Move and rename many things 🚛

48 files changed, 888 insertions, 926 deletions

diff --git a/bench/src/bench.rs b/bench/src/bench.rs
index 947a02c5..b8093d53 100644
--- a/bench/src/bench.rs
+++ b/bench/src/bench.rs
@@ -33,18 +33,18 @@ fn benchmarks(c: &mut Criterion) {
 
     // Prepare intermediate results and run warm.
     let state = State::default();
-    let tree = parse(COMA).output;
-    let document = eval(&tree, Rc::clone(&env), state.clone()).output;
-    let layouts = layout(&document, Rc::clone(&env));
+    let syntax_tree = parse(COMA).output;
+    let layout_tree = eval(&syntax_tree, Rc::clone(&env), state.clone()).output;
+    let frames = layout(&layout_tree, Rc::clone(&env));
 
     // Bench!
     bench!("parse-coma": parse(COMA));
-    bench!("eval-coma": eval(&tree, Rc::clone(&env), state.clone()));
-    bench!("layout-coma": layout(&document, Rc::clone(&env)));
+    bench!("eval-coma": eval(&syntax_tree, Rc::clone(&env), state.clone()));
+    bench!("layout-coma": layout(&layout_tree, Rc::clone(&env)));
     bench!("typeset-coma": typeset(COMA, Rc::clone(&env), state.clone()));
 
     let env = env.borrow();
-    bench!("export-pdf-coma": pdf::export(&layouts, &env));
+    bench!("export-pdf-coma": pdf::export(&frames, &env));
 }
 
 criterion_group!(benches, benchmarks);
diff --git a/src/diag.rs b/src/diag.rs
index 2872ce5a..a7bea6f1 100644
--- a/src/diag.rs
+++ b/src/diag.rs
@@ -1,8 +1,6 @@
 //! Diagnostics and decorations for source code.
 //!
-//! There are no fatal errors. The document will always compile and yield a
-//! layout on a best effort process, but diagnostics are nevertheless generated
-//! for incorrect things.
+//! Errors are never fatal, the document will always compile and yield a layout.
 
 use crate::syntax::SpanVec;
 use std::fmt::{self, Display, Formatter};
@@ -21,22 +19,9 @@ impl<T> Pass<T> {
     pub fn new(output: T, feedback: Feedback) -> Self {
         Self { output, feedback }
     }
-
-    /// Create a new pass with empty feedback.
-    pub fn okay(output: T) -> Self {
-        Self { output, feedback: Feedback::new() }
-    }
-
-    /// Map the output type and keep the feedback data.
-    pub fn map<U>(self, f: impl FnOnce(T) -> U) -> Pass<U> {
-        Pass {
-            output: f(self.output),
-            feedback: self.feedback,
-        }
-    }
 }
 
-/// Diagnostic and semantic syntax highlighting data.
+/// Diagnostics and semantic syntax highlighting information.
 #[derive(Debug, Default, Clone, Eq, PartialEq)]
 pub struct Feedback {
     /// Diagnostics about the source code.
@@ -64,7 +49,7 @@ impl Feedback {
     }
 }
 
-/// A diagnostic that arose in parsing or layouting.
+/// A diagnostic with severity level and message.
 #[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct Diag {
diff --git a/src/env.rs b/src/env.rs
index a3e14715..58c44a5f 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -42,12 +42,13 @@ impl ResourceLoader {
         Self { paths: HashMap::new(), entries: vec![] }
     }
 
-    /// Load a resource from a path.
-    pub fn load<R: 'static>(
-        &mut self,
-        path: impl AsRef<Path>,
-        parse: impl FnOnce(Vec<u8>) -> Option<R>,
-    ) -> Option<(ResourceId, &R)> {
+    /// Load a resource from a path and parse it.
+    pub fn load<P, F, R>(&mut self, path: P, parse: F) -> Option<(ResourceId, &R)>
+    where
+        P: AsRef<Path>,
+        F: FnOnce(Vec<u8>) -> Option<R>,
+        R: 'static,
+    {
         let path = path.as_ref();
         let id = match self.paths.entry(path.to_owned()) {
             Entry::Occupied(entry) => *entry.get(),
diff --git a/src/eval/args.rs b/src/eval/call.rs
index ea248ec4..186e7630 100644
--- a/src/eval/args.rs
+++ b/src/eval/call.rs
@@ -1,14 +1,37 @@
 use super::*;
+use crate::diag::Deco;
 
-/// Evaluated arguments to a function.
-#[derive(Debug)]
-pub struct Args {
-    span: Span,
-    pos: SpanVec<Value>,
-    named: Vec<(Spanned<String>, Spanned<Value>)>,
+impl Eval for Spanned<&ExprCall> {
+    type Output = Value;
+
+    fn eval(self, ctx: &mut EvalContext) -> Self::Output {
+        let name = &self.v.name.v;
+        let span = self.v.name.span;
+
+        if let Some(value) = ctx.state.scope.get(name) {
+            if let Value::Func(func) = value {
+                let func = func.clone();
+                ctx.deco(Deco::Resolved.with_span(span));
+
+                let mut args = self.v.args.as_ref().eval(ctx);
+                let returned = func(ctx, &mut args);
+                args.finish(ctx);
+
+                return returned;
+            } else {
+                let ty = value.type_name();
+                ctx.diag(error!(span, "a value of type {} is not callable", ty));
+            }
+        } else if !name.is_empty() {
+            ctx.diag(error!(span, "unknown function"));
+        }
+
+        ctx.deco(Deco::Unresolved.with_span(span));
+        Value::Error
+    }
 }
 
-impl Eval for Spanned<&Arguments> {
+impl Eval for Spanned<&ExprArgs> {
     type Output = Args;
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
@@ -33,6 +56,14 @@ impl Eval for Spanned<&Arguments> {
     }
 }
 
+/// Evaluated arguments to a function.
+#[derive(Debug)]
+pub struct Args {
+    span: Span,
+    pos: SpanVec<Value>,
+    named: Vec<(Spanned<String>, Spanned<Value>)>,
+}
+
 impl Args {
     /// Find the first convertible positional argument.
     pub fn find<T>(&mut self, ctx: &mut EvalContext) -> Option<T>
@@ -66,9 +97,8 @@ impl Args {
         self.pos.iter_mut().filter_map(move |slot| try_cast(ctx, slot))
     }
 
-    /// Convert the value for the given named argument.
-    ///
-    /// Generates an error if the conversion fails.
+    /// Convert the value for the given named argument, producing an error if
+    /// the conversion fails.
     pub fn get<'a, T>(&mut self, ctx: &mut EvalContext, name: &str) -> Option<T>
     where
         T: Cast<Spanned<Value>>,
@@ -78,7 +108,7 @@ impl Args {
         cast(ctx, value)
     }
 
-    /// Generate "unexpected argument" errors for all remaining arguments.
+    /// Produce "unexpected argument" errors for all remaining arguments.
     pub fn finish(self, ctx: &mut EvalContext) {
         let a = self.pos.iter().map(|v| v.as_ref());
         let b = self.named.iter().map(|(k, v)| (&v.v).with_span(k.span.join(v.span)));
diff --git a/src/eval/context.rs b/src/eval/context.rs
new file mode 100644
index 00000000..ece33146
--- /dev/null
+++ b/src/eval/context.rs
@@ -0,0 +1,298 @@
+use std::any::Any;
+use std::rc::Rc;
+
+use fontdock::FontStyle;
+
+use super::*;
+use crate::diag::Diag;
+use crate::diag::{Deco, Feedback, Pass};
+use crate::env::SharedEnv;
+use crate::geom::{ChildAlign, Dir, Gen, LayoutDirs, Length, Linear, Sides, Size};
+use crate::layout::{
+    Expansion, Node, NodePad, NodePages, NodePar, NodeSpacing, NodeStack, NodeText, Tree,
+};
+
+/// The context for evaluation.
+#[derive(Debug)]
+pub struct EvalContext {
+    /// The environment from which resources are gathered.
+    pub env: SharedEnv,
+    /// The active evaluation state.
+    pub state: State,
+    /// The accumulated feedback.
+    feedback: Feedback,
+    /// The finished page runs.
+    runs: Vec<NodePages>,
+    /// The stack of logical groups (paragraphs and such).
+    ///
+    /// Each entry contains metadata about the group and nodes that are at the
+    /// same level as the group, which will return to `inner` once the group is
+    /// finished.
+    groups: Vec<(Box<dyn Any>, Vec<Node>)>,
+    /// The nodes in the current innermost group
+    /// (whose metadata is in `groups.last()`).
+    inner: Vec<Node>,
+}
+
+impl EvalContext {
+    /// Create a new evaluation context with a base state.
+    pub fn new(env: SharedEnv, state: State) -> Self {
+        Self {
+            env,
+            state,
+            groups: vec![],
+            inner: vec![],
+            runs: vec![],
+            feedback: Feedback::new(),
+        }
+    }
+
+    /// Finish evaluation and return the created document.
+    pub fn finish(self) -> Pass<Tree> {
+        assert!(self.groups.is_empty(), "unfinished group");
+        Pass::new(Tree { runs: self.runs }, self.feedback)
+    }
+
+    /// Add a diagnostic to the feedback.
+    pub fn diag(&mut self, diag: Spanned<Diag>) {
+        self.feedback.diags.push(diag);
+    }
+
+    /// Add a decoration to the feedback.
+    pub fn deco(&mut self, deco: Spanned<Deco>) {
+        self.feedback.decos.push(deco);
+    }
+
+    /// Push a layout node to the active group.
+    ///
+    /// Spacing nodes will be handled according to their [`Softness`].
+    pub fn push(&mut self, node: impl Into<Node>) {
+        let node = node.into();
+
+        if let Node::Spacing(this) = node {
+            if this.softness == Softness::Soft && self.inner.is_empty() {
+                return;
+            }
+
+            if let Some(&Node::Spacing(other)) = self.inner.last() {
+                if this.softness > other.softness {
+                    self.inner.pop();
+                } else if this.softness == Softness::Soft {
+                    return;
+                }
+            }
+        }
+
+        self.inner.push(node);
+    }
+
+    /// Start a page group based on the active page state.
+    ///
+    /// The `softness` is a hint on whether empty pages should be kept in the
+    /// output.
+    ///
+    /// This also starts an inner paragraph.
+    pub fn start_page_group(&mut self, softness: Softness) {
+        self.start_group(PageGroup {
+            size: self.state.page.size,
+            padding: self.state.page.margins(),
+            dirs: self.state.dirs,
+            align: self.state.align,
+            softness,
+        });
+        self.start_par_group();
+    }
+
+    /// End a page group, returning its [`Softness`].
+    ///
+    /// Whether the page is kept when it's empty is decided by `keep_empty`
+    /// based on its softness. If kept, the page is pushed to the finished page
+    /// runs.
+    ///
+    /// This also ends an inner paragraph.
+    pub fn end_page_group<F>(&mut self, keep_empty: F) -> Softness
+    where
+        F: FnOnce(Softness) -> bool,
+    {
+        self.end_par_group();
+        let (group, children) = self.end_group::<PageGroup>();
+        if !children.is_empty() || keep_empty(group.softness) {
+            self.runs.push(NodePages {
+                size: group.size,
+                child: Node::any(NodePad {
+                    padding: group.padding,
+                    child: Node::any(NodeStack {
+                        dirs: group.dirs,
+                        align: group.align,
+                        expansion: Gen::uniform(Expansion::Fill),
+                        children,
+                    }),
+                }),
+            })
+        }
+        group.softness
+    }
+
+    /// Start a content group.
+    ///
+    /// This also starts an inner paragraph.
+    pub fn start_content_group(&mut self) {
+        self.start_group(ContentGroup);
+        self.start_par_group();
+    }
+
+    /// End a content group and return the resulting nodes.
+    ///
+    /// This also ends an inner paragraph.
+    pub fn end_content_group(&mut self) -> Vec<Node> {
+        self.end_par_group();
+        self.end_group::<ContentGroup>().1
+    }
+
+    /// Start a paragraph group based on the active text state.
+    pub fn start_par_group(&mut self) {
+        let em = self.state.font.font_size();
+        self.start_group(ParGroup {
+            dirs: self.state.dirs,
+            align: self.state.align,
+            line_spacing: self.state.par.line_spacing.resolve(em),
+        });
+    }
+
+    /// End a paragraph group and push it to its parent group if it's not empty.
+    pub fn end_par_group(&mut self) {
+        let (group, children) = self.end_group::<ParGroup>();
+        if !children.is_empty() {
+            self.push(NodePar {
+                dirs: group.dirs,
+                align: group.align,
+                // FIXME: This is a hack and should be superseded by something
+                //        better.
+                cross_expansion: if self.groups.len() <= 1 {
+                    Expansion::Fill
+                } else {
+                    Expansion::Fit
+                },
+                line_spacing: group.line_spacing,
+                children,
+            });
+        }
+    }
+
+    /// Start a layouting group.
+    ///
+    /// All further calls to [`push`](Self::push) will collect nodes for this group.
+    /// The given metadata will be returned alongside the collected nodes
+    /// in a matching call to [`end_group`](Self::end_group).
+    fn start_group<T: 'static>(&mut self, meta: T) {
+        self.groups.push((Box::new(meta), std::mem::take(&mut self.inner)));
+    }
+
+    /// End a layouting group started with [`start_group`](Self::start_group).
+    ///
+    /// This returns the stored metadata and the collected nodes.
+    #[track_caller]
+    fn end_group<T: 'static>(&mut self) -> (T, Vec<Node>) {
+        if let Some(&Node::Spacing(spacing)) = self.inner.last() {
+            if spacing.softness == Softness::Soft {
+                self.inner.pop();
+            }
+        }
+
+        let (any, outer) = self.groups.pop().expect("no pushed group");
+        let group = *any.downcast::<T>().expect("bad group type");
+        (group, std::mem::replace(&mut self.inner, outer))
+    }
+
+    /// Set the directions if they would apply to different axes, producing an
+    /// appropriate error otherwise.
+    pub fn set_dirs(&mut self, new: Gen<Option<Spanned<Dir>>>) {
+        let dirs = Gen::new(
+            new.main.map(|s| s.v).unwrap_or(self.state.dirs.main),
+            new.cross.map(|s| s.v).unwrap_or(self.state.dirs.cross),
+        );
+
+        if dirs.main.axis() != dirs.cross.axis() {
+            self.state.dirs = dirs;
+        } else {
+            for dir in new.main.iter().chain(new.cross.iter()) {
+                self.diag(error!(dir.span, "aligned axis"));
+            }
+        }
+    }
+
+    /// Apply a forced line break.
+    pub fn apply_linebreak(&mut self) {
+        self.end_par_group();
+        self.start_par_group();
+    }
+
+    /// Apply a forced paragraph break.
+    pub fn apply_parbreak(&mut self) {
+        self.end_par_group();
+        let em = self.state.font.font_size();
+        self.push(NodeSpacing {
+            amount: self.state.par.par_spacing.resolve(em),
+            softness: Softness::Soft,
+        });
+        self.start_par_group();
+    }
+
+    /// Construct a text node from the given string based on the active text
+    /// state.
+    pub fn make_text_node(&self, text: String) -> NodeText {
+        let mut variant = self.state.font.variant;
+
+        if self.state.font.strong {
+            variant.weight = variant.weight.thicken(300);
+        }
+
+        if self.state.font.emph {
+            variant.style = match variant.style {
+                FontStyle::Normal => FontStyle::Italic,
+                FontStyle::Italic => FontStyle::Normal,
+                FontStyle::Oblique => FontStyle::Normal,
+            }
+        }
+
+        NodeText {
+            text,
+            align: self.state.align,
+            dir: self.state.dirs.cross,
+            font_size: self.state.font.font_size(),
+            families: Rc::clone(&self.state.font.families),
+            variant,
+        }
+    }
+}
+
+/// Defines how an item interacts with surrounding items.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
+pub enum Softness {
+    /// A soft item can be skipped in some circumstances.
+    Soft,
+    /// A hard item is always retained.
+    Hard,
+}
+
+/// A group for a page run.
+#[derive(Debug)]
+struct PageGroup {
+    size: Size,
+    padding: Sides<Linear>,
+    dirs: LayoutDirs,
+    align: ChildAlign,
+    softness: Softness,
+}
+
+/// A group for generic content.
+#[derive(Debug)]
+struct ContentGroup;
+
+/// A group for a paragraph.
+#[derive(Debug)]
+struct ParGroup {
+    dirs: LayoutDirs,
+    align: ChildAlign,
+    line_spacing: Length,
+}
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 62bd444c..20d32e84 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -1,36 +1,32 @@
-//! Evaluation of syntax trees.
+//! Evaluation of syntax trees into layout trees.
 
