Comment 5 for bug 1606866

Cheers for the reference, however, I think that's a different bug because it relates to suspend/screen-saver not kicking in, although the comment section has become a dumping ground for related issues and there is the odd mention of suspend problems.

This bug does not relate to the screen-saver or lock failing to kick in when idle. It relates to the situation where the computer does suspend properly (evidenced by a flashing power button on my hardware), usually from lid-close but also from idling, but wakes from the suspend without the lock screen.

The serious nature of this bug is that, with the computer suspended, there is no what to see that the lock screen has not kicked in. If the computer failed to suspend or as with the other bug the screen-lock didn't kick in, it would be apparent to the user and less of an issue.

I've done a little investigation and found: If the viewer has keyboard capture the problem occurs every time, but you need to suspend with a lid-close or something the viewer doesn't capture. Otherwise, the problem can occur when the view just has focus (or last focus if Suspend is chosen from the power menu), but this is less reliable it may need to be under the mouse pointer at the time of suspend or having the window maximised. In this case I was using a laptop and running the "mini.iso" Ubuntu installer in the VM, just booted to the menu.