Match gif playback progress through animation

Closes #8

Tusker/ImageGrayscalifier.swift

@@ -17,6 +17,7 @@ struct ImageGrayscalifier {
     static func convertIfNecessary(url: URL?, image: UIImage) -> UIImage? {
         if Preferences.shared.grayscaleImages,
            let source = image.cgImage {
+            // todo: should this return the original image if conversion fails?
             return convert(url: url, cgImage: source)
         } else {
             return image

Tusker/Screens/Attachment Gallery/AttachmentPreviewViewController.swift

@@ -11,10 +11,12 @@ import Pachyderm
 
 class AttachmentPreviewViewController: UIViewController {
 
-    let attachment: Attachment
+    private let attachment: Attachment
+    private let sourceView: AttachmentView
     
-    init(attachment: Attachment) {
+    init(sourceView: AttachmentView) {
-        self.attachment = attachment
+        self.attachment = sourceView.attachment
+        self.sourceView = sourceView
 
         super.init(nibName: nil, bundle: nil)
     }
@@ -29,7 +31,9 @@ class AttachmentPreviewViewController: UIViewController {
             let imageView: UIImageView
             if attachment.url.pathExtension == "gif" {
                 let gifView = GIFImageView(image: image)
-                gifView.animate(withGIFData: data)
+                let controller = sourceView.gifController ?? GIFController(gifData: data)
+                controller.attach(to: gifView)
+                controller.startAnimating()
                 imageView = gifView
             } else {
                 imageView = UIImageView(image: image)

Tusker/Screens/Attachment Gallery/GalleryViewController.swift

@@ -41,14 +41,6 @@ class GalleryViewController: UIPageViewController, UIPageViewControllerDataSourc
             return animationSourceView?.image
         }
     }
-    var animationGifData: Data? {
-        let attachment = attachments[currentIndex]
-        if attachment.url.pathExtension == "gif" {
-            return ImageCache.attachments.getData(attachment.url)
-        } else {
-            return nil
-        }
-    }
     var dismissInteractionController: LargeImageInteractionController?
     
     var isInteractivelyAnimatingDismissal: Bool = false {

Tusker/Screens/Large Image/LargeImageContentView.swift

@@ -12,7 +12,6 @@ import AVFoundation
 
 protocol LargeImageContentView: UIView {
     var animationImage: UIImage? { get }
-    var animationGifData: Data? { get }
     var activityItemsForSharing: [Any] { get }
     func grayscaleStateChanged()
 }
@@ -20,7 +19,6 @@ protocol LargeImageContentView: UIView {
 class LargeImageImageContentView: GIFImageView, LargeImageContentView {
     
     var animationImage: UIImage? { image! }
-    let animationGifData: Data?
     
     var activityItemsForSharing: [Any] {
         [image!]
@@ -28,22 +26,12 @@ class LargeImageImageContentView: GIFImageView, LargeImageContentView {
     
     private var sourceData: Data?
     
-    convenience init(sourceData data: Data, isGif: Bool) {
-        self.init(image: UIImage(data: data)!, gifData: isGif ? data : nil)
-        
-        self.sourceData = data
-    }
-    
-    init(image: UIImage, gifData: Data?) {
-        self.animationGifData = gifData
     
+    init(image: UIImage) {
         super.init(image: image)
         
         contentMode = .scaleAspectFit
         
-        if let data = gifData {
-            self.animate(withGIFData: data)
-        }
     }
     
     required init?(coder: NSCoder) {
@@ -68,9 +56,35 @@ class LargeImageImageContentView: GIFImageView, LargeImageContentView {
     }
 }
 
