Fix math styling

9 files changed, 167 insertions, 132 deletions

diff --git a/library/src/math/ctx.rs b/library/src/math/ctx.rs
index 547d3cc8..fafb96f2 100644
--- a/library/src/math/ctx.rs
+++ b/library/src/math/ctx.rs
@@ -1,4 +1,5 @@
 use ttf_parser::math::MathValue;
+use typst::font::{FontStyle, FontWeight};
 use unicode_segmentation::UnicodeSegmentation;
 
 use super::*;
@@ -24,21 +25,18 @@ macro_rules! percent {
 /// The context for math layout.
 pub(super) struct MathContext<'a, 'b, 'v> {
     pub vt: &'v mut Vt<'b>,
-    pub outer: StyleChain<'a>,
-    pub map: StyleMap,
     pub regions: Regions<'a>,
     pub font: &'a Font,
     pub ttf: &'a ttf_parser::Face<'a>,
     pub table: ttf_parser::math::Table<'a>,
     pub constants: ttf_parser::math::Constants<'a>,
     pub space_width: Em,
-    pub fill: Paint,
-    pub lang: Lang,
     pub row: MathRow,
+    pub map: StyleMap,
     pub style: MathStyle,
-    base_size: Abs,
-    scaled_size: Abs,
-    style_stack: Vec<MathStyle>,
+    pub size: Abs,
+    outer: StyleChain<'a>,
+    style_stack: Vec<(MathStyle, Abs)>,
 }
 
 impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
@@ -52,7 +50,6 @@ impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
         let table = font.ttf().tables().math.unwrap();
         let constants = table.constants.unwrap();
         let size = styles.get(TextNode::SIZE);
-
         let ttf = font.ttf();
         let space_width = ttf
             .glyph_index(' ')
@@ -60,38 +57,38 @@ impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
             .map(|advance| font.to_em(advance))
             .unwrap_or(THICK);
 
+        let variant = variant(styles);
         Self {
             vt,
-            outer: styles,
-            map: StyleMap::new(),
             regions: {
                 let size = Size::new(regions.first.x, regions.base.y);
                 Regions::one(size, regions.base, Axes::splat(false))
             },
-            style: MathStyle {
-                variant: MathVariant::Serif,
-                size: if block { MathSize::Display } else { MathSize::Text },
-                cramped: false,
-                bold: false,
-                italic: true,
-            },
-            fill: styles.get(TextNode::FILL),
-            lang: styles.get(TextNode::LANG),
             font: &font,
             ttf: font.ttf(),
             table,
             constants,
             space_width,
             row: MathRow::new(),
-            base_size: size,
-            scaled_size: size,
+            map: StyleMap::new(),
+            style: MathStyle {
+                variant: MathVariant::Serif,
+                size: if block { MathSize::Display } else { MathSize::Text },
+                cramped: false,
+                bold: variant.weight >= FontWeight::BOLD,
+                italic: match variant.style {
+                    FontStyle::Normal => Smart::Auto,
+                    FontStyle::Italic | FontStyle::Oblique => Smart::Custom(true),
+                },
+            },
+            size,
+            outer: styles,
             style_stack: vec![],
         }
     }
 
     pub fn push(&mut self, fragment: impl Into<MathFragment>) {
-        self.row
-            .push(self.scaled_size, self.space_width, self.style, fragment);
+        self.row.push(self.size, self.space_width, self.style, fragment);
     }
 
     pub fn extend(&mut self, row: MathRow) {
@@ -130,11 +127,12 @@ impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
         Ok(self.layout_fragment(node)?.to_frame(self))
     }
 
