Add Servo_GetProperties_Overriding_Animation.

We add one FFI, Servo_GetProperties_Overriding_Animation, which calls
StrongRuleNode::get_properties_overriding_animations() to get a LonghandIdSet,
which may override animation properties running on compositor.

components/style/gecko/generated/bindings.rs

@@ -10,6 +10,7 @@ use gecko_bindings::structs::mozilla::css::URLValue;
 use gecko_bindings::structs::mozilla::Side;
 use gecko_bindings::structs::RawGeckoAnimationPropertySegment;
 use gecko_bindings::structs::RawGeckoComputedTiming;
+use gecko_bindings::structs::RawGeckoCSSPropertyIDList;
 use gecko_bindings::structs::RawGeckoDocument;
 use gecko_bindings::structs::RawGeckoElement;
 use gecko_bindings::structs::RawGeckoKeyframeList;
@@ -48,6 +49,7 @@ use gecko_bindings::structs::nsCSSCounterStyleRule;
 use gecko_bindings::structs::nsCSSFontFaceRule;
 use gecko_bindings::structs::nsCSSKeyword;
 use gecko_bindings::structs::nsCSSPropertyID;
+use gecko_bindings::structs::nsCSSPropertyIDSet;
 use gecko_bindings::structs::nsCSSShadowArray;
 use gecko_bindings::structs::nsCSSUnit;
 use gecko_bindings::structs::nsCSSValue;
@@ -316,6 +318,10 @@ pub type RawGeckoPresContextBorrowed<'a> = &'a RawGeckoPresContext;
 pub type RawGeckoPresContextBorrowedOrNull<'a> = Option<&'a RawGeckoPresContext>;
 pub type RawGeckoStyleAnimationListBorrowed<'a> = &'a RawGeckoStyleAnimationList;
 pub type RawGeckoStyleAnimationListBorrowedOrNull<'a> = Option<&'a RawGeckoStyleAnimationList>;
+pub type nsCSSPropertyIDSetBorrowed<'a> = &'a nsCSSPropertyIDSet;
+pub type nsCSSPropertyIDSetBorrowedOrNull<'a> = Option<&'a nsCSSPropertyIDSet>;
+pub type nsCSSPropertyIDSetBorrowedMut<'a> = &'a mut nsCSSPropertyIDSet;
+pub type nsCSSPropertyIDSetBorrowedMutOrNull<'a> = Option<&'a mut nsCSSPropertyIDSet>;
 pub type nsCSSValueBorrowed<'a> = &'a nsCSSValue;
 pub type nsCSSValueBorrowedOrNull<'a> = Option<&'a nsCSSValue>;
 pub type nsCSSValueBorrowedMut<'a> = &'a mut nsCSSValue;
@@ -352,6 +358,10 @@ pub type RawGeckoServoStyleRuleListBorrowed<'a> = &'a RawGeckoServoStyleRuleList
 pub type RawGeckoServoStyleRuleListBorrowedOrNull<'a> = Option<&'a RawGeckoServoStyleRuleList>;
 pub type RawGeckoServoStyleRuleListBorrowedMut<'a> = &'a mut RawGeckoServoStyleRuleList;
 pub type RawGeckoServoStyleRuleListBorrowedMutOrNull<'a> = Option<&'a mut RawGeckoServoStyleRuleList>;
+pub type RawGeckoCSSPropertyIDListBorrowed<'a> = &'a RawGeckoCSSPropertyIDList;
+pub type RawGeckoCSSPropertyIDListBorrowedOrNull<'a> = Option<&'a RawGeckoCSSPropertyIDList>;
+pub type RawGeckoCSSPropertyIDListBorrowedMut<'a> = &'a mut RawGeckoCSSPropertyIDList;
+pub type RawGeckoCSSPropertyIDListBorrowedMutOrNull<'a> = Option<&'a mut RawGeckoCSSPropertyIDList>;
 
 extern "C" {
     pub fn Gecko_EnsureTArrayCapacity(aArray: *mut ::std::os::raw::c_void,
@@ -1363,6 +1373,10 @@ extern "C" {
                                       ident: *const u16,
                                       set_slow_selector: *mut bool) -> bool;
 }
+extern "C" {
+    pub fn Gecko_AddPropertyToSet(arg1: nsCSSPropertyIDSetBorrowedMut,
+                                  arg2: nsCSSPropertyID);
+}
 extern "C" {
     pub fn Gecko_Construct_Default_nsStyleFont(ptr: *mut nsStyleFont,
                                                pres_context:
@@ -2076,6 +2090,14 @@ extern "C" {
     pub fn Servo_Property_IsDiscreteAnimatable(property: nsCSSPropertyID)
      -> bool;
 }
+extern "C" {
+    pub fn Servo_GetProperties_Overriding_Animation(arg1:
+                                                        RawGeckoElementBorrowed,
+                                                    arg2:
+                                                        RawGeckoCSSPropertyIDListBorrowed,
+                                                    arg3:
+                                                        nsCSSPropertyIDSetBorrowedMut);
+}
 extern "C" {
     pub fn Servo_AnimationValues_Interpolate(from:
                                                  RawServoAnimationValueBorrowed,

components/style/properties/properties.mako.rs

@@ -954,7 +954,7 @@ impl PropertyId {
         }
     }
 
-    /// Returns a property id from Gecko's nsCSSPropertyID.
+    /// Returns an nsCSSPropertyID.
     #[cfg(feature = "gecko")]
     #[allow(non_upper_case_globals)]
     pub fn to_nscsspropertyid(&self) -> Result<nsCSSPropertyID, ()> {

