Fix tray icon missing when KeePassXC starts before the StatusNotifierWatcher

[tassiovirginio]

Summary

When KeePassXC starts before the StatusNotifierWatcher (system tray host) is available — e.g. right after login, before the shell is up, or after a tray-host restart — the tray icon never appears, and it never recovers even after the watcher shows up seconds later. The only way out was restarting the app.

This was reproducible on Wayland (niri + quickshell dms.service) and affects any SNI host that starts after KeePassXC.

Root cause (Qt 5.15)

Qt's generic Unix theme decides once per process whether a D-Bus tray is available:

// qgenericunixthemes.cpp (qtbase 5.15)
static bool isDBusTrayAvailable() {
    static bool dbusTrayAvailable = false;      // process-wide cache
    static bool dbusTrayAvailableKnown = false;
    if (!dbusTrayAvailableKnown) {
        QDBusMenuConnection conn;
        if (conn.isStatusNotifierHostRegistered())
            dbusTrayAvailable = true;
        dbusTrayAvailableKnown = true;
    }
    return dbusTrayAvailable;
}

If the first QSystemTrayIcon of the process is created while the watcher is absent, createPlatformSystemTrayIcon() returns nullptr: the icon never gets a real QDBusTrayIcon, /StatusNotifierItem is never exported, and recreating the icon later still hits the poisoned static cache — so no amount of show()/recreate retries can ever register.

Fix

• Defer icon creation until org.kde.StatusNotifierWatcher is present on the session bus, so Qt evaluates its one-shot cache with the watcher up and a real QDBusTrayIcon (with /StatusNotifierItem + /MenuBar) is born.
• Retry timer (5s) + QDBusServiceWatcher::serviceRegistered on org.kde.StatusNotifierWatcher to re-trigger registration as soon as a host appears (first-boot race and mid-session host restart both covered).
• Verify actual registration by querying RegisteredStatusNotifierItems and resolving the owning PID of each item — accepts org.kde.StatusNotifierItem-<pid>-<n>, org.freedesktop.StatusNotifierItem-<pid>-<n> and the dedicated QDBusMenuConnection unique name (e.g. :1.853/StatusNotifierItem).
• Guarded with Q_OS_UNIX && !Q_OS_MACOS && !QT_NO_DBUS; no change on Windows/macOS. Tray menu is now owned via QPointer so icon re-creation stays leak-free.

Testing

Validated live on the session bus with busctl while the real instance keeps running:

Scenario	Result
Watcher down at launch, comes up later	icon created on a dedicated connection ~6s after watcher appears, Id="KeePassXC", registered, stable (no churn)
Watcher up at launch (regression)	icon created immediately and registered — happy path unchanged
Watcher flap (stop+start mid-session)	re-registered in ~2s, stable afterwards

Before the fix, the watcher-down case never exported /StatusNotifierItem even after minutes; after the fix it registers without restarting the app.