From 35610a8c6a1721010b933324dacfe2c4d58761a3 Mon Sep 17 00:00:00 2001
From: Laurenz <laurmaedje@gmail.com>
Date: Thu, 17 Feb 2022 17:25:57 +0100
Subject: Fallible layout

---
 src/eval/show.rs         |  8 ++++--
 src/eval/template.rs     | 36 ++++++++++++++---------
 src/layout/mod.rs        | 33 ++++++++++-----------
 src/lib.rs               |  4 +--
 src/library/align.rs     |  6 ++--
 src/library/columns.rs   |  6 ++--
 src/library/deco.rs      |  6 ++--
 src/library/flow.rs      | 21 +++++++++-----
 src/library/grid.rs      | 74 +++++++++++++++++++++++++++---------------------
 src/library/heading.rs   |  6 ++--
 src/library/hide.rs      |  6 ++--
 src/library/image.rs     |  4 +--
 src/library/link.rs      |  4 +--
 src/library/list.rs      |  6 ++--
 src/library/math.rs      |  4 +--
 src/library/pad.rs       |  6 ++--
 src/library/page.rs      |  8 +++---
 src/library/par.rs       | 12 ++++----
 src/library/place.rs     |  6 ++--
 src/library/raw.rs       |  4 +--
 src/library/shape.rs     |  8 +++---
 src/library/stack.rs     | 17 +++++++----
 src/library/table.rs     |  6 ++--
 src/library/text.rs      |  8 +++---
 src/library/transform.rs |  6 ++--
 25 files changed, 170 insertions(+), 135 deletions(-)

(limited to 'src')

diff --git a/src/eval/show.rs b/src/eval/show.rs
index 6157485d..a6a48e6f 100644
--- a/src/eval/show.rs
+++ b/src/eval/show.rs
@@ -4,12 +4,14 @@ use std::hash::{Hash, Hasher};
 use std::sync::Arc;
 
 use super::{StyleChain, Template};
+use crate::diag::TypResult;
 use crate::util::Prehashed;
+use crate::Vm;
 
 /// A node that can be realized given some styles.
 pub trait Show {
     /// Realize the template in the given styles.
-    fn show(&self, styles: StyleChain) -> Template;
+    fn show(&self, vm: &mut Vm, styles: StyleChain) -> TypResult<Template>;
 
     /// Convert to a packed show node.
     fn pack(self) -> ShowNode
@@ -40,8 +42,8 @@ impl ShowNode {
 }
 
 impl Show for ShowNode {
-    fn show(&self, styles: StyleChain) -> Template {
-        self.0.show(styles)
+    fn show(&self, vm: &mut Vm, styles: StyleChain) -> TypResult<Template> {
+        self.0.show(vm, styles)
     }
 
     fn pack(self) -> ShowNode {
diff --git a/src/eval/template.rs b/src/eval/template.rs
index 2cd6797a..b1fe07fe 100644
--- a/src/eval/template.rs
+++ b/src/eval/template.rs
@@ -165,20 +165,22 @@ impl Template {
     }
 
     /// Layout this template into a collection of pages.
-    pub fn layout(&self, vm: &mut Vm) -> Vec<Arc<Frame>> {
+    pub fn layout(&self, vm: &mut Vm) -> TypResult<Vec<Arc<Frame>>> {
         let style_arena = Arena::new();
         let template_arena = Arena::new();
 
         let mut builder = Builder::new(&style_arena, &template_arena, true);
         let chain = StyleChain::new(vm.styles);
-        builder.process(self, chain);
+        builder.process(self, vm, chain)?;
         builder.finish_page(true, false, chain);
 
+        let mut frames = vec![];
         let (pages, shared) = builder.pages.unwrap().finish();
-        pages
-            .iter()
-            .flat_map(|(page, map)| page.layout(vm, map.chain(&shared)))
-            .collect()
+        for (page, map) in pages.iter() {
+            frames.extend(page.layout(vm, map.chain(&shared))?);
+        }
+
+        Ok(frames)
     }
 }
 
@@ -269,12 +271,12 @@ impl Layout for Template {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let style_arena = Arena::new();
         let template_arena = Arena::new();
 
         let mut builder = Builder::new(&style_arena, &template_arena, false);
-        builder.process(self, styles);
+        builder.process(self, vm, styles)?;
         builder.finish_par(styles);
 
         let (flow, shared) = builder.flow.finish();
@@ -323,7 +325,12 @@ impl<'a> Builder<'a> {
     }
 
     /// Process a template.
-    fn process(&mut self, template: &'a Template, styles: StyleChain<'a>) {
+    fn process(
+        &mut self,
+        template: &'a Template,
+        vm: &mut Vm,
+        styles: StyleChain<'a>,
+    ) -> TypResult<()> {
         match template {
             Template::Space => {
                 self.par.weak(ParChild::Text(' '.into()), 0, styles);
@@ -382,8 +389,9 @@ impl<'a> Builder<'a> {
                 }
             }
             Template::Show(node) => {
-                let template = self.template_arena.alloc(node.show(styles));
-                self.process(template, styles.unscoped(node.id()));
+                let template = node.show(vm, styles)?;
+                let stored = self.template_arena.alloc(template);
+                self.process(stored, vm, styles.unscoped(node.id()))?;
             }
             Template::Styled(styled) => {
                 let (sub, map) = styled.as_ref();
@@ -397,7 +405,7 @@ impl<'a> Builder<'a> {
                     None => {}
                 }
 
