Compiles with strict concurrency checking

Tusker/Extensions/MainActor+Unsafe.swift

@@ -56,4 +56,13 @@ public extension MainActor {
         return try withoutActuallyEscaping(body) { fn in
             try unsafeBitCast(fn, to: (() throws -> T).self)()
         }
-    }}
+    }
+    
+    @_unavailableFromAsync
+    @available(*, deprecated, message: "Tool of last resort, do not use this.")
+    static func runUnsafelyMaybeIntroducingDataRace<T>(_ body: @MainActor () throws -> T) rethrows -> T {
+        return try withoutActuallyEscaping(body) { fn in
+            try unsafeBitCast(fn, to: (() throws -> T).self)()
+        }
+    }
+}

Tusker/ImageGrayscalifier.swift

@@ -15,7 +15,10 @@ struct ImageGrayscalifier {
     private static let cache = NSCache<NSURL, UIImage>()
 
     static func convertIfNecessary(url: URL?, image: UIImage) -> UIImage? {
-        if Preferences.shared.grayscaleImages,
+        let grayscale = MainActor.runUnsafelyMaybeIntroducingDataRace {
+            Preferences.shared.grayscaleImages
+        }
+        if grayscale,
            let source = image.cgImage {
             // todo: should this return the original image if conversion fails?
             return convert(url: url, cgImage: source)
@@ -35,6 +38,21 @@ struct ImageGrayscalifier {
         return doConvert(CIImage(cgImage: cgImage), url: url)
     }
     
+    static func convert(url: URL?, image: UIImage) async -> UIImage? {
+        if let url,
+           let cached = cache.object(forKey: url as NSURL) {
+            return cached
+        }
+        guard let cgImage = image.cgImage else {
+            return nil
+        }
+        return await withCheckedContinuation { continuation in
+            queue.async {
+                continuation.resume(returning: doConvert(CIImage(cgImage: cgImage), url: url))
+            }
+        }
+    }
+    
     static func convert(url: URL?, data: Data) -> UIImage? {
         if let url = url,
            let cached = cache.object(forKey: url as NSURL) {
@@ -56,6 +74,18 @@ struct ImageGrayscalifier {
         return doConvert(CIImage(cgImage: cgImage), url: url)
     }
     
+    static func convert(url: URL?, cgImage: CGImage) async -> UIImage? {
+        if let url = url,
+           let cached = cache.object(forKey: url as NSURL) {
+            return cached
+        }
+        return await withCheckedContinuation { continuation in
+            queue.async {
+                continuation.resume(returning: doConvert(CIImage(cgImage: cgImage), url: url))
+            }
+        }
+    }
+    
     private static func doConvert(_ source: CIImage, url: URL?) -> UIImage? {
         guard let filter = CIFilter(name: "CIColorMonochrome") else {
             return nil

Tusker/Screens/Preferences/About/AboutView.swift

@@ -9,6 +9,7 @@
 import SwiftUI
 import MessageUI
 
+@MainActor
 struct AboutView: View {
     @State private var logData: Data?
     @State private var isGettingLogData = false

Tusker/Views/Attachments/AttachmentView.swift

@@ -30,7 +30,7 @@ class AttachmentView: GIFImageView {
     var attachment: Attachment!
     var index: Int!
     
-    private var attachmentRequest: ImageCache.Request?
+    private var loadAttachmentTask: Task<Void, Never>?
     private var source: Source?
     
     private var autoplayGifs: Bool {
@@ -45,11 +45,13 @@ class AttachmentView: GIFImageView {
         
         self.attachment = attachment
         self.index = index
-        loadAttachment()
+        self.loadAttachmentTask = Task {
+            await self.loadAttachment()
+        }
     }
     
     deinit {
-        attachmentRequest?.cancel()
+        loadAttachmentTask?.cancel()
     }
     
     required init?(coder aDecoder: NSCoder) {
@@ -76,7 +78,9 @@ class AttachmentView: GIFImageView {
         gifPlaybackModeChanged()
         
         if isGrayscale != Preferences.shared.grayscaleImages {
-            self.displayImage()
+            Task {
+                await displayImage()
+            }
         }
         
         if getBadges().isEmpty != Preferences.shared.showAttachmentBadges {
@@ -107,34 +111,34 @@ class AttachmentView: GIFImageView {
         }
     }
     
