busy progress bar without thread ?

[npc]

Hi,

I am using progress bar which showing a busy mode ( minimum = maximum = 0 ).
and my code goes like this..

progressBar.setMinimum(0);
progressBar.setMaximum(0);
fn();
progressBar.hide();

progressBar.setMinimum(0);
progressBar.setMaximum(0);
fn();
progressBar.hide();

To copy to clipboard, switch view to plain text mode 

When the process running in fn() the progress bar is not showing the busy mode.

But I want to show the progressbar in a busy mode till the fn retuns.
should I use threads for this ? or is there any easy way ?

Thanks
*npc*