I have an animated-canvas class on PLaneT that does the double-buffering automatically - I'm sure there are other similar solutions out there too (e.g., I think frtime has some similar classes). Doug <div class="gmail_quote"> On Sat, Apr 11, 2009 at 1:27 PM, Robby Findler <<a href="mailto:robby@eecs.northwestern.edu">robby@eecs.northwestern.edu</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> 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 <div><div></div><div class="h5"> On Sat, Apr 11, 2009 at 2:22 PM, CHAMLY <<a href="mailto:marc.chamly@gmail.com">marc.chamly@gmail.com</a>> 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 <<a href="mailto:marc.chamly@gmail.com">marc.chamly@gmail.com</a>> 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 <<a href="mailto:marc.chamly@gmail.com">marc.chamly@gmail.com</a>> 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: >>>>> <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target="_blank">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a> >>>>> >>> >>> > > _________________________________________________ For list-related administrative tasks: <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target="_blank">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a> </div></div></blockquote></div>