Refactors UICollectionViewControllers/UITableViewControllers to use prefetching RSTCellContentDataSources

Delta/Components/Loading/LoadImageURLOperation.swift

@@ -45,6 +45,11 @@ class LoadImageURLOperation: RSTLoadOperation<UIImage, NSURL>
         super.cancel()
         
         self.downloadOperation?.cancel()
+        
+        if self.isAsynchronous
+        {
+            self.finish()
+        }
     }
     
     override func loadResult(completion: @escaping (UIImage?, Swift.Error?) -> Void)

Delta/Database/OpenVGDB/GamesDatabaseBrowserViewController.swift

@@ -16,10 +16,8 @@ class GamesDatabaseBrowserViewController: UITableViewController
     var selectionHandler: ((GameMetadata) -> Void)?
     
     fileprivate let database: GamesDatabase?
-    fileprivate let dataSource: RSTArrayTableViewDataSource<GameMetadata>
     
-    fileprivate let operationQueue = RSTOperationQueue()
+    fileprivate let dataSource: RSTArrayTableViewPrefetchingDataSource<GameMetadata, UIImage>
-    fileprivate let imageCache = NSCache<NSURL, UIImage>()
     
     override init(style: UITableViewStyle) {
         fatalError()
@@ -37,39 +35,13 @@ class GamesDatabaseBrowserViewController: UITableViewController
             print(error)
         }
         
-        self.dataSource = RSTArrayTableViewDataSource<GameMetadata>(items: [])
+        self.dataSource = RSTArrayTableViewPrefetchingDataSource<GameMetadata, UIImage>(items: [])
-        
-        let placeholderView = RSTPlaceholderView()
-        placeholderView.textLabel.textColor = UIColor.lightText
-        placeholderView.detailTextLabel.textColor = UIColor.lightText
-        
-        self.dataSource.placeholderView = placeholderView
         
         super.init(coder: aDecoder)
         
-        self.dataSource.cellConfigurationHandler = { (cell, metadata, indexPath) in
-            self.configure(cell: cell as! GameMetadataTableViewCell, with: metadata, for: indexPath)
-        }
-        
-        if let database = self.database
-        {
-            self.dataSource.searchController.searchHandler = { [unowned database, unowned dataSource] (searchValue, previousSearchValue) in
-                
-                return RSTBlockOperation(executionBlock: { [unowned database, unowned dataSource] (operation) in
-                    let results = database.metadataResults(forGameName: searchValue.text)
-                    
-                    guard !operation.isCancelled else { return }
-                    
-                    dataSource.items = results
-                    
-                    rst_dispatch_sync_on_main_thread {
-                        self.updatePlaceholderView()
-                    }
-                })
-            }
-        }
-        
         self.definesPresentationContext = true
+        
+        self.prepareDataSource()
     }
     
     override var preferredStatusBarStyle: UIStatusBarStyle {
@@ -83,6 +55,8 @@ class GamesDatabaseBrowserViewController: UITableViewController
         self.view.backgroundColor = UIColor.deltaDarkGray
         
         self.tableView.dataSource = self.dataSource
+        self.tableView.prefetchDataSource = self.dataSource
+        
         self.tableView.indicatorStyle = .white
         self.tableView.separatorColor = UIColor.gray
         
@@ -99,7 +73,73 @@ class GamesDatabaseBrowserViewController: UITableViewController
     }
 }
 
