Rewrite slideshow viewer

app/lib/widget/slideshow_dialog.dart

@@ -12,7 +12,7 @@ part 'slideshow_dialog.g.dart';
 
 @toString
 class SlideshowConfig {
-  SlideshowConfig({
+  const SlideshowConfig({
     required this.duration,
     required this.isShuffle,
     required this.isRepeat,

app/lib/widget/slideshow_viewer.dart

@@ -1,9 +1,13 @@
 import 'dart:async';
 
+import 'package:copy_with/copy_with.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
+import 'package:nc_photos/bloc_util.dart';
+import 'package:nc_photos/controller/account_controller.dart';
 import 'package:nc_photos/entity/file_descriptor.dart';
 import 'package:nc_photos/entity/file_util.dart' as file_util;
 import 'package:nc_photos/k.dart' as k;
@@ -17,24 +21,28 @@ import 'package:nc_photos/widget/viewer_mixin.dart';
 import 'package:nc_photos/widget/wakelock_util.dart';
 import 'package:np_codegen/np_codegen.dart';
 import 'package:np_ui/np_ui.dart';
+import 'package:to_string/to_string.dart';
 
 part 'slideshow_viewer.g.dart';
+part 'slideshow_viewer/bloc.dart';
+part 'slideshow_viewer/state_event.dart';
+part 'slideshow_viewer/view.dart';
 
 class SlideshowViewerArguments {
-  SlideshowViewerArguments(
+  const SlideshowViewerArguments(
     this.account,
-    this.streamFiles,
+    this.files,
     this.startIndex,
     this.config,
   );
 
   final Account account;
-  final List<FileDescriptor> streamFiles;
+  final List<FileDescriptor> files;
   final int startIndex;
   final SlideshowConfig config;
 }
 
-class SlideshowViewer extends StatefulWidget {
+class SlideshowViewer extends StatelessWidget {
   static const routeName = "/slideshow-viewer";
 
   static Route buildRoute(SlideshowViewerArguments args) => MaterialPageRoute(
@@ -44,7 +52,7 @@ class SlideshowViewer extends StatefulWidget {
   const SlideshowViewer({
     super.key,
     required this.account,
-    required this.streamFiles,
+    required this.files,
     required this.startIndex,
     required this.config,
   });
@@ -53,44 +61,49 @@ class SlideshowViewer extends StatefulWidget {
       : this(
           key: key,
           account: args.account,
-          streamFiles: args.streamFiles,
+          files: args.files,
           startIndex: args.startIndex,
           config: args.config,
         );
 
   @override
-  createState() => _SlideshowViewerState();
+  Widget build(BuildContext context) {
+    return BlocProvider(
+      create: (context) => _Bloc(
+        account: context.read<AccountController>().account,
+        files: files,
+        startIndex: startIndex,
+        config: config,
+      )..add(const _Init()),
+      child: const _WrappedSlideshowViewer(),
+    );
+  }
 
   final Account account;
-  final List<FileDescriptor> streamFiles;
+  final List<FileDescriptor> files;
   final int startIndex;
   final SlideshowConfig config;
 }
 
-@npLog
-class _SlideshowViewerState extends State<SlideshowViewer>
-    with
-        DisposableManagerMixin<SlideshowViewer>,
-        ViewerControllersMixin<SlideshowViewer> {
+class _WrappedSlideshowViewer extends StatefulWidget {
+  const _WrappedSlideshowViewer();
+
   @override
-  initState() {
+  State<StatefulWidget> createState() => _WrappedSlideshowViewerState();
+}
+
+class _WrappedSlideshowViewerState extends State<_WrappedSlideshowViewer>
+    with
+        DisposableManagerMixin<_WrappedSlideshowViewer>,
+        ViewerControllersMixin<_WrappedSlideshowViewer> {
+  @override
+  void initState() {
     super.initState();
-    _shuffledIndex = () {
-      final index = [for (var i = 0; i < widget.streamFiles.length; ++i) i];
-      if (widget.config.isShuffle) {
-        return index..shuffle();
-      } else if (widget.config.isReverse) {
-        return index.reversed.toList();
-      } else {
-        return index;
-      }
-    }();
-    _initSlideshow();
     SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
   }
 
