cache image dimensions and (chapter, page) used for scrolling, fix bug related to width and height of UICollectionViewCell

ExportOptions.plist

@@ -3,11 +3,15 @@
  "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-    <key>uploadBitcode</key>
-    <false/>
-    <key>uploadSymbols</key>
+    <key>method</key>
+    <string>debugging</string>
+    <key>signingStyle</key>
+    <string>automatic</string>
+    <key>destination</key>
+    <string>export</string>
+    <key>stripSwiftSymbols</key>
     <true/>
     <key>compileBitcode</key>
-    <true/>
+    <false/>
 </dict>
 </plist>

ImageViewer/ViewController.swift

@@ -1,11 +1,13 @@
 //TODO: Implement support for bonus chapters
 //TODO: Implement Anilist support?
 //TODO: Properly avoid swallowing of input from UICollectionView used for scrolling
-//TODO: Fix UICollectionView sizeForItemAt method performance either by caching or lazy loading
+//TODO: Convert between state for normal and scrolling page turn
 
 import UIKit
 
-let preloadCount = 3
+let preloadCount = 2
+// With a whopping 2 cores, and 2 threads because no hyperthreading, it makes sense to only have a queue as an extra thread to do work with to allow the main thread for ui.
+let queue = DispatchQueue(label: "queue", qos: .utility)
 
 enum PageTurn {
     case next
@@ -69,6 +71,9 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
     var scrollPos: CGPoint!
     var hasSetContentOffset = false
     var pageCount = 0
+    var pagesAvailable = 0
+    var sizeList: [CGSize] = []
+    var chapterAndPages: [(Int, Int)] = []
 
     var imageView = UIImageView()
     var mode = PageTurnMode.leftToRight
@@ -106,12 +111,10 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
 
     let imageLoader = ImageLoader.init()
 
-    let localStateQueue = DispatchQueue(label: "state.local.queue", qos: .background)
-
     override func viewDidLoad() {
         super.viewDidLoad()
 
-        view.backgroundColor = .clear
+        view.backgroundColor = .white
 
         setup()
     }
@@ -249,10 +252,10 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
             case .leftToRight:
                 ReadProgress.leftToRight(chapter: self.currentChapter, page: self.currentPage)
             case .rightToLeft:
-                ReadProgress.leftToRight(chapter: self.currentChapter, page: self.currentPage)
+                ReadProgress.rightToLeft(chapter: self.currentChapter, page: self.currentPage)
             case .scroll: ReadProgress.scroll(scrollingCollectionView.contentOffset)
             }
-        localStateQueue.async {
+        queue.async {
             do {
                 try JSONEncoder().encode(
                     LocalState(
@@ -285,6 +288,17 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
             case .scroll(let point):
                 if self.scrollPos == nil {
                     self.scrollPos = point
+                    let centerPoint = CGPoint(
+                        x: scrollingCollectionView.bounds.midX
+                            + scrollingCollectionView.contentOffset.x,
+                        y: scrollingCollectionView.bounds.midY
+                            + scrollingCollectionView.contentOffset.y)
+
+                    if let indexPath = scrollingCollectionView.indexPathForItem(at: centerPoint) {
+                        let (chapter, page) = chapterAndPages[indexPath.item]
+                        currentChapter = chapter
+                        currentPage = page
+                    }
                 }
                 self.mode = .scroll
             }
@@ -313,13 +327,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
             y: scrollingCollectionView.bounds.midY + scrollingCollectionView.contentOffset.y)
 
         if let indexPath = scrollingCollectionView.indexPathForItem(at: centerPoint) {
-            var index = 0
-            var (chapter, page) = (1, 1)
-            while index < indexPath.item {
-                (chapter, page) = getChapterAndPageFromTurn(
-                    chapter: chapter, page: page, turn: .next)
-                index += 1
-            }
+            let (chapter, page) = chapterAndPages[indexPath.item]
             currentChapter = chapter
             currentPage = page
         }
@@ -330,7 +338,9 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
 
     override func viewDidLayoutSubviews() {
         super.viewDidLayoutSubviews()
-        if scrollingCollectionView.isHidden == false && mode == .scroll && !hasSetContentOffset {
+        if scrollingCollectionView.isHidden == false && mode == .scroll
+            && !hasSetContentOffset
+        {
             scrollingCollectionView.setContentOffset(scrollPos, animated: false)
             hasSetContentOffset = true
         }
@@ -343,7 +353,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
         if let path = getPathFromComicName(name: name) {
             currentPath = path
             metadata = getMetadata(path: path)!
-            pageCount = metadata.chapters.map { $0.pages }.reduce(0, +)
+
             globalState.comicName = metadata.title
             saveGlobalState()
             loadLocalState()
@@ -353,14 +363,80 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
                 rightView.isHidden = false
                 setImages(path: path, metadata: metadata)
             } else {
-                leftView.isHidden = true
-                rightView.isHidden = true
-                scrollingCollectionView.isHidden = false
-                scrollingCollectionView.reloadData()
+                setupScrolling()
             }
         }
     }
 
