fix: asset_viewer page viewing experience (#20889)

* fix: zoomed in effect on swiped when bottom sheet is open

* fix: memory leaked

* fix: asset out of range when swiping in asset_viewer

mobile/lib/domain/services/timeline.service.dart

@@ -169,6 +169,36 @@ class TimelineService {
     return _buffer.elementAt(index - _bufferOffset);
   }
 
+  /// Gets an asset at the given index, automatically loading the buffer if needed.
+  /// This is an async version that can handle out-of-range indices by loading the appropriate buffer.
+  Future<BaseAsset?> getAssetAsync(int index) async {
+    if (index < 0 || index >= _totalAssets) {
+      return null;
+    }
+
+    if (hasRange(index, 1)) {
+      return _buffer.elementAt(index - _bufferOffset);
+    }
+
+    // Load the buffer containing the requested index
+    try {
+      final assets = await loadAssets(index, 1);
+      return assets.isNotEmpty ? assets.first : null;
+    } catch (e) {
+      return null;
+    }
+  }
+
+  /// Safely gets an asset at the given index without throwing a RangeError.
+  /// Returns null if the index is out of bounds or not currently in the buffer.
+  /// For automatic buffer loading, use getAssetAsync instead.
+  BaseAsset? getAssetSafe(int index) {
+    if (index < 0 || index >= _totalAssets || !hasRange(index, 1)) {
+      return null;
+    }
+    return _buffer.elementAt(index - _bufferOffset);
+  }
+
   Future<void> dispose() async {
     await _bucketSubscription?.cancel();
     _bucketSubscription = null;

mobile/lib/presentation/widgets/asset_viewer/asset_viewer.page.dart

@@ -127,20 +127,21 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
     _delayedOperations.clear();
   }
 
-  // This is used to calculate the scale of the asset when the bottom sheet is showing.
-  // It is a small increment to ensure that the asset is slightly zoomed in when the
-  // bottom sheet is showing, which emulates the zoom effect.
-  double get _getScaleForBottomSheet => (viewController?.prevValue.scale ?? viewController?.value.scale ?? 1.0) + 0.01;
-
   double _getVerticalOffsetForBottomSheet(double extent) =>
       (context.height * extent) - (context.height * _kBottomSheetMinimumExtent);
 
   Future<void> _precacheImage(int index) async {
-    if (!mounted || index < 0 || index >= totalAssets) {
+    if (!mounted) {
+      return;
+    }
+
+    final timelineService = ref.read(timelineServiceProvider);
+    final asset = await timelineService.getAssetAsync(index);
+
+    if (asset == null || !mounted) {
       return;
     }
 
-    final asset = ref.read(timelineServiceProvider).getAsset(index);
     final screenSize = Size(context.width, context.height);
 
     // Precache both thumbnail and full image for smooth transitions
@@ -152,8 +153,15 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
     );
   }
 
-  void _onAssetChanged(int index) {
-    final asset = ref.read(timelineServiceProvider).getAsset(index);
+  void _onAssetChanged(int index) async {
+    // Validate index bounds and try to get asset, loading buffer if needed
+    final timelineService = ref.read(timelineServiceProvider);
+    final asset = await timelineService.getAssetAsync(index);
+
+    if (asset == null) {
+      return;
+    }
+
     // Always holds the current asset from the timeline
     ref.read(assetViewerProvider.notifier).setAsset(asset);
     // The currentAssetNotifier actually holds the current asset that is displayed
@@ -217,19 +225,15 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
       final verticalOffset =
           (context.height * bottomSheetController.size) - (context.height * _kBottomSheetMinimumExtent);
       controller.position = Offset(0, -verticalOffset);
+      // Apply the zoom effect when the bottom sheet is showing
+      initialScale = controller.scale;
+      controller.scale = (controller.scale ?? 1.0) + 0.01;
     }
   }
 
   void _onPageChanged(int index, PhotoViewControllerBase? controller) {
     _onAssetChanged(index);
     viewController = controller;
-
-    // If the bottom sheet is showing, we need to adjust scale the asset to
-    // emulate the zoom effect
-    if (showingBottomSheet) {
-      initialScale = controller?.scale;
-      controller?.scale = _getScaleForBottomSheet;
-    }
   }
 
   void _onDragStart(
@@ -412,16 +416,22 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
     }
   }
 
