[HOpenGL] Conversion of GLsizei to GLfloat

[Achim Krause]

Hello everyone,
I'm making my first experiences with OpenGL at the moment. It's really
nice to use, but I got one issue which really freaks me out:
Let's say I want to create a square-grid across the whole screen as
background of a very basic 2D game. The application is meant to run in
full screen mode. Since I want it to work on different resolutions and
screen formats I introduced an IORef relSize (of type (GLfloat,GLfloat))
which is meant to store the size of the squares relative to the current
window size, and tried to set a reshape callback in the form of
reshape relS s@(Size w h) = do
   viewport $= (Position 0 0, s)
   relS $= (size / w, size / h)
where size is just a name for the (at another place) defined absolute
size for the squares. The Problem is that i see absolutely no way to
convert w and h (which are of type GLsizei) in order to yield a value of
type GLfloat. Is there any way to extract a Haskell Integer value from
values of type GLsizei and convert a Haskell Float value to a GLfloat?
Or is there a more direct way to do what I'm trying to achieve?
The only solution i've come up with so far is using read.show as
converter, which cannot really be the intended way of doing this.
Thank you very much!
Sincerely, Achim Krause