 #[macro_use]
 mod value;
-mod args;
+mod call;
+mod context;
 mod scope;
 mod state;
 
-pub use args::*;
+pub use call::*;
+pub use context::*;
 pub use scope::*;
 pub use state::*;
 pub use value::*;
 
-use std::any::Any;
 use std::rc::Rc;
 
-use fontdock::FontStyle;
-
 use crate::color::Color;
-use crate::diag::Diag;
-use crate::diag::{Deco, Feedback, Pass};
+use crate::diag::Pass;
 use crate::env::SharedEnv;
-use crate::geom::{BoxAlign, Dir, Flow, Gen, Length, Linear, Relative, Sides, Size};
-use crate::layout::{
-    Document, Expansion, LayoutNode, Pad, Pages, Par, Spacing, Stack, Text,
-};
+use crate::geom::{Gen, Length, Relative};
+use crate::layout::{self, Expansion, NodeSpacing, NodeStack};
 use crate::syntax::*;
 
-/// Evaluate a syntax tree into a document.
+/// Evaluate a syntax tree into a layout tree.
 ///
 /// The given `state` is the base state that may be updated over the course of
 /// evaluation.
-pub fn eval(tree: &SynTree, env: SharedEnv, state: State) -> Pass<Document> {
+pub fn eval(tree: &Tree, env: SharedEnv, state: State) -> Pass<layout::Tree> {
     let mut ctx = EvalContext::new(env, state);
     ctx.start_page_group(Softness::Hard);
     tree.eval(&mut ctx);
@@ -38,285 +34,6 @@ pub fn eval(tree: &SynTree, env: SharedEnv, state: State) -> Pass<Document> {
     ctx.finish()
 }
 
-/// The context for evaluation.
-#[derive(Debug)]
-pub struct EvalContext {
-    /// The environment from which resources are gathered.
-    pub env: SharedEnv,
-    /// The active evaluation state.
-    pub state: State,
-    /// The accumulated feedback.
-    feedback: Feedback,
-    /// The finished page runs.
-    runs: Vec<Pages>,
-    /// The stack of logical groups (paragraphs and such).
-    ///
-    /// Each entry contains metadata about the group and nodes that are at the
-    /// same level as the group, which will return to `inner` once the group is
-    /// finished.
-    groups: Vec<(Box<dyn Any>, Vec<LayoutNode>)>,
-    /// The nodes in the current innermost group
-    /// (whose metadata is in `groups.last()`).
-    inner: Vec<LayoutNode>,
-}
-
-impl EvalContext {
-    /// Create a new evaluation context with a base state.
-    pub fn new(env: SharedEnv, state: State) -> Self {
-        Self {
-            env,
-            state,
-            groups: vec![],
-            inner: vec![],
-            runs: vec![],
-            feedback: Feedback::new(),
-        }
-    }
-
-    /// Finish evaluation and return the created document.
-    pub fn finish(self) -> Pass<Document> {
-        assert!(self.groups.is_empty(), "unfinished group");
-        Pass::new(Document { runs: self.runs }, self.feedback)
-    }
-
-    /// Add a diagnostic to the feedback.
-    pub fn diag(&mut self, diag: Spanned<Diag>) {
-        self.feedback.diags.push(diag);
-    }
-
-    /// Add a decoration to the feedback.
-    pub fn deco(&mut self, deco: Spanned<Deco>) {
-        self.feedback.decos.push(deco);
-    }
-
-    /// Push a layout node to the active group.
-    ///
-    /// Spacing nodes will be handled according to their [`Softness`].
-    pub fn push(&mut self, node: impl Into<LayoutNode>) {
-        let node = node.into();
-
-        if let LayoutNode::Spacing(this) = node {
-            if this.softness == Softness::Soft && self.inner.is_empty() {
-                return;
-            }
-
-            if let Some(&LayoutNode::Spacing(other)) = self.inner.last() {
-                if this.softness > other.softness {
-                    self.inner.pop();
-                } else if this.softness == Softness::Soft {
-                    return;
-                }
-            }
-        }
-
-        self.inner.push(node);
-    }
-
-    /// Start a page group based on the active page state.
-    ///
-    /// The `softness` is a hint on whether empty pages should be kept in the
-    /// output.
-    ///
-    /// This also starts an inner paragraph.
-    pub fn start_page_group(&mut self, softness: Softness) {
-        self.start_group(PageGroup {
-            size: self.state.page.size,
-            padding: self.state.page.margins(),
-            flow: self.state.flow,
-            align: self.state.align,
-            softness,
-        });
-        self.start_par_group();
-    }
-
-    /// End a page group, returning its [`Softness`].
-    ///
-    /// Whether the page is kept when it's empty is decided by `keep_empty`
-    /// based on its softness. If kept, the page is pushed to the finished page
-    /// runs.
-    ///
-    /// This also ends an inner paragraph.
-    pub fn end_page_group(
-        &mut self,
-        keep_empty: impl FnOnce(Softness) -> bool,
-    ) -> Softness {
-        self.end_par_group();
-        let (group, children) = self.end_group::<PageGroup>();
-        if !children.is_empty() || keep_empty(group.softness) {
-            self.runs.push(Pages {
-                size: group.size,
-                child: LayoutNode::dynamic(Pad {
-                    padding: group.padding,
-                    child: LayoutNode::dynamic(Stack {
-                        flow: group.flow,
-                        align: group.align,
-                        expansion: Gen::uniform(Expansion::Fill),
-                        children,
-                    }),
-                }),
-            })
-        }
-        group.softness
-    }
-
-    /// Start a content group.
-    ///
-    /// This also starts an inner paragraph.
-    pub fn start_content_group(&mut self) {
-        self.start_group(ContentGroup);
-        self.start_par_group();
-    }
-
-    /// End a content group and return the resulting nodes.
-    ///
-    /// This also ends an inner paragraph.
-    pub fn end_content_group(&mut self) -> Vec<LayoutNode> {
-        self.end_par_group();
-        self.end_group::<ContentGroup>().1
-    }
-
-    /// Start a paragraph group based on the active text state.
-    pub fn start_par_group(&mut self) {
-        let em = self.state.font.font_size();
-        self.start_group(ParGroup {
-            flow: self.state.flow,
-            align: self.state.align,
-            line_spacing: self.state.par.line_spacing.resolve(em),
-        });
-    }
-
-    /// End a paragraph group and push it to its parent group if it's not empty.
-    pub fn end_par_group(&mut self) {
-        let (group, children) = self.end_group::<ParGroup>();
-        if !children.is_empty() {
-            // FIXME: This is a hack and should be superseded by something
-            //        better.
-            let cross_expansion = Expansion::fill_if(self.groups.len() <= 1);
-            self.push(Par {
-                flow: group.flow,
-                align: group.align,
-                cross_expansion,
-                line_spacing: group.line_spacing,
-                children,
-            });
-        }
-    }
-
-    /// Start a layouting group.
-    ///
-    /// All further calls to [`push`](Self::push) will collect nodes for this group.
-    /// The given metadata will be returned alongside the collected nodes
-    /// in a matching call to [`end_group`](Self::end_group).
-    fn start_group<T: 'static>(&mut self, meta: T) {
-        self.groups.push((Box::new(meta), std::mem::take(&mut self.inner)));
-    }
-
-    /// End a layouting group started with [`start_group`](Self::start_group).
-    ///
-    /// This returns the stored metadata and the collected nodes.
-    #[track_caller]
-    fn end_group<T: 'static>(&mut self) -> (T, Vec<LayoutNode>) {
-        if let Some(&LayoutNode::Spacing(spacing)) = self.inner.last() {
-            if spacing.softness == Softness::Soft {
-                self.inner.pop();
-            }
-        }
-
-        let (any, outer) = self.groups.pop().expect("no pushed group");
-        let group = *any.downcast::<T>().expect("bad group type");
-        (group, std::mem::replace(&mut self.inner, outer))
-    }
-
-    /// Updates the flow directions if the resulting main and cross directions
-    /// apply to different axes. Generates an appropriate error, otherwise.
-    pub fn set_flow(&mut self, new: Gen<Option<Spanned<Dir>>>) {
-        let flow = Gen::new(
-            new.main.map(|s| s.v).unwrap_or(self.state.flow.main),
-            new.cross.map(|s| s.v).unwrap_or(self.state.flow.cross),
-        );
-
-        if flow.main.axis() != flow.cross.axis() {
-            self.state.flow = flow;
-        } else {
-            for dir in new.main.iter().chain(new.cross.iter()) {
-                self.diag(error!(dir.span, "aligned axis"));
-            }
-        }
-    }
-
-    /// Apply a forced line break.
-    pub fn apply_linebreak(&mut self) {
-        self.end_par_group();
-        self.start_par_group();
-    }
-
-    /// Apply a forced paragraph break.
-    pub fn apply_parbreak(&mut self) {
-        self.end_par_group();
-        let em = self.state.font.font_size();
-        self.push(Spacing {
-            amount: self.state.par.par_spacing.resolve(em),
-            softness: Softness::Soft,
-        });
-        self.start_par_group();
-    }
-
-    /// Construct a text node from the given string based on the active text
-    /// state.
-    pub fn make_text_node(&self, text: String) -> Text {
-        let mut variant = self.state.font.variant;
-
-        if self.state.font.strong {
-            variant.weight = variant.weight.thicken(300);
-        }
-
-        if self.state.font.emph {
-            variant.style = match variant.style {
-                FontStyle::Normal => FontStyle::Italic,
-                FontStyle::Italic => FontStyle::Normal,
-                FontStyle::Oblique => FontStyle::Normal,
-            }
-        }
-
-        Text {
-            text,
-            align: self.state.align,
-            dir: self.state.flow.cross,
-            font_size: self.state.font.font_size(),
-            families: Rc::clone(&self.state.font.families),
-            variant,
-        }
-    }
-}
-
-/// A group for page runs.
-struct PageGroup {
-    size: Size,
-    padding: Sides<Linear>,
-    flow: Flow,
-    align: BoxAlign,
-    softness: Softness,
-}
-
-/// A group for generic content.
-struct ContentGroup;
-
-/// A group for paragraphs.
-struct ParGroup {
-    flow: Flow,
-    align: BoxAlign,
-    line_spacing: Length,
-}
-
-/// Defines how an item interact with surrounding items.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
-pub enum Softness {
-    /// A soft item can be skipped in some circumstances.
-    Soft,
-    /// A hard item is always retained.
-    Hard,
-}
-
 /// Evaluate an item.
 ///
 /// _Note_: Evaluation is not necessarily pure, it may change the active state.
@@ -339,7 +56,7 @@ where
     }
 }
 
-impl Eval for &[Spanned<SynNode>] {
+impl Eval for &[Spanned<Node>] {
     type Output = ();
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
@@ -349,33 +66,33 @@ impl Eval for &[Spanned<SynNode>] {
     }
 }
 
-impl Eval for Spanned<&SynNode> {
+impl Eval for Spanned<&Node> {
     type Output = ();
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
         match self.v {
-            SynNode::Text(text) => {
+            Node::Text(text) => {
                 let node = ctx.make_text_node(text.clone());
                 ctx.push(node);
             }
 
-            SynNode::Space => {
+            Node::Space => {
                 let em = ctx.state.font.font_size();
-                ctx.push(Spacing {
+                ctx.push(NodeSpacing {
                     amount: ctx.state.par.word_spacing.resolve(em),
                     softness: Softness::Soft,
                 });
             }
-            SynNode::Linebreak => ctx.apply_linebreak(),
-            SynNode::Parbreak => ctx.apply_parbreak(),
+            Node::Linebreak => ctx.apply_linebreak(),
+            Node::Parbreak => ctx.apply_parbreak(),
 
-            SynNode::Strong => ctx.state.font.strong ^= true,
-            SynNode::Emph => ctx.state.font.emph ^= true,
+            Node::Strong => ctx.state.font.strong ^= true,
+            Node::Emph => ctx.state.font.emph ^= true,
 
-            SynNode::Heading(heading) => heading.with_span(self.span).eval(ctx),
-            SynNode::Raw(raw) => raw.with_span(self.span).eval(ctx),
+            Node::Heading(heading) => heading.with_span(self.span).eval(ctx),
+            Node::Raw(raw) => raw.with_span(self.span).eval(ctx),
 
-            SynNode::Expr(expr) => {
+            Node::Expr(expr) => {
                 let value = expr.with_span(self.span).eval(ctx);
                 value.eval(ctx)
             }
@@ -413,15 +130,15 @@ impl Eval for Spanned<&NodeRaw> {
 
         let mut children = vec![];
         for line in &self.v.lines {
-            children.push(LayoutNode::Text(ctx.make_text_node(line.clone())));
-            children.push(LayoutNode::Spacing(Spacing {
+            children.push(layout::Node::Text(ctx.make_text_node(line.clone())));
+            children.push(layout::Node::Spacing(NodeSpacing {
                 amount: line_spacing,
                 softness: Softness::Hard,
             }));
         }
 
-        ctx.push(Stack {
-            flow: ctx.state.flow,
+        ctx.push(NodeStack {
+            dirs: ctx.state.dirs,
             align: ctx.state.align,
             expansion: Gen::uniform(Expansion::Fit),
             children,
@@ -436,10 +153,13 @@ impl Eval for Spanned<&Expr> {
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
         match self.v {
-            Expr::Lit(lit) => lit.with_span(self.span).eval(ctx),
-            Expr::Call(call) => call.with_span(self.span).eval(ctx),
-            Expr::Unary(unary) => unary.with_span(self.span).eval(ctx),
-            Expr::Binary(binary) => binary.with_span(self.span).eval(ctx),
+            Expr::Lit(v) => v.with_span(self.span).eval(ctx),
+            Expr::Call(v) => v.with_span(self.span).eval(ctx),
+            Expr::Unary(v) => v.with_span(self.span).eval(ctx),
+            Expr::Binary(v) => v.with_span(self.span).eval(ctx),
+            Expr::Array(v) => Value::Array(v.with_span(self.span).eval(ctx)),
+            Expr::Dict(v) => Value::Dict(v.with_span(self.span).eval(ctx)),
+            Expr::Content(v) => Value::Content(v.clone()),
         }
     }
 }
@@ -463,14 +183,11 @@ impl Eval for Spanned<&Lit> {
             Lit::Percent(v) => Value::Relative(Relative::new(v / 100.0)),
             Lit::Color(v) => Value::Color(Color::Rgba(v)),
             Lit::Str(ref v) => Value::Str(v.clone()),
-            Lit::Array(ref v) => Value::Array(v.with_span(self.span).eval(ctx)),
-            Lit::Dict(ref v) => Value::Dict(v.with_span(self.span).eval(ctx)),
-            Lit::Content(ref v) => Value::Content(v.clone()),
         }
     }
 }
 
