I run Ubuntu Desktop in a VirtualBox seamless mode, hosted on Windows 7. I recently upgraded from 11.10 to 12.04 and seamless mode no longer works correctly. I have re-installed guest extensions.
The problem is that the Ubuntu desktop wallpaper is shown, effectively blocking the Windows desktop. I can bring Windows apps to the foreground, but as soon as I bring any Ubuntu window to the foreground, all the windows apps will disappear, hidden by the ubuntu desktop even if I activated an Ubuntu window in a different monitor. So, it is not very much different from full-screen mode at this time.
I suspect if I could turn off the Ubuntu desktop or wallpaper this would be a sufficient workaround (this is basically what Seamless mode is) but that does not seem to be possible within Ubuntu itself.
[Jeremy doesn't specify system config, but I can confirm I'm seeing this behavior in Win 7 64-bit with both 32-bit and 64-bit guests. Giovanni sees the same thing on his laptop running Vista Ultimate 64 bit after upgrading his 32-bit guest to 12.04 (forums.virtualbox.org p225407, requires logging in with your free Oracle account). I was using vbox 4.1.14r77440 and matching Guest Additions. I upgraded to 4.1.16-78094 vbox+additions. Still a problem. And I filed launchpad bug 999929 to see if I can get feedback from developers. – tbc0]
Any other ideas?
Best Answer
This appears to be a window manager issue. As a VirtualBox guest under Windows 7 Premium 64-bit, Ubuntu 12.04 64-bit has the problem mentioned: the Ubuntu background image remains displayed. Using Ubuntu 12.04 64-bit with the GNOME window manager (installed via Ubuntu Software Center), however, seamless mode works correctly. Using Xubuntu 12.04 64-bit (which uses the XFCE window manager instead of Unity), the seamless mode also works correctly. Thus only Unity experiences this problem.
Until the Unity team solves the issue, use the Ubuntu Software Center and type in 'gnome' and use it to install the GNOME Desktop Environment. At log-in time, click on the Ubuntu icon and select one of the GNOME choices [GNOME, GNOME Classic, or GNOME Classic (no effects)] for your session. Seamless mode works as intended.
Alternatively, use the Xubuntu distribution. Seamless mode also works as intended.