Re: C++ Draw Callback?

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Christopher R Volpe (volpe++at++ash.crd.ge.com)
Fri, 06 Dec 1996 16:59:37 -0500

Hansong Zhang wrote:
>
>
> The same thing can be done to non-static member functions, also.
> But you need a explicit type conversion:
>
> chan->setTravFunc( PFTRAV_DRAW, (pfChanFuncType)MyClass::DrawChannel );
>
> You'll still get an warning about this conversion, but you could
> ignore that...

No you can't. Non-static member functions have a "this" pointer passed
in behind the scenes as part of the calling convention. If you try to
invoke the member function as if it were an ordinary function, it will
crash immediately if you're lucky, and deceptively appear to work, for
now, if you're unlucky. What will likely happen is that your member
function will think that the pfChannel* parameter passed in by performer
is actually the this-pointer, and will think that the void* parameter
passed in is atually the pfChannel* parameter, leaving the void*
parameter undefined within the member function, and it all goes downhill
from there...

--


Chris Volpe			Phone: (518) 387-7766 
GE Corporate R&D		Fax:   (518) 387-6560
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