feat: support export functionality on web by download

integration_test/export_flow_test.dart

@@ -30,6 +30,30 @@ class RecordingExporter extends ExportService {
   }
 }
 
+// Lightweight fake exporter to avoid invoking heavy rasterization during tests
+class LightweightExporter extends ExportService {
+  @override
+  Future<Uint8List?> exportSignedPdfFromBytes({
+    required Uint8List srcBytes,
+    required Size uiPageSize,
+    required Uint8List? signatureImageBytes,
+    Map<int, List<SignaturePlacement>>? placementsByPage,
+    Map<String, Uint8List>? libraryBytes,
+    double targetDpi = 144.0,
+  }) async {
+    // Return minimal non-empty bytes; content isn't used further in tests
+    return Uint8List.fromList([1, 2, 3]);
+  }
+
+  @override
+  Future<bool> saveBytesToFile({
+    required Uint8List bytes,
+    required String outputPath,
+  }) async {
+    return true;
+  }
+}
+
 void main() {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
 
@@ -225,13 +249,13 @@ void main() {
     await tester.pumpAndSettle();
     final ctx = tester.element(find.byType(PdfSignatureHomePage));
     final container = ProviderScope.containerOf(ctx);
-    expect(container.read(pdfViewModelProvider), 1);
+    expect(container.read(pdfViewModelProvider).currentPage, 1);
     container.read(pdfViewModelProvider.notifier).jumpToPage(2);
     await tester.pumpAndSettle();
-    expect(container.read(pdfViewModelProvider), 2);
+    expect(container.read(pdfViewModelProvider).currentPage, 2);
     container.read(pdfViewModelProvider.notifier).jumpToPage(3);
     await tester.pumpAndSettle();
-    expect(container.read(pdfViewModelProvider), 3);
+    expect(container.read(pdfViewModelProvider).currentPage, 3);
   });
 
   testWidgets('PDF View: zoom in/out', (tester) async {
@@ -319,7 +343,7 @@ void main() {
     await tester.pumpAndSettle();
     final ctx = tester.element(find.byType(PdfSignatureHomePage));
     final container = ProviderScope.containerOf(ctx);
-    expect(container.read(pdfViewModelProvider), 1);
+    expect(container.read(pdfViewModelProvider).currentPage, 1);
 
     final pagesSidebar = find.byType(PagesSidebar);
     expect(pagesSidebar, findsOneWidget);
@@ -332,7 +356,7 @@ void main() {
     expect(page3Thumb, findsOneWidget);
     await tester.tap(page3Thumb);
     await tester.pumpAndSettle();
-    expect(container.read(pdfViewModelProvider), 3);
+    expect(container.read(pdfViewModelProvider).currentPage, 3);
   });
 
   testWidgets('PDF View: thumbnails scroll and select', (tester) async {
@@ -371,15 +395,70 @@ void main() {
     await tester.pumpAndSettle();
     final ctx = tester.element(find.byType(PdfSignatureHomePage));
     final container = ProviderScope.containerOf(ctx);
-    expect(container.read(pdfViewModelProvider), 1);
+    expect(container.read(pdfViewModelProvider).currentPage, 1);
     final sidebar = find.byType(PagesSidebar);
     expect(sidebar, findsOneWidget);
     await tester.drag(sidebar, const Offset(0, -200));
     await tester.pumpAndSettle();
     expect(find.text('1'), findsOneWidget);
-    expect(container.read(pdfViewModelProvider), 1);
+    expect(container.read(pdfViewModelProvider).currentPage, 1);
     await tester.tap(find.text('2'));
     await tester.pumpAndSettle();
-    expect(container.read(pdfViewModelProvider), 2);
+    expect(container.read(pdfViewModelProvider).currentPage, 2);
+  });
+
+  testWidgets('PDF View: tap viewer after export does not crash', (
+    tester,
+  ) async {
+    final pdfBytes =
+        await File('integration_test/data/sample-local-pdf.pdf').readAsBytes();
+    SharedPreferences.setMockInitialValues({});
+    final prefs = await SharedPreferences.getInstance();
+
+    await tester.pumpWidget(
+      ProviderScope(
+        overrides: [
+          preferencesRepositoryProvider.overrideWith(
+            (ref) => PreferencesStateNotifier(prefs),
+          ),
+          documentRepositoryProvider.overrideWith(
+            (ref) =>
+                DocumentStateNotifier()
+                  ..openPicked(pageCount: 3, bytes: pdfBytes),
+          ),
+          pdfViewModelProvider.overrideWith(
+            (ref) => PdfViewModel(ref, useMockViewer: false),
+          ),
+          exportServiceProvider.overrideWith((ref) => LightweightExporter()),
+          savePathPickerProvider.overrideWith(
+            (_) => () async => 'C:/tmp/output-after-export.pdf',
+          ),
+        ],
+        child: MaterialApp(
+          localizationsDelegates: AppLocalizations.localizationsDelegates,
+          supportedLocales: AppLocalizations.supportedLocales,
+          locale: const Locale('en'),
+          home: PdfSignatureHomePage(
+            onPickPdf: () async {},
+            onClosePdf: () {},
+            currentFile: fs.XFile('test.pdf'),
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    // Trigger export
+    await tester.tap(find.byKey(const Key('btn_save_pdf')));
+    await tester.pumpAndSettle();
+
+    // Tap on the page area; should not crash
+    final pageArea = find.byKey(const ValueKey('pdf_page_area'));
+    expect(pageArea, findsOneWidget);
+    await tester.tap(pageArea);
+    await tester.pumpAndSettle();
+
+    // Still present and responsive
+    expect(pageArea, findsOneWidget);
   });
 }

