Wrong Qt backend used in desktop session (xcb vs. Mir)

[Rocko]

I installed unity8-desktop-session-mir in my vmplayer vivid guest and tried logging into it, got only a black screen, and found a unity8 crash file in the /var/crash afterwards.

I also almost always (9 out of 10 times) get a black screen if I try to log into a ubuntu-desktop-mir session, and if I do manage to get a normal screen with ubuntu-desktop-mir, resizing it gives me the black screen. So this might be related to a bug in mir.

ProblemType: Crash
DistroRelease: Ubuntu 15.04
Package: unity8 8.02+15.04.20141216.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.16.0-28.38-generic 3.16.7-ckt1
Uname: Linux 3.16.0-28-generic x86_64
ApportVersion: 2.15.1-0ubuntu1
Architecture: amd64
Date: Mon Jan 5 11:03:29 2015
ExecutablePath: /usr/bin/unity8
ExecutableTimestamp: 1418728702
InstallationDate: Installed on 2015-01-03 (1 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20141220)
ProcCmdline: unity8
ProcCwd: /home/rocko
ProcEnviron:
 LANGUAGE=en_US
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Signal: 6
SourcePackage: unity8
StacktraceTop:
 QMessageLogger::fatal(char const*, ...) const () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
 ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
 ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
 ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
 QPlatformIntegrationFactory::create(QString const&, QStringList const&, int&, char**, QString const&) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
Title: unity8 crashed with SIGABRT in QMessageLogger::fatal()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
upstart.unity8.log:
 ()
 QXcbConnection: Could not connect to display

[Apport retracing service (apport)]

StacktraceTop:
 qt_message_fatal (context=..., message=...) at global/qlogging.cpp:1364
 QMessageLogger::fatal (this=this@entry=0x7fff016396e0, msg=msg@entry=0x7f1868274578 "QXcbConnection: Could not connect to display %s") at global/qlogging.cpp:669
 QXcbConnection::QXcbConnection (this=0x1630e90, nativeInterface=0x16290b0, canGrabServer=<optimized out>, displayName=0x0) at qxcbconnection.cpp:322
 QXcbIntegration::QXcbIntegration (this=0x1626880, parameters=..., argc=@0x7fff01639b4c: 1, argv=0xffffffffffffffff) at qxcbintegration.cpp:162
 QXcbIntegrationPlugin::create (this=<optimized out>, system=..., parameters=..., argc=@0x7fff01639b4c: 1, argv=0x7fff01639fd8) at qxcbmain.cpp:58

[Michał Sawicz (saviq)]

Something's wrong with the setup there, as it's trying to use the xcb backend instead of Mir.

[Rocko (rockorequin)]

Is there anything I can try? All I did was install it and try it, so it ran with the default settings.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

I'm assuming we fixed this in bug 1526658