[HOpenGL] problem with displayCallback and Double buffering

[Marc A. Ziegert]

wow. thanks.
i think, i have to compile again...
and read about all the configurations first.

- marc


Am Mittwoch, 5. November 2003 01:04 schrieb Wolfgang Thaller:
> 
> On 05.11.2003, at 00:34, Marc A. Ziegert wrote:
> 
> > i've installed ghc-6.3.20031102 (still the "-lGL" <--> "-lGLU" bug in 
> > package.conf).
> > that version works now, thanks.
> >
> > now i want to use ghci, especially with
> > forkIO mainLoop
> > , but that does not seem to work anymore. is that a forkIO bug?
> 
> Hmm... did you build ghc with the --enable-threaded-rts flag? If so, 
> you should be using forkOS instead of forkIO; forkIO creates a 
> lightweight thread, but most OpenGL implementations require a 
> (heavyweight) OS thread to run reliably. With GHC 6.3 
> --enable-threaded-rts, this means you can call GLUT/OpenGL from the 
> main thread, from threads created using forkOS, and from foreign 
> exported functions, but not from threads created using forkIO.
> 
> If you're not using --enable-threaded-rts, then you could encounter a 
> different problem: GHCi only gets a chance to run while the GLUT 
> mainLoop is inside a callback, and while GHCi is waiting for input 
> using readline, the GLUT mainLoop will be blocked. Things might work if 
> you build GHC without readline support and install an idle callback 
> into the GLUT event loop.
> 
> In both cases, keep in mind that all the OpenGL drawing has to be done 
> from the thread that GLUT is running in. You can use MVars to 
> communicate with that thread from the GHCi prompt, but doing OpenGL 
> drawing from the GHCi prompt while a GLUT mainLoop is running in the 
> background will never work reliably.
> 
> Grüße,
> 
> Wolfgang
> 
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