-  void _onAssetReloadEvent() {
-    setState(() {
-      final index = pageController.page?.round() ?? 0;
-      final newAsset = ref.read(timelineServiceProvider).getAsset(index);
-      final currentAsset = ref.read(currentAssetNotifier);
-      // Do not reload / close the bottom sheet if the asset has not changed
-      if (newAsset.heroTag == currentAsset?.heroTag) {
-        return;
-      }
+  void _onAssetReloadEvent() async {
+    final index = pageController.page?.round() ?? 0;
+    final timelineService = ref.read(timelineServiceProvider);
+    final newAsset = await timelineService.getAssetAsync(index);
 
+    if (newAsset == null) {
+      return;
+    }
+
+    final currentAsset = ref.read(currentAssetNotifier);
+    // Do not reload / close the bottom sheet if the asset has not changed
+    if (newAsset.heroTag == currentAsset?.heroTag) {
+      return;
+    }
+
+    setState(() {
       _onAssetChanged(pageController.page!.round());
       sheetCloseController?.close();
     });
@@ -430,7 +440,7 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
   void _openBottomSheet(BuildContext ctx, {double extent = _kBottomSheetMinimumExtent}) {
     ref.read(assetViewerProvider.notifier).setBottomSheet(true);
     initialScale = viewController?.scale;
-    viewController?.updateMultiple(scale: _getScaleForBottomSheet);
+    // viewController?.updateMultiple(scale: (viewController?.scale ?? 1.0) + 0.01);
     previousExtent = _kBottomSheetMinimumExtent;
     sheetCloseController = showBottomSheet(
       context: ctx,
@@ -468,16 +478,29 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
   }
 
   Widget _placeholderBuilder(BuildContext ctx, ImageChunkEvent? progress, int index) {
-    BaseAsset asset = ref.read(timelineServiceProvider).getAsset(index);
+    final timelineService = ref.read(timelineServiceProvider);
+    final asset = timelineService.getAssetSafe(index);
+
+    // If asset is not available in buffer, show a loading container
+    if (asset == null) {
+      return Container(
+        width: double.infinity,
+        height: double.infinity,
+        color: backgroundColor,
+        child: const Center(child: CircularProgressIndicator()),
+      );
+    }
+
+    BaseAsset displayAsset = asset;
     final stackChildren = ref.read(stackChildrenNotifier(asset)).valueOrNull;
     if (stackChildren != null && stackChildren.isNotEmpty) {
-      asset = stackChildren.elementAt(ref.read(assetViewerProvider.select((s) => s.stackIndex)));
+      displayAsset = stackChildren.elementAt(ref.read(assetViewerProvider.select((s) => s.stackIndex)));
     }
     return Container(
       width: double.infinity,
       height: double.infinity,
       color: backgroundColor,
-      child: Thumbnail(asset: asset, fit: BoxFit.contain),
+      child: Thumbnail(asset: displayAsset, fit: BoxFit.contain),
     );
   }
 
@@ -493,18 +516,34 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
 
   PhotoViewGalleryPageOptions _assetBuilder(BuildContext ctx, int index) {
     scaffoldContext ??= ctx;
-    BaseAsset asset = ref.read(timelineServiceProvider).getAsset(index);
+    final timelineService = ref.read(timelineServiceProvider);
+    final asset = timelineService.getAssetSafe(index);
+
+    // If asset is not available in buffer, return a placeholder
+    if (asset == null) {
+      return PhotoViewGalleryPageOptions.customChild(
+        heroAttributes: PhotoViewHeroAttributes(tag: 'loading_$index'),
+        child: Container(
+          width: ctx.width,
+          height: ctx.height,
+          color: backgroundColor,
+          child: const Center(child: CircularProgressIndicator()),
+        ),
+      );
+    }
+
+    BaseAsset displayAsset = asset;
     final stackChildren = ref.read(stackChildrenNotifier(asset)).valueOrNull;
     if (stackChildren != null && stackChildren.isNotEmpty) {
-      asset = stackChildren.elementAt(ref.read(assetViewerProvider.select((s) => s.stackIndex)));
+      displayAsset = stackChildren.elementAt(ref.read(assetViewerProvider.select((s) => s.stackIndex)));
     }
 
     final isPlayingMotionVideo = ref.read(isPlayingMotionVideoProvider);
-    if (asset.isImage && !isPlayingMotionVideo) {
-      return _imageBuilder(ctx, asset);
+    if (displayAsset.isImage && !isPlayingMotionVideo) {
+      return _imageBuilder(ctx, displayAsset);
     }
 
-    return _videoBuilder(ctx, asset);
+    return _videoBuilder(ctx, displayAsset);
   }
 