-                self.process(sub, styles);
+                self.process(sub, vm, styles)?;
 
                 match interruption {
                     Some(Interruption::Page) => self.finish_page(true, false, styles),
@@ -407,10 +415,12 @@ impl<'a> Builder<'a> {
             }
             Template::Sequence(seq) => {
                 for sub in seq.iter() {
-                    self.process(sub, styles);
+                    self.process(sub, vm, styles)?;
                 }
             }
         }
+
+        Ok(())
     }
 
     /// Finish the currently built paragraph.
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index d47e37bb..0d1836fd 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -15,6 +15,7 @@ use std::fmt::{self, Debug, Formatter};
 use std::hash::{Hash, Hasher};
 use std::sync::Arc;
 
+use crate::diag::TypResult;
 use crate::eval::StyleChain;
 use crate::frame::{Element, Frame, Geometry, Shape, Stroke};
 use crate::geom::{Align, Linear, Paint, Point, Sides, Size, Spec, Transform};
@@ -33,7 +34,7 @@ pub trait Layout {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>>;
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>>;
 
     /// Convert to a packed node.
     fn pack(self) -> LayoutNode
@@ -137,7 +138,7 @@ impl Layout for LayoutNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let styles = styles.barred(self.id());
 
         #[cfg(not(feature = "layout-cache"))]
@@ -155,10 +156,10 @@ impl Layout for LayoutNode {
         // #[track_caller] annotation doesn't work.
         #[cfg(feature = "layout-cache")]
         if let Some(frames) = vm.layout_cache.get(hash, regions) {
-            frames
+            Ok(frames)
         } else {
             vm.level += 1;
-            let frames = self.0.layout(vm, regions, styles);
+            let frames = self.0.layout(vm, regions, styles)?;
             vm.level -= 1;
 
             let entry = FramesEntry::new(frames.clone(), vm.level);
@@ -175,7 +176,7 @@ impl Layout for LayoutNode {
             }
 
             vm.layout_cache.insert(hash, entry);
-            frames
+            Ok(frames)
         }
     }
 
@@ -248,11 +249,11 @@ impl Layout for EmptyNode {
         _: &mut Vm,
         regions: &Regions,
         _: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let size = regions.expand.select(regions.current, Size::zero());
         let mut cts = Constraints::new(regions.expand);
         cts.exact = regions.current.filter(regions.expand);
-        vec![Frame::new(size).constrain(cts)]
+        Ok(vec![Frame::new(size).constrain(cts)])
     }
 }
 
@@ -271,7 +272,7 @@ impl Layout for SizedNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let is_auto = self.sizing.map_is_none();
         let is_rel = self.sizing.map(|s| s.map_or(false, Linear::is_relative));
 
@@ -292,7 +293,7 @@ impl Layout for SizedNode {
             Regions::one(size, base, expand)
         };
 
-        let mut frames = self.child.layout(vm, &pod, styles);
+        let mut frames = self.child.layout(vm, &pod, styles)?;
         let Constrained { item: frame, cts } = &mut frames[0];
 
         // Ensure frame size matches regions size if expansion is on.
@@ -306,7 +307,7 @@ impl Layout for SizedNode {
         cts.exact = regions.current.filter(regions.expand | is_auto);
         cts.base = regions.base.filter(is_rel | is_auto);
 
-        frames
+        Ok(frames)
     }
 }
 
@@ -325,13 +326,13 @@ impl Layout for FillNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
-        let mut frames = self.child.layout(vm, regions, styles);
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
+        let mut frames = self.child.layout(vm, regions, styles)?;
         for Constrained { item: frame, .. } in &mut frames {
             let shape = Shape::filled(Geometry::Rect(frame.size), self.fill);
             Arc::make_mut(frame).prepend(Point::zero(), Element::Shape(shape));
         }
-        frames
+        Ok(frames)
     }
 }
 
@@ -350,12 +351,12 @@ impl Layout for StrokeNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
-        let mut frames = self.child.layout(vm, regions, styles);
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
+        let mut frames = self.child.layout(vm, regions, styles)?;
         for Constrained { item: frame, .. } in &mut frames {
             let shape = Shape::stroked(Geometry::Rect(frame.size), self.stroke);
             Arc::make_mut(frame).prepend(Point::zero(), Element::Shape(shape));
         }
-        frames
+        Ok(frames)
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index d4a8fba5..46bcad8d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -283,9 +283,7 @@ impl<'a> Vm<'a> {
     /// diagnostics in the form of a vector of error message with file and span
     /// information.
     pub fn typeset(&mut self, id: SourceId) -> TypResult<Vec<Arc<Frame>>> {
-        let module = self.evaluate(id)?;
-        let frames = module.template.layout(self);
-        Ok(frames)
+        self.evaluate(id)?.template.layout(self)
     }
 
