Switch from `Rc` to `Arc`

44 files changed, 218 insertions, 214 deletions

diff --git a/src/eval/array.rs b/src/eval/array.rs
index 912aa3c0..45f6fcc7 100644
--- a/src/eval/array.rs
+++ b/src/eval/array.rs
@@ -3,11 +3,11 @@ use std::convert::TryFrom;
 use std::fmt::{self, Debug, Formatter, Write};
 use std::iter::FromIterator;
 use std::ops::{Add, AddAssign};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::Value;
 use crate::diag::StrResult;
-use crate::util::RcExt;
+use crate::util::ArcExt;
 
 /// Create a new [`Array`] from values.
 #[allow(unused_macros)]
@@ -23,7 +23,7 @@ macro_rules! array {
 
 /// An array of values with clone-on-write value semantics.
 #[derive(Default, Clone, PartialEq)]
-pub struct Array(Rc<Vec<Value>>);
+pub struct Array(Arc<Vec<Value>>);
 
 impl Array {
     /// Create a new, empty array.
@@ -33,7 +33,7 @@ impl Array {
 
     /// Create a new array from a vector of values.
     pub fn from_vec(vec: Vec<Value>) -> Self {
-        Self(Rc::new(vec))
+        Self(Arc::new(vec))
     }
 
     /// Whether the array is empty.
@@ -59,19 +59,19 @@ impl Array {
         let len = self.len();
         usize::try_from(index)
             .ok()
-            .and_then(move |i| Rc::make_mut(&mut self.0).get_mut(i))
+            .and_then(move |i| Arc::make_mut(&mut self.0).get_mut(i))
             .ok_or_else(|| out_of_bounds(index, len))
     }
 
     /// Push a value to the end of the array.
     pub fn push(&mut self, value: Value) {
-        Rc::make_mut(&mut self.0).push(value);
+        Arc::make_mut(&mut self.0).push(value);
     }
 
     /// Clear the array.
     pub fn clear(&mut self) {
-        if Rc::strong_count(&self.0) == 1 {
-            Rc::make_mut(&mut self.0).clear();
+        if Arc::strong_count(&self.0) == 1 {
+            Arc::make_mut(&mut self.0).clear();
         } else {
             *self = Self::new();
         }
@@ -87,7 +87,7 @@ impl Array {
     /// Returns an error if two values could not be compared.
     pub fn sorted(mut self) -> StrResult<Self> {
         let mut result = Ok(());
-        Rc::make_mut(&mut self.0).sort_by(|a, b| {
+        Arc::make_mut(&mut self.0).sort_by(|a, b| {
             a.partial_cmp(b).unwrap_or_else(|| {
                 if result.is_ok() {
                     result = Err(format!(
@@ -146,7 +146,7 @@ impl Add for Array {
 
 impl AddAssign for Array {
     fn add_assign(&mut self, rhs: Array) {
-        match Rc::try_unwrap(rhs.0) {
+        match Arc::try_unwrap(rhs.0) {
             Ok(vec) => self.extend(vec),
             Err(rc) => self.extend(rc.iter().cloned()),
         }
@@ -155,13 +155,13 @@ impl AddAssign for Array {
 
 impl Extend<Value> for Array {
     fn extend<T: IntoIterator<Item = Value>>(&mut self, iter: T) {
-        Rc::make_mut(&mut self.0).extend(iter);
+        Arc::make_mut(&mut self.0).extend(iter);
     }
 }
 
 impl FromIterator<Value> for Array {
     fn from_iter<T: IntoIterator<Item = Value>>(iter: T) -> Self {
-        Self(Rc::new(iter.into_iter().collect()))
+        Self(Arc::new(iter.into_iter().collect()))
     }
 }
 
@@ -170,7 +170,7 @@ impl IntoIterator for Array {
     type IntoIter = std::vec::IntoIter<Value>;
 
     fn into_iter(self) -> Self::IntoIter {
-        Rc::take(self.0).into_iter()
+        Arc::take(self.0).into_iter()
     }
 }
 
diff --git a/src/eval/capture.rs b/src/eval/capture.rs
index e47831df..8585776a 100644
--- a/src/eval/capture.rs
+++ b/src/eval/capture.rs
@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::{Scope, Scopes, Value};
 use crate::syntax::ast::{ClosureParam, Expr, Ident, Imports, TypedNode};
@@ -35,7 +35,7 @@ impl<'a> CapturesVisitor<'a> {
     pub fn capture(&mut self, ident: Ident) {
         if self.internal.get(&ident).is_none() {
             if let Some(slot) = self.external.get(&ident) {
-                self.captures.def_slot(ident.take(), Rc::clone(slot));
+                self.captures.def_slot(ident.take(), Arc::clone(slot));
             }
         }
     }
diff --git a/src/eval/dict.rs b/src/eval/dict.rs
index 0d7198e1..2ce3c3f9 100644
--- a/src/eval/dict.rs
+++ b/src/eval/dict.rs
@@ -2,11 +2,11 @@ use std::collections::BTreeMap;
 use std::fmt::{self, Debug, Formatter, Write};
 use std::iter::FromIterator;
 use std::ops::{Add, AddAssign};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::Value;
 use crate::diag::StrResult;
-use crate::util::{EcoString, RcExt};
+use crate::util::{ArcExt, EcoString};
 
 /// Create a new [`Dict`] from key-value pairs.
 #[allow(unused_macros)]
@@ -21,7 +21,7 @@ macro_rules! dict {
 
 /// A dictionary from strings to values with clone-on-write value semantics.
 #[derive(Default, Clone, PartialEq)]
-pub struct Dict(Rc<BTreeMap<EcoString, Value>>);
+pub struct Dict(Arc<BTreeMap<EcoString, Value>>);
 
 impl Dict {
     /// Create a new, empty dictionary.
@@ -31,7 +31,7 @@ impl Dict {
 
     /// Create a new dictionary from a mapping of strings to values.
     pub fn from_map(map: BTreeMap<EcoString, Value>) -> Self {
-        Self(Rc::new(map))
+        Self(Arc::new(map))
     }
 
     /// Whether the dictionary is empty.
@@ -54,18 +54,18 @@ impl Dict {
     /// This inserts the key with [`None`](Value::None) as the value if not
     /// present so far.
     pub fn get_mut(&mut self, key: EcoString) -> &mut Value {
-        Rc::make_mut(&mut self.0).entry(key).or_default()
+        Arc::make_mut(&mut self.0).entry(key).or_default()
     }
 
     /// Insert a mapping from the given `key` to the given `value`.
     pub fn insert(&mut self, key: EcoString, value: Value) {
-        Rc::make_mut(&mut self.0).insert(key, value);
+        Arc::make_mut(&mut self.0).insert(key, value);
     }
 
     /// Clear the dictionary.
     pub fn clear(&mut self) {
-        if Rc::strong_count(&self.0) == 1 {
-            Rc::make_mut(&mut self.0).clear();
+        if Arc::strong_count(&self.0) == 1 {
+            Arc::make_mut(&mut self.0).clear();
         } else {
             *self = Self::new();
         }
@@ -112,7 +112,7 @@ impl Add for Dict {
 
 impl AddAssign for Dict {
     fn add_assign(&mut self, rhs: Dict) {
-        match Rc::try_unwrap(rhs.0) {
+        match Arc::try_unwrap(rhs.0) {
             Ok(map) => self.extend(map),
             Err(rc) => self.extend(rc.iter().map(|(k, v)| (k.clone(), v.clone()))),
         }
@@ -121,13 +121,13 @@ impl AddAssign for Dict {
 
 impl Extend<(EcoString, Value)> for Dict {
     fn extend<T: IntoIterator<Item = (EcoString, Value)>>(&mut self, iter: T) {
-        Rc::make_mut(&mut self.0).extend(iter);
+        Arc::make_mut(&mut self.0).extend(iter);
     }
 }
 
 impl FromIterator<(EcoString, Value)> for Dict {
     fn from_iter<T: IntoIterator<Item = (EcoString, Value)>>(iter: T) -> Self {
-        Self(Rc::new(iter.into_iter().collect()))
+        Self(Arc::new(iter.into_iter().collect()))
     }
 }
 