-extension GamesDatabaseBrowserViewController
+private extension GamesDatabaseBrowserViewController
+{
+    func prepareDataSource()
+    {
+        /* Placeholder View */
+        let placeholderView = RSTPlaceholderView()
+        placeholderView.textLabel.textColor = UIColor.lightText
+        placeholderView.detailTextLabel.textColor = UIColor.lightText
+        self.dataSource.placeholderView = placeholderView
+        
+        
+        /* Cell Configuration */
+        self.dataSource.cellConfigurationHandler = { [unowned self] (cell, metadata, indexPath) in
+            self.configure(cell: cell as! GameMetadataTableViewCell, with: metadata, for: indexPath)
+        }
+        
+        
+        /* Prefetching */
+        self.dataSource.prefetchHandler = { (metadata, indexPath, completionHandler) in
+            guard let artworkURL = metadata.artworkURL else { return nil }
+            
+            let operation = LoadImageURLOperation(url: artworkURL)
+            operation.resultHandler = { (image, error) in
+                completionHandler(image, error)
+            }
+            return operation
+        }
+
+        self.dataSource.prefetchCompletionHandler = { (cell, image, indexPath, error) in
+            guard let image = image else { return }
+            
+            let cell = cell as! GameMetadataTableViewCell
+            
+            let artworkDisplaySize = AVMakeRect(aspectRatio: image.size, insideRect: cell.artworkImageView.bounds)
+            let offset = (cell.artworkImageView.bounds.width - artworkDisplaySize.width) / 2
+            
+            // Offset artworkImageViewLeadingConstraint and artworkImageViewTrailingConstraint to right-align artworkImageView
+            cell.artworkImageViewLeadingConstraint.constant += offset
+            cell.artworkImageViewTrailingConstraint.constant -= offset
+            
+            cell.artworkImageView.image = image
+            cell.artworkImageView.superview?.layoutIfNeeded()
+        }
+        
+        
+        /* Searching */
+        if let database = self.database
+        {
+            self.dataSource.searchController.searchHandler = { [unowned self, unowned database] (searchValue, previousSearchValue) in
+                return RSTBlockOperation() { [unowned self, unowned database] (operation) in
+                    let results = database.metadataResults(forGameName: searchValue.text)
+                    
+                    guard !operation.isCancelled else { return }
+                    
+                    self.dataSource.items = results
+                    
+                    rst_dispatch_sync_on_main_thread {
+                        self.resetTableViewContentOffset()
+                        self.updatePlaceholderView()
+                    }
+                }
+            }
+        }
+    }
+}
+
+private extension GamesDatabaseBrowserViewController
 {
     func configure(cell: GameMetadataTableViewCell, with metadata: GameMetadata, for indexPath: IndexPath)
     {
@@ -112,30 +152,6 @@ extension GamesDatabaseBrowserViewController
         cell.artworkImageViewTrailingConstraint.constant = 15
         
         cell.separatorInset.left = cell.nameLabel.frame.minX
-        
-        if let artworkURL = metadata.artworkURL
-        {
-            let operation = LoadImageURLOperation(url: artworkURL)
-            operation.resultsCache = self.imageCache
-            operation.resultHandler = { (image, error) in
-                if let image = image
-                {
-                    let artworkDisplaySize = AVMakeRect(aspectRatio: image.size, insideRect: cell.artworkImageView.bounds)
-                    let offset = (cell.artworkImageView.bounds.width - artworkDisplaySize.width) / 2
-                    
-                    DispatchQueue.main.async {
-                        // Offset artworkImageViewLeadingConstraint and artworkImageViewTrailingConstraint to right-align artworkImageView
-                        cell.artworkImageViewLeadingConstraint.constant += offset
-                        cell.artworkImageViewTrailingConstraint.constant -= offset
-                        
-                        cell.artworkImageView.image = image
-                        cell.artworkImageView.superview?.layoutIfNeeded()
-                    }
-                }
-            }
-            
-            self.operationQueue.addOperation(operation, forKey: indexPath as NSIndexPath)
-        }
     }
     
     func updatePlaceholderView()
@@ -153,6 +169,12 @@ extension GamesDatabaseBrowserViewController
             placeholderView.detailTextLabel.text = NSLocalizedString("Please make sure the name is correct, or try searching for another game.", comment: "")
         }
     }
+    
+    func resetTableViewContentOffset()
+    {
+        self.tableView.setContentOffset(CGPoint.zero, animated: false)
+        self.tableView.setContentOffset(CGPoint(x: 0, y: -self.topLayoutGuide.length), animated: false)
+    }
 }
 
 extension GamesDatabaseBrowserViewController
@@ -167,12 +189,6 @@ extension GamesDatabaseBrowserViewController
         let metadata = self.dataSource.item(at: indexPath)
         self.selectionHandler?(metadata)
     }
-    
-    override func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath)
-    {
-        let operation = self.operationQueue[indexPath as NSIndexPath]
-        operation?.cancel()
-    }
 }
 
 extension GamesDatabaseBrowserViewController: UISearchControllerDelegate
@@ -193,7 +209,6 @@ extension GamesDatabaseBrowserViewController: UISearchControllerDelegate
     func didDismissSearchController(_ searchController: UISearchController)
     {
         // Fix potentially incorrect offset if user dismisses searchController while scrolling
-        self.tableView.setContentOffset(CGPoint.zero, animated: false)
+        self.resetTableViewContentOffset()
-        self.tableView.setContentOffset(CGPoint(x: 0, y: -self.topLayoutGuide.length), animated: false)
     }
 }

Delta/Game Selection/GameCollectionViewController.swift

@@ -45,17 +45,23 @@ class GameCollectionViewController: UICollectionViewController
     
     fileprivate var activeSaveState: SaveStateProtocol?
     
