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async I/O for images and local state

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This commit is contained in:
Vegard Bieker Matthey
2025-07-16 00:27:33 +02:00
parent 747fa39056
commit 15c448611e
1 changed files with 139 additions and 65 deletions
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178
ImageViewer/ViewController.swift
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@@ -1,9 +1,10 @@
//TODO: Implement support for bonus chapters
//TODO: Implement scrolling support
//TODO: Actually implement caching and do I/O on background thread
import UIKit
let preloadCount = 10
enum PageTurn {
case next
case previous
@@ -59,9 +60,6 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
var readerView = UIView()
var imageView = UIImageView()
var previousImage: UIImage?
var currentImage: UIImage?
var nextImage: UIImage?
var mode = PageTurnMode.leftToRight
var metadata: Metadata!
var currentPage: Int! = nil
@@ -92,6 +90,10 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
var comics: [Comic] = []
var collectionView: UICollectionView!
let imageLoader = ImageLoader.init()
let localStateQueue = DispatchQueue(label: "state.local.queue", qos: .background)
override func viewDidLoad() {
super.viewDidLoad()
@@ -223,18 +225,21 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
}
func saveLocalState() {
let color = self.readerView.backgroundColor ?? .white
localStateQueue.async {
do {
try JSONEncoder().encode(
LocalState(
chapter: currentChapter, page: currentPage, turnMode: mode,
backgroundColor: convertColorToString(
color: readerView.backgroundColor ?? .white))
chapter: self.currentChapter, page: self.currentPage, turnMode: self.mode,
backgroundColor: self.convertColorToString(
color: color))
).write(
to: currentPath.appendingPathComponent("state.json"))
to: self.currentPath.appendingPathComponent("state.json"))
} catch {
print("failed to save local state")
}
}
}
func loadLocalState() {
do {
@@ -275,10 +280,10 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
saveGlobalState()
loadLocalState()
setImages(path: path, metadata: metadata)
imageView.image = currentImage
info.text = """
\(metadata.title)
\(metadata.chapters[currentChapter - 1].title)
Volume \(Int(metadata.chapters[currentChapter - 1].volume))
Volume \(Int(metadata.chapters[currentChapter - 1].volume)) of \(Int(metadata.chapters.last!.volume))
Chapter \(currentChapter!) of \(Int(metadata.chapters.last!.chapter))
Page \(currentPage!) of \(metadata.chapters[currentChapter - 1].pages)
"""
@@ -363,8 +368,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
func setupBottomBarInfo() {
info.textAlignment = .center
info.numberOfLines = 0
info.text = ""
info.numberOfLines = 5
info.translatesAutoresizingMaskIntoConstraints = false
info.textColor = .white
bottomBarView.addSubview(info)
@@ -399,7 +403,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
readerView.isHidden = true
homeView.isHidden = false
globalState.comicName = nil
hideTopBar()
hideBar()
setNeedsStatusBarAppearanceUpdate()
saveGlobalState()
@@ -585,7 +589,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
return false
}
func toggleTopBar() {
func toggleBar() {
topBarView.isHidden.toggle()
bottomBarView.isHidden.toggle()
@@ -595,14 +599,15 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
}
}
func hideTopBar() {
func hideBar() {
topBarView.isHidden = true
bottomBarView.isHidden = true
pageTurnDropdownView.isHidden = true
backgroundColorDropdownView.isHidden = true
}
@objc func handleTopTap() {
toggleTopBar()
toggleBar()
}
@objc func handleLeftTap() {
@@ -655,41 +660,52 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
}
func changeImage(turn: PageTurn) {
let (chapter, page) = getChapterAndPageFromTurn(
var (chapter, page) = getChapterAndPageFromTurn(
chapter: currentChapter, page: currentPage, turn: turn)
if (chapter, page) == (currentChapter, currentPage) { return }
let (c, p) = getChapterAndPageFromTurn(chapter: chapter, page: page, turn: turn)
let vol = Int(metadata.chapters[currentChapter - 1].volume)
switch turn {
case .next:
if nextImage == nil { return }
previousImage = currentImage
currentImage = nextImage
nextImage = getImage(chapter: c, volume: vol, page: p, path: self.currentPath)
case .previous:
if previousImage == nil { return }
nextImage = currentImage
currentImage = previousImage
previousImage = getImage(chapter: c, volume: vol, page: p, path: self.currentPath)
var vol = Int(metadata.chapters[chapter - 1].volume)
if let path = getImagePath(chapter: chapter, volume: vol, page: page, path: currentPath) {
imageLoader.loadImage(at: path) {
[weak self] image in
self?.imageView.image = image
}
} else {
return
}
currentPage = page
currentChapter = chapter
imageView.image = currentImage
for _ in 0...preloadCount {
(chapter, page) = getChapterAndPageFromTurn(
chapter: chapter, page: page, turn: .next)
vol = Int(metadata.chapters[chapter - 1].volume)
if let path = getImagePath(
chapter: chapter, volume: vol, page: page, path: currentPath)
{
imageLoader.preloadImage(at: path)
} else {
print("could not preload image")
}
}
saveLocalState()
info.text = """
\(metadata.title)
\(metadata.chapters[currentChapter - 1].title)
Volume \(Int(metadata.chapters[currentChapter - 1].volume))
Volume \(Int(metadata.chapters[currentChapter - 1].volume)) of \(Int(metadata.chapters.last!.volume))
Chapter \(currentChapter!) of \(Int(metadata.chapters.last!.chapter))
Page \(currentPage!) of \(metadata.chapters[currentChapter - 1].pages)
"""
}
func getImage(chapter: Int, volume: Int, page: Int, path: URL) -> UIImage! {
func getImagePath(chapter: Int, volume: Int, page: Int, path: URL) -> URL! {
let newPath = path.appendingPathComponent(String(format: "volume_%04d", volume))
.appendingPathComponent(
// TODO: it should not be necessary to sub 1
String(format: "chapter_%04d_image_%04d.png", chapter, page - 1))
if !fileManager.fileExists(atPath: newPath.path) {
if fileManager.fileExists(atPath: newPath.path) {
return newPath
}
//TODO: Remove this
let alternatePath = path.appendingPathComponent(String(format: "volume_%04d", volume))
.appendingPathComponent(
@@ -698,9 +714,7 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
print("Did not find image at path")
return nil
}
return UIImage(contentsOfFile: alternatePath.path)!
