Bug#998378: Second monitor has correct mouse cursor and white+garbage

[Simon McVittie]

Control: tags -1 + moreinfo

On Wed, 03 Nov 2021 at 09:55:20 +0100, Julien Puydt wrote:
> Where should I have a look to find error messages and fix the issue?

If in doubt, the answer is always the systemd journal (system log).

> (1) The main "card" is Intel Corporation CoffeeLake-H GT2 [UHD Graphics
> 630], with kernel module i915. The second "card" is NVIDIA Corporation
> GP107M [GeForce GTX 1050 Mobile], with kernel module nouveau.

This sounds like it might be a dual-GPU laptop. Am I correct? If yes,
what model of laptop?

How is the "first" screen with correct display
connected? (HDMI? DisplayPort? VGA? Built-in screen of a laptop?)

How is the "second" screen with incorrect display connected?

Do you know which GPU the two screens are physically connected to?
For a desktop, it should be obvious from looking at which part they are
plugged into; for a laptop, it's non-obvious, but we might be able to find
out if you told us what laptop it is.

> (2) I think both physical screens are detected, since xrandr says:
> 
> Screen 0: minimum 16 x 16, current 3840 x 1080, maximum 32767 x 32767
> XWAYLAND0 connected primary 1920x1080+0+0 (normal left inverted right x
> axis y axis) 340mm x 190mm
>    1920x1080     60.05*+
> XWAYLAND1 connected 1920x1080+1920+0 (normal left inverted right x axis
> y axis) 530mm x 300mm
>    1920x1080    143.88*+

This is telling you about the emulated screens corresponding to your
real screens, as presented by Xwayland based on information provided by
GNOME Shell in native Wayland mode. For the real (lower-level) story,
it might be helpful to look at:

head /sys/class/drm/card*-*/status
head /sys/class/drm/card*-*/modes

I wonder whether the very high refresh rate (144 Hz) on the second screen
is relevant to this: that's relatively unusual. If you configure it for
a lower refresh rate like 60 Hz in gnome-control-center, does that work
any better?

    smcv