-    fileprivate let dataSource = RSTFetchedResultsCollectionViewDataSource<Game>(fetchedResultsController: NSFetchedResultsController())
+    fileprivate let dataSource: RSTFetchedResultsCollectionViewPrefetchingDataSource<Game, UIImage>
     fileprivate let prototypeCell = GridCollectionViewCell()
     
-    fileprivate let imageOperationQueue = RSTOperationQueue()
-    fileprivate let imageCache = NSCache<NSURL, UIImage>()
-    
     fileprivate var _performing3DTouchTransition = false
     fileprivate weak var _destination3DTouchTransitionViewController: UIViewController?
     
     fileprivate var _renameAction: UIAlertAction?
     fileprivate var _changingArtworkGame: Game?
+    
+    required init?(coder aDecoder: NSCoder)
+    {
+        self.dataSource = RSTFetchedResultsCollectionViewPrefetchingDataSource<Game, UIImage>(fetchedResultsController: NSFetchedResultsController())
+
+        super.init(coder: aDecoder)
+        
+        self.prepareDataSource()
+    }
 }
 
 //MARK: - UIViewController -
@@ -66,11 +72,8 @@ extension GameCollectionViewController
     {
         super.viewDidLoad()
         
-        self.dataSource.cellConfigurationHandler = { [unowned self] (cell, item, indexPath) in
-            self.configure(cell as! GridCollectionViewCell, for: indexPath)
-        }
-        
         self.collectionView?.dataSource = self.dataSource
+        self.collectionView?.prefetchDataSource = self.dataSource
         self.collectionView?.delegate = self
         
         let layout = self.collectionViewLayout as! GridCollectionViewLayout
@@ -182,7 +185,33 @@ extension GameCollectionViewController
 //MARK: - Private Methods -
 private extension GameCollectionViewController
 {
-    //MARK: - Update
+    //MARK: - Data Source
+    func prepareDataSource()
+    {
+        self.dataSource.cellConfigurationHandler = { [unowned self] (cell, item, indexPath) in
+            self.configure(cell as! GridCollectionViewCell, for: indexPath)
+        }
+        
+        self.dataSource.prefetchHandler = { (game, indexPath, completionHandler) in
+            guard let artworkURL = game.artworkURL else { return nil }
+            
+            let imageOperation = LoadImageURLOperation(url: artworkURL)
+            imageOperation.resultHandler = { (image, error) in
+                completionHandler(image, error)
+            }
+            
+            return imageOperation
+        }
+        
+        self.dataSource.prefetchCompletionHandler = { (cell, image, indexPath, error) in
+            guard let image = image else { return }
+            
+            let cell = cell as! GridCollectionViewCell
+            cell.imageView.image = image
+            cell.isImageViewVibrancyEnabled = false
+        }
+    }
+    
     func updateDataSource()
     {
         let fetchRequest: NSFetchRequest<Game> = Game.fetchRequest()
@@ -194,7 +223,7 @@ private extension GameCollectionViewController
     }
     
     //MARK: - Configure Cells
-    func configure(_ cell: GridCollectionViewCell, for indexPath: IndexPath, ignoreImageOperations: Bool = false)
+    func configure(_ cell: GridCollectionViewCell, for indexPath: IndexPath)
     {
         let game = self.dataSource.item(at: indexPath)
         
@@ -214,24 +243,6 @@ private extension GameCollectionViewController
         cell.maximumImageSize = CGSize(width: 90, height: 90)
         cell.textLabel.text = game.name
         cell.textLabel.textColor = UIColor.gray
-                
-        if let artworkURL = game.artworkURL, !ignoreImageOperations
-        {
-            let imageOperation = LoadImageURLOperation(url: artworkURL)
-            imageOperation.resultsCache = self.imageCache
-            imageOperation.resultHandler = { (image, error) in
-                
-                if let image = image
-                {
-                    DispatchQueue.main.async {
-                        cell.imageView.image = image
-                        cell.isImageViewVibrancyEnabled = false
-                    }
-                }
-            }
-            
-            self.imageOperationQueue.addOperation(imageOperation, forKey: indexPath as NSCopying)
-        }
     }
     
