PattN macOS: crash on launch — null ToolTipText in Avalonia TrayIcon.Attach()

خلاصه فارسی (TL;DR)

روی macOS جدید (27.0.1 / build 26A434، Apple Silicon) اپ PattN هنگام اجرا کرش می‌کند و
هیچ پنجره‌ای باز نمی‌شود. علت: در App.axaml خط ۴۰ برای TrayIcon مقدار
ToolTipText="{Binding RunningServerToolTipText}" ست شده، ولی آیکون تری در
App.Initialize() ساخته می‌شود، یعنی قبل از اینکه DataContext ست شود؛ در نتیجه مقدار
null به SetToolTipText می‌رسد و Avalonia 12.1.x آن را بدون چک null به
UTF8Encoding.GetByteCount می‌دهد → ArgumentNullException → abort().
این مشکل در هر ۴ ریلیز فعلی (P26, P27, P28, P29) وجود دارد.
راه‌حل پیشنهادی: یک FallbackValue غیر-null برای binding، یا ست کردن ToolTipText
ثابت، یا ساختن tray icon بعد از آماده شدن ViewModel.

Environment

• OS: macOS 27.0.1 (build 26A434), arm64 (Apple Silicon)
• PattN: 7.25.2-P29, asset PattN-macos-arm64.dmg
• Also reproduced on: P28 (7.25.2-P28), P27, P26 as shipped — all four current releases
  contain the same binding (verified by reading App.axaml at each tag)
• Avalonia.Desktop: 12.1.3 (my-releases); 12.1.2 in P26/P27/P28
• Signature: adhoc / TeamIdentifier not set (not notarized), launched without quarantine
• Launch method: both open -a /Applications/PattN.app and running
  /Applications/PattN.app/Contents/MacOS/PattN directly → identical crash

Steps to reproduce

1. Download PattN-macos-arm64.dmg from release 7.25.2-P29 and install PattN.app.
2. Launch PattN.app.
3. Expected: main window appears.
   Actual: process aborts within ~1s, no window at all, every launch.

Actual result

Unhandled managed exception; process aborts (SIGABRT). Captured on stderr when the
binary is run from a terminal:

Unhandled exception. System.ArgumentNullException: ArgumentNull_Generic Arg_ParamName_Name, chars
   at System.Text.UTF8Encoding.GetByteCount(String chars)
   at Avalonia.Native.Interop.Impl.__MicroComIAvnTrayIconProxy.SetToolTipText(String text)
   at Avalonia.Native.TrayIconImpl.SetToolTipText(String text)
   at Avalonia.Controls.TrayIcon.Attach()
   at Avalonia.Controls.TrayIcon.AttachIcons(IEnumerable`1 icons)
   at Avalonia.Controls.TrayIcon.<>c.<.cctor>b__4_0(AvaloniaPropertyChangedEventArgs`1 args)
   at Avalonia.Reactive.AnonymousObserver`1.OnNext(T value)
   at Avalonia.Reactive.LightweightObservableBase`1.PublishNext(T value)
   at Avalonia.Reactive.LightweightSubject`1.OnNext(T value)
   at Avalonia.AvaloniaProperty`1.NotifyChanged(AvaloniaPropertyChangedEventArgs`1 e)
   at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaProperty`1 property, ...)
   at Avalonia.PropertyStore.EffectiveValue`1.NotifyValueChanged(ValueStore owner, ...)
   at Avalonia.PropertyStore.ValueStore.SetValue[T](StyledProperty`1 property, ...)
   at Avalonia.AvaloniaObject.SetValue[T](StyledProperty`1 property, T value, BindingPriority priority)
   at Avalonia.Controls.TrayIcon.SetIcons(Application o, TrayIcons trayIcons)
   at v2rayN.Desktop.App.!XamlIlPopulate(IServiceProvider, App) in App.axaml:line 79
   at v2rayN.Desktop.App.!XamlIlPopulateTrampoline(App)
   at v2rayN.Desktop.App.Initialize() in App.axaml.cs:line 10
   at Avalonia.AppBuilder.SetupUnsafe()
   at Avalonia.AppBuilder.Setup()
   at Avalonia.AppBuilder.SetupWithLifetime(IApplicationLifetime lifetime)
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime(...)
   at v2rayN.Desktop.Program.Main(String[] args) in Program.cs:line 22

Crash report also written to ~/Library/Logs/DiagnosticReports/PattN-2026-10-02-132415.ips:
exception: EXC_CRASH / SIGABRT, termination: Abort trap: 6,
faulting frames: abort → TerminateProcess → DispatchManagedException → IL_Throw.

Root cause

v2rayN/v2rayN.Desktop/App.axaml line 40:

<TrayIcon
    Command="{Binding NotifyLeftClickCmd}"
    Icon="/Assets/NotifyIcon1.ico"
    ToolTipText="{Binding RunningServerToolTipText}">

The <TrayIcon.Icons> block is part of the Application XAML, so the tray icon is
attached during App.Initialize() — before any DataContext / StatusBarViewModel
exists. The binding therefore evaluates to null, and Avalonia.Controls.TrayIcon.Attach()
passes that null straight to TrayIconImpl.SetToolTipText().
Avalonia 12.1.x marshals the argument into UTF8Encoding.GetByteCount(string), which
throws ArgumentNullException on null → unhandled → abort().

Because this happens during application initialization, it is deterministic on every
launch (not a race), and it explains why no window is ever shown.

Suggested fixes (any one is enough)

1. Give the binding a non-null fallback:
   ToolTipText="{Binding RunningServerToolTipText, FallbackValue=PattN}"
2. Or set a static tooltip: ToolTipText="PattN" and update it later from code when the
   view-model is ready.
3. Or move tray-icon creation out of App.axaml and attach it after the main window /
   StatusBarViewModel DataContext is established.
4. Upstream/Avalonia-side: treat null as "" in TrayIconImpl.SetToolTipText (defensive
   null handling) — this is arguably the real bug in Avalonia's macOS backend.
5. If pinning Avalonia: verify whether 12.1.2 tolerated a null tooltip; if so, P26–P28 may
   only crash because the binding is present, and the same XAML guard fixes all of them.

Notes

• This may be specific to very new macOS (26A434); I could not find any release that
  launches successfully here, so please confirm whether the macOS build is expected to
  work on macOS 27.
• Workaround I used meanwhile: the bundled patched core at
  PattN.app/Contents/MacOS/bin/xray/xray (Xray 26.9.27) runs fine standalone with a
  hand-written config (verified with xray -test, including the finalmask fragment
  block and fingerprint=unsafe + cipherSuites). So only the GUI is affected, not the core.