Program.cs

namespace CapsNumTray;

internal static class Program
{
    [STAThread]
    static void Main(string[] args)
    {
#if DEBUG
        // Debug-only DPI render harness — realizes each form at the real screen
        // DPI and dumps PNGs, then exits. Runs before the single-instance mutex
        // (it's a one-shot render, not a tray session) so it works alongside a
        // live instance on a test VM. Stripped from Release.
        if (args.Contains("--diag-render-form"))
        {
            DiagRender.Run(args);
            return;
        }
        if (args.Contains("--diag-measure-settings"))
        {
            DiagRender.MeasureSettings(args);
            return;
        }
        if (args.Contains("--diag-measure-update"))
        {
            DiagRender.MeasureUpdate(args);
            return;
        }
#endif

        bool isAfterUpdate = args.Contains("--after-update");
        // --after-theme-restart: dispatched by TrayApplication when the user
        // changes the Theme dropdown. Same mutex-retry treatment as --after-update
        // because we're racing the outgoing instance for the single-instance lock.
        bool isAfterThemeRestart = args.Contains("--after-theme-restart");

        // Single-instance: hold mutex for lifetime. Post-update / post-theme-restart
        // the outgoing exe needs a moment to release the mutex, so retry briefly
        // in those cases. Local\ scope — the tray is inherently per-session (icons
        // live in the session's explorer.exe), so Global\ would let user A block
        // user B on multi-session machines (RDS, fast user switching).
        Mutex mutex;
        bool createdNew;
        int remainingRetries = (isAfterUpdate || isAfterThemeRestart) ? 50 : 0;
        while (true)
        {
            try
            {
                mutex = new Mutex(true, @"Local\CapsNumTray_SingleInstance", out createdNew);
            }
            catch (Exception ex) when (
                ex is UnauthorizedAccessException     // restricted DACL / Session 0 / AppContainer
                or WaitHandleCannotBeOpenedException  // name collision with a different kernel object
                or IOException)                       // generic Win32 error leak from the ctor
            {
                // Any of these mean we cannot claim the single-instance lock.
                // Declining is safer than crashing with an unhandled exception.
                return;
            }
            if (createdNew || remainingRetries-- <= 0) break;
            mutex.Dispose();
            Thread.Sleep(100);
        }
        using var _mutex = mutex;
        if (!createdNew)
            return;

        UpdateDialog.CleanupUpdateArtifacts();

        // Self-heal startup shortcut if exe path has changed (e.g., winget upgrade)
        StartupManager.ValidateStartupPath();

        ApplicationConfiguration.Initialize();

        if (isAfterUpdate)
            UpdateDialog.ShowUpdateToast();
        if (isAfterThemeRestart)
            OsdForm.ShowDelayedOsd("Theme applied.", delayMs: 800, dwellMs: 1800);

        using var app = new TrayApplication();
        Application.Run(app);
    }
}