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

Michel Dänzer michel at daenzer.net
Fri Feb 14 15:55:28 UTC 2020

On 2020-02-14 12:53 p.m., 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.
> 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
> virtual X server (tried using Xephyr but it complained about there being
> no matching screen), or some other way I haven't thought of?

I reckon it should be relatively easy to make this work with Xwayland.

Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer

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