-    func loadAttachment() {
+    private func loadAttachment() async {
+        let blurHashTask: Task<Void, any Error>?
         if let hash = attachment.blurHash {
-            AttachmentView.queue.async { [weak self] in
-                guard let self = self else { return }
-                
+            blurHashTask = Task {
                 guard var preview = UIImage(blurHash: hash, size: self.blurHashSize()) else {
                     return
                 }
+                try Task.checkCancellation()
                 
                 if Preferences.shared.grayscaleImages,
                    let grayscale = ImageGrayscalifier.convert(url: nil, cgImage: preview.cgImage!) {
                     preview = grayscale
                 }
+                try Task.checkCancellation()
                 
-                DispatchQueue.main.async { [weak self] in
-                    guard let self = self, self.image == nil else { return }
                 self.image = preview
             }
-            }
+        } else {
+            blurHashTask = nil
         }
         
         createBadgesView(getBadges())
         
         switch attachment.kind {
         case .image:
-            loadImage()
+            await loadImage()
         case .video:
-            loadVideo()
+            await loadVideo()
         case .audio:
             loadAudio()
         case .gifv:
@@ -142,6 +146,8 @@ class AttachmentView: GIFImageView {
         case .unknown:
             createUnknownLabel()
         }
+        
+        blurHashTask?.cancel()
     }
     
     private func getBadges() -> Badges {
@@ -182,66 +188,27 @@ class AttachmentView: GIFImageView {
         }
     }
     
-    func loadImage() {
-        let attachmentURL = attachment.url
-        attachmentRequest = ImageCache.attachments.get(attachmentURL) { [weak self] (data, image) in
-            guard let self = self,
-                  self.attachment.url == attachmentURL else {
-                return
-            }
+    private func loadImage() async {
+        let (data, image) = await ImageCache.attachments.get(attachment.url)
+        guard !Task.isCancelled else { return }
         
-            DispatchQueue.main.async {
-                self.attachmentRequest = nil
-                
-                if attachmentURL.pathExtension == "gif",
+        if attachment.url.pathExtension == "gif",
            let data {
-                    self.source = .gifData(attachmentURL, data, image)
-                    if self.autoplayGifs {
+            source = .gifData(attachment.url, data, image)
+            if autoplayGifs {
                 let controller = GIFController(gifData: data)
                 controller.attach(to: self)
                 controller.startAnimating()
             } else {
-                        self.displayImage()
+                await displayImage()
             }
         } else if let image {
-                    self.source = .image(attachmentURL, image)
-                    self.displayImage()
-                }
-            }
-        }
-    }
-    
-    func loadVideo() {
-        if let previewURL = self.attachment.previewURL {
-            attachmentRequest = ImageCache.attachments.get(previewURL, completion: { [weak self] (_, image) in
-                guard let self, let image else { return }
-                DispatchQueue.main.async {
-                    self.attachmentRequest = nil
-                    self.source = .image(previewURL, image)
-                    self.displayImage()
-                }
-            })
-        } else {
-            let attachmentURL = self.attachment.url
-            AttachmentView.queue.async { [weak self] in
-                let asset = AVURLAsset(url: attachmentURL)
-                let generator = AVAssetImageGenerator(asset: asset)
-                generator.appliesPreferredTrackTransform = true
-                #if os(visionOS)
-                #warning("Use async AVAssetImageGenerator.image(at:)")
-                #else
-                guard let image = try? generator.copyCGImage(at: .zero, actualTime: nil) else { return }
-                UIImage(cgImage: image).prepareForDisplay { [weak self] image in
-                    DispatchQueue.main.async { [weak self] in
-                        guard let self, let image else { return }
-                        self.source = .image(attachmentURL, image)
-                        self.displayImage()
-                    }
-                }
-                #endif
+            source = .image(attachment.url, image)
+            await displayImage()
         }
     }
     
+    private func loadVideo() async {
         let playImageView = UIImageView(image: UIImage(systemName: "play.circle.fill"))
         playImageView.translatesAutoresizingMaskIntoConstraints = false
         addSubview(playImageView)
@@ -251,9 +218,40 @@ class AttachmentView: GIFImageView {
             playImageView.centerXAnchor.constraint(equalTo: centerXAnchor),
             playImageView.centerYAnchor.constraint(equalTo: centerYAnchor),
         ])
+        
+        if let previewURL = attachment.previewURL {
+            guard let image = await ImageCache.attachments.get(previewURL).1,
+                  !Task.isCancelled else {
+                return
             }
             
