Make FontSystem not self-referencing

src/font/mod.rs

@@ -4,12 +4,17 @@ use core::ops::Deref;
 
 pub(crate) mod fallback;
 
-pub use self::matches::*;
-mod matches;
-
 pub use self::system::*;
 mod system;
 
+#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+/// Identifies a [`Font`] in a [`FontSystem`]
+pub struct FontKey {
+    pub id: fontdb::ID,
+    #[cfg(feature = "swash")]
+    pub swash: (u32, swash::CacheKey),
+}
+
 /// A font
 pub struct Font<'a> {
     pub info: &'a fontdb::FaceInfo,
@@ -44,6 +49,36 @@ impl<'a> Font<'a> {
         })
     }
 
+    pub fn from_key(db: &'a fontdb::Database, key: FontKey) -> Option<Self> {
+        let info = db.face(key.id)?;
+        let data = match &info.source {
+            fontdb::Source::Binary(data) => data.deref().as_ref(),
+            #[cfg(feature = "std")]
+            fontdb::Source::File(path) => {
+                log::warn!("Unsupported fontdb Source::File('{}')", path.display());
+                return None;
+            }
+            #[cfg(feature = "std")]
+            fontdb::Source::SharedFile(_path, data) => data.deref().as_ref(),
+        };
+
+        Some(Self {
+            info,
+            data,
+            rustybuzz: rustybuzz::Face::from_slice(data, info.index)?,
+            #[cfg(feature = "swash")]
+            swash: key.swash,
+        })
+    }
+
+    pub fn key(&self) -> FontKey {
+        FontKey {
+            id: self.info.id,
+            #[cfg(feature = "swash")]
+            swash: self.swash,
+        }
+    }
+
     #[cfg(feature = "swash")]
     pub fn as_swash(&self) -> swash::FontRef {
         swash::FontRef {