     /// Resolve a user-entered path (relative to the source file) to be
diff --git a/src/library/align.rs b/src/library/align.rs
index 5b50937e..3ffd5ec8 100644
--- a/src/library/align.rs
+++ b/src/library/align.rs
@@ -27,7 +27,7 @@ impl Layout for AlignNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         // The child only needs to expand along an axis if there's no alignment.
         let mut pod = regions.clone();
         pod.expand &= self.aligns.map_is_none();
@@ -39,7 +39,7 @@ impl Layout for AlignNode {
         }
 
         // Layout the child.
-        let mut frames = self.child.layout(vm, &pod, passed.chain(&styles));
+        let mut frames = self.child.layout(vm, &pod, passed.chain(&styles))?;
 
         for ((current, base), Constrained { item: frame, cts }) in
             regions.iter().zip(&mut frames)
@@ -57,7 +57,7 @@ impl Layout for AlignNode {
             cts.exact = current.filter(regions.expand | cts.exact.map_is_some());
         }
 
-        frames
+        Ok(frames)
     }
 }
 
diff --git a/src/library/columns.rs b/src/library/columns.rs
index 61da6177..049fa8b9 100644
--- a/src/library/columns.rs
+++ b/src/library/columns.rs
@@ -32,7 +32,7 @@ impl Layout for ColumnsNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         // Separating the infinite space into infinite columns does not make
         // much sense.
         if regions.current.x.is_infinite() {
@@ -59,7 +59,7 @@ impl Layout for ColumnsNode {
         };
 
         // Layout the children.
-        let mut frames = self.child.layout(vm, &pod, styles).into_iter();
+        let mut frames = self.child.layout(vm, &pod, styles)?.into_iter();
 
         let dir = styles.get(ParNode::DIR);
         let total_regions = (frames.len() as f32 / columns as f32).ceil() as usize;
@@ -102,7 +102,7 @@ impl Layout for ColumnsNode {
             finished.push(output.constrain(cts));
         }
 
-        finished
+        Ok(finished)
     }
 }
 
diff --git a/src/library/deco.rs b/src/library/deco.rs
index 92fcf09f..79026288 100644
--- a/src/library/deco.rs
+++ b/src/library/deco.rs
@@ -32,15 +32,15 @@ impl<const L: DecoLine> DecoNode<L> {
 }
 
 impl<const L: DecoLine> Show for DecoNode<L> {
-    fn show(&self, styles: StyleChain) -> Template {
-        self.0.clone().styled(TextNode::LINES, vec![Decoration {
+    fn show(&self, _: &mut Vm, styles: StyleChain) -> TypResult<Template> {
+        Ok(self.0.clone().styled(TextNode::LINES, vec![Decoration {
             line: L,
             stroke: styles.get(Self::STROKE),
             thickness: styles.get(Self::THICKNESS),
             offset: styles.get(Self::OFFSET),
             extent: styles.get(Self::EXTENT),
             evade: styles.get(Self::EVADE),
-        }])
+        }]))
     }
 }
 
diff --git a/src/library/flow.rs b/src/library/flow.rs
index 95469b65..135fd327 100644
--- a/src/library/flow.rs
+++ b/src/library/flow.rs
@@ -31,7 +31,7 @@ impl Layout for FlowNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let mut layouter = FlowLayouter::new(regions);
 
         for (child, map) in self.0.iter() {
@@ -56,12 +56,12 @@ impl Layout for FlowNode {
                     layouter.layout_spacing(*kind);
                 }
                 FlowChild::Node(ref node) => {
-                    layouter.layout_node(vm, node, styles);
+                    layouter.layout_node(vm, node, styles)?;
                 }
             }
         }
 
-        layouter.finish()
+        Ok(layouter.finish())
     }
 }
 
@@ -161,7 +161,12 @@ impl FlowLayouter {
     }
 
     /// Layout a node.
-    pub fn layout_node(&mut self, vm: &mut Vm, node: &LayoutNode, styles: StyleChain) {
+    pub fn layout_node(
+        &mut self,
+        vm: &mut Vm,
+        node: &LayoutNode,
+        styles: StyleChain,
+    ) -> TypResult<()> {
         // Don't even try layouting into a full region.
         if self.regions.is_full() {
             self.finish_region();
@@ -171,9 +176,9 @@ impl FlowLayouter {
         // aligned later.
         if let Some(placed) = node.downcast::<PlaceNode>() {
             if placed.out_of_flow() {
-                let frame = node.layout(vm, &self.regions, styles).remove(0);
+                let frame = node.layout(vm, &self.regions, styles)?.remove(0);
                 self.items.push(FlowItem::Placed(frame.item));
-                return;
+                return Ok(());
             }
         }
 
@@ -188,7 +193,7 @@ impl FlowLayouter {
                 .unwrap_or(Align::Top),
         );
 
-        let frames = node.layout(vm, &self.regions, styles);
+        let frames = node.layout(vm, &self.regions, styles)?;
         let len = frames.len();
         for (i, frame) in frames.into_iter().enumerate() {
             // Grow our size, shrink the region and save the frame for later.
@@ -202,6 +207,8 @@ impl FlowLayouter {
                 self.finish_region();
             }
         }
+
+        Ok(())
     }
 