-    func loadAudio() {
+            source = .image(previewURL, image)
+            await displayImage()
+        } else {
+            let asset = AVURLAsset(url: attachment.url)
+            let generator = AVAssetImageGenerator(asset: asset)
+            generator.appliesPreferredTrackTransform = true
+            let image: CGImage?
+            #if os(visionOS)
+            image = try? await generator.image(at: .zero).image
+            #else
+            if #available(iOS 16.0, *) {
+                image = try? await generator.image(at: .zero).image
+            } else {
+                image = try? generator.copyCGImage(at: .zero, actualTime: nil)
+            }
+            #endif
+            guard let image,
+                  let prepared = await UIImage(cgImage: image).byPreparingForDisplay(),
+                  !Task.isCancelled else {
+                return
+            }
+            source = .image(attachment.url, prepared)
+            await displayImage()
+        }
+    }
+    
+    private func loadAudio() {
         let label = UILabel()
         label.text = "Audio Only"
         let playImageView = UIImageView(image: UIImage(systemName: "play.circle.fill"))
@@ -274,23 +272,8 @@ class AttachmentView: GIFImageView {
         ])
     }
     
-    func loadGifv() {
-        let attachmentURL = self.attachment.url
-        let asset = AVURLAsset(url: attachmentURL)
-        AttachmentView.queue.async {
-            let generator = AVAssetImageGenerator(asset: asset)
-            generator.appliesPreferredTrackTransform = true
-            #if os(visionOS)
-            #warning("Use async AVAssetImageGenerator.image(at:)")
-            #else
-            guard let image = try? generator.copyCGImage(at: .zero, actualTime: nil) else { return }
-            DispatchQueue.main.async {
-                self.source = .cgImage(attachmentURL, image)
-                self.displayImage()
-            }
-            #endif
-        }
-        
+    private func loadGifv() {
+        let asset = AVURLAsset(url: attachment.url)
         let gifvView = GifvAttachmentView(asset: asset, gravity: .resizeAspectFill)
         self.gifvView = gifvView
         gifvView.translatesAutoresizingMaskIntoConstraints = false
@@ -306,7 +289,7 @@ class AttachmentView: GIFImageView {
         ])
     }
     
-    func createUnknownLabel() {
+    private func createUnknownLabel() {
         backgroundColor = .appSecondaryBackground
         let label = UILabel()
         label.text = "Unknown Attachment Type"
@@ -325,8 +308,7 @@ class AttachmentView: GIFImageView {
         ])
     }
     
-    @MainActor
-    private func displayImage() {
+    private func displayImage() async {
         isGrayscale = Preferences.shared.grayscaleImages
         
         switch source {
@@ -335,12 +317,7 @@ class AttachmentView: GIFImageView {
             
         case let .image(url, sourceImage):
             if isGrayscale {
-                ImageGrayscalifier.queue.async { [weak self] in
-                    let grayscale = ImageGrayscalifier.convert(url: url, image: sourceImage)
-                    DispatchQueue.main.async { [weak self] in
-                        self?.image = grayscale
-                    }
-                }
+                self.image = await ImageGrayscalifier.convert(url: url, image: sourceImage)
             } else {
                 self.image = sourceImage
             }
@@ -348,26 +325,16 @@ class AttachmentView: GIFImageView {
         case let .gifData(url, _, sourceImage):
             if isGrayscale,
                let sourceImage {
-                ImageGrayscalifier.queue.async { [weak self] in
-                    let grayscale = ImageGrayscalifier.convert(url: url, image: sourceImage)
-                    DispatchQueue.main.async { [weak self] in
-                        self?.image = grayscale
-                    }
-                }
+                self.image = await ImageGrayscalifier.convert(url: url, image: sourceImage)
             } else {
                 self.image = sourceImage
             }
             
         case let .cgImage(url, cgImage):
             if isGrayscale {
-                ImageGrayscalifier.queue.async { [weak self] in
-                    let grayscale = ImageGrayscalifier.convert(url: url, cgImage: cgImage)
-                    DispatchQueue.main.async { [weak self] in
-                        self?.image = grayscale
-                    }
-                }
+                self.image = await ImageGrayscalifier.convert(url: url, cgImage: cgImage)
             } else {
-                image = UIImage(cgImage: cgImage)
+                self.image = UIImage(cgImage: cgImage)
             }
         }
     }