}
return UIImage(contentsOfFile: newPath.path)!
return alternatePath
}
func getChapterAndPageFromTurn(chapter: Int, page: Int, turn: PageTurn) -> (Int, Int) {
@@ -748,21 +762,31 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
func setImages(path: URL, metadata: Metadata) {
var directories: [URL] = []
if currentPage != nil && currentChapter != nil {
currentImage = getImage(
chapter: currentChapter, volume: Int(metadata.chapters[currentChapter - 1].volume),
page: currentPage, path: currentPath)
var vol = Int(metadata.chapters[currentChapter - 1].volume)
imageLoader.loadImage(
at: getImagePath(
chapter: currentChapter, volume: vol, page: currentPage, path: currentPath
)
) {
[weak self] image in
self?.imageView.image = image
}
let (nc, np) = getChapterAndPageFromTurn(
var (chapter, page) = getChapterAndPageFromTurn(
chapter: currentChapter, page: currentPage, turn: .next)
nextImage = getImage(
chapter: nc, volume: Int(metadata.chapters[nc - 1].volume),
page: np, path: currentPath)
for _ in 0...preloadCount {
vol = Int(metadata.chapters[chapter - 1].volume)
if let path = getImagePath(
chapter: chapter, volume: vol, page: page, path: currentPath)
{
imageLoader.preloadImage(at: path)
} else {
print("could not preload image")
}
(chapter, page) = getChapterAndPageFromTurn(
chapter: chapter, page: page, turn: .next)
}
let (pc, pp) = getChapterAndPageFromTurn(
chapter: currentChapter, page: currentPage, turn: .previous)
previousImage = getImage(
chapter: pc, volume: Int(metadata.chapters[pc - 1].volume),
page: pp, path: currentPath)
return
}
@@ -781,9 +805,8 @@ class ViewController: UIViewController, UIGestureRecognizerDelegate {
let dir: URL = directories[0]
let ps: [String] = try fileManager.contentsOfDirectory(atPath: dir.path).sorted()
let current = dir.appendingPathComponent(ps[0])
let next = dir.appendingPathComponent(ps[1])
currentImage = UIImage(contentsOfFile: current.path)
nextImage = UIImage(contentsOfFile: next.path)
imageView.image = UIImage(contentsOfFile: current.path)
let path_meta = current.lastPathComponent.components(separatedBy: "_")
assert(path_meta[0] == "chapter")
currentChapter = Int(path_meta[1])!
@@ -888,3 +911,54 @@ class ImageCell: UICollectionViewCell {
fatalError("init(coder:) has not been implemented")
}
}
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
}
func preloadImage(at path: URL) {
loadImage(at: path, completion: nil)
}
func loadImage(at path: URL, completion: ((UIImage?) -> Void)?) {
if let cached = cache.object(forKey: path.path as NSString) {
completion?(cached)
return
}
if loadingTasks[path.path] != nil {
if let completion = completion {
loadingTasks[path.path]?.append(completion)
}
return
}
loadingTasks[path.path] = completion != nil ? [completion!] : []
queue.async { [weak self] in
guard let self = self else { return }
let image = UIImage(contentsOfFile: path.path)
DispatchQueue.main.async {
if let image = image, let data = image.pngData() {
self.cache.setObject(image, forKey: path.path as NSString, cost: data.count)
} else {
print("no image to cache found")
}
self.loadingTasks[path.path]?.forEach { $0(image) }
self.loadingTasks.removeValue(forKey: path.path)
}
}
}
func imageIfLoaded(at path: String) -> UIImage? {
return cache.object(forKey: path as NSString)
}
}