   @override
-  initDisposables() {
+  List<Disposable> initDisposables() {
     return [
       ...super.initDisposables(),
       WakelockControllerDisposable(),
@@ -98,210 +111,23 @@ class _SlideshowViewerState extends State<SlideshowViewer>
   }
 
   @override
-  build(BuildContext context) {
+  Widget build(BuildContext context) {
     return Theme(
       data: buildDarkTheme(context),
-      child: Scaffold(
-        body: Builder(
-          builder: _buildContent,
-        ),
+      child: const Scaffold(
+        body: _Body(),
       ),
     );
   }
-
-  Widget _buildContent(BuildContext context) {
-    final int initialPage;
-    if (widget.config.isShuffle) {
-      // the original order is meaningless after shuffled
-      initialPage = 0;
-    } else if (widget.config.isReverse) {
-      initialPage = widget.streamFiles.length - 1 - widget.startIndex;
-    } else {
-      initialPage = widget.startIndex;
-    }
-    return GestureDetector(
-      onTap: () {
-        setState(() {
-          _setShowActionBar(!_isShowAppBar);
-        });
-      },
-      child: Stack(
-        children: [
-          Container(color: Colors.black),
-          HorizontalPageViewer(
-            pageCount:
-                widget.config.isRepeat ? null : widget.streamFiles.length,
-            pageBuilder: _buildPage,
-            initialPage: initialPage,
-            controller: _viewerController,
-            viewportFraction: _viewportFraction,
-            canSwitchPage: false,
-          ),
-          _buildAppBar(context),
-        ],
-      ),
-    );
-  }
-
-  Widget _buildAppBar(BuildContext context) {
-    return Wrap(
-      children: [
-        AnimatedVisibility(
-          opacity: _isShowAppBar ? 1.0 : 0.0,
-          duration: k.animationDurationNormal,
-          child: Stack(
-            children: [
-              Container(
-                // + status bar height
-                height: kToolbarHeight + MediaQuery.of(context).padding.top,
-                decoration: const BoxDecoration(
-                  gradient: LinearGradient(
-                    begin: Alignment(0, -1),
-                    end: Alignment(0, 1),
-                    colors: [
-                      Color.fromARGB(192, 0, 0, 0),
-                      Color.fromARGB(0, 0, 0, 0),
-                    ],
-                  ),
-                ),
-              ),
-              AppBar(
-                backgroundColor: Colors.transparent,
-                elevation: 0,
-                leading: IconButton(
-                  icon: const Icon(Icons.close),
-                  tooltip: MaterialLocalizations.of(context).closeButtonTooltip,
-                  onPressed: () {
-                    Navigator.of(context).pop();
-                  },
-                ),
-              ),
-            ],
-          ),
-        ),
-      ],
-    );
-  }
-
-  Widget _buildPage(BuildContext context, int index) {
-    final itemIndex = _transformIndex(index);
-    _log.info("[_buildPage] Page: $index, item: $itemIndex");
-    return FractionallySizedBox(
-      widthFactor: 1 / _viewportFraction,
-      child: _buildItemView(context, itemIndex),
-    );
-  }
-
-  Widget _buildItemView(BuildContext context, int index) {
-    final file = widget.streamFiles[index];
-    if (file_util.isSupportedImageFormat(file)) {
-      return _buildImageView(context, index);
-    } else if (file_util.isSupportedVideoFormat(file)) {
-      return _buildVideoView(context, index);
-    } else {
-      _log.shout("[_buildItemView] Unknown file format: ${file.fdMime}");
-      return Container();
