gx_window_event_process in GUIX event handlers

Can someone please explain to me the usage of 'gx_window_event_process()' in GUIX event handlers.

In example projects, its use does not seem to follow a pattern.

Some handlers call the routine on entry to the handler, others only in certain events.

I can't find the source code for the routine (hidden for GUIX i assume), and as usual i struggle to find detailed documentation for GUIX.

Thanks

Alex