Application windows disappear when switching to Seamless Mode

[4til7]

When I switch to seamless mode, all application windows disappear. Problem experienced under 6.02. Upgraded to 6.12. The problem still exists.

This may be an ongoing issue. A search of bug track found reports of seamless mode not working (or not working well, e.g. https://www.virtualbox.org/ticket/15318). The ones reviewed were not specific about the issues experienced.

Ubuntu 18.04

[4til7]

This tickets appears related: https://www.virtualbox.org/ticket/18421

These tickets cover a possibly related issue: https://www.virtualbox.org/ticket/18022 https://www.virtualbox.org/ticket/15092

The last one has been open four years and has a looooot of comments but (at a skim) no significant action.

[4til7]

I managed to solve this.

For Ubuntu hosts, there are multiple ways to install VirtualBox: VirtualBox's official version or Ubuntu's official repository. Mixing these can cause multiple problems. The ones I've encountered or that I've seen reported:

1) Seamless mode not working

2) Video randomly resizing

3) Attempts to install/update Guest Additions fails (e.g. with "phantom device" errors

To prevent, install _both_ VirtualBox _and_ VirtualBox Extension Pack from one source and stick with that one source:

1) Official VirtualBox versions: This has the advantage you'll always have the latest version. Find both VirtualBox _and_ VirtualBox Extension Pack under Downloads on virtualbox.org.

2) Ubuntu's official repository. Your version will generally be older but will be part of Ubuntu's official testing, bug-fixes, etc. Install it via apt: sudo apt-get install -y virtualbox-5.2 virtualbox-guest-dkms virtualbox-guest-soure \

virtualbox-guest-utils virtualbox-dkms virtualbox-qt

sudo apt-get install -y virtualbox-ext-pack

[4til7]

THIS TICKET CAN BE CLOSED: see above entry in change history.