-    }
-  }
-
-  Widget _buildImageView(BuildContext context, int index) {
-    return RemoteImageViewer(
-      account: widget.account,
-      file: widget.streamFiles[index],
-      canZoom: false,
-      onLoaded: () => _onImageLoaded(index),
-    );
-  }
-
-  Widget _buildVideoView(BuildContext context, int index) {
-    return VideoViewer(
-      account: widget.account,
-      file: widget.streamFiles[index],
-      onLoadFailure: () {
-        // error, next
-        Future.delayed(const Duration(seconds: 2), _onSlideshowTick);
-      },
-      onPause: () {
-        // video ended
-        Future.delayed(const Duration(seconds: 2), _onSlideshowTick);
-      },
-      isControlVisible: false,
-      canLoop: false,
-    );
-  }
-
-  void _onImageLoaded(int index) {
-    // currently pageview doesn't pre-load pages, we do it manually
-    // don't pre-load if user already navigated away
-    if (_viewerController.currentPage == index) {
-      _log.info("[_onImageLoaded] Pre-loading nearby images");
-      if (index > 0) {
-        final prevFile = widget.streamFiles[index - 1];
-        if (file_util.isSupportedImageFormat(prevFile)) {
-          RemoteImageViewer.preloadImage(widget.account, prevFile);
-        }
-      }
-      if (index + 1 < widget.streamFiles.length) {
-        final nextFile = widget.streamFiles[index + 1];
-        if (file_util.isSupportedImageFormat(nextFile)) {
-          RemoteImageViewer.preloadImage(widget.account, nextFile);
-        }
-      }
-    }
-  }
-
-  void _initSlideshow() {
-    _setupSlideTransition(widget.startIndex);
-  }
-
-  Future<void> _onSlideshowTick() async {
-    if (!mounted) {
-      return;
-    }
-    _log.info("[_onSlideshowTick] Next item");
-    final page = _viewerController.currentPage;
-    await _viewerController.nextPage(
-        duration: k.animationDurationLong, curve: Curves.easeInOut);
-    final newPage = _viewerController.currentPage;
-    if (page == newPage) {
-      // end reached
-      _log.info("[_onSlideshowTick] Reached the end");
-      return;
-    }
-    _setupSlideTransition(newPage);
-
-    unawaited(SystemChrome.restoreSystemUIOverlays());
-  }
-
-  void _setupSlideTransition(int index) {
-    final itemIndex = _transformIndex(index);
-    final item = widget.streamFiles[itemIndex];
-    if (file_util.isSupportedVideoFormat(item)) {
-      // for videos, we need to wait until it's ended
-    } else {
-      Future.delayed(widget.config.duration, _onSlideshowTick);
-    }
-  }
-
-  void _setShowActionBar(bool flag) {
-    _isShowAppBar = flag;
-    if (flag) {
-      SystemChrome.setEnabledSystemUIMode(SystemUiMode.manual,
-          overlays: SystemUiOverlay.values);
-    } else {
-      SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
-    }
-  }
-
-  /// Return the page index to the corresponding item index
-  int _transformIndex(int pageIndex) =>
-      _shuffledIndex[pageIndex % widget.streamFiles.length];
-
-  var _isShowAppBar = false;
-
-  final _viewerController = HorizontalPageViewerController();
-  // late final _SlideshowController _slideshowController;
-  late final List<int> _shuffledIndex;
-
-  static const _viewportFraction = 1.05;
+}
+
+// typedef _BlocBuilder = BlocBuilder<_Bloc, _State>;
+// typedef _BlocListener = BlocListener<_Bloc, _State>;
+typedef _BlocListenerT<T> = BlocListenerT<_Bloc, _State, T>;
+typedef _BlocSelector<T> = BlocSelector<_Bloc, _State, T>;
+
+extension on BuildContext {
+  _Bloc get bloc => read<_Bloc>();
+  // _State get state => bloc.state;
+  void addEvent(_Event event) => bloc.add(event);
 }