   PhotoViewGalleryPageOptions _imageBuilder(BuildContext ctx, BaseAsset asset) {
@@ -515,8 +554,6 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
       heroAttributes: PhotoViewHeroAttributes(tag: '${asset.heroTag}_$heroOffset'),
       filterQuality: FilterQuality.high,
       tightMode: true,
-      initialScale: PhotoViewComputedScale.contained * 0.999,
-      minScale: PhotoViewComputedScale.contained * 0.999,
       disableScaleGestures: showingBottomSheet,
       onDragStart: _onDragStart,
       onDragUpdate: _onDragUpdate,
@@ -545,9 +582,7 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
       onTapDown: _onTapDown,
       heroAttributes: PhotoViewHeroAttributes(tag: '${asset.heroTag}_$heroOffset'),
       filterQuality: FilterQuality.high,
-      initialScale: PhotoViewComputedScale.contained * 0.99,
       maxScale: 1.0,
-      minScale: PhotoViewComputedScale.contained * 0.99,
       basePosition: Alignment.center,
       child: SizedBox(
         width: ctx.width,

mobile/lib/presentation/widgets/images/local_image_provider.dart

@@ -11,7 +11,6 @@ import 'package:immich_mobile/domain/services/setting.service.dart';
 import 'package:immich_mobile/extensions/codec_extensions.dart';
 import 'package:immich_mobile/infrastructure/repositories/asset_media.repository.dart';
 import 'package:immich_mobile/infrastructure/repositories/storage.repository.dart';
-import 'package:immich_mobile/presentation/widgets/images/image_provider.dart';
 import 'package:immich_mobile/presentation/widgets/images/one_frame_multi_image_stream_completer.dart';
 import 'package:immich_mobile/presentation/widgets/timeline/constants.dart';
 import 'package:immich_mobile/providers/image/cache/thumbnail_image_cache_manager.dart';
@@ -107,7 +106,6 @@ class LocalFullImageProvider extends ImageProvider<LocalFullImageProvider> {
   ImageStreamCompleter loadImage(LocalFullImageProvider key, ImageDecoderCallback decode) {
     return OneFramePlaceholderImageStreamCompleter(
       _codec(key, decode),
-      initialImage: getCachedImage(LocalThumbProvider(id: key.id, updatedAt: key.updatedAt)),
       informationCollector: () => <DiagnosticsNode>[
         DiagnosticsProperty<String>('Id', key.id),
         DiagnosticsProperty<DateTime>('Updated at', key.updatedAt),
@@ -117,13 +115,30 @@ class LocalFullImageProvider extends ImageProvider<LocalFullImageProvider> {
   }
 
   // Streams in each stage of the image as we ask for it
-  Stream<ImageInfo> _codec(LocalFullImageProvider key, ImageDecoderCallback decode) {
+  Stream<ImageInfo> _codec(LocalFullImageProvider key, ImageDecoderCallback decode) async* {
     try {
-      return switch (key.type) {
+      // First, yield the thumbnail image from LocalThumbProvider
+      final thumbProvider = LocalThumbProvider(id: key.id, updatedAt: key.updatedAt);
+      try {
+        final thumbCodec = await thumbProvider._codec(
+          thumbProvider,
+          thumbProvider.cacheManager ?? ThumbnailImageCacheManager(),
+          decode,
+        );
+        final thumbImageInfo = await thumbCodec.getImageInfo();
+        yield thumbImageInfo;
+      } catch (_) {}
+
+      // Then proceed with the main image loading stream
+      final mainStream = switch (key.type) {
         AssetType.image => _decodeProgressive(key, decode),
         AssetType.video => _getThumbnailCodec(key, decode),
         _ => throw StateError('Unsupported asset type ${key.type}'),
       };
+
+      await for (final imageInfo in mainStream) {
+        yield imageInfo;
+      }
     } catch (error, stack) {
       Logger('ImmichLocalImageProvider').severe('Error loading local image ${key.id}', error, stack);
       throw const ImageLoadingException('Could not load image from local storage');

mobile/lib/widgets/photo_view/src/photo_view_wrappers.dart

@@ -86,6 +86,7 @@ class _ImageWrapperState extends State<ImageWrapper> {
   Size? _imageSize;
   Object? _lastException;
   StackTrace? _lastStack;
+  bool _didLoadSynchronously = false;
 
   @override
   void dispose() {
@@ -130,9 +131,11 @@ class _ImageWrapperState extends State<ImageWrapper> {
         _loadingProgress = null;
         _lastException = null;
         _lastStack = null;
+
+        _didLoadSynchronously = synchronousCall;
       }
 
-      synchronousCall ? setupCB() : setState(setupCB);
+      synchronousCall && !_didLoadSynchronously ? setupCB() : setState(setupCB);
     }
 
     void handleError(dynamic error, StackTrace? stackTrace) {