style: Expose the traversal kind to the style system.

This way we'll be able to take different paths for the sequential and parallel
traversals in some concrete cases.

This is a preliminar patch to fix bug 1332525.
This commit is contained in:
Emilio Cobos Álvarez 2017-01-23 19:55:06 +01:00
parent 7e2329ea4e
commit f00b628c3a
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7 changed files with 64 additions and 13 deletions

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@ -62,6 +62,23 @@ impl LogBehavior {
fn allow(&self) -> bool { matches!(*self, MayLog) }
}
/// The kind of traversals we could perform.
#[derive(Debug, Copy, Clone)]
pub enum TraversalDriver {
/// A potentially parallel traversal.
Parallel,
/// A sequential traversal.
Sequential,
}
impl TraversalDriver {
/// Returns whether this represents a parallel traversal or not.
#[inline]
pub fn is_parallel(&self) -> bool {
matches!(*self, TraversalDriver::Parallel)
}
}
/// A DOM Traversal trait, that is used to generically implement styling for
/// Gecko and Servo.
pub trait DomTraversal<E: TElement> : Sync {
@ -284,6 +301,14 @@ pub trait DomTraversal<E: TElement> : Sync {
/// Creates a thread-local context.
fn create_thread_local_context(&self) -> Self::ThreadLocalContext;
/// Whether we're performing a parallel traversal.
///
/// NB: We do this check on runtime. We could guarantee correctness in this
/// regard via the type system via a `TraversalDriver` trait for this trait,
/// that could be one of two concrete types. It's not clear whether the
/// potential code size impact of that is worth it.
fn is_parallel(&self) -> bool;
}
/// Helper for the function below.