[HOpenGL] problem with displayCallback and Double buffering

[Sven Panne]

Marc A. Ziegert wrote:
 > does anyone else have this problem?  i want to use double buffering,
 > but swapBuffers does not seem to work.

Works for me with the current version from CVS on x86 Linux, see below.

 > to set the active window to... the active window (i think that has
 > to work!) does not work, too. [...]

I guess with "active" you mean "current", but this works for me, too.
Remember that you can't access currentWindow (or windowPosition,
windowSize, etc.) before mainLoop is entered, this is how GLUT works.

Cheers,
    S.

----------------------------------------------------------------------
import Graphics.UI.GLUT

dc :: DisplayCallback
dc = do
    clearColor $= Color4 0 0 1 0
    clear [ColorBuffer, DepthBuffer]
    putStrLn "begin swapBuffers"
    swapBuffers
    putStrLn "end swapBuffers"

main :: IO ()
main = do
    getArgsAndInitialize
    initialDisplayMode $= [DoubleBuffered, WithDepthBuffer]
    b <- get displayModePossible
    putStrLn $ "displayModePossible? ..." ++ show b
    createWindow "main"
    displayCallback $= dc
    mainLoop
----------------------------------------------------------------------
panne at jeanluc:~> ghc --make first.hs
Chasing modules from: first.hs
Compiling Main             ( first.hs, first.o )
Linking ...
panne at jeanluc:~> ./a.out
displayModePossible? ...True
begin swapBuffers
end swapBuffers
[ blue window appears, iconized it and de-iconized it again ]
begin swapBuffers
end swapBuffers