[Intel-gfx] [RFC] DRI2 swapbuffers (yes yet again)

[Kristian Høgsberg]

On Tue, May 5, 2009 at 12:20 PM, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> On Mon, 04 May 2009 19:14:29 -0700
> Ian Romanick <idr at freedesktop.org> wrote:
>
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>> Jesse Barnes wrote:
>> > On Mon, 04 May 2009 14:45:07 -0700
>> > Ian Romanick <idr at freedesktop.org> wrote:
>> >
>> >> There's a problem in dri2SwapBuffers.  If a new libGL is used with
>> >> an old driver, psc->dri2->setBuffers won't be set, right?
>> >
>> > Yes.  I should probably add an #ifdef for that like ->flush has.
>>
>> No, I mean what happens you if you build a driver from, say,
>> mesa_7_4_branch and use it with libGL that has your patches applied.
>> The compile-time check won't cut it.
>
> Oh runtime mixing too... is that common?
>
>> >> Also, should there be a mechanism for the 3D driver to force swap
>> >> buffers to be implemented with a copy?
>> >
>> > Hm, well the 2D driver can easily force it by not implementing a
>> > swapbuffers function or by returning NULL, but I guess allowing the
>> > 3D driver to force it would be ok to.  Could probably just check for
>> > ->setbuffers?  Or maybe add a way for the driver to set the
>> > swapAvailable flag...
>>
>> Having this ability would allow us to advertise some fbconfigs with
>> GLX_SWAP_METHOD_OML = GLX_SWAP_COPY_OML.  We obviously don't have any
>> apps that use that today, but I can think of a couple that should. :)
>
> Yeah, ok.

It's not something that needs to be exposed in the protocol or dri2
module.  If you want the copy behaviour, use DRI2CopyRegion().
Another point about GLX_SWAP_METHOD_OML is that we can't really
implement the "always swap" (GLX_SWAP_EXCHANGE_OML) behaviour without
a fair bit of yucky code, and without that we can't really claim to
support the extension.

cheers,
Kristian