30-bit X session and programs requiring 24-bit depth

[Ilya Anfimov]

On Fri, Feb 14, 2020 at 12:53:53PM +0100, Marek Szuba wrote:
> Hello,
> 
> I do quite a lot of photo editing on my box and with both my monitors
> and my graphics card (amdgpu) supporting 10-bit colour channels, I tend
> to run X at colour depth 30. Unfortunately some software, most notably
> programs using OpenGL it seems, refuse to run in this mode - presumably
> (I have seen this mentioned as the reason of problems with 30-bit mode
> under Windows when the first cards supporting it came out) because the
> software assumes 8-bit alpha channel but with the frame buffer still
> being only 32-bit it is only 2-bit. Seeing as there seem to be no way of
> switching colour depth on the fly, the best I have been able to come up
> with is two separate X sessions - one at depth 30 and one at 24.

 Well,  you  can  try to run it via virtualgl -- however, I'm not
sure it will be easy to share one videocard  between  two  server
simultaneously  -- i.e., make that no one of them will be sent to
background.

> 
> Is there, or perhaps will there be some way in the near future, to work
> around this problem - either by increasing framebuffer BPP (tried it a
> while ago but it didn't seem to accept anything more than 32), using a

 I'm not sure it is really a framebuffer size problem.

 Shouldn't  alpha  be  stripped  off when copying data to DAC-ac-
cessed areas anyway?
 Also, There was 16-bit  framebuffers,  no  problems  with  alpha
there  -- when all the framebuffer bits was filled with color in-
formation.

 Can you post glxinfo ?

 Also, it would be useful to debug opengl calls of failed apps --
but there are different available techniques for different opengl
drivers.


> virtual X server (tried using Xephyr but it complained about there being
> no matching screen), or some other way I haven't thought of?
> 
> Thank you in advance for your comments.
> 
> -- 
> MS
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