I have three command applets on a panel. They are displaying correctly but the journal is showing this assertion fail every time an applet refreshes.

This happens on only one of my 19.04 machines. I have 3

 command-applet[31803]: gtk_label_set_text: assertion 'GTK_IS_LABEL (label)' failed

Even though they display correctly, the panel often becomes unresponsive so that application links stop working.

Something is wrong, but I don't know where to look next.


The command applet is essentially a dynamic panel label. It sits on a desktop panel and displays the output of an associated script. For example I display the IP, the external IP, VPN status. Simple scripts. When the script logic fails the command applet will display whatever error message the script has generated.

The applet is very simple. I doubt there is any involvement of 3D but that is a guess. If I discover otherwise, I'll post.

The applet is MATE standard issue,the github repo is here :



Desktop compositor : Marco (Adaptive)

Log file : syslog

To reproduce:

  • rclick panel, choose 'Add to Panel'
  • In the 'Add to Panel' dialog, choose 'Command / Shows the output of a command'
    • Panel will add a label showing the current time. This is the default command.)
  • rclick the new label, choose 'Preferences'
  • In the 'Command' field, enter the full path to the script
  • In the 'Interval' field, set the number of seconds to put between refreshes
  • Close the dialog

Here is a script that puts the current workspace name:


echo $(wmctrl -d | awk '/\*/ {print $10}')

Here are the relevant dconf entries as given by dconf dump / :



And after N0rbert's comment on another panel-related issue from some time ago -- Question recently upvoted by some remarkable coincidence :

apt-cache policy mate-panel python-mate-menu libmate-menu2    

  Installed: 1.20.5-1
  Candidate: 1.20.5-1
  Version table:
 *** 1.20.5-1 500
        500 http://ca.archive.ubuntu.com/ubuntu disco/universe amd64 Packages
        100 /var/lib/dpkg/status
  Installed: 1.20.2-1
  Candidate: 1.20.2-1
  Version table:
 *** 1.20.2-1 500
        500 http://ca.archive.ubuntu.com/ubuntu disco/universe amd64 Packages
        100 /var/lib/dpkg/status
  Installed: 1.20.2-1
  Candidate: 1.20.2-1
  Version table:
 *** 1.20.2-1 500
        500 http://ca.archive.ubuntu.com/ubuntu disco/universe amd64 Packages
        100 /var/lib/dpkg/status
  • • Could you explain what a command applet is, where you got it from, and possibly provide the code (or a link to the code)? • When I hover over the "panel-applets" tag you used, it mentions 3D effects using compiz. Is that what your panel applets are about? • I searched for gtk_label_set_text and maybe stackoverflow.com/a/28957290 is of help? – DK Bose May 2 at 2:11
  • @DKBose I've added more info. The code is here github.com/mate-desktop/mate-applets – Stephen Boston May 2 at 6:10
  • @StephenBoston could you please make your problem more reproducible - add complete steps to reproduce including the simplest working script. What is your desktop compositor and in which log-file do you have these warning/error messages? I do not see issues with simple default date +%T command. – N0rbert May 2 at 10:11
  • @N0rbert Done. I added also a note explaining that this is happening on only one of my 19.04 machines. – Stephen Boston May 2 at 13:04
  • 1
    @DKBose I added more of the info you suggested. – Stephen Boston May 2 at 13:13

The issue has been resolved in this way :

System/Preferences/Hardware/Additional Drivers offers three choices: 2 NVIDIA drivers and the Nouveau. The most recent NVIDIA was selected so I selected the Nouveau and rebooted.

The display was badly distorted through the previous settings so I reset to the most recent NVIDIA and rebooted again, thinking I'd look for another solution.

Now there are no LABEL assertion failures in the log.

Note that of my three 19.04 MATE machines this is the only one with NVIDIA graphics.

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