Remove props in favor of using state for everything

16 files changed, 197 insertions, 267 deletions

diff --git a/src/exec/context.rs b/src/exec/context.rs
index 63008260..e03a7c67 100644
--- a/src/exec/context.rs
+++ b/src/exec/context.rs
@@ -1,4 +1,5 @@
 use std::mem;
+use std::rc::Rc;
 
 use super::{Exec, ExecWithMap, FontFamily, State};
 use crate::diag::{Diag, DiagSet, Pass};
@@ -43,8 +44,11 @@ impl ExecContext {
 
     /// Set the font to monospace.
     pub fn set_monospace(&mut self) {
-        let families = self.state.font.families_mut();
-        families.list.insert(0, FontFamily::Monospace);
+        self.state
+            .font_mut()
+            .families_mut()
+            .list
+            .insert(0, FontFamily::Monospace);
     }
 
     /// Execute a template and return the result as a stack node.
@@ -108,8 +112,7 @@ impl ExecContext {
 
     /// Apply a forced paragraph break.
     pub fn parbreak(&mut self) {
-        let em = self.state.font.resolve_size();
-        let amount = self.state.par.spacing.resolve(em);
+        let amount = self.state.par.spacing.resolve(self.state.font.size);
         self.stack.parbreak(&self.state);
         self.stack.push_soft(StackChild::Spacing(amount));
     }
@@ -133,9 +136,11 @@ impl ExecContext {
     }
 
     fn make_text_node(&self, text: impl Into<String>) -> ParChild {
-        let align = self.state.aligns.cross;
-        let props = self.state.font.resolve_props();
-        ParChild::Text(text.into(), props, align)
+        ParChild::Text(
+            text.into(),
+            self.state.aligns.cross,
+            Rc::clone(&self.state.font),
+        )
     }
 }
 
@@ -217,11 +222,10 @@ struct ParBuilder {
 
 impl ParBuilder {
     fn new(state: &State) -> Self {
-        let em = state.font.resolve_size();
         Self {
             aligns: state.aligns,
             dir: state.lang.dir,
-            line_spacing: state.par.leading.resolve(em),
+            line_spacing: state.par.leading.resolve(state.font.size),
             children: vec![],
             last: Last::None,
         }
diff --git a/src/exec/mod.rs b/src/exec/mod.rs
index a13d8c5e..639c1a87 100644
--- a/src/exec/mod.rs
+++ b/src/exec/mod.rs
@@ -55,8 +55,8 @@ impl ExecWithMap for syntax::Node {
             Self::Space => ctx.push_word_space(),
             Self::Linebreak(_) => ctx.linebreak(),
             Self::Parbreak(_) => ctx.parbreak(),
-            Self::Strong(_) => ctx.state.font.strong ^= true,
-            Self::Emph(_) => ctx.state.font.emph ^= true,
+            Self::Strong(_) => ctx.state.font_mut().strong ^= true,
+            Self::Emph(_) => ctx.state.font_mut().emph ^= true,
             Self::Raw(raw) => raw.exec(ctx),
             Self::Heading(heading) => heading.exec_with_map(ctx, map),
             Self::List(list) => list.exec_with_map(ctx, map),
@@ -85,10 +85,11 @@ impl Exec for syntax::RawNode {
 impl ExecWithMap for syntax::HeadingNode {
     fn exec_with_map(&self, ctx: &mut ExecContext, map: &ExprMap) {
         let snapshot = ctx.state.clone();
+        let font = ctx.state.font_mut();
 
         let upscale = 1.6 - 0.1 * self.level as f64;
-        ctx.state.font.scale *= upscale;
-        ctx.state.font.strong = true;
+        font.size *= upscale;
+        font.strong = true;
 
         self.body.exec_with_map(ctx, map);
 
@@ -109,7 +110,7 @@ impl ExecWithMap for syntax::ListNode {
             aspect: None,
             children: vec![
                 StackChild::Any(bullet.into(), Gen::default()),
-                StackChild::Spacing(ctx.state.font.resolve_size() / 2.0),
+                StackChild::Spacing(ctx.state.font.size / 2.0),
                 StackChild::Any(body.into(), Gen::default()),
             ],
         };
@@ -139,7 +140,7 @@ impl Exec for Value {
                 let prev = Rc::clone(&ctx.state.font.families);
                 ctx.set_monospace();
                 ctx.push_text(pretty(other));
-                ctx.state.font.families = prev;
+                ctx.state.font_mut().families = prev;
             }
         }
     }
diff --git a/src/exec/state.rs b/src/exec/state.rs
index 2b824afe..fa16004e 100644
--- a/src/exec/state.rs
+++ b/src/exec/state.rs
@@ -8,7 +8,7 @@ use crate::layout::Fill;
 use crate::paper::{Paper, PaperClass, PAPER_A4};
 
