Code Quality: Isolate remaining Windows-only code (P4 orphans)

src/Files.App/Files.App.csproj

@@ -245,6 +245,7 @@
         <Compile Remove="Helpers\Layout\LayoutPreferencesDatabase.Linux.cs" />
         <Compile Remove="Services\SizeProvider\CachedSizeProvider.Linux.cs" />
         <Compile Remove="Utils\Storage\Operations\FileSizeCalculator.Linux.cs" />
+        <Compile Remove="Utils\Storage\Helpers\SyncRootHelpers.Linux.cs" />
     </ItemGroup>
 
     <!--  XAML pages are matched by SDK default globs that run after this file, so Page Remove has no effect; use DefaultItemExcludes  -->

src/Files.App/Utils/Storage/Helpers/SyncRootHelpers.Linux.cs

@@ -0,0 +1,12 @@
+// Copyright (c) Files Community
+// Licensed under the MIT License.
+
+namespace Files.App.Utils.Storage
+{
+	internal static class SyncRootHelpers
+	{
+		// LINUX-TODO(cloud): Windows cloud sync roots have no Linux equivalent; report no quota.
+		public static Task<(bool Success, ulong Capacity, ulong Used)> GetSyncRootQuotaAsync(string path)
+			=> Task.FromResult((false, 0ul, 0ul));
+	}
+}

src/Files.App/ViewModels/UserControls/NavigationToolbarViewModel.Windows.cs

@@ -0,0 +1,63 @@
+// Copyright (c) Files Community
+// Licensed under the MIT License.
+
+using Files.Shared.Helpers;
+using System.IO;
+using Windows.Win32;
+using Windows.Win32.Storage.FileSystem;
+
+namespace Files.App.ViewModels.UserControls
+{
+	public sealed partial class NavigationToolbarViewModel
+	{
+		/// <summary>
+		/// Enumerates subfolders using Win32 API, including hidden folders based on user settings.
+		/// Returns null if the path cannot be enumerated with Win32.
+		/// </summary>
+		private unsafe List<(string Name, string Path, bool IsHidden)>? GetSubfolders(string parentPath)
+		{
+			WIN32_FIND_DATAW findData = default;
+			using FindCloseSafeHandle hFile = PInvoke.FindFirstFileEx(
+				$"{parentPath}{Path.DirectorySeparatorChar}*.*",
+				FINDEX_INFO_LEVELS.FindExInfoBasic,
+				&findData,
+				FINDEX_SEARCH_OPS.FindExSearchNameMatch,
+				FIND_FIRST_EX_FLAGS.FIND_FIRST_EX_LARGE_FETCH);
+
+			if (hFile.IsInvalid)
+				return null;
+
+			var showHidden = UserSettingsService.FoldersSettingsService.ShowHiddenItems;
+			var showSystem = UserSettingsService.FoldersSettingsService.ShowProtectedSystemFiles;
+			var showDot = UserSettingsService.FoldersSettingsService.ShowDotFiles;
+			var folders = new List<(string Name, string Path, bool IsHidden)>();
+
+			do
+			{
+				if (((FileAttributes)findData.dwFileAttributes & FileAttributes.Directory) == 0)
+					continue;
+
+				string fileName = findData.cFileName.ToString();
+				if (fileName is "." or "..")
+					continue;
+
+				bool isHidden = ((FileAttributes)findData.dwFileAttributes & FileAttributes.Hidden) != 0;
+				bool isSystem = ((FileAttributes)findData.dwFileAttributes & FileAttributes.System) != 0;
+
+				if (isHidden && (!showHidden || (isSystem && !showSystem)))
+					continue;
+
+				if (fileName.StartsWith('.') && !showDot)
+					continue;
+
+				folders.Add((fileName, Path.Combine(parentPath, fileName), isHidden));
+			}
+			while (PInvoke.FindNextFile(hFile, out findData));
+
+			var naturalComparer = NaturalStringComparer.GetForProcessor();
+			folders.Sort((a, b) => naturalComparer.Compare(a.Name, b.Name));
+
+			return folders;
+		}
+	}
+}

src/Files.App/ViewModels/UserControls/NavigationToolbarViewModel.cs

@@ -14,8 +14,6 @@
 using System.Windows.Input;
 using Windows.ApplicationModel.DataTransfer;
 using WinRT;
-using Windows.Win32;
-using Windows.Win32.Storage.FileSystem;
 
 namespace Files.App.ViewModels.UserControls
 {
@@ -712,7 +710,11 @@ public async Task SetPathBoxDropDownFlyoutAsync(MenuFlyout flyout, PathBoxItem p
 			var path = pathItem.Path
 				?? throw new InvalidOperationException("The path box item does not have a path.");
 
+#if WINDOWS
 			var childFolders = OperatingSystem.IsWindows() ? GetSubfolders(path) : await GetSubfoldersAsync(path);
+#else
+			var childFolders = await GetSubfoldersAsync(path);
+#endif
 
 			// Fall back to StorageFolder API for non-filesystem paths (e.g. FTP)
 			if (childFolders is null)
@@ -827,56 +829,6 @@ public async Task SetPathBoxDropDownFlyoutAsync(MenuFlyout flyout, PathBoxItem p
 			}
 		}
 
-		/// <summary>
-		/// Enumerates subfolders using Win32 API, including hidden folders based on user settings.
-		/// Returns null if the path cannot be enumerated with Win32.
-		/// </summary>
-		private unsafe List<(string Name, string Path, bool IsHidden)>? GetSubfolders(string parentPath)
-		{
-			WIN32_FIND_DATAW findData = default;
-			using FindCloseSafeHandle hFile = PInvoke.FindFirstFileEx(
-				$"{parentPath}{Path.DirectorySeparatorChar}*.*",
-				FINDEX_INFO_LEVELS.FindExInfoBasic,
-				&findData,
-				FINDEX_SEARCH_OPS.FindExSearchNameMatch,
-				FIND_FIRST_EX_FLAGS.FIND_FIRST_EX_LARGE_FETCH);
-
-			if (hFile.IsInvalid)
-				return null;
-
-			var showHidden = UserSettingsService.FoldersSettingsService.ShowHiddenItems;
-			var showSystem = UserSettingsService.FoldersSettingsService.ShowProtectedSystemFiles;
-			var showDot = UserSettingsService.FoldersSettingsService.ShowDotFiles;
-			var folders = new List<(string Name, string Path, bool IsHidden)>();
-
-			do
-			{
-				if (((FileAttributes)findData.dwFileAttributes & FileAttributes.Directory) == 0)
-					continue;
-
-				string fileName = findData.cFileName.ToString();
-				if (fileName is "." or "..")
-					continue;
-
-				bool isHidden = ((FileAttributes)findData.dwFileAttributes & FileAttributes.Hidden) != 0;
-				bool isSystem = ((FileAttributes)findData.dwFileAttributes & FileAttributes.System) != 0;
-
-				if (isHidden && (!showHidden || (isSystem && !showSystem)))
-					continue;
-
-				if (fileName.StartsWith('.') && !showDot)
-					continue;
-
-				folders.Add((fileName, Path.Combine(parentPath, fileName), isHidden));
-			}
-			while (PInvoke.FindNextFile(hFile, out findData));
-
-			var naturalComparer = NaturalStringComparer.GetForProcessor();
-			folders.Sort((a, b) => naturalComparer.Compare(a.Name, b.Name));
-
-			return folders;
-		}
-
 		private async Task LoadFlyoutItemIconAsync(MenuFlyoutItem flyoutItem, string path)
 		{
 			var imageSource = await NavigationHelpers.GetIconForPathAsync(path);