Dri2 buffer format

[Jerome Glisse]

On Tue, Nov 9, 2010 at 9:11 PM, Russell Shaw <rjshaw at netspace.net.au> wrote:
> On 10/11/10 12:47, Kristian Høgsberg wrote:
>>
>> On Tue, Nov 9, 2010 at 8:43 PM, Russell Shaw<rjshaw at netspace.net.au>
>>  wrote:
>>>
>>> On 10/11/10 12:32, Jesse Barnes wrote:
>
> ...
>
>>>>>> DRI2 is not mean to be use by end user application, it's only use by
>>>>>> Xorg to comunicate with library such as opengl that want to provide
>>>>>> direct rendering to X pixmap/window.
>>>>>
>>>>> Ok. How do i plot a pixel in Wayland? I'm not using
>>>>> gtk/qt/OpenGL/OpenVG
>>>>> etc.
>>>>
>>>> Allocate an shm buffer based on an mmap you've done in your client.
>>>> Then you can draw to it and notify wayland of the damage.
>>>
>>> Ok. I'm already using shm buffers in X. Is there example code in wayland
>>> of getting the shm pixel format? (i couldn't see one last time i looked)
>>
>> Look at the smoke.c example.
>
> Hi,
> smoke.c uses cairo http://cairographics.org/
> I don't want cairo.
>
> Please could i have that one bit of code for the pixel format?:)

Wayland is not intended to work that way, GPU might pack pixel in strange
format (especialy newer GPU where sometimes you can only use tiled
buffer). The format of the buffer that GPU can understand would thus vary
from one GPU to another, making any application which try to directly
access pixel non portable at all.

The format of the underlying buffer should thus only be understable
by the associated GPU driver (wayland use EGL driver and in your
app you can use another api as long as it has a driver for the GPU
but i could only encourage anyone to stick to api such as EGL or
cairo GL as this have proper driver for all 3 big GPU amd,intel &nividia)

Cheers,
Jerome