 /// The execution state.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Default, Debug, Clone, PartialEq, Hash)]
 pub struct State {
     /// The current language-related settings.
     pub lang: LangState,
@@ -17,25 +17,20 @@ pub struct State {
     /// The current paragraph settings.
     pub par: ParState,
     /// The current font settings.
-    pub font: FontState,
+    pub font: Rc<FontState>,
     /// The current alignments of layouts in their parents.
     pub aligns: Gen<Align>,
 }
 
-impl Default for State {
-    fn default() -> Self {
-        Self {
-            lang: LangState::default(),
-            page: PageState::default(),
-            par: ParState::default(),
-            font: FontState::default(),
-            aligns: Gen::splat(Align::Start),
-        }
+impl State {
+    /// Access the `font` state mutably.
+    pub fn font_mut(&mut self) -> &mut FontState {
+        Rc::make_mut(&mut self.font)
     }
 }
 
 /// Defines language properties.
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, Hash)]
 pub struct LangState {
     /// The direction for text and other inline objects.
     pub dir: Dir,
@@ -48,7 +43,7 @@ impl Default for LangState {
 }
 
 /// Defines page properties.
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, Hash)]
 pub struct PageState {
     /// The class of this page.
     pub class: PaperClass,
@@ -88,7 +83,7 @@ impl Default for PageState {
 }
 
 /// Defines paragraph properties.
-#[derive(Debug, Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq, Hash)]
 pub struct ParState {
     /// The spacing between paragraphs (dependent on scaled font size).
     pub spacing: Linear,
@@ -110,7 +105,7 @@ impl Default for ParState {
 }
 
 /// Defines font properties.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Hash)]
 pub struct FontState {
     /// A list of font families with generic class definitions.
     pub families: Rc<FamilyList>,
@@ -118,8 +113,6 @@ pub struct FontState {
     pub variant: FontVariant,
     /// The font size.
     pub size: Length,
-    /// The linear to apply on the base font size.
-    pub scale: Linear,
     /// The top end of the text bounding box.
     pub top_edge: VerticalFontMetric,
     /// The bottom end of the text bounding box.
@@ -133,49 +126,14 @@ pub struct FontState {
     /// whether the next `_` makes italic or non-italic.
     pub emph: bool,
     /// The specifications for a strikethrough line, if any.
-    pub strikethrough: Option<LineState>,
+    pub strikethrough: Option<Rc<LineState>>,
     /// The specifications for a underline, if any.
-    pub underline: Option<LineState>,
+    pub underline: Option<Rc<LineState>>,
     /// The specifications for a overline line, if any.
-    pub overline: Option<LineState>,
+    pub overline: Option<Rc<LineState>>,
 }
 
 impl FontState {
-    /// The resolved font size.
-    pub fn resolve_size(&self) -> Length {
-        self.scale.resolve(self.size)
-    }
-
-    /// Resolve font properties.
-    pub fn resolve_props(&self) -> FontProps {
-        let mut variant = self.variant;
-
-        if self.strong {
-            variant.weight = variant.weight.thicken(300);
-        }
-
-        if self.emph {
-            variant.style = match variant.style {
-                FontStyle::Normal => FontStyle::Italic,
-                FontStyle::Italic => FontStyle::Normal,
-                FontStyle::Oblique => FontStyle::Normal,
-            }
-        }
-
-        let size = self.resolve_size();
-        FontProps {
-            families: Rc::clone(&self.families),
-            variant,
-            size,
-            top_edge: self.top_edge,
-            bottom_edge: self.bottom_edge,
-            strikethrough: self.strikethrough.map(|s| s.resolve_props(size, &self.fill)),
-            underline: self.underline.map(|s| s.resolve_props(size, &self.fill)),
-            overline: self.overline.map(|s| s.resolve_props(size, &self.fill)),
-            fill: self.fill,
-        }
-    }
-
     /// Access the `families` mutably.
     pub fn families_mut(&mut self) -> &mut FamilyList {
         Rc::make_mut(&mut self.families)
@@ -194,7 +152,6 @@ impl Default for FontState {
             size: Length::pt(11.0),
             top_edge: VerticalFontMetric::CapHeight,
             bottom_edge: VerticalFontMetric::Baseline,
-            scale: Linear::one(),
             fill: Fill::Color(Color::Rgba(RgbaColor::BLACK)),
             strong: false,
             emph: false,
@@ -205,11 +162,9 @@ impl Default for FontState {
     }
 }
 
