reviewed collection model to work with source + lenses

lib/labs/sliver_transition_grid_delegate.dart

@@ -164,7 +164,7 @@ class SliverTransitionGridTileLayout extends SliverGridLayout {
 
     if (t != 0) {
       final index = childCount - 1;
-      var maxScrollOffset = lerpDouble(_getScrollOffset(index, floor), _getScrollOffset(index, ceil), t) + current.mainAxisStride;
+      final maxScrollOffset = lerpDouble(_getScrollOffset(index, floor), _getScrollOffset(index, ceil), t) + current.mainAxisStride;
       return maxScrollOffset;
     }
 

lib/model/collection_filters.dart

@@ -0,0 +1,39 @@
+import 'package:aves/model/image_entry.dart';
+
+abstract class CollectionFilter {
+  const CollectionFilter();
+
+  bool filter(ImageEntry entry);
+}
+
+class AlbumFilter extends CollectionFilter {
+  final String album;
+
+  const AlbumFilter(this.album);
+
+  @override
+  bool filter(ImageEntry entry) => entry.directory == album;
+}
+
+class TagFilter extends CollectionFilter {
+  final String tag;
+
+  const TagFilter(this.tag);
+
+  @override
+  bool filter(ImageEntry entry) => entry.xmpSubjects.contains(tag);
+}
+
+class VideoFilter extends CollectionFilter {
+  @override
+  bool filter(ImageEntry entry) => entry.isVideo;
+}
+
+class MetadataFilter extends CollectionFilter {
+  final String value;
+
+  const MetadataFilter(this.value);
+
+  @override
+  bool filter(ImageEntry entry) => entry.search(value);
+}

lib/model/collection_lens.dart

@@ -0,0 +1,157 @@
+import 'dart:async';
+import 'dart:collection';
+
+import 'package:aves/model/collection_filters.dart';
+import 'package:aves/model/collection_source.dart';
+import 'package:aves/model/image_entry.dart';
+import 'package:collection/collection.dart';
+import 'package:flutter/foundation.dart';
+
+class CollectionLens with ChangeNotifier {
+  final CollectionSource source;
+  final List<CollectionFilter> filters;
+  GroupFactor groupFactor;
+  SortFactor sortFactor;
+
+  List<ImageEntry> _filteredEntries;
+  List<StreamSubscription> _subscriptions = [];
+
+  Map<dynamic, List<ImageEntry>> sections = Map.unmodifiable({});
+
+  CollectionLens({
+    @required this.source,
+    List<CollectionFilter> filters,
+    GroupFactor groupFactor,
+    SortFactor sortFactor,
+  })  : this.filters = filters ?? [],
+        this.groupFactor = groupFactor ?? GroupFactor.month,
+        this.sortFactor = sortFactor ?? SortFactor.date {
+    _subscriptions.add(source.eventBus.on<EntryAddedEvent>().listen((e) => onSourceChanged()));
+    _subscriptions.add(source.eventBus.on<EntryRemovedEvent>().listen((e) => onSourceChanged()));
+    _subscriptions.add(source.eventBus.on<MetadataChangedEvent>().listen((e) => onMetadataChanged()));
+    onSourceChanged();
+  }
+
+  factory CollectionLens.empty() {
+    return CollectionLens(
+      source: CollectionSource(),
+    );
+  }
+
+  factory CollectionLens.from(CollectionLens lens, CollectionFilter filter) {
+    return CollectionLens(
+      source: lens.source,
+      filters: [...lens.filters, filter],
+      groupFactor: lens.groupFactor,
+      sortFactor: lens.sortFactor,
+    );
+  }
+
+  @override
+  void dispose() {
+    _subscriptions
+      ..forEach((sub) => sub.cancel())
+      ..clear();
+    _subscriptions = null;
+    super.dispose();
+  }
+
+  bool get isEmpty => _filteredEntries.isEmpty;
+
+  int get imageCount => _filteredEntries.where((entry) => !entry.isVideo).length;
+
+  int get videoCount => _filteredEntries.where((entry) => entry.isVideo).length;
+
+  List<ImageEntry> get sortedEntries => List.unmodifiable(sections.entries.expand((e) => e.value));
+
+  void sort(SortFactor sortFactor) {
+    this.sortFactor = sortFactor;
+    updateSections();
+  }
+
+  void group(GroupFactor groupFactor) {
+    this.groupFactor = groupFactor;
+    updateSections();
+  }
+
+  void updateSections() {
+    _applySort();
+    switch (sortFactor) {
+      case SortFactor.date:
+        switch (groupFactor) {
+          case GroupFactor.album:
+            sections = Map.unmodifiable(groupBy(_filteredEntries, (entry) => entry.directory));
+            break;
+          case GroupFactor.month:
+            sections = Map.unmodifiable(groupBy(_filteredEntries, (entry) => entry.monthTaken));
+            break;
+          case GroupFactor.day:
+            sections = Map.unmodifiable(groupBy(_filteredEntries, (entry) => entry.dayTaken));
+            break;
+        }
+        break;
+      case SortFactor.size:
+        sections = Map.unmodifiable(Map.fromEntries([
+          MapEntry(null, _filteredEntries),
+        ]));
+        break;
+      case SortFactor.name:
+        final byAlbum = groupBy(_filteredEntries, (ImageEntry entry) => entry.directory);
+        final albums = byAlbum.keys.toSet();
+        final compare = (a, b) {
+          final ua = CollectionSource.getUniqueAlbumName(a, albums);
+          final ub = CollectionSource.getUniqueAlbumName(b, albums);
+          return compareAsciiUpperCase(ua, ub);
+        };
+        sections = Map.unmodifiable(SplayTreeMap.from(byAlbum, compare));
+        break;
+    }
+    notifyListeners();
+  }
+
+  void _applySort() {
+    switch (sortFactor) {
+      case SortFactor.date:
+        _filteredEntries.sort((a, b) => b.bestDate.compareTo(a.bestDate));
+        break;
+      case SortFactor.size:
+        _filteredEntries.sort((a, b) => b.sizeBytes.compareTo(a.sizeBytes));
+        break;
+      case SortFactor.name:
+        _filteredEntries.sort((a, b) => compareAsciiUpperCase(a.title, b.title));
+        break;
+    }
+  }
+
+//  void add(ImageEntry entry) => _rawEntries.add(entry);
+//
+//  Future<bool> delete(ImageEntry entry) async {
+//    final success = await ImageFileService.delete(entry);
+//    if (success) {
+//      _rawEntries.remove(entry);
+//      updateSections();
+//    }
+//    return success;
+//  }
+
+  void onSourceChanged() {
+    _applyFilters();
+    updateSections();
+  }
+
+  void _applyFilters() {
+    final rawEntries = source.entries;
+    _filteredEntries = List.of(filters.isEmpty ? rawEntries : rawEntries.where((entry) => filters.fold(true, (prev, filter) => prev && filter.filter(entry))));
+    updateSections();
+  }
+
+  void onMetadataChanged() {
+    _applyFilters();
+    // metadata dates impact sorting and grouping
+    updateSections();
+  }
+}
+
+enum SortFactor { date, size, name }
+
+enum GroupFactor { album, month, day }