-impl Eval for Spanned<&Array> {
+impl Eval for Spanned<&ExprArray> {
     type Output = ValueArray;
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
@@ -478,7 +195,7 @@ impl Eval for Spanned<&Array> {
     }
 }
 
-impl Eval for Spanned<&Dict> {
+impl Eval for Spanned<&ExprDict> {
     type Output = ValueDict;
 
     fn eval(self, ctx: &mut EvalContext) -> Self::Output {
@@ -489,36 +206,6 @@ impl Eval for Spanned<&Dict> {
     }
 }
 
-impl Eval for Spanned<&ExprCall> {
-    type Output = Value;
-
-    fn eval(self, ctx: &mut EvalContext) -> Self::Output {
-        let name = &self.v.name.v;
-        let span = self.v.name.span;
-
-        if let Some(value) = ctx.state.scope.get(name) {
-            if let Value::Func(func) = value {
-                let func = func.clone();
-                ctx.feedback.decos.push(Deco::Resolved.with_span(span));
-
-                let mut args = self.v.args.as_ref().eval(ctx);
-                let returned = func(ctx, &mut args);
-                args.finish(ctx);
-
-                return returned;
-            } else {
-                let ty = value.type_name();
-                ctx.diag(error!(span, "a value of type {} is not callable", ty));
-            }
-        } else if !name.is_empty() {
-            ctx.diag(error!(span, "unknown function"));
-        }
-
-        ctx.feedback.decos.push(Deco::Unresolved.with_span(span));
-        Value::Error
-    }
-}
-
 impl Eval for Spanned<&ExprUnary> {
     type Output = Value;
 
diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index c9ce1423..dd7cc1da 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -1,11 +1,9 @@
-//! Mapping from identifiers to functions.
-
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
 
 use super::Value;
 
-/// A map from identifiers to functions.
+/// A map from identifiers to values.
 #[derive(Default, Clone, PartialEq)]
 pub struct Scope {
     values: HashMap<String, Value>,
diff --git a/src/eval/state.rs b/src/eval/state.rs
index 3f3ac8e4..9cdafaf2 100644
--- a/src/eval/state.rs
+++ b/src/eval/state.rs
@@ -1,46 +1,46 @@
-//! Evaluation state.
-
 use std::rc::Rc;
 
 use fontdock::{fallback, FallbackTree, FontStretch, FontStyle, FontVariant, FontWeight};
 
 use super::Scope;
-use crate::geom::{Align, BoxAlign, Dir, Flow, Length, Linear, Relative, Sides, Size};
+use crate::geom::{
+    Align, ChildAlign, Dir, LayoutDirs, Length, Linear, Relative, Sides, Size,
+};
 use crate::paper::{Paper, PaperClass, PAPER_A4};
 
-/// The active evaluation state.
+/// The evaluation state.
 #[derive(Debug, Clone, PartialEq)]
 pub struct State {
-    /// The scope that contains function definitions.
+    /// The scope that contains variable definitions.
     pub scope: Scope,
-    /// The page state.
-    pub page: PageState,
-    /// The paragraph state.
-    pub par: ParState,
-    /// The font state.
-    pub font: FontState,
-    /// The active layouting directions.
-    pub flow: Flow,
-    /// The active box alignments.
-    pub align: BoxAlign,
+    /// The current page state.
+    pub page: StatePage,
+    /// The current paragraph state.
+    pub par: StatePar,
+    /// The current font state.
+    pub font: StateFont,
+    /// The current directions.
+    pub dirs: LayoutDirs,
+    /// The current alignments.
+    pub align: ChildAlign,
 }
 
 impl Default for State {
     fn default() -> Self {
         Self {
             scope: crate::library::_std(),
-            page: PageState::default(),
-            par: ParState::default(),
-            font: FontState::default(),
-            flow: Flow::new(Dir::TTB, Dir::LTR),
-            align: BoxAlign::new(Align::Start, Align::Start),
+            page: StatePage::default(),
+            par: StatePar::default(),
+            font: StateFont::default(),
+            dirs: LayoutDirs::new(Dir::TTB, Dir::LTR),
+            align: ChildAlign::new(Align::Start, Align::Start),
         }
     }
 }
 
 /// Defines page properties.
 #[derive(Debug, Copy, Clone, PartialEq)]
-pub struct PageState {
+pub struct StatePage {
     /// The class of this page.
     pub class: PaperClass,
     /// The width and height of the page.
@@ -50,7 +50,7 @@ pub struct PageState {
     pub margins: Sides<Option<Linear>>,
 }
 
-impl PageState {
+impl StatePage {
     /// The default page style for the given paper.
     pub fn new(paper: Paper) -> Self {
         Self {
@@ -72,7 +72,7 @@ impl PageState {
     }
 }
 
-impl Default for PageState {
+impl Default for StatePage {
     fn default() -> Self {
         Self::new(PAPER_A4)
     }
@@ -80,7 +80,7 @@ impl Default for PageState {
 
 /// Defines paragraph properties.
 #[derive(Debug, Copy, Clone, PartialEq)]
-pub struct ParState {
+pub struct StatePar {
     /// The spacing between words (dependent on scaled font size).
     pub word_spacing: Linear,
     /// The spacing between lines (dependent on scaled font size).
@@ -89,7 +89,7 @@ pub struct ParState {
     pub par_spacing: Linear,
 }
 
-impl Default for ParState {
+impl Default for StatePar {
     fn default() -> Self {
         Self {
             word_spacing: Relative::new(0.25).into(),
@@ -101,7 +101,7 @@ impl Default for ParState {
 
 /// Defines font properties.
 #[derive(Debug, Clone, PartialEq)]
-pub struct FontState {
+pub struct StateFont {
     /// A tree of font family names and generic class names.
     pub families: Rc<FallbackTree>,
     /// The selected font variant.
@@ -118,14 +118,14 @@ pub struct FontState {
     pub emph: bool,
 }
 
-impl FontState {
+impl StateFont {
     /// The absolute font size.
     pub fn font_size(&self) -> Length {
         self.scale.resolve(self.size)
     }
 }
 
-impl Default for FontState {
+impl Default for StateFont {
     fn default() -> Self {
         Self {
             families: Rc::new(default_font_families()),
@@ -150,8 +150,6 @@ fn default_font_families() -> FallbackTree {
             "serif"      => ["source serif pro", "noto serif"],
             "sans-serif" => ["source sans pro", "noto sans"],
             "monospace"  => ["source code pro", "noto sans mono"],
-            "emoji"      => ["segoe ui emoji", "noto emoji"],
-            "math"       => ["latin modern math", "serif"],
         },
         base: [
             "source sans pro",
diff --git a/src/eval/value.rs b/src/eval/value.rs
index d1dcdcfa..a91ff137 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -1,5 +1,3 @@
-//! Computational values.
-
 use std::any::Any;
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
@@ -9,7 +7,7 @@ use std::rc::Rc;
 use super::{Args, Eval, EvalContext};
 use crate::color::Color;
 use crate::geom::{Length, Linear, Relative};
-use crate::syntax::{Spanned, SynTree, WithSpan};
+use crate::syntax::{Spanned, Tree, WithSpan};
 
 /// A computational value.
 #[derive(Clone, PartialEq)]
@@ -47,6 +45,14 @@ pub enum Value {
 }
 
 impl Value {
+    /// Create a new dynamic value.
+    pub fn any<T>(any: T) -> Self
+    where
+        T: Type + Debug + Clone + PartialEq + 'static,
+    {
+        Self::Any(ValueAny::new(any))
+    }
+
     /// Try to cast the value into a specific type.
     pub fn cast<T>(self) -> CastResult<T, Self>
     where
@@ -130,7 +136,7 @@ pub type ValueArray = Vec<Value>;
 pub type ValueDict = HashMap<String, Value>;
 
 /// A content value: `{*Hi* there}`.
-pub type ValueContent = SynTree;
+pub type ValueContent = Tree;
 
 /// A wrapper around a reference-counted executable function.
 #[derive(Clone)]
@@ -197,7 +203,7 @@ impl ValueAny {
         self.0.as_any().downcast_ref()
     }
 
-    /// The name of the stored object's type.
+    /// The name of the stored value's type.
     pub fn type_name(&self) -> &'static str {
         self.0.dyn_type_name()
     }
@@ -289,7 +295,7 @@ pub enum CastResult<T, V> {
 }
 
 impl<T, V> CastResult<T, V> {
-    /// Access the conversion resulting, discarding a possibly existing warning.
+    /// Access the conversion result, discarding a possibly existing warning.
     pub fn ok(self) -> Option<T> {
         match self {
             CastResult::Ok(t) | CastResult::Warn(t, _) => Some(t),
@@ -399,7 +405,7 @@ impl From<ValueAny> for Value {
     }
 }
 
-/// Make a type usable with [`ValueAny`].
+/// Make a type usable as a [`Value`].
 ///
 /// Given a type `T`, this implements the following traits:
 /// - [`Type`] for `T`,
@@ -419,7 +425,7 @@ macro_rules! impl_type {
 
         impl From<$type> for $crate::eval::Value {
             fn from(any: $type) -> Self {
-                $crate::eval::Value::Any($crate::eval::ValueAny::new(any))
+                $crate::eval::Value::any(any)
             }
         }
 
diff --git a/src/export/pdf.rs b/src/export/pdf.rs
index 5a2aa0cc..03c9ae95 100644
--- a/src/export/pdf.rs
+++ b/src/export/pdf.rs
@@ -15,22 +15,22 @@ use ttf_parser::{name_id, GlyphId};
 
 use crate::env::{Env, ImageResource, ResourceId};
 use crate::geom::Length;
-use crate::layout::{BoxLayout, LayoutElement};
+use crate::layout::{Element, Frame};
 
-/// Export a list of layouts into a _PDF_ document.
+/// Export a collection of frames into a _PDF_ document.
 ///
-/// This creates one page per layout. Additionally to the layouts, you need to
-/// pass in the font loader used for typesetting such that the fonts can be
-/// included in the _PDF_.
+/// This creates one page per frame. In addition to the frames, you need to pass
+/// in the environment used for typesetting such that things like fonts and
+/// images can be included in the _PDF_.
 ///
 /// Returns the raw bytes making up the _PDF_ document.
-pub fn export(layouts: &[BoxLayout], env: &Env) -> Vec<u8> {
-    PdfExporter::new(layouts, env).write()
+pub fn export(frames: &[Frame], env: &Env) -> Vec<u8> {
+    PdfExporter::new(frames, env).write()
 }
 
 struct PdfExporter<'a> {
     writer: PdfWriter,
-    layouts: &'a [BoxLayout],
+    frames: &'a [Frame],
     env: &'a Env,
     refs: Refs,
     fonts: Remapper<FaceId>,
@@ -38,7 +38,7 @@ struct PdfExporter<'a> {
 }
 
 impl<'a> PdfExporter<'a> {
-    fn new(layouts: &'a [BoxLayout], env: &'a Env) -> Self {
+    fn new(frames: &'a [Frame], env: &'a Env) -> Self {
         let mut writer = PdfWriter::new(1, 7);
         writer.set_indent(2);
 
@@ -46,11 +46,11 @@ impl<'a> PdfExporter<'a> {
         let mut images = Remapper::new();
         let mut alpha_masks = 0;
 
-        for layout in layouts {
-            for (_, element) in &layout.elements {
+        for frame in frames {
+            for (_, element) in &frame.elements {
                 match element {
-                    LayoutElement::Text(shaped) => fonts.insert(shaped.face),
-                    LayoutElement::Image(image) => {
+                    Element::Text(shaped) => fonts.insert(shaped.face),
+                    Element::Image(image) => {
                         let img = env.resources.loaded::<ImageResource>(image.res);
                         if img.buf.color().has_alpha() {
                             alpha_masks += 1;
@@ -61,16 +61,9 @@ impl<'a> PdfExporter<'a> {
             }
         }
 
-        let refs = Refs::new(layouts.len(), fonts.len(), images.len(), alpha_masks);
+        let refs = Refs::new(frames.len(), fonts.len(), images.len(), alpha_masks);
 
-        Self {
-            writer,
-            layouts,
-            env,
-            refs,
-            fonts,
-            images,
-        }
+        Self { writer, frames, env, refs, fonts, images }
     }
 
     fn write(mut self) -> Vec<u8> {
@@ -110,7 +103,7 @@ impl<'a> PdfExporter<'a> {
 
         // The page objects (non-root nodes in the page tree).
         for ((page_id, content_id), page) in
-            self.refs.pages().zip(self.refs.contents()).zip(self.layouts)
+            self.refs.pages().zip(self.refs.contents()).zip(self.frames)
         {
             self.writer
                 .page(page_id)
@@ -126,12 +119,12 @@ impl<'a> PdfExporter<'a> {
     }
 
     fn write_pages(&mut self) {
-        for (id, page) in self.refs.contents().zip(self.layouts) {
+        for (id, page) in self.refs.contents().zip(self.frames) {
             self.write_page(id, &page);
         }
     }
 
-    fn write_page(&mut self, id: Ref, page: &'a BoxLayout) {
+    fn write_page(&mut self, id: Ref, page: &'a Frame) {
         let mut content = Content::new();
 
         // We only write font switching actions when the used face changes. To
@@ -141,7 +134,7 @@ impl<'a> PdfExporter<'a> {
 
         let mut text = content.text();
         for (pos, element) in &page.elements {
-            if let LayoutElement::Text(shaped) = element {
+            if let Element::Text(shaped) = element {
                 // Check if we need to issue a font switching action.
                 if shaped.face != face || shaped.font_size != size {
                     face = shaped.face;
@@ -161,7 +154,7 @@ impl<'a> PdfExporter<'a> {
         drop(text);
 
         for (pos, element) in &page.elements {
-            if let LayoutElement::Image(image) = element {
+            if let Element::Image(image) = element {
                 let name = format!("Im{}", self.images.map(image.res));
                 let size = image.size;
                 let x = pos.x.to_pt() as f32;
@@ -359,12 +352,12 @@ struct FontRefs {
 impl Refs {
     const OBJECTS_PER_FONT: usize = 5;
 
-    fn new(layouts: usize, fonts: usize, images: usize, alpha_masks: usize) -> Self {
+    fn new(frames: usize, fonts: usize, images: usize, alpha_masks: usize) -> Self {
         let catalog = 1;
         let page_tree = catalog + 1;
         let pages_start = page_tree + 1;
-        let contents_start = pages_start + layouts as i32;
-        let fonts_start = contents_start + layouts as i32;
+        let contents_start = pages_start + frames as i32;
+        let fonts_start = contents_start + frames as i32;
         let images_start = fonts_start + (Self::OBJECTS_PER_FONT * fonts) as i32;
         let alpha_masks_start = images_start + images as i32;
         let end = alpha_masks_start + alpha_masks as i32;
diff --git a/src/font.rs b/src/font.rs
index 68a2db67..40ec5918 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -3,19 +3,16 @@
 use fontdock::{ContainsChar, FaceFromVec, FontSource};
 use ttf_parser::Face;
 
-/// A font loader backed by a dynamic source.
-pub type FontLoader = fontdock::FontLoader<Box<DynSource>>;
-
-/// The dynamic font source.
-pub type DynSource = dyn FontSource<Face = OwnedFace>;
+/// A font loader that is backed by a dynamic source.
+pub type FontLoader = fontdock::FontLoader<Box<dyn FontSource<Face = FaceBuf>>>;
 
