Deduplicate ttf-parser and rustybuzz face 🥞

3 files changed, 66 insertions, 54 deletions

diff --git a/src/font.rs b/src/font.rs
index a816ed06..1ac8fea3 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -10,8 +10,7 @@ use crate::geom::Length;
 pub struct FaceBuf {
     data: Box<[u8]>,
     index: u32,
-    ttf: ttf_parser::Face<'static>,
-    buzz: rustybuzz::Face<'static>,
+    inner: rustybuzz::Face<'static>,
     units_per_em: f64,
     ascender: f64,
     cap_height: f64,
@@ -30,23 +29,16 @@ impl FaceBuf {
         self.index
     }
 
-    /// Get a reference to the underlying ttf-parser face.
-    pub fn ttf(&self) -> &ttf_parser::Face<'_> {
+    /// Get a reference to the underlying ttf-parser/rustybuzz face.
+    pub fn ttf(&self) -> &rustybuzz::Face<'_> {
         // We can't implement Deref because that would leak the internal 'static
         // lifetime.
-        &self.ttf
+        &self.inner
     }
 
-    /// Get a reference to the underlying rustybuzz face.
-    pub fn buzz(&self) -> &rustybuzz::Face<'_> {
-        // We can't implement Deref because that would leak the internal 'static
-        // lifetime.
-        &self.buzz
-    }
-
-    /// Look up a vertical metric at a given font size.
-    pub fn vertical_metric(&self, size: Length, metric: VerticalFontMetric) -> Length {
-        self.convert(size, match metric {
+    /// Look up a vertical metric.
+    pub fn vertical_metric(&self, metric: VerticalFontMetric) -> EmLength {
+        self.convert(match metric {
             VerticalFontMetric::Ascender => self.ascender,
             VerticalFontMetric::CapHeight => self.cap_height,
             VerticalFontMetric::XHeight => self.x_height,
@@ -55,9 +47,9 @@ impl FaceBuf {
         })
     }
 
-    /// Convert from font units to a length at a given font size.
-    pub fn convert(&self, size: Length, units: impl Into<f64>) -> Length {
-        units.into() / self.units_per_em * size
+    /// Convert from font units to an em length length.
+    pub fn convert(&self, units: impl Into<f64>) -> EmLength {
+        EmLength(units.into() / self.units_per_em)
     }
 }
 
@@ -70,21 +62,19 @@ impl FaceFromVec for FaceBuf {
         let slice: &'static [u8] =
             unsafe { std::slice::from_raw_parts(data.as_ptr(), data.len()) };
 
-        let ttf = ttf_parser::Face::from_slice(slice, index).ok()?;
-        let buzz = rustybuzz::Face::from_slice(slice, index)?;
+        let inner = rustybuzz::Face::from_slice(slice, index)?;
 
         // Look up some metrics we may need often.
-        let units_per_em = ttf.units_per_em().unwrap_or(1000);
-        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 units_per_em = inner.units_per_em();
+        let ascender = inner.typographic_ascender().unwrap_or(inner.ascender());
+        let cap_height = inner.capital_height().filter(|&h| h > 0).unwrap_or(ascender);
+        let x_height = inner.x_height().filter(|&h| h > 0).unwrap_or(ascender);
+        let descender = inner.typographic_descender().unwrap_or(inner.descender());
 
         Some(Self {
             data,
             index,
-            ttf,
-            buzz,
+            inner,
             units_per_em: f64::from(units_per_em),
             ascender: f64::from(ascender),
             cap_height: f64::from(cap_height),
@@ -94,6 +84,22 @@ impl FaceFromVec for FaceBuf {
     }
 }
 
+/// A length in resolved em units.
+#[derive(Default, Debug, Copy, Clone, PartialEq, PartialOrd)]
+pub struct EmLength(f64);
+
+impl EmLength {
+    /// Convert to a length at the given font size.
+    pub fn scale(self, size: Length) -> Length {
+        self.0 * size
+    }
+
+    /// Get the number of em units.
+    pub fn get(self) -> f64 {
+        self.0
+    }
+}
+
 /// Identifies a vertical metric of a font.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
 pub enum VerticalFontMetric {
diff --git a/src/layout/shaping.rs b/src/layout/shaping.rs
index b062f602..14dd79b1 100644
--- a/src/layout/shaping.rs
+++ b/src/layout/shaping.rs
@@ -39,7 +39,7 @@ pub struct ShapedGlyph {
     /// The font face the glyph is contained in.
     pub face_id: FaceId,
     /// The glyph's ID in the face.
-    pub id: GlyphId,
+    pub glyph_id: GlyphId,
     /// The advance width of the glyph.
     pub x_advance: i32,
     /// The horizontal offset of the glyph.
@@ -59,8 +59,6 @@ impl<'a> ShapedText<'a> {
         let mut x = Length::ZERO;
 
         for (face_id, group) in self.glyphs.as_ref().group_by_key(|g| g.face_id) {
-            let face = loader.face(face_id);
-
             let pos = Point::new(x, self.baseline);
             let mut text = Text {
                 face_id,
@@ -69,10 +67,11 @@ impl<'a> ShapedText<'a> {
                 glyphs: vec![],
             };
 