app/lib/widget/slideshow_viewer.g.dart

@@ -2,13 +2,125 @@
 
 part of 'slideshow_viewer.dart';
 
+// **************************************************************************
+// CopyWithLintRuleGenerator
+// **************************************************************************
+
+// ignore_for_file: library_private_types_in_public_api, duplicate_ignore
+
+// **************************************************************************
+// CopyWithGenerator
+// **************************************************************************
+
+abstract class $_StateCopyWithWorker {
+  _State call(
+      {bool? hasInit,
+      int? page,
+      int? nextPage,
+      FileDescriptor? currentFile,
+      bool? isShowUi});
+}
+
+class _$_StateCopyWithWorkerImpl implements $_StateCopyWithWorker {
+  _$_StateCopyWithWorkerImpl(this.that);
+
+  @override
+  _State call(
+      {dynamic hasInit,
+      dynamic page,
+      dynamic nextPage,
+      dynamic currentFile,
+      dynamic isShowUi}) {
+    return _State(
+        hasInit: hasInit as bool? ?? that.hasInit,
+        page: page as int? ?? that.page,
+        nextPage: nextPage as int? ?? that.nextPage,
+        currentFile: currentFile as FileDescriptor? ?? that.currentFile,
+        isShowUi: isShowUi as bool? ?? that.isShowUi);
+  }
+
+  final _State that;
+}
+
+extension $_StateCopyWith on _State {
+  $_StateCopyWithWorker get copyWith => _$copyWith;
+  $_StateCopyWithWorker get _$copyWith => _$_StateCopyWithWorkerImpl(this);
+}
+
 // **************************************************************************
 // NpLogGenerator
 // **************************************************************************
 
-extension _$_SlideshowViewerStateNpLog on _SlideshowViewerState {
+extension _$_BlocNpLog on _Bloc {
   // ignore: unused_element
   Logger get _log => log;
 
-  static final log = Logger("widget.slideshow_viewer._SlideshowViewerState");
+  static final log = Logger("widget.slideshow_viewer._Bloc");
+}
+
+extension _$_BodyNpLog on _Body {
+  // ignore: unused_element
+  Logger get _log => log;
+
+  static final log = Logger("widget.slideshow_viewer._Body");
+}
+
+extension _$_PageViewNpLog on _PageView {
+  // ignore: unused_element
+  Logger get _log => log;
+
+  static final log = Logger("widget.slideshow_viewer._PageView");
+}
+
+// **************************************************************************
+// ToStringGenerator
+// **************************************************************************
+
+extension _$_StateToString on _State {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_State {hasInit: $hasInit, page: $page, nextPage: $nextPage, currentFile: ${currentFile.fdPath}, isShowUi: $isShowUi}";
+  }
+}
+
+extension _$_InitToString on _Init {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_Init {}";
+  }
+}
+
+extension _$_ToggleShowUiToString on _ToggleShowUi {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_ToggleShowUi {}";
+  }
+}
+
+extension _$_PreloadSidePagesToString on _PreloadSidePages {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_PreloadSidePages {center: $center}";
+  }
+}
+
+extension _$_VideoCompletedToString on _VideoCompleted {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_VideoCompleted {page: $page}";
+  }
+}
+
+extension _$_SetCurrentPageToString on _SetCurrentPage {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_SetCurrentPage {value: $value}";
+  }
+}
+
+extension _$_NextPageToString on _NextPage {
+  String _$toString() {
+    // ignore: unnecessary_string_interpolations
+    return "_NextPage {value: $value}";
+  }
 }