lib/model/collection_source.dart

@@ -1,131 +1,30 @@
-import 'dart:collection';
-
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/model/image_file_service.dart';
 import 'package:aves/model/image_metadata.dart';
 import 'package:aves/model/metadata_db.dart';
 import 'package:collection/collection.dart';
+import 'package:event_bus/event_bus.dart';
 import 'package:flutter/foundation.dart';
 import 'package:path/path.dart';
 
-class ImageCollection with ChangeNotifier {
+class CollectionSource {
   final List<ImageEntry> _rawEntries;
-  Map<dynamic, List<ImageEntry>> sections = Map.unmodifiable({});
+  final EventBus _eventBus = EventBus();
-  GroupFactor groupFactor = GroupFactor.month;
+
-  SortFactor sortFactor = SortFactor.date;
   List<String> sortedAlbums = List.unmodifiable(const Iterable.empty());
   List<String> sortedTags = List.unmodifiable(const Iterable.empty());
 
-  ImageCollection({
+  List<ImageEntry> get entries => List.unmodifiable(_rawEntries);
-    @required List<ImageEntry> entries,
-    this.groupFactor,
-    this.sortFactor,
-  }) : _rawEntries = entries {
-    if (_rawEntries.isNotEmpty) updateSections();
-  }
 
-  int get imageCount => _rawEntries.where((entry) => !entry.isVideo).length;
+  EventBus get eventBus => _eventBus;
-
-  int get videoCount => _rawEntries.where((entry) => entry.isVideo).length;
 
   int get albumCount => sortedAlbums.length;
 
   int get tagCount => sortedTags.length;
 
