Fix the crash after adding the Windows 11 menu entry, and the donut on a drag without files

src/Filee.App/Services/RadialController.cs

@@ -1,8 +1,9 @@
 // Opens, fills and closes the live donut toolbar.
 //
 // Drag mode  (modifier + drag in Explorer):
-//   gesture detected → empty ring appears at the cursor (not activated) → DragEnter brings the file list →
-//   slices pop out → drop on a slice converts / drop in the hole or release elsewhere closes.
+//   gesture detected → an invisible window waits at the cursor (not activated) → DragEnter brings the file list →
+//   the donut pops out → drop on a slice converts / drop in the hole or release elsewhere closes. Without files
+//   (text, a rubber-band selection) nothing ever shows.
 // Click mode (keyboard shortcut, context menu, drop zone):
 //   files are known up front → donut appears activated → click a slice to convert, right-click to edit,
 //   Esc / click outside closes.
@@ -45,7 +46,11 @@ public sealed class RadialController(
 
     public bool IsVisible => _visible;
 
-    /// <summary>Drag gesture started at the given physical screen point.</summary>
+    /// <summary>
+    /// Drag gesture started at the given physical screen point. The window is placed under the cursor but stays
+    /// invisible until files are dragged into it (FilesEntered); a gesture without files (text, a rubber-band
+    /// selection, nothing at all) never shows anything and closes when the button is released.
+    /// </summary>
     public void ShowForDrag(int x, int y)
     {
         ReleaseProgressToToast();
@@ -54,7 +59,6 @@ public void ShowForDrag(int x, int y)
         viewModel.ResetForDrag();
         window.DonutControl.AllowContextEdit = false;
         PlaceAndShow(window, x, y, activate: false);
-        window.DonutControl.PlayOpenAnimation();
     }
 
     /// <summary>Opens the donut for known files (click mode).</summary>

src/Filee.App/ViewModels/Pages/GeneralPageViewModel.cs

@@ -85,7 +85,16 @@ private async Task ChangeModernMenu(bool enabled)
             return;
         ModernMenuBusy = true;
         ModernMenuStatus = _loc["general.modern_menu_busy"];
-        var result = await _platform.SetModernContextMenuAsync(enabled, exe);
+        ModernContextMenuResult result;
+        try
+        {
+            result = await _platform.SetModernContextMenuAsync(enabled, exe);
+        }
+        catch (Exception ex) when (ex is not OutOfMemoryException)
+        {
+            // A command that throws would end the app (async void path): report it on the page instead.
+            result = new ModernContextMenuResult(false, Error: ex.Message);
+        }
         ModernMenuBusy = false;
         RefreshModernMenu();
         if (result.Cancelled)

src/Filee.App/ViewModels/RadialViewModel.cs

@@ -20,6 +20,18 @@ public sealed partial class RadialViewModel(UserDataStore store, ILocalizer loc,
     [ObservableProperty] private double _holeRatio = 0.42;
     [ObservableProperty] private double _sliceOpacity = 0.96;
 
+    /// <summary>
+    /// 0 while a drag gesture waits for files, 1 otherwise. The gesture starts before anyone knows what is being
+    /// dragged (a file, text, or nothing: Ctrl + a rubber-band selection), so the donut only appears when files enter.
+    /// </summary>
+    [ObservableProperty] private double _donutOpacity = 1;
+
+    /// <summary>
+    /// Background of the window while the donut is hidden: practically invisible, but not fully transparent, so
+    /// Windows still delivers the drag to this window and the files can arrive.
+    /// </summary>
+    [ObservableProperty] private string _hitBackground = "Transparent";
+
     /// <summary>Files the donut will convert (empty while waiting for a drag to enter).</summary>
     public IReadOnlyList<string> Files { get; private set; } = [];
 
@@ -41,13 +53,17 @@ public void ResetForDrag()
         Items = [];
         CenterTitle = loc["donut.center_drag"];
         CenterSubtitle = null;
+        DonutOpacity = 0;
+        HitBackground = "#01000000";
     }
 
