[Haskell-cafe] unsafeInterleaveIO and OpenGL

[Henning Thielemann]

On Fri, 9 May 2008, Peter Verswyvelen wrote:

> I'm experiencing strange behavior when executing some Haskell OpenGL code 
> inside unsafeInterleaveIO.
>
> For example,
>
>       vp <- get GL.viewport
>
> returns garbage, as if the opengl context is not correctly set.

Sounds reasonable. 'unsafeInterleaveIO' defers computation of 'vp' until 
it is actually needed. At this time the viewport might have changed.