Standalone Notifier IPC Subsystem

LocalTelemetry.Notifier is a standalone, lightweight WinForms executable (LocalTelemetry.Notifier.exe) targeting .NET 10 Windows x64, dedicated to rendering non-blocking desktop toast alert windows.

Why a Standalone Process?

Rendering alert windows with slide-in animations and auto-dismiss timers inside the main application process carries two key risks:

1. Focus Stealing: Window activation during full-screen gaming or video playback could cause games to lose keyboard focus or minimize to desktop
2. UI Thread Blocking: Animation loops on the main UI thread could delay telemetry sensor polling ticks

By spinning up LocalTelemetry.Notifier.exe as a secondary process, notifications display smoothly without stealing foreground focus or blocking hardware monitoring threads.

Named Pipe IPC Communication

LocalTelemetry.App launches LocalTelemetry.Notifier.exe passing its Parent Process ID (PID) as args[0]. Inter-process communication takes place over an asynchronous Windows Named Pipe (LocalTelemetryNotifier).

On-Demand Process Lifecycle

To conserve system resources, LocalTelemetry.Notifier.exe is not kept running unconditionally. App.xaml.cs dynamically controls the process lifecycle:

• EnsureNotifierLaunched(): Invoked on startup or when the user enables threshold alerts with toast notifications in Settings. Launches the executable with the current process ID as args[0].
• EnsureNotifierStopped(): Invoked when alerts or toast notifications are disabled in Settings, or when LocalTelemetry is closing. Dispatches a Shutdown IPC message over the named pipe and waits up to 2 seconds for a clean shutdown before terminating the process.

JSON Message Contract (NotificationMessage)

NotificationClient.cs serializes messages over the pipe in UTF-8 JSON Lines format:

{
    "Action": "ShowToast",
    "Title": "CPU Temperature Warning",
    "Body": "CPU reached 88°C (Limit: 85°C)",
    "Tag": "cpu_temp"
}

private sealed record NotificationMessage
{
    public string Action { get; set; } = string.Empty;
    public string? Title { get; set; }
    public string? Body { get; set; }
    public string? Tag { get; set; }
}

Command Actions

• ShowToast: Triggers ToastForm rendering on screen with Title and Body
• Shutdown: Gracefully cancels CancellationTokenSource and closes HiddenForm

Hidden Message Pump (HiddenForm)

Inside Program.cs, an invisible HiddenForm provides a WinForms message pump:

• Hidden from Alt+Tab via WS_EX_TOOLWINDOW (0x00000080) extended window style
• ShowInTaskbar = false, WindowState = Minimized, Opacity = 0
• Receives pipe messages on a background thread (RunPipeServerAsync) and dispatches toast creation to the UI thread via hiddenForm.BeginInvoke(...)

Toast Window Rendering & Animation

Implemented in ToastForm.cs, the window renders a custom dark alert popup:

• Dimensions: 320px width × 90px height.
• Appearance: Dark background (Color.FromArgb(32, 32, 32)), rounded corners (CornerRadius = 8 via GraphicsPath), border pen (Color.FromArgb(60, 60, 60)).
• Audio Cue: Plays system exclamation sound (SystemSounds.Exclamation.Play()).
• Ease-Out Slide-In Animation: OnLoad animates the window position from below the screen working area using a cubic ease-out curve (1.0 - Math.Pow(1.0 - t, 3)) over 300ms.
• Auto-Dismiss: A System.Windows.Forms.Timer automatically closes the toast window after 5000ms.

Parent Process Monitoring & Auto-Exit

When LocalTelemetry.Notifier.exe receives parentPid as args[0]:

1. Launches a background worker task: Process.GetProcessById(parentPid).WaitForExitAsync().
2. When the parent LocalTelemetry.exe process exits, the notifier process automatically logs exit and shuts down cleanly.

Notifier Diagnostic Logging

Implemented in NotifierLog.cs, LocalTelemetry.Notifier records its operational lifecycle, named pipe connections, and toast animations directly to lt_notifier.log:

• File Location: Uses the identical directory resolution rule as AppSettings (located in %LOCALAPPDATA%\LocalTelemetry\lt_notifier.log in standard mode, or alongside the executable in portable mode).
• Clean Shutdown: NotifierLog.Shutdown() flushes buffered log entries to disk when the message pump exits.