ilya-fedin

> The qt5 one now plumbs the app Id via `QApplication`, but couldn't do that in qt6 - I had to register the app ID before doing `QApplication a(argc, argv);`...

> Does this mean it would be more correct to call them as `QGuiApplication::setDesktopFileName(APP_ID)` and `QGuiApplication::desktopFileName()`, rather than `app->setDesktopFileName(APP_ID)` and `app->desktopFileName()`? Exactly