feat: resume selection on window focus (#6455)

frontend/appflowy_flutter/integration_test/desktop/document/document_app_lifecycle_test.dart

@@ -0,0 +1,32 @@
+import 'dart:ui';
+
+import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:integration_test/integration_test.dart';
+
+import '../../shared/util.dart';
+
+void main() {
+  final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  group('Editor AppLifeCycle tests', () {
+    testWidgets(
+      'Selection is added back after pausing AppFlowy',
+      (tester) async {
+        await tester.initializeAppFlowy();
+        await tester.tapAnonymousSignInButton();
+
+        final selection = Selection.single(path: [4], startOffset: 0);
+        await tester.editor.updateSelection(selection);
+
+        binding.handleAppLifecycleStateChanged(AppLifecycleState.inactive);
+        expect(tester.editor.getCurrentEditorState().selection, null);
+
+        binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
+        await tester.pumpAndSettle();
+
+        expect(tester.editor.getCurrentEditorState().selection, selection);
+      },
+    );
+  });
+}

frontend/appflowy_flutter/integration_test/desktop_runner_3.dart

@@ -4,6 +4,8 @@ import 'desktop/board/board_test_runner.dart' as board_test_runner;
 import 'desktop/database/database_row_cover_test.dart'
     as database_row_cover_test;
 import 'desktop/document/document_title_test.dart' as document_title_test;
+import 'desktop/document/document_app_lifecycle_test.dart'
+    as document_app_lifecycle_test;
 import 'desktop/document/document_sub_page_test.dart' as document_sub_page_test;
 import 'desktop/grid/grid_filter_and_sort_test.dart'
     as grid_filter_and_sort_test_runner;
@@ -11,8 +13,8 @@ import 'desktop/grid/grid_reopen_test.dart' as grid_reopen_test_runner;
 import 'desktop/grid/grid_reorder_row_test.dart'
     as grid_reorder_row_test_runner;
 import 'desktop/grid/grid_edit_row_test.dart' as grid_edit_row_test_runner;
-import 'desktop/settings/settings_runner.dart' as settings_test_runner;
 import 'desktop/grid/grid_row_test.dart' as grid_create_row_test_runner;
+import 'desktop/settings/settings_runner.dart' as settings_test_runner;
 import 'desktop/sidebar/sidebar_test_runner.dart' as sidebar_test_runner;
 import 'desktop/uncategorized/emoji_shortcut_test.dart' as emoji_shortcut_test;
 import 'desktop/uncategorized/empty_test.dart' as first_test;
@@ -51,4 +53,5 @@ Future<void> runIntegration3OnDesktop() async {
   zoom_in_out_test.main();
   document_title_test.main();
   document_sub_page_test.main();
+  document_app_lifecycle_test.main();
 }

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_page.dart

@@ -58,7 +58,8 @@ class AppFlowyEditorPage extends StatefulWidget {
   State<AppFlowyEditorPage> createState() => _AppFlowyEditorPageState();
 }
 
-class _AppFlowyEditorPageState extends State<AppFlowyEditorPage> {
+class _AppFlowyEditorPageState extends State<AppFlowyEditorPage>
+    with WidgetsBindingObserver {
   late final ScrollController effectiveScrollController;
 
   late final InlineActionsService inlineActionsService = InlineActionsService(
@@ -126,6 +127,7 @@ class _AppFlowyEditorPageState extends State<AppFlowyEditorPage> {
   @override
   void initState() {
     super.initState();
+    WidgetsBinding.instance.addObserver(this);
 
     if (widget.useViewInfoBloc) {
       viewInfoBloc.add(
@@ -163,6 +165,8 @@ class _AppFlowyEditorPageState extends State<AppFlowyEditorPage> {
     // customize the dynamic theme color
     _customizeBlockComponentBackgroundColorDecorator();
 
+    widget.editorState.selectionNotifier.addListener(onSelectionChanged);
+
     WidgetsBinding.instance.addPostFrameCallback((_) {
       if (!mounted) {
         return;
@@ -181,6 +185,24 @@ class _AppFlowyEditorPageState extends State<AppFlowyEditorPage> {
     });
   }
 
+  Selection? previousSelection;
+
+  void onSelectionChanged() {
+    if (widget.editorState.isDisposed || widget.editorState.selection == null) {
+      return;
+    }
+
+    previousSelection = widget.editorState.selection;
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    super.didChangeAppLifecycleState(state);
+    if (state == AppLifecycleState.resumed && !widget.editorState.isDisposed) {
+      widget.editorState.selection = previousSelection;
+    }
+  }
+
   @override
   void didChangeDependencies() {
     final currFocusManager = AFFocusManager.maybeOf(context);
@@ -202,6 +224,7 @@ class _AppFlowyEditorPageState extends State<AppFlowyEditorPage> {
 
   @override
   void dispose() {
+    widget.editorState.selectionNotifier.removeListener(onSelectionChanged);
     widget.editorState.service.keyboardService?.unregisterInterceptor(
       editorKeyboardInterceptor,
     );