example: save and read Utf-16 LE files

fix api to return empty list on cancel

bump file_selector_platform_interface

fix reentrance issue in SaveTextFile widget

getPathForShellItem throws on error

replace import

rename variable

Author: adpinola

packages/file_selector/file_selector_windows/example/lib/open_text_page.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:typed_data';
+
 import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
 import 'package:flutter/material.dart';
 
@@ -23,7 +25,14 @@ class OpenTextPage extends StatelessWidget {
       return;
     }
     final String fileName = file.name;
-    final String fileContent = await file.readAsString();
+
+    // This behavior defaults works when reading files encoded using UTF-16 LE.
+    // If you have files encoded with UTF-8 you can simply use file.readAsString()
+    // For other encodings, consider using Encoding.getByName() method, to get your enconder
+    // before calling file.readAsString()
+    final Uint8List bytes = await file.readAsBytes();
+    final Uint16List utf16CodeUnits = bytes.buffer.asUint16List();
+    final String fileContent = String.fromCharCodes(utf16CodeUnits);
 
     await showDialog<void>(
       context: context,

packages/file_selector/file_selector_windows/example/lib/save_text_page.dart

@@ -25,10 +25,12 @@ class SaveTextPage extends StatelessWidget {
       return;
     }
     final String text = _contentController.text;
-    final Uint8List fileData = Uint8List.fromList(text.codeUnits);
+
+    // This behavior saves an Utf-16 LE encoded file.
+    final Uint16List fileData = Uint16List.fromList(text.codeUnits);
     const String fileMimeType = 'text/plain';
-    final XFile textFile =
-        XFile.fromData(fileData, mimeType: fileMimeType, name: fileName);
+    final XFile textFile = XFile.fromData(fileData.buffer.asUint8List(),
+        mimeType: fileMimeType, name: fileName);
     await textFile.saveTo(path);
   }
 

packages/file_selector/file_selector_windows/example/pubspec.yaml

@@ -8,7 +8,7 @@ environment:
   flutter: ">=3.0.0"
 
 dependencies:
-  file_selector_platform_interface: ^2.2.0
+  file_selector_platform_interface: ^2.3.0
   file_selector_windows:
     # When depending on this package from a real application you should use:
     #   file_selector_windows: ^x.y.z

packages/file_selector/file_selector_windows/lib/file_selector_windows.dart

@@ -15,13 +15,13 @@ import 'src/file_selector_dart/selection_options.dart';
 /// An implementation of [FileSelectorPlatform] for Windows.
 class FileSelectorWindows extends FileSelectorPlatform {
   /// Creates a new instance of [FileSelectorApi].
-  FileSelectorWindows(int foregroundWindowHandle)
+  FileSelectorWindows()
       : _hostApi = FileSelectorApi(
             DialogWrapperFactory(
               FileDialogControllerFactory(),
               IFileDialogFactory(),
             ),
-            foregroundWindowHandle);
+            GetActiveWindow());
 
   /// Creates a fake implementation of [FileSelectorApi] for testing purposes.
   @visibleForTesting
@@ -31,7 +31,7 @@ class FileSelectorWindows extends FileSelectorPlatform {
 
   /// Registers the Windows implementation.
   static void registerWith() {
-    FileSelectorPlatform.instance = FileSelectorWindows(GetForegroundWindow());
+    FileSelectorPlatform.instance = FileSelectorWindows();
   }
 
   @override

packages/file_selector/file_selector_windows/lib/src/file_selector_api.dart

@@ -13,11 +13,11 @@ import 'file_selector_dart/selection_options.dart';
 class FileSelectorApi {
   /// Creates a new instance of [FileSelectorApi].
   /// Allows Dependency Injection of a [DialogWrapperFactory] to handle dialog creation.
-  FileSelectorApi(this._dialogWrapperFactory, this._foregroundWindow);
+  FileSelectorApi(this._dialogWrapperFactory, this._activeWindow);
 
   final DialogWrapperFactory _dialogWrapperFactory;
 
-  final int _foregroundWindow;
+  final int _activeWindow;
 
   /// Displays a dialog window to open one or more files.
   List<String?> showOpenDialog(
@@ -26,7 +26,7 @@ class FileSelectorApi {
     String? confirmButtonText,
   ) =>
       _showDialog(
-        _foregroundWindow,
+        _activeWindow,
         DialogMode.open,
         options,
         initialDirectory,
@@ -42,7 +42,7 @@ class FileSelectorApi {
     String? confirmButtonText,
   ) =>
       _showDialog(
-        _foregroundWindow,
+        _activeWindow,
         DialogMode.save,
         options,
         initialDirectory,
@@ -90,9 +90,6 @@ class FileSelectorApi {
 
     final List<String?>? files = dialogWrapper.show(parentWindow);
     dialogWrapper.release();
-    if (files != null) {
-      return files;
-    }
-    throw WindowsException(E_FAIL);
+    return files ?? <String>[];
   }
 }

packages/file_selector/file_selector_windows/lib/src/file_selector_dart/dialog_wrapper.dart

@@ -7,7 +7,7 @@ import 'dart:ffi';
 
 import 'package:ffi/ffi.dart';
 import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
-import 'package:flutter/cupertino.dart';
+import 'package:flutter/foundation.dart';
 import 'package:win32/win32.dart';
 
 import 'dialog_mode.dart';
@@ -181,34 +181,40 @@ class DialogWrapper {
       Pointer<Pointer<COMObject>> shellItemArrayPtr,
       Pointer<Uint32> shellItemCountPtr,
       Pointer<Pointer<COMObject>> shellItemPtr) {
-    final List<String> files = <String>[];
-    if (_isOpenDialog) {
-      _lastResult = _dialogController.getResults(shellItemArrayPtr);
-      if (!SUCCEEDED(_lastResult)) {
-        return null;
-      }
+    try {
+      final List<String> files = <String>[];
+      int lastOperationResult;
+      if (_isOpenDialog) {
+        lastOperationResult = _dialogController.getResults(shellItemArrayPtr);
+        if (!SUCCEEDED(lastOperationResult)) {
+          throw WindowsException(lastOperationResult);
+        }
 