     /// Finish the frame for one region.
diff --git a/src/library/grid.rs b/src/library/grid.rs
index 78ac375f..5f1edb1c 100644
--- a/src/library/grid.rs
+++ b/src/library/grid.rs
@@ -38,7 +38,7 @@ impl Layout for GridNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         // Prepare grid layout by unifying content and gutter tracks.
         let layouter = GridLayouter::new(
             self.tracks.as_deref(),
@@ -48,7 +48,7 @@ impl Layout for GridNode {
             styles,
         );
 
-        // Measure the columsna nd layout the grid row-by-row.
+        // Measure the columns and layout the grid row-by-row.
         layouter.layout(vm)
     }
 }
@@ -205,19 +205,19 @@ impl<'a> GridLayouter<'a> {
     }
 
     /// Determines the columns sizes and then layouts the grid row-by-row.
-    pub fn layout(mut self, vm: &mut Vm) -> Vec<Constrained<Arc<Frame>>> {
-        self.measure_columns(vm);
+    pub fn layout(mut self, vm: &mut Vm) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
+        self.measure_columns(vm)?;
 
         for y in 0 .. self.rows.len() {
             // Skip to next region if current one is full, but only for content
             // rows, not for gutter rows.
             if y % 2 == 0 && self.regions.is_full() {
-                self.finish_region(vm);
+                self.finish_region(vm)?;
             }
 
             match self.rows[y] {
-                TrackSizing::Auto => self.layout_auto_row(vm, y),
-                TrackSizing::Linear(v) => self.layout_linear_row(vm, v, y),
+                TrackSizing::Auto => self.layout_auto_row(vm, y)?,
+                TrackSizing::Linear(v) => self.layout_linear_row(vm, v, y)?,
                 TrackSizing::Fractional(v) => {
                     self.cts.exact.y = Some(self.full);
                     self.lrows.push(Row::Fr(v, y));
@@ -226,12 +226,12 @@ impl<'a> GridLayouter<'a> {
             }
         }
 
-        self.finish_region(vm);
-        self.finished
+        self.finish_region(vm)?;
+        Ok(self.finished)
     }
 
     /// Determine all column sizes.
-    fn measure_columns(&mut self, vm: &mut Vm) {
+    fn measure_columns(&mut self, vm: &mut Vm) -> TypResult<()> {
         enum Case {
             /// The column sizing is only determined by specified linear sizes.
             PurelyLinear,
@@ -277,7 +277,7 @@ impl<'a> GridLayouter<'a> {
         let available = self.regions.current.x - linear;
         if available >= Length::zero() {
             // Determine size of auto columns.
-            let (auto, count) = self.measure_auto_columns(vm, available);
+            let (auto, count) = self.measure_auto_columns(vm, available)?;
 
             // If there is remaining space, distribute it to fractional columns,
             // otherwise shrink auto columns.
@@ -308,6 +308,8 @@ impl<'a> GridLayouter<'a> {
 
         // Sum up the resolved column sizes once here.
         self.used.x = self.rcols.iter().sum();
+
+        Ok(())
     }
 
     /// Measure the size that is available to auto columns.
@@ -315,7 +317,7 @@ impl<'a> GridLayouter<'a> {
         &mut self,
         vm: &mut Vm,
         available: Length,
-    ) -> (Length, usize) {
+    ) -> TypResult<(Length, usize)> {
         let mut auto = Length::zero();
         let mut count = 0;
 
@@ -340,7 +342,7 @@ impl<'a> GridLayouter<'a> {
                         pod.base.y = v.resolve(self.regions.base.y);
                     }
 
-                    let frame = node.layout(vm, &pod, self.styles).remove(0).item;
+                    let frame = node.layout(vm, &pod, self.styles)?.remove(0).item;
                     resolved.set_max(frame.size.x);
                 }
             }
@@ -350,7 +352,7 @@ impl<'a> GridLayouter<'a> {
             count += 1;
         }
 
-        (auto, count)
+        Ok((auto, count))
     }
 
     /// Distribute remaining space to fractional columns.
@@ -394,7 +396,7 @@ impl<'a> GridLayouter<'a> {
 
     /// Layout a row with automatic height. Such a row may break across multiple
     /// regions.
-    fn layout_auto_row(&mut self, vm: &mut Vm, y: usize) {
+    fn layout_auto_row(&mut self, vm: &mut Vm, y: usize) -> TypResult<()> {
         let mut resolved: Vec<Length> = vec![];
 
         // Determine the size for each region of the row.
@@ -409,7 +411,7 @@ impl<'a> GridLayouter<'a> {
                 }
 
                 let mut sizes = node
-                    .layout(vm, &pod, self.styles)
+                    .layout(vm, &pod, self.styles)?
                     .into_iter()
                     .map(|frame| frame.item.size.y);
 
@@ -427,14 +429,14 @@ impl<'a> GridLayouter<'a> {
 
         // Nothing to layout.
         if resolved.is_empty() {
-            return;
+            return Ok(());
         }
 
         // Layout into a single region.
         if let &[first] = resolved.as_slice() {
-            let frame = self.layout_single_row(vm, first, y);
+            let frame = self.layout_single_row(vm, first, y)?;
             self.push_row(frame);
-            return;
+            return Ok(());
         }
 
         // Expand all but the last region if the space is not
@@ -449,36 +451,40 @@ impl<'a> GridLayouter<'a> {
         }
 
