Turn on strict memory safety for the macOS app

mac/Sources/Byre/Fonts.swift

@@ -1,4 +1,5 @@
 import CoreText
+import Synchronization
 import SwiftUI
 
 enum Fonts {
@@ -14,7 +15,7 @@ enum Fonts {
     }()
 
     private static func file(_ subset: String, _ italic: Bool, _ weight: CGFloat) -> CTFontDescriptor {
-        let d = descriptors["atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2"]!
+        let d = unsafe descriptors["atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2"]!
         return CTFontDescriptorCreateCopyWithVariation(d, 0x7767_6874 as CFNumber, weight)
     }
 
@@ -24,29 +25,25 @@ enum Fonts {
         return CTFontCreateWithFontDescriptor(d, size, nil)
     }
 
-    nonisolated(unsafe) private static var fonts: [String: (font: Font, ns: NSFont)] = [:]
-    private static let lock = NSLock()
+    private static let fonts = Mutex<[String: CTFont]>([:])
 
-    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> (font: Font, ns: NSFont) {
+    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> CTFont {
         let key = "\(size) \(weight) \(italic)"
-        lock.lock()
-        defer {
-            lock.unlock()
-        }
-        if let f = fonts[key] {
+        return fonts.withLock { fonts in
+            if let f = fonts[key] {
+                return f
+            }
+            let f = ct(size, weight: weight, italic: italic)
+            fonts[key] = f
             return f
         }
-        let c = ct(size, weight: weight, italic: italic)
-        let f = (Font(c), c as NSFont)
-        fonts[key] = f
-        return f
     }
 
     static func font(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> Font {
-        cached(size, weight, italic).font
+        Font(cached(size, weight, italic))
     }
 
     static func ns(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> NSFont {
-        cached(size, weight, italic).ns
+        cached(size, weight, italic) as NSFont
     }
 }