 /// An owned font face.
-pub struct OwnedFace {
+pub struct FaceBuf {
     data: Box<[u8]>,
     face: Face<'static>,
 }
 
-impl OwnedFace {
+impl FaceBuf {
     /// Get a reference to the underlying face.
     pub fn get(&self) -> &Face<'_> {
         // We can't implement Deref because that would leak the internal 'static
@@ -29,7 +26,7 @@ impl OwnedFace {
     }
 }
 
-impl FaceFromVec for OwnedFace {
+impl FaceFromVec for FaceBuf {
     fn from_vec(vec: Vec<u8>, i: u32) -> Option<Self> {
         let data = vec.into_boxed_slice();
 
@@ -45,7 +42,7 @@ impl FaceFromVec for OwnedFace {
     }
 }
 
-impl ContainsChar for OwnedFace {
+impl ContainsChar for FaceBuf {
     fn contains_char(&self, c: char) -> bool {
         self.get().glyph_index(c).is_some()
     }
diff --git a/src/geom/align.rs b/src/geom/align.rs
index 7c4d965f..8f02a4ea 100644
--- a/src/geom/align.rs
+++ b/src/geom/align.rs
@@ -1,7 +1,7 @@
 use super::*;
 
-/// The alignment of a box in a container.
-pub type BoxAlign = Gen<Align>;
+/// The alignment of a child in a container.
+pub type ChildAlign = Gen<Align>;
 
 /// Where to align something along a directed axis.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
diff --git a/src/geom/dir.rs b/src/geom/dir.rs
index f7ffa3e2..c5eaa3a6 100644
--- a/src/geom/dir.rs
+++ b/src/geom/dir.rs
@@ -1,7 +1,7 @@
 use super::*;
 
-/// The directions along which content flows in a container.
-pub type Flow = Gen<Dir>;
+/// The directions along which nodes are layouted.
+pub type LayoutDirs = Gen<Dir>;
 
 /// The four directions into which content can be laid out.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
diff --git a/src/geom/gen.rs b/src/geom/gen.rs
index 11b117ea..8723ea99 100644
--- a/src/geom/gen.rs
+++ b/src/geom/gen.rs
@@ -50,8 +50,8 @@ impl<T> Get<GenAxis> for Gen<T> {
 impl<T> Switch for Gen<T> {
     type Other = Spec<T>;
 
-    fn switch(self, flow: Flow) -> Self::Other {
-        match flow.main.axis() {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
+        match dirs.main.axis() {
             SpecAxis::Horizontal => Spec::new(self.main, self.cross),
             SpecAxis::Vertical => Spec::new(self.cross, self.main),
         }
@@ -80,10 +80,10 @@ impl GenAxis {
 impl Switch for GenAxis {
     type Other = SpecAxis;
 
-    fn switch(self, flow: Flow) -> Self::Other {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
         match self {
-            Self::Main => flow.main.axis(),
-            Self::Cross => flow.cross.axis(),
+            Self::Main => dirs.main.axis(),
+            Self::Cross => dirs.cross.axis(),
         }
     }
 }
diff --git a/src/geom/mod.rs b/src/geom/mod.rs
index 0589346e..69bb0898 100644
--- a/src/geom/mod.rs
+++ b/src/geom/mod.rs
@@ -50,5 +50,5 @@ pub trait Switch {
 
     /// The other version of this type based on the current layouting
     /// directions.
-    fn switch(self, flow: Flow) -> Self::Other;
+    fn switch(self, dirs: LayoutDirs) -> Self::Other;
 }
diff --git a/src/geom/point.rs b/src/geom/point.rs
index 4523a861..0faa781c 100644
--- a/src/geom/point.rs
+++ b/src/geom/point.rs
@@ -45,8 +45,8 @@ impl Get<SpecAxis> for Point {
 impl Switch for Point {
     type Other = Gen<Length>;
 
-    fn switch(self, flow: Flow) -> Self::Other {
-        match flow.main.axis() {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
+        match dirs.main.axis() {
             SpecAxis::Horizontal => Gen::new(self.x, self.y),
             SpecAxis::Vertical => Gen::new(self.y, self.x),
         }
diff --git a/src/geom/size.rs b/src/geom/size.rs
index 28984659..bc233e5c 100644
--- a/src/geom/size.rs
+++ b/src/geom/size.rs
@@ -53,8 +53,8 @@ impl Get<SpecAxis> for Size {
 impl Switch for Size {
     type Other = Gen<Length>;
 
-    fn switch(self, flow: Flow) -> Self::Other {
-        match flow.main.axis() {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
+        match dirs.main.axis() {
             SpecAxis::Horizontal => Gen::new(self.width, self.height),
             SpecAxis::Vertical => Gen::new(self.height, self.width),
         }
diff --git a/src/geom/spec.rs b/src/geom/spec.rs
index f259ce25..c61f9526 100644
--- a/src/geom/spec.rs
+++ b/src/geom/spec.rs
@@ -66,8 +66,8 @@ impl<T> Get<SpecAxis> for Spec<T> {
 impl<T> Switch for Spec<T> {
     type Other = Gen<T>;
 
-    fn switch(self, flow: Flow) -> Self::Other {
-        match flow.main.axis() {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
+        match dirs.main.axis() {
             SpecAxis::Horizontal => Gen::new(self.horizontal, self.vertical),
             SpecAxis::Vertical => Gen::new(self.vertical, self.horizontal),
         }
@@ -96,11 +96,11 @@ impl SpecAxis {
 impl Switch for SpecAxis {
     type Other = GenAxis;
 
-    fn switch(self, flow: Flow) -> Self::Other {
-        if self == flow.main.axis() {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
+        if self == dirs.main.axis() {
             GenAxis::Main
         } else {
-            debug_assert_eq!(self, flow.cross.axis());
+            debug_assert_eq!(self, dirs.cross.axis());
             GenAxis::Cross
         }
     }
diff --git a/src/layout/fixed.rs b/src/layout/fixed.rs
index d0daa2ca..2ec46df3 100644
--- a/src/layout/fixed.rs
+++ b/src/layout/fixed.rs
@@ -3,16 +3,16 @@ use crate::geom::Linear;
 
 /// A node that can fix its child's width and height.
 #[derive(Debug, Clone, PartialEq)]
-pub struct Fixed {
+pub struct NodeFixed {
     /// The fixed width, if any.
     pub width: Option<Linear>,
     /// The fixed height, if any.
     pub height: Option<Linear>,
     /// The child node whose size to fix.
-    pub child: LayoutNode,
+    pub child: Node,
 }
 
-impl Layout for Fixed {
+impl Layout for NodeFixed {
     fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted {
         let Area { rem, full } = areas.current;
         let size = Size::new(
@@ -25,8 +25,8 @@ impl Layout for Fixed {
     }
 }
 
-impl From<Fixed> for LayoutNode {
-    fn from(fixed: Fixed) -> Self {
-        Self::dynamic(fixed)
+impl From<NodeFixed> for Node {
+    fn from(fixed: NodeFixed) -> Self {
+        Self::any(fixed)
     }
 }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 44a2c2fa..d09566e3 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -1,4 +1,4 @@
-//! Layouting of documents.
+//! Layouting.
 
 mod fixed;
 mod node;
@@ -20,10 +20,48 @@ pub use spacing::*;
 pub use stack::*;
 pub use text::*;
 
-/// Layout a document and return the produced layouts.
-pub fn layout(document: &Document, env: SharedEnv) -> Vec<BoxLayout> {
-    let mut ctx = LayoutContext { env };
-    document.layout(&mut ctx)
+/// Layout a tree into a collection of frames.
+pub fn layout(tree: &Tree, env: SharedEnv) -> Vec<Frame> {
+    tree.layout(&mut LayoutContext { env })
+}
+
+/// A tree of layout nodes.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Tree {
+    /// Runs of pages with the same properties.
+    pub runs: Vec<NodePages>,
+}
+
+impl Tree {
+    /// Layout the tree into a collection of frames.
+    pub fn layout(&self, ctx: &mut LayoutContext) -> Vec<Frame> {
+        self.runs.iter().flat_map(|run| run.layout(ctx)).collect()
+    }
+}
+
+/// A run of pages that all have the same properties.
+#[derive(Debug, Clone, PartialEq)]
+pub struct NodePages {
+    /// The size of each page.
+    pub size: Size,
+    /// The layout node that produces the actual pages (typically a
+    /// [`NodeStack`]).
+    pub child: Node,
+}
+
+impl NodePages {
+    /// Layout the page run.
+    pub fn layout(&self, ctx: &mut LayoutContext) -> Vec<Frame> {
+        let areas = Areas::repeat(self.size);
+        let layouted = self.child.layout(ctx, &areas);
+        layouted.frames()
+    }
+}
+
+/// Layout a node.
+pub trait Layout {
+    /// Layout the node into the given areas.
+    fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted;
 }
 
 /// The context for layouting.
@@ -33,22 +71,30 @@ pub struct LayoutContext {
     pub env: SharedEnv,
 }
 
-/// Layout a node.
-pub trait Layout {
-    /// Layout the node into the given areas.
-    fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted;
+/// An area into which content can be laid out.
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub struct Area {
+    /// The remaining size of this area.
+    pub rem: Size,
+    /// The full size this area once had (used for relative sizing).
+    pub full: Size,
 }
 
-/// A sequence of areas to layout into.
+impl Area {
+    /// Create a new area.
+    pub fn new(size: Size) -> Self {
+        Self { rem: size, full: size }
+    }
+}
+
+/// A collection of areas to layout into.
 #[derive(Debug, Clone, PartialEq)]
 pub struct Areas {
     /// The current area.
     pub current: Area,
-    /// The backlog of followup areas.
-    ///
-    /// _Note_: This works stack-like and not queue-like!
+    /// A stack of followup areas (the next area is the last element).
     pub backlog: Vec<Size>,
-    /// The last area that is repeated when the backlog is empty.
+    /// The final area that is repeated when the backlog is empty.
     pub last: Option<Size>,
 }
 
@@ -86,136 +132,81 @@ impl Areas {
     }
 }
 
-/// The area into which content can be laid out.
-#[derive(Debug, Copy, Clone, PartialEq)]
-pub struct Area {
-    /// The remaining size of this area.
-    pub rem: Size,
-    /// The full size this area once had (used for relative sizing).
-    pub full: Size,
-}
-
-impl Area {
-    /// Create a new area.
-    pub fn new(size: Size) -> Self {
-        Self { rem: size, full: size }
-    }
-}
-
-/// How to determine a container's size along an axis.
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub enum Expansion {
-    /// Fit the content.
-    Fit,
-    /// Fill the available space.
-    Fill,
-}
-
-impl Expansion {
-    /// Returns `Fill` if the condition is true and `Fit` otherwise.
-    pub fn fill_if(condition: bool) -> Self {
-        if condition { Self::Fill } else { Self::Fit }
-    }
-}
-
-/// The result of [layouting](Layout::layout) a node.
+/// The result of layouting a node.
 #[derive(Debug, Clone, PartialEq)]
 pub enum Layouted {
     /// Spacing that should be added to the parent.
     Spacing(Length),
     /// A layout that should be added to and aligned in the parent.
-    Layout(BoxLayout, BoxAlign),
+    Frame(Frame, ChildAlign),
     /// Multiple layouts.
-    Layouts(Vec<BoxLayout>, BoxAlign),
+    Frames(Vec<Frame>, ChildAlign),
 }
 
 impl Layouted {
-    /// Return all layouts contained in this variant (zero, one or arbitrarily
+    /// Return all frames contained in this variant (zero, one or arbitrarily
     /// many).
-    pub fn into_layouts(self) -> Vec<BoxLayout> {
+    pub fn frames(self) -> Vec<Frame> {
         match self {
             Self::Spacing(_) => vec![],
-            Self::Layout(layout, _) => vec![layout],
-            Self::Layouts(layouts, _) => layouts,
+            Self::Frame(frame, _) => vec![frame],
+            Self::Frames(frames, _) => frames,
         }
     }
 }
 
-/// A finished box with content at fixed positions.
+/// Whether to expand or shrink a node along an axis.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum Expansion {
+    /// Fit the content.
+    Fit,
+    /// Fill the available space.
+    Fill,
+}
+
+/// A finished layout with elements at fixed positions.
 #[derive(Debug, Clone, PartialEq)]
-pub struct BoxLayout {
-    /// The size of the box.
+pub struct Frame {
+    /// The size of the frame.
     pub size: Size,
     /// The elements composing this layout.
-    pub elements: Vec<(Point, LayoutElement)>,
+    pub elements: Vec<(Point, Element)>,
 }
 
-impl BoxLayout {
-    /// Create a new empty collection.
+impl Frame {
+    /// Create a new, empty frame.
     pub fn new(size: Size) -> Self {
         Self { size, elements: vec![] }
     }
 
     /// Add an element at a position.
-    pub fn push(&mut self, pos: Point, element: LayoutElement) {
+    pub fn push(&mut self, pos: Point, element: Element) {
         self.elements.push((pos, element));
     }
 
-    /// Add all elements of another collection, placing them relative to the
-    /// given position.
-    pub fn push_layout(&mut self, pos: Point, more: Self) {
-        for (subpos, element) in more.elements {
+    /// Add all elements of another frame, placing them relative to the given
+    /// position.
+    pub fn push_frame(&mut self, pos: Point, subframe: Self) {
+        for (subpos, element) in subframe.elements {
             self.push(pos + subpos, element);
         }
     }
 }
 
-/// A layout element, the basic building block layouts are composed of.
+/// The building block frames are composed of.
 #[derive(Debug, Clone, PartialEq)]
-pub enum LayoutElement {
+pub enum Element {
     /// Shaped text.
     Text(Shaped),
     /// An image.
-    Image(ImageElement),
+    Image(Image),
 }
 
-/// An image.
+/// An image element.
 #[derive(Debug, Clone, PartialEq)]
-pub struct ImageElement {
-    /// The image.
+pub struct Image {
+    /// The image resource.
     pub res: ResourceId,
-    /// The document size of the image.
+    /// The size of the image in the document.
     pub size: Size,
 }
-
-/// The top-level layout node.
-#[derive(Debug, Clone, PartialEq)]
-pub struct Document {
-    /// The runs of pages with same properties.
-    pub runs: Vec<Pages>,
-}
-
-impl Document {
-    /// Layout the document.
-    pub fn layout(&self, ctx: &mut LayoutContext) -> Vec<BoxLayout> {
-        self.runs.iter().flat_map(|run| run.layout(ctx)).collect()
-    }
-}
-
-/// A variable-length run of pages that all have the same properties.
-#[derive(Debug, Clone, PartialEq)]
-pub struct Pages {
-    /// The size of each page.
-    pub size: Size,
-    /// The layout node that produces the actual pages (typically a [`Stack`]).
-    pub child: LayoutNode,
-}
-
-impl Pages {
-    /// Layout the page run.
-    pub fn layout(&self, ctx: &mut LayoutContext) -> Vec<BoxLayout> {
-        let areas = Areas::repeat(self.size);
-        let layouted = self.child.layout(ctx, &areas);
-        layouted.into_layouts()
-    }
-}
diff --git a/src/layout/node.rs b/src/layout/node.rs
index 44767898..c945ee19 100644
--- a/src/layout/node.rs
+++ b/src/layout/node.rs
@@ -1,91 +1,89 @@
-//! Layout nodes.
-
 use std::any::Any;
 use std::fmt::{self, Debug, Formatter};
 
 use super::*;
 