+    func setupScrolling() {
+        leftView.isHidden = true
+        rightView.isHidden = true
+        scrollingCollectionView.isHidden = false
+        pagesAvailable = countFiles()
+        var index = 0
+        var (chapter, page) = (1, 1)
+        chapterAndPages = Array(repeating: (0, 0), count: pagesAvailable + 1)
+        chapterAndPages[index] = (chapter, page)
+        while index < pagesAvailable {
+            index += 1
+            (chapter, page) = getChapterAndPageFromTurn(
+                chapter: chapter, page: page, turn: .next)
+            chapterAndPages[index] = (chapter, page)
+        }
+
+        sizeList = Array(repeating: CGSize(), count: pagesAvailable)
+        let binPath = currentPath.appendingPathComponent("size.bin")
+        let decoder = PropertyListDecoder()
+        do {
+            let data = try Data(contentsOf: binPath)
+            sizeList = try decoder.decode([CGSize].self, from: data)
+        } catch {
+            print("Failed to read data:", error)
+        }
+
+        scrollingCollectionView.reloadData()
+        DispatchQueue.main.async {
+            let encoder = PropertyListEncoder()
+            encoder.outputFormat = .binary
+            do {
+                let data = try encoder.encode(self.sizeList)
+                try data.write(to: binPath)
+            } catch {
+                print("Encoding or writing failed:", error)
+            }
+        }
+    }
+
+    func countFiles() -> Int {
+        var count = 0
+        if let enumerator = fileManager.enumerator(
+            at: currentPath, includingPropertiesForKeys: [.isDirectoryKey],
+            options: [.skipsHiddenFiles])
+        {
+            for case let dir as URL in enumerator {
+                do {
+                    if let enumerator = fileManager.enumerator(
+                        at: dir, includingPropertiesForKeys: [.isRegularFileKey],
+                        options: [.skipsHiddenFiles])
+                    {
+                        for case let file as URL in enumerator {
+                            let resourceValues = try file.resourceValues(forKeys: [
+                                .isRegularFileKey
+                            ])
+                            if resourceValues.isRegularFile == true {
+                                count += 1
+                            }
+                        }
+                    }
+
+                } catch {
+                    print("Error reading file attributes for \(dir):", error)
+                }
+            }
+        }
+        return count
+    }
+
     func setupScrollingCollectionView() {
         let layout = UICollectionViewFlowLayout()
         layout.minimumInteritemSpacing = 0
@@ -368,7 +444,6 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
         scrollingCollectionView = UICollectionView(
             frame: view.bounds, collectionViewLayout: layout)
         scrollingCollectionView.translatesAutoresizingMaskIntoConstraints = false
-        scrollingCollectionView.isUserInteractionEnabled = true
         scrollingCollectionView.dataSource = self
         scrollingCollectionView.delegate = self
         scrollingCollectionView.backgroundColor = .white
@@ -383,7 +458,6 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
             scrollingCollectionView.trailingAnchor.constraint(equalTo: readerView.trailingAnchor),
             scrollingCollectionView.heightAnchor.constraint(equalTo: readerView.heightAnchor),
         ])
-
     }
 
     func setupTapZones() {
@@ -639,16 +713,28 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
 
