[Mesa-dev] [PATCH] egl/x11/dri3: do not expose the preserved swap behavior (to be squashed)

[Eric Anholt]

Martin Graesslin <mgraesslin at kde.org> writes:

> On Thursday, November 19, 2015 1:54:22 PM CET Martin Peres wrote:
>> On 11/11/15 00:44, Eric Anholt wrote:
>> > Martin Peres <martin.peres at linux.intel.com> writes:
>> >> The preserved swap behavior is currently untested in piglit and not
>> >> supported on the GLX side. Before working on implementing it for
>> >> EGL/DRI3, let's disable it until support comes.
>> >> 
>> >> This patch is trivial enough and will likely be squashed in the commit
>> >> egl/x11: Implement dri3 support with loader's dri3 helper
>> >> 
>> >> Signed-off-by: Martin Peres <martin.peres at linux.intel.com>
>> > 
>> > This looks good to me.  I don't think anybody really cares about
>> > SWAP_BEHAVIOR_PRESERVED -- the buffer_age stuff was what you really
>> > wanted all along.
>> 
>> Hey Eric and Martin,
>> 
>> It seems like KWin is relying on SWAP_BEHAVIOR_PRESERVED for its EGL
>> backend. Should we add proper support for it in mesa or should we
>> propose a patch for kwin to test for the extension to be present before
>> using it?
>> 
>> Martin, what is your opinion on this since buffer age is what you need
>> and you already have support for it for the glx and wayland backends?
>
> That's certainly a left over from before buffer age.  I don't know whether we 
> can remove it unconditionally. Not every GLES harware which does support X11 
> supports buffer age.
>
> I assume the smartest thing to do is not ask for PRESERVED if buffer age is 
> supported.

Yeah, you definitely want to not ask for PRESERVED if you can handle
buffer age, since PRESERVED means losing page flipping.  (Part of why
PRESERVED was a bad idea from day 1)
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