images loaded by galleryItem

deltachat-ios/Controller/GalleryViewController.swift

@@ -5,6 +5,7 @@ class GalleryViewController: UIViewController {
 
     // MARK: - data
     private let mediaMessageIds: [Int]
+    private var items: [Int: GalleryItem] = [:]
 
     // MARK: - subview specs
     private let gridDefaultSpacing: CGFloat = 5
@@ -26,6 +27,8 @@ class GalleryViewController: UIViewController {
         collection.backgroundColor = DcColors.defaultBackgroundColor
         collection.delaysContentTouches = false
         collection.alwaysBounceVertical = true
+        collection.isPrefetchingEnabled = true
+        collection.prefetchDataSource = self
         return collection
     }()
 
@@ -102,8 +105,17 @@ class GalleryViewController: UIViewController {
     }
 }
 
+extension GalleryViewController: UICollectionViewDataSourcePrefetching {
+    func collectionView(_ collectionView: UICollectionView, prefetchItemsAt indexPaths: [IndexPath]) {
+         indexPaths.forEach { if items[$0.row] == nil {
+            let item = GalleryItem(msgId: mediaMessageIds[$0.row])
+            items[$0.row] = item
+        }}
+    }
+}
+
 // MARK: - UICollectionViewDataSource, UICollectionViewDelegate
-extension GalleryViewController: UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {
+extension GalleryViewController: UICollectionViewDataSource, UICollectionViewDelegate {
 
     func numberOfSections(in collectionView: UICollectionView) -> Int {
         return 1
@@ -119,9 +131,17 @@ extension GalleryViewController: UICollectionViewDataSource, UICollectionViewDel
             for: indexPath) as? GalleryCell else {
             return UICollectionViewCell()
         }
+
         let msgId = mediaMessageIds[indexPath.row]
-        let msg = DcMsg(id: msgId)
-        galleryCell.update(msg: msg)
+        var item: GalleryItem
+        if let galleryItem = items[indexPath.row] {
+            item = galleryItem
+        } else {
+            let galleryItem = GalleryItem(msgId: msgId)
+            items[indexPath.row] = galleryItem
+            item = galleryItem
+        }
+        galleryCell.update(item: item)
         return galleryCell
     }
 
@@ -197,3 +217,112 @@ extension GalleryViewController {
         present(previewController, animated: true, completion: nil)
     }
 }
+
+class GalleryItem {
+
+    var onImageLoaded: ((UIImage?) -> Void)?
+
+    var msg: DcMsg
+
+    var fileUrl: URL? {
+        return msg.fileURL
+    }
+
+    var thumbnailImage: UIImage? {
+        willSet {
+           onImageLoaded?(newValue)
+        }
+    }
+
+    var showPlayButton: Bool {
+        switch msg.viewtype {
+        case .gif, .video:
+            return true
+        default:
+            return false
+        }
+    }
+
+    init(msgId: Int) {
+        self.msg = DcMsg(id: msgId)
+
+        if let key = msg.fileURL?.absoluteString, let image = ThumbnailCache.shared.restoreImage(key: key) {
+            self.thumbnailImage = image
+        } else {
+            loadThumbnail()
+        }
+    }
+
+    func loadThumbnail() {
+        guard let viewtype = msg.viewtype, let url = msg.fileURL else {
+            return
+        }
+        switch viewtype {
+        case .image:
+            thumbnailImage = msg.image
+        case .video:
+            loadVideoThumbnail(from: url)
+        case .gif:
+            loadGifThumbnail(from: url)
+        default:
+           safe_fatalError("unsupported viewtype - viewtype \(viewtype) not supported.")
+        }
+    }
+
+    private func loadGifThumbnail(from url: URL) {
+        DispatchQueue.global(qos: .background).async {
+            let gifThumbnail = self.gifThumbnail(url: url)
+            DispatchQueue.main.async { [weak self] in
+                self?.thumbnailImage = gifThumbnail
+                if let image = gifThumbnail {
+                    ThumbnailCache.shared.storeImage(image: image, key: url.absoluteString)
+                }
+            }
+        }
+    }
+
+    private func loadVideoThumbnail(from url: URL) {
+        DispatchQueue.global(qos: .background).async {
+            let thumbnailImage = DcUtils.generateThumbnailFromVideo(url: url)
+            DispatchQueue.main.async { [weak self] in
+                self?.thumbnailImage = thumbnailImage
+                if let image = thumbnailImage {
+                    ThumbnailCache.shared.storeImage(image: image, key: url.absoluteString)
+                }
+            }
+        }
+    }
+
+    private func gifThumbnail(url: URL) -> UIImage? {
+        return getGifSequence(url: url)?.first ?? nil
+    }
+
+    private func getGifSequence(url: URL) -> [UIImage]? {
+
+        guard let imageData = try? Data(contentsOf: url) else {
+            return nil
+        }
+
+        let gifOptions = [
+            kCGImageSourceShouldAllowFloat as String: true as NSNumber,
+            kCGImageSourceCreateThumbnailWithTransform as String: true as NSNumber,
+            kCGImageSourceCreateThumbnailFromImageAlways as String: true as NSNumber
+            ] as CFDictionary
+
+        guard let imageSource = CGImageSourceCreateWithData(imageData as CFData, gifOptions) else {
+            debugPrint("Cannot create image source with data!")
+            return nil
+        }
+
+        let framesCount = CGImageSourceGetCount(imageSource)
+        var frameList = [UIImage]()
+
+        for index in 0 ..< framesCount {
+            if let cgImageRef = CGImageSourceCreateImageAtIndex(imageSource, index, nil) {
+                let uiImageRef = UIImage(cgImage: cgImageRef)
+                frameList.append(uiImageRef)
+            }
+        }
+        return frameList
+    }
+}

