Re: [HOpenGL] Black Screen with GHC&HOpenGL

7 Feb 2010


      I've played a bit around and tried to use DoubleBuffered display mode 
instead of single and everything works fine (as I read using 
DoubleBuffered is important to avoid animation flicker, so I would have 
to use it anyway) . Thanks for helping, know I can start using OpenGL 
with Haskell, I hope there won't be any big problems in the future.

If anybody has the same problems, here's my Main.hs:
http://hpaste.org/fastcgi/hpaste.fcgi/view?id=17220

Daniel

Balazs Komuves schrieb:
...
Hi Daniel,
Your program works fine here (OSX + GHC 6.10.1), so I can only guess:
 - you either have some installation program (are you on a 64 bit 
system by any chance?)
 - or the GLUT implementation is a bit different, and needs some more 
initialization.
In particular, I would try setting `initialDisplayMode' before calling 
`createWindow', eg.
initialDisplayMode $= [ RGBAMode ]
and possibly also `initialWindowSize'.
Also, there is no clean way to exit the program; you should set up a 
keyboard handler
and exit on pressing ESC or something like that, but this is not 
really important.
Balazs
On Sun, Feb 7, 2010 at 2:06 AM, Daniel mailto:cornicis@googlemail.com> wrote:
Hello!
    So, my problem is this: I can compile my "Main.hs" without errors,
    but when I'm executing the application a black screen appears and
    my cursour is still visible. After klicking somewhere on the
    screen my normal Desktop reappears with "Hello World" in my task
    bar. I can minimize all other windows to have only "Hello World"
    visible, but the black screen appears again when I'm trying to
    activate the window. Do you know what I am doing wrong?
Ubuntu is my OS, all libraries are installed, I have the same
    problem using Hugs.
Here's my Main.hs:
import Graphics.UI.GLUT
    import Graphics.Rendering.OpenGL
main = do
     (progname, _) <- getArgsAndInitialize
     createWindow "Hello World"
     displayCallback $= display
     reshapeCallback $= Just reshape
     mainLoop
reshape s@(Size w h) = do
     viewport $= (Position 0 0, s)
     postRedisplay Nothing
myPoints :: [(GLfloat, GLfloat, GLfloat)]
    myPoints = map (\k -> (sin(2*pi*k/12),cos(2*pi*k/12),0.0)) [1..12]
display = do
      clear [ColorBuffer]
      renderPrimitive Points $ mapM_ (\(x,y,z) -> vertex$Vertex3 x y
    z) myPoints
      flush
Thanks for helping! :)
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