Taskbar plugin window titles stop updating when there's no desktop switcher in the panel

[Jesús Jiménez]

I've found that taskbar plugin doesn't update window titles unless there's a desktop switcher added in some of the panels. For example, all browser windows are shown as "Mozilla Firefox" (instead of each web title), and all PcManFm are shown as just "PcManFm" (instead of current directory name). Also, behaviour of the setting "Show only windows in current monitor" (sorry if this is not the right spelling, I use Lubuntu in a non-english language) is erratic at best.

Adding a desktop switcher to any panel solves the problem. It seems to me that lxpanel assumes that desktop switcher is the only plugin who needs window info updates, so, when no desktop switcher is shown, it stops sending it to the plugins. Problem is that taskbar plugin needs this info too, and it stops working right.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: lxpanel 0.7.2-1ubuntu2
ProcVersionSignature: Ubuntu 3.19.0-26.28-generic 3.19.8-ckt4
Uname: Linux 3.19.0-26-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.17.2-0ubuntu1.3
Architecture: amd64
Config_Home_Lubuntu:
 [Command]
 Logout=lxsession-default quit
CurrentDesktop: LXDE
Date: Tue Sep 8 13:12:29 2015
InstallationDate: Installed on 2015-09-03 (4 days ago)
InstallationMedia: Lubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
SourcePackage: lxpanel
UpgradeStatus: No upgrade log present (probably fresh install)

[Lyn Perrine (walterorlin)]

I cannot reproduce this myself but does this happen if you don't use the nvidia binary drivers. Although can't use novueau with 900 hundreds series. I could not reproduce this on my intel graphics desktop or in a virtual machine. Although not sure if your processor has onboard graphics or if it works with noveau. Also you meantion settings for multiple monitors does the same thing happen when you only have one monitor active?

[Jesús Jiménez (jesjimenez)]

I 've switched to nouveau, and the bug persists: as soon as I remove desktop switcher from all panels and run "lxpanelctl restart" (or reboot), window titles stop updating in taskbar (I attach a screenshot). If I add it again to any panel, everything works fine.

I'll try to disable one monitor to see if it might be related.

[Jesús Jiménez (jesjimenez)]

I've unplugged one of my monitors, rebooted, and problem still persists...

I will try a clean Lubuntu install in a virtual machine, to see if I can reproduce the problem and give you exacts steps.

[Jesús Jiménez (jesjimenez)]

I'm not able to replicate the bug in a virtual machine. I've reinstalled Lubuntu from scratch in virtualbox, and I've tried to perform the same steps I did in my desktop with no success, everything works fine. Perhaps I've missed something, or the problem comes from some weird interaction with graphic drivers, or something related to multi-monitor that is not possible to replicate in a virtual machine.

Is there some lxpanel related log file to look at? I've seen that lxpanel can be invoked with a --log parameter, with 5 different verbose levels, but I haven't been able to find where these logs are being written...

[Launchpad Janitor (janitor)]

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

[LStranger (andrej-rep)]

The --log argument is deprecated and not used since version 0.7.0.
To see any debug you may use G_MESSAGES_DEBUG environment variable, the debug messages will come to stdout then but there isn't much to be seen anyway.
Though I hope the issue is fixed with newer versions of lxpanel, there were many updates since then.

[Chris Guiver (guiverc)]

Thank you for reporting this bug to Ubuntu.

Ubuntu 15.04 (vivid) reached end-of-life on February 4, 2016.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in.

[Launchpad Janitor (janitor)]

[Expired for lxpanel (Ubuntu) because there has been no activity for 60 days.]