Window hide/show loop (~60 Hz) when "Minimize to the tray" is enabled but no system tray exists (GNOME Wayland), breaks alt-tab session-wide

Start in src/qt/bitcoingui.cpp at BitcoinGUI::changeEvent(), where minimize-to-tray handling hides the window. Check how QSystemTrayIcon::isSystemTrayAvailable() relates to the existing tray-icon creation guard. Done means the minimize-to-tray path no longer loops when no system tray exists, while tray behavior remains available when one exists.

bitcoin-qt v29.0, started with -min and with "Minimize to the tray instead of the taskbar" enabled, on a desktop with no system tray (stock GNOME 48, Wayland, no AppIndicator extension), enters a loop where its window is destroyed and re-created continuously at about 60Hz window-created events.

Environment

• Bitcoin Core v29.0 (official binaries, /home/leo/bitcoin/bitcoin-29.0/bin/bitcoin-qt -min -chain=main)
• Debian 13 (trixie), GNOME Shell 48 on Wayland; bitcoin-qt runs via XWayland
• No system tray: stock GNOME, no AppIndicator/StatusNotifier extension installed

Symptoms

• A generic (icon-less) entry flickers in the alt-tab switcher / dock.
• Every re-map re-enters the window as "most recent" in the alt-tab order and can steal focus at the moment of switching: alt-tab and overview clicks fail ~30% of the time for every application on the desktop, not just bitcoin-qt.
• gnome-shell burns CPU constantly from the restacking (42% of one core sustained; 4+ days of CPU time accumulated over 9 days of uptime).
• The user-visible damage started after updating to Debian Trixie (GNOME 43 to 48 probably marked the AppIndicator extension incompatible and switch it off) which removed the tray. It persisted for days; no crash-looping process exists, so ps looks clean. Only shell-level instrumentation identified the culprit.

Diagnosis

GNOME Shell hook:

global.display.connect('window-created', (d, w) =>
  log('FLICK pid=' + w.get_pid() + ' class=' + w.get_wm_class() + ' title=' + w.get_title()));

Output (repeating ~60x/second):

Aug 21 19:49:45 debian gnome-shell[3296]: FLICK pid=3475 class=Bitcoin-Qt title=Bitcoin Core type=0

pid 3475 = the bitcoin-qt process above.

In v29 src/qt/bitcoingui.cpp, BitcoinGUI::changeEvent() hides the window on minimize whenever getMinimizeToTray() is set. The option is honored even when QSystemTrayIcon::isSystemTrayAvailable() is false (that check only guards tray-icon creation). With no tray to land in, the hide/re-show cycle repeats indefinitely on this setup.

Workaround

Disable minimize to tray in the config file. In the options window it's grayed out.

Suggested fix direction

Gate the minimize-to-tray hide path on QSystemTrayIcon::isSystemTrayAvailable() (as PR bitcoin/bitcoin#691 once did for the -min startup phase), or force-disable the option at runtime when no tray exists.

Prior reports checked (none match)

• bitcoin/bitcoin#788 (2012, xmonad window flicker — same symptom family, ancient, closed)
• bitcoin/bitcoin#3789 (2014, -min + no tray → orphaned window; the "hide" half without the loop)
• bitcoin-core/gui#903 / #904 / #914 (2025, Qt6-native-Wayland flicker via bringToFront() — different mechanism; this box runs Qt5/XWayland)
• bitcoin-core/gui#405 (window disappears on Cinnamon)
• bitcoin-core/gui#748/#749 (-min vs. wallet loading dialog)