     /// <summary>Fills the donut for the given files.</summary>
     public void Load(IReadOnlyList<string> files, bool clickMode)
     {
         IsClickMode = clickMode;
         Files = files;
+        DonutOpacity = 1;
+        HitBackground = "Transparent";
         ApplyAppearance();
 
         var profile = ProfileSelector.Select(store.Profiles, files);

src/Filee.App/Views/RadialWindow.axaml

@@ -18,8 +18,9 @@
         ShowActivated="False"
         CanResize="False"
         SizeToContent="WidthAndHeight">
-  <Panel x:Name="Root" Background="Transparent" DragDrop.AllowDrop="True">
+  <Panel x:Name="Root" Background="{Binding HitBackground}" DragDrop.AllowDrop="True">
     <c:DonutMenu x:Name="Donut"
+                 Opacity="{Binding DonutOpacity}"
                  Items="{Binding Items}"
                  CenterTitle="{Binding CenterTitle}"
                  CenterSubtitle="{Binding CenterSubtitle}"

src/Filee.Platform.Windows/ExplorerMenuRegistration.cs

@@ -282,7 +282,20 @@ public static string ShortenDeploymentError(string message)
         return string.Join(' ', message.Split(['\r', '\n'], StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries));
     }
 
-    private static unsafe string? ExternalLocationOf(string fullName)
+    /// <summary>The install folder the package points to, or null when Windows can't tell.</summary>
+    public static unsafe string? ExternalLocationOf(string fullName)
+    {
+        try
+        {
+            return ExternalLocationOfCore(fullName);
+        }
+        catch (Exception ex) when (ex is EntryPointNotFoundException or DllNotFoundException)
+        {
+            return null; // older Windows without the API: the folder is then not compared
+        }
+    }
+
+    private static unsafe string? ExternalLocationOfCore(string fullName)
     {
         uint length = 0;
         if (NativeMethods.GetPackagePathByFullName2(fullName, NativeMethods.PackagePathType_EffectiveExternal, ref length, null)

src/Filee.Platform.Windows/NativeMethods.cs

@@ -58,7 +58,8 @@ public unsafe struct PACKAGE_ID
     [LibraryImport("kernel32.dll", StringMarshalling = StringMarshalling.Utf16)]
     public static unsafe partial int GetPackagesByPackageFamily(string packageFamilyName, ref uint count, char** packageFullNames, ref uint bufferLength, char* buffer);
 
-    [LibraryImport("kernel32.dll", StringMarshalling = StringMarshalling.Utf16)]
+    // Not exported by kernel32.dll (only by kernelbase.dll): import it from its API set, Windows 10 1903 and later.
+    [LibraryImport("api-ms-win-appmodel-runtime-l1-1-3.dll", StringMarshalling = StringMarshalling.Utf16)]
     public static unsafe partial int GetPackagePathByFullName2(string packageFullName, int packagePathType, ref uint pathLength, char* path);
 
     [LibraryImport("kernel32.dll")]

src/Filee.Platform.Windows/WindowsPlatformServices.cs

@@ -139,20 +139,39 @@ public void SetContextMenu(bool enabled, string executablePath, string label)
         CreateShortcut(SendToShortcutPath, executablePath, "--convert", label);
     }
 
-    public ModernContextMenuState GetModernContextMenuState(string executablePath) =>
-        Path.GetDirectoryName(executablePath) is { Length: > 0 } folder
-            ? ExplorerMenuRegistration.GetState(folder)
-            : ModernContextMenuState.Unsupported;
+    public ModernContextMenuState GetModernContextMenuState(string executablePath)
+    {
+        try
+        {
+            return Path.GetDirectoryName(executablePath) is { Length: > 0 } folder
+                ? ExplorerMenuRegistration.GetState(folder)
+                : ModernContextMenuState.Unsupported;
+        }
+        catch (Exception ex) when (ex is not OutOfMemoryException)
+        {
+            // Asking Windows about packages must never take the app or the settings page down.
+            Trace.TraceWarning($"Reading the Explorer menu state failed: {ex}");
+            return ModernContextMenuState.Unsupported;
+        }
+    }
 
     public Task<ModernContextMenuResult> SetModernContextMenuAsync(bool enabled, string executablePath) => Task.Run(async () =>
     {
         var folder = Path.GetDirectoryName(executablePath);
         if (string.IsNullOrEmpty(folder))
             return new ModernContextMenuResult(false, Error: "Unknown install folder.");
 
