[Haskell-beginners] gtk2hs and threadDelay

[gabre at caesar.elte.hu]

Hello!

I managed to do it with timeoutAdd:

--code below is the onClicked function:
drawProgram gui preprocPrg = do
	let drArea = (drawWin gui)
	drw <- widgetGetDrawWindow drArea
	-- let list = compileToList preprocPrg
	-- renderWithDrawable drw (drawFromList list)
	renderWithDrawable drw (myDraw 200 200)
	-- drawWindowProcessUpdates drw True
	timeoutAdd ((\_ -> do
			renderWithDrawable drw (myDraw2 200 200)
	                return False) 5) 500
	return ()

But "sometimes" it gives the following error:

(<interactive>:23929): Gdk-WARNING **: Using Cairo rendering requires  
the drawable argument to
have a specified colormap. All windows have a colormap,
however, pixmaps only have colormap by default if they
were created with a non-NULL window argument. Otherwise
a colormap must be set on them with gdk_drawable_set_colormap

(<interactive>:23929): Gdk-CRITICAL **: IA__gdk_cairo_region:  
assertion `region != NULL' failed
<interactive>: user error (NULL pointer)
<interactive>: interrupted
<interactive>: warning: too many hs_exit()s

What can cause this? I think the other parts of my program are  
correct, and I cant understand, how can ghci "randomly give" this  
error. (every 5. try)

To be honest, my goal is to make a "turtle graphics" program, so I ll  
have to write a function, which draws a line on the GUI in slow  
motion: there will be even more problems with timing, because I ll  
have to draw the line pixel by pixel.