Decode video preview on background queue

commit_hash:a30188831672e51e39dcde7729bf6a8e451e9008

.mapping.json

@@ -18738,6 +18738,7 @@
   "client/ios/DivKit/Form/DivSubmitter.swift":"divkit/public/client/ios/DivKit/Form/DivSubmitter.swift",
   "client/ios/DivKit/Form/SubmitRequest.swift":"divkit/public/client/ios/DivKit/Form/SubmitRequest.swift",
   "client/ios/DivKit/IdToPath.swift":"divkit/public/client/ios/DivKit/IdToPath.swift",
+  "client/ios/DivKit/Images/AsyncDataImageHolder.swift":"divkit/public/client/ios/DivKit/Images/AsyncDataImageHolder.swift",
   "client/ios/DivKit/Images/CachedRemoteImageHolder.swift":"divkit/public/client/ios/DivKit/Images/CachedRemoteImageHolder.swift",
   "client/ios/DivKit/Images/DivImageHolderFactory.swift":"divkit/public/client/ios/DivKit/Images/DivImageHolderFactory.swift",
   "client/ios/DivKit/LayoutProvider/DivLayoutProviderHandler.swift":"divkit/public/client/ios/DivKit/LayoutProvider/DivLayoutProviderHandler.swift",

client/ios/DivKit/Extensions/DivVideoExtensions.swift

@@ -38,7 +38,13 @@ extension DivVideo: DivBlockModeling {
     let elapsedTime: Binding<Int>? = elapsedTimeVariable.flatMap {
       context.makeBinding(variableName: $0, defaultValue: 0)
     }
-    let preview: Image? = resolvePreview(resolver).flatMap(_makeImage(base64:))
+    let preview: ImageHolder = context
+      .imageHolderFactory.make(
+        nil,
+        resolvePreview(resolver)
+          .map { .imageData(ImageData(base64: $0)) }
+      )
+
     let videoData = VideoData(videos: videoSources?
       .compactMap { $0.makeVideo(resolver: resolver) } ?? []
     )
@@ -124,18 +130,3 @@ extension DivVideoScale {
     }
   }
 }
-
-private func _makeImage(base64: String) -> Image? {
-  decode(base64: base64).flatMap(Image.init(data:))
-}
-
-fileprivate func decode(base64: String) -> Data? {
-  if let data = Data(base64Encoded: base64) {
-    return data
-  }
-  if let url = URL(string: base64),
-     let dataHoldingURL = try? Data(contentsOf: url) {
-    return dataHoldingURL
-  }
-  return nil
-}

client/ios/DivKit/Images/AsyncDataImageHolder.swift

@@ -0,0 +1,85 @@
+import Foundation
+import VGSL
+
+@preconcurrency @MainActor
+final class AsyncDataImageHolder: ImageHolder {
+  private(set) weak var image: Image?
+
+  let placeholder: ImagePlaceholder?
+
+  private let imageData: ImageData
+  private let imageProcessingQueue: OperationQueueType
+  private let imageDecoder: (@Sendable (_ data: Data) -> Image?)?
+
+  nonisolated var debugDescription: String {
+    onMainThreadSync {
+      let imagePart = if let image {
+        String(format: "%.0fx%.0f", image.size.width, image.size.height)
+      } else {
+        "nil"
+      }
+      return "AsyncDataImageHolder(image=\(imagePart), placeholder=\(dbgStr(placeholder?.debugDescription)), customDecoder=\(imageDecoder != nil), queue=\(imageProcessingQueue), imageData=\(String(describing: imageData)))"
+    }
+  }
+
+  init(
+    data: ImageData,
+    imageProcessingQueue: OperationQueueType,
+    imageDecoder: (@Sendable (_ data: Data) -> Image?)? = nil,
+    placeholder: ImagePlaceholder? = nil
+  ) {
+    self.imageData = data
+    self.imageProcessingQueue = imageProcessingQueue
+    self.imageDecoder = imageDecoder
+    self.placeholder = placeholder
+  }
+
+  func requestImageWithCompletion(
+    _ completion: @escaping @MainActor (Image?) -> Void
+  ) -> Cancellable? {
+    imageData.makeImage(
+      queue: imageProcessingQueue,
+      decoder: imageDecoder
+    ) { [weak self] image in
+      guard let self else { return }
+      completion(image)
+      self.image = image
+    }
+
+    return nil
+  }
+
+  func reused(
+    with placeholder: ImagePlaceholder?,
+    remoteImageURL url: URL?
+  ) -> (any ImageHolder)? {
+    (self.placeholder === placeholder && url == nil) ? self : nil
+  }
+
+  func equals(_ other: any ImageHolder) -> Bool {
+    guard let other = other as? Self else {
+      return false
+    }
+
+    return self.imageData == other.imageData && self.imageProcessingQueue === other
+      .imageProcessingQueue
+  }
+}
+
+extension ImagePlaceholder {
+  public func toAsyncDataImageHolder(
+    imageProcessingQueue: OperationQueueType,
+    decoder: (@Sendable (Data) -> Image?)? = nil
+  ) -> ImageHolder {
+    switch self {
+    case .image, .color, .view:
+      toImageHolder()
+    case let .imageData(imageData):
+      AsyncDataImageHolder(
+        data: imageData,
+        imageProcessingQueue: imageProcessingQueue,
+        imageDecoder: decoder
+      )
+    }
+  }
+}