+class LargeImageGifContentView: GIFImageView, LargeImageContentView {
+    var animationImage: UIImage? { image }
+    
+    var activityItemsForSharing: [Any] {
+        // todo: should gifs share the data?
+        [image].compactMap { $0 }
+    }
+    
+    init(gifController: GIFController) {
+        super.init(image: gifController.lastFrame?.image)
+        
+        contentMode = .scaleAspectFit
+        
+        gifController.attach(to: self)
+        // todo: doing this in the init feels wrong
+        gifController.startAnimating()
+    }
+    
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    func grayscaleStateChanged() {
+        // todo
+    }
+}
+
 class LargeImageGifvContentView: GifvAttachmentView, LargeImageContentView {
     private(set) var animationImage: UIImage?
-    var animationGifData: Data? { nil }
     var activityItemsForSharing: [Any] {
         // todo: what should we share for gifvs?
         // some SO posts indicate that just sharing a URL to the video should work, but that may need to be a local URL?

Tusker/Screens/Large Image/LargeImageViewController.swift

@@ -13,7 +13,6 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
     weak var animationSourceView: UIImageView?
     var largeImageController: LargeImageViewController? { self }
     var animationImage: UIImage? { contentView.animationImage }
-    var animationGifData: Data? { contentView.animationGifData }
     var dismissInteractionController: LargeImageInteractionController?
     
     @IBOutlet weak var scrollView: UIScrollView!

Tusker/Screens/Large Image/LoadingLargeImageViewController.swift

@@ -40,7 +40,6 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
     weak var animationSourceView: UIImageView?
     var largeImageController: LargeImageViewController? { largeImageVC }
     var animationImage: UIImage? { largeImageVC?.animationImage ?? animationSourceView?.image }
-    var animationGifData: Data? { largeImageVC?.animationGifData }
     var dismissInteractionController: LargeImageInteractionController?
     
     var isInteractivelyAnimatingDismissal: Bool = false {
@@ -93,6 +92,8 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
         
         // always load full resolution from disk for large image, in case the cache is scaled
         if let entry = cache.get(url, loadOriginal: true) {
+            // todo: if load original is true, is there any way entry.data could be nil?
+            // feels like the data param of createLargeImage shouldn't be optional
             createLargeImage(data: entry.data, image: entry.image, url: url)
         } else {
             createPreview()
@@ -126,19 +127,31 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
         guard !loaded else { return }
         loaded = true
         
-        if let transformedImage = ImageGrayscalifier.convertIfNecessary(url: url, image: image) {
+        let content: LargeImageContentView
-            let gifData = url.pathExtension == "gif" ? data : nil
-            createLargeImage(image: transformedImage, gifData: gifData)
-        }
-    }
         
-    private func createLargeImage(image: UIImage, gifData: Data?) {
+        // todo: p sure grayscaling gifs has never worked
-        let imageView = LargeImageImageContentView(image: image, gifData: gifData)
+        if url.pathExtension == "gif", let data = data {
-        
+            // todo: pulling the gif controller out of the source view feels icky
-        if let existing = largeImageVC {
+            // is it possible for the source view's gif controller to have different data than we just got?
-            existing.contentView = imageView
+            // should this be a property set by the animation controller instead?
+            let gifController = (animationSourceView as? GIFImageView)?.gifController ?? GIFController(gifData: data)
+            content = LargeImageGifContentView(gifController: gifController)
         } else {
-            largeImageVC = LargeImageViewController(contentView: imageView, description: imageDescription, sourceView: animationSourceView)
+            if let transformedImage = ImageGrayscalifier.convertIfNecessary(url: url, image: image) {
+                content = LargeImageImageContentView(image: transformedImage)
+            } else {
+                content = LargeImageImageContentView(image: image)
+            }
+        }
+        
+        setContent(content)
+    }
+    
+    private func setContent(_ content: LargeImageContentView) {
+        if let existing = largeImageVC {
+            existing.contentView = content
+        } else {
+            largeImageVC = LargeImageViewController(contentView: content, description: imageDescription, sourceView: animationSourceView)
             largeImageVC!.initialControlsVisible = initialControlsVisible
             largeImageVC!.shrinkGestureEnabled = false
             embedChild(largeImageVC!)
@@ -154,7 +167,7 @@ class LoadingLargeImageViewController: UIViewController, LargeImageAnimatableVie
            let grayscale = ImageGrayscalifier.convert(url: nil, cgImage: source) {
             image = grayscale
         }
-        self.createLargeImage(image: image, gifData: nil)
+        setContent(LargeImageImageContentView(image: image))
     }
     
