[Fieldtrip] Re: [HOpenGL] noticing freeglut vs not

Thanks very much Claus. Sound fixable indeed, with an exception handler. Would someone with convenient access to a non-freeglut system be up for trying out Claus's suggestion??? - Conal On Thu, Dec 4, 2008 at 9:52 AM, Claus Reinke wrote:

Is this still an open issue in FieldTrip? If you look at the online versions of the files Sven mentioned

http://darcs.haskell.org/packages/GLUT/include/HsGLUTExt.h http://darcs.haskell.org/packages/GLUT/Graphics/UI/GLUT/Extensions.hs

you can see how the dynamic lookup of functions that are only available in some extensions is handled. Looking at

http://darcs.haskell.org/packages/GLUT/Graphics/UI/GLUT/Begin.hs

it does seem as if constants and StateVars are not directly protected like this, but 'actionOnWindowClose' calls 'glutSetOption', which you can see in http://darcs.haskell.org/packages/GLUT/Graphics/UI/GLUT/QueryUtils.hs

as just such a dynamic lookup. In case this isn't clear: your code can simply catch the exception thrown when that dynamic lookup fails, letting the exception handler pursue an alternative path (since your ticket recommends commenting out that line, the handler could perhaps just do nothing in your case, or issue a warning about missing freeglut?).

No change to the GLUT package should be needed, I think. Claus

Thanks for the pointers.

...

I'm looking for some way to program my library so that a graceful exit is made where possible and still runs, though exits less gracefully with non-free glut. I'd be happy with either a new API entry for that case or a change to the meaning of MainLoopReturns.

- Conal

On Thu, Nov 20, 2008 at 5:33 AM, Sven Panne wrote:

On Thursday 13 November 2008 03:24:29 Conal Elliott wrote:

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I'm looking for a way to use MainLoopReturns when freeglut is present and not when it isn't. I could use some help. I figure that the implementation has some way to generate that error message, and maybe we could similarly just do a standard ungraceful exit if freeglut is missing.

The great thing about MainLoopReturns is that it plays nicely with ghci. Closing a window returns to ghci for more fun.

Some more info at http://trac.haskell.org/FieldTrip/ticket/8 .

Any ideas?

Currently the GLUT binding uses dynamic lookup to get freeglut-only API entries (see /GLUT/Graphics/UI/GLUT/Extensions.hs, cbits/HsGLUT.c, include/HsGLUTExt.h) and uses throwIfNull to test for non-existent API entries. Therefore, e.g. actionOnWindowClose should throw an exception when "classic" GLUT is used. I am not sure if I understand your request: Do you want a new API entry for the GLUT binding or a different behavior of the current entries?

Cheers, S.

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