Use the shaper in math (#6336)

3 files changed, 50 insertions, 1 deletions

diff --git a/crates/typst-library/src/text/font/mod.rs b/crates/typst-library/src/text/font/mod.rs
index afa92e77..0383bfe1 100644
--- a/crates/typst-library/src/text/font/mod.rs
+++ b/crates/typst-library/src/text/font/mod.rs
@@ -106,13 +106,26 @@ impl Font {
     }
 
     /// Look up the horizontal advance width of a glyph.
-    pub fn advance(&self, glyph: u16) -> Option<Em> {
+    pub fn x_advance(&self, glyph: u16) -> Option<Em> {
         self.0
             .ttf
             .glyph_hor_advance(GlyphId(glyph))
             .map(|units| self.to_em(units))
     }
 
+    /// Look up the vertical advance width of a glyph.
+    pub fn y_advance(&self, glyph: u16) -> Option<Em> {
+        self.0
+            .ttf
+            .glyph_ver_advance(GlyphId(glyph))
+            .map(|units| self.to_em(units))
+    }
+
+    /// Look up the width of a space.
+    pub fn space_width(&self) -> Option<Em> {
+        self.0.ttf.glyph_index(' ').and_then(|id| self.x_advance(id.0))
+    }
+
     /// Lookup a name by id.
     pub fn find_name(&self, id: u16) -> Option<String> {
         find_name(&self.0.ttf, id)
diff --git a/crates/typst-library/src/text/item.rs b/crates/typst-library/src/text/item.rs
index ed559aec..518b082b 100644
--- a/crates/typst-library/src/text/item.rs
+++ b/crates/typst-library/src/text/item.rs
@@ -35,6 +35,11 @@ impl TextItem {
     pub fn width(&self) -> Abs {
         self.glyphs.iter().map(|g| g.x_advance).sum::<Em>().at(self.size)
     }
+
+    /// The height of the text run.
+    pub fn height(&self) -> Abs {
+        self.glyphs.iter().map(|g| g.y_advance).sum::<Em>().at(self.size)
+    }
 }
 
 impl Debug for TextItem {
@@ -54,6 +59,10 @@ pub struct Glyph {
     pub x_advance: Em,
     /// The horizontal offset of the glyph.
     pub x_offset: Em,
+    /// The advance height (Y-up) of the glyph.
+    pub y_advance: Em,
+    /// The vertical offset (Y-up) of the glyph.
+    pub y_offset: Em,
     /// The range of the glyph in its item's text. The range's length may
     /// be more than one due to multi-byte UTF-8 encoding or ligatures.
     pub range: Range<u16>,
@@ -115,4 +124,13 @@ impl<'a> TextItemView<'a> {
             .sum::<Em>()
             .at(self.item.size)
     }
+
+    /// The total height of this text slice
+    pub fn height(&self) -> Abs {
+        self.glyphs()
+            .iter()
+            .map(|g| g.y_advance)
+            .sum::<Em>()
+            .at(self.item.size)
+    }
 }
diff --git a/crates/typst-library/src/text/mod.rs b/crates/typst-library/src/text/mod.rs
index 23edc9e9..1c0696d1 100644
--- a/crates/typst-library/src/text/mod.rs
+++ b/crates/typst-library/src/text/mod.rs
@@ -30,6 +30,7 @@ pub use self::space::*;
 
 use std::fmt::{self, Debug, Formatter};
 use std::hash::Hash;
+use std::str::FromStr;
 use std::sync::LazyLock;
 
 use ecow::{eco_format, EcoString};
@@ -1283,6 +1284,12 @@ pub fn features(styles: StyleChain) -> Vec<Feature> {
         feat(b"frac", 1);
     }
 
+    match EquationElem::size_in(styles) {
+        MathSize::Script => feat(b"ssty", 1),
+        MathSize::ScriptScript => feat(b"ssty", 2),
+        _ => {}
+    }
+
     for (tag, value) in TextElem::features_in(styles).0 {
         tags.push(Feature::new(tag, value, ..))
     }
@@ -1290,6 +1297,17 @@ pub fn features(styles: StyleChain) -> Vec<Feature> {
     tags
 }
 
+/// Process the language and region of a style chain into a
+/// rustybuzz-compatible BCP 47 language.
+pub fn language(styles: StyleChain) -> rustybuzz::Language {
+    let mut bcp: EcoString = TextElem::lang_in(styles).as_str().into();
+    if let Some(region) = TextElem::region_in(styles) {
+        bcp.push('-');
+        bcp.push_str(region.as_str());
+    }
+    rustybuzz::Language::from_str(&bcp).unwrap()
+}
+
 /// A toggle that turns on and off alternatingly if folded.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct ItalicToggle(pub bool);