-        var result = enabled
-            ? await ExplorerMenuRegistration.AddAsync(folder)
-            : await ExplorerMenuRegistration.RemoveAsync(allowElevation: true);
+        ModernContextMenuResult result;
+        try
+        {
+            result = enabled
+                ? await ExplorerMenuRegistration.AddAsync(folder)
+                : await ExplorerMenuRegistration.RemoveAsync(allowElevation: true);
+        }
+        catch (Exception ex) when (ex is not OutOfMemoryException)
+        {
+            result = new ModernContextMenuResult(false, Error: ex.Message);
+        }
 
         // Keep exactly one entry: the title file exists while the Explorer menu setting is on.
         if (ExplorerMenuRegistration.ReadTitle() is { Length: > 0 } title)

tests/Filee.App.Tests/ExplorerMenuTests.cs

@@ -90,6 +90,35 @@ public void Family_name_matches_what_Windows_computes_from_the_publisher()
         Assert.Equal(ExplorerMenuPackage.FamilyName, ExplorerMenuRegistration.ComputeFamilyName());
     }
 
+    [Fact]
+    public void Every_native_import_exists_in_the_dll_it_names()
+    {
+        // GetPackagePathByFullName2 was imported from kernel32.dll, which doesn't export it: the call only failed
+        // once a package was registered and crashed the app right after "Add to the main menu" (1.1.0).
+        var nativeMethods = typeof(ExplorerMenuRegistration).Assembly.GetType("Filee.Platform.Windows.NativeMethods", throwOnError: true)!;
+        var imports = nativeMethods.GetMethods(System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic)
+            .Select(m => (Method: m, Import: m.GetCustomAttributes(typeof(LibraryImportAttribute), false).OfType<LibraryImportAttribute>().FirstOrDefault()))
+            .Where(m => m.Import is not null)
+            .ToList();
+        Assert.NotEmpty(imports);
+        Assert.All(imports, m =>
+        {
+            var entryPoint = m.Import!.EntryPoint ?? m.Method.Name;
+            Assert.True(NativeLibrary.TryLoad(m.Import.LibraryName, out var library), $"{m.Import.LibraryName} can't be loaded");
+            Assert.True(NativeLibrary.TryGetExport(library, entryPoint, out _), $"{m.Import.LibraryName} has no {entryPoint}");
+        });
+    }
+
+    [Fact]
+    public void Reading_the_registered_package_never_throws()
+    {
+        Assert.Null(ExplorerMenuRegistration.ExternalLocationOf("Filee.NotInstalled_1.0.0.0_x64__0000000000000"));
+        // Whatever is registered on this machine (nothing on CI): a registered sparse package has an external location.
+        if (ExplorerMenuRegistration.Find() is { } package)
+            Assert.False(string.IsNullOrEmpty(package.ExternalLocation), package.FullName);
+        _ = ExplorerMenuRegistration.GetState(BuiltFolder);
+    }
+
     [Fact]
     public void PowerShell_literals_escape_straight_and_typographic_single_quotes()
     {

tests/Filee.App.Tests/RenderTests.cs

@@ -125,7 +125,11 @@ public void Donut_toolbar_waits_for_files_in_drag_mode()
         Pump();
 
         Assert.Empty(vm.Items);
+        // Nothing shows until files are dragged in (a Ctrl + drag without files must not open anything).
+        Assert.Equal(0, vm.DonutOpacity);
         Save(window, "donut-drag-waiting.png");
+        vm.Load([@"C:\photos\a.jpg"], clickMode: false);
+        Assert.Equal(1, vm.DonutOpacity);
         window.Close();
     }