Bug#870641: light-locker: screen stays black after closing and opening laptop lid

[David Farrier <farrier@iglou.com>]

I see I am coming to this thread a bit late, but for what it is worth, 
here is some additional information.

But first, thanks to Udo Richter for suggesting the workaround of 
installing linux-image-5.4.0-0.bpo.2-amd64, in other words backporting the 
testing/bullseye kernel into buster. On my laptop, this fixed the 
intermittent problem restoring blanked screen. It also seems to have 
introduced a new problem where the computer occasionally does not blank 
or lock when it should, but that is far better than occasionally losing 
work-in-progress due to inability to restore the screen.

However, this does not seem to simply be a case of buster's default 4.19.0 
kernel being buggy. I say this, because I tried the backport version of 
4.19.0 in stretch. On my laptop, screen blanking and locking work just 
fine in stretch, regardless whether it is the default 4.9.0 or the 
backported 4.19.0 kernel. Apparently, something besides the kernel 
changed between stretch and buster.

Some background info: I have been testing with the xfce desktop on a 
Panasonic CF-19 laptop. Intel Corporation Xeon E3-1200 v3/4th Gen Core 
Processor Integrated Graphics Controller (rev 06)