     //MARK: - Emulation
@@ -533,12 +544,9 @@ extension GameCollectionViewController: ImportControllerDelegate
         
         if let imageURL = imageURL
         {
-            if let previousArtworkURL = game.artworkURL as NSURL?
+            // Remove previous artwork from cache.
-            {
+            self.dataSource.prefetchItemCache.removeObject(forKey: game)
-                // Remove previous artwork from cache.
+            
-                self.imageCache.removeObject(forKey: previousArtworkURL)
-            }
-                        
             DatabaseManager.shared.performBackgroundTask { (context) in
                 let temporaryGame = context.object(with: game.objectID) as! Game
                 temporaryGame.artworkURL = imageURL
@@ -626,12 +634,6 @@ extension GameCollectionViewController
             self.launchGame(withSender: cell, clearScreen: true)
         }
     }
-    
-    override func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath)
-    {
-        let operation = self.imageOperationQueue[indexPath as NSCopying]
-        operation?.cancel()
-    }
 }
 
 //MARK: - UICollectionViewDelegateFlowLayout -
@@ -646,7 +648,7 @@ extension GameCollectionViewController: UICollectionViewDelegateFlowLayout
         widthConstraint.isActive = true
         defer { widthConstraint.isActive = false }
         
-        self.configure(self.prototypeCell, for: indexPath, ignoreImageOperations: true)
+        self.configure(self.prototypeCell, for: indexPath)
         
         let size = self.prototypeCell.contentView.systemLayoutSizeFitting(UILayoutFittingCompressedSize)
         return size

Delta/Pause Menu/Save States/SaveStatesViewController.swift

@@ -65,10 +65,7 @@ class SaveStatesViewController: UICollectionViewController
     fileprivate var prototypeCellWidthConstraint: NSLayoutConstraint!
     fileprivate var prototypeHeader = SaveStatesCollectionHeaderView()
     
-    fileprivate let dataSource = RSTFetchedResultsCollectionViewDataSource<SaveState>(fetchedResultsController: NSFetchedResultsController())
+    fileprivate let dataSource: RSTFetchedResultsCollectionViewPrefetchingDataSource<SaveState, UIImage>
-    
-    fileprivate let imageOperationQueue = RSTOperationQueue()
-    fileprivate let imageCache = NSCache<NSURL, UIImage>()
     
     fileprivate var emulatorCoreSaveState: SaveStateProtocol?
     
@@ -76,11 +73,15 @@ class SaveStatesViewController: UICollectionViewController
     
     required init?(coder aDecoder: NSCoder)
     {
+        self.dataSource = RSTFetchedResultsCollectionViewPrefetchingDataSource<SaveState, UIImage>(fetchedResultsController: NSFetchedResultsController())
+        
         self.dateFormatter = DateFormatter()
         self.dateFormatter.timeStyle = .short
         self.dateFormatter.dateStyle = .short
         
         super.init(coder: aDecoder)
+        
+        self.prepareDataSource()
     }
 }
 
@@ -90,21 +91,8 @@ extension SaveStatesViewController
     {
         super.viewDidLoad()
         
-        self.vibrancyView = UIVisualEffectView(effect: nil)
-        
-        self.placeholderView = RSTPlaceholderView(frame: CGRect(x: 0, y: 0, width: self.vibrancyView.bounds.width, height: self.vibrancyView.bounds.height))
-        self.placeholderView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
-        self.placeholderView.textLabel.text = NSLocalizedString("No Save States", comment: "")
-        self.placeholderView.textLabel.textColor = UIColor.white
-        self.placeholderView.detailTextLabel.textColor = UIColor.white
-        self.vibrancyView.contentView.addSubview(self.placeholderView)
-        
-        self.dataSource.proxy = self
-        self.dataSource.placeholderView = self.vibrancyView
-        self.dataSource.cellConfigurationHandler = { [unowned self] (cell, item, indexPath) in
-            self.configure(cell as! GridCollectionViewCell, for: indexPath)
-        }
         self.collectionView?.dataSource = self.dataSource
+        self.collectionView?.prefetchDataSource = self.dataSource
         
