[racket-dev] Universe double buffering

What happens if you restart drracket and try the same program again?
(If the double buffering appears to come back I think I know what
happened.)

Robby

On Thu, Sep 2, 2010 at 8:15 AM, Nadeem Abdul Hamid <nadeem at acm.org> wrote:
>> Why do you think it doesn't?
>
> (I'm assuming you mean: "What makes me think that it is not
> double-buffering?") ...
>
> I have a list of 15 thumbnail images of people and a function that
> places pairs of them side by side, using above/beside to create a 133
> x 581 image. i.e.
>   choose-and-show-pairs : (listof image) -> image
>
> Now, when I do:
> (big-bang PIC-LIST
>          (on-draw choose-and-show-pairs))
>
> I see each individual image getting laid out, one by one, rather
> excrutiatingly slowly. The choose-and-show-pairs actually randomizes
> the pairing up, and so if I move the mouse over the canvas, apparently
> the redraw handler is called, so I see a new set of pairs getting laid
> out, very slowly.
>
> I would have expected a double-buffered implementation to lay out the
> images in memory on some bitmap buffer and then quickly transfer the
> bitmap buffer to the canvas, so you don't actually witness the effect
> of all the above/beside operations happening.
>
>
>>
>>
>>
>>
>> On Sep 2, 2010, at 8:52 AM, Nadeem Abdul Hamid wrote:
>>
>>> Why doesn't 2htdp/universe use double-buffering?
>>>
>>> --- nadeem
>>> _________________________________________________
>>>  For list-related administrative tasks:
>>>  http://lists.racket-lang.org/listinfo/dev
>>
>>
>
>
>
> --
> Nadeem Abdul Hamid
> Associate Professor, Computer Science
> Berry College
> PO Box 5014
> 2277 Martha Berry Hwy NW
> Mount Berry, GA 30149-5014
> (706) 368-5632
> http://cs.berry.edu/~nhamid/
> _________________________________________________
>  For list-related administrative tasks:
>  http://lists.racket-lang.org/listinfo/dev
>