-      final IShellItemArray shellItemResources =
-          IShellItemArray(shellItemArrayPtr.cast());
-      _lastResult = shellItemResources.getCount(shellItemCountPtr);
-      if (!SUCCEEDED(_lastResult)) {
-        return null;
-      }
-      for (int index = 0; index < shellItemCountPtr.value; index += 1) {
-        shellItemResources.getItemAt(index, shellItemPtr);
+        final IShellItemArray shellItemResources =
+            IShellItemArray(shellItemArrayPtr.cast());
+        lastOperationResult = shellItemResources.getCount(shellItemCountPtr);
+        if (!SUCCEEDED(lastOperationResult)) {
+          throw WindowsException(lastOperationResult);
+        }
+        for (int index = 0; index < shellItemCountPtr.value; index += 1) {
+          shellItemResources.getItemAt(index, shellItemPtr);
+          final IShellItem shellItem = IShellItem(shellItemPtr.cast());
+          files.add(_shellWin32Api.getPathForShellItem(shellItem));
+          _shellWin32Api.releaseShellItem(shellItem);
+        }
+      } else {
+        lastOperationResult = _dialogController.getResult(shellItemPtr);
+        if (!SUCCEEDED(lastOperationResult)) {
+          throw WindowsException(lastOperationResult);
+        }
         final IShellItem shellItem = IShellItem(shellItemPtr.cast());
         files.add(_shellWin32Api.getPathForShellItem(shellItem));
         _shellWin32Api.releaseShellItem(shellItem);
       }
-    } else {
-      _lastResult = _dialogController.getResult(shellItemPtr);
-      if (!SUCCEEDED(_lastResult)) {
-        return null;
-      }
-      final IShellItem shellItem = IShellItem(shellItemPtr.cast());
-      files.add(_shellWin32Api.getPathForShellItem(shellItem));
-      _shellWin32Api.releaseShellItem(shellItem);
+      return files;
+    } on WindowsException catch (ex) {
+      _lastResult = ex.hr;
+      return null;
     }
-    return files;
   }
 }

packages/file_selector/file_selector_windows/lib/src/file_selector_dart/shell_win32_api.dart

@@ -32,7 +32,7 @@ class ShellWin32Api {
       );
 
       if (!SUCCEEDED(operationResult)) {
-        return '';
+        throw WindowsException(operationResult);
       }
       return ptrPath.value.toDartString();
     });

packages/file_selector/file_selector_windows/test/file_selector_api_test.dart

@@ -68,14 +68,16 @@ void main() {
           .called(1);
     });
 
-    test('should throw an exception if file list is null', () {
+    test('should return an empty list if operation is cancelled', () {
       // Arrange
       when(mockDialogWrapper.show(parentWindow)).thenReturn(null);
 
-      // Act - Assert
-      expect(
-          () => fileSelectorApi.showSaveDialog(emptyOptions, null, null, null),
-          throwsA(const TypeMatcher<WindowsException>()));
+      // Act
+      final List<String?> result =
+          fileSelectorApi.showSaveDialog(emptyOptions, null, null, null);
+
+      // Assert
+      expect(result.isEmpty, true);
     });
   });
   group('showOpenDialog', () {
@@ -88,14 +90,16 @@ void main() {
           .called(1);
     });
 
-    test('should throw an exception if file list is null', () {
+    test('should return an empty list if operation is cancelled', () {
       // Arrange
       when(mockDialogWrapper.show(parentWindow)).thenReturn(null);
 
-      // Act - Assert
-      expect(
-          () => fileSelectorApi.showOpenDialog(emptyOptions, null, null),
-          throwsA(const TypeMatcher<WindowsException>()));
+      // Act
+      final List<String?> result =
+          fileSelectorApi.showOpenDialog(emptyOptions, null, null);
+
+      // Assert
+      expect(result.isEmpty, true);
     });
   });
   group('Common behavior', () {

packages/file_selector/file_selector_windows/test/file_selector_dart/dialog_wrapper_test.dart

@@ -272,7 +272,24 @@ void main() {
     verify(mockFileDialogController.getResult(any)).called(1);
   });
 
-  test('[DialogMode == Save] show should the selected directory for', () {
+  test(
+      '[DialogMode == Save] show should return null if cannot getPathForShellItem',
+      () {
+    final DialogWrapper dialogWrapperModeSave =
+        DialogWrapper.withFakeDependencies(
+            mockFileDialogController, DialogMode.save, mockShellWin32Api);
+    const int parentWindow = 0;
+    when(mockFileDialogController.show(parentWindow)).thenReturn(S_OK);
+    when(mockFileDialogController.getResult(any)).thenReturn(S_OK);
+    when(mockShellWin32Api.getPathForShellItem(any))
+        .thenThrow(WindowsException(E_FAIL));
+
+    final List<String?>? result = dialogWrapperModeSave.show(parentWindow);
+
+    expect(result, null);
+  });
+
+  test('[DialogMode == Save] show should return the file path', () {
     const String filePath = 'path/to/file.txt';
     final DialogWrapper dialogWrapperModeSave =
         DialogWrapper.withFakeDependencies(