Deduplicate ttf-parser and rustybuzz face 🥞

1 files changed, 33 insertions, 27 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 {