+            let face = loader.face(face_id);
             for glyph in group {
-                let x_advance = face.convert(self.props.size, glyph.x_advance);
-                let x_offset = face.convert(self.props.size, glyph.x_offset);
-                text.glyphs.push(Glyph { id: glyph.id, x_advance, x_offset });
+                let x_advance = face.convert(glyph.x_advance).scale(self.props.size);
+                let x_offset = face.convert(glyph.x_offset).scale(self.props.size);
+                text.glyphs.push(Glyph { id: glyph.glyph_id, x_advance, x_offset });
                 x += x_advance;
             }
 
@@ -218,7 +217,7 @@ fn shape_segment<'a>(
     });
 
     // Shape!
-    let buffer = rustybuzz::shape(loader.face(face_id).buzz(), &[], buffer);
+    let buffer = rustybuzz::shape(loader.face(face_id).ttf(), &[], buffer);
     let infos = buffer.glyph_infos();
     let pos = buffer.glyph_positions();
 
@@ -233,7 +232,7 @@ fn shape_segment<'a>(
             // TODO: Don't ignore y_advance and y_offset.
             glyphs.push(ShapedGlyph {
                 face_id,
-                id: GlyphId(info.codepoint as u16),
+                glyph_id: GlyphId(info.codepoint as u16),
                 x_advance: pos[i].x_advance,
                 x_offset: pos[i].x_offset,
                 text_index: base + cluster,
@@ -306,8 +305,8 @@ fn measure(
     let mut bottom = Length::ZERO;
     let mut width = Length::ZERO;
     let mut vertical = |face: &FaceBuf| {
-        top = top.max(face.vertical_metric(props.size, props.top_edge));
-        bottom = bottom.max(-face.vertical_metric(props.size, props.bottom_edge));
+        top = top.max(face.vertical_metric(props.top_edge).scale(props.size));
+        bottom = bottom.max(-face.vertical_metric(props.bottom_edge).scale(props.size));
     };
 
     if glyphs.is_empty() {
@@ -325,7 +324,7 @@ fn measure(
             vertical(face);
 
             for glyph in group {
-                width += face.convert(props.size, glyph.x_advance);
+                width += face.convert(glyph.x_advance).scale(props.size);
             }
         }
     }
diff --git a/src/pdf/mod.rs b/src/pdf/mod.rs
index 656635fc..36527544 100644
--- a/src/pdf/mod.rs
+++ b/src/pdf/mod.rs
@@ -15,6 +15,7 @@ use ttf_parser::{name_id, GlyphId};
 
 use crate::color::Color;
 use crate::env::{Env, ImageResource, ResourceId};
+use crate::font::{EmLength, VerticalFontMetric};
 use crate::geom::{self, Length, Size};
 use crate::layout::{Element, Fill, Frame, Image, Shape};
 
@@ -234,24 +235,18 @@ impl<'a> PdfExporter<'a> {
             flags.insert(FontFlags::SYMBOLIC);
             flags.insert(FontFlags::SMALL_CAP);
 
-            // Convert from OpenType font units to PDF glyph units.
-            let em_per_unit = 1.0 / ttf.units_per_em().unwrap_or(1000) as f32;
-            let convert = |font_unit: f32| (1000.0 * em_per_unit * font_unit).round();
-            let convert_i16 = |font_unit: i16| convert(font_unit as f32);
-            let convert_u16 = |font_unit: u16| convert(font_unit as f32);
-
             let global_bbox = ttf.global_bounding_box();
             let bbox = Rect::new(
-                convert_i16(global_bbox.x_min),
-                convert_i16(global_bbox.y_min),
-                convert_i16(global_bbox.x_max),
-                convert_i16(global_bbox.y_max),
+                face.convert(global_bbox.x_min).to_pdf(),
+                face.convert(global_bbox.y_min).to_pdf(),
+                face.convert(global_bbox.x_max).to_pdf(),
+                face.convert(global_bbox.y_max).to_pdf(),
             );
 
             let italic_angle = ttf.italic_angle().unwrap_or(0.0);
-            let ascender = convert_i16(ttf.typographic_ascender().unwrap_or(0));
-            let descender = convert_i16(ttf.typographic_descender().unwrap_or(0));
-            let cap_height = ttf.capital_height().map(convert_i16);
+            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 stem_v = 10.0 + 0.244 * (f32::from(ttf.weight().to_number()) - 50.0);
 
             // Write the base font object referencing the CID font.
@@ -272,8 +267,8 @@ impl<'a> PdfExporter<'a> {
                 .individual(0, {
                     let num_glyphs = ttf.number_of_glyphs();
                     (0 .. num_glyphs).map(|g| {
-                        let advance = ttf.glyph_hor_advance(GlyphId(g));
-                        convert_u16(advance.unwrap_or(0))
+                        let x = ttf.glyph_hor_advance(GlyphId(g)).unwrap_or(0);
+                        face.convert(x).to_pdf()
                     })
                 });
 
@@ -286,7 +281,7 @@ impl<'a> PdfExporter<'a> {
                 .italic_angle(italic_angle)
                 .ascent(ascender)
                 .descent(descender)
-                .cap_height(cap_height.unwrap_or(ascender))
+                .cap_height(cap_height)
                 .stem_v(stem_v)
                 .font_file2(refs.data);
 
@@ -571,3 +566,15 @@ where
         self.to_layout.iter().copied()
     }
 }
+
+/// Additional methods for [`EmLength`].
+trait EmLengthExt {
+    /// Convert an em length to a number of PDF font units.
+    fn to_pdf(self) -> f32;
+}
+
+impl EmLengthExt for EmLength {
+    fn to_pdf(self) -> f32 {
+        1000.0 * self.get() as f32
+    }
+}