app/lib/widget/slideshow_viewer/bloc.dart

@@ -0,0 +1,187 @@
+part of '../slideshow_viewer.dart';
+
+@npLog
+class _Bloc extends Bloc<_Event, _State> with BlocLogger {
+  _Bloc({
+    required this.account,
+    required this.files,
+    required this.startIndex,
+    required this.config,
+  }) : super(_State.init(
+          initialFile: files[startIndex],
+        )) {
+    on<_Init>(_onInit);
+    on<_ToggleShowUi>(_onToggleShowUi);
+    on<_PreloadSidePages>(_onPreloadSidePages);
+    on<_VideoCompleted>(_onVideoCompleted);
+    on<_SetCurrentPage>(_onSetCurrentPage);
+    on<_NextPage>(_onNextPage);
+  }
+
+  @override
+  Future<void> close() {
+    _showUiTimer?.cancel();
+    for (final s in _subscriptions) {
+      s.cancel();
+    }
+    return super.close();
+  }
+
+  @override
+  String get tag => _log.fullName;
+
+  /// Convert the page index to the corresponding item index
+  int convertPageToFileIndex(int pageIndex) =>
+      _shuffledIndex[pageIndex % files.length];
+
+  void _onInit(_Init ev, Emitter<_State> emit) {
+    _log.info(ev);
+    final parsedConfig = _parseConfig(
+      files: files,
+      startIndex: startIndex,
+      config: config,
+    );
+    _shuffledIndex = parsedConfig.shuffled;
+    initialPage = parsedConfig.initial;
+    pageCount = parsedConfig.count;
+    emit(state.copyWith(
+      hasInit: true,
+      page: initialPage,
+      currentFile: _getFileByPageIndex(initialPage),
+    ));
+    _prepareNextPage();
+  }
+
+  void _onToggleShowUi(_ToggleShowUi ev, Emitter<_State> emit) {
+    _log.info(ev);
+    emit(state.copyWith(isShowUi: !state.isShowUi));
+    if (state.isShowUi) {
+      SystemChrome.setEnabledSystemUIMode(
+        SystemUiMode.manual,
+        overlays: SystemUiOverlay.values,
+      );
+      _showUiTimer?.cancel();
+      _showUiTimer = Timer(
+        const Duration(seconds: 3),
+        () {
+          if (state.isShowUi) {
+            add(const _ToggleShowUi());
+          }
+        },
+      );
+    } else {
+      SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
+    }
+  }
+
+  void _onPreloadSidePages(_PreloadSidePages ev, Emitter<_State> emit) {
+    _log.info(ev);
+    // currently pageview doesn't pre-load pages, we do it manually
+    // don't pre-load if user already navigated away
+    if (state.page != ev.center) {
+      return;
+    }
+    _log.info("[_onPreloadSidePages] Pre-loading nearby images");
+    if (ev.center > 0) {
+      final fileIndex = convertPageToFileIndex(ev.center - 1);
+      final prevFile = files[fileIndex];
+      if (file_util.isSupportedImageFormat(prevFile)) {
+        RemoteImageViewer.preloadImage(account, prevFile);
+      }
+    }
+    if (pageCount == null || ev.center + 1 < pageCount!) {
+      final fileIndex = convertPageToFileIndex(ev.center + 1);
+      final nextFile = files[fileIndex];
+      if (file_util.isSupportedImageFormat(nextFile)) {
+        RemoteImageViewer.preloadImage(account, nextFile);
+      }
+    }
+  }
+
+  void _onVideoCompleted(_VideoCompleted ev, Emitter<_State> emit) {
+    _log.info(ev);
+    _gotoNextPage();
+  }
+
+  void _onSetCurrentPage(_SetCurrentPage ev, Emitter<_State> emit) {
+    _log.info(ev);
+    emit(state.copyWith(
+      page: ev.value,
+      currentFile: _getFileByPageIndex(ev.value),
+    ));
+    _prepareNextPage();
+  }
+
+  void _onNextPage(_NextPage ev, Emitter<_State> emit) {
+    _log.info(ev);
+    emit(state.copyWith(nextPage: ev.value));
+  }
+
+  static ({List<int> shuffled, int initial, int? count}) _parseConfig({
+    required List<FileDescriptor> files,
+    required int startIndex,
+    required SlideshowConfig config,
+  }) {
+    final index = [for (var i = 0; i < files.length; ++i) i];
+    final count = config.isRepeat ? null : files.length;
+    if (config.isShuffle) {
+      return (
+        shuffled: index..shuffle(),
+        initial: 0,
+        count: count,
+      );
+    } else if (config.isReverse) {
+      return (
+        shuffled: index.reversed.toList(),
+        initial: files.length - 1 - startIndex,
+        count: count,
+      );
+    } else {
+      return (
+        shuffled: index,
+        initial: startIndex,
+        count: count,
+      );
+    }
+  }
+
+  Future<void> _prepareNextPage() async {
+    final file = state.currentFile;
+    if (file_util.isSupportedVideoFormat(file)) {
+      // for videos, we need to wait until it's ended
+      return;
+    }
+    // for photos, we wait for a fixed amount of time defined in config
+    await Future.delayed(config.duration);
+    _gotoNextPage();
+  }
+
+  void _gotoNextPage() {
+    if (isClosed) {
+      return;
+    }
+    final nextPage = state.page + 1;
+    if (pageCount != null && nextPage >= pageCount!) {
+      // end reached
+      _log.info("[_gotoNextSlide] Reached the end");
+      return;
+    }
+    _log.info("[_gotoNextSlide] Next page: $nextPage");
+    add(_NextPage(nextPage));
+  }
+
+  FileDescriptor _getFileByPageIndex(int pageIndex) =>
+      files[convertPageToFileIndex(pageIndex)];
+
+  final Account account;
+  final List<FileDescriptor> files;
+  final int startIndex;
+  final SlideshowConfig config;
+
+  late final List<int> _shuffledIndex;
+  late final int initialPage;
+  late final int? pageCount;
+
+  final _subscriptions = <StreamSubscription>[];
+  Timer? _showUiTimer;
+}