-/// Describes a line that could be positioned over or under text.
+/// Describes a line that could be positioned over, under or on top of text.
 #[derive(Debug, Copy, Clone, PartialEq, Hash)]
 pub struct LineState {
-    /// Color of the line. Will default to text color if `None`.
-    pub fill: Option<Fill>,
     /// Thickness of the line's stroke. Calling functions should attempt to
     /// read this value from the appropriate font tables if this is `None`.
     pub strength: Option<Linear>,
@@ -219,40 +174,8 @@ pub struct LineState {
     pub position: Option<Linear>,
     /// Amount that the line will be longer or shorter than its associated text.
     pub extent: Linear,
-}
-
-impl LineState {
-    pub fn resolve_props(&self, font_size: Length, fill: &Fill) -> LineProps {
-        LineProps {
-            fill: self.fill.unwrap_or_else(|| fill.clone()),
-            strength: self.strength.map(|s| s.resolve(font_size)),
-            position: self.position.map(|p| p.resolve(font_size)),
-            extent: self.extent.resolve(font_size),
-        }
-    }
-}
-
-/// Properties used for font selection and layout.
-#[derive(Debug, Clone, PartialEq, Hash)]
-pub struct FontProps {
-    /// The list of font families to use for shaping.
-    pub families: Rc<FamilyList>,
-    /// Which variant of the font to use.
-    pub variant: FontVariant,
-    /// The font size.
-    pub size: Length,
-    /// What line to consider the top edge of text.
-    pub top_edge: VerticalFontMetric,
-    /// What line to consider the bottom edge of text.
-    pub bottom_edge: VerticalFontMetric,
-    /// The fill color of the text.
-    pub fill: Fill,
-    /// The specifications for a strikethrough line, if any.
-    pub strikethrough: Option<LineProps>,
-    /// The specifications for a underline, if any.
-    pub underline: Option<LineProps>,
-    /// The specifications for a overline line, if any.
-    pub overline: Option<LineProps>,
+    /// Color of the line. Will default to text color if `None`.
+    pub fill: Option<Fill>,
 }
 
 /// Font family definitions.
@@ -319,19 +242,3 @@ impl Display for FontFamily {
         })
     }
 }
-
-/// Describes a line that could be positioned over or under text.
-#[derive(Debug, Copy, Clone, PartialEq, Hash)]
-pub struct LineProps {
-    /// Color of the line.
-    pub fill: Fill,
-    /// Thickness of the line's stroke. Calling functions should attempt to
-    /// read this value from the appropriate font tables if this is `None`.
-    pub strength: Option<Length>,
-    /// Position of the line relative to the baseline. Calling functions should
-    /// attempt to read this value from the appropriate font tables if this is
-    /// `None`.
-    pub position: Option<Length>,
-    /// Amount that the line will be longer or shorter than its associated text.
-    pub extent: Length,
-}
diff --git a/src/export/pdf.rs b/src/export/pdf.rs
index da3c9369..f939d8ab 100644
--- a/src/export/pdf.rs
+++ b/src/export/pdf.rs
@@ -14,7 +14,7 @@ use ttf_parser::{name_id, GlyphId};
 
 use crate::cache::Cache;
 use crate::color::Color;
-use crate::font::{Em, FaceId, VerticalFontMetric};
+use crate::font::{Em, FaceId};
 use crate::geom::{self, Length, Size};
 use crate::image::{Image, ImageId};
 use crate::layout::{Element, Fill, Frame, Shape};
@@ -256,9 +256,9 @@ impl<'a> PdfExporter<'a> {
             );
 
             let italic_angle = ttf.italic_angle().unwrap_or(0.0);
-            let ascender = face.vertical_metric(VerticalFontMetric::Ascender).to_pdf();
-            let descender = face.vertical_metric(VerticalFontMetric::Descender).to_pdf();
-            let cap_height = face.vertical_metric(VerticalFontMetric::CapHeight).to_pdf();
+            let ascender = face.ascender.to_pdf();
+            let descender = face.descender.to_pdf();
+            let cap_height = face.cap_height.to_pdf();
             let stem_v = 10.0 + 0.244 * (f32::from(ttf.weight().to_number()) - 50.0);
 
             // Write the base font object referencing the CID font.
diff --git a/src/font.rs b/src/font.rs
index a55a2a13..fc7a99d9 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -15,10 +15,19 @@ pub struct Face {
     index: u32,
     ttf: rustybuzz::Face<'static>,
     units_per_em: f64,
-    ascender: Em,
-    cap_height: Em,
-    x_height: Em,
-    descender: Em,
+    pub ascender: Em,
+    pub cap_height: Em,
+    pub x_height: Em,
+    pub descender: Em,
+    pub strikethrough: LineMetrics,
+    pub underline: LineMetrics,
+    pub overline: LineMetrics,
+}
+
+/// Metrics for a decorative line.
+pub struct LineMetrics {
+    pub strength: Em,
+    pub position: Em,
 }
 
 impl Face {
@@ -35,22 +44,45 @@ impl Face {
 
         let ttf = rustybuzz::Face::from_slice(slice, index)?;
 
