Rework font cache to cache on paths

This is done in order to help prevent us from loading the same
font face over and over again under separate keys.  We still incur
the performance hit of doing the fontconfig search each new glyph,
but that's unavoidable without more extensive refactoring.

1 files changed, 24 insertions, 14 deletions

diff --git a/font/src/ft/mod.rs b/font/src/ft/mod.rs
index d69aad9a..20dfd2ce 100644
--- a/font/src/ft/mod.rs
+++ b/font/src/ft/mod.rs
@@ -27,7 +27,7 @@ use super::{FontDesc, RasterizedGlyph, Metrics, Size, FontKey, GlyphKey, Weight,
 pub struct FreeTypeRasterizer {
     faces: HashMap<FontKey, Face<'static>>,
     library: Library,
-    keys: HashMap<FontDesc, FontKey>,
+    keys: HashMap<::std::path::PathBuf, FontKey>,
     dpi_x: u32,
     dpi_y: u32,
     dpr: f32,
@@ -75,15 +75,10 @@ impl ::Rasterize for FreeTypeRasterizer {
     }
 
     fn load_font(&mut self, desc: &FontDesc, _size: Size) -> Result<FontKey, Error> {
-        self.keys
-            .get(&desc.to_owned())
-            .map(|k| Ok(*k))
-            .unwrap_or_else(|| {
-                let face = self.get_face(desc)?;
-                let key = FontKey::next();
-                self.faces.insert(key, face);
-                Ok(key)
-            })
+        let face = self.get_face(desc)?;
+        let key = FontKey::next();
+        self.faces.insert(key, face);
+        Ok(key)
     }
 
     fn get_glyph(&mut self, glyph_key: &GlyphKey) -> Result<RasterizedGlyph, Error> {
@@ -246,11 +241,26 @@ impl FreeTypeRasterizer {
         match fc::font_match(config, &mut pattern) {
             Some(font) => {
                 if let (Some(path), Some(index)) = (font.file(0), font.index(0)) {
-                    let face = self.library.new_face(path, index)?;
-                    let key = FontKey::next();
-                    self.faces.insert(key, face);
-                    return Ok(key)
+                    match self.keys.get(&path.to_path_buf()) {
+                        // We've previously loaded this font, so don't
+                        // load it again.
+                        Some(&key) => {
+                            debug!("Hit for font {:?}", path);
+                            return Ok(key)
+                        },
+
+                        None => {
+                            debug!("Miss for font {:?}", path);
+                            let pathbuf = path.to_path_buf();
+                            let face = self.library.new_face(path, index)?;
+                            let key = FontKey::next();
+                            self.keys.insert(pathbuf, key);
+                            self.faces.insert(key, face);
+                            return Ok(key)
+                        }
+                    }
                 }
+
                 Err(Error::MissingFont(
                     FontDesc::new("fallback-without-path", Style::Specific(glyph.to_string()))
                 ))