element = GeckoElement(root);
-    debug!("Servo_TraverseSubtree: {:?}", element);
+    debug!("Servo_TraverseSubtree: {:?} {:?}", element, restyle_behavior);
 
     let traversal_flags = match (root_behavior, restyle_behavior) {
         (Root::Normal, Restyle::Normal) |
         (Root::Normal, Restyle::ForNewlyBoundElement) |
-        (Root::Normal, Restyle::ForAnimationOnly)
+        (Root::Normal, Restyle::ForThrottledAnimationFlush)
             => TraversalFlags::empty(),
         (Root::UnstyledChildrenOnly, Restyle::Normal) |
         (Root::UnstyledChildrenOnly, Restyle::ForNewlyBoundElement) |
-        (Root::UnstyledChildrenOnly, Restyle::ForAnimationOnly)
+        (Root::UnstyledChildrenOnly, Restyle::ForThrottledAnimationFlush)
             => UNSTYLED_CHILDREN_ONLY,
         (Root::Normal, Restyle::ForCSSRuleChanges) => FOR_CSS_RULE_CHANGES,
         (Root::Normal, Restyle::ForReconstruct) => FOR_RECONSTRUCT,
@@ -282,8 +282,9 @@ pub extern "C" fn Servo_TraverseSubtree(root: RawGeckoElementBorrowed,
                          unsafe { &*snapshots });
     }
 
-    if restyle_behavior == Restyle::ForAnimationOnly {
+    if restyle_behavior == Restyle::ForThrottledAnimationFlush {
-        return needs_animation_only_restyle;
+        return element.has_animation_only_dirty_descendants() ||
+               element.borrow_data().unwrap().restyle.is_restyle();
     }
 
     traverse_subtree(element,
@@ -2728,17 +2729,37 @@ pub extern "C" fn Servo_NoteExplicitHints(element: RawGeckoElementBorrowed,
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_TakeChangeHint(element: RawGeckoElementBorrowed) -> nsChangeHint
+pub extern "C" fn Servo_TakeChangeHint(element: RawGeckoElementBorrowed,
+                                       restyle_behavior: structs::TraversalRestyleBehavior,
+                                       was_restyled: *mut bool) -> nsChangeHint
 {
+    let mut was_restyled =  unsafe { was_restyled.as_mut().unwrap() };
     let element = GeckoElement(element);
+
     let damage = match element.mutate_data() {
         Some(mut data) => {
+            *was_restyled = data.restyle.is_restyle();
+
             let damage = data.restyle.damage;
-            data.clear_restyle_state();
+            if restyle_behavior == structs::TraversalRestyleBehavior::ForThrottledAnimationFlush {
+                debug_assert!(data.restyle.is_restyle() || damage.is_empty(),
+                              "Restyle damage should be empty if the element was not restyled");
+                // In the case where we call this function for post traversal for
+                // flusing throttled animations (i.e. without normal restyle
+                // traversal), we need to preserve restyle hints for normal restyle
+                // traversal. Restyle hints for animations have been already
+                // removed during animation-only traversal.
+                debug_assert!(!data.restyle.hint.has_animation_hint(),
+                              "Animation restyle hints should have been already removed");
+                data.clear_restyle_flags_and_damage();
+            } else {
+                data.clear_restyle_state();
+            }
             damage
         }
         None => {
             warn!("Trying to get change hint from unstyled element");
+            *was_restyled = false;
             GeckoRestyleDamage::empty()
         }
     };