using fltk with gl animation windows

I have a fltk window with a interior window which subclasses the Fl_Gl_Window to allow me to show Gl stuff in the window. This is all fine except for the updating of the window. The contents are a simple simulation showing movement, however the refreshing of this screen only seems to occur with a window event, eg mouse movement, click etc
How can i set it up so it will automatically refresh, is there something similar to the glutIdleFunc callback? or anyother method of regularly updateing this window?


Fl::add_idle(void (cb)(void), void* = 0);