-  List<ImageEntry> get sortedEntries => List.unmodifiable(sections.entries.expand((e) => e.value));
+  CollectionSource({
-
+    List<ImageEntry> entries,
-  void sort(SortFactor sortFactor) {
+  }) : _rawEntries = entries ?? [];
-    this.sortFactor = sortFactor;
-    updateSections();
-  }
-
-  void group(GroupFactor groupFactor) {
-    this.groupFactor = groupFactor;
-    updateSections();
-  }
-
-  void updateSections() {
-    _applySort();
-    switch (sortFactor) {
-      case SortFactor.date:
-        switch (groupFactor) {
-          case GroupFactor.album:
-            sections = Map.unmodifiable(groupBy(_rawEntries, (entry) => entry.directory));
-            break;
-          case GroupFactor.month:
-            sections = Map.unmodifiable(groupBy(_rawEntries, (entry) => entry.monthTaken));
-            break;
-          case GroupFactor.day:
-            sections = Map.unmodifiable(groupBy(_rawEntries, (entry) => entry.dayTaken));
-            break;
-        }
-        break;
-      case SortFactor.size:
-        sections = Map.unmodifiable(Map.fromEntries([
-          MapEntry(null, _rawEntries),
-        ]));
-        break;
-      case SortFactor.name:
-        final byAlbum = groupBy(_rawEntries, (ImageEntry entry) => entry.directory);
-        final albums = byAlbum.keys.toSet();
-        final compare = (a, b) {
-          final ua = getUniqueAlbumName(a, albums);
-          final ub = getUniqueAlbumName(b, albums);
-          return compareAsciiUpperCase(ua, ub);
-        };
-        sections = Map.unmodifiable(SplayTreeMap.from(byAlbum, compare));
-        break;
-    }
-    notifyListeners();
-  }
-
-  void _applySort() {
-    switch (sortFactor) {
-      case SortFactor.date:
-        _rawEntries.sort((a, b) => b.bestDate.compareTo(a.bestDate));
-        break;
-      case SortFactor.size:
-        _rawEntries.sort((a, b) => b.sizeBytes.compareTo(a.sizeBytes));
-        break;
-      case SortFactor.name:
-        _rawEntries.sort((a, b) => compareAsciiUpperCase(a.title, b.title));
-        break;
-    }
-  }
-
-  void add(ImageEntry entry) => _rawEntries.add(entry);
-
-  Future<bool> delete(ImageEntry entry) async {
-    final success = await ImageFileService.delete(entry);
-    if (success) {
-      _rawEntries.remove(entry);
-      updateSections();
-    }
-    return success;
-  }
-
-  void updateAlbums() {
-    final albums = _rawEntries.map((entry) => entry.directory).toSet();
-    final sorted = albums.toList()
-      ..sort((a, b) {
-        final ua = getUniqueAlbumName(a, albums);
-        final ub = getUniqueAlbumName(b, albums);
-        return compareAsciiUpperCase(ua, ub);
-      });
-    sortedAlbums = List.unmodifiable(sorted);
-  }
-
-  void updateTags() {
-    final tags = _rawEntries.expand((entry) => entry.xmpSubjects).toSet();
-    final sorted = tags.toList()..sort(compareAsciiUpperCase);
-    sortedTags = List.unmodifiable(sorted);
-  }
-
-  void onMetadataChanged() {
-    // metadata dates impact sorting and grouping
-    updateSections();
-    updateTags();
-  }
 
   Future<void> loadCatalogMetadata() async {
     final stopwatch = Stopwatch()..start();
@@ -171,6 +70,11 @@ class ImageCollection with ChangeNotifier {
     debugPrint('$runtimeType catalogEntries complete in ${stopwatch.elapsed.inSeconds}s with ${newMetadata.length} new entries');
   }
 
+  void onMetadataChanged() {
+    updateTags();
+    eventBus.fire(MetadataChangedEvent());
+  }
+
   Future<void> locateEntries() async {
     final stopwatch = Stopwatch()..start();
     final unlocatedEntries = _rawEntries.where((entry) => entry.hasGps && !entry.isLocated).toList();
@@ -189,15 +93,43 @@ class ImageCollection with ChangeNotifier {
     debugPrint('$runtimeType locateEntries complete in ${stopwatch.elapsed.inMilliseconds}ms');
   }
 
