HOpenGL uses Data.StateVar. One can define the following function:

newStateVar :: a -> IO (StateVar a)
newStateVar val = do
    ref <- newIORef val
    let readAction = readIORef ref
    let writeAction = \newVal -> writeIORef ref newVal
    return (makeStateVar readAction writeAction)

Now one can use StateVar consistent with HOpenGL:

create:  foo <- newStateVar bar
read:     get foo
write      foo $= baz

On 4 April 2010 11:03, Mark Spezzano <mark.spezzano@chariot.net.au> wrote:

Hi

What is the correct way to record "custom" state when using OpenGL?

By this, I refer to, say, properties of a square--say it's x,y coordinates as it moves across the screen. This requires that the program keep track of the object's state as it moves. These coordinates are _not_ part of the OpenGL state machine, so is the correct way to use the State monad?

If so--or if not so--how would I proceed to keep track of the state of my objects as they move about the screen? Maybe the HOpenGL implementation comes with such state-tracking devices?

Please post code snippets if necessary.

Thanks in advance,

Mark Spezzano
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