 }

Tusker/Screens/Large Image/Transitions/LargeImageExpandAnimationController.swift

@@ -12,7 +12,6 @@ protocol LargeImageAnimatableViewController: UIViewController {
     var animationSourceView: UIImageView? { get }
     var largeImageController: LargeImageViewController? { get }
     var animationImage: UIImage? { get }
-    var animationGifData: Data? { get }
     var dismissInteractionController: LargeImageInteractionController? { get }
     var isInteractivelyAnimatingDismissal: Bool { get set }
 }
@@ -86,8 +85,8 @@ class LargeImageExpandAnimationController: NSObject, UIViewControllerAnimatedTra
 
         let imageView = GIFImageView(frame: sourceFrame)
         imageView.image = image
-        if let gifData = toVC.animationGifData {
+        if let gifController = (sourceView as? GIFImageView)?.gifController {
-            imageView.animate(withGIFData: gifData)
+            gifController.attach(to: imageView)
         }
         imageView.contentMode = .scaleAspectFill
         imageView.layer.cornerRadius = sourceView.layer.cornerRadius

Tusker/Screens/Large Image/Transitions/LargeImageShrinkAnimationController.swift

@@ -56,8 +56,10 @@ class LargeImageShrinkAnimationController: NSObject, UIViewControllerAnimatedTra
 
         let imageView = GIFImageView(frame: originalFrame)
         imageView.image = image
-        if let gifData = fromVC.animationGifData {
+        if let gifController = (sourceView as? GIFImageView)?.gifController {
-            imageView.animate(withGIFData: gifData)
+            gifController.attach(to: imageView)
+            // todo: this might not be necessary, the large image content view should have started it
+            gifController.startAnimating()
         }
         imageView.contentMode = .scaleAspectFill
         imageView.layer.cornerRadius = 0

Tusker/Views/Attachments/AttachmentView.swift

@@ -29,14 +29,6 @@ class AttachmentView: GIFImageView {
     private var attachmentRequest: ImageCache.Request?
     private var source: Source?
     
-    var gifData: Data? {
-        switch source {
-        case let .gifData(_, data):
-            return data
-        default:
-            return nil
-        }
-    }
     private var autoplayGifs: Bool {
         Preferences.shared.automaticallyPlayGifs && !ProcessInfo.processInfo.isLowPowerModeEnabled
     }
@@ -91,11 +83,13 @@ class AttachmentView: GIFImageView {
         // NSProcessInfoPowerStateDidChange is sometimes fired on a background thread
         DispatchQueue.main.async {
             if self.attachment.kind == .image,
-               let gifData = self.gifData {
+               let gifController = self.gifController {
                 if self.autoplayGifs && !self.isAnimatingGIF {
-                    self.animate(withGIFData: gifData)
+                    gifController.attach(to: self)
+                    gifController.startAnimating()
                 } else if !self.autoplayGifs && self.isAnimatingGIF {
-                    self.stopAnimatingGIF()
+                    // detach instead of stopping so that any other attached gif views keep animating
+                    self.detachGIFController()
                 }
             } else if self.attachment.kind == .gifv,
                       let gifvView = self.gifvView {
@@ -166,13 +160,18 @@ class AttachmentView: GIFImageView {
             }
             if self.attachment.url.pathExtension == "gif" {
                 self.source = .gifData(attachmentURL, data)
-                if self.autoplayGifs {
+                let controller = GIFController(gifData: data)
                 DispatchQueue.main.async {
-                        self.animate(withGIFData: data)
+                    controller.attach(to: self)
+                    if self.autoplayGifs {
+                        controller.startAnimating()
                     }
-                } else {
+                }
+                
+                if !self.autoplayGifs {
                     self.displayImage()
                 }
+                
             } else {
                 self.source = .imageData(attachmentURL, data)
                 self.displayImage()
@@ -322,7 +321,7 @@ extension AttachmentView: UIContextMenuInteractionDelegate {
     func contextMenuInteraction(_ interaction: UIContextMenuInteraction, configurationForMenuAtLocation location: CGPoint) -> UIContextMenuConfiguration? {
         return UIContextMenuConfiguration(identifier: nil, previewProvider: { () -> UIViewController? in
             if self.attachment.kind == .image {
-                return AttachmentPreviewViewController(attachment: self.attachment)
+                return AttachmentPreviewViewController(sourceView: self)
             } else if self.attachment.kind == .gifv {
                 let vc = GifvAttachmentViewController(attachment: self.attachment)
                 vc.preferredContentSize = self.image?.size ?? .zero