client/ios/DivKit/Images/DivImageHolderFactory.swift

@@ -80,7 +80,9 @@ final class DefaultImageHolderFactory: DivImageHolderFactory {
 
   func make(_ url: URL?, _ placeholder: ImagePlaceholder?) -> ImageHolder {
     guard let url else {
-      return placeholder?.toImageHolder() ?? NilImageHolder()
+      return placeholder?.toAsyncDataImageHolder(
+        imageProcessingQueue: imageProcessingQueue
+      ) ?? NilImageHolder()
     }
     return RemoteImageHolder(
       url: url,

client/ios/DivKitSVG/SVGImageHolderFactory.swift

@@ -29,17 +29,25 @@ public final class SVGImageHolderFactory: DivImageHolderFactory {
   }
 
   public func make(_ url: URL?, _ placeholder: ImagePlaceholder?) -> ImageHolder {
-    guard let url else {
-      return placeholder?.toImageHolder() ?? NilImageHolder()
+    let decoder: (
+      @Sendable (_ data: Data) -> Image?
+    )? = { [weak self] in
+      self?.svgDecoder.decode(data: $0)
+    }
+
+    return if let url {
+      RemoteImageHolder(
+        url: url,
+        placeholder: placeholder,
+        requester: requester,
+        imageProcessingQueue: imageProcessingQueue,
+        imageDecoder: decoder
+      )
+    } else {
+      placeholder?.toAsyncDataImageHolder(
+        imageProcessingQueue: imageProcessingQueue,
+        decoder: decoder
+      ) ?? NilImageHolder()
     }
-    return RemoteImageHolder(
-      url: url,
-      placeholder: placeholder,
-      requester: requester,
-      imageProcessingQueue: imageProcessingQueue,
-      imageDecoder: { [weak self] in
-        self?.svgDecoder.decode(data: $0)
-      }
-    )
   }
 }

client/ios/LayoutKit/LayoutKit/UI/Blocks/VideoBlock+UIViewRenderableBlock.swift

@@ -157,8 +157,14 @@ private final class VideoBlockView: BlockView, VisibleBoundsTrackingContainer {
       player?.set(isMuted: model.playbackConfig.isMuted)
     }
 
-    if let previewImage = model.preview {
-      preview.value.image = previewImage
+    if let preview = model.preview {
+      if !compare(preview, oldValue.preview) {
+        preview.requestImageWithCompletion { [weak self] image in
+          self?.updatePreview(image)
+        }
+      }
+    } else {
+      self.preview.value.image = nil
     }
 
     if let elapsedTime = model.elapsedTime?.value,
@@ -168,6 +174,11 @@ private final class VideoBlockView: BlockView, VisibleBoundsTrackingContainer {
     }
   }
 
+  private func updatePreview(_ image: Image?) {
+    preview.value.image = image
+    preview.value.frame = adjustPreviewFrame()
+  }
+
   private func adjustPreviewFrame() -> CGRect {
     guard let videoView,
           let videoRatio = videoView.videoRatio else {

client/ios/LayoutKit/LayoutKit/ViewModels/VideoBlockViewModel.swift

@@ -5,7 +5,7 @@ public struct VideoBlockViewModel: Equatable {
   public let playbackConfig: PlaybackConfig
   public var elapsedTime: Binding<Int>?
   public var duration: Binding<Int>?
-  public let preview: Image?
+  public let preview: ImageHolder?
   public let resumeActions: [UserInterfaceAction]
   public let pauseActions: [UserInterfaceAction]
   public let bufferingActions: [UserInterfaceAction]
@@ -18,7 +18,7 @@ public struct VideoBlockViewModel: Equatable {
   public init(
     videoData: VideoData,
     playbackConfig: PlaybackConfig,
-    preview: Image? = nil,
+    preview: ImageHolder? = nil,
     elapsedTime: Binding<Int>? = nil,
     duration: Binding<Int>? = nil,
     resumeActions: [UserInterfaceAction] = [],