From 3fa347b87fe935a4e1a3fc728f87d3d25c6f8d52 Mon Sep 17 00:00:00 2001
From: Jordan Baird <jordanbaird.dev@gmail.com>
Date: Sun, 26 May 2024 03:16:35 -0600
Subject: [PATCH] Rework exclusivity lock

---
 .../ColorWellKit/Utilities/LockedState.swift  | 79 +++++++++++++++++++
 .../Views/Cocoa/CWColorWell.swift             | 27 +++----
 2 files changed, 90 insertions(+), 16 deletions(-)
 create mode 100644 Sources/ColorWellKit/Utilities/LockedState.swift

diff --git a/Sources/ColorWellKit/Utilities/LockedState.swift b/Sources/ColorWellKit/Utilities/LockedState.swift
new file mode 100644
index 0000000..a615583
--- /dev/null
+++ b/Sources/ColorWellKit/Utilities/LockedState.swift
@@ -0,0 +1,79 @@
+//
+//  LockedState.swift
+//  ColorWellKit
+//
+
+import os
+
+/// A locking wrapper around a state.
+///
+/// This implementation is heavily inspired by Foundation's `LockedState` type:
+/// https://github.com/apple/swift-foundation/blob/main/Sources/FoundationEssentials/LockedState.swift
+struct LockedState<State> {
+    private enum Lock {
+        typealias UnfairLock = os_unfair_lock
+
+        static func initialize(_ lock: UnsafeMutablePointer<UnfairLock>) {
+            lock.initialize(to: UnfairLock())
+        }
+
+        static func deinitialize(_ lock: UnsafeMutablePointer<UnfairLock>) {
+            lock.deinitialize(count: 1)
+        }
+
+        static func lock(_ lock: UnsafeMutablePointer<UnfairLock>) {
+            os_unfair_lock_lock(lock)
+        }
+
+        static func unlock(_ lock: UnsafeMutablePointer<UnfairLock>) {
+            os_unfair_lock_unlock(lock)
+        }
+    }
+
+    private class Buffer: ManagedBuffer<State, Lock.UnfairLock> {
+        deinit {
+            withUnsafeMutablePointerToElements { lock in
+                Lock.deinitialize(lock)
+            }
+        }
+    }
+
+    private let buffer: ManagedBuffer<State, Lock.UnfairLock>
+
+    var state: State {
+        buffer.withUnsafeMutablePointerToHeader { state in
+            state.pointee
+        }
+    }
+
+    init(initialState: State) {
+        self.buffer = Buffer.create(minimumCapacity: 1) { buffer in
+            buffer.withUnsafeMutablePointerToElements { lock in
+                Lock.initialize(lock)
+            }
+            return initialState
+        }
+    }
+
+    func withLock<T>(_ body: (inout State) throws -> T) rethrows -> T {
+        try buffer.withUnsafeMutablePointers { state, lock in
+            Lock.lock(lock)
+            defer {
+                Lock.unlock(lock)
+            }
+            return try body(&state.pointee)
+        }
+    }
+
+    func withLockExtendingLifetimeOfState<T>(_ body: (inout State) throws -> T) rethrows -> T {
+        try buffer.withUnsafeMutablePointers { state, lock in
+            Lock.lock(lock)
+            return try withExtendedLifetime(state.pointee) {
+                defer {
+                    Lock.unlock(lock)
+                }
+                return try body(&state.pointee)
+            }
+        }
+    }
+}
diff --git a/Sources/ColorWellKit/Views/Cocoa/CWColorWell.swift b/Sources/ColorWellKit/Views/Cocoa/CWColorWell.swift
index fe80154..d86e125 100644
--- a/Sources/ColorWellKit/Views/Cocoa/CWColorWell.swift
+++ b/Sources/ColorWellKit/Views/Cocoa/CWColorWell.swift
@@ -27,9 +27,7 @@ public class CWColorWell: _CWColorWellBaseControl {
 
     // MARK: Instance Properties
 
-    private let exclusivityLock = NSRecursiveLock()
-
-    private var isExclusive = true
+    private let exclusivity = LockedState(initialState: true)
 
     private var popover: NSPopover?
 
@@ -143,7 +141,7 @@ public class CWColorWell: _CWColorWellBaseControl {
                 }
             }
             if shouldActivate {
-                if isExclusive && allowsMultipleSelection {
+                if exclusivity.state && allowsMultipleSelection {
                     NSColorPanel.shared.enforceExclusivity(of: self)
                 }
                 NSColorPanel.shared.attach(self)
@@ -213,25 +211,22 @@ public class CWColorWell: _CWColorWellBaseControl {
     /// Until the color well is activated again, changes to the color panel will not
     /// affect the color well's state.
     public func deactivate() {
-        withExclusivityLock(isExclusive) { isActive = false }
+        withExclusivityLock(exclusivity.state) { isActive = false }
     }
 
     // MARK: Private/Internal Instance Methods
 
     /// Performs the given closure while locking the exclusivity of the color well
     /// to the given state in a thread-safe manner.
-    private func withExclusivityLock<T>(
-        _ isExclusive: @autoclosure () -> Bool,
-        body: () throws -> T
-    ) rethrows -> T {
-        exclusivityLock.lock()
-        let cachedIsExclusive = self.isExclusive
-        self.isExclusive = isExclusive()
-        defer {
-            self.isExclusive = cachedIsExclusive
-            exclusivityLock.unlock()
+    private func withExclusivityLock<T>(_ isExclusive: Bool, body: () throws -> T) rethrows -> T {
+        try exclusivity.withLock { state in
+            let cachedState = state
+            state = isExclusive
+            defer {
+                state = cachedState
+            }
+            return try body()
         }
-        return try body()
     }
 
     @objc(deactivate) // exposed to Objective-C as `deactivate`