app/lib/widget/slideshow_viewer/state_event.dart

@@ -0,0 +1,91 @@
+part of '../slideshow_viewer.dart';
+
+@genCopyWith
+@toString
+class _State {
+  const _State({
+    required this.hasInit,
+    required this.page,
+    required this.nextPage,
+    required this.currentFile,
+    required this.isShowUi,
+  });
+
+  factory _State.init({
+    required FileDescriptor initialFile,
+  }) =>
+      _State(
+        hasInit: false,
+        page: 0,
+        nextPage: 0,
+        currentFile: initialFile,
+        isShowUi: false,
+      );
+
+  @override
+  String toString() => _$toString();
+
+  final bool hasInit;
+  final int page;
+  final int nextPage;
+  final FileDescriptor currentFile;
+  final bool isShowUi;
+}
+
+abstract class _Event {}
+
+@toString
+class _Init implements _Event {
+  const _Init();
+
+  @override
+  String toString() => _$toString();
+}
+
+@toString
+class _ToggleShowUi implements _Event {
+  const _ToggleShowUi();
+
+  @override
+  String toString() => _$toString();
+}
+
+@toString
+class _PreloadSidePages implements _Event {
+  const _PreloadSidePages(this.center);
+
+  @override
+  String toString() => _$toString();
+
+  final int center;
+}
+
+@toString
+class _VideoCompleted implements _Event {
+  const _VideoCompleted(this.page);
+
+  @override
+  String toString() => _$toString();
+
+  final int page;
+}
+
+@toString
+class _SetCurrentPage implements _Event {
+  const _SetCurrentPage(this.value);
+
+  @override
+  String toString() => _$toString();
+
+  final int value;
+}
+
+@toString
+class _NextPage implements _Event {
+  const _NextPage(this.value);
+
+  @override
+  String toString() => _$toString();
+
+  final int value;
+}

