fix: scrolling set offset on startup, scale fill to width, info update, background color

ImageViewer/ViewController.swift

@@ -124,6 +124,20 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
         if let alert = pendingAlert {
             present(alert, animated: false, completion: nil)
         }
+        if !hasSetContentOffset, scrollPos != nil {
+            let screenSize = UIScreen.main.bounds.size
+            var offset = scrollPos!
+            if screenSize.width > screenSize.height {
+                offset.y *= (screenSize.width / screenSize.height)
+            }
+            scrollingCollectionView.setContentOffset(offset, animated: false)
+            hasSetContentOffset = true
+        } else {
+            let screenSize = UIScreen.main.bounds.size
+            var offset = scrollingCollectionView.contentOffset
+            offset.y *= (screenSize.width / screenSize.height)
+            scrollingCollectionView.setContentOffset(offset, animated: false)
+        }
     }
 
     func setup() {
@@ -872,8 +886,8 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
     func scrollViewDidScroll(_: UIScrollView) {
         if scrollingCollectionView.isHidden { return }
         let centerPoint = CGPoint(
-            x: scrollingCollectionView.bounds.midX + scrollingCollectionView.contentOffset.x,
-            y: scrollingCollectionView.bounds.midY + scrollingCollectionView.contentOffset.y
+            x: scrollingCollectionView.bounds.midX,
+            y: scrollingCollectionView.bounds.midY,
         )
 
         if let indexPath = scrollingCollectionView.indexPathForItem(at: centerPoint) {
@@ -907,20 +921,6 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
             }
             return
         }
-        if !hasSetContentOffset, scrollPos != nil {
-            let screenSize = UIScreen.main.bounds.size
-            var offset = scrollPos!
-            if screenSize.width > screenSize.height {
-                offset.y *= (screenSize.width / screenSize.height)
-            }
-            scrollingCollectionView.setContentOffset(offset, animated: false)
-            hasSetContentOffset = true
-        } else {
-            let screenSize = UIScreen.main.bounds.size
-            var offset = scrollingCollectionView.contentOffset
-            offset.y *= (screenSize.width / screenSize.height)
-            scrollingCollectionView.setContentOffset(offset, animated: false)
-        }
     }
 
     func readComic(name: String) {
@@ -941,6 +941,7 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
             imageView.isHidden = mode == .scroll
             if mode == .scroll {
                 scrollingCollectionView.reloadData()
+                updateInfo()
             } else {
                 setImages()
             }
@@ -959,7 +960,7 @@ final class ViewController: UIViewController, UIGestureRecognizerDelegate {
         scrollingCollectionView.translatesAutoresizingMaskIntoConstraints = false
         scrollingCollectionView.dataSource = self
         scrollingCollectionView.delegate = self
-        scrollingCollectionView.backgroundColor = .white
+        scrollingCollectionView.backgroundColor = .clear
         scrollingCollectionView.isHidden = true
         scrollingCollectionView.register(
             ScrollingImageCell.self, forCellWithReuseIdentifier: "ScrollingImageCell"
@@ -1687,6 +1688,7 @@ enum Rotation {
 }
 
 class ImageLoader {
+    // Fill is kind of a lie here, it is actually FillToWidth, because that is what makes sense for scrolling.
     private let cache = NSCache<NSString, UIImage>()
     private let portraitFitCache = NSCache<NSString, UIImage>()
     private let landscapeFitCache = NSCache<NSString, UIImage>()
@@ -1836,7 +1838,9 @@ class ImageLoader {
                 height: min(screenSize.height, screenSize.width)
             )
         }
-        let scaledSize = aspectSize(for: image.size, in: resizeTo, scaling: scaling)
+        let scaledSize = image.size.height > image.size.width && scaling == .scaleAspectFill ?
+        aspectSize(for: image.size, in: resizeTo, scaling: scaling) :
+        aspectSize(for: image.size, in: resizeTo, scaling: .scaleAspectFit)
         let scaledImage = resizeImage(image, to: scaledSize)
         let cost = imageByteSize(scaledImage)!
         switch (orientation, scaling) {
@@ -2235,28 +2239,29 @@ extension ViewController {
 
     private func makePageTurnTree() -> [SettingsMenuItem] {
         return pageTurnDefaultItems { [self] pageTurnMode in
-            if self.mode == pageTurnMode { return }
-
-            if self.mode != .scroll {
-                let archiveURL = getArchiveURL(progress.v)
-                imageLoader.loadImage(
-                    archiveURL: archiveURL,
-                    filename: getImagePath(self.progress),
-                    scaling: .scaleAspectFit,
-                    screenSize: UIScreen.main.bounds.size
-                ) { [weak self] image in
-                    self?.imageView.image = image
-                }
+            if mode == pageTurnMode { return }
+            let scrollSwitch = mode != .scroll && pageTurnMode != .scroll
+            mode = pageTurnMode
+            saveLocalState()
+            if scrollSwitch { return }
+            let archiveURL = getArchiveURL(progress.v)
+            imageLoader.loadImage(
+                archiveURL: archiveURL,
+                filename: getImagePath(progress),
+                scaling: .scaleAspectFit,
+                screenSize: UIScreen.main.bounds.size
+            ) { [weak self] image in
+                self?.imageView.image = image
             }
+
             scrollingCollectionView.isHidden = mode != .scroll
             leftView.isHidden = mode == .scroll
             rightView.isHidden = mode == .scroll
             imageView.isHidden = mode == .scroll
+
             if mode == .scroll {
                 scrollingCollectionView.reloadData()
             }
-            self.mode = pageTurnMode
-            saveLocalState()
         }
     }