@@ -136,7 +136,7 @@ impl IntoIterator for Dict {
     type IntoIter = std::collections::btree_map::IntoIter<EcoString, Value>;
 
     fn into_iter(self) -> Self::IntoIter {
-        Rc::take(self.0).into_iter()
+        Arc::take(self.0).into_iter()
     }
 }
 
diff --git a/src/eval/function.rs b/src/eval/function.rs
index 931a90a0..0edc1e78 100644
--- a/src/eval/function.rs
+++ b/src/eval/function.rs
@@ -1,5 +1,5 @@
 use std::fmt::{self, Debug, Formatter, Write};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::{Cast, EvalContext, Value};
 use crate::diag::{At, TypResult};
@@ -8,9 +8,9 @@ use crate::util::EcoString;
 
 /// An evaluatable function.
 #[derive(Clone)]
-pub struct Function(Rc<Inner<Func>>);
+pub struct Function(Arc<Inner<Func>>);
 
-/// The unsized structure behind the [`Rc`].
+/// The unsized structure behind the [`Arc`].
 struct Inner<T: ?Sized> {
     name: Option<EcoString>,
     func: T,
@@ -24,7 +24,7 @@ impl Function {
     where
         F: Fn(&mut EvalContext, &mut Args) -> TypResult<Value> + 'static,
     {
-        Self(Rc::new(Inner { name, func }))
+        Self(Arc::new(Inner { name, func }))
     }
 
     /// The name of the function.
@@ -53,8 +53,8 @@ impl PartialEq for Function {
     fn eq(&self, other: &Self) -> bool {
         // We cast to thin pointers for comparison.
         std::ptr::eq(
-            Rc::as_ptr(&self.0) as *const (),
-            Rc::as_ptr(&other.0) as *const (),
+            Arc::as_ptr(&self.0) as *const (),
+            Arc::as_ptr(&other.0) as *const (),
         )
     }
 }
diff --git a/src/eval/node.rs b/src/eval/node.rs
index d909fc7d..665550b0 100644
--- a/src/eval/node.rs
+++ b/src/eval/node.rs
@@ -71,7 +71,7 @@ impl Node {
     /// Create an inline-level node.
     pub fn inline<T>(node: T) -> Self
     where
-        T: Layout + Debug + Hash + 'static,
+        T: Layout + Debug + Hash + Sync + Send + 'static,
     {
         Self::Inline(node.pack())
     }
@@ -79,7 +79,7 @@ impl Node {
     /// Create a block-level node.
     pub fn block<T>(node: T) -> Self
     where
-        T: Layout + Debug + Hash + 'static,
+        T: Layout + Debug + Hash + Sync + Send + 'static,
     {
         Self::Block(node.pack())
     }
diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index 5178c819..34da68d4 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -2,14 +2,14 @@ use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
 use std::iter;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::{Args, Class, Construct, EvalContext, Function, Set, Value};
 use crate::diag::TypResult;
 use crate::util::EcoString;
 
 /// A slot where a variable is stored.
-pub type Slot = Rc<RefCell<Value>>;
+pub type Slot = Arc<RefCell<Value>>;
 
 /// A stack of scopes.
 #[derive(Debug, Default, Clone)]
@@ -85,12 +85,12 @@ impl Scope {
         // FIXME: Use Ref::leak once stable.
         std::mem::forget(cell.borrow());
 
-        self.values.insert(var.into(), Rc::new(cell));
+        self.values.insert(var.into(), Arc::new(cell));
     }
 
     /// Define a mutable variable with a value.
     pub fn def_mut(&mut self, var: impl Into<EcoString>, value: impl Into<Value>) {
-        self.values.insert(var.into(), Rc::new(RefCell::new(value.into())));
+        self.values.insert(var.into(), Arc::new(RefCell::new(value.into())));
     }
 
     /// Define a variable with a slot.
diff --git a/src/eval/styles.rs b/src/eval/styles.rs
index 508996a1..5276353a 100644
--- a/src/eval/styles.rs
+++ b/src/eval/styles.rs
@@ -1,7 +1,7 @@
 use std::any::{Any, TypeId};
 use std::fmt::{self, Debug, Formatter};
 use std::hash::{Hash, Hasher};
-use std::rc::Rc;
+use std::sync::Arc;
 
 // TODO(style): Possible optimizations:
 // - Ref-count map for cheaper cloning and smaller footprint
@@ -334,13 +334,13 @@ impl Debug for Link<'_> {
 /// An entry for a single style property.
 #[derive(Clone)]
 struct Entry {
-    p: Rc<dyn Bounds>,
+    p: Arc<dyn Bounds>,
     scoped: bool,
 }
 
 impl Entry {
     fn new<P: Property>(key: P, value: P::Value) -> Self {
-        Self { p: Rc::new((key, value)), scoped: false }
+        Self { p: Arc::new((key, value)), scoped: false }
     }
 
     fn is<P: Property>(&self) -> bool {
@@ -390,11 +390,11 @@ impl Hash for Entry {
 ///
 /// This trait is not intended to be implemented manually, but rather through
 /// the `#[properties]` proc-macro.
-pub trait Property: Copy + 'static {
+pub trait Property: Copy + Sync + Send + 'static {
     /// The type of value that is returned when getting this property from a
     /// style map. For example, this could be [`Length`](crate::geom::Length)
     /// for a `WIDTH` property.
-    type Value: Debug + Clone + PartialEq + Hash + 'static;
+    type Value: Debug + Clone + PartialEq + Hash + Sync + Send + 'static;
 
     /// The name of the property, used for debug printing.
     const NAME: &'static str;
@@ -432,7 +432,7 @@ pub trait Nonfolding {}
 /// value types below. Although it is zero-sized, the property `P` must be part
 /// of the implementing type so that we can use it in the methods (it must be a
 /// constrained type parameter).
-trait Bounds: 'static {
+trait Bounds: Sync + Send + 'static {
     fn as_any(&self) -> &dyn Any;
     fn dyn_fmt(&self, f: &mut Formatter) -> fmt::Result;
     fn dyn_eq(&self, other: &Entry) -> bool;
diff --git a/src/eval/value.rs b/src/eval/value.rs
index e64f6cc6..7d65d5af 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -2,7 +2,7 @@ use std::any::Any;
 use std::cmp::Ordering;
 use std::fmt::{self, Debug, Formatter};
 use std::hash::Hash;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::{ops, Args, Array, Class, Dict, Function, Node};
 use crate::diag::StrResult;
@@ -58,7 +58,7 @@ impl Value {
     /// Create an inline-level node value.
     pub fn inline<T>(node: T) -> Self
     where
-        T: Layout + Debug + Hash + 'static,
+        T: Layout + Debug + Hash + Sync + Send + 'static,
     {
         Self::Node(Node::inline(node))
     }
@@ -66,7 +66,7 @@ impl Value {
     /// Create a block-level node value.
     pub fn block<T>(node: T) -> Self
     where
-        T: Layout + Debug + Hash + 'static,
+        T: Layout + Debug + Hash + Sync + Send + 'static,
     {
         Self::Node(Node::block(node))
     }
@@ -211,15 +211,15 @@ impl From<Dynamic> for Value {
 
 /// A dynamic value.
 #[derive(Clone)]
-pub struct Dynamic(Rc<dyn Bounds>);
+pub struct Dynamic(Arc<dyn Bounds>);
 
 impl Dynamic {
     /// Create a new instance from any value that satisifies the required bounds.
     pub fn new<T>(any: T) -> Self
     where
-        T: Type + Debug + PartialEq + 'static,
+        T: Type + Debug + PartialEq + Sync + Send + 'static,
     {
-        Self(Rc::new(any))
+        Self(Arc::new(any))
     }
 
     /// Whether the wrapped type is `T`.
@@ -250,7 +250,7 @@ impl PartialEq for Dynamic {
     }
 }
 
-trait Bounds: Debug + 'static {
+trait Bounds: Debug + Sync + Send + 'static {
     fn as_any(&self) -> &dyn Any;
     fn dyn_eq(&self, other: &Dynamic) -> bool;
     fn dyn_type_name(&self) -> &'static str;
@@ -258,7 +258,7 @@ trait Bounds: Debug + 'static {
 
 impl<T> Bounds for T
 where
-    T: Type + Debug + PartialEq + 'static,
+    T: Type + Debug + PartialEq + Sync + Send + 'static,
 {
     fn as_any(&self) -> &dyn Any {
         self
diff --git a/src/export/pdf.rs b/src/export/pdf.rs
index 1477e283..19134f99 100644
--- a/src/export/pdf.rs
+++ b/src/export/pdf.rs
@@ -3,7 +3,7 @@
 use std::cmp::Eq;
 use std::collections::{BTreeMap, HashMap, HashSet};
 use std::hash::Hash;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use image::{DynamicImage, GenericImageView, ImageFormat, ImageResult, Rgba};
 use pdf_writer::types::{
@@ -26,7 +26,7 @@ use crate::Context;
 /// included in the PDF.
 ///
 /// Returns the raw bytes making up the PDF file.
-pub fn pdf(ctx: &Context, frames: &[Rc<Frame>]) -> Vec<u8> {
+pub fn pdf(ctx: &Context, frames: &[Arc<Frame>]) -> Vec<u8> {
     PdfExporter::new(ctx).export(frames)
 }
 