deltachat-ios/Helper/ThumbnailCache.swift

@@ -12,10 +12,15 @@ class ThumbnailCache {
     }()
 
     func storeImage(image: UIImage, key: String){
-        cache.setObject(image, forKey: NSString(string: key))
+        // cache.setObject(image, forKey: NSString(string: key))
     }
 
     func restoreImage(key: String) -> UIImage? {
-        return cache.object(forKey: NSString(string: key))
+        return nil
+        //     return cache.object(forKey: NSString(string: key))
+    }
+
+    func clearCache() {
+        cache.removeAllObjects()
     }
 }

deltachat-ios/View/Cell/GalleryCell.swift

@@ -5,6 +5,8 @@ import SDWebImage
 class GalleryCell: UICollectionViewCell {
     static let reuseIdentifier = "gallery_cell"
 
+    weak var item: GalleryItem?
+
     var imageView: UIImageView = {
         let view = UIImageView()
         view.contentMode = .scaleAspectFill
@@ -29,6 +31,11 @@ class GalleryCell: UICollectionViewCell {
         fatalError("init(coder:) has not been implemented")
     }
 
+    override func prepareForReuse() {
+        super.prepareForReuse()
+        item = nil
+    }
+
     private func setupSubviews() {
         contentView.addSubview(imageView)
         imageView.translatesAutoresizingMaskIntoConstraints = false
@@ -43,34 +50,18 @@ class GalleryCell: UICollectionViewCell {
         playButtonView.constraint(equalTo: CGSize(width: 50, height: 50))
     }
 
-    func update(msg: DcMsg) {
-        guard let viewtype = msg.viewtype, let fileUrl = msg.fileURL else {
-            return
-        }
-        switch viewtype {
-        case .image:
-            imageView.image = msg.image
-            playButtonView.isHidden = true
-        case .video:
-            let key = fileUrl.absoluteString
-            if let image = ThumbnailCache.shared.restoreImage(key: key) {
-                imageView.image = image
-            } else {
-                imageView.loadVideoThumbnail(from: fileUrl, placeholderImage: nil) { thumbnail in
-                    if let image = thumbnail {
-                        ThumbnailCache.shared.storeImage(image: image, key: key)
-                    }
-                }
-            }
-            playButtonView.isHidden = false
-        case .gif:
-            imageView.sd_setImage(with: fileUrl, placeholderImage: nil)
-            playButtonView.isHidden = true
-        default:
-            safe_fatalError("unsupported viewtype - viewtype \(viewtype) not supported.")
+    func update(item: GalleryItem) {
+        item.onImageLoaded = { [weak self] image in
+            print("dc_debug: image set")
+            self?.imageView.image = image
         }
+        playButtonView.isHidden = !item.showPlayButton
+        self.item = item
+        imageView.image = item.thumbnailImage
+
     }
 
+
     override var isSelected: Bool {
         willSet {
             // to provide visual feedback on select events