lib/ui/features/pdf/view_model/pdf_view_model.dart

@@ -34,7 +34,7 @@ class PdfViewModel extends ChangeNotifier {
   PdfViewModel(this.ref, {bool? useMockViewer})
     : _useMockViewer =
           useMockViewer ??
-          bool.fromEnvironment('FLUTTER_TEST', defaultValue: false);
+          const bool.fromEnvironment('FLUTTER_TEST', defaultValue: false);
 
   bool get useMockViewer => _useMockViewer;
 

lib/ui/features/pdf/widgets/pdf_screen.dart

@@ -13,6 +13,7 @@ import 'pdf_page_area.dart';
 import 'pages_sidebar.dart';
 import 'signatures_sidebar.dart';
 import 'ui_services.dart';
+import 'package:pdf_signature/utils/download.dart';
 import '../view_model/pdf_view_model.dart';
 
 class PdfSignatureHomePage extends ConsumerStatefulWidget {
@@ -168,6 +169,21 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
         if (out != null) {
           ok = await exporter.saveBytesToFile(bytes: out, outputPath: fullPath);
         }
+      } else {
+        // Web: export and trigger browser download
+        final src = pdf.pickedPdfBytes ?? Uint8List(0);
+        final out = await exporter.exportSignedPdfFromBytes(
+          srcBytes: src,
+          uiPageSize: _pageSize,
+          signatureImageBytes: null,
+          placementsByPage: pdf.placementsByPage,
+          targetDpi: targetDpi,
+        );
+        if (out != null) {
+          // Use a sensible default filename (cannot prompt path on web)
+          ok = await downloadBytes(out, filename: 'signed.pdf');
+          savedPath = 'signed.pdf';
+        }
       }
       if (!kIsWeb) {
         if (ok) {
@@ -185,6 +201,19 @@ class _PdfSignatureHomePageState extends ConsumerState<PdfSignatureHomePage> {
             ),
           );
         }
+      } else {
+        // Web: show a toast-like confirmation
+        messenger.showSnackBar(
+          SnackBar(
+            content: Text(
+              ok
+                  ? AppLocalizations.of(
+                    context,
+                  ).savedWithPath(savedPath ?? 'signed.pdf')
+                  : AppLocalizations.of(context).failedToSavePdf,
+            ),
+          ),
+        );
       }
     } finally {
       ref.read(exportingProvider.notifier).state = false;

lib/utils/download.dart

@@ -0,0 +1,11 @@
+import 'dart:typed_data';
+
+import 'download_stub.dart' if (dart.library.html) 'download_web.dart' as impl;
+
+/// Initiates a platform-appropriate download/save operation.
+///
+/// On Web: triggers a browser download with the provided filename.
+/// On non-Web: returns false (no-op). Use your existing IO save flow instead.
+Future<bool> downloadBytes(Uint8List bytes, {required String filename}) {
+  return impl.downloadBytes(bytes, filename: filename);
+}

lib/utils/download_stub.dart

@@ -0,0 +1,6 @@
+import 'dart:typed_data';
+
+Future<bool> downloadBytes(Uint8List bytes, {required String filename}) async {
+  // Not supported on non-web. Return false so caller can fallback to file save.
+  return false;
+}

lib/utils/download_web.dart

@@ -0,0 +1,22 @@
+// ignore: avoid_web_libraries_in_flutter
+import 'dart:html' as html;
+import 'dart:typed_data';
+
+Future<bool> downloadBytes(Uint8List bytes, {required String filename}) async {
+  try {
+    final blob = html.Blob([bytes], 'application/pdf');
+    final url = html.Url.createObjectUrlFromBlob(blob);
+    final anchor =
+        html.document.createElement('a') as html.AnchorElement
+          ..href = url
+          ..download = filename
+          ..style.display = 'none';
+    html.document.body?.children.add(anchor);
+    anchor.click();
+    anchor.remove();
+    html.Url.revokeObjectUrl(url);
+    return true;
+  } catch (_) {
+    return false;
+  }
+}