-        // Look up some metrics we may need often.
         let units_per_em = f64::from(ttf.units_per_em());
-        let ascender = ttf.typographic_ascender().unwrap_or(ttf.ascender());
-        let cap_height = ttf.capital_height().filter(|&h| h > 0).unwrap_or(ascender);
-        let x_height = ttf.x_height().filter(|&h| h > 0).unwrap_or(ascender);
-        let descender = ttf.typographic_descender().unwrap_or(ttf.descender());
+        let to_em = |units| Em::from_units(units, units_per_em);
+
+        let ascender = to_em(ttf.typographic_ascender().unwrap_or(ttf.ascender()));
+        let cap_height = ttf.capital_height().filter(|&h| h > 0).map_or(ascender, to_em);
+        let x_height = ttf.x_height().filter(|&h| h > 0).map_or(ascender, to_em);
+        let descender = to_em(ttf.typographic_descender().unwrap_or(ttf.descender()));
+
+        let strikeout = ttf.strikeout_metrics();
+        let underline = ttf.underline_metrics();
+        let default = Em::new(0.06);
+
+        let strikethrough = LineMetrics {
+            strength: strikeout.or(underline).map_or(default, |s| to_em(s.thickness)),
+            position: strikeout.map_or(Em::new(0.25), |s| to_em(s.position)),
+        };
+
+        let underline = LineMetrics {
+            strength: underline.or(strikeout).map_or(default, |s| to_em(s.thickness)),
+            position: underline.map_or(Em::new(-0.2), |s| to_em(s.position)),
+        };
+
+        let overline = LineMetrics {
+            strength: underline.strength,
+            position: cap_height + Em::new(0.1),
+        };
 
         Some(Self {
             buffer,
             index,
             ttf,
             units_per_em,
-            ascender: Em::from_units(ascender, units_per_em),
-            cap_height: Em::from_units(cap_height, units_per_em),
-            x_height: Em::from_units(x_height, units_per_em),
-            descender: Em::from_units(descender, units_per_em),
+            ascender,
+            cap_height,
+            x_height,
+            descender,
+            strikethrough,
+            underline,
+            overline,
         })
     }
 
diff --git a/src/geom/angle.rs b/src/geom/angle.rs
index f1db841c..bf8bcc66 100644
--- a/src/geom/angle.rs
+++ b/src/geom/angle.rs
@@ -1,15 +1,18 @@
 use super::*;
+use decorum::N64;
 
 /// An angle.
-#[derive(Default, Copy, Clone, PartialEq, PartialOrd)]
+#[derive(Default, Copy, Clone, PartialEq, PartialOrd, Hash)]
 pub struct Angle {
     /// The angle in raw units.
-    raw: f64,
+    raw: N64,
 }
 
 impl Angle {
     /// The zero angle.
-    pub const ZERO: Self = Self { raw: 0.0 };
+    pub fn zero() -> Self {
+        Self { raw: N64::from(0.0) }
+    }
 
     /// Create an angle from a number of radians.
     pub fn rad(rad: f64) -> Self {
@@ -23,7 +26,7 @@ impl Angle {
 
     /// Create an angle from a number of raw units.
     pub fn raw(raw: f64) -> Self {
-        Self { raw }
+        Self { raw: N64::from(raw) }
     }
 
     /// Convert this to a number of radians.
@@ -38,17 +41,17 @@ impl Angle {
 
     /// Get the value of this angle in raw units.
     pub fn to_raw(self) -> f64 {
-        self.raw
+        self.raw.into()
     }
 
     /// Create an angle from a value in a unit.
     pub fn with_unit(val: f64, unit: AngularUnit) -> Self {
-        Self { raw: val * unit.raw_scale() }
+        Self { raw: N64::from(val * unit.raw_scale()) }
     }
 
     /// Get the value of this length in unit.
     pub fn to_unit(self, unit: AngularUnit) -> f64 {
-        self.raw / unit.raw_scale()
+        self.to_raw() / unit.raw_scale()
     }
 }
 
@@ -119,7 +122,7 @@ impl Div for Angle {
     type Output = f64;
 
     fn div(self, other: Self) -> f64 {
-        self.raw / other.raw
+        self.to_raw() / other.to_raw()
     }
 }
 
