Minor quicklook fixes. (#6112)

* Only show a spinner when opening the media viewer is slow

* Keep a sent local echo's page in the media viewer

* Fix the caption visibility.

---------

Co-authored-by: Stefan Ceriu <stefan.ceriu@gmail.com>
Co-authored-by: Matthew Hodgson <matthew@matrix.org>

ElementX/Sources/Screens/FilePreviewScreen/View/TimelineMediaPreviewController.swift

@@ -73,6 +73,11 @@ class TimelineMediaPreviewController: QLPreviewController {
         
         super.init(nibName: nil, bundle: nil)
         
+        headerHostingController.rootView.onMoveToWindow = { [weak self] in
+            guard #available(iOS 26, *) else { return }
+            self?.updateCaptionVisibility()
+        }
+        
         view.addSubview(captionView)
         // Constraints added later as the toolbar isn't available yet.
         
@@ -128,11 +133,9 @@ class TimelineMediaPreviewController: QLPreviewController {
         super.viewWillLayoutSubviews()
         
         if let bottomBarItemsContainer {
-            // Using the toolbar's visibility doesn't work so check its frame.
-            captionView.isHidden = if #available(iOS 26, *) {
-                navigationBar?.topItem?.leftBarButtonItem?.frame(in: view) == nil
-            } else {
-                bottomBarItemsContainer.frame.minY >= view.frame.maxY
+            if #unavailable(iOS 26) {
+                // Using the toolbar's visibility doesn't work so check its frame.
+                captionView.isHidden = bottomBarItemsContainer.frame.minY >= view.frame.maxY
             }
             
             if captionView.constraints.isEmpty {
@@ -176,6 +179,15 @@ class TimelineMediaPreviewController: QLPreviewController {
         barButtonTimer = nil
     }
     
+    @available(iOS 26, *)
+    private func updateCaptionVisibility() {
+        // The caption should be hidden alongside the header.
+        let isHeaderHidden = headerHostingController.view.window == nil
+        if captionView.isHidden != isHeaderHidden {
+            captionView.isHidden = isHeaderHidden
+        }
+    }
+    
     private func updateBarButtons() {
         guard let topItem = navigationBar?.topItem else { return }
         
@@ -306,11 +318,20 @@ class TimelineMediaPreviewController: QLPreviewController {
 
 private struct HeaderView: View {
     @ObservedObject var context: TimelineMediaPreviewViewModel.Context
+    /// Called whenever the header is added or removed from a window.
+    var onMoveToWindow: () -> Void = { }
+    
     private var currentItem: TimelineMediaPreviewItem {
         context.viewState.currentItem
     }
     
     var body: some View {
+        content
+            .background(WindowTrackingView(onMoveToWindow: onMoveToWindow))
+    }
+    
+    @ViewBuilder
+    private var content: some View {
         if let mediaItem = currentItem.mediaItem {
             VStack(spacing: 0) {
                 Text(mediaItem.sender.displayName ?? mediaItem.sender.id)
@@ -475,6 +496,31 @@ private struct DownloadIndicatorView: View {
 
 // MARK: - Helpers
 
+/// An invisible view that reports when it is added to or removed from a window.
+private struct WindowTrackingView: UIViewRepresentable {
+    let onMoveToWindow: () -> Void
+    
+    func makeUIView(context: Context) -> TrackingView {
+        let view = TrackingView()
+        view.isUserInteractionEnabled = false
+        view.onMoveToWindow = onMoveToWindow
+        return view
+    }
+    
+    func updateUIView(_ uiView: TrackingView, context: Context) {
+        uiView.onMoveToWindow = onMoveToWindow
+    }
+    
+    class TrackingView: UIView {
+        var onMoveToWindow: (() -> Void)?
+        
+        override func didMoveToWindow() {
+            super.didMoveToWindow()
+            onMoveToWindow?()
+        }
+    }
+}
+
 private extension UIView {
     func firstScrollView() -> UIScrollView? {
         for view in subviews {