perf: don't create thumbnails when auto-saving

lib/components/canvas/save_indicator.dart

@@ -28,21 +28,26 @@ class SaveIndicator extends StatelessWidget {
             icon: switch (savingState.value) {
               SavingState.waitingToSave => const Icon(Icons.save),
               SavingState.saving => const CircularProgressIndicator.adaptive(),
-              SavingState.saved => const Icon(Icons.arrow_back),
+              SavingState.savedWithoutThumbnail => const Icon(Icons.arrow_back),
+              SavingState.savedWithThumbnail => const Icon(Icons.arrow_back),
             },
           ),
         );
       },
     );
   }
 
+  /// When the save/exit button is pressed
   void _onPressed(BuildContext context) {
     switch (savingState.value) {
       case SavingState.waitingToSave:
         triggerSave();
       case SavingState.saving:
         break;
-      case SavingState.saved:
+      case SavingState.savedWithoutThumbnail:
+        triggerSave(); // triggering save will be created thumbnail and then is finished editing
+        _back(context);
+      case SavingState.savedWithThumbnail:
         _back(context);
     }
   }
@@ -62,5 +67,11 @@ class SaveIndicator extends StatelessWidget {
 enum SavingState {
   waitingToSave,
   saving,
-  saved,
+
+  /// Saved, but the thumbnail still needs updating.
+  /// (Thumbnails aren't created when auto-saving to avoid lag.)
+  savedWithoutThumbnail,
+
+  /// Saved, and the thumbnail is up-to-date.
+  savedWithThumbnail,
 }

lib/components/home/preview_card.dart

@@ -53,8 +53,11 @@ class _PreviewCardState extends State<PreviewCard> {
   }
 
   StreamSubscription? fileWriteSubscription;
+
+  /// Listen to changes of thumbnail file
   void fileWriteListener(FileOperation event) {
-    if (event.filePath != widget.filePath) return;
+    if (event.filePath != '${widget.filePath}${Editor.extension}.p') return;
+
     if (event.type == FileOperationType.delete) {
       thumbnail.image = null;
     } else if (event.type == FileOperationType.write) {

lib/components/navbar/responsive_navbar.dart

@@ -63,7 +63,8 @@ class _ResponsiveNavbarState extends State<ResponsiveNavbar> {
       final savingState = Whiteboard.savingState;
       switch (savingState) {
         case null:
-        case SavingState.saved:
+        case SavingState.savedWithoutThumbnail:
+        case SavingState.savedWithThumbnail:
           break;
         case SavingState.waitingToSave:
           Whiteboard.triggerSave();

lib/data/file_manager/file_manager.dart

@@ -28,6 +28,8 @@ class FileManager {
   /// Realistically, this value never changes.
   static late String documentsDirectory;
 
+  /// A stream of [FileOperation]s. Note that file paths
+  /// include the file extension.
   static final StreamController<FileOperation> fileWriteStream =
       StreamController.broadcast(
     onListen: () => _fileWriteStreamIsListening = true,
@@ -73,14 +75,6 @@ class FileManager {
   @visibleForTesting
   static void broadcastFileWrite(FileOperationType type, String path) async {
     if (!_fileWriteStreamIsListening) return;
-
-    // remove extension
-    if (path.endsWith(Editor.extension)) {
-      path = path.substring(0, path.length - Editor.extension.length);
-    } else if (path.endsWith(Editor.extensionOldJson)) {
-      path = path.substring(0, path.length - Editor.extensionOldJson.length);
-    }
-
     fileWriteStream.add(FileOperation(type, path));
   }
 

lib/pages/editor/editor.dart

@@ -170,8 +170,9 @@ class EditorState extends State<Editor> {
     Prefs.lastTool.value = tool.toolId;
   }
 
-  ValueNotifier<SavingState> savingState = ValueNotifier(SavingState.saved);
-  Timer? _delayedSaveTimer;
+  final savingState = ValueNotifier(SavingState.savedWithThumbnail);
+  @visibleForTesting
+  Timer? delayedSaveTimer;
 
   // used to prevent accidentally drawing when pinch zooming
   int lastSeenPointerCount = 0;
@@ -258,7 +259,8 @@ class EditorState extends State<Editor> {
       clearAllPages();
 