-/// A self-contained, styled layout node.
+/// A self-contained layout node.
 #[derive(Clone, PartialEq)]
-pub enum LayoutNode {
-    /// A spacing node.
-    Spacing(Spacing),
+pub enum Node {
     /// A text node.
-    Text(Text),
-    /// A dynamic that can implement custom layouting behaviour.
-    Dyn(Dynamic),
+    Text(NodeText),
+    /// A spacing node.
+    Spacing(NodeSpacing),
+    /// A dynamic node that can implement custom layouting behaviour.
+    Any(NodeAny),
 }
 
-impl LayoutNode {
+impl Node {
     /// Create a new dynamic node.
-    pub fn dynamic<T>(inner: T) -> Self
+    pub fn any<T>(any: T) -> Self
     where
         T: Layout + Debug + Clone + PartialEq + 'static,
     {
-        Self::Dyn(Dynamic::new(inner))
+        Self::Any(NodeAny::new(any))
     }
 }
 
-impl Layout for LayoutNode {
+impl Layout for Node {
     fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted {
         match self {
             Self::Spacing(spacing) => spacing.layout(ctx, areas),
             Self::Text(text) => text.layout(ctx, areas),
-            Self::Dyn(dynamic) => dynamic.layout(ctx, areas),
+            Self::Any(any) => any.layout(ctx, areas),
         }
     }
 }
 
-impl Debug for LayoutNode {
+impl Debug for Node {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
             Self::Spacing(spacing) => spacing.fmt(f),
             Self::Text(text) => text.fmt(f),
-            Self::Dyn(dynamic) => dynamic.fmt(f),
+            Self::Any(any) => any.fmt(f),
         }
     }
 }
 
 /// A wrapper around a dynamic layouting node.
-pub struct Dynamic(Box<dyn Bounds>);
+pub struct NodeAny(Box<dyn Bounds>);
 
-impl Dynamic {
+impl NodeAny {
     /// Create a new instance from any node that satisifies the required bounds.
-    pub fn new<T>(inner: T) -> Self
+    pub fn new<T>(any: T) -> Self
     where
         T: Layout + Debug + Clone + PartialEq + 'static,
     {
-        Self(Box::new(inner))
+        Self(Box::new(any))
     }
 }
 
-impl Layout for Dynamic {
+impl Layout for NodeAny {
     fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted {
         self.0.layout(ctx, areas)
     }
 }
 
-impl Clone for Dynamic {
+impl Clone for NodeAny {
     fn clone(&self) -> Self {
         Self(self.0.dyn_clone())
     }
 }
 
-impl PartialEq for Dynamic {
+impl PartialEq for NodeAny {
     fn eq(&self, other: &Self) -> bool {
         self.0.dyn_eq(other.0.as_ref())
     }
 }
 
-impl Debug for Dynamic {
+impl Debug for NodeAny {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         self.0.fmt(f)
     }
 }
 
-impl From<Dynamic> for LayoutNode {
-    fn from(dynamic: Dynamic) -> Self {
-        Self::Dyn(dynamic)
+impl From<NodeAny> for Node {
+    fn from(dynamic: NodeAny) -> Self {
+        Self::Any(dynamic)
     }
 }
 
diff --git a/src/layout/pad.rs b/src/layout/pad.rs
index 00830a07..f947a7f5 100644
--- a/src/layout/pad.rs
+++ b/src/layout/pad.rs
@@ -1,26 +1,26 @@
 use super::*;
 use crate::geom::Linear;
 
-/// A node that pads its child at the sides.
+/// A node that adds padding to its child.
 #[derive(Debug, Clone, PartialEq)]
-pub struct Pad {
+pub struct NodePad {
     /// The amount of padding.
     pub padding: Sides<Linear>,
     /// The child node whose sides to pad.
-    pub child: LayoutNode,
+    pub child: Node,
 }
 
-impl Layout for Pad {
+impl Layout for NodePad {
     fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted {
-        let areas = shrink_areas(areas, self.padding);
+        let areas = shrink(areas, self.padding);
 
         let mut layouted = self.child.layout(ctx, &areas);
         match &mut layouted {
             Layouted::Spacing(_) => {}
-            Layouted::Layout(layout, _) => pad_layout(layout, self.padding),
-            Layouted::Layouts(layouts, _) => {
-                for layout in layouts {
-                    pad_layout(layout, self.padding);
+            Layouted::Frame(frame, _) => pad(frame, self.padding),
+            Layouted::Frames(frames, _) => {
+                for frame in frames {
+                    pad(frame, self.padding);
                 }
             }
         }
@@ -29,14 +29,14 @@ impl Layout for Pad {
     }
 }
 
-impl From<Pad> for LayoutNode {
-    fn from(pad: Pad) -> Self {
-        Self::dynamic(pad)
+impl From<NodePad> for Node {
+    fn from(pad: NodePad) -> Self {
+        Self::any(pad)
     }
 }
 
 /// Shrink all areas by the padding.
-fn shrink_areas(areas: &Areas, padding: Sides<Linear>) -> Areas {
+fn shrink(areas: &Areas, padding: Sides<Linear>) -> Areas {
     let shrink = |size| size - padding.resolve(size).size();
     Areas {
         current: Area {
@@ -49,12 +49,12 @@ fn shrink_areas(areas: &Areas, padding: Sides<Linear>) -> Areas {
 }
 
 /// Enlarge the box and move all elements inwards.
-fn pad_layout(layout: &mut BoxLayout, padding: Sides<Linear>) {
-    let padding = padding.resolve(layout.size);
+fn pad(frame: &mut Frame, padding: Sides<Linear>) {
+    let padding = padding.resolve(frame.size);
     let origin = Point::new(padding.left, padding.top);
 
-    layout.size += padding.size();
-    for (point, _) in &mut layout.elements {
+    frame.size += padding.size();
+    for (point, _) in &mut frame.elements {
         *point += origin;
     }
 }
diff --git a/src/layout/par.rs b/src/layout/par.rs
index 723f27cb..3a8e3969 100644
--- a/src/layout/par.rs
+++ b/src/layout/par.rs
@@ -2,69 +2,67 @@ use super::*;
 
 /// A node that arranges its children into a paragraph.
 #[derive(Debug, Clone, PartialEq)]
-pub struct Par {
+pub struct NodePar {
     /// The `main` and `cross` directions of this paragraph.
     ///
     /// The children are placed in lines along the `cross` direction. The lines
     /// are stacked along the `main` direction.
-    pub flow: Flow,
+    pub dirs: LayoutDirs,
     /// Whether to expand the cross axis to fill the area or to fit the content.
     pub cross_expansion: Expansion,
     /// The spacing to insert after each line.
     pub line_spacing: Length,
     /// The nodes to be arranged in a paragraph.
-    pub children: Vec<LayoutNode>,
+    pub children: Vec<Node>,
     /// How to align this paragraph in _its_ parent.
-    pub align: BoxAlign,
+    pub align: ChildAlign,
 }
 
-impl Layout for Par {
+impl Layout for NodePar {
     fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted {
         let mut layouter = ParLayouter::new(self, areas.clone());
         for child in &self.children {
             match child.layout(ctx, &layouter.areas) {
                 Layouted::Spacing(spacing) => layouter.push_spacing(spacing),
-                Layouted::Layout(layout, align) => {
-                    layouter.push_layout(layout, align.cross)
-                }
-                Layouted::Layouts(layouts, align) => {
-                    for layout in layouts {
-                        layouter.push_layout(layout, align.cross);
+                Layouted::Frame(frame, align) => layouter.push_frame(frame, align.cross),
+                Layouted::Frames(frames, align) => {
+                    for frame in frames {
+                        layouter.push_frame(frame, align.cross);
                     }
                 }
             }
         }
-        Layouted::Layouts(layouter.finish(), self.align)
+        Layouted::Frames(layouter.finish(), self.align)
     }
 }
 
-impl From<Par> for LayoutNode {
-    fn from(par: Par) -> Self {
-        Self::dynamic(par)
+impl From<NodePar> for Node {
+    fn from(par: NodePar) -> Self {
+        Self::any(par)
     }
 }
 
 struct ParLayouter<'a> {
-    par: &'a Par,
+    par: &'a NodePar,
     main: SpecAxis,
     cross: SpecAxis,
-    flow: Flow,
+    dirs: LayoutDirs,
     areas: Areas,
-    finished: Vec<BoxLayout>,
-    lines: Vec<(Length, BoxLayout, Align)>,
+    finished: Vec<Frame>,
+    lines: Vec<(Length, Frame, Align)>,
     lines_size: Gen<Length>,
-    run: Vec<(Length, BoxLayout, Align)>,
+    run: Vec<(Length, Frame, Align)>,
     run_size: Gen<Length>,
     run_ruler: Align,
 }
 
 impl<'a> ParLayouter<'a> {
-    fn new(par: &'a Par, areas: Areas) -> Self {
+    fn new(par: &'a NodePar, areas: Areas) -> Self {
         Self {
             par,
-            main: par.flow.main.axis(),
-            cross: par.flow.cross.axis(),
-            flow: par.flow,
+            main: par.dirs.main.axis(),
+            cross: par.dirs.cross.axis(),
+            dirs: par.dirs,
             areas,
             finished: vec![],
             lines: vec![],
@@ -80,7 +78,7 @@ impl<'a> ParLayouter<'a> {
         self.run_size.cross = (self.run_size.cross + amount).min(cross_max);
     }
 
-    fn push_layout(&mut self, layout: BoxLayout, align: Align) {
+    fn push_frame(&mut self, frame: Frame, align: Align) {
         if self.run_ruler > align {
             self.finish_run();
         }
@@ -88,16 +86,16 @@ impl<'a> ParLayouter<'a> {
         let fits = {
             let mut usable = self.areas.current.rem;
             *usable.get_mut(self.cross) -= self.run_size.cross;
-            usable.fits(layout.size)
+            usable.fits(frame.size)
         };
 
         if !fits {
             self.finish_run();
 
-            while !self.areas.current.rem.fits(layout.size) {
+            while !self.areas.current.rem.fits(frame.size) {
                 if self.areas.in_full_last() {
                     // TODO: Diagnose once the necessary spans exist.
-                    let _ = warning!("cannot fit box into any area");
+                    let _ = warning!("cannot fit frame into any area");
                     break;
                 } else {
                     self.finish_area();
@@ -105,8 +103,8 @@ impl<'a> ParLayouter<'a> {
             }
         }
 
-        let size = layout.size.switch(self.flow);
-        self.run.push((self.run_size.cross, layout, align));
+        let size = frame.size.switch(self.dirs);
+        self.run.push((self.run_size.cross, frame, align));
 
         self.run_size.cross += size.cross;
         self.run_size.main = self.run_size.main.max(size.main);
@@ -119,13 +117,13 @@ impl<'a> ParLayouter<'a> {
             Expansion::Fit => self.run_size.cross,
         });
 
-        let mut output = BoxLayout::new(full_size.switch(self.flow).to_size());
+        let mut output = Frame::new(full_size.switch(self.dirs).to_size());
 
-        for (before, layout, align) in std::mem::take(&mut self.run) {
-            let child_cross_size = layout.size.get(self.cross);
+        for (before, frame, align) in std::mem::take(&mut self.run) {
+            let child_cross_size = frame.size.get(self.cross);
 
             // Position along the cross axis.
-            let cross = align.resolve(if self.flow.cross.is_positive() {
+            let cross = align.resolve(if self.dirs.cross.is_positive() {
                 let after_with_self = self.run_size.cross - before;
                 before .. full_size.cross - after_with_self
             } else {
@@ -134,8 +132,8 @@ impl<'a> ParLayouter<'a> {
                 full_size.cross - before_with_self .. after
             });
 
-            let pos = Gen::new(Length::ZERO, cross).switch(self.flow).to_point();
-            output.push_layout(pos, layout);
+            let pos = Gen::new(Length::ZERO, cross).switch(self.dirs).to_point();
+            output.push_frame(pos, frame);
         }
 
         self.lines.push((self.lines_size.main, output, self.run_ruler));
@@ -151,27 +149,27 @@ impl<'a> ParLayouter<'a> {
 
     fn finish_area(&mut self) {
         let size = self.lines_size;
-        let mut output = BoxLayout::new(size.switch(self.flow).to_size());
+        let mut output = Frame::new(size.switch(self.dirs).to_size());
 
         for (before, run, cross_align) in std::mem::take(&mut self.lines) {
-            let child_size = run.size.switch(self.flow);
+            let child_size = run.size.switch(self.dirs);
 
             // Position along the main axis.
-            let main = if self.flow.main.is_positive() {
+            let main = if self.dirs.main.is_positive() {
                 before
             } else {
                 size.main - (before + child_size.main)
             };
 
             // Align along the cross axis.
-            let cross = cross_align.resolve(if self.flow.cross.is_positive() {
+            let cross = cross_align.resolve(if self.dirs.cross.is_positive() {
                 Length::ZERO .. size.cross - child_size.cross
             } else {
                 size.cross - child_size.cross .. Length::ZERO
             });
 
-            let pos = Gen::new(main, cross).switch(self.flow).to_point();
-            output.push_layout(pos, run);
+            let pos = Gen::new(main, cross).switch(self.dirs).to_point();
+            output.push_frame(pos, run);
         }
 
         self.finished.push(output);
@@ -180,7 +178,7 @@ impl<'a> ParLayouter<'a> {
         self.lines_size = Gen::ZERO;
     }
 
-    fn finish(mut self) -> Vec<BoxLayout> {
+    fn finish(mut self) -> Vec<Frame> {
         self.finish_run();
         self.finish_area();
         self.finished
diff --git a/src/layout/spacing.rs b/src/layout/spacing.rs
index c9a9c233..f0024fab 100644
--- a/src/layout/spacing.rs
+++ b/src/layout/spacing.rs
@@ -5,7 +5,7 @@ use crate::eval::Softness;
 
 /// A  spacing node.
 #[derive(Copy, Clone, PartialEq)]
-pub struct Spacing {
+pub struct NodeSpacing {
     /// The amount of spacing to insert.
     pub amount: Length,
     /// Defines how spacing interacts with surrounding spacing.
@@ -19,13 +19,13 @@ pub struct Spacing {
     pub softness: Softness,
 }
 
-impl Layout for Spacing {
+impl Layout for NodeSpacing {
     fn layout(&self, _: &mut LayoutContext, _: &Areas) -> Layouted {
         Layouted::Spacing(self.amount)
     }
 }
 
-impl Debug for Spacing {
+impl Debug for NodeSpacing {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self.softness {
             Softness::Soft => write!(f, "Soft({})", self.amount),
@@ -34,8 +34,8 @@ impl Debug for Spacing {
     }
 }
 
-impl From<Spacing> for LayoutNode {
-    fn from(spacing: Spacing) -> Self {
+impl From<NodeSpacing> for Node {
+    fn from(spacing: NodeSpacing) -> Self {
         Self::Spacing(spacing)
     }
 }
diff --git a/src/layout/stack.rs b/src/layout/stack.rs
index 9d2540e9..e98be7ed 100644
--- a/src/layout/stack.rs
+++ b/src/layout/stack.rs
@@ -1,65 +1,65 @@
 use super::*;
 
