OK, it actually DOES appear related to the -threaded flag. I was sure I had removed that and still seen the problem but now it seems that taking that out is indeed the fix. Using the -O2 flag is OK. I guess it's some syncronization problem when using the threaded RTS. Which is a shame because it does seem faster that way on my dual core machine. I guess I need to learn about how threading works in ghc.
Duncan Coutts
I'm using the Gtk.timeoutAddFull function to do the animation.
Are you using the threaded rts? Are you linking the program with -threaded? Are you doing the drawing directly in the timeout function or just invalidating the window/widget and letting it get redrawn? See for example the cairo clock demo which animates the hands of the clock every second: timeoutAdd (widgetQueueDraw window >> return True) 1000 In general it is much better to only ever draw to a window or widget during that widget's expose event. Duncan --------------------------------- Get easy, one-click access to your favorites. Make Yahoo! your homepage.