Fix gifv attachments not being centered

Closes #271

Tusker/Screens/Attachment Gallery/GalleryViewController.swift

@@ -99,11 +99,9 @@ class GalleryViewController: UIPageViewController, UIPageViewControllerDataSourc
                 return vc
             case .gifv:
                 // Passing the source view to the LargeImageGifvContentView is a crappy workaround for not
-                // having the video size directly inside the content view. This will break when there
+                // having the current frame to use as the animationImage. This will break when there
                 // are more than 4 attachments and there is a gifv at index >= 3 (the More... button will show
                 // in place of the fourth attachment, so there aren't source views for the attachments at index >= 3).
-                // Really, what should happen is the LargeImageGifvContentView should get the size of the video from
-                // the AVFoundation instead of the source view.
                 // This isn't a priority as only Mastodon converts gifs to gifvs, and Mastodon (in its default configuration,
                 // I don't know about forks) doesn't allow more than four attachments, meaning there will always be a source view.
                 let gifvContentView = LargeImageGifvContentView(attachment: attachment, source: sourceViews[index]!)

Tusker/Screens/Large Image/LargeImageContentView.swift

@@ -146,11 +146,9 @@ class LargeImageGifvContentView: GifvAttachmentView, LargeImageContentView {
     
     private let asset: AVURLAsset
     
-    // The content view needs to supply an intrinsicContentSize for the LargeImageViewController to handle layout/scrolling/zooming correctly
+    private var videoSize: CGSize?
     override var intrinsicContentSize: CGSize {
-        // This is a really sucky workaround for the fact that in the content view, we don't have access to the size of the underlying video.
+        videoSize ?? CGSize(width: UIView.noIntrinsicMetric, height: UIView.noIntrinsicMetric)
-        // There's probably some way of getting this from the AVPlayer/AVAsset directly
-        animationImage?.size ?? CGSize(width: UIView.noIntrinsicMetric, height: UIView.noIntrinsicMetric)
     }
 
     init(attachment: Attachment, source: UIImageView) {
@@ -163,6 +161,17 @@ class LargeImageGifvContentView: GifvAttachmentView, LargeImageContentView {
         self.animationImage = source.image
         
         self.player.play()
+        
+        Task {
+            do {
+                if let track = try await asset.loadTracks(withMediaType: .video).first {
+                    let (size, transform) = try await track.load(.naturalSize, .preferredTransform)
+                    self.videoSize = size.applying(transform)
+                    self.invalidateIntrinsicContentSize()
+                }
+            } catch {
+            }
+        }
     }
     
     required init?(coder: NSCoder) {

Tusker/Screens/Large Image/LargeImageViewController.swift

@@ -48,6 +48,7 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
     
     private var prevZoomScale: CGFloat?
     private var isGrayscale = false
+    private var contentViewSizeObservation: NSKeyValueObservation?
     
     var isInteractivelyAnimatingDismissal: Bool = false {
         didSet {
@@ -127,6 +128,9 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
             contentViewLeadingConstraint,
             contentViewTopConstraint,
         ])
+        contentViewSizeObservation = (contentView as UIView).observe(\.bounds, changeHandler: { [unowned self] _, _ in
+            self.centerImage()
+        })
     }
     
     private func setupControls() {
@@ -259,8 +263,6 @@ class LargeImageViewController: UIViewController, UIScrollViewDelegate, LargeIma
     }
     
     func scrollViewDidZoom(_ scrollView: UIScrollView) {
-        centerImage()
-        
         let prevZoomScale = self.prevZoomScale ?? scrollView.minimumZoomScale
         if scrollView.zoomScale <= scrollView.minimumZoomScale {
             setControlsVisible(true, animated: true)