-  ImageCollection filter(bool Function(ImageEntry) filter) {
+  void updateAlbums() {
-    return ImageCollection(
+    final albums = _rawEntries.map((entry) => entry.directory).toSet();
-      entries: _rawEntries.where(filter).toList(),
+    final sorted = albums.toList()
-      groupFactor: groupFactor,
+      ..sort((a, b) {
-      sortFactor: sortFactor,
+        final ua = getUniqueAlbumName(a, albums);
-    );
+        final ub = getUniqueAlbumName(b, albums);
+        return compareAsciiUpperCase(ua, ub);
+      });
+    sortedAlbums = List.unmodifiable(sorted);
   }
 
-  String getUniqueAlbumName(String album, Iterable<String> albums) {
+  void updateTags() {
+    final tags = _rawEntries.expand((entry) => entry.xmpSubjects).toSet();
+    final sorted = tags.toList()..sort(compareAsciiUpperCase);
+    sortedTags = List.unmodifiable(sorted);
+  }
+
+  void add(ImageEntry entry) {
+    _rawEntries.add(entry);
+    eventBus.fire(EntryAddedEvent(entry));
+  }
+
+  void addAll(Iterable<ImageEntry> entries) {
+    _rawEntries.addAll(entries);
+    eventBus.fire(const EntryAddedEvent());
+  }
+
+  Future<bool> delete(ImageEntry entry) async {
+    final success = await ImageFileService.delete(entry);
+    if (success) {
+      _rawEntries.remove(entry);
+      eventBus.fire(EntryRemovedEvent(entry));
+    }
+    return success;
+  }
+
+  static String getUniqueAlbumName(String album, Iterable<String> albums) {
     final otherAlbums = albums.where((item) => item != album);
     final parts = album.split(separator);
     int partCount = 0;
@@ -209,6 +141,16 @@ class ImageCollection with ChangeNotifier {
   }
 }
 
-enum SortFactor { date, size, name }
+class MetadataChangedEvent {}
 
-enum GroupFactor { album, month, day }
+class EntryAddedEvent {
+  final ImageEntry entry;
+
+  const EntryAddedEvent([this.entry]);
+}
+
+class EntryRemovedEvent {
+  final ImageEntry entry;
+
+  const EntryRemovedEvent(this.entry);
+}

lib/model/settings.dart

@@ -1,4 +1,4 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:shared_preferences/shared_preferences.dart';

lib/widgets/album/all_collection_drawer.dart

@@ -1,7 +1,8 @@
 import 'dart:ui';
 
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_filters.dart';
-import 'package:aves/model/image_entry.dart';
+import 'package:aves/model/collection_lens.dart';
+import 'package:aves/model/collection_source.dart';
 import 'package:aves/utils/android_file_utils.dart';
 import 'package:aves/utils/color_utils.dart';
 import 'package:aves/widgets/album/filtered_collection_page.dart';
@@ -16,10 +17,11 @@ class AllCollectionDrawer extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final collection = Provider.of<ImageCollection>(context);
+    final collection = Provider.of<CollectionLens>(context);
-    final tags = collection.sortedTags;
+    final source = collection.source;
+    final tags = source.sortedTags;
     final regularAlbums = [], appAlbums = [], specialAlbums = [];
-    for (var album in collection.sortedAlbums) {
+    for (var album in source.sortedAlbums) {
       switch (androidFileUtils.getAlbumType(album)) {
         case AlbumType.Default:
           regularAlbums.add(album);
@@ -37,13 +39,13 @@ class AllCollectionDrawer extends StatelessWidget {
       collection: collection,
       leading: const Icon(OMIcons.videoLibrary),
       title: 'Videos',
-      filter: (entry) => entry.isVideo,
+      filter: VideoFilter(),
     );
     final buildAlbumEntry = (album) => _FilteredCollectionNavTile(
           collection: collection,
           leading: IconUtils.getAlbumIcon(context, album) ?? const Icon(OMIcons.photoAlbum),
-          title: collection.getUniqueAlbumName(album, collection.sortedAlbums),
+          title: CollectionSource.getUniqueAlbumName(album, source.sortedAlbums),
-          filter: (entry) => entry.directory == album,
+          filter: AlbumFilter(album),
         );
     final buildTagEntry = (tag) => _FilteredCollectionNavTile(
           collection: collection,
@@ -52,7 +54,7 @@ class AllCollectionDrawer extends StatelessWidget {
             color: stringToColor(tag),
           ),
           title: tag,
-          filter: (entry) => entry.xmpSubjects.contains(tag),
+          filter: TagFilter(tag),
         );
 
