[Mesa-dev] [PATCH 08/10] drirc: Don't expose 10 bpc visuals/configs to gnome-shell.

[Mario Kleiner]

On 09/08/2017 05:21 AM, Michel Dänzer wrote:
> On 08/09/17 12:26 AM, Marek Olšák wrote:
>> [+ Dave]
>>
>> We can also ignore gnome-shell in Mesa for now and let the gnome-shell
>> maintainers fix the issue in gnome-shell.
> 
> Indeed, that would be better.
> 

[+ Jonas Adahl] probably a good person to ping wrt. this?

You mean we shouldn't provide the driconf workaround for gnome-shell?

That would make g-s wayland pretty much unusable in a very colorful way 
until it's fixed. On X11 g-s works perfectly fine at Screen DefaultDepth 
24, but on wayland we'd probably get lots bug reports by users which try 
out the latest Mesa from some repo, e.g., Ubuntu's padoka ppa's.

> IIUC, with this workaround, all content composited by gnome-shell will
> effectively use only 8 bits per component, even when Xorg runs at depth 30.
> 
> 

Yes, just confirmed with photometer. However, unredirected fullscreen 
windows (page-flipped) still work with 30 bit precision says the 
photometer, so there's still some use on g-s x11.

Tapani is right, the clutter picking code uses color coded drawing into 
some fb, translating ui element ("actor") id's to rgb color codes and 
back during hit testing / picking. That code has some clever logic to 
deal with fb's of different bit depths, but was last updated 9 years ago 
to deal with problems in low precision modes (rgb565 i guess), so 
probably never tested on any depth 30 fb's and only handling < 8 bpc, 
not more.

The stuff is in clutter/clutter-main.c, (_clutter_id_to_color() and 
_clutter_pixel_to_id()) but apparently there are separate clutter trees 
for the mutter and clutter repos, ie. mutter includes its own copy of 
clutter.

-mario