[PATCH dri3proto v2] Add modifier/multi-plane requests, bump to v1.1

[Daniel Stone]

Hi,

On 28 July 2017 at 09:54, Michel Dänzer <michel at daenzer.net> wrote:
> On 28/07/17 05:03 PM, Daniel Stone wrote:
>> By implementation if not spec, DRI3 v1.0 enforces that depth 16 is
>> RGB565, depth 24 is XRGB8888, and depth 32 is ARGB8888.
>
> No, it doesn't. How the bits stored in a pixmap are interpreted is
> outside of the scope of DRI3 1.0.

I mean that, when using glamor_egl and Mesa, PixmapFromBuffer
translates XRGB8888 to depth 24, and BufferFromPixmap translates depth
24 to XRGB8888. So, de facto, these are the established translations
between depth and format required to use DRI3.

>> tl;dr: we could replace FourCC with depth as the format determinant to
>> better match DRI3 v1.0, or just declare that doing anything with those
>> Pixmaps other than displaying them to a Window with a compatible
>> Visual results in undefined behaviour
>
> I'm getting less and less convinced that any reference at all to formats
> in the context of pixmaps in the DRI3 specification is a good idea.

I'd be fine with that, but at least documenting the implemented
behaviour would probably be reasonable, to save other implementations
from having to reverse-engineer the actual semantics.

Cheers,
Daniel