app/lib/widget/slideshow_viewer/view.dart

@@ -0,0 +1,207 @@
+part of '../slideshow_viewer.dart';
+
+class _AppBar extends StatelessWidget {
+  const _AppBar();
+
+  @override
+  Widget build(BuildContext context) {
+    return Stack(
+      children: [
+        Container(
+          // + status bar height
+          height: kToolbarHeight + MediaQuery.of(context).padding.top,
+          decoration: const BoxDecoration(
+            gradient: LinearGradient(
+              begin: Alignment.topCenter,
+              end: Alignment.bottomCenter,
+              colors: [
+                Color.fromARGB(192, 0, 0, 0),
+                Color.fromARGB(0, 0, 0, 0),
+              ],
+            ),
+          ),
+        ),
+        AppBar(
+          backgroundColor: Colors.transparent,
+          elevation: 0,
+          leading: IconButton(
+            icon: const Icon(Icons.close),
+            tooltip: MaterialLocalizations.of(context).closeButtonTooltip,
+            onPressed: () {
+              Navigator.of(context).pop();
+            },
+          ),
+        ),
+      ],
+    );
+  }
+}
+
+@npLog
+class _Body extends StatelessWidget {
+  const _Body();
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: () {
+        context.addEvent(const _ToggleShowUi());
+      },
+      child: Stack(
+        fit: StackFit.expand,
+        children: [
+          const ColoredBox(color: Colors.black),
+          _BlocSelector<bool>(
+            selector: (state) => state.hasInit,
+            builder: (context, hasInit) =>
+                hasInit ? const _PageViewer() : const SizedBox.shrink(),
+          ),
+          _BlocSelector<bool>(
+            selector: (state) => state.isShowUi,
+            builder: (context, isShowUi) => AnimatedVisibility(
+              opacity: isShowUi ? 1 : 0,
+              duration: k.animationDurationNormal,
+              child: const Align(
+                alignment: Alignment.topCenter,
+                child: _AppBar(),
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _PageViewer extends StatefulWidget {
+  const _PageViewer();
+
+  @override
+  State<StatefulWidget> createState() => _PageViewerState();
+}
+
+class _PageViewerState extends State<_PageViewer> {
+  @override
+  Widget build(BuildContext context) {
+    return MultiBlocListener(
+      listeners: [
+        _BlocListenerT(
+          selector: (state) => state.nextPage,
+          listener: (context, state) {
+            _controller.nextPage(
+              duration: k.animationDurationLong,
+              curve: Curves.easeInOut,
+            );
+          },
+        ),
+      ],
+      child: HorizontalPageViewer(
+        pageCount: context.bloc.pageCount,
+        pageBuilder: (context, index) {
+          return FractionallySizedBox(
+            widthFactor: 1 / _viewportFraction,
+            child: _PageView.ofPage(context, index),
+          );
+        },
+        initialPage: context.bloc.initialPage,
+        controller: _controller,
+        viewportFraction: _viewportFraction,
+        canSwitchPage: false,
+        onPageChanged: (from, to) {
+          context.addEvent(_SetCurrentPage(to));
+        },
+      ),
+    );
+  }
+
+  final _controller = HorizontalPageViewerController();
+}
+
+@npLog
+class _PageView extends StatelessWidget {
+  const _PageView._({
+    required this.page,
+    required this.itemIndex,
+  });
+
+  factory _PageView.ofPage(BuildContext context, int page) => _PageView._(
+        page: page,
+        itemIndex: context.bloc.convertPageToFileIndex(page),
+      );
+
+  @override
+  Widget build(BuildContext context) {
+    final file = context.bloc.files[itemIndex];
+    if (file_util.isSupportedImageFormat(file)) {
+      return _ImagePageView(
+        file: file,
+        onLoaded: () {
+          context.addEvent(_PreloadSidePages(page));
+        },
+      );
+    } else if (file_util.isSupportedVideoFormat(file)) {
+      return _VideoPageView(
+        file: file,
+        onCompleted: () {
+          context.addEvent(_VideoCompleted(page));
+        },
+      );
+    } else {
+      _log.shout("[build] Unknown file format: ${file.fdMime}");
+      return const SizedBox.shrink();
+    }
+  }
+
+  final int page;
+  final int itemIndex;
+}
+
+class _ImagePageView extends StatelessWidget {
+  const _ImagePageView({
+    required this.file,
+    this.onLoaded,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return RemoteImageViewer(
+      account: context.bloc.account,
+      file: file,
+      canZoom: false,
+      onLoaded: onLoaded,
+    );
+  }
+
+  final FileDescriptor file;
+  final VoidCallback? onLoaded;
+}
+
+class _VideoPageView extends StatelessWidget {
+  const _VideoPageView({
+    required this.file,
+    this.onCompleted,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return VideoViewer(
+      account: context.bloc.account,
+      file: file,
+      onLoadFailure: () {
+        // error, next
+        Future.delayed(const Duration(seconds: 2), onCompleted);
+      },
+      onPause: () {
+        // video ended
+        Future.delayed(const Duration(seconds: 2), onCompleted);
+      },
+      isControlVisible: false,
+      canLoop: false,
+    );
+  }
+
+  final FileDescriptor file;
+  final VoidCallback? onCompleted;
+}
+
+const _viewportFraction = 1.05;