Auto merge of #16963 - BorisChiou:stylo/animation/omta, r=emilio

stylo: Bug 1334036 - Enable animations running on compositor.

These are interdependent patches of Bug 1334036, which enables off-main thread animations. We add one FFI to get the property id set which overriding animations, so we can make sure the cascade result is correct for off-main thread animations.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [Bug 1334036](https://bugzilla.mozilla.org/show_bug.cgi?id=1334036)
- [X] These changes do not require tests because we support off-main thread animation only on Gecko, and there are enough test cases there.

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components/script/layout_wrapper.rs

@@ -486,7 +486,10 @@ impl<'le> TElement for ServoLayoutElement<'le> {
     }
 
     fn has_animations(&self) -> bool {
-        unreachable!("this should be only called on gecko");
+        // We use this function not only for Gecko but also for Servo to know if this element has
+        // animations, so we maybe try to get the important rules of this element. This is used for
+        // off-main thread animations, but we don't support it on Servo, so return false directly.
+        false
     }
 
     fn has_css_animations(&self) -> bool {

components/style/data.rs

@@ -13,6 +13,7 @@ use properties::longhands::display::computed_value as display;
 use restyle_hints::{RESTYLE_DESCENDANTS, RESTYLE_LATER_SIBLINGS, RESTYLE_SELF, RestyleHint};
 use rule_tree::StrongRuleNode;
 use selector_parser::{EAGER_PSEUDO_COUNT, PseudoElement, RestyleDamage};
+use shared_lock::StylesheetGuards;
 #[cfg(feature = "servo")] use std::collections::HashMap;
 use std::fmt;
 #[cfg(feature = "servo")] use std::hash::BuildHasherDefault;
@@ -506,6 +507,24 @@ impl ElementData {
         true
     }
 
+    /// Return true if important rules are different.
+    /// We use this to make sure the cascade of off-main thread animations is correct.
+    /// Note: Ignore custom properties for now because we only support opacity and transform
+    ///       properties for animations running on compositor. Actually, we only care about opacity
+    ///       and transform for now, but it's fine to compare all properties and let the user
+    ///       the check which properties do they want.
+    ///       If it costs too much, get_properties_overriding_animations() should return a set
+    ///       containing only opacity and transform properties.
+    pub fn important_rules_are_different(&self,
+                                         rules: &StrongRuleNode,
+                                         guards: &StylesheetGuards) -> bool {
+        debug_assert!(self.has_styles());
+        let (important_rules, _custom) =
+            self.styles().primary.rules.get_properties_overriding_animations(&guards);
+        let (other_important_rules, _custom) = rules.get_properties_overriding_animations(&guards);
+        important_rules != other_important_rules
+    }
+
     /// Returns true if the Element has a RestyleData.
     pub fn has_restyle(&self) -> bool {
         self.restyle.is_some()

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,
@@ -1177,6 +1187,9 @@ extern "C" {
 extern "C" {
     pub fn Gecko_NewCSSValueSharedList(len: u32) -> *mut nsCSSValueSharedList;
 }
+extern "C" {
+    pub fn Gecko_NewNoneTransform() -> *mut nsCSSValueSharedList;
+}
 extern "C" {
     pub fn Gecko_CSSValue_GetArrayItem(css_value: nsCSSValueBorrowedMut,
                                        index: i32) -> nsCSSValueBorrowedMut;
@@ -1363,6 +1376,10 @@ 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 +2093,14 @@ 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,