-/// A node that stacks and align its children.
+/// A node that stacks its children.
 #[derive(Debug, Clone, PartialEq)]
-pub struct Stack {
+pub struct NodeStack {
     /// The `main` and `cross` directions of this stack.
     ///
     /// The children are stacked along the `main` direction. The `cross`
     /// direction is required for aligning the children.
-    pub flow: Flow,
+    pub dirs: LayoutDirs,
     /// How to align this stack in _its_ parent.
-    pub align: BoxAlign,
+    pub align: ChildAlign,
     /// Whether to expand the axes to fill the area or to fit the content.
     pub expansion: Gen<Expansion>,
     /// The nodes to be stacked.
-    pub children: Vec<LayoutNode>,
+    pub children: Vec<Node>,
 }
 
-impl Layout for Stack {
+impl Layout for NodeStack {
     fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Layouted {
         let mut layouter = StackLayouter::new(self, areas.clone());
         for child in &self.children {
             match child.layout(ctx, &layouter.areas) {
                 Layouted::Spacing(spacing) => layouter.push_spacing(spacing),
-                Layouted::Layout(layout, align) => layouter.push_layout(layout, align),
-                Layouted::Layouts(layouts, align) => {
-                    for layout in layouts {
-                        layouter.push_layout(layout, align);
+                Layouted::Frame(frame, align) => layouter.push_frame(frame, align),
+                Layouted::Frames(frames, align) => {
+                    for frame in frames {
+                        layouter.push_frame(frame, align);
                     }
                 }
             }
         }
-        Layouted::Layouts(layouter.finish(), self.align)
+        Layouted::Frames(layouter.finish(), self.align)
     }
 }
 
-impl From<Stack> for LayoutNode {
-    fn from(stack: Stack) -> Self {
-        Self::dynamic(stack)
+impl From<NodeStack> for Node {
+    fn from(stack: NodeStack) -> Self {
+        Self::any(stack)
     }
 }
 
 struct StackLayouter<'a> {
-    stack: &'a Stack,
+    stack: &'a NodeStack,
     main: SpecAxis,
-    flow: Flow,
+    dirs: LayoutDirs,
     areas: Areas,
-    finished: Vec<BoxLayout>,
-    layouts: Vec<(Length, BoxLayout, BoxAlign)>,
+    finished: Vec<Frame>,
+    frames: Vec<(Length, Frame, ChildAlign)>,
     used: Gen<Length>,
     ruler: Align,
 }
 
 impl<'a> StackLayouter<'a> {
-    fn new(stack: &'a Stack, areas: Areas) -> Self {
+    fn new(stack: &'a NodeStack, areas: Areas) -> Self {
         Self {
             stack,
-            main: stack.flow.main.axis(),
-            flow: stack.flow,
+            main: stack.dirs.main.axis(),
+            dirs: stack.dirs,
             areas,
             finished: vec![],
-            layouts: vec![],
+            frames: vec![],
             used: Gen::ZERO,
             ruler: Align::Start,
         }
@@ -72,23 +72,23 @@ impl<'a> StackLayouter<'a> {
         self.used.main += capped;
     }
 
-    fn push_layout(&mut self, layout: BoxLayout, align: BoxAlign) {
+    fn push_frame(&mut self, frame: Frame, align: ChildAlign) {
         if self.ruler > align.main {
             self.finish_area();
         }
 
-        while !self.areas.current.rem.fits(layout.size) {
+        while !self.areas.current.rem.fits(frame.size) {
             if self.areas.in_full_last() {
                 // TODO: Diagnose once the necessary spans exist.
-                let _ = warning!("cannot fit box into any area");
+                let _ = warning!("cannot fit frame into any area");
                 break;
             } else {
                 self.finish_area();
             }
         }
 
-        let size = layout.size.switch(self.flow);
-        self.layouts.push((self.used.main, layout, align));
+        let size = frame.size.switch(self.dirs);
+        self.frames.push((self.used.main, frame, align));
 
         *self.areas.current.rem.get_mut(self.main) -= size.main;
         self.used.main += size.main;
@@ -98,7 +98,7 @@ impl<'a> StackLayouter<'a> {
 
     fn finish_area(&mut self) {
         let full_size = {
-            let full = self.areas.current.full.switch(self.flow);
+            let full = self.areas.current.full.switch(self.dirs);
             Gen::new(
                 match self.stack.expansion.main {
                     Expansion::Fill => full.main,
@@ -111,13 +111,13 @@ impl<'a> StackLayouter<'a> {
             )
         };
 
-        let mut output = BoxLayout::new(full_size.switch(self.flow).to_size());
+        let mut output = Frame::new(full_size.switch(self.dirs).to_size());
 
-        for (before, layout, align) in std::mem::take(&mut self.layouts) {
-            let child_size = layout.size.switch(self.flow);
+        for (before, frame, align) in std::mem::take(&mut self.frames) {
+            let child_size = frame.size.switch(self.dirs);
 
             // Align along the main axis.
-            let main = align.main.resolve(if self.flow.main.is_positive() {
+            let main = align.main.resolve(if self.dirs.main.is_positive() {
                 let after_with_self = self.used.main - before;
                 before .. full_size.main - after_with_self
             } else {
@@ -127,14 +127,14 @@ impl<'a> StackLayouter<'a> {
             });
 
             // Align along the cross axis.
-            let cross = align.cross.resolve(if self.flow.cross.is_positive() {
+            let cross = align.cross.resolve(if self.dirs.cross.is_positive() {
                 Length::ZERO .. full_size.cross - child_size.cross
             } else {
                 full_size.cross - child_size.cross .. Length::ZERO
             });
 
-            let pos = Gen::new(main, cross).switch(self.flow).to_point();
-            output.push_layout(pos, layout);
+            let pos = Gen::new(main, cross).switch(self.dirs).to_point();
+            output.push_frame(pos, frame);
         }
 
         self.finished.push(output);
@@ -144,7 +144,7 @@ impl<'a> StackLayouter<'a> {
         self.ruler = Align::Start;
     }
 
-    fn finish(mut self) -> Vec<BoxLayout> {
+    fn finish(mut self) -> Vec<Frame> {
         self.finish_area();
         self.finished
     }
diff --git a/src/layout/text.rs b/src/layout/text.rs
index 56b2328e..cfd83372 100644
--- a/src/layout/text.rs
+++ b/src/layout/text.rs
@@ -8,11 +8,11 @@ use crate::shaping;
 
 /// A text node.
 #[derive(Clone, PartialEq)]
-pub struct Text {
+pub struct NodeText {
     /// The text.
     pub text: String,
     /// How to align this text node in its parent.
-    pub align: BoxAlign,
+    pub align: ChildAlign,
     /// The text direction.
     pub dir: Dir,
     /// The font size.
@@ -23,15 +23,15 @@ pub struct Text {
     pub variant: FontVariant,
 }
 
-impl Layout for Text {
+impl Layout for NodeText {
     fn layout(&self, ctx: &mut LayoutContext, _: &Areas) -> Layouted {
         let mut env = ctx.env.borrow_mut();
-        Layouted::Layout(
+        Layouted::Frame(
             shaping::shape(
-                &mut env.fonts,
                 &self.text,
                 self.dir,
                 self.font_size,
+                &mut env.fonts,
                 &self.families,
                 self.variant,
             ),
@@ -40,14 +40,14 @@ impl Layout for Text {
     }
 }
 
-impl Debug for Text {
+impl Debug for NodeText {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "Text({})", self.text)
     }
 }
 
-impl From<Text> for LayoutNode {
-    fn from(text: Text) -> Self {
+impl From<NodeText> for Node {
+    fn from(text: NodeText) -> Self {
         Self::Text(text)
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index d471b09d..15d68803 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,23 +5,23 @@
 //!   [iterator of tokens][tokens]. This token stream is [parsed] into a [syntax
 //!   tree]. The structures describing the tree can be found in the [syntax]
 //!   module.
-//! - **Evaluation:** The next step is to [evaluate] the parsed "script" to a
-//!   [document], a high-level, fully styled representation. The nodes of the
-//!   document tree are fully self-contained and order-independent and thus much
+//! - **Evaluation:** The next step is to [evaluate] the parsed "script" into a
+//!   [layout tree], a high-level, fully styled representation. The nodes of
+//!   this tree are fully self-contained and order-independent and thus much
 //!   better suited for layouting than the syntax tree.
-//! - **Layouting:** The next step is to [layout] the document into a portable
-//!   version of the typeset document. The output of this is a vector of
-//!   [`BoxLayout`]s (corresponding to pages), ready for exporting.
+//! - **Layouting:** Next, the tree is to [layouted] into a portable version of
+//!   the typeset document. The output of this is a vector of [`Frame`]s
+//!   (corresponding to pages), ready for exporting.
 //! - **Exporting:** The finished layout can be exported into a supported
 //!   format. Submodules for these formats are located in the [export] module.
 //!   Currently, the only supported output format is [_PDF_].
 //!
 //! [tokens]: parse::Tokens
 //! [parsed]: parse::parse
-//! [syntax tree]: syntax::SynTree
+//! [syntax tree]: syntax::Tree
 //! [evaluate]: eval::eval
-//! [document]: layout::Document
-//! [layout]: layout::layout
+//! [layout tree]: layout::Tree
+//! [layouted]: layout::layout
 //! [_PDF_]: export::pdf
 
 #[macro_use]
@@ -46,13 +46,13 @@ use std::rc::Rc;
 use crate::diag::{Feedback, Pass};
 use crate::env::SharedEnv;
 use crate::eval::State;
-use crate::layout::BoxLayout;
+use crate::layout::Frame;
 
-/// Process _Typst_ source code directly into a collection of layouts.
-pub fn typeset(src: &str, env: SharedEnv, state: State) -> Pass<Vec<BoxLayout>> {
-    let Pass { output: tree, feedback: f1 } = parse::parse(src);
-    let Pass { output: document, feedback: f2 } =
-        eval::eval(&tree, Rc::clone(&env), state);
-    let layouts = layout::layout(&document, env);
-    Pass::new(layouts, Feedback::join(f1, f2))
+/// Process _Typst_ source code directly into a collection of frames.
+pub fn typeset(src: &str, env: SharedEnv, state: State) -> Pass<Vec<Frame>> {
+    let Pass { output: syntax_tree, feedback: f1 } = parse::parse(src);
+    let Pass { output: layout_tree, feedback: f2 } =
+        eval::eval(&syntax_tree, Rc::clone(&env), state);
+    let frames = layout::layout(&layout_tree, env);
+    Pass::new(frames, Feedback::join(f1, f2))
 }
diff --git a/src/library/insert.rs b/src/library/insert.rs
index 587f96dc..7d95afe3 100644
--- a/src/library/insert.rs
+++ b/src/library/insert.rs
@@ -22,7 +22,7 @@ pub fn image(ctx: &mut EvalContext, args: &mut Args) -> Value {
         if let Some((res, img)) = loaded {
             let dimensions = img.buf.dimensions();
             drop(env);
-            ctx.push(Image {
+            ctx.push(NodeImage {
                 res,
                 dimensions,
                 width,
@@ -40,7 +40,7 @@ pub fn image(ctx: &mut EvalContext, args: &mut Args) -> Value {
 
 /// An image node.
 #[derive(Debug, Clone, PartialEq)]
-struct Image {
+struct NodeImage {
     /// The resource id of the image file.
     res: ResourceId,
     /// The pixel dimensions of the image.
@@ -50,10 +50,10 @@ struct Image {
     /// The fixed height, if any.
     height: Option<Linear>,
     /// How to align this image node in its parent.
-    align: BoxAlign,
+    align: ChildAlign,
 }
 
-impl Layout for Image {
+impl Layout for NodeImage {
     fn layout(&self, _: &mut LayoutContext, areas: &Areas) -> Layouted {
         let Area { rem, full } = areas.current;
         let pixel_ratio = (self.dimensions.0 as f64) / (self.dimensions.1 as f64);
@@ -76,18 +76,15 @@ impl Layout for Image {
             }
         };
 
-        let mut boxed = BoxLayout::new(size);
-        boxed.push(
-            Point::ZERO,
-            LayoutElement::Image(ImageElement { res: self.res, size }),
-        );
+        let mut frame = Frame::new(size);
+        frame.push(Point::ZERO, Element::Image(Image { res: self.res, size }));
 
-        Layouted::Layout(boxed, self.align)
+        Layouted::Frame(frame, self.align)
     }
 }
 
-impl From<Image> for LayoutNode {
-    fn from(image: Image) -> Self {
-        Self::dynamic(image)
+impl From<NodeImage> for Node {
+    fn from(image: NodeImage) -> Self {
+        Self::any(image)
     }
 }
diff --git a/src/library/layout.rs b/src/library/layout.rs
index ac152d07..e469c9be 100644
--- a/src/library/layout.rs
+++ b/src/library/layout.rs
@@ -1,5 +1,5 @@
 use crate::eval::Softness;
-use crate::layout::{Expansion, Fixed, Spacing, Stack};
+use crate::layout::{Expansion, NodeFixed, NodeSpacing, NodeStack};
 use crate::paper::{Paper, PaperClass};
 use crate::prelude::*;
 
@@ -45,8 +45,8 @@ pub fn align(ctx: &mut EvalContext, args: &mut Args) -> Value {
         // Check whether we know which axis this alignment belongs to.
         if let Some(axis) = axis {
             // We know the axis.
-            let gen_axis = axis.switch(ctx.state.flow);
-            let gen_align = arg.switch(ctx.state.flow);
+            let gen_axis = axis.switch(ctx.state.dirs);
+            let gen_align = arg.switch(ctx.state.dirs);
 
             if arg.axis().map_or(false, |a| a != axis) {
                 ctx.diag(error!(span, "invalid alignment for {} axis", axis));
@@ -132,7 +132,7 @@ impl Alignment {
 impl Switch for Alignment {
     type Other = Align;
 
-    fn switch(self, flow: Flow) -> Self::Other {
+    fn switch(self, dirs: LayoutDirs) -> Self::Other {
         let get = |dir: Dir, at_positive_start| {
             if dir.is_positive() == at_positive_start {
                 Align::Start
@@ -141,12 +141,12 @@ impl Switch for Alignment {
             }
         };
 
-        let flow = flow.switch(flow);
+        let dirs = dirs.switch(dirs);
         match self {
-            Self::Left => get(flow.horizontal, true),
-            Self::Right => get(flow.horizontal, false),
-            Self::Top => get(flow.vertical, true),
-            Self::Bottom => get(flow.vertical, false),
+            Self::Left => get(dirs.horizontal, true),
+            Self::Right => get(dirs.horizontal, false),
+            Self::Top => get(dirs.vertical, true),
+            Self::Bottom => get(dirs.vertical, false),
             Self::Center => Align::Center,
         }
     }
@@ -169,9 +169,9 @@ pub fn boxed(ctx: &mut EvalContext, args: &mut Args) -> Value {
     let main = args.get(ctx, "main-dir");
     let cross = args.get(ctx, "cross-dir");
 
-    ctx.set_flow(Gen::new(main, cross));
+    ctx.set_dirs(Gen::new(main, cross));
 
-    let flow = ctx.state.flow;
+    let dirs = ctx.state.dirs;
     let align = ctx.state.align;
 
     ctx.start_content_group();
@@ -182,19 +182,14 @@ pub fn boxed(ctx: &mut EvalContext, args: &mut Args) -> Value {
 
     let children = ctx.end_content_group();
 
