The Send impl for `FontContext` is too forgiving.
I'm pretty confident that it is only thread safe if FK is (or another way of putting it is, I'm pretty sure if you include an `Rc<_>` in FK it should not be safe to share between threads).
@@ -56,7 +56,7 @@ pub struct FontContext<FK> where FK: Clone + Hash + Eq + Ord {
}
// Core Text is thread-safe.
-unsafe impl<FK> Send for FontContext<FK> where FK: Clone + Hash + Eq + Ord {}
+unsafe impl<FK> Send for FontContext<FK> where FK: Clone + Hash + Eq + Ord + Send {}
impl<FK> FontContext<FK> where FK: Clone + Hash + Eq + Ord {
/// Creates a new font context instance.