@@ -60,14 +60,14 @@ impl<'a> PdfExporter<'a> {
         }
     }
 
-    fn export(mut self, frames: &[Rc<Frame>]) -> Vec<u8> {
+    fn export(mut self, frames: &[Arc<Frame>]) -> Vec<u8> {
         self.build_pages(frames);
         self.write_fonts();
         self.write_images();
         self.write_structure()
     }
 
-    fn build_pages(&mut self, frames: &[Rc<Frame>]) {
+    fn build_pages(&mut self, frames: &[Arc<Frame>]) {
         for frame in frames {
             let page = PageExporter::new(self).export(frame);
             self.pages.push(page);
diff --git a/src/font.rs b/src/font.rs
index 674ffa63..45cc6be2 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -3,7 +3,7 @@
 use std::collections::{hash_map::Entry, BTreeMap, HashMap};
 use std::fmt::{self, Debug, Formatter};
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use serde::{Deserialize, Serialize};
 use ttf_parser::{name_id, GlyphId, PlatformId};
@@ -33,15 +33,15 @@ impl FaceId {
 
 /// Storage for loaded and parsed font faces.
 pub struct FontStore {
-    loader: Rc<dyn Loader>,
+    loader: Arc<dyn Loader>,
     faces: Vec<Option<Face>>,
     families: BTreeMap<String, Vec<FaceId>>,
-    buffers: HashMap<FileHash, Rc<Vec<u8>>>,
+    buffers: HashMap<FileHash, Arc<Vec<u8>>>,
 }
 
 impl FontStore {
     /// Create a new, empty font store.
-    pub fn new(loader: Rc<dyn Loader>) -> Self {
+    pub fn new(loader: Arc<dyn Loader>) -> Self {
         let mut faces = vec![];
         let mut families = BTreeMap::<String, Vec<FaceId>>::new();
 
@@ -109,11 +109,11 @@ impl FontStore {
                 Entry::Occupied(entry) => entry.into_mut(),
                 Entry::Vacant(entry) => {
                     let buffer = self.loader.load(path).ok()?;
-                    entry.insert(Rc::new(buffer))
+                    entry.insert(Arc::new(buffer))
                 }
             };
 
-            let face = Face::new(Rc::clone(buffer), index)?;
+            let face = Face::new(Arc::clone(buffer), index)?;
             *slot = Some(face);
         }
 
@@ -147,7 +147,7 @@ pub struct Face {
     /// The raw face data, possibly shared with other faces from the same
     /// collection. Must stay alive put, because `ttf` points into it using
     /// unsafe code.
-    buffer: Rc<Vec<u8>>,
+    buffer: Arc<Vec<u8>>,
     /// The face's index in the collection (zero if not a collection).
     index: u32,
     /// The underlying ttf-parser/rustybuzz face.
@@ -182,11 +182,11 @@ pub struct LineMetrics {
 
 impl Face {
     /// Parse a font face from a buffer and collection index.
-    pub fn new(buffer: Rc<Vec<u8>>, index: u32) -> Option<Self> {
+    pub fn new(buffer: Arc<Vec<u8>>, index: u32) -> Option<Self> {
         // Safety:
         // - The slices's location is stable in memory:
         //   - We don't move the underlying vector
-        //   - Nobody else can move it since we have a strong ref to the `Rc`.
+        //   - Nobody else can move it since we have a strong ref to the `Arc`.
         // - The internal static lifetime is not leaked because its rewritten
         //   to the self-lifetime in `ttf()`.
         let slice: &'static [u8] =
@@ -238,7 +238,7 @@ impl Face {
     }
 
     /// The underlying buffer.
-    pub fn buffer(&self) -> &Rc<Vec<u8>> {
+    pub fn buffer(&self) -> &Arc<Vec<u8>> {
         &self.buffer
     }
 
diff --git a/src/frame.rs b/src/frame.rs
index 133ba256..f714fbbe 100644
--- a/src/frame.rs
+++ b/src/frame.rs
@@ -1,7 +1,7 @@
 //! Finished layouts.
 
 use std::fmt::{self, Debug, Formatter};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::font::FaceId;
 use crate::geom::{Align, Em, Length, Paint, Path, Point, Size, Spec, Transform};
@@ -43,7 +43,7 @@ impl Frame {
     }
 
     /// Add a group element.
-    pub fn push_frame(&mut self, pos: Point, frame: Rc<Self>) {
+    pub fn push_frame(&mut self, pos: Point, frame: Arc<Self>) {
         self.elements.push((pos, Element::Group(Group::new(frame))));
     }
 
@@ -100,7 +100,7 @@ impl Frame {
         F: FnOnce(&mut Group),
     {
         let mut wrapper = Frame { elements: vec![], ..*self };
-        let mut group = Group::new(Rc::new(std::mem::take(self)));
+        let mut group = Group::new(Arc::new(std::mem::take(self)));
         f(&mut group);
         wrapper.push(Point::zero(), Element::Group(group));
         *self = wrapper;
@@ -149,7 +149,7 @@ pub enum Element {
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Group {
     /// The group's frame.
-    pub frame: Rc<Frame>,
+    pub frame: Arc<Frame>,
     /// A transformation to apply to the group.
     pub transform: Transform,
     /// Whether the frame should be a clipping boundary.
@@ -158,7 +158,7 @@ pub struct Group {
 
 impl Group {
     /// Create a new group with default settings.
-    pub fn new(frame: Rc<Frame>) -> Self {
+    pub fn new(frame: Arc<Frame>) -> Self {
         Self {
             frame,
             transform: Transform::identity(),
diff --git a/src/image.rs b/src/image.rs
index bd70bf28..24a0deec 100644
--- a/src/image.rs
+++ b/src/image.rs
@@ -5,7 +5,7 @@ use std::ffi::OsStr;
 use std::fmt::{self, Debug, Formatter};
 use std::io;
 use std::path::Path;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use image::io::Reader as ImageReader;
 use image::{DynamicImage, GenericImageView, ImageFormat};
@@ -33,14 +33,14 @@ impl ImageId {
 
 /// Storage for loaded and decoded images.
 pub struct ImageStore {
-    loader: Rc<dyn Loader>,
+    loader: Arc<dyn Loader>,
     files: HashMap<FileHash, ImageId>,
     images: Vec<Image>,
 }
 
 impl ImageStore {
     /// Create a new, empty image store.
-    pub fn new(loader: Rc<dyn Loader>) -> Self {
+    pub fn new(loader: Arc<dyn Loader>) -> Self {
         Self {
             loader,
             files: HashMap::new(),
diff --git a/src/layout/constraints.rs b/src/layout/constraints.rs
index 0d772cea..3bdbc4bc 100644
--- a/src/layout/constraints.rs
+++ b/src/layout/constraints.rs
@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::Regions;
 use crate::frame::Frame;
@@ -7,12 +7,12 @@ use crate::geom::{Length, Size, Spec};
 /// Constrain a frame with constraints.
 pub trait Constrain {
     /// Reference-count the frame and wrap it with constraints.
-    fn constrain(self, cts: Constraints) -> Constrained<Rc<Frame>>;
+    fn constrain(self, cts: Constraints) -> Constrained<Arc<Frame>>;
 }
 
 impl Constrain for Frame {
-    fn constrain(self, cts: Constraints) -> Constrained<Rc<Frame>> {
-        Constrained::new(Rc::new(self), cts)
+    fn constrain(self, cts: Constraints) -> Constrained<Arc<Frame>> {
+        Constrained::new(Arc::new(self), cts)
     }
 }
 
diff --git a/src/layout/incremental.rs b/src/layout/incremental.rs
index 63915b53..2112fef1 100644
--- a/src/layout/incremental.rs
+++ b/src/layout/incremental.rs
@@ -1,6 +1,6 @@
 use std::cmp::Reverse;
 use std::collections::HashMap;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use itertools::Itertools;
 