@@ -130,7 +133,7 @@ assign_impl!(Angle /= f64);
 
 impl Sum for Angle {
     fn sum<I: Iterator<Item = Angle>>(iter: I) -> Self {
-        iter.fold(Angle::ZERO, Add::add)
+        iter.fold(Angle::zero(), Add::add)
     }
 }
 /// Different units of angular measurement.
diff --git a/src/geom/point.rs b/src/geom/point.rs
index 8982dcea..129205f1 100644
--- a/src/geom/point.rs
+++ b/src/geom/point.rs
@@ -3,7 +3,7 @@ use super::*;
 use serde::{Deserialize, Serialize};
 
 /// A point in 2D.
-#[derive(Default, Copy, Clone, PartialEq, Serialize, Deserialize)]
+#[derive(Default, Copy, Clone, PartialEq, Serialize, Deserialize, Hash)]
 pub struct Point {
     /// The x coordinate.
     pub x: Length,
diff --git a/src/geom/size.rs b/src/geom/size.rs
index b859cb80..ea522091 100644
--- a/src/geom/size.rs
+++ b/src/geom/size.rs
@@ -3,7 +3,7 @@ use super::*;
 use serde::{Deserialize, Serialize};
 
 /// A size in 2D.
-#[derive(Default, Copy, Clone, PartialEq, Serialize, Deserialize)]
+#[derive(Default, Copy, Clone, PartialEq, Serialize, Deserialize, Hash)]
 pub struct Size {
     /// The width.
     pub width: Length,
diff --git a/src/geom/spec.rs b/src/geom/spec.rs
index e7a2d056..782cf0f6 100644
--- a/src/geom/spec.rs
+++ b/src/geom/spec.rs
@@ -1,7 +1,7 @@
 use super::*;
 
 /// A container with a horizontal and vertical component.
-#[derive(Default, Copy, Clone, Eq, PartialEq)]
+#[derive(Default, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct Spec<T> {
     /// The horizontal component.
     pub horizontal: T,
diff --git a/src/layout/par.rs b/src/layout/par.rs
index 8b3cbf8b..d51bad3e 100644
--- a/src/layout/par.rs
+++ b/src/layout/par.rs
@@ -1,10 +1,11 @@
 use std::fmt::{self, Debug, Formatter};
+use std::rc::Rc;
 
 use unicode_bidi::{BidiInfo, Level};
 use xi_unicode::LineBreakIterator;
 
 use super::*;
-use crate::exec::FontProps;
+use crate::exec::FontState;
 use crate::util::{RangeExt, SliceExt};
 
 type Range = std::ops::Range<usize>;
@@ -26,7 +27,7 @@ pub enum ParChild {
     /// Spacing between other nodes.
     Spacing(Length),
     /// A run of text and how to align it in its line.
-    Text(String, FontProps, Align),
+    Text(String, Align, Rc<FontState>),
     /// Any child node and how to align it in its line.
     Any(AnyNode, Align),
 }
@@ -131,11 +132,11 @@ impl<'a> ParLayout<'a> {
                     items.push(ParItem::Spacing(amount));
                     ranges.push(range);
                 }
-                ParChild::Text(_, ref props, align) => {
+                ParChild::Text(_, align, ref state) => {
                     // TODO: Also split by language and script.
                     for (subrange, dir) in split_runs(&bidi, range) {
                         let text = &bidi.text[subrange.clone()];
-                        let shaped = shape(ctx, text, dir, props);
+                        let shaped = shape(ctx, text, dir, state);
                         items.push(ParItem::Text(shaped, align));
                         ranges.push(subrange);
                     }
diff --git a/src/layout/shaping.rs b/src/layout/shaping.rs
index 232e9fc5..d8901471 100644
--- a/src/layout/shaping.rs
+++ b/src/layout/shaping.rs
@@ -1,12 +1,12 @@
 use std::borrow::Cow;
 use std::fmt::{self, Debug, Formatter};
-use std::ops::{Add, Range};
+use std::ops::Range;
 
 use rustybuzz::UnicodeBuffer;
 
 use super::{Element, Frame, Glyph, LayoutContext, Text};
-use crate::exec::FontProps;
-use crate::font::{Em, Face, FaceId, VerticalFontMetric};
+use crate::exec::{FontState, LineState};
+use crate::font::{Face, FaceId, FontStyle, LineMetrics};
 use crate::geom::{Dir, Length, Point, Size};
 use crate::layout::Shape;
 use crate::util::SliceExt;
@@ -23,7 +23,7 @@ pub struct ShapedText<'a> {
     /// The text direction.
     pub dir: Dir,
     /// The properties used for font selection.
-    pub props: &'a FontProps,
+    pub state: &'a FontState,
     /// The font size.
     pub size: Size,
     /// The baseline from the top of the frame.
@@ -69,8 +69,8 @@ impl<'a> ShapedText<'a> {
 
             let mut text = Text {
                 face_id,
-                size: self.props.size,
-                fill: self.props.fill,
+                size: self.state.size,
+                fill: self.state.fill,
                 glyphs: vec![],
             };
 
