main_iteration
Runs a single iteration of the mainloop. If no events are waiting to be
processed GTK+ will block until the next event is noticed.
If you don't want to block look at
main_iteration_do() or check if any
events are pending with events_pending()
first.
If you ever change the UI and go on with time consuming processing, you
should update the UI (e.g. the progress bar) yourself by using the
following lines of code:
Returns true if
main_quit() has been called for the
innermost mainloop.