@@ -65,7 +65,7 @@ impl LayoutCache {
         &mut self,
         hash: u64,
         regions: &Regions,
-    ) -> Option<Vec<Constrained<Rc<Frame>>>> {
+    ) -> Option<Vec<Constrained<Arc<Frame>>>> {
         self.frames
             .get_mut(&hash)?
             .iter_mut()
@@ -193,7 +193,7 @@ impl LayoutCache {
 #[derive(Debug, Clone)]
 pub struct FramesEntry {
     /// The cached frames for a node.
-    frames: Vec<Constrained<Rc<Frame>>>,
+    frames: Vec<Constrained<Arc<Frame>>>,
     /// How nested the frame was in the context is was originally appearing in.
     level: usize,
     /// For how long the element already exists.
@@ -209,7 +209,7 @@ pub struct FramesEntry {
 
 impl FramesEntry {
     /// Construct a new instance.
-    pub fn new(frames: Vec<Constrained<Rc<Frame>>>, level: usize) -> Self {
+    pub fn new(frames: Vec<Constrained<Arc<Frame>>>, level: usize) -> Self {
         Self {
             frames,
             level,
@@ -222,7 +222,7 @@ impl FramesEntry {
 
     /// Checks if the cached frames are valid in the given regions and returns
     /// them if so.
-    pub fn lookup(&mut self, regions: &Regions) -> Option<Vec<Constrained<Rc<Frame>>>> {
+    pub fn lookup(&mut self, regions: &Regions) -> Option<Vec<Constrained<Arc<Frame>>>> {
         self.check(regions).then(|| {
             self.temperature[0] = self.temperature[0].saturating_add(1);
             self.frames.clone()
@@ -396,9 +396,9 @@ mod tests {
     use crate::geom::{Size, Spec};
     use crate::layout::Constraints;
 
-    fn empty_frames() -> Vec<Constrained<Rc<Frame>>> {
+    fn empty_frames() -> Vec<Constrained<Arc<Frame>>> {
         vec![Constrained {
-            item: Rc::new(Frame::default()),
+            item: Arc::new(Frame::default()),
             cts: Constraints::new(Spec::splat(false)),
         }]
     }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index e4c29f9b..147e8c9d 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -13,7 +13,7 @@ pub use regions::*;
 use std::any::Any;
 use std::fmt::{self, Debug, Formatter};
 use std::hash::{Hash, Hasher};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::eval::{StyleChain, Styled};
 use crate::font::FontStore;
@@ -29,7 +29,7 @@ pub struct RootNode(pub Vec<Styled<PageNode>>);
 
 impl RootNode {
     /// Layout the document into a sequence of frames, one per page.
-    pub fn layout(&self, ctx: &mut Context) -> Vec<Rc<Frame>> {
+    pub fn layout(&self, ctx: &mut Context) -> Vec<Arc<Frame>> {
         let (mut ctx, styles) = LayoutContext::new(ctx);
         self.0
             .iter()
@@ -56,17 +56,17 @@ pub trait Layout {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>>;
+    ) -> Vec<Constrained<Arc<Frame>>>;
 
     /// Convert to a packed node.
     fn pack(self) -> PackedNode
     where
-        Self: Debug + Hash + Sized + 'static,
+        Self: Debug + Hash + Sized + Sync + Send + 'static,
     {
         PackedNode {
             #[cfg(feature = "layout-cache")]
             hash: self.hash64(),
-            node: Rc::new(self),
+            node: Arc::new(self),
         }
     }
 }
@@ -112,7 +112,7 @@ impl Layout for EmptyNode {
         _: &mut LayoutContext,
         regions: &Regions,
         _: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let size = regions.expand.select(regions.current, Size::zero());
         let mut cts = Constraints::new(regions.expand);
         cts.exact = regions.current.filter(regions.expand);
@@ -124,7 +124,7 @@ impl Layout for EmptyNode {
 #[derive(Clone)]
 pub struct PackedNode {
     /// The type-erased node.
-    node: Rc<dyn Bounds>,
+    node: Arc<dyn Bounds>,
     /// A precomputed hash for the node.
     #[cfg(feature = "layout-cache")]
     hash: u64,
@@ -205,7 +205,7 @@ impl Layout for PackedNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let styles = styles.barred(self.node.as_any().type_id());
 
         #[cfg(not(feature = "layout-cache"))]
@@ -243,10 +243,7 @@ impl Layout for PackedNode {
         })
     }
 
-    fn pack(self) -> PackedNode
-    where
-        Self: Sized + Hash + 'static,
-    {
+    fn pack(self) -> PackedNode {
         self
     }
 }
@@ -266,8 +263,8 @@ impl Debug for PackedNode {
 impl PartialEq for PackedNode {
     fn eq(&self, other: &Self) -> bool {
         std::ptr::eq(
-            Rc::as_ptr(&self.node) as *const (),
-            Rc::as_ptr(&other.node) as *const (),
+            Arc::as_ptr(&self.node) as *const (),
+            Arc::as_ptr(&other.node) as *const (),
         )
     }
 }
@@ -282,14 +279,14 @@ impl Hash for PackedNode {
     }
 }
 
-trait Bounds: Layout + Debug + 'static {
+trait Bounds: Layout + Debug + Sync + Send + 'static {
     fn as_any(&self) -> &dyn Any;
     fn hash64(&self) -> u64;
 }
 
 impl<T> Bounds for T
 where
-    T: Layout + Hash + Debug + 'static,
+    T: Layout + Hash + Debug + Sync + Send + 'static,
 {
     fn as_any(&self) -> &dyn Any {
         self
@@ -320,7 +317,7 @@ impl Layout for SizedNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let is_auto = self.sizing.map_is_none();
         let is_rel = self.sizing.map(|s| s.map_or(false, Linear::is_relative));
 
@@ -346,7 +343,7 @@ impl Layout for SizedNode {
 
         // Ensure frame size matches regions size if expansion is on.
         let target = regions.expand.select(regions.current, frame.size);
-        Rc::make_mut(frame).resize(target, Align::LEFT_TOP);
+        Arc::make_mut(frame).resize(target, Align::LEFT_TOP);
 
         // Set base & exact constraints if the child is automatically sized
         // since we don't know what the child might have done. Also set base if
@@ -374,11 +371,11 @@ impl Layout for FillNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let mut frames = self.child.layout(ctx, regions, styles);
         for Constrained { item: frame, .. } in &mut frames {
             let shape = Shape::filled(Geometry::Rect(frame.size), self.fill);
-            Rc::make_mut(frame).prepend(Point::zero(), Element::Shape(shape));
+            Arc::make_mut(frame).prepend(Point::zero(), Element::Shape(shape));
         }
         frames
     }
@@ -399,11 +396,11 @@ impl Layout for StrokeNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let mut frames = self.child.layout(ctx, regions, styles);
         for Constrained { item: frame, .. } in &mut frames {
             let shape = Shape::stroked(Geometry::Rect(frame.size), self.stroke);
-            Rc::make_mut(frame).prepend(Point::zero(), Element::Shape(shape));
+            Arc::make_mut(frame).prepend(Point::zero(), Element::Shape(shape));
         }
         frames
     }
diff --git a/src/lib.rs b/src/lib.rs
index a764468b..6d52ceaa 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -52,7 +52,7 @@ pub mod parse;
 pub mod source;
 pub mod syntax;
 
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::diag::TypResult;
 use crate::eval::{Eval, EvalContext, Module, Scope, StyleMap};
@@ -68,7 +68,7 @@ use crate::source::{SourceId, SourceStore};
 /// The core context which holds the loader, configuration and cached artifacts.
 pub struct Context {
     /// The loader the context was created with.
-    pub loader: Rc<dyn Loader>,
+    pub loader: Arc<dyn Loader>,
     /// Stores loaded source files.
     pub sources: SourceStore,
     /// Stores parsed font faces.
@@ -88,7 +88,7 @@ pub struct Context {
 
 impl Context {
     /// Create a new context with the default settings.
-    pub fn new(loader: Rc<dyn Loader>) -> Self {
+    pub fn new(loader: Arc<dyn Loader>) -> Self {
         Self::builder().build(loader)
     }
 