         // Layout into multiple regions.
-        let frames = self.layout_multi_row(vm, &resolved, y);
+        let frames = self.layout_multi_row(vm, &resolved, y)?;
         let len = frames.len();
         for (i, frame) in frames.into_iter().enumerate() {
             self.push_row(frame);
             if i + 1 < len {
                 self.cts.exact.y = Some(self.full);
-                self.finish_region(vm);
+                self.finish_region(vm)?;
             }
         }
+
+        Ok(())
     }
 
     /// Layout a row with linear height. Such a row cannot break across multiple
     /// regions, but it may force a region break.
-    fn layout_linear_row(&mut self, vm: &mut Vm, v: Linear, y: usize) {
+    fn layout_linear_row(&mut self, vm: &mut Vm, v: Linear, y: usize) -> TypResult<()> {
         let resolved = v.resolve(self.regions.base.y);
-        let frame = self.layout_single_row(vm, resolved, y);
+        let frame = self.layout_single_row(vm, resolved, y)?;
 
         // Skip to fitting region.
         let height = frame.size.y;
         while !self.regions.current.y.fits(height) && !self.regions.in_last() {
             self.cts.max.y = Some(self.used.y + height);
-            self.finish_region(vm);
+            self.finish_region(vm)?;
 
             // Don't skip multiple regions for gutter and don't push a row.
             if y % 2 == 1 {
-                return;
+                return Ok(());
             }
         }
 
         self.push_row(frame);
+
+        Ok(())
     }
 
     /// Layout a row with fixed height and return its frame.
@@ -487,7 +493,7 @@ impl<'a> GridLayouter<'a> {
         vm: &mut Vm,
         height: Length,
         y: usize,
-    ) -> Frame {
+    ) -> TypResult<Frame> {
         let mut output = Frame::new(Size::new(self.used.x, height));
         let mut pos = Point::zero();
 
@@ -502,14 +508,14 @@ impl<'a> GridLayouter<'a> {
                     .select(self.regions.base, size);
 
                 let pod = Regions::one(size, base, Spec::splat(true));
-                let frame = node.layout(vm, &pod, self.styles).remove(0);
+                let frame = node.layout(vm, &pod, self.styles)?.remove(0);
                 output.push_frame(pos, frame.item);
             }
 
             pos.x += rcol;
         }
 
-        output
+        Ok(output)
     }
 
     /// Layout a row spanning multiple regions.
@@ -518,7 +524,7 @@ impl<'a> GridLayouter<'a> {
         vm: &mut Vm,
         heights: &[Length],
         y: usize,
-    ) -> Vec<Frame> {
+    ) -> TypResult<Vec<Frame>> {
         // Prepare frames.
         let mut outputs: Vec<_> = heights
             .iter()
@@ -542,7 +548,7 @@ impl<'a> GridLayouter<'a> {
                 }
 
                 // Push the layouted frames into the individual output frames.
-                let frames = node.layout(vm, &pod, self.styles);
+                let frames = node.layout(vm, &pod, self.styles)?;
                 for (output, frame) in outputs.iter_mut().zip(frames) {
                     output.push_frame(pos, frame.item);
                 }
@@ -551,7 +557,7 @@ impl<'a> GridLayouter<'a> {
             pos.x += rcol;
         }
 
-        outputs
+        Ok(outputs)
     }
 
     /// Push a row frame into the current region.
@@ -562,7 +568,7 @@ impl<'a> GridLayouter<'a> {
     }
 
     /// Finish rows for one region.
-    fn finish_region(&mut self, vm: &mut Vm) {
+    fn finish_region(&mut self, vm: &mut Vm) -> TypResult<()> {
         // Determine the size of the grid in this region, expanding fully if
         // there are fr rows.
         let mut size = self.used;
@@ -584,7 +590,7 @@ impl<'a> GridLayouter<'a> {
                 Row::Fr(v, y) => {
                     let remaining = self.full - self.used.y;
                     let height = v.resolve(self.fr, remaining);
-                    self.layout_single_row(vm, height, y)
+                    self.layout_single_row(vm, height, y)?
                 }
             };
 
@@ -600,6 +606,8 @@ impl<'a> GridLayouter<'a> {
         self.used.y = Length::zero();
         self.fr = Fractional::zero();
         self.cts = Constraints::new(self.expand);
+
+        Ok(())
     }
 
     /// Get the node in the cell in column `x` and row `y`.
diff --git a/src/library/heading.rs b/src/library/heading.rs
index 2123116b..2044355e 100644
--- a/src/library/heading.rs
+++ b/src/library/heading.rs
@@ -43,7 +43,7 @@ impl HeadingNode {
 }
 
 impl Show for HeadingNode {
-    fn show(&self, styles: StyleChain) -> Template {
+    fn show(&self, _: &mut Vm, styles: StyleChain) -> TypResult<Template> {
         let mut map = StyleMap::new();
 
         let upscale = (1.6 - 0.1 * self.level as f64).max(0.75);
@@ -93,6 +93,8 @@ impl Show for HeadingNode {
             seq.push(Template::Vertical(below.into()));
         }
 
