[plt-scheme] Double buffer (scheme/gui)

From: CHAMLY (marc.chamly at gmail.com)
Date: Sat Apr 11 13:59:24 EDT 2009

Well I already put the 'no-autoclear  to the canvas, my BITMAP-DC-1  
(tunnel) doesn't flicker only my BITMAP-DC-2(Object) flickers, I will  
try to put the 'no-autoclear somewhere else, and see if it works.

Thank you.

On Apr 11, 2009, at 7:31 PM, Robby Findler wrote:

> Probably you want to pass the 'no-autoclear style to the canvas%
> object when you create it (I may have got the precise name wrong, but
> it is listed in the docs for the initialization arguments to canvas%).
> But you also probably want to only recreate the bitmaps when their
> content changes, not every time the window is refreshed. In other
> words, all but the last line below should be somewhere else, not in
> the on-paint method.
> Robby
> On Sat, Apr 11, 2009 at 12:25 PM, CHAMLY <marc.chamly at gmail.com>  
> wrote:
>> HI!
>> I am programming a game on scheme using #lang scheme/gui, the game  
>> is  made
>> of:
>> 1) an object (copter) that when you click moves up, otherwise it  
>> falls down,
>> and does not move horizontaly.
>> 2) a tunnel that moves from right to left, giving the impression  
>> that the
>> object is moving forward (moving to the right reaching the end of the
>> tunnel).
>> I have a little problem with my double buffer,
>> I'm using two bitmaps one to draw the copter, and one to draw my  
>> tunnel
>> Here is what i have in the paint-callback of my canvas:
>>             (send BITMAP-DC-1 clear)              ; i move my tunnel
>>             (send TUNNEL draw-tunnel1  BITMAP-DC-1  y1)
>>             (send dc draw-bitmap BITMAP-1  (- x-canvas) 0 'solid))
>>             (send BITMAP-DC-2 clear)     ; i move my copter
>>             (send BITMAP-DC-2 draw-bitmap copterUp  0 0 'solid)
>>             (send dc draw-bitmap BITMAP-2  150 (send COPTER get-y- 
>> copter)
>>  'solid))
>> The problem is that my copter still flickers, and i don't know why??
>> (i don't draw my copter in BITMAP-DC-1 because afterwords i also  
>> use other
>> bitmaps to draw my tunnel)
>> thanks
>> Marc
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