-    pub fn layout_text(&mut self, text: &EcoString) -> SourceResult<()> {
+    pub fn layout_text(&mut self, text: &str) -> SourceResult<()> {
         let mut chars = text.chars();
         if let Some(glyph) = chars
             .next()
             .filter(|_| chars.next().is_none())
+            .map(|c| self.style.styled_char(c))
             .and_then(|c| GlyphFragment::try_new(self, c))
         {
             // A single letter that is available in the math font.
@@ -147,10 +145,10 @@ impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
                 self.push(glyph);
             }
         } else if text.chars().all(|c| c.is_ascii_digit()) {
-            // A number that should respect math styling and can therefore
-            // not fall back to the normal text layout.
+            // Numbers aren't that difficult.
             let mut vec = vec![];
             for c in text.chars() {
+                let c = self.style.styled_char(c);
                 vec.push(GlyphFragment::new(self, c).into());
             }
             let frame = MathRow(vec).to_frame(self);
@@ -158,7 +156,12 @@ impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
         } else {
             // Anything else is handled by Typst's standard text layout.
             let spaced = text.graphemes(true).count() > 1;
-            let frame = self.layout_non_math(&TextNode::packed(text.clone()))?;
+            let mut style = self.style;
+            if self.style.italic == Smart::Auto {
+                style = style.with_italic(false);
+            }
+            let text: EcoString = text.chars().map(|c| style.styled_char(c)).collect();
+            let frame = self.layout_non_math(&TextNode::packed(text))?;
             self.push(
                 FrameFragment::new(frame)
                     .with_class(MathClass::Alphabetic)
@@ -169,33 +172,35 @@ impl<'a, 'b, 'v> MathContext<'a, 'b, 'v> {
         Ok(())
     }
 
-    pub fn size(&self) -> Abs {
-        self.scaled_size
+    pub fn styles(&self) -> StyleChain {
+        self.outer.chain(&self.map)
     }
 
     pub fn style(&mut self, style: MathStyle) {
-        self.style_stack.push(self.style);
+        self.style_stack.push((self.style, self.size));
+        let base_size = self.styles().get(TextNode::SIZE) / self.style.size.factor(self);
+        self.size = base_size * style.size.factor(self);
+        self.map.set(TextNode::SIZE, TextSize(self.size.into()));
+        self.map.set(
+            TextNode::STYLE,
+            if style.italic == Smart::Custom(true) {
+                FontStyle::Italic
+            } else {
+                FontStyle::Normal
+            },
+        );
+        self.map.set(
+            TextNode::WEIGHT,
+            if style.bold { FontWeight::BOLD } else { FontWeight::REGULAR },
+        );
         self.style = style;
-        self.rescale();
-        self.map.set(TextNode::SIZE, TextSize(self.scaled_size.into()));
     }
 
     pub fn unstyle(&mut self) {
-        self.style = self.style_stack.pop().unwrap();
-        self.rescale();
+        (self.style, self.size) = self.style_stack.pop().unwrap();
+        self.map.unset();
+        self.map.unset();
         self.map.unset();
-    }
-
-    fn rescale(&mut self) {
-        self.scaled_size = match self.style.size {
-            MathSize::Display | MathSize::Text => self.base_size,
-            MathSize::Script => {
-                self.base_size * percent!(self, script_percent_scale_down)
-            }
-            MathSize::ScriptScript => {
-                self.base_size * percent!(self, script_script_percent_scale_down)
-            }
-        };
     }
 }
 
@@ -217,7 +222,7 @@ impl Scaled for u16 {
 
 impl Scaled for Em {
     fn scaled(self, ctx: &MathContext) -> Abs {
-        self.at(ctx.size())
+        self.at(ctx.size)
     }
 }
 
diff --git a/library/src/math/frac.rs b/library/src/math/frac.rs
index e945473c..ebdb5c02 100644
--- a/library/src/math/frac.rs
+++ b/library/src/math/frac.rs
@@ -157,8 +157,10 @@ fn layout(
         frame.push(
             line_pos,
             Element::Shape(
-                Geometry::Line(Point::with_x(line_width))
-                    .stroked(Stroke { paint: ctx.fill, thickness }),
+                Geometry::Line(Point::with_x(line_width)).stroked(Stroke {
+                    paint: ctx.styles().get(TextNode::FILL),
+                    thickness,
+                }),
             ),
         );
         ctx.push(frame);
diff --git a/library/src/math/fragment.rs b/library/src/math/fragment.rs
index fef57a0a..a7ca8db3 100644
--- a/library/src/math/fragment.rs
+++ b/library/src/math/fragment.rs
@@ -121,6 +121,8 @@ impl From<Frame> for MathFragment {
 pub(super) struct GlyphFragment {
     pub id: GlyphId,
     pub c: char,
+    pub lang: Lang,
+    pub fill: Paint,
     pub font_size: Abs,
     pub width: Abs,
     pub ascent: Abs,
@@ -131,7 +133,6 @@ pub(super) struct GlyphFragment {
 