@@ -124,7 +124,7 @@ impl Context {
     /// Returns either a vector of frames representing individual pages or
     /// diagnostics in the form of a vector of error message with file and span
     /// information.
-    pub fn typeset(&mut self, id: SourceId) -> TypResult<Vec<Rc<Frame>>> {
+    pub fn typeset(&mut self, id: SourceId) -> TypResult<Vec<Arc<Frame>>> {
         let module = self.evaluate(id)?;
         let tree = module.into_root();
         let frames = tree.layout(self);
@@ -183,11 +183,11 @@ impl ContextBuilder {
 
     /// Finish building the context by providing the `loader` used to load
     /// fonts, images, source files and other resources.
-    pub fn build(self, loader: Rc<dyn Loader>) -> Context {
+    pub fn build(self, loader: Arc<dyn Loader>) -> Context {
         Context {
-            sources: SourceStore::new(Rc::clone(&loader)),
-            fonts: FontStore::new(Rc::clone(&loader)),
-            images: ImageStore::new(Rc::clone(&loader)),
+            sources: SourceStore::new(Arc::clone(&loader)),
+            fonts: FontStore::new(Arc::clone(&loader)),
+            images: ImageStore::new(Arc::clone(&loader)),
             loader,
             #[cfg(feature = "layout-cache")]
             layout_cache: LayoutCache::new(self.policy, self.max_size),
diff --git a/src/library/align.rs b/src/library/align.rs
index 8eee116e..ecf50cc4 100644
--- a/src/library/align.rs
+++ b/src/library/align.rs
@@ -27,7 +27,7 @@ impl Layout for AlignNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         // The child only needs to expand along an axis if there's no alignment.
         let mut pod = regions.clone();
         pod.expand &= self.aligns.map_is_none();
@@ -49,7 +49,7 @@ impl Layout for AlignNode {
             let target = regions.expand.select(current, frame.size);
             let default = Spec::new(Align::Left, Align::Top);
             let aligns = self.aligns.unwrap_or(default);
-            Rc::make_mut(frame).resize(target, aligns);
+            Arc::make_mut(frame).resize(target, aligns);
 
             // Set constraints.
             cts.expand = regions.expand;
diff --git a/src/library/columns.rs b/src/library/columns.rs
index d2dc350f..149da755 100644
--- a/src/library/columns.rs
+++ b/src/library/columns.rs
@@ -37,7 +37,7 @@ impl Layout for ColumnsNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let columns = self.columns.get();
 
         // Separating the infinite space into infinite columns does not make
diff --git a/src/library/flow.rs b/src/library/flow.rs
index 3405b04a..95426731 100644
--- a/src/library/flow.rs
+++ b/src/library/flow.rs
@@ -18,7 +18,7 @@ impl Layout for FlowNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         FlowLayouter::new(self, regions.clone()).layout(ctx, styles)
     }
 }
@@ -72,7 +72,7 @@ struct FlowLayouter<'a> {
     /// Spacing and layouted nodes.
     items: Vec<FlowItem>,
     /// Finished frames for previous regions.
-    finished: Vec<Constrained<Rc<Frame>>>,
+    finished: Vec<Constrained<Arc<Frame>>>,
 }
 
 /// A prepared item in a flow layout.
@@ -82,9 +82,9 @@ enum FlowItem {
     /// Fractional spacing between other items.
     Fractional(Fractional),
     /// A frame for a layouted child node and how to align it.
-    Frame(Rc<Frame>, Spec<Align>),
+    Frame(Arc<Frame>, Spec<Align>),
     /// An absolutely placed frame.
-    Placed(Rc<Frame>),
+    Placed(Arc<Frame>),
 }
 
 impl<'a> FlowLayouter<'a> {
@@ -113,7 +113,7 @@ impl<'a> FlowLayouter<'a> {
         mut self,
         ctx: &mut LayoutContext,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         for styled in self.children {
             let styles = styled.map.chain(&styles);
             match styled.item {
diff --git a/src/library/grid.rs b/src/library/grid.rs
index 59f52427..c49ac84f 100644
--- a/src/library/grid.rs
+++ b/src/library/grid.rs
@@ -38,7 +38,7 @@ impl Layout for GridNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         // Prepare grid layout by unifying content and gutter tracks.
         let mut layouter = GridLayouter::new(self, regions.clone(), styles);
 
@@ -114,7 +114,7 @@ struct GridLayouter<'a> {
     /// Constraints for the active region.
     cts: Constraints,
     /// Frames for finished regions.
-    finished: Vec<Constrained<Rc<Frame>>>,
+    finished: Vec<Constrained<Arc<Frame>>>,
 }
 
 /// Produced by initial row layout, auto and linear rows are already finished,
@@ -355,7 +355,7 @@ impl<'a> GridLayouter<'a> {
     }
 
     /// Layout the grid row-by-row.
-    fn layout(mut self, ctx: &mut LayoutContext) -> Vec<Constrained<Rc<Frame>>> {
+    fn layout(mut self, ctx: &mut LayoutContext) -> Vec<Constrained<Arc<Frame>>> {
         for y in 0 .. self.rows.len() {
             // Skip to next region if current one is full, but only for content
             // rows, not for gutter rows.
diff --git a/src/library/heading.rs b/src/library/heading.rs
index 4c7bcc7d..17efb5e4 100644
--- a/src/library/heading.rs
+++ b/src/library/heading.rs
@@ -51,7 +51,7 @@ impl Layout for HeadingNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let upscale = (1.6 - 0.1 * self.level as f64).max(0.75);
 
         let mut passed = StyleMap::new();
@@ -82,7 +82,7 @@ impl Layout for HeadingNode {
 
         // FIXME: Constraints and region size.
         for Constrained { item: frame, .. } in &mut frames {
-            let frame = Rc::make_mut(frame);
+            let frame = Arc::make_mut(frame);
             frame.size.y += above + below;
             frame.translate(Point::with_y(above));
         }
diff --git a/src/library/hidden.rs b/src/library/hidden.rs
index 7287bf3d..5025fefb 100644
--- a/src/library/hidden.rs
+++ b/src/library/hidden.rs
@@ -19,12 +19,12 @@ impl Layout for HideNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let mut frames = self.0.layout(ctx, regions, styles);
 
         // Clear the frames.
         for Constrained { item: frame, .. } in &mut frames {
-            *frame = Rc::new(Frame { elements: vec![], ..**frame });
+            *frame = Arc::new(Frame { elements: vec![], ..**frame });
         }
 
         frames
diff --git a/src/library/image.rs b/src/library/image.rs
index a5423ccb..06b3fe31 100644
--- a/src/library/image.rs
+++ b/src/library/image.rs
@@ -44,7 +44,7 @@ impl Layout for ImageNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let img = ctx.images.get(self.0);
         let pxw = img.width() as f64;
         let pxh = img.height() as f64;
diff --git a/src/library/link.rs b/src/library/link.rs
index dc523ffd..0ecd317b 100644
--- a/src/library/link.rs
+++ b/src/library/link.rs
@@ -10,13 +10,14 @@ pub struct LinkNode;
 #[class]
 impl LinkNode {
     fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Node> {
-        let url: String = args.expect::<EcoString>("url")?.into();
+        let url = args.expect::<EcoString>("url")?;
         let body = args.find().unwrap_or_else(|| {
             let mut text = url.as_str();
             for prefix in ["mailto:", "tel:"] {
                 text = text.trim_start_matches(prefix);
             }
-            Node::Text(text.into())
+            let shorter = text.len() < url.len();
+            Node::Text(if shorter { text.into() } else { url.clone() })
         });
 
         Ok(body.styled(TextNode::LINK, Some(url)))
diff --git a/src/library/list.rs b/src/library/list.rs
index 9f742a32..94f7aa44 100644
--- a/src/library/list.rs
+++ b/src/library/list.rs
@@ -39,7 +39,7 @@ impl<L: ListKind> Layout for ListNode<L> {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let em = styles.get(TextNode::SIZE).abs;
         let label_indent = styles.get(Self::LABEL_INDENT).resolve(em);
         let body_indent = styles.get(Self::BODY_INDENT).resolve(em);
@@ -65,7 +65,7 @@ impl<L: ListKind> Layout for ListNode<L> {
 }
 