-        Template::block(Template::sequence(seq).styled_with_map(map))
+        Ok(Template::block(
+            Template::sequence(seq).styled_with_map(map),
+        ))
     }
 }
diff --git a/src/library/hide.rs b/src/library/hide.rs
index 230300d2..ea2227f1 100644
--- a/src/library/hide.rs
+++ b/src/library/hide.rs
@@ -19,14 +19,14 @@ impl Layout for HideNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
-        let mut frames = self.0.layout(vm, regions, styles);
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
+        let mut frames = self.0.layout(vm, regions, styles)?;
 
         // Clear the frames.
         for Constrained { item: frame, .. } in &mut frames {
             *frame = Arc::new(Frame { elements: vec![], ..**frame });
         }
 
-        frames
+        Ok(frames)
     }
 }
diff --git a/src/library/image.rs b/src/library/image.rs
index 5527fbdc..05877126 100644
--- a/src/library/image.rs
+++ b/src/library/image.rs
@@ -39,7 +39,7 @@ impl Layout for ImageNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let img = vm.images.get(self.0);
         let pxw = img.width() as f64;
         let pxh = img.height() as f64;
@@ -91,7 +91,7 @@ impl Layout for ImageNode {
             frame.link(url);
         }
 
-        vec![frame.constrain(Constraints::tight(regions))]
+        Ok(vec![frame.constrain(Constraints::tight(regions))])
     }
 }
 
diff --git a/src/library/link.rs b/src/library/link.rs
index 58c7e550..95fff089 100644
--- a/src/library/link.rs
+++ b/src/library/link.rs
@@ -37,7 +37,7 @@ impl LinkNode {
 }
 
 impl Show for LinkNode {
-    fn show(&self, styles: StyleChain) -> Template {
+    fn show(&self, _: &mut Vm, styles: StyleChain) -> TypResult<Template> {
         let mut map = StyleMap::new();
         map.set(TextNode::LINK, Some(self.url.clone()));
 
@@ -50,6 +50,6 @@ impl Show for LinkNode {
             body = body.underlined();
         }
 
-        body.styled_with_map(map)
+        Ok(body.styled_with_map(map))
     }
 }
diff --git a/src/library/list.rs b/src/library/list.rs
index 7f76a178..08ccfc18 100644
--- a/src/library/list.rs
+++ b/src/library/list.rs
@@ -30,7 +30,7 @@ impl<const L: Labelling> ListNode<L> {
 }
 
 impl<const L: Labelling> Show for ListNode<L> {
-    fn show(&self, styles: StyleChain) -> Template {
+    fn show(&self, _: &mut Vm, styles: StyleChain) -> TypResult<Template> {
         let em = styles.get(TextNode::SIZE).abs;
         let label_indent = styles.get(Self::LABEL_INDENT).resolve(em);
         let body_indent = styles.get(Self::BODY_INDENT).resolve(em);
@@ -40,7 +40,7 @@ impl<const L: Labelling> Show for ListNode<L> {
             ORDERED | _ => format_eco!("{}.", self.number.unwrap_or(1)),
         };
 
-        Template::block(GridNode {
+        Ok(Template::block(GridNode {
             tracks: Spec::with_x(vec![
                 TrackSizing::Linear(label_indent.into()),
                 TrackSizing::Auto,
@@ -54,7 +54,7 @@ impl<const L: Labelling> Show for ListNode<L> {
                 LayoutNode::default(),
                 self.child.clone(),
             ],
-        })
+        }))
     }
 }
 
diff --git a/src/library/math.rs b/src/library/math.rs
index 29367cd5..d3c8b5e5 100644
--- a/src/library/math.rs
+++ b/src/library/math.rs
@@ -22,11 +22,11 @@ impl MathNode {
 }
 
 impl Show for MathNode {
-    fn show(&self, _: StyleChain) -> Template {
+    fn show(&self, _: &mut Vm, _: StyleChain) -> TypResult<Template> {
         let mut template = Template::Text(self.formula.trim().into());
         if self.display {
             template = Template::Block(template.pack());
         }
-        template.monospaced()
+        Ok(template.monospaced())
     }
 }
diff --git a/src/library/pad.rs b/src/library/pad.rs
index 84e83939..76647645 100644
--- a/src/library/pad.rs
+++ b/src/library/pad.rs
@@ -37,10 +37,10 @@ impl Layout for PadNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         // Layout child into padded regions.
         let pod = regions.map(|size| shrink(size, self.padding));
-        let mut frames = self.child.layout(vm, &pod, styles);
+        let mut frames = self.child.layout(vm, &pod, styles)?;
 
         for ((current, base), Constrained { item: frame, cts }) in
             regions.iter().zip(&mut frames)
@@ -70,7 +70,7 @@ impl Layout for PadNode {
             }
         }
 