       // save cleared whiteboard
-      await saveToFile();
+      // without thumbanil as whiteboard thumbnail is never used
+      await saveToFile(createThumbnail: false);
       Whiteboard.needsToAutoClearWhiteboard = false;
     } else {
       setState(() {});
@@ -320,12 +322,12 @@ class EditorState extends State<Editor> {
       late final topOfLastPage = -CanvasGestureDetector.getTopOfPage(
         pageIndex: coreInfo.pages.length - 1,
         pages: coreInfo.pages,
-        screenWidth: MediaQuery.sizeOf(context).width,
+        screenWidth: _mediaQuery.size.width,
       );
       final bottomOfLastPage = -CanvasGestureDetector.getTopOfPage(
         pageIndex: coreInfo.pages.length,
         pages: coreInfo.pages,
-        screenWidth: MediaQuery.sizeOf(context).width,
+        screenWidth: _mediaQuery.size.width,
       );
 
       if (scrollY < bottomOfLastPage) {
@@ -802,28 +804,34 @@ class EditorState extends State<Editor> {
 
   void autosaveAfterDelay() {
     savingState.value = SavingState.waitingToSave;
-    _delayedSaveTimer?.cancel();
+    delayedSaveTimer?.cancel();
     if (Prefs.autosaveDelay.value < 0) return;
-    _delayedSaveTimer =
+    delayedSaveTimer =
         Timer(Duration(milliseconds: Prefs.autosaveDelay.value), () {
-      saveToFile();
+      saveToFile(createThumbnail: false);
     });
   }
 
-  Future<void> saveToFile() async {
+  Future<void> saveToFile({required bool createThumbnail}) async {
+    // createThumbnail=false is used when called from autosave - to avoid lagging during thumbnail creation
     if (coreInfo.readOnly) return;
 
     switch (savingState.value) {
-      case SavingState.saved:
+      case SavingState.savedWithThumbnail:
         // avoid saving if nothing has changed
         return;
+      case SavingState.savedWithoutThumbnail:
+        // note is saved, but thumbnail need to be created
+        createThumbnailPreview();
+        savingState.value = SavingState.savedWithThumbnail;
+        return;
       case SavingState.saving:
         // avoid saving if already saving
         log.warning('saveToFile() called while already saving');
         return;
       case SavingState.waitingToSave:
         // continue
-        _delayedSaveTimer?.cancel();
+        delayedSaveTimer?.cancel();
         savingState.value = SavingState.saving;
     }
 
@@ -852,14 +860,26 @@ class EditorState extends State<Editor> {
           numAssets: assets.length,
         ),
       ]);
-      savingState.value = SavingState.saved;
+      if (createThumbnail) {
+        savingState.value = SavingState.savedWithThumbnail;
+      } else {
+        savingState.value = SavingState.savedWithoutThumbnail;
+      }
     } catch (e) {
       log.severe('Failed to save file: $e', e);
       savingState.value = SavingState.waitingToSave;
       if (kDebugMode) rethrow;
       return;
     }
 
+    if (createThumbnail) await createThumbnailPreview();
+  }
+
+  /// create thumbnail of note
+  Future<void> createThumbnailPreview() async {
+    if (coreInfo.readOnly) return;
+    final filePath = coreInfo.filePath + Editor.extension;
+
     if (!mounted) return;
     final screenshotter = ScreenshotController();
     final page = coreInfo.pages.first;
@@ -868,31 +888,35 @@ class EditorState extends State<Editor> {
     );
     final thumbnailSize = Size(720, 720 * previewHeight / page.size.width);
     final thumbnail = await screenshotter.captureFromWidget(
-      Theme(
-        data: ThemeData(
-          brightness: Brightness.light,
-          colorScheme: const ColorScheme.light(
-            primary: EditorExporter.primaryColor,
-            secondary: EditorExporter.secondaryColor,
-          ),
+      MediaQuery(
+        data: MediaQueryData(
+          size: thumbnailSize,
+          devicePixelRatio: 1,
         ),
-        child: Localizations.override(
-          context: context,
-          child: SizedBox(
-            width: thumbnailSize.width,
-            height: thumbnailSize.height,
-            child: FittedBox(
-              child: pagePreviewBuilder(
-                context,
-                pageIndex: 0,
-                previewHeight: previewHeight,
+        child: MaterialApp(
+          theme: ThemeData(
+            brightness: Brightness.light,
+            colorScheme: const ColorScheme.light(
+              primary: EditorExporter.primaryColor,
+              secondary: EditorExporter.secondaryColor,
+            ),
+          ),
+          home: SizedBox(
+              width: thumbnailSize.width,
+              height: thumbnailSize.height,
+              child: FittedBox(
+                child: Builder(
+                  builder: (context) => pagePreviewBuilder(
+                    context,
+                    pageIndex: 0,
+                    previewHeight: previewHeight,
+                  ),
+                ),
               ),
             ),
           ),
-        ),
       ),
       pixelRatio: 1,
-      context: context,
       targetSize: thumbnailSize,
     );
     await FileManager.writeFile(
@@ -1280,6 +1304,14 @@ class EditorState extends State<Editor> {
     ));
   }
 