     return Drawer(
@@ -109,12 +111,12 @@ class AllCollectionDrawer extends StatelessWidget {
                         Row(children: [
                           const Icon(OMIcons.photoAlbum),
                           const SizedBox(width: 4),
-                          Text('${collection.albumCount}'),
+                          Text('${source.albumCount}'),
                         ]),
                         Row(children: [
                           const Icon(OMIcons.label),
                           const SizedBox(width: 4),
-                          Text('${collection.tagCount}'),
+                          Text('${source.tagCount}'),
                         ]),
                       ],
                     ),
@@ -147,10 +149,10 @@ class AllCollectionDrawer extends StatelessWidget {
 }
 
 class _FilteredCollectionNavTile extends StatelessWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final Widget leading;
   final String title;
-  final bool Function(ImageEntry) filter;
+  final CollectionFilter filter;
 
   const _FilteredCollectionNavTile({
     @required this.collection,

lib/widgets/album/all_collection_page.dart

@@ -1,4 +1,4 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/settings.dart';
 import 'package:aves/widgets/album/search_delegate.dart';
 import 'package:aves/widgets/album/thumbnail_collection.dart';
@@ -31,7 +31,7 @@ class _AllCollectionAppBar extends SliverAppBar {
   static List<Widget> _buildActions() {
     return [
       Builder(
-        builder: (context) => Consumer<ImageCollection>(
+        builder: (context) => Consumer<CollectionLens>(
           builder: (context, collection, child) => IconButton(
             icon: Icon(OMIcons.search),
             onPressed: () => showSearch(
@@ -42,7 +42,7 @@ class _AllCollectionAppBar extends SliverAppBar {
         ),
       ),
       Builder(
-        builder: (context) => Consumer<ImageCollection>(
+        builder: (context) => Consumer<CollectionLens>(
           builder: (context, collection, child) => PopupMenuButton<AlbumAction>(
             itemBuilder: (context) => [
               PopupMenuItem(
@@ -85,7 +85,7 @@ class _AllCollectionAppBar extends SliverAppBar {
     ];
   }
 
-  static void _onActionSelected(BuildContext context, ImageCollection collection, AlbumAction action) {
+  static void _onActionSelected(BuildContext context, CollectionLens collection, AlbumAction action) {
     switch (action) {
       case AlbumAction.debug:
         _goToDebug(context, collection);
@@ -117,7 +117,7 @@ class _AllCollectionAppBar extends SliverAppBar {
     }
   }
 
-  static Future _goToDebug(BuildContext context, ImageCollection collection) {
+  static Future _goToDebug(BuildContext context, CollectionLens collection) {
     return Navigator.push(
       context,
       MaterialPageRoute(

lib/widgets/album/collection_section.dart

@@ -1,4 +1,5 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
+import 'package:aves/model/collection_source.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/widgets/album/sections.dart';
 import 'package:aves/widgets/album/thumbnail.dart';
@@ -10,7 +11,7 @@ import 'package:flutter_sticky_header/flutter_sticky_header.dart';
 import 'package:provider/provider.dart';
 
 class SectionSliver extends StatelessWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final dynamic sectionKey;
   final int columnCount;
 
@@ -91,7 +92,7 @@ class ThumbnailMetadata {
 }
 
 class SectionHeader extends StatelessWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final Map<dynamic, List<ImageEntry>> sections;
   final dynamic sectionKey;
 
@@ -143,7 +144,7 @@ class SectionHeader extends StatelessWidget {
         child: albumIcon,
       );
     }
-    var title = collection.getUniqueAlbumName(sectionKey as String, sections.keys.cast<String>());
+    final title = CollectionSource.getUniqueAlbumName(sectionKey as String, sections.keys.cast<String>());
     return TitleSectionHeader(
       key: ValueKey(title),
       leading: albumIcon,

lib/widgets/album/filtered_collection_page.dart

@@ -1,24 +1,24 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_filters.dart';
-import 'package:aves/model/image_entry.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/widgets/album/thumbnail_collection.dart';
 import 'package:aves/widgets/common/providers/media_query_data_provider.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
 class FilteredCollectionPage extends StatelessWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
-  final bool Function(ImageEntry) filter;
+  final CollectionFilter filter;
   final String title;
 
-  FilteredCollectionPage({Key key, ImageCollection collection, this.filter, this.title})
+  FilteredCollectionPage({Key key, CollectionLens collection, this.filter, this.title})
-      : this.collection = collection.filter(filter),
+      : this.collection = CollectionLens.from(collection, filter),
         super(key: key);
 