-        frames
+        Ok(frames)
     }
 }
 
diff --git a/src/library/page.rs b/src/library/page.rs
index 155f60dd..160ac1ed 100644
--- a/src/library/page.rs
+++ b/src/library/page.rs
@@ -60,7 +60,7 @@ impl PageNode {
 
 impl PageNode {
     /// Layout the page run into a sequence of frames, one per page.
-    pub fn layout(&self, vm: &mut Vm, styles: StyleChain) -> Vec<Arc<Frame>> {
+    pub fn layout(&self, vm: &mut Vm, styles: StyleChain) -> TypResult<Vec<Arc<Frame>>> {
         // When one of the lengths is infinite the page fits its content along
         // that axis.
         let width = styles.get(Self::WIDTH).unwrap_or(Length::inf());
@@ -103,11 +103,11 @@ impl PageNode {
         // Layout the child.
         let expand = size.map(Length::is_finite);
         let regions = Regions::repeat(size, size, expand);
-        child
-            .layout(vm, &regions, styles)
+        Ok(child
+            .layout(vm, &regions, styles)?
             .into_iter()
             .map(|c| c.item)
-            .collect()
+            .collect())
     }
 }
 
diff --git a/src/library/par.rs b/src/library/par.rs
index 02633612..dd0ee5d0 100644
--- a/src/library/par.rs
+++ b/src/library/par.rs
@@ -85,7 +85,7 @@ impl Layout for ParNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         // Collect all text into one string used for BiDi analysis.
         let text = self.collect_text();
 
@@ -95,10 +95,10 @@ impl Layout for ParNode {
 
         // Prepare paragraph layout by building a representation on which we can
         // do line breaking without layouting each and every line from scratch.
-        let layouter = ParLayouter::new(self, vm, regions, &styles, bidi);
+        let layouter = ParLayouter::new(self, vm, regions, &styles, bidi)?;
 
         // Find suitable linebreaks.
-        layouter.layout(vm, regions.clone())
+        Ok(layouter.layout(vm, regions.clone()))
     }
 }
 
@@ -220,7 +220,7 @@ impl<'a> ParLayouter<'a> {
         regions: &Regions,
         styles: &'a StyleChain<'a>,
         bidi: BidiInfo<'a>,
-    ) -> Self {
+    ) -> TypResult<Self> {
         let mut items = vec![];
         let mut ranges = vec![];
 
@@ -255,7 +255,7 @@ impl<'a> ParLayouter<'a> {
                 ParChild::Node(node) => {
                     let size = Size::new(regions.current.x, regions.base.y);
                     let pod = Regions::one(size, regions.base, Spec::splat(false));
-                    let frame = node.layout(vm, &pod, styles).remove(0);
+                    let frame = node.layout(vm, &pod, styles)?.remove(0);
                     items.push(ParItem::Frame(Arc::take(frame.item)));
                     ranges.push(range);
                 }
@@ -266,7 +266,7 @@ impl<'a> ParLayouter<'a> {
         let align = styles.get(ParNode::ALIGN);
         let leading = styles.get(ParNode::LEADING).resolve(em);
 
-        Self { align, leading, bidi, items, ranges }
+        Ok(Self { align, leading, bidi, items, ranges })
     }
 
     /// Find first-fit line breaks and build the paragraph.
diff --git a/src/library/place.rs b/src/library/place.rs
index c2c9ac25..9bcd3c37 100644
--- a/src/library/place.rs
+++ b/src/library/place.rs
@@ -26,7 +26,7 @@ impl Layout for PlaceNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let out_of_flow = self.out_of_flow();
 
         // The pod is the base area of the region because for absolute
@@ -37,7 +37,7 @@ impl Layout for PlaceNode {
             Regions::one(regions.base, regions.base, expand)
         };
 
-        let mut frames = self.0.layout(vm, &pod, styles);
+        let mut frames = self.0.layout(vm, &pod, styles)?;
         let Constrained { item: frame, cts } = &mut frames[0];
 
         // If expansion is off, zero all sizes so that we don't take up any
@@ -51,7 +51,7 @@ impl Layout for PlaceNode {
         cts.base = regions.base.map(Some);
         cts.exact = regions.current.filter(regions.expand | out_of_flow);
 
-        frames
+        Ok(frames)
     }
 }
 
diff --git a/src/library/raw.rs b/src/library/raw.rs
index 45733fd0..da926679 100644
--- a/src/library/raw.rs
+++ b/src/library/raw.rs
@@ -40,7 +40,7 @@ impl RawNode {
 }
 
 impl Show for RawNode {
-    fn show(&self, styles: StyleChain) -> Template {
+    fn show(&self, _: &mut Vm, styles: StyleChain) -> TypResult<Template> {
         let lang = styles.get_ref(Self::LANG).as_ref();
         let foreground = THEME
             .settings
@@ -87,7 +87,7 @@ impl Show for RawNode {
             template = Template::Block(template.pack());
         }
 
-        template.monospaced()
+        Ok(template.monospaced())
     }
 }
 
diff --git a/src/library/shape.rs b/src/library/shape.rs
index acb011ea..518254ce 100644
--- a/src/library/shape.rs
+++ b/src/library/shape.rs
@@ -49,7 +49,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let mut frames;
         if let Some(child) = &self.0 {
             let mut padding = styles.get(Self::PADDING);
@@ -61,7 +61,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
             let child = child.clone().padded(Sides::splat(padding));
 
             let mut pod = Regions::one(regions.current, regions.base, regions.expand);
-            frames = child.layout(vm, &pod, styles);
+            frames = child.layout(vm, &pod, styles)?;
 
