[X2Go-Dev] Bug#896: Session Resume Fails with "Failed to restore all the required visuals."

[Michael DePaulo]

Package: x2goclient
Version: 4.0.4.0
Severity: normal
Tags: +build-win32

Sometimes when starting an X2Go session on a Windows client, and
resuming it on a different machine (which may or may not be Windows),
the session fails to resume and you get this error message:

X2Go - 50
Failed to restore all the required visuals.
Can't resume the NX session on this display.

Screenshot: http://imgur.com/zQz69Cz

On test configuration #1 at least, I am still able to resume the
session on the original client, even after receiving the error on the
new client.

I have seen this issue occasionally over the last year or 2. I recall
experiencing it when try resume a session over RDP. However, I have 2
other test configurations listed below.

Note that the error message comes from nx-libs, not x2goclient.
x2goclient passes the error message to the user.

However, I am filing this bug under x2goclient since it is likely
possible to fix it by launching VcXsrv on Windows with different
options. In fact, at X2Go Gathering 2015, one of the QVD developers
said that they experienced this issue with QVD client for iOS, and
fixed it by launching their client-side X server with certain options:
https://github.com/theqvd/qvd-client-ios/blob/master/QVDWrapper/wrapper/Services/QVDXvncService.m#L106

Right now I am able to reproduce it with this test configuration (#1):

Server OS: Fedora 21 64-bit with latest updates
x2goserver: 4.0.1.19-3.fc21 (from Fedora)
x2goserver-xsession: 4.0.1.19-3.fc21 (from Fedora)
nxagent: 3.5.0.31-0.0x2go1.1.git20150608.671.main.fc21

session-starting client OS: Windows 10 64-bit build 10130
session-starting x2goclient: 4.0.4.0-2015.06.24
session-starting hardware: physical, accessed locally

session-resuming client OS: Windows XP 32-bit SP3 with last available updates
session-resuming x2goclient: 4.0.4.0-2015.06.24
session-resuming hardware: Virtual. Running on the server's qemu-kvm
hypervisor with virt-manager. QXL & SPICE are used (the SPICE server
is built into the hypervisor.) Driver is "Red Hat QXL GPU" 7/17/2013
5.1.0.10018. Color is set to 32-bit. Accessed over virt-viewer 2.0
from Windows.

Also, at the X2Go Gathering 2015, we were able to reproduce this with
the following 2 clients (but with a different server) (test config
#2):

Server Details: unknown

session-starting client OS: Windows 7 64-bit SP1 with latest updated
session-starting x2goclient: 4.0.4.0-2015.06.24
session-starting hardware: physical, accessed locally

session-resuming client OS: X2Go TCE (version unknown) (based on
Debian 7 Wheezy IIRC)
session-resuming x2goclient: version unknown
session-resuming hardware: physical, accessed locally