[plt-scheme] double on-paint

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Thu Dec 7 17:48:54 EST 2006

At Thu, 7 Dec 2006 16:31:00 -0600, "pedro pinto" wrote:
> On Windows XP, with DrScheme v360, the following code:
> (define f (new frame% (label "Hello")))
> (define c (new canvas% (parent f)
>                (paint-callback (lambda _ (printf "painting~n")))))
> (send f show #t)
> Will print "painting" twice, with a noticeable delay between the two
> messages, every time the frame is resized. That's not right is it?

My guess is that both resize and refresh events from from the OS, and
MrEd at some point triggers a refresh to handle the resize event. I may
be able to improve that.

Is the delay you see just a delay in DrScheme's output? I see a
significant delay, too, but when I include the result of
`(current-milliseconds)' in the printed message, then the printed
numbers usually differ by only 20 or 30 milliseconds.


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