@@ -85,7 +85,7 @@ impl<'a> ShapedText<'a> {
             }
 
             frame.push(pos, Element::Text(text));
-            decorate(ctx, &mut frame, &self.props, face_id, pos, width);
+            decorate(ctx, &mut frame, pos, width, face_id, &self.state);
 
             offset += width;
         }
@@ -101,17 +101,17 @@ impl<'a> ShapedText<'a> {
         text_range: Range<usize>,
     ) -> ShapedText<'a> {
         if let Some(glyphs) = self.slice_safe_to_break(text_range.clone()) {
-            let (size, baseline) = measure(ctx, glyphs, self.props);
+            let (size, baseline) = measure(ctx, glyphs, self.state);
             Self {
                 text: &self.text[text_range],
                 dir: self.dir,
-                props: self.props,
+                state: self.state,
                 size,
                 baseline,
                 glyphs: Cow::Borrowed(glyphs),
             }
         } else {
-            shape(ctx, &self.text[text_range], self.dir, self.props)
+            shape(ctx, &self.text[text_range], self.dir, self.state)
         }
     }
 
@@ -185,20 +185,20 @@ pub fn shape<'a>(
     ctx: &mut LayoutContext,
     text: &'a str,
     dir: Dir,
-    props: &'a FontProps,
+    state: &'a FontState,
 ) -> ShapedText<'a> {
     let mut glyphs = vec![];
-    let families = props.families.iter();
+    let families = state.families.iter();
     if !text.is_empty() {
-        shape_segment(ctx, &mut glyphs, 0, text, dir, props, families, None);
+        shape_segment(ctx, &mut glyphs, 0, text, dir, state, families, None);
     }
 
-    let (size, baseline) = measure(ctx, &glyphs, props);
+    let (size, baseline) = measure(ctx, &glyphs, state);
 
     ShapedText {
         text,
         dir,
-        props,
+        state,
         size,
         baseline,
         glyphs: Cow::Owned(glyphs),
@@ -212,7 +212,7 @@ fn shape_segment<'a>(
     base: usize,
     text: &str,
     dir: Dir,
-    props: &FontProps,
+    state: &FontState,
     mut families: impl Iterator<Item = &'a str> + Clone,
     mut first_face: Option<FaceId>,
 ) {
@@ -221,7 +221,21 @@ fn shape_segment<'a>(
         // Try to load the next available font family.
         match families.next() {
             Some(family) => {
-                match ctx.cache.font.select(ctx.loader, family, props.variant) {
+                let mut variant = state.variant;
+
+                if state.strong {
+                    variant.weight = variant.weight.thicken(300);
+                }
+
+                if state.emph {
+                    variant.style = match variant.style {
+                        FontStyle::Normal => FontStyle::Italic,
+                        FontStyle::Italic => FontStyle::Normal,
+                        FontStyle::Oblique => FontStyle::Normal,
+                    }
+                }
+
+                match ctx.cache.font.select(ctx.loader, family, variant) {
                     Some(id) => break (id, true),
                     None => {}
                 }
@@ -267,8 +281,8 @@ fn shape_segment<'a>(
             glyphs.push(ShapedGlyph {
                 face_id,
                 glyph_id: info.codepoint as u16,
-                x_advance: face.to_em(pos[i].x_advance).to_length(props.size),
-                x_offset: face.to_em(pos[i].x_offset).to_length(props.size),
+                x_advance: face.to_em(pos[i].x_advance).to_length(state.size),
+                x_offset: face.to_em(pos[i].x_offset).to_length(state.size),
                 text_index: base + cluster,
                 safe_to_break: !info.unsafe_to_break(),
             });
@@ -319,7 +333,7 @@ fn shape_segment<'a>(
                 base + range.start,
                 &text[range],
                 dir,
-                props,
+                state,
                 families.clone(),
                 first_face,
             );
@@ -336,7 +350,7 @@ fn shape_segment<'a>(
 fn measure(
     ctx: &mut LayoutContext,
     glyphs: &[ShapedGlyph],
-    props: &FontProps,
+    state: &FontState,
 ) -> (Size, Length) {
     let cache = &mut ctx.cache.font;
 