 impl GlyphFragment {
     pub fn new(ctx: &MathContext, c: char) -> Self {
-        let c = ctx.style.styled_char(c);
         let id = ctx.ttf.glyph_index(c).unwrap_or_default();
         Self::with_id(ctx, c, id)
     }
@@ -154,7 +155,9 @@ impl GlyphFragment {
         Self {
             id,
             c,
-            font_size: ctx.size(),
+            lang: ctx.styles().get(TextNode::LANG),
+            fill: ctx.styles().get(TextNode::FILL),
+            font_size: ctx.size,
             width: advance.scaled(ctx),
             ascent: bbox.y_max.scaled(ctx),
             descent: -bbox.y_min.scaled(ctx),
@@ -184,12 +187,12 @@ impl GlyphFragment {
         let text = Text {
             font: ctx.font.clone(),
             size: self.font_size,
-            fill: ctx.fill,
-            lang: ctx.lang,
+            fill: self.fill,
+            lang: self.lang,
             glyphs: vec![Glyph {
                 id: self.id.0,
                 c: self.c,
-                x_advance: Em::from_length(self.width, ctx.size()),
+                x_advance: Em::from_length(self.width, ctx.size),
                 x_offset: Em::zero(),
             }],
         };
diff --git a/library/src/math/lr.rs b/library/src/math/lr.rs
index 30ff532a..e265affb 100644
--- a/library/src/math/lr.rs
+++ b/library/src/math/lr.rs
@@ -66,7 +66,7 @@ impl LayoutMath for LrNode {
         let height = self
             .size
             .unwrap_or(Rel::one())
-            .resolve(ctx.outer.chain(&ctx.map))
+            .resolve(ctx.styles())
             .relative_to(2.0 * max_extent);
 
         match row.0.as_mut_slice() {
diff --git a/library/src/math/matrix.rs b/library/src/math/matrix.rs
index 45ebdda7..72ef0253 100644
--- a/library/src/math/matrix.rs
+++ b/library/src/math/matrix.rs
@@ -39,20 +39,11 @@ impl VecNode {
     fn construct(_: &Vm, args: &mut Args) -> SourceResult<Content> {
         Ok(Self(args.all()?).pack())
     }
-
-    fn field(&self, name: &str) -> Option<Value> {
-        match name {
-            "elements" => {
-                Some(Value::Array(self.0.iter().cloned().map(Value::Content).collect()))
-            }
-            _ => None,
-        }
-    }
 }
 
 impl LayoutMath for VecNode {
     fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
-        let delim = ctx.outer.get(Self::DELIM);
+        let delim = ctx.styles().get(Self::DELIM);
         layout(ctx, &self.0, Align::Center, Some(delim.open()), Some(delim.close()))
     }
 }
@@ -86,15 +77,6 @@ impl CasesNode {
     fn construct(_: &Vm, args: &mut Args) -> SourceResult<Content> {
         Ok(Self(args.all()?).pack())
     }
-
-    fn field(&self, name: &str) -> Option<Value> {
-        match name {
-            "branches" => {
-                Some(Value::Array(self.0.iter().cloned().map(Value::Content).collect()))
-            }
-            _ => None,
-        }
-    }
 }
 
 impl LayoutMath for CasesNode {
diff --git a/library/src/math/mod.rs b/library/src/math/mod.rs
index f1bcd8f4..ab67a0d3 100644
--- a/library/src/math/mod.rs
+++ b/library/src/math/mod.rs
@@ -29,29 +29,27 @@ pub use self::root::*;
 pub use self::stack::*;
 pub use self::style::*;
 
-use ttf_parser::GlyphId;
-use ttf_parser::Rect;
+use ttf_parser::{GlyphId, Rect};
 use typst::font::Font;
-use typst::model::{Guard, Module, Scope, SequenceNode};
+use typst::model::{Guard, Module, Scope, SequenceNode, StyledNode};
 use unicode_math_class::MathClass;
 
 use self::ctx::*;
 use self::fragment::*;
 use self::row::*;
 use self::spacing::*;
-use crate::layout::HNode;
-use crate::layout::ParNode;
-use crate::layout::Spacing;
+use crate::layout::{HNode, ParNode, Spacing};
 use crate::prelude::*;
-use crate::text::LinebreakNode;
-use crate::text::TextNode;
-use crate::text::TextSize;
-use crate::text::{families, variant, FallbackList, FontFamily, SpaceNode};
+use crate::text::{
+    families, variant, FallbackList, FontFamily, LinebreakNode, SpaceNode, TextNode,
+    TextSize,
+};
 