         let collectionViewLayout = self.collectionViewLayout as! GridCollectionViewLayout
         let averageHorizontalInset = (collectionViewLayout.sectionInset.left + collectionViewLayout.sectionInset.right) / 2
@@ -118,11 +106,11 @@ extension SaveStatesViewController
         {
         case .saving:
             self.title = NSLocalizedString("Save State", comment: "")
-            placeholderView.detailTextLabel.text = NSLocalizedString("You can create a new save state by pressing the + button in the top right.", comment: "")
+            self.placeholderView.detailTextLabel.text = NSLocalizedString("You can create a new save state by pressing the + button in the top right.", comment: "")
             
         case .loading:
             self.title = NSLocalizedString("Load State", comment: "")
-            placeholderView.detailTextLabel.text = NSLocalizedString("You can create a new save state by pressing the Save State option in the pause menu.", comment: "")
+            self.placeholderView.detailTextLabel.text = NSLocalizedString("You can create a new save state by pressing the Save State option in the pause menu.", comment: "")
             self.navigationItem.rightBarButtonItem = nil
         }
         
@@ -156,10 +144,57 @@ extension SaveStatesViewController
     }
 }
 
+private extension SaveStatesViewController
+{
+    func prepareDataSource()
+    {
+        self.dataSource.proxy = self
+        
+        self.vibrancyView = UIVisualEffectView(effect: nil)
+        
+        self.placeholderView = RSTPlaceholderView(frame: CGRect(x: 0, y: 0, width: self.vibrancyView.bounds.width, height: self.vibrancyView.bounds.height))
+        self.placeholderView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+        self.placeholderView.textLabel.text = NSLocalizedString("No Save States", comment: "")
+        self.placeholderView.textLabel.textColor = UIColor.white
+        self.placeholderView.detailTextLabel.textColor = UIColor.white
+        self.vibrancyView.contentView.addSubview(self.placeholderView)
+        
+        self.dataSource.placeholderView = self.vibrancyView
+        
+        self.dataSource.cellConfigurationHandler = { [unowned self] (cell, item, indexPath) in
+            self.configure(cell as! GridCollectionViewCell, for: indexPath)
+        }
+        
+        self.dataSource.prefetchHandler = { [unowned self] (saveState, indexPath, completionHandler) in
+            let imageOperation = LoadImageURLOperation(url: saveState.imageFileURL)
+            imageOperation.resultHandler = { (image, error) in
+                completionHandler(image, error)
+            }
+                        
+            if self.isAppearing
+            {
+                imageOperation.start()
+                imageOperation.waitUntilFinished()
+                return nil
+            }
+            
+            return imageOperation
+        }
+        
+        self.dataSource.prefetchCompletionHandler = { (cell, image, indexPath, error) in
+            guard let image = image, let cell = cell as? GridCollectionViewCell else { return }
+            
+            cell.imageView.backgroundColor = nil
+            cell.imageView.image = image
+            
+            cell.isImageViewVibrancyEnabled = false
+        }
+    }
+}
+
 private extension SaveStatesViewController
 {
     //MARK: - Update -
-    
     func updateDataSource()
     {
         let fetchRequest: NSFetchRequest<SaveState> = SaveState.fetchRequest()
@@ -194,7 +229,7 @@ private extension SaveStatesViewController
     
     //MARK: - Configure Views -
     
-    func configure(_ cell: GridCollectionViewCell, for indexPath: IndexPath, ignoreExpensiveOperations ignoreOperations: Bool = false)
+    func configure(_ cell: GridCollectionViewCell, for indexPath: IndexPath)
     {
         let saveState = self.dataSource.item(at: indexPath)
         
@@ -213,32 +248,6 @@ private extension SaveStatesViewController
             cell.isImageViewVibrancyEnabled = true
         }        
         
-        if !ignoreOperations
-        {
-            let imageOperation = LoadImageURLOperation(url: saveState.imageFileURL)
-            imageOperation.resultsCache = self.imageCache
-            imageOperation.resultHandler = { (image, error) in
-                
-                if let image = image
-                {
-                    DispatchQueue.main.async {
-                        cell.imageView.backgroundColor = nil
-                        cell.imageView.image = image
-                        
-                        cell.isImageViewVibrancyEnabled = false
-                    }
-                }
-            }
-            
-            // Ensure initially visible cells have loaded their image before they appear to prevent potential flickering from placeholder to thumbnail
-            if self.isAppearing
-            {
-                imageOperation.isImmediate = true
-            }
-            
-            self.imageOperationQueue.addOperation(imageOperation, forKey: indexPath as NSCopying)
-        }
-        
         let deltaCore = Delta.core(for: self.game.type)!
         
