[linux-audio-dev] FLTK/X11 question

Sorry, this is not directly audio related. I'm hacking together a VU meter app for jack, using FLTK, and it works OK, except that when the update rate falls out of sync with the video refresh rate the window flickers. I'm pasting a bigass image as the background, see screenshot http://inanna.ecs.soton.ac.uk/~swh/vu-ss.png (apologies for the tacky brushed steel background, its a placholder, honest). I seem to remeber that on the Amiga and in GL I could issue a call to wait for the next vertical blank, forcing the redraw to be in sync with the video hardware. Is there an equivalent in FLTK or X? How do other people get round this? Cheers, Steve PS I know a VU meter in a PCM system is about as much use as an underwater hairdryer, but its a stepping stone to a PPM meter, and you can run it in peak mode, but with a VU scale and balistics.