Add font infrastructure

Sources/SwiftUIMath/Internal/Font/FontRegistry.swift

@@ -0,0 +1,114 @@
+@preconcurrency import CoreGraphics
+@preconcurrency import CoreText
+import Foundation
+
+extension Math {
+  final class FontRegistry: Sendable {
+    static let shared = FontRegistry()
+
+    private struct Cache {
+      var graphicsFonts: [Font.Name: CGFont] = [:]
+      var tables: [Font.Name: Table] = [:]
+      let fonts = NSCache<KeyBox<Font>, CTFont>()
+    }
+
+    private let cache = ReadWriteLockIsolated<Cache>(Cache())
+
+    func graphicsFont(named name: Font.Name) -> CGFont? {
+      cache.withValue { cache in
+        if let graphicsFont = cache.graphicsFonts[name] {
+          return graphicsFont
+        }
+
+        guard let (graphicsFont, _) = registerGraphicsFont(named: name, cache: &cache) else {
+          return nil
+        }
+
+        return graphicsFont
+      }
+    }
+
+    func table(named name: Font.Name) -> Table? {
+      cache.withValue { cache in
+        if let table = cache.tables[name] {
+          return table
+        }
+
+        guard let (_, table) = registerGraphicsFont(named: name, cache: &cache) else {
+          return nil
+        }
+
+        return table
+      }
+    }
+
+    func font(named name: Font.Name, size: CGFloat) -> CTFont? {
+      cache.withValue { cache in
+        let key = KeyBox(Font(name: name, size: size))
+
+        if let font = cache.fonts.object(forKey: key) {
+          return font
+        }
+
+        guard
+          let graphicsFont = cache.graphicsFonts[name]
+            ?? registerGraphicsFont(named: name, cache: &cache)?.0
+        else {
+          return nil
+        }
+
+        let font = CTFontCreateWithGraphicsFont(graphicsFont, size, nil, nil)
+        cache.fonts.setObject(font, forKey: key)
+
+        return font
+      }
+    }
+
+    private func registerGraphicsFont(
+      named name: Font.Name,
+      cache: inout Cache
+    ) -> (CGFont, Table)? {
+      guard let graphicsFont = CGFont.named(name), let table = Table.named(name) else {
+        return nil
+      }
+
+      guard CTFontManagerRegisterGraphicsFont(graphicsFont, nil) else {
+        return nil
+      }
+
+      cache.graphicsFonts[name] = graphicsFont
+      cache.tables[name] = table
+
+      return (graphicsFont, table)
+    }
+  }
+}
+
+extension CGFont {
+  fileprivate static func named(_ name: Math.Font.Name) -> CGFont? {
+    guard
+      let bundleURL = Bundle.module.url(forResource: "mathFonts", withExtension: "bundle"),
+      let url = Bundle(url: bundleURL)?.url(forResource: name.rawValue, withExtension: "otf"),
+      let data = try? Data(contentsOf: url),
+      let dataProvider = CGDataProvider(data: data as CFData)
+    else {
+      return nil
+    }
+
+    return CGFont(dataProvider)
+  }
+}
+
+extension Math.Table {
+  fileprivate static func named(_ name: Math.Font.Name) -> Math.Table? {
+    guard
+      let bundleURL = Bundle.module.url(forResource: "mathFonts", withExtension: "bundle"),
+      let url = Bundle(url: bundleURL)?.url(forResource: name.rawValue, withExtension: "plist"),
+      let data = try? Data(contentsOf: url)
+    else {
+      return nil
+    }
+
+    return try? PropertyListDecoder().decode(Math.Table.self, from: data)
+  }
+}