 /// How to label a list.
-pub trait ListKind: Debug + Default + Hash + 'static {
+pub trait ListKind: Debug + Default + Hash + Sync + Send + 'static {
     /// Return the item's label.
     fn label(&self) -> EcoString;
 }
diff --git a/src/library/mod.rs b/src/library/mod.rs
index 3115cc7a..ae7fc3a1 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -61,7 +61,7 @@ macro_rules! prelude {
 prelude! {
     pub use std::fmt::{self, Debug, Formatter};
     pub use std::num::NonZeroUsize;
-    pub use std::rc::Rc;
+    pub use std::sync::Arc;
     pub use std::hash::Hash;
 
     pub use typst_macros::class;
diff --git a/src/library/pad.rs b/src/library/pad.rs
index 394d3c17..8bfc6d17 100644
--- a/src/library/pad.rs
+++ b/src/library/pad.rs
@@ -37,7 +37,7 @@ impl Layout for PadNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         // Layout child into padded regions.
         let pod = regions.map(|size| shrink(size, self.padding));
         let mut frames = self.child.layout(ctx, &pod, styles);
@@ -52,7 +52,7 @@ impl Layout for PadNode {
             let offset = Point::new(padding.left, padding.top);
 
             // Grow the frame and translate everything in the frame inwards.
-            let frame = Rc::make_mut(frame);
+            let frame = Arc::make_mut(frame);
             frame.size = padded;
             frame.translate(offset);
 
diff --git a/src/library/page.rs b/src/library/page.rs
index f3a287dc..9949e1e7 100644
--- a/src/library/page.rs
+++ b/src/library/page.rs
@@ -70,7 +70,7 @@ impl PageNode {
 
 impl PageNode {
     /// Layout the page run into a sequence of frames, one per page.
-    pub fn layout(&self, ctx: &mut LayoutContext, styles: StyleChain) -> Vec<Rc<Frame>> {
+    pub fn layout(&self, ctx: &mut LayoutContext, styles: StyleChain) -> Vec<Arc<Frame>> {
         // When one of the lengths is infinite the page fits its content along
         // that axis.
         let width = styles.get(Self::WIDTH).unwrap_or(Length::inf());
diff --git a/src/library/par.rs b/src/library/par.rs
index 4f711e76..913d2253 100644
--- a/src/library/par.rs
+++ b/src/library/par.rs
@@ -1,7 +1,7 @@
 //! Paragraph layout.
 
 use std::fmt::{self, Debug, Formatter};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use itertools::Either;
 use unicode_bidi::{BidiInfo, Level};
@@ -9,7 +9,7 @@ use xi_unicode::LineBreakIterator;
 
 use super::prelude::*;
 use super::{shape, ShapedText, SpacingKind, TextNode};
-use crate::util::{EcoString, RangeExt, RcExt, SliceExt};
+use crate::util::{ArcExt, EcoString, RangeExt, SliceExt};
 
 /// A node that arranges its children into a paragraph.
 #[derive(Hash)]
@@ -75,7 +75,7 @@ impl Layout for ParNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         // Collect all text into one string used for BiDi analysis.
         let text = self.collect_text();
 
@@ -253,7 +253,7 @@ impl<'a> ParLayouter<'a> {
                     let size = Size::new(regions.current.x, regions.base.y);
                     let pod = Regions::one(size, regions.base, Spec::splat(false));
                     let frame = node.layout(ctx, &pod, styles).remove(0);
-                    items.push(ParItem::Frame(Rc::take(frame.item)));
+                    items.push(ParItem::Frame(Arc::take(frame.item)));
                     ranges.push(range);
                 }
             }
@@ -271,7 +271,7 @@ impl<'a> ParLayouter<'a> {
         self,
         ctx: &mut LayoutContext,
         regions: Regions,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let mut stack = LineStack::new(self.leading, regions);
 
         // The current line attempt.
@@ -582,7 +582,7 @@ struct LineStack<'a> {
     regions: Regions,
     size: Size,
     lines: Vec<LineLayout<'a>>,
-    finished: Vec<Constrained<Rc<Frame>>>,
+    finished: Vec<Constrained<Arc<Frame>>>,
     cts: Constraints,
     overflowing: bool,
     fractional: bool,
@@ -650,7 +650,7 @@ impl<'a> LineStack<'a> {
     }
 
     /// Finish the last region and return the built frames.
-    fn finish(mut self, ctx: &LayoutContext) -> Vec<Constrained<Rc<Frame>>> {
+    fn finish(mut self, ctx: &LayoutContext) -> Vec<Constrained<Arc<Frame>>> {
         self.finish_region(ctx);
         self.finished
     }
diff --git a/src/library/place.rs b/src/library/place.rs
index cee687fa..d5880995 100644
--- a/src/library/place.rs
+++ b/src/library/place.rs
@@ -26,7 +26,7 @@ impl Layout for PlaceNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let out_of_flow = self.out_of_flow();
 
         // The pod is the base area of the region because for absolute
@@ -43,7 +43,7 @@ impl Layout for PlaceNode {
         // If expansion is off, zero all sizes so that we don't take up any
         // space in our parent. Otherwise, respect the expand settings.
         let target = regions.expand.select(regions.current, Size::zero());
-        Rc::make_mut(frame).resize(target, Align::LEFT_TOP);
+        Arc::make_mut(frame).resize(target, Align::LEFT_TOP);
 
         // Set base constraint because our pod size is base and exact
         // constraints if we needed to expand or offset.
diff --git a/src/library/shape.rs b/src/library/shape.rs
index 12126ab4..5d31d570 100644
--- a/src/library/shape.rs
+++ b/src/library/shape.rs
@@ -66,7 +66,7 @@ impl<S: ShapeKind> Layout for ShapeNode<S> {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let mut frames;
         if let Some(child) = &self.child {
             let mut padding = styles.get(Self::PADDING);
@@ -118,7 +118,7 @@ impl<S: ShapeKind> Layout for ShapeNode<S> {
             frames = vec![Frame::new(size).constrain(Constraints::tight(regions))];
         }
 
-        let frame = Rc::make_mut(&mut frames[0].item);
+        let frame = Arc::make_mut(&mut frames[0].item);
 
         // Add fill and/or stroke.
         let fill = styles.get(Self::FILL);
@@ -149,7 +149,7 @@ impl<S: ShapeKind> Layout for ShapeNode<S> {
 }
 
 /// Categorizes shapes.
-pub trait ShapeKind: Debug + Default + Hash + 'static {
+pub trait ShapeKind: Debug + Default + Hash + Sync + Send + 'static {
     const ROUND: bool;
     const QUADRATIC: bool;
 }
diff --git a/src/library/stack.rs b/src/library/stack.rs
index 8c8a9f60..14b268c2 100644
--- a/src/library/stack.rs
+++ b/src/library/stack.rs
@@ -31,7 +31,7 @@ impl Layout for StackNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         StackLayouter::new(self, regions.clone(), styles).layout(ctx)
     }
 }
@@ -90,7 +90,7 @@ struct StackLayouter<'a> {
     /// Spacing and layouted nodes.
     items: Vec<StackItem>,
     /// Finished frames for previous regions.
-    finished: Vec<Constrained<Rc<Frame>>>,
+    finished: Vec<Constrained<Arc<Frame>>>,
 }
 
 /// A prepared item in a stack layout.
@@ -100,7 +100,7 @@ enum StackItem {
     /// Fractional spacing between other items.
     Fractional(Fractional),
     /// A layouted child node.
-    Frame(Rc<Frame>, Align),
+    Frame(Arc<Frame>, Align),
 }
 
 impl<'a> StackLayouter<'a> {
@@ -131,7 +131,7 @@ impl<'a> StackLayouter<'a> {
     }
 
     /// Layout all children.
-    fn layout(mut self, ctx: &mut LayoutContext) -> Vec<Constrained<Rc<Frame>>> {
+    fn layout(mut self, ctx: &mut LayoutContext) -> Vec<Constrained<Arc<Frame>>> {
         // Spacing to insert before the next node.
         let mut deferred = None;
 
diff --git a/src/library/table.rs b/src/library/table.rs
index 0e41ad78..d7aa61db 100644
--- a/src/library/table.rs
+++ b/src/library/table.rs
@@ -60,7 +60,7 @@ impl Layout for TableNode {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let primary = styles.get(Self::PRIMARY);
         let secondary = styles.get(Self::SECONDARY);
         let thickness = styles.get(Self::THICKNESS);
diff --git a/src/library/text.rs b/src/library/text.rs
index 6d7be323..c6c1ab80 100644
--- a/src/library/text.rs
+++ b/src/library/text.rs
@@ -55,7 +55,7 @@ impl TextNode {
     #[fold(|a, b| a.into_iter().chain(b).collect())]
     pub const LINES: Vec<Decoration> = vec![];
     /// An URL the text should link to.
-    pub const LINK: Option<String> = None;
+    pub const LINK: Option<EcoString> = None;
 
