(gdb) bt
#0  0x0000000000000000 in  ()
#1  0x00007ffff59902fa in QApplication::setActiveWindow(QWidget*) () at /usr/lib/libQt5Widgets.so.5
#2  0x00007ffff59905fc in QApplicationPrivate::notifyActiveWindowChange(QWindow*) () at /usr/lib/libQt5Widgets.so.5
#3  0x00007ffff52abe0d in QGuiApplicationPrivate::processActivatedEvent(QWindowSystemInterfacePrivate::ActivatedWindowEvent*) ()
    at /usr/lib/libQt5Gui.so.5
#4  0x00007ffff52b0c3b in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) ()
    at /usr/lib/libQt5Gui.so.5
#5  0x00007ffff5289c2c in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
    at /usr/lib/libQt5Gui.so.5
#6  0x00007fffec29ebac in  () at /usr/lib/libQt5XcbQpa.so.5
#7  0x00007ffff6a4751e in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#8  0x00007ffff6a492d1 in  () at /usr/lib/libglib-2.0.so.0
#9  0x00007ffff6a49311 in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#10 0x00007ffff780d020 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
    at /usr/lib/libQt5Core.so.5
#11 0x00007ffff77b34cc in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#12 0x00007ffff77bb4d6 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5
#13 0x0000555555877cf6 in main ()