         let dimensions = deltaCore.videoFormat.dimensions
@@ -577,7 +586,7 @@ extension SaveStatesViewController: UIViewControllerPreviewingDelegate
         
         let saveState = self.dataSource.item(at: indexPath)
         let actions = self.actionsForSaveState(saveState)?.previewActions ?? []
-        let previewImage = self.imageCache.object(forKey: saveState.imageFileURL as NSURL) ?? UIImage(contentsOfFile: saveState.imageFileURL.path)
+        let previewImage = self.dataSource.prefetchItemCache.object(forKey: saveState) ?? UIImage(contentsOfFile: saveState.imageFileURL.path)
         
         let previewGameViewController = PreviewGameViewController()
         previewGameViewController.game = self.game
@@ -655,12 +664,6 @@ extension SaveStatesViewController
         case .loading: self.loadSaveState(saveState)
         }
     }
-    
-    override func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath)
-    {
-        let operation = self.imageOperationQueue[indexPath as NSCopying]
-        operation?.cancel()
-    }
 }
 
 //MARK: - <UICollectionViewDelegateFlowLayout> -
@@ -668,8 +671,7 @@ extension SaveStatesViewController: UICollectionViewDelegateFlowLayout
 {
     func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
     {
-        // No need to load images from disk just to determine size, so we pass true for ignoreExpensiveOperations
+        self.configure(self.prototypeCell, for: indexPath)
-        self.configure(self.prototypeCell, for: indexPath, ignoreExpensiveOperations: true)
         
         let size = self.prototypeCell.contentView.systemLayoutSizeFitting(UILayoutFittingCompressedSize)
         return size

Delta/Settings/Controller Skins/ControllerSkinsViewController.swift

@@ -12,15 +12,6 @@ import DeltaCore
 
 import Roxas
 
-extension ControllerSkinsViewController
-{
-    enum Section: Int
-    {
-        case standard
-        case custom
-    }
-}
-
 class ControllerSkinsViewController: UITableViewController
 {
     var system: System! {
@@ -35,11 +26,16 @@ class ControllerSkinsViewController: UITableViewController
         }
     }
     
-    fileprivate let dataSource = RSTFetchedResultsTableViewDataSource<ControllerSkin>(fetchedResultsController: NSFetchedResultsController())
+    fileprivate let dataSource: RSTFetchedResultsTableViewPrefetchingDataSource<ControllerSkin, UIImage>
     
-    fileprivate let imageOperationQueue = RSTOperationQueue()
+    required init?(coder aDecoder: NSCoder)
-    
+    {
-    fileprivate let imageCache = NSCache<ControllerSkinImageCacheKey, UIImage>()
+        self.dataSource = RSTFetchedResultsTableViewPrefetchingDataSource<ControllerSkin, UIImage>(fetchedResultsController: NSFetchedResultsController())
+        
+        super.init(coder: aDecoder)
+        
+        self.prepareDataSource()
+    }
 }
 
 extension ControllerSkinsViewController
@@ -48,11 +44,8 @@ extension ControllerSkinsViewController
     {
         super.viewDidLoad()
         
-        self.dataSource.proxy = self
-        self.dataSource.cellConfigurationHandler = { [unowned self] (cell, item, indexPath) in
-            self.configure(cell as! ControllerSkinTableViewCell, for: indexPath)
-        }
         self.tableView.dataSource = self.dataSource
+        self.tableView.prefetchDataSource = self.dataSource
     }
 
