keep alive face thumbnail when scrolling fast

mobile/apps/photos/lib/ui/viewer/people/person_face_widget.dart

@@ -21,6 +21,7 @@ class PersonFaceWidget extends StatefulWidget {
   final String? clusterID;
   final bool useFullFile;
   final VoidCallback? onErrorCallback;
+  final bool keepAlive;
 
   // PersonFaceWidget constructor checks that both personId and clusterID are not null
   // and that the file is not null
@@ -29,6 +30,7 @@ class PersonFaceWidget extends StatefulWidget {
     this.clusterID,
     this.useFullFile = true,
     this.onErrorCallback,
+    this.keepAlive = false,
     super.key,
   }) : assert(
           personId != null || clusterID != null,
@@ -39,12 +41,16 @@ class PersonFaceWidget extends StatefulWidget {
   State<PersonFaceWidget> createState() => _PersonFaceWidgetState();
 }
 
-class _PersonFaceWidgetState extends State<PersonFaceWidget> {
+class _PersonFaceWidgetState extends State<PersonFaceWidget>
+    with AutomaticKeepAliveClientMixin {
   Future<Uint8List?>? faceCropFuture;
   EnteFile? fileForFaceCrop;
 
   bool get isPerson => widget.personId != null;
 
+  @override
+  bool get wantKeepAlive => widget.keepAlive;
+
   @override
   void initState() {
     super.initState();
@@ -64,6 +70,10 @@ class _PersonFaceWidgetState extends State<PersonFaceWidget> {
 
   @override
   Widget build(BuildContext context) {
+    super.build(
+      context,
+    ); // Calling super.build for AutomaticKeepAliveClientMixin
+
     return FutureBuilder<Uint8List?>(
       future: faceCropFuture,
       builder: (context, snapshot) {

mobile/apps/photos/lib/ui/viewer/search/result/people_section_all_page.dart

@@ -95,12 +95,14 @@ class SelectablePersonSearchExample extends StatelessWidget {
   final GenericSearchResult searchResult;
   final double size;
   final SelectedPeople selectedPeople;
+  final bool isDefaultFace;
 
   const SelectablePersonSearchExample({
     super.key,
     required this.searchResult,
     required this.selectedPeople,
     this.size = 102,
+    this.isDefaultFace = false,
   });
 
   void _handleTap(BuildContext context) {
@@ -192,7 +194,10 @@ class SelectablePersonSearchExample extends StatelessWidget {
                                 searchResult.previewThumbnail()!,
                                 shouldShowSyncStatus: false,
                               )
-                            : FaceSearchResult(searchResult);
+                            : FaceSearchResult(
+                                searchResult,
+                                isDefaultFace: isDefaultFace,
+                              );
                       } else {
                         child = const NoThumbnailWidget(
                           addBorder: false,
@@ -301,8 +306,13 @@ class SelectablePersonSearchExample extends StatelessWidget {
 
 class FaceSearchResult extends StatelessWidget {
   final SearchResult searchResult;
+  final bool isDefaultFace;
 
-  const FaceSearchResult(this.searchResult, {super.key});
+  const FaceSearchResult(
+    this.searchResult, {
+    super.key,
+    this.isDefaultFace = false,
+  });
 
   @override
   Widget build(BuildContext context) {
@@ -313,6 +323,7 @@ class FaceSearchResult extends StatelessWidget {
       key: params.containsKey(kPersonWidgetKey)
           ? ValueKey(params[kPersonWidgetKey])
           : ValueKey(params[kPersonParamID] ?? params[kClusterParamId]),
+      keepAlive: isDefaultFace,
     );
   }
 }
@@ -486,6 +497,7 @@ class _PeopleSectionAllWidgetState extends State<PeopleSectionAllWidget> {
                               searchResult: normalFaces[index],
                               size: itemSize,
                               selectedPeople: widget.selectedPeople!,
+                              isDefaultFace: true,
                             )
                           : PersonSearchExample(
                               searchResult: normalFaces[index],
@@ -525,6 +537,7 @@ class _PeopleSectionAllWidgetState extends State<PeopleSectionAllWidget> {
                                 searchResult: extraFaces[index],
                                 size: itemSize,
                                 selectedPeople: widget.selectedPeople!,
+                                isDefaultFace: false,
                               )
                             : PersonSearchExample(
                                 searchResult: extraFaces[index],