Restore Mac Application Window after Cmd-H

If you have hidden an OS X Application with Cmd-H (aka Apple-H = ⌘-H) the hidden window cannot be shown again by calling slot show(). In this case you must call

raise();
// maybe additionally to activate the window:
activateWindow();

If you have installed a system tray icon with QSystemTrayIcon you can add a menu entry and connect the QAction's triggered() signal with the respecitve slots.