-    ctx.push(Fixed {
+    let fill_if = |c| if c { Expansion::Fill } else { Expansion::Fit };
+    let expansion =
+        Spec::new(fill_if(width.is_some()), fill_if(height.is_some())).switch(dirs);
+
+    ctx.push(NodeFixed {
         width,
         height,
-        child: LayoutNode::dynamic(Stack {
-            flow,
-            align,
-            expansion: Spec::new(
-                Expansion::fill_if(width.is_some()),
-                Expansion::fill_if(height.is_some()),
-            )
-            .switch(flow),
-            children,
-        }),
+        child: Node::any(NodeStack { dirs, align, expansion, children }),
     });
 
     ctx.state = snapshot;
@@ -227,8 +222,8 @@ fn spacing(ctx: &mut EvalContext, args: &mut Args, axis: SpecAxis) -> Value {
 
     if let Some(linear) = spacing {
         let amount = linear.resolve(ctx.state.font.font_size());
-        let spacing = Spacing { amount, softness: Softness::Hard };
-        if axis == ctx.state.flow.main.axis() {
+        let spacing = NodeSpacing { amount, softness: Softness::Hard };
+        if axis == ctx.state.dirs.main.axis() {
             ctx.end_par_group();
             ctx.push(spacing);
             ctx.start_par_group();
@@ -305,7 +300,7 @@ pub fn page(ctx: &mut EvalContext, args: &mut Args) -> Value {
     let main = args.get(ctx, "main-dir");
     let cross = args.get(ctx, "cross-dir");
 
-    ctx.set_flow(Gen::new(main, cross));
+    ctx.set_dirs(Gen::new(main, cross));
 
     let mut softness = ctx.end_page_group(|_| false);
     if let Some(body) = args.find::<ValueContent>(ctx) {
diff --git a/src/main.rs b/src/main.rs
index 213734d7..4746bc0c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -49,7 +49,7 @@ fn main() -> anyhow::Result<()> {
 
     let state = State::default();
     let Pass {
-        output: layouts,
+        output: frames,
         feedback: Feedback { mut diags, .. },
     } = typeset(&src, Rc::clone(&env), state);
 
@@ -72,7 +72,7 @@ fn main() -> anyhow::Result<()> {
         }
     }
 
-    let pdf_data = pdf::export(&layouts, &env.borrow());
+    let pdf_data = pdf::export(&frames, &env.borrow());
     fs::write(&dest_path, pdf_data).context("Failed to write PDF file.")?;
 
     Ok(())
diff --git a/src/paper.rs b/src/paper.rs
index 21f54756..bbe07803 100644
--- a/src/paper.rs
+++ b/src/paper.rs
@@ -5,7 +5,7 @@ use crate::geom::{Length, Linear, Relative, Sides, Size};
 /// Specification of a paper.
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct Paper {
-    /// The kind of paper, which defines the default margins.
+    /// The broad class this paper belongs to.
     pub class: PaperClass,
     /// The width of the paper in millimeters.
     pub width: f64,
@@ -25,7 +25,7 @@ impl Paper {
     }
 }
 
-/// Paper classes define default margins for a class of related papers.
+/// Defines default margins for a class of related papers.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum PaperClass {
     Custom,
diff --git a/src/parse/collection.rs b/src/parse/collection.rs
index db267dbe..889cfb0f 100644
--- a/src/parse/collection.rs
+++ b/src/parse/collection.rs
@@ -2,7 +2,7 @@ use super::*;
 use crate::diag::Deco;
 
 /// Parse the arguments to a function call.
-pub fn arguments(p: &mut Parser) -> Arguments {
+pub fn arguments(p: &mut Parser) -> ExprArgs {
     collection(p, vec![])
 }
 
@@ -74,7 +74,7 @@ trait Collection {
     fn push_comma(&mut self) {}
 }
 
-impl Collection for Arguments {
+impl Collection for ExprArgs {
     fn push_arg(&mut self, _: &mut Parser, arg: Spanned<Argument>) {
         self.push(arg.v);
     }
@@ -85,17 +85,17 @@ impl Collection for Arguments {
 enum State {
     Unknown,
     Expr(Spanned<Expr>),
-    Array(Array),
-    Dict(Dict),
+    Array(ExprArray),
+    Dict(ExprDict),
 }
 
 impl State {
     fn into_expr(self) -> Expr {
         match self {
-            Self::Unknown => Expr::Lit(Lit::Array(vec![])),
+            Self::Unknown => Expr::Array(vec![]),
             Self::Expr(expr) => expr.v,
-            Self::Array(array) => Expr::Lit(Lit::Array(array)),
-            Self::Dict(dict) => Expr::Lit(Lit::Dict(dict)),
+            Self::Array(array) => Expr::Array(array),
+            Self::Dict(dict) => Expr::Dict(dict),
         }
     }
 }
diff --git a/src/parse/lines.rs b/src/parse/lines.rs
index be120d8a..d1a6c781 100644
--- a/src/parse/lines.rs
+++ b/src/parse/lines.rs
@@ -1,5 +1,3 @@
-//! Conversion of byte positions to line/column locations.
-
 use super::Scanner;
 use crate::syntax::{Location, Offset, Pos};
 
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 912a34d0..e6cac17f 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -22,13 +22,13 @@ use crate::syntax::*;
 use collection::{arguments, parenthesized};
 
 /// Parse a string of source code.
-pub fn parse(src: &str) -> Pass<SynTree> {
+pub fn parse(src: &str) -> Pass<Tree> {
     let mut p = Parser::new(src);
     Pass::new(tree(&mut p), p.finish())
 }
 
 /// Parse a syntax tree.
-fn tree(p: &mut Parser) -> SynTree {
+fn tree(p: &mut Parser) -> Tree {
     // We keep track of whether we are at the start of a block or paragraph
     // to know whether headings are allowed.
     let mut at_start = true;
@@ -36,8 +36,8 @@ fn tree(p: &mut Parser) -> SynTree {
     while !p.eof() {
         if let Some(node) = p.span_if(|p| node(p, at_start)) {
             match node.v {
-                SynNode::Parbreak => at_start = true,
-                SynNode::Space => {}
+                Node::Parbreak => at_start = true,
+                Node::Space => {}
                 _ => at_start = false,
             }
             tree.push(node);
@@ -47,42 +47,42 @@ fn tree(p: &mut Parser) -> SynTree {
 }
 
 /// Parse a syntax node.
-fn node(p: &mut Parser, at_start: bool) -> Option<SynNode> {
+fn node(p: &mut Parser, at_start: bool) -> Option<Node> {
     let node = match p.peek()? {
         Token::Space(newlines) => {
             if newlines < 2 {
-                SynNode::Space
+                Node::Space
             } else {
-                SynNode::Parbreak
+                Node::Parbreak
             }
         }
-        Token::Text(text) => SynNode::Text(text.into()),
+        Token::Text(text) => Node::Text(text.into()),
 
         Token::LineComment(_) | Token::BlockComment(_) => {
             p.eat();
             return None;
         }
 
-        Token::Star => SynNode::Strong,
-        Token::Underscore => SynNode::Emph,
-        Token::Tilde => SynNode::Text("\u{00A0}".into()),
-        Token::Backslash => SynNode::Linebreak,
+        Token::Star => Node::Strong,
+        Token::Underscore => Node::Emph,
+        Token::Tilde => Node::Text("\u{00A0}".into()),
+        Token::Backslash => Node::Linebreak,
         Token::Hashtag => {
             if at_start {
-                return Some(SynNode::Heading(heading(p)));
+                return Some(Node::Heading(heading(p)));
             } else {
-                SynNode::Text(p.get(p.peek_span()).into())
+                Node::Text(p.get(p.peek_span()).into())
             }
         }
-        Token::Raw(t) => SynNode::Raw(raw(p, t)),
-        Token::UnicodeEscape(t) => SynNode::Text(unicode_escape(p, t)),
+        Token::Raw(t) => Node::Raw(raw(p, t)),
+        Token::UnicodeEscape(t) => Node::Text(unicode_escape(p, t)),
 
         Token::LeftBracket => {
-            return Some(SynNode::Expr(Expr::Call(bracket_call(p))));
+            return Some(Node::Expr(Expr::Call(bracket_call(p))));
         }
 
         Token::LeftBrace => {
-            return Some(SynNode::Expr(block_expr(p)?));
+            return Some(Node::Expr(block_expr(p)?));
         }
 
         _ => {
@@ -189,15 +189,15 @@ fn bracket_call(p: &mut Parser) -> ExprCall {
     p.end_group();
 
     if p.peek() == Some(Token::LeftBracket) {
-        let body = p.span(|p| Expr::Lit(Lit::Content(bracket_body(p))));
+        let body = p.span(|p| Expr::Content(bracket_body(p)));
         inner.span.expand(body.span);
         inner.v.args.v.push(Argument::Pos(body));
     }
 
     while let Some(mut top) = outer.pop() {
         let span = inner.span;
-        let node = inner.map(|c| SynNode::Expr(Expr::Call(c)));
-        let expr = Expr::Lit(Lit::Content(vec![node])).with_span(span);
+        let node = inner.map(|c| Node::Expr(Expr::Call(c)));
+        let expr = Expr::Content(vec![node]).with_span(span);
         top.v.args.v.push(Argument::Pos(expr));
         inner = top;
     }
@@ -227,7 +227,7 @@ fn bracket_subheader(p: &mut Parser) -> ExprCall {
 }
 
 /// Parse the body of a bracketed function call.
-fn bracket_body(p: &mut Parser) -> SynTree {
+fn bracket_body(p: &mut Parser) -> Tree {
     p.push_mode(TokenMode::Body);
     p.start_group(Group::Bracket);
     let tree = tree(p);
@@ -299,13 +299,13 @@ fn value(p: &mut Parser) -> Option<Expr> {
     let expr = match p.peek() {
         // Bracketed function call.
         Some(Token::LeftBracket) => {
-            let node = p.span(|p| SynNode::Expr(Expr::Call(bracket_call(p))));
-            return Some(Expr::Lit(Lit::Content(vec![node])));
+            let node = p.span(|p| Node::Expr(Expr::Call(bracket_call(p))));
+            return Some(Expr::Content(vec![node]));
         }
 
         // Content expression.
         Some(Token::LeftBrace) => {
-            return Some(Expr::Lit(Lit::Content(content(p))));
+            return Some(Expr::Content(content(p)));
         }
 
         // Dictionary or just a parenthesized expression.
@@ -345,7 +345,7 @@ fn value(p: &mut Parser) -> Option<Expr> {
 }
 
 // Parse a content value: `{...}`.
-fn content(p: &mut Parser) -> SynTree {
+fn content(p: &mut Parser) -> Tree {
     p.push_mode(TokenMode::Body);
     p.start_group(Group::Brace);
     let tree = tree(p);
diff --git a/src/parse/resolve.rs b/src/parse/resolve.rs
index 051bc7d5..d6c6d8a4 100644
--- a/src/parse/resolve.rs
+++ b/src/parse/resolve.rs
@@ -1,5 +1,3 @@
-//! Resolve strings and raw blocks.
-
 use super::{is_newline, Scanner};
 use crate::syntax::{Ident, NodeRaw};
 
diff --git a/src/parse/scanner.rs b/src/parse/scanner.rs
index 69ad2138..cc23a612 100644
--- a/src/parse/scanner.rs
+++ b/src/parse/scanner.rs
@@ -1,9 +1,7 @@
-//! Low-level char-based scanner.
-
 use std::fmt::{self, Debug, Formatter};
 use std::slice::SliceIndex;
 
-/// A low-level featureful char-based scanner.
+/// A featureful char-based scanner.
 #[derive(Clone)]
 pub struct Scanner<'s> {
     src: &'s str,
diff --git a/src/parse/tests.rs b/src/parse/tests.rs
index 0c8998b5..d01d09a5 100644
--- a/src/parse/tests.rs
+++ b/src/parse/tests.rs
@@ -9,7 +9,7 @@ use crate::geom::Unit;
 use crate::syntax::*;
 
 use BinOp::*;
-use SynNode::{Emph, Linebreak, Parbreak, Space, Strong};
+use Node::{Emph, Linebreak, Parbreak, Space, Strong};
 use UnOp::*;
 
 macro_rules! t {
@@ -82,16 +82,16 @@ macro_rules! into {
     };
 }
 
-fn Text(text: &str) -> SynNode {
-    SynNode::Text(text.into())
+fn Text(text: &str) -> Node {
+    Node::Text(text.into())
 }
 
-fn Heading(level: impl Into<Spanned<u8>>, contents: SynTree) -> SynNode {
-    SynNode::Heading(NodeHeading { level: level.into(), contents })
+fn Heading(level: impl Into<Spanned<u8>>, contents: Tree) -> Node {
+    Node::Heading(NodeHeading { level: level.into(), contents })
 }
 
-fn Raw(lang: Option<&str>, lines: &[&str], inline: bool) -> SynNode {
-    SynNode::Raw(NodeRaw {
+fn Raw(lang: Option<&str>, lines: &[&str], inline: bool) -> Node {
+    Node::Raw(NodeRaw {
         lang: lang.map(|id| Ident(id.into())),
         lines: lines.iter().map(ToString::to_string).collect(),
         inline,
@@ -130,8 +130,8 @@ fn Str(string: &str) -> Expr {
     Expr::Lit(Lit::Str(string.to_string()))
 }
 
-fn Block(expr: Expr) -> SynNode {
-    SynNode::Expr(expr)
+fn Block(expr: Expr) -> Node {
+    Node::Expr(expr)
 }
 
 fn Binary(
@@ -157,7 +157,7 @@ macro_rules! Array {
     (@$($expr:expr),* $(,)?) => {
         vec![$(into!($expr)),*]
     };
-    ($($tts:tt)*) => (Expr::Lit(Lit::Array(Array![@$($tts)*])));
+    ($($tts:tt)*) => (Expr::Array(Array![@$($tts)*]));
 }
 
 macro_rules! Dict {
@@ -167,7 +167,7 @@ macro_rules! Dict {
             expr: into!($expr)
         }),*]
     };
-    ($($tts:tt)*) => (Expr::Lit(Lit::Dict(Dict![@$($tts)*])));
+    ($($tts:tt)*) => (Expr::Dict(Dict![@$($tts)*]));
 }
 
 macro_rules! Args {
@@ -187,7 +187,7 @@ macro_rules! Args {
 
 macro_rules! Content {
     (@$($node:expr),* $(,)?) => (vec![$(into!($node)),*]);
-    ($($tts:tt)*) => (Expr::Lit(Lit::Content(Content![@$($tts)*])));
+    ($($tts:tt)*) => (Expr::Content(Content![@$($tts)*]));
 }
 
 macro_rules! Call {
@@ -201,7 +201,7 @@ macro_rules! Call {
         }
     };
     (@$($tts:tt)*) => (Expr::Call(Call!(@@$($tts)*)));
-    ($($tts:tt)*) => (SynNode::Expr(Call!(@$($tts)*)));
+    ($($tts:tt)*) => (Node::Expr(Call!(@$($tts)*)));
 }
 
 #[test]
diff --git a/src/parse/tokens.rs b/src/parse/tokens.rs
index a9692a58..ff7f11bd 100644
--- a/src/parse/tokens.rs
+++ b/src/parse/tokens.rs
@@ -1,5 +1,3 @@
-//! Tokenization.
-
 use std::fmt::{self, Debug, Formatter};
 
 use super::{is_newline, Scanner};
diff --git a/src/prelude.rs b/src/prelude.rs
index 5d446e8c..1db0d5b0 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -8,7 +8,7 @@ pub use crate::eval::{
 };
 pub use crate::geom::*;
 #[doc(no_inline)]
-pub use crate::layout::LayoutNode;
+pub use crate::layout::Node;
 #[doc(no_inline)]
-pub use crate::syntax::{Span, Spanned, SynTree, WithSpan};
-pub use crate::{error, warning};
+pub use crate::syntax::{Span, Spanned, WithSpan};
+pub use crate::{error, impl_type, warning};
diff --git a/src/shaping.rs b/src/shaping.rs
index c42cd0ac..722d103a 100644
--- a/src/shaping.rs
+++ b/src/shaping.rs
@@ -11,7 +11,7 @@ use ttf_parser::{Face, GlyphId};
 
 use crate::font::FontLoader;
 use crate::geom::{Dir, Length, Point, Size};
-use crate::layout::{BoxLayout, LayoutElement};
+use crate::layout::{Element, Frame};
 