@@ -344,15 +358,15 @@ fn measure(
     let mut top = Length::zero();
     let mut bottom = Length::zero();
     let mut expand_vertical = |face: &Face| {
-        top.set_max(face.vertical_metric(props.top_edge).to_length(props.size));
-        bottom.set_max(-face.vertical_metric(props.bottom_edge).to_length(props.size));
+        top.set_max(face.vertical_metric(state.top_edge).to_length(state.size));
+        bottom.set_max(-face.vertical_metric(state.bottom_edge).to_length(state.size));
     };
 
     if glyphs.is_empty() {
         // When there are no glyphs, we just use the vertical metrics of the
         // first available font.
-        for family in props.families.iter() {
-            if let Some(face_id) = cache.select(ctx.loader, family, props.variant) {
+        for family in state.families.iter() {
+            if let Some(face_id) = cache.select(ctx.loader, family, state.variant) {
                 expand_vertical(cache.get(face_id));
                 break;
             }
@@ -375,76 +389,44 @@ fn measure(
 fn decorate(
     ctx: &LayoutContext,
     frame: &mut Frame,
-    props: &FontProps,
-    face_id: FaceId,
     pos: Point,
     width: Length,
+    face_id: FaceId,
+    state: &FontState,
 ) {
-    let mut apply = |strength, position, extent, fill| {
+    let mut apply = |substate: &LineState, metrics: fn(&Face) -> &LineMetrics| {
+        let metrics = metrics(&ctx.cache.font.get(face_id));
+
+        let strength = substate
+            .strength
+            .map(|s| s.resolve(state.size))
+            .unwrap_or(metrics.strength.to_length(state.size));
+
+        let position = substate
+            .position
+            .map(|s| s.resolve(state.size))
+            .unwrap_or(metrics.position.to_length(state.size));
+
+        let extent = substate.extent.resolve(state.size);
+        let fill = substate.fill.unwrap_or(state.fill);
+
         let pos = Point::new(pos.x - extent, pos.y - position);
         let target = Point::new(width + 2.0 * extent, Length::zero());
-        frame.push(pos, Element::Geometry(Shape::Line(target, strength), fill));
+        let shape = Shape::Line(target, strength);
+        let element = Element::Geometry(shape, fill);
+
+        frame.push(pos, element);
     };
 
-    if let Some(strikethrough) = props.strikethrough {
-        let face = ctx.cache.font.get(face_id);
-
-        let strength = strikethrough.strength.unwrap_or_else(|| {
-            face.ttf()
-                .strikeout_metrics()
-                .or_else(|| face.ttf().underline_metrics())
-                .map_or(Em::new(0.06), |m| face.to_em(m.thickness))
-                .to_length(props.size)
-        });
-
-        let position = strikethrough.position.unwrap_or_else(|| {
-            face.ttf()
-                .strikeout_metrics()
-                .map_or(Em::new(0.25), |m| face.to_em(m.position))
-                .to_length(props.size)
-        });
-
-        apply(strength, position, strikethrough.extent, strikethrough.fill);
+    if let Some(strikethrough) = &state.strikethrough {
+        apply(strikethrough, |face| &face.strikethrough);
     }
 
-    if let Some(underline) = props.underline {
-        let face = ctx.cache.font.get(face_id);
-
-        let strength = underline.strength.unwrap_or_else(|| {
-            face.ttf()
-                .underline_metrics()
-                .or_else(|| face.ttf().strikeout_metrics())
-                .map_or(Em::new(0.06), |m| face.to_em(m.thickness))
-                .to_length(props.size)
-        });
-
-        let position = underline.position.unwrap_or_else(|| {
-            face.ttf()
-                .underline_metrics()
-                .map_or(Em::new(-0.2), |m| face.to_em(m.position))
-                .to_length(props.size)
-        });
-
-        apply(strength, position, underline.extent, underline.fill);
+    if let Some(underline) = &state.underline {
+        apply(underline, |face| &face.underline);
     }
 
-    if let Some(overline) = props.overline {
-        let face = ctx.cache.font.get(face_id);
-
-        let strength = overline.strength.unwrap_or_else(|| {
-            face.ttf()
-                .underline_metrics()
-                .or_else(|| face.ttf().strikeout_metrics())
-                .map_or(Em::new(0.06), |m| face.to_em(m.thickness))
-                .to_length(props.size)
-        });
-
-        let position = overline.position.unwrap_or_else(|| {
-            face.vertical_metric(VerticalFontMetric::CapHeight)
-                .add(Em::new(0.1))
-                .to_length(props.size)
-        });
-
-        apply(strength, position, overline.extent, overline.fill);
+    if let Some(overline) = &state.overline {
+        apply(overline, |face| &face.overline);
     }
 }
diff --git a/src/library/decorations.rs b/src/library/decorations.rs
index ef9afd37..423041c1 100644
--- a/src/library/decorations.rs
+++ b/src/library/decorations.rs
@@ -55,7 +55,7 @@ fn line_impl(
     name: &str,
     ctx: &mut EvalContext,
     args: &mut FuncArgs,
-    substate: impl Fn(&mut FontState) -> &mut Option<LineState> + 'static,
+    substate: fn(&mut FontState) -> &mut Option<Rc<LineState>>,
 ) -> Value {
     let color = args.eat_named(ctx, "color");
     let position = args.eat_named(ctx, "position");
@@ -64,17 +64,19 @@ fn line_impl(
     let body = args.eat::<TemplateValue>(ctx);
 
