added statup with Windows feature

CursorLang/Interop/PackageIdentityNative.cs

@@ -0,0 +1,38 @@
+using System.Runtime.InteropServices;
+
+namespace CursorLang.Interop;
+
+/// <summary>
+/// Answers whether the application runs from an MSIX package.
+/// </summary>
+/// <remarks>
+/// The same application runs both installed from the Store and simply unpacked
+/// into a folder. Some Windows features — startup through <c>StartupTask</c>, for
+/// instance — are available only to a package, and reaching for them without a
+/// check is not allowed: outside a package they throw.
+/// </remarks>
+internal static class PackageIdentityNative
+{
+    /// <summary>APPMODEL_ERROR_NO_PACKAGE — the process runs outside a package.</summary>
+    private const int NoPackage = 15700;
+
+    /// <summary>
+    /// The application runs from an MSIX package.
+    /// </summary>
+    /// <remarks>
+    /// The value is computed once: it cannot change during the lifetime of
+    /// the process.
+    /// </remarks>
+    internal static bool IsPackaged { get; } = DetectPackage();
+
+    private static bool DetectPackage()
+    {
+        // The answer comes from the return code rather than from the name itself, so
+        // no buffer is needed: with zero length a package replies complaining about space
+        uint length = 0;
+        return GetCurrentPackageFullName(ref length, IntPtr.Zero) != NoPackage;
+    }
+
+    [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+    private static extern int GetCurrentPackageFullName(ref uint packageFullNameLength, IntPtr packageFullName);
+}

CursorLang/Services/IStartupService.cs

@@ -0,0 +1,18 @@
+using CursorLang.Models;
+
+namespace CursorLang.Services;
+
+/// <summary>
+/// Starting the app together with Windows.
+/// </summary>
+public interface IStartupService
+{
+    /// <summary>Finds out the current state of startup.</summary>
+    Task<StartupState> GetStateAsync();
+
+    /// <summary>
+    /// Asks for startup to be switched on or off and answers with the state that
+    /// came of it: the request to switch it on may well be turned down.
+    /// </summary>
+    Task<StartupState> SetEnabledAsync(bool enabled);
+}

CursorLang/Services/RegistryStartup.cs

@@ -0,0 +1,120 @@
+using System.IO;
+using System.Security;
+using CursorLang.Models;
+using Microsoft.Win32;
+
+namespace CursorLang.Services;
+
+/// <summary>
+/// Startup for a build that is not a package: a value under the Run key.
+/// </summary>
+/// <remarks>
+/// A package declares its startup task in the manifest and asks Windows to switch
+/// it on. A build unpacked into a folder has no manifest, so it registers itself
+/// the way desktop programs always have — under the Run key of the current user.
+/// Administrator rights are not needed for that: the key belongs to the user.
+///
+/// Windows keeps the user's own verdict apart from the entry itself. Turning the
+/// app off in Settings — Apps — Startup leaves the Run value where it is and marks
+/// it disabled under StartupApproved. The mark is obeyed here the same way a
+/// package obeys DisabledByUser: the app does not argue with the user.
+/// </remarks>
+internal sealed class RegistryStartup
+{
+    private const string RunPath = @"Software\Microsoft\Windows\CurrentVersion\Run";
+
+    private const string ApprovedPath =
+        @"Software\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run";
+
+    /// <summary>The name of the value — Windows shows it in the startup list.</summary>
+    private const string ValueName = "CursorLang";
+
+    private readonly RegistryKey _root;
+    private readonly string? _command;
+
+    internal RegistryStartup()
+        : this(Registry.CurrentUser, GetCommand())
+    {
+    }
+
+    /// <summary>A root of the test's own, so that the real startup list is left alone.</summary>
+    internal RegistryStartup(RegistryKey root, string? command)
+    {
+        _root = root;
+        _command = command;
+    }
+
+    internal StartupState GetState()
+    {
+        if (_command is null)
+        {
+            return StartupState.Unavailable;
+        }
+
+        try
+        {
+            using RegistryKey? run = _root.OpenSubKey(RunPath);
+
+            if (run?.GetValue(ValueName) is null)
+            {
+                return StartupState.Disabled;
+            }
+
+            return IsApprovedByUser() ? StartupState.Enabled : StartupState.DisabledByUser;
+        }
+        catch (Exception e) when (e is SecurityException or UnauthorizedAccessException or IOException)
+        {
+            return StartupState.Unavailable;
+        }
+    }
+
+    internal StartupState SetEnabled(bool enabled)
+    {
+        if (_command is null)
+        {
+            return StartupState.Unavailable;
+        }
+
+        try
+        {
+            using RegistryKey run = _root.CreateSubKey(RunPath);
+
+            if (enabled)
+            {
+                // The path is written afresh every time: the app may have been moved
+                run.SetValue(ValueName, _command, RegistryValueKind.String);
+            }
+            else
+            {
+                run.DeleteValue(ValueName, throwOnMissingValue: false);
+            }
+        }
+        catch (Exception e) when (e is SecurityException or UnauthorizedAccessException or IOException)
+        {
+            return StartupState.Unavailable;
+        }
+
+        // The answer is read back rather than assumed: an entry the user has
+        // banned stays banned no matter what was just written next to it
+        return GetState();
+    }
+
+    /// <summary>
+    /// Whether the user has left the entry alone. The verdict is a blob whose
+    /// lowest bit of the first byte stands for the ban; no value means untouched.
+    /// </summary>
+    private bool IsApprovedByUser()
+    {
+        using RegistryKey? approved = _root.OpenSubKey(ApprovedPath);
+
+        return approved?.GetValue(ValueName) is not byte[] { Length: > 0 } verdict
+            || (verdict[0] & 1) == 0;
+    }
+
+    /// <summary>
+    /// What Windows is to run. <c>null</c> — the path of the running program is
+    /// unknown, and there is nothing to write down.
+    /// </summary>
+    private static string? GetCommand() =>
+        Environment.ProcessPath is { Length: > 0 } path ? $"\"{path}\"" : null;
+}