Tusker/Views/GIFImageView.swift

@@ -10,25 +10,82 @@ import UIKit
 
 class GIFImageView: UIImageView {
     
-    private(set) var isAnimatingGIF: Bool = false
+    fileprivate(set) var gifController: GIFController? = nil
-    private var shouldStopAnimatingGIF = false
+    var isAnimatingGIF: Bool { gifController?.state == .playing }
     
+    /// Detaches the current GIF controller from this view.
+    /// If this view is the GIF controller's only one, it will stop itself.
+    func detachGIFController() {
+        gifController?.detach(from: self)
+    }
     
-    func animate(withGIFData data: Data) {
+}
-        CGAnimateImageDataWithBlock(data as CFData, nil) { [weak self] (frameIndex, frame, stop) in
+
+/// A `GIFController` controls the animation of one or more `GIFImageView`s.
+class GIFController {
+    
+    // GIFImageView strongly holds the controller so that when the last view detaches, the controller is freed
+    private var imageViews = WeakArray<GIFImageView>()
+    
+    private(set) var gifData: Data
+    private(set) var state: State = .stopped
+    private(set) var lastFrame: (image: UIImage, index: Int)? = nil
+    
+    init(gifData: Data) {
+        self.gifData = gifData
+    }
+    
+    /// Attaches another view to this controller, letting it play back alongside the others.
+    /// Immediately brings it into sync with the others, setting the last frame if there was one.
+    func attach(to view: GIFImageView) {
+        imageViews.append(view)
+        view.gifController = self
+        
+        if let lastFrame = lastFrame {
+            view.image = lastFrame.image
+        }
+    }
+    
+    /// Detaches the given view from this controller.
+    /// If no views attached views remain, the last strong reference to this controller is nilled out
+    /// and image animation will stop at the next CGAnimateImageDataWithBlock callback.
+    func detach(from view: GIFImageView) {
+        // todo: does === work the way i want here
+        imageViews.removeAll(where: { $0 === view })
+        view.gifController = nil
+    }
+    
+    func startAnimating() {
+        guard state.shouldStop else { return }
+        
+        state = .playing
+        
+        CGAnimateImageDataWithBlock(gifData as CFData, nil) { [weak self] (frameIndex, cgImage, stop) in
             guard let self = self else {
                 stop.pointee = true
                 return
             }
-            self.image = UIImage(cgImage: frame)
+            let image = UIImage(cgImage: cgImage)
-            stop.pointee = self.shouldStopAnimatingGIF
+            self.lastFrame = (image, frameIndex)
+            for case let .some(view) in self.imageViews {
+                view.image = image
+            }
+            stop.pointee = self.state.shouldStop
         }
-        isAnimatingGIF = true
     }
     
-    func stopAnimatingGIF() {
+    func stopAnimating() {
-        shouldStopAnimatingGIF = true
+        guard state == .playing else { return }
-        isAnimatingGIF = false
+        
+        state = .stopping
+    }
+    
+    enum State: Equatable {
+        case stopped, playing, stopping
+        
+        var shouldStop: Bool {
+            self == .stopped || self == .stopping
+        }
     }
     
 }