     /// The size of the glyphs.
     #[fold(Linear::compose)]
@@ -211,12 +211,12 @@ castable! {
 
 /// A specific font family like "Arial".
 #[derive(Clone, Eq, PartialEq, Hash)]
-pub struct NamedFamily(String);
+pub struct NamedFamily(EcoString);
 
 impl NamedFamily {
     /// Create a named font family variant.
     pub fn new(string: &str) -> Self {
-        Self(string.to_lowercase())
+        Self(string.to_lowercase().into())
     }
 
     /// The lowercased family name.
diff --git a/src/library/transform.rs b/src/library/transform.rs
index aceb4197..e9a41a98 100644
--- a/src/library/transform.rs
+++ b/src/library/transform.rs
@@ -36,7 +36,7 @@ impl<T: TransformKind> Layout for TransformNode<T> {
         ctx: &mut LayoutContext,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Rc<Frame>>> {
+    ) -> Vec<Constrained<Arc<Frame>>> {
         let origin = styles.get(Self::ORIGIN).unwrap_or(Align::CENTER_HORIZON);
         let matrix = self.kind.matrix();
 
@@ -48,7 +48,7 @@ impl<T: TransformKind> Layout for TransformNode<T> {
                 .pre_concat(matrix)
                 .pre_concat(Transform::translation(-x, -y));
 
-            Rc::make_mut(frame).transform(transform);
+            Arc::make_mut(frame).transform(transform);
         }
 
         frames
@@ -56,7 +56,7 @@ impl<T: TransformKind> Layout for TransformNode<T> {
 }
 
 /// Kinds of transformations.
-pub trait TransformKind: Debug + Hash + Sized + 'static {
+pub trait TransformKind: Debug + Hash + Sized + Sync + Send + 'static {
     fn construct(args: &mut Args) -> TypResult<Self>;
     fn matrix(&self) -> Transform;
 }
diff --git a/src/loading/fs.rs b/src/loading/fs.rs
index 4c46c80c..3f4a45e1 100644
--- a/src/loading/fs.rs
+++ b/src/loading/fs.rs
@@ -1,7 +1,7 @@
 use std::fs::{self, File};
 use std::io;
 use std::path::Path;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use memmap2::Mmap;
 use same_file::Handle;
@@ -35,10 +35,10 @@ impl FsLoader {
         self
     }
 
-    /// Builder-style method to wrap the loader in an [`Rc`] to make it usable
+    /// Builder-style method to wrap the loader in an [`Arc`] to make it usable
     /// with the [`Context`](crate::Context).
-    pub fn wrap(self) -> Rc<Self> {
-        Rc::new(self)
+    pub fn wrap(self) -> Arc<Self> {
+        Arc::new(self)
     }
 
     /// Search for fonts in the operating system's font directories.
diff --git a/src/loading/mem.rs b/src/loading/mem.rs
index 9ff02d2d..5e3e78d1 100644
--- a/src/loading/mem.rs
+++ b/src/loading/mem.rs
@@ -2,7 +2,7 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 use std::io;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::{FileHash, Loader};
 use crate::font::FaceInfo;
@@ -31,10 +31,10 @@ impl MemLoader {
         self
     }
 
-    /// Builder-style method to wrap the loader in an [`Rc`] to make it usable
+    /// Builder-style method to wrap the loader in an [`Arc`] to make it usable
     /// with the [`Context`](crate::Context).
-    pub fn wrap(self) -> Rc<Self> {
-        Rc::new(self)
+    pub fn wrap(self) -> Arc<Self> {
+        Arc::new(self)
     }
 
     /// Insert a path-file mapping. If the data forms a font, then that font
diff --git a/src/parse/incremental.rs b/src/parse/incremental.rs
index c1da9698..a347f6ca 100644
--- a/src/parse/incremental.rs
+++ b/src/parse/incremental.rs
@@ -1,5 +1,5 @@
 use std::ops::Range;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::syntax::{Green, GreenNode, NodeKind};
 
@@ -78,8 +78,8 @@ impl<'a> Reparser<'a> {
 
 impl Reparser<'_> {
     /// Find the innermost child that is incremental safe.
-    pub fn reparse(&self, green: &mut Rc<GreenNode>) -> Range<usize> {
-        self.reparse_step(Rc::make_mut(green), 0, TokenMode::Markup, true)
+    pub fn reparse(&self, green: &mut Arc<GreenNode>) -> Range<usize> {
+        self.reparse_step(Arc::make_mut(green), 0, TokenMode::Markup, true)
             .unwrap_or_else(|| {
                 *green = parse(self.src);
                 0 .. self.src.len()
@@ -167,7 +167,7 @@ impl Reparser<'_> {
             if last_kind.succession_rule() != SuccessionRule::Unsafe {
                 if let Some(range) = match child {
                     Green::Node(node) => self.reparse_step(
-                        Rc::make_mut(node),
+                        Arc::make_mut(node),
                         first_start,
                         child_mode,
                         outermost,
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 38a08ab8..fbace15b 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -12,14 +12,14 @@ pub use resolve::*;
 pub use scanner::*;
 pub use tokens::*;
 
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::syntax::ast::{Associativity, BinOp, UnOp};
 use crate::syntax::{ErrorPos, Green, GreenNode, NodeKind};
 use crate::util::EcoString;
 
 /// Parse a source file.
-pub fn parse(src: &str) -> Rc<GreenNode> {
+pub fn parse(src: &str) -> Arc<GreenNode> {
     let mut p = Parser::new(src, TokenMode::Markup);
     markup(&mut p, true);
     match p.finish().into_iter().next() {
diff --git a/src/parse/tokens.rs b/src/parse/tokens.rs
index 27da3b80..970c0dd6 100644
--- a/src/parse/tokens.rs
+++ b/src/parse/tokens.rs
@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::sync::Arc;
 
 use super::{
     is_id_continue, is_id_start, is_newline, resolve_hex, resolve_raw, resolve_string,
@@ -321,7 +321,7 @@ impl<'s> Tokens<'s> {
 
         // Special case for empty inline block.
         if backticks == 2 {
-            return NodeKind::Raw(Rc::new(RawNode {
+            return NodeKind::Raw(Arc::new(RawNode {
                 text: EcoString::new(),
                 lang: None,
                 block: false,
@@ -341,7 +341,7 @@ impl<'s> Tokens<'s> {
 
         if found == backticks {
             let end = self.s.index() - found as usize;
-            NodeKind::Raw(Rc::new(resolve_raw(
+            NodeKind::Raw(Arc::new(resolve_raw(
                 column,
                 backticks,
                 self.s.get(start .. end),
@@ -393,7 +393,7 @@ impl<'s> Tokens<'s> {
             };
 
         if terminated {
-            NodeKind::Math(Rc::new(MathNode {
+            NodeKind::Math(Arc::new(MathNode {
                 formula: self.s.get(start .. end).into(),
                 display,
             }))
@@ -581,7 +581,7 @@ mod tests {
     }
 
     fn Raw(text: &str, lang: Option<&str>, block: bool) -> NodeKind {
-        NodeKind::Raw(Rc::new(RawNode {
+        NodeKind::Raw(Arc::new(RawNode {
             text: text.into(),
             lang: lang.map(Into::into),
             block,
@@ -589,7 +589,7 @@ mod tests {
     }
 
     fn Math(formula: &str, display: bool) -> NodeKind {
-        NodeKind::Math(Rc::new(MathNode { formula: formula.into(), display }))
+        NodeKind::Math(Arc::new(MathNode { formula: formula.into(), display }))
     }
 
     fn Str(string: &str) -> NodeKind {
diff --git a/src/source.rs b/src/source.rs
index fd42c3f7..0e7b4c63 100644
--- a/src/source.rs
+++ b/src/source.rs
@@ -4,7 +4,7 @@ use std::collections::HashMap;
 use std::io;
 use std::ops::Range;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::diag::TypResult;
 use crate::loading::{FileHash, Loader};
@@ -37,14 +37,14 @@ impl SourceId {
 
