fix: incorrect asset viewer scale on image frame update (#25430)

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>

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

@@ -118,7 +118,6 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
   bool dragInProgress = false;
   bool shouldPopOnDrag = false;
   bool assetReloadRequested = false;
-  double? initialScale;
   double previousExtent = _kBottomSheetMinimumExtent;
   Offset dragDownPosition = Offset.zero;
   int totalAssets = 0;
@@ -264,7 +263,6 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
           (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;
     }
   }
@@ -316,7 +314,7 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
     hasDraggedDown = null;
     viewController?.animateMultiple(
       position: initialPhotoViewState.position,
-      scale: initialPhotoViewState.scale,
+      scale: viewController?.initialScale ?? initialPhotoViewState.scale,
       rotation: initialPhotoViewState.rotation,
     );
     ref.read(assetViewerProvider.notifier).setOpacity(255);
@@ -366,8 +364,9 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
     final maxScaleDistance = ctx.height * 0.5;
     final scaleReduction = (distance / maxScaleDistance).clamp(0.0, dragRatio);
     double? updatedScale;
-    if (initialPhotoViewState.scale != null) {
+    double? initialScale = viewController?.initialScale ?? initialPhotoViewState.scale;
-      updatedScale = initialPhotoViewState.scale! * (1.0 - scaleReduction);
+    if (initialScale != null) {
+      updatedScale = initialScale * (1.0 - scaleReduction);
     }
 
     final backgroundOpacity = (255 * (1.0 - (scaleReduction / dragRatio))).round();
@@ -481,8 +480,6 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
 
   void _openBottomSheet(BuildContext ctx, {double extent = _kBottomSheetMinimumExtent, bool activitiesMode = false}) {
     ref.read(assetViewerProvider.notifier).setBottomSheet(true);
-    initialScale = viewController?.scale;
-    // viewController?.updateMultiple(scale: (viewController?.scale ?? 1.0) + 0.01);
     previousExtent = _kBottomSheetMinimumExtent;
     sheetCloseController = showBottomSheet(
       context: ctx,
@@ -504,7 +501,7 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
 
   void _handleSheetClose() {
     viewController?.animateMultiple(position: Offset.zero);
-    viewController?.updateMultiple(scale: initialScale);
+    viewController?.updateMultiple(scale: viewController?.initialScale);
     ref.read(assetViewerProvider.notifier).setBottomSheet(false);
     sheetCloseController = null;
     shouldPopOnDrag = false;

mobile/lib/widgets/photo_view/src/controller/photo_view_controller.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:flutter/widgets.dart';
 import 'package:immich_mobile/widgets/photo_view/src/utils/ignorable_change_notifier.dart';
+import 'package:immich_mobile/widgets/photo_view/src/utils/photo_view_utils.dart';
 
 /// The interface in which controllers will be implemented.
 ///
@@ -62,6 +63,9 @@ abstract class PhotoViewControllerBase<T extends PhotoViewControllerValue> {
   /// The scale factor to transform the child (image or a customChild).
   late double? scale;
 
+  double? get initialScale;
+  ScaleBoundaries? scaleBoundaries;
+
   /// Nevermind this method :D, look away
   void setScaleInvisibly(double? scale);
 
@@ -141,6 +145,9 @@ class PhotoViewController implements PhotoViewControllerBase<PhotoViewController
 
   late StreamController<PhotoViewControllerValue> _outputCtrl;
 
+  @override
+  ScaleBoundaries? scaleBoundaries;
+
   late void Function(Offset)? _animatePosition;
   late void Function(double)? _animateScale;
   late void Function(double)? _animateRotation;
@@ -311,4 +318,7 @@ class PhotoViewController implements PhotoViewControllerBase<PhotoViewController
     }
     _valueNotifier.value = newValue;
   }
+
+  @override
+  double? get initialScale => scaleBoundaries?.initialScale ?? initial.scale;
 }

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

@@ -108,6 +108,17 @@ class _ImageWrapperState extends State<ImageWrapper> {
     }
   }
 
+  // Should be called only when _imageSize is not null
+  ScaleBoundaries get scaleBoundaries {
+    return ScaleBoundaries(
+      widget.minScale ?? 0.0,
+      widget.maxScale ?? double.infinity,
+      widget.initialScale ?? PhotoViewComputedScale.contained,
+      widget.outerSize,
+      _imageSize!,
+    );
+  }
+
   // retrieve image from the provider
   void _resolveImage() {
     final ImageStream newStream = widget.imageProvider.resolve(const ImageConfiguration());
@@ -133,6 +144,7 @@ class _ImageWrapperState extends State<ImageWrapper> {
         _lastStack = null;
 
         _didLoadSynchronously = synchronousCall;
+        widget.controller.scaleBoundaries = scaleBoundaries;
       }
 
       synchronousCall && !_didLoadSynchronously ? setupCB() : setState(setupCB);
@@ -204,14 +216,6 @@ class _ImageWrapperState extends State<ImageWrapper> {
       );
     }
 
-    final scaleBoundaries = ScaleBoundaries(
-      widget.minScale ?? 0.0,
-      widget.maxScale ?? double.infinity,
-      widget.initialScale ?? PhotoViewComputedScale.contained,
-      widget.outerSize,
-      _imageSize!,
-    );
-
     return PhotoViewCore(
       imageProvider: widget.imageProvider,
       backgroundDecoration: widget.backgroundDecoration,