CursorLang/Services/StartupService.cs

@@ -0,0 +1,85 @@
+using System.Runtime.InteropServices;
+using CursorLang.Interop;
+using CursorLang.Models;
+using Windows.ApplicationModel;
+
+namespace CursorLang.Services;
+
+/// <summary>
+/// Startup, arranged by whatever means the current build has.
+/// </summary>
+/// <remarks>
+/// Startup used to be a scheduled task with the highest rights — otherwise an app
+/// that wanted administrator rights would not start from the startup folder. The
+/// app needs no such rights any more, and the two ways left are simpler.
+///
+/// A package declares the task in its manifest, and Windows lists it for the user
+/// next to the rest under Settings — Apps — Startup. Turned off there, it can no
+/// longer be turned back on by the app. Outside a package the same setting is kept
+/// in the registry: see <see cref="RegistryStartup"/>.
+/// </remarks>
+public sealed class StartupService : IStartupService
+{
+    /// <summary>Matches TaskId in the package manifest.</summary>
+    private const string TaskId = "CursorLangStartup";
+
+    private readonly RegistryStartup _registry = new();
+
+    public async Task<StartupState> GetStateAsync()
+    {
+        if (!PackageIdentityNative.IsPackaged)
+        {
+            return _registry.GetState();
+        }
+
+        try
+        {
+            StartupTask task = await StartupTask.GetAsync(TaskId);
+            return Translate(task.State);
+        }
+        catch (Exception e) when (e is COMException or ArgumentException or InvalidOperationException)
+        {
+            // No task by that name in the manifest: that happens to a package put
+            // together by hand. The setting simply will not show
+            return StartupState.Unavailable;
+        }
+    }
+
+    public async Task<StartupState> SetEnabledAsync(bool enabled)
+    {
+        if (!PackageIdentityNative.IsPackaged)
+        {
+            return _registry.SetEnabled(enabled);
+        }
+
+        try
+        {
+            StartupTask task = await StartupTask.GetAsync(TaskId);
+
+            if (!enabled)
+            {
+                task.Disable();
+                return Translate(task.State);
+            }
+
+            // Windows answers with a state rather than with success: once the user
+            // has forbidden startup, the ban stays
+            return Translate(await task.RequestEnableAsync());
+        }
+        catch (Exception e) when (e is COMException or ArgumentException or InvalidOperationException)
+        {
+            return StartupState.Unavailable;
+        }
+    }
+
+    /// <summary>The state of a Windows task in the app's own terms.</summary>
+    internal static StartupState Translate(StartupTaskState state) => state switch
+    {
+        StartupTaskState.Enabled => StartupState.Enabled,
+        StartupTaskState.EnabledByPolicy => StartupState.EnabledByPolicy,
+        StartupTaskState.Disabled => StartupState.Disabled,
+        StartupTaskState.DisabledByUser => StartupState.DisabledByUser,
+        StartupTaskState.DisabledByPolicy => StartupState.DisabledByPolicy,
+        _ => StartupState.Unavailable,
+    };
+}