components/style/rule_tree/mod.rs

@@ -8,7 +8,7 @@
 
 #[cfg(feature = "servo")]
 use heapsize::HeapSizeOf;
-use properties::{Importance, PropertyDeclarationBlock};
+use properties::{Importance, LonghandIdSet, PropertyDeclarationBlock};
 use shared_lock::{Locked, StylesheetGuards, SharedRwLockReadGuard};
 use smallvec::SmallVec;
 use std::io::{self, Write};
@@ -1092,6 +1092,42 @@ impl StrongRuleNode {
             .take_while(|node| node.cascade_level() >= CascadeLevel::SMILOverride)
             .any(|node| node.cascade_level().is_animation())
     }
+
+    /// Get a set of properties whose CascadeLevel are higher than Animations but not equal to
+    /// Transitions. If there are any custom properties, we set the boolean value of the returned
+    /// tuple to true.
+    pub fn get_properties_overriding_animations(&self, guards: &StylesheetGuards)
+                                                -> (LonghandIdSet, bool) {
+        use properties::PropertyDeclarationId;
+
+        // We want to iterate over cascade levels that override the animations level, i.e.
+        // !important levels and the transitions level. However, we actually want to skip the
+        // transitions level because although it is higher in the cascade than animations, when
+        // both transitions and animations are present for a given element and property, transitions
+        // are suppressed so that they don't actually override animations.
+        let iter = self.self_and_ancestors()
+                       .skip_while(|node| node.cascade_level() == CascadeLevel::Transitions)
+                       .take_while(|node| node.cascade_level() > CascadeLevel::Animations);
+        let mut result = (LonghandIdSet::new(), false);
+        for node in iter {
+            let style = node.style_source().unwrap();
+            for &(ref decl, important) in style.read(node.cascade_level().guard(guards))
+                                               .declarations()
+                                               .iter() {
+                // Although we are only iterating over cascade levels that override animations,
+                // in a given property declaration block we can have a mixture of !important and
+                // non-!important declarations but only the !important declarations actually
+                // override animations.
+                if important.important() {
+                    match decl.id() {
+                        PropertyDeclarationId::Longhand(id) => result.0.insert(id),
+                        PropertyDeclarationId::Custom(_) => result.1 = true
+                    }
+                }
+            }
+        }
+        result
+    }
 }
 
 /// An iterator over a rule node and its ancestors.

ports/geckolib/glue.rs

@@ -40,11 +40,13 @@ use style::gecko_bindings::bindings::{RawServoStyleSheetBorrowed, ServoComputedV
 use style::gecko_bindings::bindings::{RawServoStyleSheetStrong, ServoComputedValuesStrong};
 use style::gecko_bindings::bindings::{RawServoSupportsRule, RawServoSupportsRuleBorrowed};
 use style::gecko_bindings::bindings::{ServoCssRulesBorrowed, ServoCssRulesStrong};
-use style::gecko_bindings::bindings::{nsACString, nsAString};
+use style::gecko_bindings::bindings::{nsACString, nsAString, nsCSSPropertyIDSetBorrowedMut};
+use style::gecko_bindings::bindings::Gecko_AddPropertyToSet;
 use style::gecko_bindings::bindings::Gecko_GetOrCreateFinalKeyframe;
 use style::gecko_bindings::bindings::Gecko_GetOrCreateInitialKeyframe;
 use style::gecko_bindings::bindings::Gecko_GetOrCreateKeyframeAtStart;
 use style::gecko_bindings::bindings::RawGeckoAnimationPropertySegmentBorrowed;
+use style::gecko_bindings::bindings::RawGeckoCSSPropertyIDListBorrowed;
 use style::gecko_bindings::bindings::RawGeckoComputedKeyframeValuesListBorrowedMut;
 use style::gecko_bindings::bindings::RawGeckoComputedTimingBorrowed;
 use style::gecko_bindings::bindings::RawGeckoElementBorrowed;
@@ -1319,6 +1321,38 @@ pub extern "C" fn Servo_ParseEasing(easing: *const nsAString,
     }
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_GetProperties_Overriding_Animation(element: RawGeckoElementBorrowed,
+                                                           list: RawGeckoCSSPropertyIDListBorrowed,
+                                                           set: nsCSSPropertyIDSetBorrowedMut) {
+    let element = GeckoElement(element);
+    let element_data = match element.borrow_data() {
+        Some(data) => data,
+        None => return
+    };
+    let global_style_data = &*GLOBAL_STYLE_DATA;
+    let guard = global_style_data.shared_lock.read();
+    let guards = StylesheetGuards::same(&guard);
+    let (overridden, custom) =
+        element_data.styles().primary.rules.get_properties_overriding_animations(&guards);
+    for p in list.iter() {
+        match PropertyId::from_nscsspropertyid(*p) {
+            Ok(property) => {
+                if let PropertyId::Longhand(id) = property {
+                    if overridden.contains(id) {
+                        unsafe { Gecko_AddPropertyToSet(set, *p) };
+                    }
+                }
+            },
+            Err(_) => {
+                if *p == nsCSSPropertyID::eCSSPropertyExtra_variable && custom {
+                    unsafe { Gecko_AddPropertyToSet(set, *p) };
+                }
+            }
+        }
+    }
+}
+
 #[no_mangle]
 pub extern "C" fn Servo_ParseStyleAttribute(data: *const nsACString,
                                             raw_extra_data: *mut URLExtraData,