     // Suppress any existing strikethrough if strength is explicitly zero.
-    let state = strength.map_or(true, |s| !s.is_zero()).then(|| LineState {
-        fill: color.map(Fill::Color),
-        strength,
-        position,
-        extent,
+    let state = strength.map_or(true, |s| !s.is_zero()).then(|| {
+        Rc::new(LineState {
+            strength,
+            position,
+            extent,
+            fill: color.map(Fill::Color),
+        })
     });
 
     Value::template(name, move |ctx| {
         let snapshot = ctx.state.clone();
 
-        *substate(&mut ctx.state.font) = state;
+        *substate(ctx.state.font_mut()) = state.clone();
 
         if let Some(body) = &body {
             body.exec(ctx);
diff --git a/src/library/font.rs b/src/library/font.rs
index a3fe6c13..c1ed1c98 100644
--- a/src/library/font.rs
+++ b/src/library/font.rs
@@ -64,54 +64,50 @@ pub fn font(ctx: &mut EvalContext, args: &mut FuncArgs) -> Value {
 
     Value::template("font", move |ctx| {
         let snapshot = ctx.state.clone();
+        let font = ctx.state.font_mut();
 
         if let Some(linear) = size {
-            if linear.rel.is_zero() {
-                ctx.state.font.size = linear.abs;
-                ctx.state.font.scale = Linear::one();
-            } else {
-                ctx.state.font.scale = linear;
-            }
+            font.size = linear.resolve(font.size);
         }
 
         if !list.is_empty() {
-            ctx.state.font.families_mut().list = list.clone();
+            font.families_mut().list = list.clone();
         }
 
         if let Some(style) = style {
-            ctx.state.font.variant.style = style;
+            font.variant.style = style;
         }
 
         if let Some(weight) = weight {
-            ctx.state.font.variant.weight = weight;
+            font.variant.weight = weight;
         }
 
         if let Some(stretch) = stretch {
-            ctx.state.font.variant.stretch = stretch;
+            font.variant.stretch = stretch;
         }
 
         if let Some(top_edge) = top_edge {
-            ctx.state.font.top_edge = top_edge;
+            font.top_edge = top_edge;
         }
 
         if let Some(bottom_edge) = bottom_edge {
-            ctx.state.font.bottom_edge = bottom_edge;
+            font.bottom_edge = bottom_edge;
         }
 
         if let Some(color) = color {
-            ctx.state.font.fill = Fill::Color(color);
+            font.fill = Fill::Color(color);
         }
 
         if let Some(FontFamilies(serif)) = &serif {
-            ctx.state.font.families_mut().serif = serif.clone();
+            font.families_mut().serif = serif.clone();
         }
 
         if let Some(FontFamilies(sans_serif)) = &sans_serif {
-            ctx.state.font.families_mut().sans_serif = sans_serif.clone();
+            font.families_mut().sans_serif = sans_serif.clone();
         }
 
         if let Some(FontFamilies(monospace)) = &monospace {
-            ctx.state.font.families_mut().monospace = monospace.clone();
+            font.families_mut().monospace = monospace.clone();
         }
 
         if let Some(body) = &body {
diff --git a/src/library/mod.rs b/src/library/mod.rs
index 553b39e6..0536eaa1 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -34,6 +34,7 @@ pub use spacing::*;
 pub use stack::*;
 
 use std::fmt::{self, Display, Formatter};
+use std::rc::Rc;
 
 use crate::color::RgbaColor;
 use crate::eval::{EvalContext, FuncArgs, Scope, TemplateValue, Value};
diff --git a/src/library/spacing.rs b/src/library/spacing.rs
index ff6aaa69..654a18c4 100644
--- a/src/library/spacing.rs
+++ b/src/library/spacing.rs
@@ -31,7 +31,8 @@ fn spacing_impl(
     let spacing: Option<Linear> = args.eat_expect(ctx, "spacing");
     Value::template(name, move |ctx| {
         if let Some(linear) = spacing {
-            let amount = linear.resolve(ctx.state.font.resolve_size());
+            // TODO: Should this really always be font-size relative?
+            let amount = linear.resolve(ctx.state.font.size);
             ctx.push_spacing(axis, amount);
         }
     })
diff --git a/src/paper.rs b/src/paper.rs
index 58d87be1..8dfc071c 100644
--- a/src/paper.rs
+++ b/src/paper.rs
@@ -26,7 +26,7 @@ impl Paper {
 }
 
 /// Defines default margins for a class of related papers.
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum PaperClass {
     Custom,
     Base,