Lock screen shows a dimmed desktop

[James Gauth]

Whenever my screen locks (with the lock screen icon, ctrl-alt-l or after a period of time), the screen fades to black but then shows a dimmed version of the desktop.

If I wait until the dimmed screen is shown and move the mouse to pop up the unlock dialogue, then cancel the dialogue, the correct blanked background is shown.

The bug seems related to the following:
https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/160264
(near the end of the bug report people are seeing the same effect but the bug report does not address this issue)

Prior to a month or two ago, locking the screen used to blank it properly. I find myself locking my screen and walking away from my computer only to return with my desktop still visible (although slightly dimmed).

I've tried changing my Compiz configuration to see if it affects anything. When I disable animations and window fading in ccsm, initial blanking doesn't work at all (ie. locking the screen makes it fade, then shows my entire desktop as-is, no dimming at all).

If I go to the Screensaver preferences, select 'Blank screen' as my screensaver and then click Preview, the first-time preview is completely transparent. If I cancel the preview and then click Preview again, it shows a black (blank) preview.

[AndrewR (lotsofish)]

I have the same problem on Hardy (all released updates), nvidia restricted drivers + compiz. Lock screen, shows desktop, if I move mouse or hit a key it shows the log in window, then hit escape to go black but it does not allow the monitor to turn off.

I have not tried disabling Compiz or installing the hardy proposed fix from the other bug report posted yet.

[Xepra (xepra)]

I can also confirm this happens intermittently on Hardy, all released updates, with nvidia restricted drivers compiz and two instances of X in a dual monitor setup. I believe it only happens on one of the screens when it does happen. I usually manually lock the computer, so it could happen every time that it locks automatically. I will pay more attention.

[tjb (trevorbriere)]

The same thing is happening on my hardy-compiz laptop. If anyone knows of a workaround, please post it. It leaves a false sense of security - myself and probably a lot of others do not want to leak confidential information. That's the whole point of "locking" it before leaving it unattended.

Thank you.

[164747 (jacquet-david)]

I can confirm this bug on two Hardy machines, booth running compiz with nvidia binary driver. However, it does not happen every time. When it happens, I only have to move the mouse pointer, and then the screen goes into a correct black lockdown.

[Steve Walker (swalker2001)]

This bug is present in Pangolin as well. It is intermittent and I have not been able to figure out how to reproduce it but I believe it only happens when the screen locks after timeout rather than when I lock the screen with CTRL-ALT-L.

I have also noticed that if i have a virtualbox running, and focus is on the virtualbox when the screen locks, I can usually work in the virtualbox without entering my password to unlock the screen. However, as soon as I try to shift focus to Ubuntu the screen blanks to the desktop background and I am required to enter a password to continue.

I noticed this in 11.10 as well.