             // Relayout with full expansion into square region to make sure
             // the result is really a square or circle.
@@ -77,7 +77,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
 
                 pod.current = Size::splat(length);
                 pod.expand = Spec::splat(true);
-                frames = child.layout(vm, &pod, styles);
+                frames = child.layout(vm, &pod, styles)?;
                 frames[0].cts = Constraints::tight(regions);
             }
         } else {
@@ -127,7 +127,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
             frame.link(url);
         }
 
-        frames
+        Ok(frames)
     }
 }
 
diff --git a/src/library/stack.rs b/src/library/stack.rs
index 287731b8..c7985d87 100644
--- a/src/library/stack.rs
+++ b/src/library/stack.rs
@@ -31,7 +31,7 @@ impl Layout for StackNode {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let mut layouter = StackLayouter::new(self.dir, regions);
 
         // Spacing to insert before the next node.
@@ -48,13 +48,13 @@ impl Layout for StackNode {
                         layouter.layout_spacing(kind);
                     }
 
-                    layouter.layout_node(vm, node, styles);
+                    layouter.layout_node(vm, node, styles)?;
                     deferred = self.spacing;
                 }
             }
         }
 
-        layouter.finish()
+        Ok(layouter.finish())
     }
 }
 
@@ -163,7 +163,12 @@ impl StackLayouter {
     }
 
     /// Layout an arbitrary node.
-    pub fn layout_node(&mut self, vm: &mut Vm, node: &LayoutNode, styles: StyleChain) {
+    pub fn layout_node(
+        &mut self,
+        vm: &mut Vm,
+        node: &LayoutNode,
+        styles: StyleChain,
+    ) -> TypResult<()> {
         if self.regions.is_full() {
             self.finish_region();
         }
@@ -174,7 +179,7 @@ impl StackLayouter {
             .and_then(|node| node.aligns.get(self.axis))
             .unwrap_or(self.dir.start().into());
 
-        let frames = node.layout(vm, &self.regions, styles);
+        let frames = node.layout(vm, &self.regions, styles)?;
         let len = frames.len();
         for (i, frame) in frames.into_iter().enumerate() {
             // Grow our size, shrink the region and save the frame for later.
@@ -188,6 +193,8 @@ impl StackLayouter {
                 self.finish_region();
             }
         }
+
+        Ok(())
     }
 
     /// Advance to the next region.
diff --git a/src/library/table.rs b/src/library/table.rs
index dfefa21d..8c088c09 100644
--- a/src/library/table.rs
+++ b/src/library/table.rs
@@ -55,7 +55,7 @@ impl TableNode {
 }
 
 impl Show for TableNode {
-    fn show(&self, styles: StyleChain) -> Template {
+    fn show(&self, _: &mut Vm, styles: StyleChain) -> TypResult<Template> {
         let primary = styles.get(Self::PRIMARY);
         let secondary = styles.get(Self::SECONDARY);
         let thickness = styles.get(Self::THICKNESS);
@@ -85,10 +85,10 @@ impl Show for TableNode {
             })
             .collect();
 
-        Template::block(GridNode {
+        Ok(Template::block(GridNode {
             tracks: self.tracks.clone(),
             gutter: self.gutter.clone(),
             children,
-        })
+        }))
     }
 }
diff --git a/src/library/text.rs b/src/library/text.rs
index 9fbc8605..721a8eac 100644
--- a/src/library/text.rs
+++ b/src/library/text.rs
@@ -123,8 +123,8 @@ impl StrongNode {
 }
 
 impl Show for StrongNode {
-    fn show(&self, _: StyleChain) -> Template {
-        self.0.clone().styled(TextNode::STRONG, true)
+    fn show(&self, _: &mut Vm, _: StyleChain) -> TypResult<Template> {
+        Ok(self.0.clone().styled(TextNode::STRONG, true))
     }
 }
 
@@ -140,8 +140,8 @@ impl EmphNode {
 }
 
 impl Show for EmphNode {
-    fn show(&self, _: StyleChain) -> Template {
-        self.0.clone().styled(TextNode::EMPH, true)
+    fn show(&self, _: &mut Vm, _: StyleChain) -> TypResult<Template> {
+        Ok(self.0.clone().styled(TextNode::EMPH, true))
     }
 }
 
diff --git a/src/library/transform.rs b/src/library/transform.rs
index 91d4b574..5cdb2f6f 100644
--- a/src/library/transform.rs
+++ b/src/library/transform.rs
@@ -49,9 +49,9 @@ impl<const T: TransformKind> Layout for TransformNode<T> {
         vm: &mut Vm,
         regions: &Regions,
         styles: StyleChain,
-    ) -> Vec<Constrained<Arc<Frame>>> {
+    ) -> TypResult<Vec<Constrained<Arc<Frame>>>> {
         let origin = styles.get(Self::ORIGIN).unwrap_or(Align::CENTER_HORIZON);
-        let mut frames = self.child.layout(vm, regions, styles);
+        let mut frames = self.child.layout(vm, regions, styles)?;
 
         for Constrained { item: frame, .. } in &mut frames {
             let Spec { x, y } = origin.zip(frame.size).map(|(o, s)| o.resolve(s));
@@ -62,7 +62,7 @@ impl<const T: TransformKind> Layout for TransformNode<T> {
             Arc::make_mut(frame).transform(transform);
         }
 
-        frames
+        Ok(frames)
     }
 }
 
-- 
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