Dri2 buffer format

[Russell Shaw]

On 10/11/10 12:32, Jesse Barnes wrote:
> On Wed, 10 Nov 2010 12:30:11 +1100
> Russell Shaw<rjshaw at netspace.net.au>  wrote:
>
>> On 10/11/10 09:28, Jerome Glisse wrote:
>>> On Mon, Nov 8, 2010 at 6:55 PM, Russell Shaw<rjshaw at netspace.net.au>   wrote:
>>>> On 09/11/10 04:53, Jerome Glisse wrote:
>>>>>
>>>>> On Mon, Nov 8, 2010 at 10:52 AM, Russell Shaw<rjshaw at netspace.net.au>
>>>>>    wrote:
>>>>>>
>>>>>> Hi,
>>>>>> How should the "format" of a DRI2 buffer be determined?
>>>>>>
>>>>>>
>>>>>> http://www.x.org/releases/current/doc/dri2proto/dri2proto.txt
>>>>>>
>>>>>> DRI2ATTACH_FORMAT { attachment: CARD32
>>>>>>              format:     CARD32 }
>>>>>>
>>>>>>      The DRI2ATTACH_FORMAT describes an attachment and the associated
>>>>>>      format.  'attachment' describes the attachment point for the buffer,
>>>>>>      'format' describes an opaque, device-dependent format for the buffer.
>>>>>>
>>>>>>
>>>>>
>>>>> As the spec says, it's opaque and only the driver understand it, intel,
>>>>> radeon, nouveau all use different things i think. DRI2 is meant to be
>>>>> use btw different driver of same hw which should all understand each
>>>>> others.
>>>>
>>>> If it's opaque, how does one know what bytes are red/green/blue so that
>>>> you can draw a line in the right colour?
>>>
>>> This format is intend to be exchanged btw Xorg DDX driver for a given
>>> hw for instance the nouveau ddx and with the mesa or other dri2 driver
>>> like for instance the nouveau gallium driver. Both of this component
>>> understand each others.
>>>
>>> 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)