   @override
   Widget build(BuildContext context) {
     return MediaQueryDataProvider(
       child: Scaffold(
-        body: ChangeNotifierProvider<ImageCollection>.value(
+        body: ChangeNotifierProvider<CollectionLens>.value(
           value: collection,
           child: ThumbnailCollection(
             appBar: SliverAppBar(

lib/widgets/album/search_delegate.dart

@@ -1,4 +1,5 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_filters.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/widgets/album/thumbnail_collection.dart';
 import 'package:aves/widgets/common/providers/media_query_data_provider.dart';
@@ -7,7 +8,7 @@ import 'package:outline_material_icons/outline_material_icons.dart';
 import 'package:provider/provider.dart';
 
 class ImageSearchDelegate extends SearchDelegate<ImageEntry> {
-  final ImageCollection collection;
+  final CollectionLens collection;
 
   ImageSearchDelegate(this.collection);
 
@@ -54,19 +55,17 @@ class ImageSearchDelegate extends SearchDelegate<ImageEntry> {
       showSuggestions(context);
       return const SizedBox.shrink();
     }
-    final lowerQuery = query.toLowerCase();
-    final matches = collection.sortedEntries.where((entry) => entry.search(lowerQuery)).toList();
-    if (matches.isEmpty) {
-      return _EmptyContent();
-    }
     return MediaQueryDataProvider(
-      child: ChangeNotifierProvider<ImageCollection>.value(
+      child: ChangeNotifierProvider<CollectionLens>.value(
-        value: ImageCollection(
+        value: CollectionLens(
-          entries: matches,
+          source: collection.source,
+          filters: [MetadataFilter(query.toLowerCase())],
           groupFactor: collection.groupFactor,
           sortFactor: collection.sortFactor,
         ),
-        child: ThumbnailCollection(),
+        child: ThumbnailCollection(
+          emptyBuilder: (context) => _EmptyContent(),
+        ),
       ),
     );
   }
@@ -76,7 +75,8 @@ class _EmptyContent extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     const color = Color(0xFF607D8B);
-    return Center(
+    return Align(
+      alignment: const FractionalOffset(.5, .4),
       child: Column(
         mainAxisSize: MainAxisSize.min,
         children: const [

lib/widgets/album/thumbnail.dart

@@ -10,7 +10,7 @@ class Thumbnail extends StatelessWidget {
   final double extent;
 
   static final Color borderColor = Colors.grey.shade700;
-  static const double  borderWidth = .5;
+  static const double borderWidth = .5;
 
   const Thumbnail({
     Key key,

lib/widgets/album/thumbnail_collection.dart

@@ -1,4 +1,4 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/widgets/album/collection_scaling.dart';
 import 'package:aves/widgets/album/collection_section.dart';
 import 'package:draggable_scrollbar/draggable_scrollbar.dart';
@@ -7,6 +7,8 @@ import 'package:provider/provider.dart';
 
 class ThumbnailCollection extends StatelessWidget {
   final Widget appBar;
+  final WidgetBuilder emptyBuilder;
+
   final ScrollController _scrollController = ScrollController();
   final ValueNotifier<int> _columnCountNotifier = ValueNotifier(4);
   final GlobalKey _scrollableKey = GlobalKey();
@@ -14,11 +16,12 @@ class ThumbnailCollection extends StatelessWidget {
   ThumbnailCollection({
     Key key,
     this.appBar,
+    this.emptyBuilder,
   }) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
-    final collection = Provider.of<ImageCollection>(context);
+    final collection = Provider.of<CollectionLens>(context);
     final sections = collection.sections;
     final sectionKeys = sections.keys.toList();
 
@@ -56,6 +59,12 @@ class ThumbnailCollection extends StatelessWidget {
                   controller: _scrollController,
                   slivers: [
                     if (appBar != null) appBar,
+                    if (collection.isEmpty && emptyBuilder != null)
+                      SliverFillViewport(
+                        delegate: SliverChildListDelegate(
+                          [emptyBuilder(context)],
+                        ),
+                      ),
                     ...sectionKeys.map((sectionKey) => SectionSliver(
                           collection: collection,
                           sectionKey: sectionKey,

lib/widgets/common/providers/media_store_collection_provider.dart

@@ -1,4 +1,5 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
+import 'package:aves/model/collection_source.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/model/image_file_service.dart';
 import 'package:aves/model/metadata_db.dart';
@@ -18,7 +19,7 @@ class MediaStoreCollectionProvider extends StatefulWidget {
 }
 
 class _MediaStoreCollectionProviderState extends State<MediaStoreCollectionProvider> {
-  Future<ImageCollection> collectionFuture;
+  Future<CollectionLens> collectionFuture;
 
   static const EventChannel eventChannel = EventChannel('deckers.thibault/aves/mediastore');
 
