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

Nevertheless, double buffering means that you have to have the entire
thing in a single buffer. Otherwise you'll draw the tunnel with no
copter and then draw the copter on top, which leads to flicker.

I don't know what the rest of your code does, but perhaps you don't
really need those two bitmaps at all.

But if you do, then you'll need a third bitmap.

Robby

On Sat, Apr 11, 2009 at 2:22 PM, CHAMLY <marc.chamly at gmail.com> wrote:
> Yes, But I have 2 bitmaps, because both of my objects have to move
> independently, the tunnel has to be able to move to the left, without moving
> the Copter, and the Copter has to move Up and Down without moving the
> tunnel...
>
> Marc
>
>
>
> On Apr 11, 2009, at 8:47 PM, Robby Findler wrote:
>
>> Oh! I misread the code. You need to create a single bitmap containing
>> the whole thing and then draw it. Don't draw two bitmaps (that's
>> what's causing your flicker).
>>
>> Robby
>>
>> On Sat, Apr 11, 2009 at 12:59 PM, CHAMLY <marc.chamly at gmail.com> wrote:
>>>
>>> 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
>>>>>          _________________________________________________
>>>>>  For list-related administrative tasks:
>>>>>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>>>>
>>>
>>>
>
>