     @objc func handlePageTurnOption(_ sender: UIButton) {
         if let title = sender.currentTitle {
+            let prev = mode
             switch title.lowercased() {
             case "left to right": mode = .leftToRight
             case "right to left": mode = .rightToLeft
-            case "scroll":
-                if mode != .scroll {
-                    scrollingCollectionView.reloadData()
-                }
-                mode = .scroll
+            case "scroll": mode = .scroll
             default: break
             }
+            if prev == mode { return }
+            if mode == .scroll {
+                setupScrolling()
+            } else {
+                imageLoader.loadImage(
+                    at: getImagePath(
+                        chapter: currentChapter,
+                        volume: Int(metadata.chapters[currentChapter - 1].volume),
+                        page: currentPage,
+                        path: currentPath)
+                ) {
+                    [weak self] image in
+                    self?.imageView.image = image
+                }
+            }
         }
         scrollingCollectionView.isHidden = mode != .scroll
         leftView.isHidden = mode == .scroll
@@ -824,7 +910,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
 
         if let chapterTitle = metadata.chapters[currentChapter - 1].title {
             text =
-                text + "\(chapterTitle)"
+                text + "\(chapterTitle)\n"
         }
         text =
             text + """
@@ -1002,7 +1088,7 @@ extension ViewController: UICollectionViewDataSource, UICollectionViewDelegateFl
         if collectionView == comicCollectionView {
             return comics.count
         } else {
-            return pageCount
+            return pagesAvailable
         }
     }
 
@@ -1024,20 +1110,26 @@ extension ViewController: UICollectionViewDataSource, UICollectionViewDelegateFl
             if metadata == nil {
                 return cell
             }
-            var index = 0
-            var (chapter, page) = (1, 1)
-            while index < indexPath.item {
-                (chapter, page) = getChapterAndPageFromTurn(
-                    chapter: chapter, page: page, turn: .next)
-                index += 1
-            }
+            var (chapter, page) = chapterAndPages[indexPath.item]
             if let url = getImagePath(
                 chapter: chapter,
                 volume: Int(metadata.chapters[chapter - 1].volume),
                 page: page, path: currentPath)
             {
-                // cell.imageView.image = UIImage(contentsOfFile: url.path)
                 imageLoader.loadImage(at: url) { image in cell.imageView.image = image }
+                for _ in 0...preloadCount {
+                    (chapter, page) = getChapterAndPageFromTurn(
+                        chapter: chapter, page: page, turn: .next)
+                    if let url = getImagePath(
+                        chapter: chapter,
+                        volume: Int(metadata.chapters[chapter - 1].volume),
+                        page: page, path: currentPath)
+                    {
+                        imageLoader.preloadImage(at: url)
+                    } else {
+                        break
+                    }
+                }
             }
             return cell
         } else {
@@ -1066,13 +1158,13 @@ extension ViewController: UICollectionViewDataSource, UICollectionViewDelegateFl
             if metadata == nil {
                 return CGSize()
             }
-            var index = 0
-            var (chapter, page) = (1, 1)
-            while index < indexPath.item {
-                (chapter, page) = getChapterAndPageFromTurn(
-                    chapter: chapter, page: page, turn: .next)
-                index += 1
+            if sizeList[indexPath.item] != CGSize(width: 0, height: 0) {
+                return CGSize(
+                    width: readerView.bounds.width,
+                    height: sizeList[indexPath.item].height * readerView.bounds.width
+                        / sizeList[indexPath.item].width)
             }
+            let (chapter, page) = chapterAndPages[indexPath.item]
             if let imagePath = getImagePath(
                 chapter: chapter,
                 volume: Int(metadata.chapters[chapter - 1].volume),
@@ -1080,11 +1172,15 @@ extension ViewController: UICollectionViewDataSource, UICollectionViewDelegateFl
                 let imageSource = CGImageSourceCreateWithURL(imagePath as CFURL, nil),
                 let imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, nil)
                     as? [CFString: Any],
-                let height = imageProperties[kCGImagePropertyPixelHeight] as? CGFloat
+                let height = imageProperties[kCGImagePropertyPixelHeight] as? CGFloat,
+                let width = imageProperties[kCGImagePropertyPixelWidth] as? CGFloat
             {
-                return CGSize(width: readerView.bounds.width, height: height)
+                sizeList[indexPath.item] = CGSize(width: width, height: height)
+                return CGSize(
+                    width: readerView.bounds.width, height: height * readerView.bounds.width / width
+                )
             }
-            return CGSize(width: readerView.bounds.width, height: readerView.bounds.height)
+            return CGSize()
         } else {
             assert(false)
         }
@@ -1152,7 +1248,6 @@ class ComicImageCell: UICollectionViewCell {
 class ImageLoader {
     private let cache = NSCache<NSString, UIImage>()
     private var loadingTasks: [String: [((UIImage?) -> Void)]] = [:]
-    private let queue = DispatchQueue(label: "image.loading.queue", qos: .userInitiated)
 
     init() {
         cache.totalCostLimit = 50 * 1024 * 1024