I am using that all the time while editing, but its only almost-realtime by pressing Alt-A (Windows only, just saw that in Linux that did not work).
This shortcut key actually formats your whole code in the current window, i.e. the whole file according to what style you have selected. It works quite well once I got used to pressing Alt-A all the time (a bit like pressing Ctrl-S all the time)
For exampe
if(i==1) a=1;
else a=2;
looks like that after pressing Alt-A
if (i==1)
{ a=1; }
else
{ a=2; }
With your GNU style it would be a bit different.
Not sure if that answers the question, though