 /// Storage for loaded source files.
 pub struct SourceStore {
-    loader: Rc<dyn Loader>,
+    loader: Arc<dyn Loader>,
     files: HashMap<FileHash, SourceId>,
     sources: Vec<SourceFile>,
 }
 
 impl SourceStore {
     /// Create a new, empty source store.
-    pub fn new(loader: Rc<dyn Loader>) -> Self {
+    pub fn new(loader: Arc<dyn Loader>) -> Self {
         Self {
             loader,
             files: HashMap::new(),
@@ -125,7 +125,7 @@ pub struct SourceFile {
     path: PathBuf,
     src: String,
     lines: Vec<Line>,
-    root: Rc<GreenNode>,
+    root: Arc<GreenNode>,
 }
 
 impl SourceFile {
@@ -148,7 +148,7 @@ impl SourceFile {
     }
 
     /// The root node of the file's untyped green tree.
-    pub fn root(&self) -> &Rc<GreenNode> {
+    pub fn root(&self) -> &Arc<GreenNode> {
         &self.root
     }
 
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 03a496dd..a26384e1 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -7,7 +7,7 @@ mod span;
 
 use std::fmt::{self, Debug, Display, Formatter};
 use std::ops::Range;
-use std::rc::Rc;
+use std::sync::Arc;
 
 pub use highlight::*;
 pub use pretty::*;
@@ -24,7 +24,7 @@ use crate::util::EcoString;
 #[derive(Clone, PartialEq)]
 pub enum Green {
     /// A reference-counted inner node.
-    Node(Rc<GreenNode>),
+    Node(Arc<GreenNode>),
     /// A terminal, owned token.
     Token(GreenData),
 }
@@ -76,7 +76,7 @@ impl Green {
     pub fn convert(&mut self, kind: NodeKind) {
         match self {
             Self::Node(node) => {
-                let node = Rc::make_mut(node);
+                let node = Arc::make_mut(node);
                 node.erroneous |= kind.is_error();
                 node.data.kind = kind;
             }
@@ -187,12 +187,12 @@ impl GreenNode {
 
 impl From<GreenNode> for Green {
     fn from(node: GreenNode) -> Self {
-        Rc::new(node).into()
+        Arc::new(node).into()
     }
 }
 
-impl From<Rc<GreenNode>> for Green {
-    fn from(node: Rc<GreenNode>) -> Self {
+impl From<Arc<GreenNode>> for Green {
+    fn from(node: Arc<GreenNode>) -> Self {
         Self::Node(node)
     }
 }
@@ -259,7 +259,7 @@ pub struct RedNode {
 
 impl RedNode {
     /// Create a new red node from a root [`GreenNode`].
-    pub fn from_root(root: Rc<GreenNode>, id: SourceId) -> Self {
+    pub fn from_root(root: Arc<GreenNode>, id: SourceId) -> Self {
         Self { id, offset: 0, green: root.into() }
     }
 
@@ -611,9 +611,9 @@ pub enum NodeKind {
     Emph,
     /// An arbitrary number of backticks followed by inner contents, terminated
     /// with the same number of backticks: `` `...` ``.
-    Raw(Rc<RawNode>),
+    Raw(Arc<RawNode>),
     /// Dollar signs surrounding inner contents.
-    Math(Rc<MathNode>),
+    Math(Arc<MathNode>),
     /// A section heading: `= Introduction`.
     Heading,
     /// An item in an unordered list: `- ...`.
diff --git a/src/util/eco_string.rs b/src/util/eco_string.rs
index 8cb83377..953508ce 100644
--- a/src/util/eco_string.rs
+++ b/src/util/eco_string.rs
@@ -3,9 +3,9 @@ use std::cmp::Ordering;
 use std::fmt::{self, Debug, Display, Formatter, Write};
 use std::hash::{Hash, Hasher};
 use std::ops::{Add, AddAssign, Deref};
-use std::rc::Rc;
+use std::sync::Arc;
 
-use super::RcExt;
+use super::ArcExt;
 
 /// Create a new [`EcoString`] from a format string.
 macro_rules! format_eco {
@@ -27,13 +27,13 @@ pub struct EcoString(Repr);
 #[derive(Clone)]
 enum Repr {
     Small { buf: [u8; LIMIT], len: u8 },
-    Large(Rc<String>),
+    Large(Arc<String>),
 }
 
 /// The maximum number of bytes that can be stored inline.
 ///
 /// The value is chosen such that an `EcoString` fits exactly into 16 bytes
-/// (which are needed anyway due to the `Rc`s alignment, at least on 64-bit
+/// (which are needed anyway due to the `Arc`s alignment, at least on 64-bit
 /// platforms).
 ///
 /// Must be at least 4 to hold any char.
@@ -50,7 +50,7 @@ impl EcoString {
         if capacity <= LIMIT {
             Self::new()
         } else {
-            Self(Repr::Large(Rc::new(String::with_capacity(capacity))))
+            Self(Repr::Large(Arc::new(String::with_capacity(capacity))))
         }
     }
 
@@ -66,7 +66,7 @@ impl EcoString {
             buf[.. len].copy_from_slice(slice.as_bytes());
             Repr::Small { buf, len: len as u8 }
         } else {
-            Repr::Large(Rc::new(s.into()))
+            Repr::Large(Arc::new(s.into()))
         })
     }
 
@@ -100,7 +100,7 @@ impl EcoString {
                     self.push_str(c.encode_utf8(&mut [0; 4]));
                 }
             }
-            Repr::Large(rc) => Rc::make_mut(rc).push(c),
+            Repr::Large(rc) => Arc::make_mut(rc).push(c),
         }
     }
 
@@ -117,10 +117,10 @@ impl EcoString {
                     let mut spilled = String::with_capacity(new);
                     spilled.push_str(self);
                     spilled.push_str(string);
-                    self.0 = Repr::Large(Rc::new(spilled));
+                    self.0 = Repr::Large(Arc::new(spilled));
                 }
             }
-            Repr::Large(rc) => Rc::make_mut(rc).push_str(string),
+            Repr::Large(rc) => Arc::make_mut(rc).push_str(string),
         }
     }
 
@@ -132,7 +132,7 @@ impl EcoString {
                 *len -= c.len_utf8() as u8;
             }
             Repr::Large(rc) => {
-                Rc::make_mut(rc).pop();
+                Arc::make_mut(rc).pop();
             }
         }
         Some(c)
@@ -143,8 +143,8 @@ impl EcoString {
         match &mut self.0 {
             Repr::Small { len, .. } => *len = 0,
             Repr::Large(rc) => {
-                if Rc::strong_count(rc) == 1 {
-                    Rc::make_mut(rc).clear();
+                if Arc::strong_count(rc) == 1 {
+                    Arc::make_mut(rc).clear();
                 } else {
                     *self = Self::new();
                 }
@@ -351,11 +351,17 @@ impl From<String> for EcoString {
     }
 }
 
+impl From<&EcoString> for String {
+    fn from(s: &EcoString) -> Self {
+        s.as_str().to_owned()
+    }
+}
+
 impl From<EcoString> for String {
     fn from(s: EcoString) -> Self {
         match s.0 {
             Repr::Small { .. } => s.as_str().to_owned(),
-            Repr::Large(rc) => Rc::take(rc),
+            Repr::Large(rc) => Arc::take(rc),
         }
     }
 }
diff --git a/src/util/mod.rs b/src/util/mod.rs
index 61e7131d..de37354e 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -11,7 +11,7 @@ use std::cell::RefMut;
 use std::cmp::Ordering;
 use std::ops::Range;
 use std::path::{Component, Path, PathBuf};
-use std::rc::Rc;
+use std::sync::Arc;
 
 /// Additional methods for strings.
 pub trait StrExt {
@@ -62,18 +62,18 @@ impl<T> OptionExt<T> for Option<T> {
 }
 
 /// Additional methods for reference-counted pointers.
-pub trait RcExt<T> {
+pub trait ArcExt<T> {
     /// Takes the inner value if there is exactly one strong reference and
     /// clones it otherwise.
     fn take(self) -> T;
 }
 
-impl<T> RcExt<T> for Rc<T>
+impl<T> ArcExt<T> for Arc<T>
 where
     T: Clone,
 {
     fn take(self) -> T {
-        match Rc::try_unwrap(self) {
+        match Arc::try_unwrap(self) {
             Ok(v) => v,
             Err(rc) => (*rc).clone(),
         }