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

[Julien Puydt]

Package: gnome-shell
Version: 41.0-2

I hadn't hooked my second monitor in a while, and now it's as described
in the title: the mouse cursor is correctly displayed on it but all the
rest is white with some garbage on the upper (about one mouse cursor
high).

That's why I think the problem comes from the top of the stack (gnome-
shell) rather than from below (nouveau), but I might be in error, so
here are details:

(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.

(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*+


Where should I have a look to find error messages and fix the issue?

Cheers,

J.Puydt