     override func didReceiveMemoryWarning()
@@ -65,6 +58,41 @@ extension ControllerSkinsViewController
 private extension ControllerSkinsViewController
 {
     //MARK: - Update
+    func prepareDataSource()
+    {
+        self.dataSource.proxy = self
+        self.dataSource.cellConfigurationHandler = { (cell, item, indexPath) in
+            let cell = cell as! ControllerSkinTableViewCell
+            
+            cell.controllerSkinImageView.image = nil
+            cell.activityIndicatorView.startAnimating()
+        }
+        
+        self.dataSource.prefetchHandler = { [unowned self] (controllerSkin, indexPath, completionHandler) in
+            let imageOperation = LoadControllerSkinImageOperation(controllerSkin: controllerSkin, traits: self.traits, size: UIScreen.main.defaultControllerSkinSize)
+            imageOperation.resultHandler = { (image, error) in
+                completionHandler(image, error)
+            }
+            
+            // Ensure initially visible cells have loaded their image before they appear to prevent potential flickering from placeholder to thumbnail
+            if self.isAppearing
+            {
+                imageOperation.start()
+                imageOperation.waitUntilFinished()
+                return nil
+            }
+            
+            return imageOperation
+        }
+        
+        self.dataSource.prefetchCompletionHandler = { (cell, image, indexPath, error) in
+            guard let image = image, let cell = cell as? ControllerSkinTableViewCell else { return }
+            
+            cell.controllerSkinImageView.image = image
+            cell.activityIndicatorView.stopAnimating()
+        }
+    }
+    
     func updateDataSource()
     {
         guard let system = self.system, let traits = self.traits else { return }
@@ -77,45 +105,6 @@ private extension ControllerSkinsViewController
         
         self.dataSource.fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: DatabaseManager.shared.viewContext, sectionNameKeyPath: #keyPath(ControllerSkin.name), cacheName: nil)
     }
-    
-    //MARK: - Configure Cells
-    func configure(_ cell: ControllerSkinTableViewCell, for indexPath: IndexPath)
-    {
-        let controllerSkin = self.dataSource.item(at: indexPath)
-        
-        cell.controllerSkinImageView.image = nil
-        cell.activityIndicatorView.startAnimating()
-        
-        let size = UIScreen.main.defaultControllerSkinSize
-        
-        let imageOperation = LoadControllerSkinImageOperation(controllerSkin: controllerSkin, traits: self.traits, size: size)
-        imageOperation.resultsCache = self.imageCache
-        imageOperation.resultHandler = { (image, error) in
-            
-            guard let image = image else { return }
-            
-            if !imageOperation.isImmediate
-            {
-                UIView.transition(with: cell.controllerSkinImageView, duration: 0.2, options: .transitionCrossDissolve, animations: {
-                    cell.controllerSkinImageView.image = image
-                }, completion: nil)
-            }
-            else
-            {
-                cell.controllerSkinImageView.image = image
-            }
-            
-            cell.activityIndicatorView.stopAnimating()
-        }
-        
-        // Ensure initially visible cells have loaded their image before they appear to prevent potential flickering from placeholder to thumbnail
-        if self.isAppearing
-        {
-            imageOperation.isImmediate = true
-        }
-        
-        self.imageOperationQueue.addOperation(imageOperation, forKey: indexPath as NSCopying)
-    }
 }
 
 extension ControllerSkinsViewController
@@ -127,33 +116,6 @@ extension ControllerSkinsViewController
     }
 }
 
-extension ControllerSkinsViewController: UITableViewDataSourcePrefetching
-{
-    func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath])
-    {
-        for indexPath in indexPaths
-        {
-            let controllerSkin = self.dataSource.item(at: indexPath)
-            
-            let size = UIScreen.main.defaultControllerSkinSize
-            
-            let imageOperation = LoadControllerSkinImageOperation(controllerSkin: controllerSkin, traits: self.traits, size: size)
-            imageOperation.resultsCache = self.imageCache
-            
-            self.imageOperationQueue.addOperation(imageOperation, forKey: indexPath as NSCopying)
-        }
-    }
-    
-    func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath])
-    {
-        for indexPath in indexPaths
-        {
-            let operation = self.imageOperationQueue[indexPath as NSCopying]
-            operation?.cancel()
-        }
-    }
-}
-
 extension ControllerSkinsViewController
 {
     override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)
@@ -176,10 +138,4 @@ extension ControllerSkinsViewController
         
         return height
     }
-    
-    override func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath)
-    {
-        let operation = self.imageOperationQueue[indexPath as NSCopying]
-        operation?.cancel()
-    }
 }

External/Roxas

@@ -1 +1 @@
-Subproject commit 3ecd5e6e727181d0d1c9984079a809483c247c24
+Subproject commit 7434aef0372aca1d0b12cc4b8a6a37df034aae7c