6 files changed, 417 insertions, 400 deletions

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)
             }
         }