 /// A shaped run of text.
 #[derive(Clone, PartialEq)]
@@ -31,13 +31,13 @@ pub struct Shaped {
 
 impl Shaped {
     /// Create a new shape run with empty `text`, `glyphs` and `offsets`.
-    pub fn new(face: FaceId, size: Length) -> Self {
+    pub fn new(face: FaceId, font_size: Length) -> Self {
         Self {
             text: String::new(),
             face,
             glyphs: vec![],
             offsets: vec![],
-            font_size: size,
+            font_size,
         }
     }
 
@@ -58,16 +58,16 @@ impl Debug for Shaped {
     }
 }
 
-/// Shape text into a box containing [`Shaped`] runs.
+/// Shape text into a frame containing [`Shaped`] runs.
 pub fn shape(
-    loader: &mut FontLoader,
     text: &str,
     dir: Dir,
     font_size: Length,
+    loader: &mut FontLoader,
     fallback: &FallbackTree,
     variant: FontVariant,
-) -> BoxLayout {
-    let mut layout = BoxLayout::new(Size::new(Length::ZERO, font_size));
+) -> Frame {
+    let mut frame = Frame::new(Size::new(Length::ZERO, font_size));
     let mut shaped = Shaped::new(FaceId::MAX, font_size);
     let mut offset = Length::ZERO;
 
@@ -91,9 +91,9 @@ pub fn shape(
 
             // Flush the buffer if we change the font face.
             if shaped.face != id && !shaped.text.is_empty() {
-                let pos = Point::new(layout.size.width, Length::ZERO);
-                layout.push(pos, LayoutElement::Text(shaped));
-                layout.size.width += offset;
+                let pos = Point::new(frame.size.width, Length::ZERO);
+                frame.push(pos, Element::Text(shaped));
+                frame.size.width += offset;
                 shaped = Shaped::new(FaceId::MAX, font_size);
                 offset = Length::ZERO;
             }
@@ -108,12 +108,12 @@ pub fn shape(
 
     // Flush the last buffered parts of the word.
     if !shaped.text.is_empty() {
-        let pos = Point::new(layout.size.width, Length::ZERO);
-        layout.push(pos, LayoutElement::Text(shaped));
-        layout.size.width += offset;
+        let pos = Point::new(frame.size.width, Length::ZERO);
+        frame.push(pos, Element::Text(shaped));
+        frame.size.width += offset;
     }
 
-    layout
+    frame
 }
 
 /// Looks up the glyph for `c` and returns its index alongside its width at the
diff --git a/src/syntax/expr.rs b/src/syntax/expr.rs
index 905ade04..94d07b07 100644
--- a/src/syntax/expr.rs
+++ b/src/syntax/expr.rs
@@ -1,5 +1,3 @@
-//! Expressions.
-
 use super::*;
 use crate::color::RgbaColor;
 use crate::geom::Unit;
@@ -7,7 +5,7 @@ use crate::geom::Unit;
 /// An expression.
 #[derive(Debug, Clone, PartialEq)]
 pub enum Expr {
-    /// A literal: `true`, `1cm`, `"hi"`, `{_Hey!_}`.
+    /// A literal: `true`, `1cm`, `"hi"`.
     Lit(Lit),
     /// An invocation of a function: `[foo ...]`, `foo(...)`.
     Call(ExprCall),
@@ -15,6 +13,12 @@ pub enum Expr {
     Unary(ExprUnary),
     /// A binary operation: `a + b`, `a / b`.
     Binary(ExprBinary),
+    /// An array expression: `(1, "hi", 12cm)`.
+    Array(ExprArray),
+    /// A dictionary expression: `(color: #f79143, pattern: dashed)`.
+    Dict(ExprDict),
+    /// A content expression: `{*Hello* there!}`.
+    Content(ExprContent),
 }
 
 /// An invocation of a function: `[foo ...]`, `foo(...)`.
@@ -23,14 +27,14 @@ pub struct ExprCall {
     /// The name of the function.
     pub name: Spanned<Ident>,
     /// The arguments to the function.
-    pub args: Spanned<Arguments>,
+    pub args: Spanned<ExprArgs>,
 }
 
 /// The arguments to a function: `12, draw: false`.
 ///
 /// In case of a bracketed invocation with a body, the body is _not_
 /// included in the span for the sake of clearer error messages.
-pub type Arguments = Vec<Argument>;
+pub type ExprArgs = Vec<Argument>;
 
 /// An argument to a function call: `12` or `draw: false`.
 #[derive(Debug, Clone, PartialEq)]
@@ -41,6 +45,15 @@ pub enum Argument {
     Named(Named),
 }
 
+/// A pair of a name and an expression: `pattern: dashed`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Named {
+    /// The name: `pattern`.
+    pub name: Spanned<Ident>,
+    /// The right-hand side of the pair: `dashed`.
+    pub expr: Spanned<Expr>,
+}
+
 /// A unary operation: `-x`.
 #[derive(Debug, Clone, PartialEq)]
 pub struct ExprUnary {
@@ -81,6 +94,15 @@ pub enum BinOp {
     Div,
 }
 
+/// An array expression: `(1, "hi", 12cm)`.
+pub type ExprArray = SpanVec<Expr>;
+
+/// A dictionary expression: `(color: #f79143, pattern: dashed)`.
+pub type ExprDict = Vec<Named>;
+
+/// A content expression: `{*Hello* there!}`.
+pub type ExprContent = Tree;
+
 /// A literal.
 #[derive(Debug, Clone, PartialEq)]
 pub enum Lit {
@@ -103,25 +125,4 @@ pub enum Lit {
     Color(RgbaColor),
     /// A string literal: `"hello!"`.
     Str(String),
-    /// An array literal: `(1, "hi", 12cm)`.
-    Array(Array),
-    /// A dictionary literal: `(color: #f79143, pattern: dashed)`.
-    Dict(Dict),
-    /// A content literal: `{*Hello* there!}`.
-    Content(SynTree),
-}
-
-/// An array literal: `(1, "hi", 12cm)`.
-pub type Array = SpanVec<Expr>;
-
-/// A dictionary literal: `(color: #f79143, pattern: dashed)`.
-pub type Dict = Vec<Named>;
-
-/// A pair of a name and an expression: `pattern: dashed`.
-#[derive(Debug, Clone, PartialEq)]
-pub struct Named {
-    /// The name: `pattern`.
-    pub name: Spanned<Ident>,
-    /// The right-hand side of the pair: `dashed`.
-    pub expr: Spanned<Expr>,
 }
diff --git a/src/syntax/ident.rs b/src/syntax/ident.rs
index 4f3668c0..3cb47c47 100644
--- a/src/syntax/ident.rs
+++ b/src/syntax/ident.rs
@@ -1,5 +1,3 @@
-//! Unicode identifiers.
-
 use std::ops::Deref;
 
 use unicode_xid::UnicodeXID;
@@ -44,7 +42,7 @@ impl Deref for Ident {
     }
 }
 
-/// Whether the string is a valid identifier.
+/// Whether a string is a valid identifier.
 pub fn is_ident(string: &str) -> bool {
     let mut chars = string.chars();
     chars
@@ -52,12 +50,12 @@ pub fn is_ident(string: &str) -> bool {
         .map_or(false, |c| is_id_start(c) && chars.all(is_id_continue))
 }
 
-/// Whether the character can start an identifier.
+/// Whether a character can start an identifier.
 pub fn is_id_start(c: char) -> bool {
     c.is_xid_start() || c == '_'
 }
 
-/// Whether the character can continue an identifier.
+/// Whether a character can continue an identifier.
 pub fn is_id_continue(c: char) -> bool {
     c.is_xid_continue() || c == '_' || c == '-'
 }
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 970cd283..9c78fbc3 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -12,5 +12,5 @@ pub use node::*;
 pub use span::*;
 pub use token::*;
 
-/// A collection of nodes which form a tree together with the nodes' children.
-pub type SynTree = SpanVec<SynNode>;
+/// A collection of nodes which form a tree together with their children.
+pub type Tree = SpanVec<Node>;
diff --git a/src/syntax/node.rs b/src/syntax/node.rs
index cee810a2..d64d4fed 100644
--- a/src/syntax/node.rs
+++ b/src/syntax/node.rs
@@ -1,11 +1,8 @@
-//! Syntax tree nodes.
-
 use super::*;
 
-/// A syntax node, which encompasses a single logical entity of parsed source
-/// code.
+/// A syntax node, encompassing a single logical entity of parsed source code.
 #[derive(Debug, Clone, PartialEq)]
-pub enum SynNode {
+pub enum Node {
     /// Plain text.
     Text(String),
 
@@ -36,7 +33,7 @@ pub struct NodeHeading {
     /// The section depth (numer of hashtags minus 1).
     pub level: Spanned<u8>,
     /// The contents of the heading.
-    pub contents: SynTree,
+    pub contents: Tree,
 }
 
 /// A raw block with optional syntax highlighting: `` `raw` ``.
diff --git a/src/syntax/span.rs b/src/syntax/span.rs
index 20008354..3be770b8 100644
--- a/src/syntax/span.rs
+++ b/src/syntax/span.rs
@@ -1,5 +1,3 @@
-//! Mapping of values to the locations they originate from in source code.
-
 use std::fmt::{self, Debug, Display, Formatter};
 use std::ops::Range;
 
@@ -66,12 +64,18 @@ impl<T> Spanned<T> {
     }
 
     /// Map the value using a function while keeping the span.
-    pub fn map<U>(self, f: impl FnOnce(T) -> U) -> Spanned<U> {
+    pub fn map<F, U>(self, f: F) -> Spanned<U>
+    where
+        F: FnOnce(T) -> U,
+    {
         Spanned { v: f(self.v), span: self.span }
     }
 
     /// Maps the span while keeping the value.
-    pub fn map_span(mut self, f: impl FnOnce(Span) -> Span) -> Self {
+    pub fn map_span<F>(mut self, f: F) -> Self
+    where
+        F: FnOnce(Span) -> Span,
+    {
         self.span = f(self.span);
         self
     }
@@ -102,7 +106,7 @@ impl<T: Debug> Debug for Spanned<T> {
     }
 }
 
-/// Locates a slice of source code.
+/// Bounds of a slice of source code.
 #[derive(Copy, Clone, Ord, PartialOrd)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct Span {
diff --git a/src/syntax/token.rs b/src/syntax/token.rs
index b365d8d3..ef17fac2 100644
--- a/src/syntax/token.rs
+++ b/src/syntax/token.rs
@@ -1,5 +1,3 @@
-//! Token definition.
-
 use crate::geom::Unit;
 
 /// A minimal semantic entity of source code.
diff --git a/tests/typ/example-coma.typ b/tests/typ/example-coma.typ
index d559a6fb..5374af1f 100644
--- a/tests/typ/example-coma.typ
+++ b/tests/typ/example-coma.typ
@@ -1,4 +1,4 @@
-// Test integration of syntax, page setup, box layout and alignment.
+// Test integration of syntax, library and layouting.
 
 [page width: 450pt, height: 300pt, margins: 1cm]
 
diff --git a/tests/typeset.rs b/tests/typeset.rs
index 4f76d467..735a46c0 100644
--- a/tests/typeset.rs
+++ b/tests/typeset.rs
@@ -19,7 +19,7 @@ use typst::eval::State;
 use typst::export::pdf;
 use typst::font::FontLoader;
 use typst::geom::{Length, Point, Sides, Size};
-use typst::layout::{BoxLayout, ImageElement, LayoutElement};
+use typst::layout::{Element, Frame, Image};
 use typst::parse::{LineMap, Scanner};
 use typst::shaping::Shaped;
 use typst::syntax::{Location, Pos, SpanVec, Spanned, WithSpan};
@@ -134,16 +134,16 @@ fn test(
     state.page.margins = Sides::uniform(Some(Length::pt(10.0).into()));
 
     let Pass {
-        output: layouts,
+        output: frames,
         feedback: Feedback { mut diags, .. },
     } = typeset(&src, Rc::clone(env), state);
     diags.sort();
 
     let env = env.borrow();
-    let canvas = draw(&layouts, &env, 2.0);
+    let canvas = draw(&frames, &env, 2.0);
     canvas.pixmap.save_png(png_path).unwrap();
 
-    let pdf_data = pdf::export(&layouts, &env);
+    let pdf_data = pdf::export(&frames, &env);
     fs::write(pdf_path, pdf_data).unwrap();
 
     let mut ok = true;
@@ -226,12 +226,12 @@ fn print_diag(diag: &Spanned<Diag>, map: &LineMap) {
     println!("{}: {}-{}: {}", diag.v.level, start, end, diag.v.message);
 }
 
-fn draw(layouts: &[BoxLayout], env: &Env, pixel_per_pt: f32) -> Canvas {
+fn draw(frames: &[Frame], env: &Env, pixel_per_pt: f32) -> Canvas {
     let pad = Length::pt(5.0);
 
-    let height = pad + layouts.iter().map(|l| l.size.height + pad).sum::<Length>();
+    let height = pad + frames.iter().map(|l| l.size.height + pad).sum::<Length>();
     let width = 2.0 * pad
-        + layouts
+        + frames
             .iter()
             .map(|l| l.size.width)
             .max_by(|a, b| a.partial_cmp(&b).unwrap())
@@ -244,7 +244,7 @@ fn draw(layouts: &[BoxLayout], env: &Env, pixel_per_pt: f32) -> Canvas {
     canvas.pixmap.fill(Color::BLACK);
 
     let mut origin = Point::new(pad, pad);
-    for layout in layouts {
+    for frame in frames {
         let mut paint = Paint::default();
         paint.set_color(Color::WHITE);
 
@@ -252,26 +252,26 @@ fn draw(layouts: &[BoxLayout], env: &Env, pixel_per_pt: f32) -> Canvas {
             Rect::from_xywh(
                 origin.x.to_pt() as f32,
                 origin.y.to_pt() as f32,
-                layout.size.width.to_pt() as f32,
-                layout.size.height.to_pt() as f32,
+                frame.size.width.to_pt() as f32,
+                frame.size.height.to_pt() as f32,
             )
             .unwrap(),
             &paint,
         );
 
-        for &(pos, ref element) in &layout.elements {
+        for &(pos, ref element) in &frame.elements {
             let pos = origin + pos;
             match element {
-                LayoutElement::Text(shaped) => {
+                Element::Text(shaped) => {
                     draw_text(&mut canvas, pos, env, shaped);
                 }
-                LayoutElement::Image(image) => {
+                Element::Image(image) => {
                     draw_image(&mut canvas, pos, env, image);
                 }
             }
         }
 
-        origin.y += layout.size.height + pad;
+        origin.y += frame.size.height + pad;
     }
 
     canvas
@@ -303,7 +303,7 @@ fn draw_text(canvas: &mut Canvas, pos: Point, env: &Env, shaped: &Shaped) {
     }
 }
 
-fn draw_image(canvas: &mut Canvas, pos: Point, env: &Env, element: &ImageElement) {
+fn draw_image(canvas: &mut Canvas, pos: Point, env: &Env, element: &Image) {
     let img = &env.resources.loaded::<ImageResource>(element.res);
 
     let mut pixmap = Pixmap::new(img.buf.width(), img.buf.height()).unwrap();