Handle unsupported HID descriptors in CopperPad GUI

CopperPad.Gui/MainWindow.cs

@@ -75,7 +75,7 @@ public MainWindow()
 		MinHeight = 640;
 		Content = BuildContent();
 
-		_host.DevicesChanged += (_, args) => Dispatcher.UIThread.Post(() => OnDevicesChanged(args.Devices));
+		_host.DevicesChanged += (_, args) => Dispatcher.UIThread.Post(() => OnDevicesChanged(args));
 		_host.RawReportReceived += (_, args) => Dispatcher.UIThread.Post(() => OnRawReport(args));
 		_host.StateChanged += (_, args) => Dispatcher.UIThread.Post(() => OnStateChanged(args.State));
 		Opened += async (_, _) => await InitializeAsync().ConfigureAwait(true);
@@ -365,17 +365,30 @@ private async Task InitializeAsync()
 			SetStatus("Profile load failed: " + ex.Message);
 		}
 
-		_host.Start();
+		StartHost();
 	}
 
 	private void RefreshDevices()
 	{
-		_host.Stop();
-		_host.Start();
+		try
+		{
+			_host.Stop();
+			_host.Start();
+		}
+		catch (Exception ex) when (IsRecoverableHidException(ex))
+		{
+			SetStatus("Controller refresh failed: " + ex.Message);
+		}
 	}
 
-	private void OnDevicesChanged(IReadOnlyList<HidDeviceInfo> devices)
+	private void OnDevicesChanged(HidDevicesChangedEventArgs args)
 	{
+		var devices = args.Devices;
+		if (!string.IsNullOrWhiteSpace(args.Diagnostic))
+		{
+			SetStatus(args.Diagnostic);
+		}
+
 		var selectedId = _selectedDevice?.Id;
 		var items = devices.Select(device => new DeviceListItem(device)).ToArray();
 		_deviceList.ItemsSource = items;
@@ -392,6 +405,18 @@ private void OnDevicesChanged(IReadOnlyList<HidDeviceInfo> devices)
 		}
 	}
 
+	private void StartHost()
+	{
+		try
+		{
+			_host.Start();
+		}
+		catch (Exception ex) when (IsRecoverableHidException(ex))
+		{
+			SetStatus("Controller scan failed: " + ex.Message);
+		}
+	}
+
 	private void SelectDevice(HidDeviceInfo? device)
 	{
 		_selectedDevice = device;
@@ -932,6 +957,9 @@ private static void AddCell(Grid grid, Control control, int row, int column)
 	private static int DecimalToInt(decimal? value)
 		=> (int)(value ?? 0);
 
+	private static bool IsRecoverableHidException(Exception ex)
+		=> ex is IOException or InvalidOperationException or TimeoutException or UnauthorizedAccessException or NotSupportedException;
+
 	private static string ToHexRows(byte[] bytes)
 	{
 		if (bytes.Length == 0)

CopperPad.Tests/ControllerDiagnosticsTests.cs

@@ -20,6 +20,21 @@ public void DiagnosticsHost_EnumeratesAllHidDevices()
 		Assert.Equal(observed, host.GetDevices());
 	}
 
+	[Fact]
+	public void DiagnosticsHost_PublishesScanDiagnosticWhenEnumerationFails()
+	{
+		var provider = new FakeHidDeviceProvider { GetDevicesException = new NotSupportedException("descriptor unavailable") };
+		using var host = new ControllerDiagnosticsHost(provider, new ControllerHostOptions());
+		HidDevicesChangedEventArgs? observed = null;
+		host.DevicesChanged += (_, args) => observed = args;
+
+		host.Start();
+
+		Assert.Empty(host.GetDevices());
+		Assert.NotNull(observed);
+		Assert.Equal("HID scan failed: descriptor unavailable", observed.Diagnostic);
+	}
+
 	[Fact]
 	public async Task DiagnosticsHost_PublishesRawReportsAndProfileMappedState()
 	{
@@ -89,10 +104,19 @@ private sealed class FakeHidDeviceProvider : IHidDeviceProvider
 		private readonly Dictionary<string, FakeHidInputStream> _streams = new(StringComparer.Ordinal);
 		private IReadOnlyList<HidDeviceDescriptor> _devices = Array.Empty<HidDeviceDescriptor>();
 
+		public Exception? GetDevicesException { get; init; }
+
 		public event EventHandler? Changed;
 
 		public IReadOnlyList<HidDeviceDescriptor> GetDevices()
-			=> _devices;
+		{
+			if (GetDevicesException != null)
+			{
+				throw GetDevicesException;
+			}
+
+			return _devices;
+		}
 
 		public IHidInputStream Open(HidDeviceDescriptor device, TimeSpan readTimeout)
 			=> _streams.TryGetValue(device.Id, out var stream)

CopperPad/ControllerDiagnostics.cs

@@ -12,9 +12,10 @@ public sealed record HidDeviceInfo(
 	bool ReportsUseId,
 	string? Diagnostic);
 