 /// Create a module with all math definitions.
 pub fn module(sym: &Module) -> Module {
     let mut math = Scope::deduplicating();
     math.def_func::<FormulaNode>("formula");
+    math.def_func::<TextNode>("text");
 
     // Grouping.
     math.def_func::<LrNode>("lr");
@@ -83,6 +81,7 @@ pub fn module(sym: &Module) -> Module {
     math.def_func::<RootNode>("root");
 
     // Styles.
+    math.def_func::<UprightNode>("upright");
     math.def_func::<BoldNode>("bold");
     math.def_func::<ItalicNode>("italic");
     math.def_func::<SerifNode>("serif");
@@ -243,6 +242,24 @@ impl LayoutMath for FormulaNode {
 
 impl LayoutMath for Content {
     fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
+        if let Some(node) = self.to::<SequenceNode>() {
+            for child in &node.0 {
+                child.layout_math(ctx)?;
+            }
+            return Ok(());
+        }
+
+        if let Some(styled) = self.to::<StyledNode>() {
+            let prev_map = std::mem::replace(&mut ctx.map, styled.map.clone());
+            let prev_size = ctx.size;
+            ctx.map.apply(prev_map.clone());
+            ctx.size = ctx.styles().get(TextNode::SIZE);
+            styled.sub.layout_math(ctx)?;
+            ctx.size = prev_size;
+            ctx.map = prev_map;
+            return Ok(());
+        }
+
         if self.is::<SpaceNode>() {
             ctx.push(MathFragment::Space);
             return Ok(());
@@ -256,9 +273,7 @@ impl LayoutMath for Content {
         if let Some(node) = self.to::<HNode>() {
             if let Spacing::Relative(rel) = node.amount {
                 if rel.rel.is_zero() {
-                    ctx.push(MathFragment::Spacing(
-                        rel.abs.resolve(ctx.outer.chain(&ctx.map)),
-                    ));
+                    ctx.push(MathFragment::Spacing(rel.abs.resolve(ctx.styles())));
                 }
             }
             return Ok(());
@@ -269,13 +284,6 @@ impl LayoutMath for Content {
             return Ok(());
         }
 
-        if let Some(node) = self.to::<SequenceNode>() {
-            for child in &node.0 {
-                child.layout_math(ctx)?;
-            }
-            return Ok(());
-        }
-
         if let Some(node) = self.with::<dyn LayoutMath>() {
             return node.layout_math(ctx);
         }
diff --git a/library/src/math/root.rs b/library/src/math/root.rs
index 79bcfe38..1416325c 100644
--- a/library/src/math/root.rs
+++ b/library/src/math/root.rs
@@ -144,7 +144,7 @@ fn layout(
         line_pos,
         Element::Shape(
             Geometry::Line(Point::with_x(line_length))
-                .stroked(Stroke { paint: ctx.fill, thickness }),
+                .stroked(Stroke { paint: ctx.styles().get(TextNode::FILL), thickness }),
         ),
     );
     frame.push_frame(radicand_pos, radicand);
diff --git a/library/src/math/row.rs b/library/src/math/row.rs
index f75aed99..bc013182 100644
--- a/library/src/math/row.rs
+++ b/library/src/math/row.rs
@@ -77,7 +77,7 @@ impl MathRow {
             let mut frame = Frame::new(Size::zero());
             let fragments = std::mem::take(&mut self.0);
 
-            let leading = ctx.outer.chain(&ctx.map).get(ParNode::LEADING);
+            let leading = ctx.styles().get(ParNode::LEADING);
             let rows: Vec<_> = fragments
                 .split(|frag| matches!(frag, MathFragment::Linebreak))
                 .map(|slice| Self(slice.to_vec()))
diff --git a/library/src/math/style.rs b/library/src/math/style.rs
index d408b532..14f97ae8 100644
--- a/library/src/math/style.rs
+++ b/library/src/math/style.rs
@@ -1,5 +1,40 @@
 use super::*;
 
