bernd kreimeier wrote:
>
> > >
> > > // Scenario for an entry point in libGL.so
> > > glFoo() // app makes call
> > > -> calls libGL.so:glFoo
v> >
> > So, given what I've proposed above, this would call "__glFoo_driver_MODE()"
> > directly, rather that indirectly through the "__glFoo_driver_dispatch"
> > function.
>
> Maybe I misunderstand. It seems that you propose collapsing the
> context and the driver dispatch into one. I can see only
> two ways to make this work.
>
> a) libGL.so:glFoo does
> if ( currentContext!=lastContext )
> _glFoo_driverMODE = whatever
> which adds overhead to every single call
>
> b) glxMakeCurrent manipulates libGL.so
>
> I think the latter would do what you want (just as the
> application is best advised to update pointes on
> context switch, GLX could do so). One drawback it has
> is that it will always update all internal dispatch,
> as it does not know what the application might use.
> But context switch is expensive, so this might be
> acceptable. One issue I have no idea about is whether
> this kind of interaction between GLX and GL is desirable.
>
> Anyway, your should amend your proposal by stating how you
> want to collapse the two indirections into one, and when.
Sorry, I tried to make this clear, but apparently didn't.
Jon's example of a libGL dispatch entrypoint contains this:
-> (*dispatch[context].glFoo)() // jump table based on context
-> calls libDriver.so:__glFoo_driver_dispatch
My proposal would change it to this:
-> (*dispatch[context].glFoo)() // dynamic jump table based both
// on context and driver state.
-> calls libDriver.so:__glFoo_driver_MODE
This is accomplished by allowing the driver to manipulate the
contents of the context's jump table (through an appropriate and
well defined API of course). The libDriver.so:__glFoo_driver_dispatch
function is redundant, and doesn't need to even exist!
I hope this makes the concept clearer.
Cheers!
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