@@ -28,11 +29,14 @@ class _MediaStoreCollectionProviderState extends State<MediaStoreCollectionProvi
     collectionFuture = _create();
   }
 
-  Future<ImageCollection> _create() async {
+  Future<CollectionLens> _create() async {
     final stopwatch = Stopwatch()..start();
-    final mediaStoreCollection = ImageCollection(entries: []);
+    final mediaStoreSource = CollectionSource();
-    mediaStoreCollection.groupFactor = settings.collectionGroupFactor;
+    final mediaStoreBaseLens = CollectionLens(
-    mediaStoreCollection.sortFactor = settings.collectionSortFactor;
+      source: mediaStoreSource,
+      groupFactor: settings.collectionGroupFactor,
+      sortFactor: settings.collectionSortFactor,
+    );
 
     await metadataDb.init(); // <20ms
     final currentTimeZone = await FlutterNativeTimezone.getLocalTimezone(); // <20ms
@@ -44,17 +48,18 @@ class _MediaStoreCollectionProviderState extends State<MediaStoreCollectionProvi
       settings.catalogTimeZone = currentTimeZone;
     }
 
+    final allEntries = List<ImageEntry>();
     eventChannel.receiveBroadcastStream().cast<Map>().listen(
-          (entryMap) => mediaStoreCollection.add(ImageEntry.fromMap(entryMap)),
+          (entryMap) => allEntries.add(ImageEntry.fromMap(entryMap)),
           onDone: () async {
             debugPrint('$runtimeType stream complete in ${stopwatch.elapsed.inMilliseconds}ms');
-            mediaStoreCollection.updateSections(); // <50ms
+            mediaStoreSource.addAll(allEntries);
             // TODO reduce setup time until here
-            mediaStoreCollection.updateAlbums(); // <50ms
+            mediaStoreSource.updateAlbums(); // <50ms
-            await mediaStoreCollection.loadCatalogMetadata(); // 650ms
+            await mediaStoreSource.loadCatalogMetadata(); // 650ms
-            await mediaStoreCollection.catalogEntries(); // <50ms
+            await mediaStoreSource.catalogEntries(); // <50ms
-            await mediaStoreCollection.loadAddresses(); // 350ms
+            await mediaStoreSource.loadAddresses(); // 350ms
-            await mediaStoreCollection.locateEntries(); // <50ms
+            await mediaStoreSource.locateEntries(); // <50ms
             debugPrint('$runtimeType setup end, elapsed=${stopwatch.elapsed}');
           },
           onError: (error) => debugPrint('$runtimeType mediastore stream error=$error'),
@@ -63,16 +68,16 @@ class _MediaStoreCollectionProviderState extends State<MediaStoreCollectionProvi
     // TODO split image fetch AND/OR cache fetch across sessions
     await ImageFileService.getImageEntries(); // 460ms
 
-    return mediaStoreCollection;
+    return mediaStoreBaseLens;
   }
 
   @override
   Widget build(BuildContext context) {
     return FutureBuilder(
       future: collectionFuture,
-      builder: (futureContext, AsyncSnapshot<ImageCollection> snapshot) {
+      builder: (futureContext, AsyncSnapshot<CollectionLens> snapshot) {
-        final collection = (snapshot.connectionState == ConnectionState.done && !snapshot.hasError) ? snapshot.data : ImageCollection(entries: []);
+        final collection = (snapshot.connectionState == ConnectionState.done && !snapshot.hasError) ? snapshot.data : CollectionLens.empty();
-        return ChangeNotifierProvider<ImageCollection>.value(
+        return ChangeNotifierProvider<CollectionLens>.value(
           value: collection,
           child: widget.child,
         );

lib/widgets/fullscreen/fullscreen_action_delegate.dart

@@ -1,6 +1,6 @@
 import 'dart:io';
 
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/utils/android_app_service.dart';
 import 'package:flushbar/flushbar.dart';
@@ -12,7 +12,7 @@ import 'package:printing/printing.dart';
 enum FullscreenAction { delete, edit, info, open, openMap, print, rename, rotateCCW, rotateCW, setAs, share }
 
 class FullscreenActionDelegate {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final VoidCallback showInfo;
 
