Sometimes GThread
s are created when you use functions that rely on async behaviour. These usually create a GTask
internally (with g_task_run_in_thread
and friends) and run the synchronous version in a seperate thread (except for those being nativly async or async-able, those usually won't spawn another thread). Usually this is IO (i.e. GtkBuilder), Socket and IPC (dbus) related - so mostly glib
stuff.
There might also be occasions which I am not aware of, that will spawn additional threads, the mainloop itself is strictly single threaded.
So in your case I can only think of two thing that could trigger this: The Stock image that is loaded from your local disk or the styling information of your theme.