OpenEuphoria

Re: Stack limits query - windows dlls

• Posted by Derek Parnell <ddparnell at bigpond.com> Nov 26, 2002
• 413 views

I would have thought that doEvents inside the inPaint handler is a 
dangerous thing. Is it really necessary? What events are you expecting to 
happen during the onPaint processing? Anyways, I often do this sort of 
thing...

integer painting painting = False
procedure onPaint_xxx(...)
 if painting then
   return
end if
painting = True

. . .

painting = False
end procedure


On Tue, 26 Nov 2002 01:02:53 +0000, Pete Lomax <petelomax at blueyonder.co.uk>
wrote:

>
> I have recently stopped a problem which went along the following
> lines:
>
> windows (or win32lib) calls onpaint(1) -- some lengthy graphics stuff
> onpaint calls doEvents
> doEvents calls onkeydown
> onkeydown calls onpaint(2)	-- user has zoomed
> ...
> 			      onpaint(3)
> ...
> 			      onpaint(4)
> ...
>
> of course, onpaint(1)..(3) will check whether to continue and just
> return, without doing any more graphics stuff, but only after doEvents
> returns. So if the user (me) zooms and zooms and zooms, before (any
> of) the graphics drawing gets finished, the stack just grows and grows
> until it goes bang.
>
> The Euphoria interpreter does not have this problem running pure Eu
> code - I've just tested it to over 1,000,000 recursive calls and it
> just gets a bit slower, but the windows dlls I think have a much
> smaller limit, (128K?) and crash.
>
> I made onkeydown count how many outstanding calls it had made to
> onpaint and ignore any further attempts to zoom when it reached a
> certain number, until that is, they had finished & it is safe to
> resume. Stopped the problem quite definitely anyway
> (invalid page fault in module KERNEL32.DLL at 015f:bff71459)
>
> So after all that, my question is simple: what would a sensible limit
> be?
>
> Or instead, should I be detecting that onpaint is still running, so
> instead of calling it, set appropriate flags, safe in the knowledge
> that control will eventually return to the statement following the
> doEvents call, so onpaint can loop back to the start?
>
> Pete
>
> ==^^===============================================================
> This email was sent to: ddparnell at bigpond.com
>
>
>



-- 

cheers,
Derek Parnell