   FullscreenActionDelegate({
@@ -109,7 +109,7 @@ class FullscreenActionDelegate {
       },
     );
     if (confirmed == null || !confirmed) return;
-    if (!await collection.delete(entry)) {
+    if (!await collection.source.delete(entry)) {
       _showFeedback(context, 'Failed');
     } else if (collection.sortedEntries.isEmpty) {
       Navigator.pop(context);

lib/widgets/fullscreen/fullscreen_page.dart

@@ -1,7 +1,7 @@
 import 'dart:io';
 import 'dart:math';
 
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/widgets/common/providers/media_query_data_provider.dart';
 import 'package:aves/widgets/fullscreen/fullscreen_action_delegate.dart';
@@ -19,7 +19,7 @@ import 'package:tuple/tuple.dart';
 import 'package:video_player/video_player.dart';
 
 class FullscreenPage extends AnimatedWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final String initialUri;
 
   const FullscreenPage({
@@ -44,7 +44,7 @@ class FullscreenPage extends AnimatedWidget {
 }
 
 class FullscreenBody extends StatefulWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final String initialUri;
 
   const FullscreenBody({
@@ -69,7 +69,7 @@ class FullscreenBodyState extends State<FullscreenBody> with SingleTickerProvide
   FullscreenActionDelegate _actionDelegate;
   final List<Tuple2<String, VideoPlayerController>> _videoControllers = [];
 
-  ImageCollection get collection => widget.collection;
+  CollectionLens get collection => widget.collection;
 
   List<ImageEntry> get entries => widget.collection.sortedEntries;
 
@@ -273,7 +273,7 @@ class FullscreenBodyState extends State<FullscreenBody> with SingleTickerProvide
 }
 
 class FullscreenVerticalPageView extends StatefulWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final ImageEntry entry;
   final List<Tuple2<String, VideoPlayerController>> videoControllers;
   final PageController horizontalPager, verticalPager;

lib/widgets/fullscreen/image_page.dart

@@ -1,6 +1,6 @@
 import 'dart:io';
 
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/widgets/fullscreen/video.dart';
 import 'package:flutter/material.dart';
@@ -9,7 +9,7 @@ import 'package:tuple/tuple.dart';
 import 'package:video_player/video_player.dart';
 
 class ImagePage extends StatefulWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final PageController pageController;
   final VoidCallback onTap;
   final ValueChanged<int> onPageChanged;

lib/widgets/fullscreen/info/info_page.dart

@@ -1,4 +1,4 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/widgets/common/coma_divider.dart';
 import 'package:aves/widgets/common/providers/media_query_data_provider.dart';
@@ -13,7 +13,7 @@ import 'package:provider/provider.dart';
 import 'package:tuple/tuple.dart';
 
 class InfoPage extends StatefulWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final ImageEntry entry;
   final ValueNotifier<bool> visibleNotifier;
 

lib/widgets/fullscreen/info/xmp_section.dart

@@ -1,4 +1,5 @@
-import 'package:aves/model/image_collection.dart';
+import 'package:aves/model/collection_filters.dart';
+import 'package:aves/model/collection_lens.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/utils/color_utils.dart';
 import 'package:aves/widgets/album/filtered_collection_page.dart';
@@ -6,7 +7,7 @@ import 'package:aves/widgets/fullscreen/info/info_page.dart';
 import 'package:flutter/material.dart';
 
 class XmpTagSectionSliver extends AnimatedWidget {
-  final ImageCollection collection;
+  final CollectionLens collection;
   final ImageEntry entry;
 
   static const double buttonBorderWidth = 2;
@@ -56,7 +57,7 @@ class XmpTagSectionSliver extends AnimatedWidget {
       MaterialPageRoute(
         builder: (context) => FilteredCollectionPage(
           collection: collection,
-          filter: (entry) => entry.xmpSubjects.contains(tag),
+          filter: TagFilter(tag),
           title: tag,
         ),
       ),

pubspec.lock

@@ -80,6 +80,13 @@ packages:
       url: "git://github.com/deckerst/flutter-draggable-scrollbar.git"
     source: git
     version: "0.0.4"
+  event_bus:
+    dependency: "direct main"
+    description:
+      name: event_bus
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.1"
   flushbar:
     dependency: "direct main"
     description:

pubspec.yaml

@@ -21,6 +21,7 @@ dependencies:
   draggable_scrollbar:
     git:
       url: git://github.com/deckerst/flutter-draggable-scrollbar.git
+  event_bus:
   flushbar:
   flutter_native_timezone:
   flutter_staggered_grid_view: