I have found a very peculiar behavior in my laptop with Debian Bullseye and KDE Plasma 5.22.5 in Xorg. When Firefox is active and I close the lid, the screen is not locked. I thought first that this is a Firefox behaviour, but maybe not. if I close the lid **carefully** and slow, the screen locks, but if I close it fast (as usual), it does not lock. In all cases, the laptop goes to sleep, but does not always lock.

I have "When laptop lid closed: sleep" and "lock screen automatically after waking from sleep" on in my KDE settings.

What could be the reason of this? I cannot explain it. It happens only with Firefox. I would not like to move to another browser, but this is a major security risk.

I have now an explanation. When closing the lid quickly, the laptop creates a touchscreen event from the pressure of closing. That event prevents locking for some reason that I do not understand. I disabled the touchscreen and now the screen locks in all cases, both quick and careful closing of the lid.

This sounds to me like a hardware issue, maybe check in your manufacturers support pages for answers.

Mamarok wrote:This sounds to me like a hardware issue, maybe check in your manufacturers support pages for answers.

I do not think so. It sounds more like a timing issue. The touch screen event disturbs the lid close event and somehow prevents locking. I do not know Xorg architecture well, but the problem may be in Xorg also.