1 files changed, 67 insertions, 0 deletions
diff --git a/servo/components/style/traversal_flags.rs b/servo/components/style/traversal_flags.rs
new file mode 100644
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+++ b/servo/components/style/traversal_flags.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Flags that control the traversal process.
+//!
+//! We CamelCase rather than UPPER_CASING so that we can grep for the same
+//! strings across gecko and servo.
+#![allow(non_upper_case_globals)]
+
+bitflags! {
+    /// Flags that control the traversal process.
+    pub struct TraversalFlags: u32 {
+        /// Traverse only elements for animation restyles.
+        const AnimationOnly = 1 << 0;
+        /// Traverse and update all elements with CSS animations since
+        /// @keyframes rules may have changed. Triggered by CSS rule changes.
+        const ForCSSRuleChanges = 1 << 1;
+        /// The final animation-only traversal, which shouldn't really care about other
+        /// style changes anymore.
+        const FinalAnimationTraversal = 1 << 2;
+        /// Allows the traversal to run in parallel if there are sufficient cores on
+        /// the machine.
+        const ParallelTraversal = 1 << 7;
+        /// Flush throttled animations. By default, we only update throttled animations
+        /// when we have other non-throttled work to do. With this flag, we
+        /// unconditionally tick and process them.
+        const FlushThrottledAnimations = 1 << 8;
+
+    }
+}
+
+/// Asserts that all TraversalFlags flags have a matching ServoTraversalFlags value in gecko.
+#[cfg(feature = "gecko")]
+#[inline]
+pub fn assert_traversal_flags_match() {
+    use crate::gecko_bindings::structs;
+
+    macro_rules! check_traversal_flags {
+        ( $( $a:ident => $b:path ),*, ) => {
+            if cfg!(debug_assertions) {
+                let mut modes = TraversalFlags::all();
+                $(
+                    assert_eq!(structs::$a as usize, $b.bits() as usize, stringify!($b));
+                    modes.remove($b);
+                )*
+                assert_eq!(modes, TraversalFlags::empty(), "all TraversalFlags bits should have an assertion");
+            }
+        }
+    }
+
+    check_traversal_flags! {
+        ServoTraversalFlags_AnimationOnly => TraversalFlags::AnimationOnly,
+        ServoTraversalFlags_ForCSSRuleChanges => TraversalFlags::ForCSSRuleChanges,
+        ServoTraversalFlags_FinalAnimationTraversal => TraversalFlags::FinalAnimationTraversal,
+        ServoTraversalFlags_ParallelTraversal => TraversalFlags::ParallelTraversal,
+        ServoTraversalFlags_FlushThrottledAnimations => TraversalFlags::FlushThrottledAnimations,
+    }
+}
+
+impl TraversalFlags {
+    /// Returns true if the traversal is for animation-only restyles.
+    #[inline]
+    pub fn for_animation_only(&self) -> bool {
+        self.contains(TraversalFlags::AnimationOnly)
+    }
+}