[HOpenGL] Re: Open GL, GLUT

[Sven Panne]

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Gracjan Polak wrote:
> 
> Hi all,
> 
> I'd like to make some use of OpenGL with Haskell (under Win2000).
> Here is some code:
> 
> 
> module Main where
> import Graphics.Rendering.OpenGL.GL
> import Graphics.Rendering.OpenGL.GLU
> import Graphics.UI.GLUT
> 
> main = do
>     ver <- get gluVersion
>     putStrLn ver
> 
>     getArgsAndInitialize
>     fullScreen
>     wnd <- createWindow "Hello World"
> 
>     vertex (Vertex2 (100::GLint) 100)
>     return ()
> 
> Compilation (linking) fails with:
> 
> $ ghc --make openglapp.hs -o openglapp.exe
> Chasing modules from: openglapp.hs
> Compiling Main             ( openglapp.hs, openglapp.o )
> Linking ...
> c:/ghc/ghc-6.2/libHSGLUT.a(Initialization__158.o)(.text+0x123):ghc16024.hc: 
> unde
> fined reference to `glutInit at 8'
> c:/ghc/ghc-6.2/libHSGLUT.a(Window__61.o)(.text+0x33):ghc14736.hc: 
> undefined refe
> rence to `glutFullScreen at 0'
> c:/ghc/ghc-6.2/libHSGLUT.a(Window__53.o)(.text+0x85):ghc14736.hc: 
> undefined refe
> rence to `glutCreateWindow at 4'
> 
> Manually adding -lglut -lglut32 does not help. Libraries libglut32.a and 
> libglut.a are there, they contain needed symbols but with '_' prepended, 
> like _glutInit at 8.
> 
> Functions from GL and GLU link perfectly. They do even work correctly 
> when run. Only GLUT ones do not :(
> 
> Has anybody compiled anything for GL recently? Google pointed me only to 
> some old, not relevant any more, material.
> 
> Am I missing something obvious here?
> 
> GHC 6.2, installer for Window taken from www.haskell.org, Win2000 
> Professional.

It compiles fine with GHC 6.2.1 on my Win2k box, you might want to update your
GHC installation. There have been quite a few bug fixes, so it might be worth it
even when you are not using OpenGL/GLUT. Does it work with 6.2 when you add -O?
Just curious...

Apart from that, there are a few things you should change in your code:

    * GL/GLU state can only be accessed after you have a rendering context, i.e.
      after createWindow

    * fullScreen only works when you have a current window, i.e. after createWindow

    * Rendering should only be done in the display callback

    * The vertex call should probably be within a renderPrimitive.

Perhaps Sven Panitz' tutorial might help a bit:

    http://www.tfh-berlin.de/~panitz/hopengl/

A more up-to-date version of the tutorial is available from the fptools CVS repository,
but building it requires some unusual tools, BTW.

Cheers,
    S.