+/// # Upright
+/// Upright (non-italic) font style in math.
+///
+/// ## Example
+/// ```
+/// $ upright(A) != A $
+/// ```
+///
+/// ## Parameters
+/// - body: Content (positional, required)
+///   The piece of formula to style.
+///
+/// ## Category
+/// math
+#[func]
+#[capable(LayoutMath)]
+#[derive(Debug, Hash)]
+pub struct UprightNode(pub Content);
+
+#[node]
+impl UprightNode {
+    fn construct(_: &Vm, args: &mut Args) -> SourceResult<Content> {
+        Ok(Self(args.expect("body")?).pack())
+    }
+}
+
+impl LayoutMath for UprightNode {
+    fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
+        ctx.style(ctx.style.with_italic(false));
+        self.0.layout_math(ctx)?;
+        ctx.unstyle();
+        Ok(())
+    }
+}
+
 /// # Bold
 /// Bold font style in math.
 ///
@@ -28,7 +63,7 @@ impl BoldNode {
 
 impl LayoutMath for BoldNode {
     fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
-        ctx.style(ctx.style.with_italic(false).with_bold_toggled());
+        ctx.style(ctx.style.with_bold(true));
         self.0.layout_math(ctx)?;
         ctx.unstyle();
         Ok(())
@@ -60,7 +95,7 @@ impl ItalicNode {
 
 impl LayoutMath for ItalicNode {
     fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
-        ctx.style(ctx.style.with_italic_toggled());
+        ctx.style(ctx.style.with_italic(true));
         self.0.layout_math(ctx)?;
         ctx.unstyle();
         Ok(())
@@ -290,22 +325,7 @@ pub struct MathStyle {
     /// Whether to use bold glyphs.
     pub bold: bool,
     /// Whether to use italic glyphs.
-    pub italic: bool,
-}
-
-/// The size of elements in a formula.
-///
-/// See the TeXbook p. 141.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
-pub enum MathSize {
-    /// Second-level sub- and superscripts.
-    ScriptScript,
-    /// Sub- and superscripts.
-    Script,
-    /// Math in text.
-    Text,
-    /// Math on its own line.
-    Display,
+    pub italic: Smart<bool>,
 }
 
 impl MathStyle {
@@ -331,17 +351,7 @@ impl MathStyle {
 
     /// This style, with `italic` set to the given value.
     pub fn with_italic(self, italic: bool) -> Self {
-        Self { italic, ..self }
-    }
-
-    /// This style, with boldness inverted.
-    pub fn with_bold_toggled(self) -> Self {
-        self.with_bold(!self.bold)
-    }
-
-    /// This style, with italicness inverted.
-    pub fn with_italic_toggled(self) -> Self {
-        self.with_italic(!self.italic)
+        Self { italic: Smart::Custom(italic), ..self }
     }
 
     /// The style for subscripts in the current style.
@@ -377,6 +387,31 @@ impl MathStyle {
     }
 }
 
+/// The size of elements in a formula.
+///
+/// See the TeXbook p. 141.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
+pub enum MathSize {
+    /// Second-level sub- and superscripts.
+    ScriptScript,
+    /// Sub- and superscripts.
+    Script,
+    /// Math in text.
+    Text,
+    /// Math on its own line.
+    Display,
+}
+
+impl MathSize {
+    pub(super) fn factor(self, ctx: &MathContext) -> f64 {
+        match self {
+            Self::Display | Self::Text => 1.0,
+            Self::Script => percent!(ctx, script_percent_scale_down),
+            Self::ScriptScript => percent!(ctx, script_script_percent_scale_down),
+        }
+    }
+}
+
 /// A mathematical style variant, as defined by Unicode.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum MathVariant {
@@ -401,17 +436,17 @@ impl Default for MathVariant {
 pub(super) fn styled_char(style: MathStyle, c: char) -> char {
     use MathVariant::*;
 
-    let tuple = (style.variant, style.bold, style.italic);
-    let base = match c {
-        'a'..='z' => 'a',
-        'A'..='Z' => 'A',
-        'α'..='ω' => 'α',
-        'Α'..='Ω' => 'Α',
-        '0'..='9' => '0',
+    let (base, default_italic) = match c {
+        'a'..='z' => ('a', true),
+        'A'..='Z' => ('A', true),
+        'α'..='ω' => ('α', false),
+        'Α'..='Ω' => ('Α', false),
+        '0'..='9' => ('0', false),
         '-' => return '−',
         _ => return c,
     };
 
+    let tuple = (style.variant, style.bold, style.italic.unwrap_or(default_italic));
     let start = match c {
         // Latin upper.
         'A'..='Z' => match tuple {