+  late MediaQueryData _mediaQuery = const MediaQueryData();
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    _mediaQuery = MediaQuery.of(context);
+  }
+
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
@@ -1553,17 +1585,18 @@ class EditorState extends State<Editor> {
       builder: (context, savingState, child) {
         // don't allow user to go back until saving is done
         return PopScope(
-          canPop: savingState == SavingState.saved,
+          canPop: savingState == SavingState.savedWithThumbnail,
           onPopInvoked: (didPop) {
             switch (savingState) {
               case SavingState.waitingToSave:
                 assert(!didPop);
-                saveToFile(); // trigger save now
+                saveToFile(createThumbnail: true); // trigger save now
                 snackBarNeedsToSaveBeforeExiting();
               case SavingState.saving:
                 assert(!didPop);
                 snackBarNeedsToSaveBeforeExiting();
-              case SavingState.saved:
+              case SavingState.savedWithoutThumbnail:
+              case SavingState.savedWithThumbnail:
                 break;
             }
           },
@@ -1592,7 +1625,7 @@ class EditorState extends State<Editor> {
                       ),
                 leading: SaveIndicator(
                   savingState: savingState,
-                  triggerSave: saveToFile,
+                  triggerSave: () => saveToFile(createThumbnail: true),
                 ),
                 actions: [
                   IconButton(
@@ -1607,7 +1640,7 @@ class EditorState extends State<Editor> {
                       CanvasGestureDetector.scrollToPage(
                         pageIndex: currentPageIndex + 1,
                         pages: coreInfo.pages,
-                        screenWidth: MediaQuery.sizeOf(context).width,
+                        screenWidth: _mediaQuery.size.width,
                         transformationController: _transformationController,
                       );
                     }),
@@ -1920,11 +1953,9 @@ class EditorState extends State<Editor> {
   int get currentPageIndex {
     if (!mounted) return _lastCurrentPageIndex;
 
-    final screenWidth = MediaQuery.sizeOf(context).width;
-
     return _lastCurrentPageIndex = getPageIndexFromScrollPosition(
       scrollY: -scrollY,
-      screenWidth: screenWidth,
+      screenWidth: _mediaQuery.size.width,
       pages: coreInfo.pages,
     );
   }
@@ -1951,21 +1982,21 @@ class EditorState extends State<Editor> {
   }
 
   @override
-  void dispose() {
+  void dispose() async {
+    delayedSaveTimer?.cancel();
+    _lastSeenPointerCountTimer?.cancel();
+
     (() async {
       if (_renameTimer?.isActive ?? false) {
         _renameTimer!.cancel();
         await _renameFileNow();
         filenameTextEditingController.dispose();
       }
-      await saveToFile();
+      await saveToFile(createThumbnail: true);
     })();
 
     DynamicMaterialApp.removeFullscreenListener(_setState);
 
-    _delayedSaveTimer?.cancel();
-    _lastSeenPointerCountTimer?.cancel();
-
     _removeKeybindings();
 
     coreInfo.dispose();

lib/pages/home/whiteboard.dart

@@ -21,7 +21,7 @@ class Whiteboard extends StatelessWidget {
     final editorState = _whiteboardKey.currentState;
     if (editorState == null) return;
     assert(editorState.savingState.value == SavingState.waitingToSave);
-    editorState.saveToFile();
+    editorState.saveToFile(createThumbnail: false);
     editorState.snackBarNeedsToSaveBeforeExiting();
   }
 

test/editor_undo_redo_test.dart

@@ -61,6 +61,11 @@ void main() {
         reason: 'Editor is still read-only');
     printOnFailure('Editor core info is loaded');
 
+    addTearDown(() async {
+      editorState.delayedSaveTimer?.cancel();
+      await FileManager.deleteFile(filePath + Editor.extension);
+    });
+
     IconButton getUndoBtn() => tester.widget<IconButton>(find.ancestor(
           of: find.byIcon(Icons.undo),
           matching: find.byType(IconButton),
@@ -108,14 +113,6 @@ void main() {
         reason: 'Undo button should be enabled after undo and draw');
     expect(getRedoBtn().onPressed, isNull,
         reason: 'Redo button should be disabled after undo and draw');
-
-    // save file now to supersede the save timer (which would run after the test is finished)
-    printOnFailure('Saving file: $filePath${Editor.extension}');
-    await tester.runAsync(() async {
-      await editorState.saveToFile();
-      await Future.delayed(const Duration(milliseconds: 100));
-      await FileManager.deleteFile(filePath + Editor.extension);
-    });
   });
 }