-public sealed class HidDevicesChangedEventArgs(IReadOnlyList<HidDeviceInfo> devices) : EventArgs
+public sealed class HidDevicesChangedEventArgs(IReadOnlyList<HidDeviceInfo> devices, string? diagnostic = null) : EventArgs
 {
 	public IReadOnlyList<HidDeviceInfo> Devices { get; } = devices;
+	public string? Diagnostic { get; } = diagnostic;
 }
 
 public sealed class ControllerRawReportReceivedEventArgs(HidDeviceInfo device, byte[] report, int length, DateTimeOffset timestamp) : EventArgs
@@ -38,6 +39,7 @@ public sealed class ControllerDiagnosticsHost : IDisposable
 	private IReadOnlyList<HidDeviceDescriptor> _descriptors = Array.Empty<HidDeviceDescriptor>();
 	private IReadOnlyList<HidDeviceInfo> _devices = Array.Empty<HidDeviceInfo>();
 	private ControllerProfileSet _profiles;
+	private string? _diagnostic;
 	private string? _selectedDeviceId;
 	private CancellationTokenSource? _readerCancellation;
 	private Task? _readerTask;
@@ -168,12 +170,27 @@ private void OnProviderChanged(object? sender, EventArgs args)
 
 	private void RescanLocked(bool restartReader)
 	{
-		_descriptors = _provider.GetDevices()
-			.GroupBy(device => device.Id, StringComparer.Ordinal)
-			.Select(group => group.First())
-			.OrderBy(device => device.ProductName, StringComparer.OrdinalIgnoreCase)
-			.ThenBy(device => device.Id, StringComparer.Ordinal)
-			.ToArray();
+		try
+		{
+			_descriptors = _provider.GetDevices()
+				.GroupBy(device => device.Id, StringComparer.Ordinal)
+				.Select(group => group.First())
+				.OrderBy(device => device.ProductName, StringComparer.OrdinalIgnoreCase)
+				.ThenBy(device => device.Id, StringComparer.Ordinal)
+				.ToArray();
+			_diagnostic = null;
+		}
+		catch (Exception ex) when (IsRecoverableHidException(ex))
+		{
+			StopReaderLocked();
+			_descriptors = Array.Empty<HidDeviceDescriptor>();
+			_devices = Array.Empty<HidDeviceInfo>();
+			_selectedDeviceId = null;
+			_diagnostic = "HID scan failed: " + ex.Message;
+			RaiseDevicesChangedLocked();
+			return;
+		}
+
 		_devices = _descriptors.Select(ToInfo).ToArray();
 		if (_selectedDeviceId != null && !_descriptors.Any(device => string.Equals(device.Id, _selectedDeviceId, StringComparison.Ordinal)))
 		{
@@ -260,7 +277,7 @@ private async Task ReadLoopAsync(HidDeviceDescriptor device, IControllerMapper m
 		catch (OperationCanceledException)
 		{
 		}
-		catch (Exception ex) when (ex is IOException or InvalidOperationException or TimeoutException or UnauthorizedAccessException)
+		catch (Exception ex) when (IsRecoverableHidException(ex))
 		{
 			var failed = info with { Diagnostic = "HID read failed: " + ex.Message };
 			var controller = new ControllerInfo(
@@ -276,7 +293,10 @@ private async Task ReadLoopAsync(HidDeviceDescriptor device, IControllerMapper m
 	}
 
 	private void RaiseDevicesChangedLocked()
-		=> DevicesChanged?.Invoke(this, new HidDevicesChangedEventArgs(_devices));
+		=> DevicesChanged?.Invoke(this, new HidDevicesChangedEventArgs(_devices, _diagnostic));
+
+	private static bool IsRecoverableHidException(Exception ex)
+		=> ex is IOException or InvalidOperationException or TimeoutException or UnauthorizedAccessException or NotSupportedException;
 
 	private void ThrowIfDisposed()
 	{

CopperPad/ControllerHost.cs

@@ -226,7 +226,7 @@ private async Task ReadLoopAsync()
 			catch (OperationCanceledException)
 			{
 			}
-			catch (Exception ex) when (ex is IOException or InvalidOperationException or TimeoutException or UnauthorizedAccessException)
+			catch (Exception ex) when (ex is IOException or InvalidOperationException or TimeoutException or UnauthorizedAccessException or NotSupportedException)
 			{
 				var diagnostic = "HID read failed: " + ex.Message;
 				Info = Info with { IsConnected = false, Diagnostic = diagnostic };

CopperPad/HidSharpDeviceProvider.cs

@@ -55,7 +55,7 @@ private static HidDeviceDescriptor CreateDescriptor(HidDevice device)
 				.SelectMany(report => report.GetAllUsages())
 				.Any(IsGameControllerUsage);
 		}
-		catch (Exception ex) when (ex is IOException or InvalidOperationException or ArgumentException)
+		catch (Exception ex) when (ex is IOException or InvalidOperationException or ArgumentException or NotSupportedException)
 		{
 			diagnostic = "Unable to parse HID report descriptor: " + ex.Message;
 		}
@@ -99,7 +99,7 @@ private static string SafeString(Func<string> getter, string? fallback, string d
 			var value = getter();
 			return string.IsNullOrWhiteSpace(value) ? fallback ?? defaultValue : value;
 		}
-		catch (Exception ex) when (ex is IOException or InvalidOperationException)
+		catch (Exception ex) when (ex is IOException or InvalidOperationException or NotSupportedException or UnauthorizedAccessException)
 		{
 			return string.IsNullOrWhiteSpace(fallback) ? defaultValue : fallback;
 		}